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Nevado del Ruiz

Photo of this volcano
  • Country
  • Volcanic Region
  • Landform | Volc Type
  • Last Known Eruption
  • 4.892°N
  • 75.324°W

  • 5,279 m
    17,320 ft

  • 351020
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Weekly Report: 20 November-26 November 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 19-25 November. The number of seismic events associated with fluid movement decreased in number but increased in magnitude compared to the previous week. Additionally, the number of low-level, long-duration events increased. Webcam images confirmed several ash emissions and higher-temperature ejecta associated with some of these events, though weather clouds sometimes obscured views. Seismicity associated with rock fracturing remained similar in number but decreased in magnitude compared to the previous week. The earthquakes were less than M 1, located below Arenas Crater and the SSW, NE, and SE flanks within 10 km, and had depths of 1-7 km. Low-energy thermal anomalies on the crater floor were identified in satellite data when weather permitted. Gas plumes rose up to 1.3 km above the crater rim and drifted SW on 21 and 24 November. Sulfur dioxide emissions detected in satellite data were similar to previous weeks. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater, not to spend long periods of time on the Murillo-Cerro Gualí Road, and to avoid drainages in the high-threat zones.

Source: Servicio Geológico Colombiano (SGC)


Most Recent Bulletin Report: August 2023 (BGVN 48:08) Citation IconCite this Report

Intermittent gas-and-ash plumes, ashfall events, and seismicity during February-July 2023

Nevado del Ruiz is located in central Colombia and covers more than 200 km2. It contains the 1-km-wide, 240-m-deep Arenas summit crater. Eruptions have been documented since 1570 CE. The current eruption period has been ongoing since November 2014 and more recently has consisted of intermittent ash emissions, lava dome growth, and thermal activity (BGVN 48:02). This report describes intermittent ash plumes, ashfall events, gas-and-steam emissions, and seismicity during February through July 2023, based on information from the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and various satellite data.

Occasional thermal anomalies were recorded during February through July 2023, with slightly stronger and more frequent anomalies occurring during mid-March through early May, according to MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data (figure 143). A total of seven thermal alerts were detected by the MODVOLC thermal alert system on 22 March, 7, 10, and 19 April, and 8 May. Some of that stronger thermal activity was captured in infrared satellite images on 7 February, 18 April, 23 April, and 8 May; weather clouds often obscured clear views of the summit (figure 144). According to data from the TROPOMI instrument on the Sentinel-5P satellite, sulfur dioxide plumes were frequently detected throughout the reporting period, many of which had maximum column densities that exceeded 2 Dobson Units (DU) and drifted in different directions (figure 145).

Figure (see Caption) Figure 143. Occasional thermal anomalies were detected at Nevado del Ruiz during February through July 2023, according to this MIROVA graph (Log Radiative Power). Slightly stronger and more frequent anomalies were detected during mid-March through early May. Only two anomalies were detected during mid-June and three during July. Courtesy of MIROVA.
Figure (see Caption) Figure 144. Infrared (bands B12, B11, B4) satellite images showing a strong thermal anomaly at the summit crater of Nevado del Ruiz on 18 April 2023 (left) and 8 May 2023 (right). Courtesy of Copernicus Browser.
Figure (see Caption) Figure 145. Sulfur dioxide emissions from Nevado del Ruiz were frequently captured with the TROPOMI instrument on the Sentinel-5P satellite during February through July 2023. Plumes drifted in different directions and often exceeded 2 Dobson Units (DU), as shown on 23 February 2023 (top left), 3 March 2023 (top middle), 15 April 2023 (top right), 13 May 2023 (bottom left), 19 June 2023 (bottom middle), and 28 July 2023 (bottom right). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during February and most of March was relatively low and consisted of gas-and-steam and ash emissions and low seismicity. Gas-and-steam plumes mainly composed of sulfur dioxide were reported once a week, rising 1.3-3.2 km above the summit and drifting in different directions during February, the latter of which was recorded on 8 February. During March gas-and-ash plumes rose 2-3 km above the summit and drifted NW and SW, the latter of which occurred on 11 March. On 4 March seismic signals increased in intensity and were associated with mostly continuous ash emissions with occasional pulses. Ashfall was reported in Manizales (27 km NW). Webcam images and reports from residents captured several ash emissions during 18-20 March. The emissions were associated with seismic signals indicating fluid movement in the conduit. A gas-and-ash emission rose 2.7 km above the summit and drifted SW at 0902 on 20 March and was visible from several municipalities including: Caldas, Tolima, and Risaralda. This plume was one of the tallest recorded in recent days. Two notable seismic increases were recorded on 24 and 31 March, mainly characterized by rock-fracturing earthquakes; seismicity mainly affected the SW flank. On 28 March there were 6,500 rock-fracturing events detected, the highest daily count since 2010. The number of daily events continued to increase and on 29 March the seismic network recorded 11,000 earthquakes, the highest daily count since seismic monitoring began in 1985. On 30 March, 11,600 earthquakes were detected. The Alert Level was raised to Orange, Level II (the second highest level on a four-level scale) on 30 March. In addition to the seismic swarm, seismic signals indicating fluid movement continued, some of which were associated with ash emissions. On 30 March ash emissions rose as high as 1.8 km above the summit and drifted NW and SW, and the next day, gas-and-ash emissions reached 1.3 km above the summit and drifted SW and SE. The total number of earthquakes on 31 March was 8,800.

During the first half of April, seismicity showed a gradual decrease in the number of recorded events, ranging from 5,000-10,000 events during 1-5 April to 500-3,000 during 6-13 April. For the rest of the month, about 100 events occurred each day. Gas-and-ash emissions rose 1.2 km above the summit and drifted SW and NW during 1-2 April; officials from the Los Navados National Natural Park reported ashfall in Brisas and Potosí. During 3-4 April gas-and-ash plumes rose 1.1-1.5 km above the summit and drifted SW and NW. On 5 April at 0216 a strong earthquake of M 3.9 was recorded and felt by residents in Villamaría (28 km NW). SGC noted that this was the highest magnitude earthquake recorded in the SW part of the volcano since instrumental monitoring was installed in 1985. According to a news article, 87 people had self-evacuated after the government called for a voluntary evacuation of roughly 2,500 families. Continuous gas-and-ash emissions rose 1.2-1.8 km above the summit and drifted SW, SE, NE, and E during 6-10 April, based on webcam images and reports from residents in La Cabaña (Murillo, Tolima) (figure 146). Drumbeat-type seismicity associated with the growth of the lava dome located at the bottom of the Arenas crater was detected on 8, 13, 14, 17, 18, and 21 April. During 11-13 April gas-and-ash plumes rose 1.8-2.5 km above the summit and drifted N, NE, SW, and NW, and there were reports of ashfall in Villamaría (Caldas) and Filandia (Quindío). As many as 2,000 daily drumbeat-type events were also recorded on 13 April. During 0759-1113 on 14 April and from 1515 on 14 April to 0057 on 15 April seismicity intensified and corresponded to continuous ash emissions that rose as high as 1.5 km above the summit and drifted SW, as observed by residents in Murillo and Manizales. During 16-19 and 21-22 April gas-and-steam plumes possibly containing some ash rose 1.1-1.8 km above the summit and drifted in different directions; ashfall was reported in Anzoátegui, Tolima on 18 April after an ash plume was reported at 0711. Pulsating ash emissions were visible in webcam images during 23-29 April, rising 1.1-2.5 km above the summit and drifting in multiple directions. The ash emissions on 25 April were visible from Tolima, Caldas, and Risaralda. The ash emission reported at 0837 on 27 April was followed by reports of ashfall in Manizales a few hours later.

Figure (see Caption) Figure 146. Photo of an ash cloud from Nevado del Ruiz as seen from Murillo, Tolima, Colombia taken on 7 April 2023. Courtesy of Joaquin Sarmiento via CNN.

According to SGC, the sulfur dioxide emission rate increased during the first week of May compared to those emitted during April. Drumbeat-type events continued to occur on 6, 16, 17, 26, 27, and 31 May. Gas-and-steam plumes rose 1.9 km and 2.7 km above the summit on 12 and 25 May, respectively, and drifted generally W. A sulfur odor was reported in several parts of Manizales on 15 May. A significant thermal anomaly was observed within the crater on 31 May. On that same day, a sulfur odor was reported in Cerro Gualí.

SGC reported that the rate of sulfur dioxide emissions had decreased in June compared to May. Several short-duration drumbeat-type events were recorded on 1, 5, and 26 June. Gas-and-steam emissions that possibly contained some ash rose 2-2.4 km above the summit and drifted NW on 4 June. As a result, minor ashfall was reported in Manizales and Villamaría. Continuous ash emissions was visible in webcam images during the afternoon of 20 June and ashfall was reported in Manizales. Ash emissions rose as high as 1.3 km above the summit on 21 June and drifted WSW; they continued to rise as high as 4 km above the summit that same day. Crater incandescence was observed, coinciding with pulsating ash emissions during 20-23 June. Gas-and-ash plumes rose 900-1,800 m above the summit during 24-27 June and drifted NW. Minor ashfall was reported in Villamaría and Manizales on 22 and 25 June, respectively. The Alert Level was lowered to Yellow, Level III (the second level on a four-level scale) on 27 June. SGC noted that monitoring data was more stable in recent weeks, thermal anomalies at the lava dome were less intense, ash emissions had decreased, and gas-and-steam emissions remained relatively stable.

Low seismicity and gas-and-ash emissions were reported during July. Drumbeat-type events were detected on 1, 3, 7, 8, 10, 12, 15, 17, 24, 26, 27, 28, and 29 July. Incandescence was observed on 4 July, accompanied by an ash emission at 2048 that rose 2km above the summit and drifted NW and SW. Occasional gas-and-steam plumes mainly consisting of sulfur dioxide rose 1.2-1.8 km above the summit and drifted NW and WSW. During 24-25 July a gas-and-ash plume rose 1.8 km above the summit and drifted NW and WNW, causing light ashfall in Manizales. On 27 July at 0617 a gas-and-ash plume rose 2.3-3.5 km above the summit and drifted NW and WNW; light ashfall was reported in Manizales on several occasions.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www.sgc.gov.co/volcanes); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/); Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/); CNN, One CNN Center, 12th Floor, North Tower, Atlanta, GA 30303, USA, “A deadly volcano could erupt ‘within days or weeks’ in Colombia. But only a small fraction of locals have evacuated”(URL: https://edition.cnn.com/2023/04/15/americas/nevado-del-ruiz-colombia-volcano-intl-latam/index.html).

Weekly Reports - Index


2024: January | February | March | May | June | July | August | September | October | November
2023: January | March | April | May | June | August | September | October | November | December
2022: February | April | May | August | October | November | December
2021: July | August | November | December
2020: March | April | May | July | December
2019: July | October
2018: October
2017: January | February | March | April | May | August
2016: January | February | March | April | May | June | July | August | September | October | November | December
2015: January | April | May | June | July | August | September | October | November | December
2014: December
2013: January | April | July
2012: March | April | May | June | July | August | September | November
2010: July | September
2002: June


20 November-26 November 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 19-25 November. The number of seismic events associated with fluid movement decreased in number but increased in magnitude compared to the previous week. Additionally, the number of low-level, long-duration events increased. Webcam images confirmed several ash emissions and higher-temperature ejecta associated with some of these events, though weather clouds sometimes obscured views. Seismicity associated with rock fracturing remained similar in number but decreased in magnitude compared to the previous week. The earthquakes were less than M 1, located below Arenas Crater and the SSW, NE, and SE flanks within 10 km, and had depths of 1-7 km. Low-energy thermal anomalies on the crater floor were identified in satellite data when weather permitted. Gas plumes rose up to 1.3 km above the crater rim and drifted SW on 21 and 24 November. Sulfur dioxide emissions detected in satellite data were similar to previous weeks. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater, not to spend long periods of time on the Murillo-Cerro Gualí Road, and to avoid drainages in the high-threat zones.

Source: Servicio Geológico Colombiano (SGC)


30 October-5 November 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 30 October-5 November. The number of seismic events associated with fluid movement increased in both magnitude and number compared to the previous week, especially from seismic signals related to pulsating ash emissions, but were variable between low and moderate levels throughout the week. Webcam images confirmed ash emissions associated with some of these events. At 0220 on 30 November an ash emission rose 1.8 km above the crater and drifted NE, E, and NW. Ashfall and sulfur odor was reported in the Lagunilla River area to the E. Seismicity associated with rock fracturing increased in both magnitude and number compared to the previous week, with depths less than 8 km below the summit. The largest event was M 2.5, recorded at 0055 on 30 October. Low-to-moderate thermal anomalies on the crater floor were identified in satellite data when weather permitted. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater, not to spend long periods of time on the Murillo-Cerro Gualí Road, and to avoid drainages in the high-threat zones.

Source: Servicio Geológico Colombiano (SGC)


16 October-22 October 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 15-21 October. The number of seismic events associated with fluid movement increased in both magnitude and number compared to the previous week, especially from seismic signals related to pulsating ash emissions, but were variable between low and moderate levels throughout the week. Webcam images confirmed ash emissions associated with some of these events. The highest temperature recorded for the week was on 16 October, associated with an ash emission at 0452 that rose 1.3 km above the crater. Another ash emission rose 2.2 km above the crater at 1637 on 19 October. Ashfall was reported in Cabaña de Brisas (NW), Aguacerales, and Recreo (Caldas and Tolima). Seismicity associated with rock fracturing remained similar in the number of events and magnitude compared to the previous week, with depths ranging from less than 1 km down to 8 km below the summit. The largest event was an M 1 which was detected at 1725 on 20 October. Sulfur dioxide emissions were variable, and drift directions were not towards measuring stations; satellite measurements indicated a slight decrease in emissions. Low-to-moderate thermal anomalies on the crater floor were identified in satellite data. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater, not to spend long periods of time on the Murillo-Cerro Gualí Road, and to avoid drainages in the high-threat zones.

Source: Servicio Geológico Colombiano (SGC)


25 September-1 October 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 24-30 September. The number of seismic events associated with fluid movement increased in both magnitude and number compared to the previous week but were variable between low and moderate levels throughout the week. Webcam images confirmed ash emissions associated with some of these events along with occasional ejections of hotter material. Ash plumes rose as high as 2 km above the crater rim and drifted NW and WNW during the first half of the week and N, E, and SE during the second half of the week. Ashfall was reported in Cabaña de Brisas (NW) and in areas to the E around the Lagunilla River. Seismicity associated with rock fracturing increased in the number of events, though their magnitudes were comparable to the previous week; these earthquakes, with depths ranging from less than 1 km down to 8 km below the summit, were primarily located within 4 km SSW, S, SE, and SE of Arenas Crater. The largest event was an M 1 which was detected at 2131 on 28 September and located about 2 km SSE and 4 km deep. Sulfur dioxide emissions were variable, and drift directions were not towards measuring stations; satellite measurements indicated increased emissions and a high value on 29 September that had not been recorded since February 2023. Low-to-moderate thermal anomalies on the crater floor were identified in satellite data. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater, not to spend long periods of time on the Murillo-Cerro Gualí Road, and to avoid drainages in the high-threat zones.

Source: Servicio Geológico Colombiano (SGC)


14 August-20 August 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 13-19 August. The number of seismic events associated with fluid movement increased in both magnitude and number compared to the previous week but were variable throughout the week. Through webcams several ash emissions associated with these events were confirmed along with the occasional ejection of hotter material. Ashfall was reported in the municipalities of Villamaría (28 km NW) and Manizales (28 km NW), especially during 17-18 August. Seismicity associated with rock fracturing decreased in both the number of events and their magnitudes compared to the previous week; these earthquakes, with depths ranging from less than 1 km down to 8 km below the summit, were primarily located beneath the NW, ESE, and SE flanks of Arenas Crater and within 8 km N and NE of the crater. The largest event was an M 1 which was detected at 1747 on 13 August and located about 8 km ESE and 5 km deep. Sulfur dioxide emissions were variable, and gas plumes rose as high as 1.2 km above the crater rim and drifted NW, W, and WSW. Thermal anomalies on the crater floor were identified in satellite data, though weather conditions often obscured views. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater, not to spend long periods of time on the Murillo-Cerro Gualí Road, and to avoid drainages in the high-threat zones.

Source: Servicio Geológico Colombiano (SGC)


10 July-16 July 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 9-15 July. The number of seismic events associated with fluid movement decreased in both magnitude and number compared to the previous week but were variable throughout the week. Through webcams and visual observations by officials at Parque Nacional Natural de Los Nevados, several as emissions associated with these events were confirmed. Seismicity associated with rock fracturing decreased in the number of events but maintained similar magnitudes compared to the previous week; these earthquakes at depths of 1-7 km below the summit were primarily located within 4 km of Arenas Crater and the NE sector. The largest events were M 1.2 which were detected at 0319 on 13 July (about 1 km NW and 2 km deep) and 1222 on 14 July (to the N and 4 km deep). Seismic signals indicating lava-dome activity increased but remained of short duration and low energy level. Sulfur dioxide emissions were variable, and gas plumes rose as high as 1.5 km above the crater rim and drifted NW, W, and WSW. Thermal anomalies on the crater floor were identified in satellite data, though weather conditions often inhibited views. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


19 June-25 June 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 18-24 June. The number of seismic events associated with fluid movement increased in both magnitude and number compared to the previous week. There was an increase in the number of long-duration seismic signals. Some of these signals were associated with ash emissions observed by officials at Parque Nacional Natural de Los Nevados and area residents. Seismicity associated with rock fracturing was stable in both the number and magnitude of events compared to the previous week; these earthquakes at depths of 1-7 km below the summit were primarily located within 10 km of Arenas Crater, particularly to the SE and ESE. The largest event was an M 1.1 which was detected at 2358 on 18 June and was located at a depth of 2 km. Seismic signals indicating lava-dome activity notably increased; on 24 June a period of dome-related seismicity was characterized as having the longest duration and highest number of events since 2015, the year this type of seismicity was first detected. Sulfur dioxide emissions were variable and gas plumes rose as high as 1.4 km above the crater rim and drifted NW, W, and SW. Thermal anomalies on the crater floor were identified in satellite data, though weather conditions often inhibited views. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


1 May-7 May 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 30 April-6 May. The number of seismic events associated with fluid movement remained stable at low-to-moderate levels, though the signal increased in magnitude. Some of these signals were associated with pulsating emissions of ash and gas; ash plumes rose as high as 2 km above the summit on 30 April and drifted NW and WNW. Seismicity associated with rock fracturing was stable in both the number and magnitude of events; these earthquakes at depths less than 5 km below the summit were primarily located within 5 km of Arenas Crater, particularly to the E. The largest event was an M 1.2 which was detected at 1842 on 1 May. Several thermal anomalies on the crater floor were identified in satellite data, though weather conditions often inhibited views. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


20 March-26 March 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued during 19-25 March. Seismicity associated with fluid movement decreased in both the number of events recorded and seismic energy released; most of these signals were associated with pulsating emissions of ash and gas. At 0516 on 22 March a seismic signal was associated with an ash emission that rose 1,100 m above the crater and drifted 1,400 m to the SW and W; this was the highest intensity signal this year. Several ash emissions were seen with a webcam. Seismicity associated with rock fracturing decreased in the number of events but increased in seismic energy released. These earthquakes at depths of 1-6 km below the summit were primarily located on the E flank, 3-5 km from the Arenas Crater, with additional events in other areas within 10 km of the crater. The largest event of the period was M 2.0 at 1217 on 24 March. Several thermal anomalies on the crater floor were identified in satellite data. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


6 March-12 March 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued at moderate levels during 5-11 March. Seismic events indicating rock fracturing increased both in number and intensity compared to the previous week. These events were located in areas up to 13 km NW, SSW, and NE from Arenas Crater at depths of 1-10 km. The largest earthquake, a M 1.8, was recorded at 1108 on 7 March and was located 4 km SSW of the crater at a depth of 4 km. Seismicity associated with fluid movement in the conduit decreased in both number and magnitude. These events were mainly associated with ash-and-gas emissions that rose as high as 1.1 km above the summit and up to 2 km as the plume drifted downwind. Several thermal anomalies on the crater floor were identified in satellite data, though they had low-to-moderate values. The Alert Level remained at Yellow (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


14 February-20 February 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued at moderate levels during 13-19 February. Seismic events indicating rock fracturing increased in number compared to the previous week. These events were located in areas up to 7 km in various directions from Arenas Crater at depths of 1-8 km. The largest earthquake, a M 1.6, was recorded at 1518 on 18 February and was located SE of the crater at a depth of 2 km. Seismicity associated with fluid movement in the conduit decreased in both number and magnitude. These events were mainly associated with ash-and-gas emissions that rose as high as 1 km above the summit and drifted NW. Several thermal anomalies on the crater floor were identified in satellite data; the highest value recorded since 2007 (when this type of monitoring began) was recorded on 15 February. The Alert Level remained at Yellow, Level III (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


7 February-13 February 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that unstable eruptive activity at Nevado del Ruiz continued during 30 January–6 February. Seismic events indicating rock fracturing remained similar to the previous week in both number of events and seismic energy released. These events were mainly located in areas up to 5 km to the NE, SE, S, and SW of Arenas Crater, and at depths of 1-7 km. The largest event, a M 1.1, occurred at 0648 on 2 February and was located about 2 km SSE of the crater and at a depth of 4 km. Seismicity associated with gas-and-ash emissions remained at similar numbers as the previous week but were more intense, and several ash emissions were observed through cameras. On 5 February an ash plume rose to a maximum height of 1.8 km above the summit. Sulfur dioxide emissions varied but continued at a low level overall. The Alert Level remained at Yellow, Level III (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


24 January-30 January 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued at low levels during 23-29 January. Seismic events indicating rock fracturing increased in number, though the intensity of the signals was similar to the previous week. These events were mainly located in areas up to 6 km to the NE and SSE of Arenas Crater, and at depths of 1-7 km. The largest event, a M 1.3, occurred at 2105 on 24 January and was located about 1 km SSE of the crater and at a depth of 3 km. Seismicity associated with gas-and-ash emissions remained at similar numbers as the previous week but were less intense. Gas-and-ash emissions drifted NW and N and rose to a maximum height of 1.8 km above the summit, recorded on both 25 and 29 January. Sulfur dioxide emissions varied but decreased overall. The Alert Level remained at Yellow, Level III (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


3 January-9 January 2024 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued at moderate levels during 2-8 January. Seismic events indicating rock fracturing increased in both number an intensity. These events were located in areas up to 4 km in various directions from Arenas Crater at depths of 1-7 km. The seismic activity was most notable on 3 and 5 January; the largest earthquake, a M 3.9, was recorded at 1103 on 3 January and felt by officials of the Parque Nacional Natural Los Nevados, SGC personnel in the field, and residents in Manizales (27 km NW). Seismicity associated with ash-and-gas emissions decreased in both size and number. The maximum height of the ash-and-gas emissions was 1.8 km above the summit, recorded on 6 January. Emissions during the week drifted NW, W, and SW, causing ashfall near the volcano and occasionally in Manizales. The Alert Level remained at Yellow, Level III (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


20 December-26 December 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that eruptive activity at Nevado del Ruiz continued at low-to-moderate levels during 19-25 December. Seismic events indicating rock fracturing increased in both number an intensity. These events were located in areas up to 11 km in various directions from Arenas Crater, though mainly on the E flank, at depths of 1-9 km. The seismic activity was most notable during 24-25 December; earthquakes at 1402, 1403, and 1715 on 24 December and at 0813 on 25 December were felt in parts of La Cabaña and the Lagunilla River drainage in the department of Tolima. Seismicity associated with activity at the lava dome had also intensified, beginning at 2301 on 24 December. Ash-and-gas emissions were seismicity detected during the week as well as occasionally visible in webcam images. The maximum height of the ash-and-gas emissions was 1.9 km above the summit, recorded on 22 December. Emissions drifted SE during the first part of the week and SW and NW during the second part of the week, generating ashfall near the volcano and occasionally in Manizales (27 km NW). The Alert Level remained at Yellow, Level III (the second level on a four-level scale), and the public was warned to stay out of the restricted areas around Arenas Crater.

Source: Servicio Geológico Colombiano (SGC)


22 November-28 November 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued at low-to-moderate levels during 21-27 November. Seismic events indicating the movement of fluids increased in number and intensity compared to the previous week, especially with respect to the signals indicating emissions. The number of signals indicating rock fracturing decreased in both number an intensity. These events were located in areas up to 6 km in various directions from Arenas Crater, at depths of 1-8 km. The largest earthquake, a M 2, was recorded at 1949 on 25 November. Thermal anomalies on the crater floor were identified in satellite images. Ash-and-gas plumes rose as high as 1.3 km above the summit on 21 November and up to 1.7 km on 27 November. The plumes drifted WSW and SW. Sulfur dioxide emissions increased through the week. The Alert Level remained at Yellow, Level III (the second level on a four-level scale).

Source: Servicio Geológico Colombiano (SGC)


18 October-24 October 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued at low-to-moderate levels during 17-23 October. Seismic events indicating the movement of fluids increased in number and intensity compared to the previous week. The number of signals indicating rock fracturing increased in intensity, though decreased in number. These events were located in areas as far as 13 km ESE and SW of Arenas Crater, at depths less than one to 7 km. Earthquakes recorded at 2214 on 21 October (M 3) and at 0837 on 22 October (M 3.2) were felt by residents in the municipality of Murillo. Thermal anomalies on the crater floor were identified in satellite images, though they were less intense than the previous week. Several ash-and-gas emissions were visible during the week, with the highest plumes rising to 1.6 km above the crater rim on 17 October. Plumes drifted SW, NW, and NNE. The Alert Level remained at Yellow, Level III (the second level on a four-level scale).

Source: Servicio Geológico Colombiano (SGC)


27 September-3 October 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued at low-to-moderate levels during 26 September-2 October. Seismicity indicating the movement of fluids was similar to the week before. The number of signals indicating rock fracturing significantly increased during 28-29 September. These events were located in areas 1-4 km S and SSE of Arenas Crater at depths of 2-5 km. Earthquakes recorded at 0512 (M 3.5) and 0614 (M 3.8) on 28 September were felt by residents. Rock-fracturing earthquakes were at low levels on the other days. Seismicity was generally low. Several thermal anomalies in the crater were identified in satellite images. Ash-and-gas emissions continued during the week, with the highest plumes rising to 2 km above the crater rim on 30 September. Plumes drifted NW, W, and SW; ashfall was reported in Manizales (27 km NW) on 30 September. The Alert Level remained at Yellow, Level III (the second level on a four-level scale).

Source: Servicio Geológico Colombiano (SGC)


23 August-29 August 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued at low-to-moderate levels during 22-28 August. Seismicity indicating the movement of fluids increased in number and magnitude compared to the week before; these seismic signals were most notable on 26 August and were associated with pulsating, or occasionally continuous, emissions of gas and ash. Seismicity indicating rock fracturing decreased compared to the previous week. These events were generally located below Arenas Crater and in areas within 8 km to the SE, NE, and NW at depths of less than 8 km. Ash-and-gas emissions continued, with the highest plumes rising as high as 1.3 and 2.6 km above the crater rim on 26 and at 1745 on 27 August, respectively. Plumes drifted NW, WNW, and SW and caused ashfall in Manizales (27 km NW) and Dosquebradas (40 km WSW) on 23 August, and on several other occasions during 26-28 August. The Alert Level remained at Yellow, Level III (the second level on a four-level scale).

Source: Servicio Geológico Colombiano (SGC)


16 August-22 August 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued at low levels during 15-21 August. Seismicity was generally low with occasional increases to moderate levels. Steam-and-gas emissions continued. Gas, steam, and ash plumes rose as high as 1.5 km and drifted NW and WNW on 19 August. A low-energy thermal anomaly from the crater was identified in satellite images. The Alert Level remained at Yellow, Level III (the second level on a four-level scale).

Source: Servicio Geológico Colombiano (SGC)


21 June-27 June 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued during 20-27 June and was characterized by gas, steam, and ash emissions, and variable seismic activity. The number of seismic events related to fluid movement, emissions, and rock fracturing fluctuated throughout the week; seismicity was highest at the beginning of the week and notably high during 22-23 June with the most intense seismicity recorded since the current period of elevated activity began on 24 March. Earthquakes occurred at distances of 1-8 km from Arenas crater at depths of 1-6 km. A period of continuous ash emissions in the afternoon of 20 June was visible in webcam images. Ashfall was reported in Manizales. Ash emissions on 21 June rose as high as 1.3 km above the crater rim, drifted WNW, and continued to rise to as high as 4 km above the summit. Incandescence from the crater was visible coincident with pulsating ash emissions during 20-23 June. Gas, steam, and ash plumes rose as high as 1.8 km and drifted NW during 24-27 June. Minor ashfall was reported in the municipalities of Villamaría (28 km NW) and Manizales (28 km NW) on 22 and 25 June respectively. The Alert Level was lowered to Yellow, Level III (the second level on a four-level scale) on 27 June. SGC noted that monitoring data was more stable in recent weeks; earthquake magnitudes were overall lower, the locations were more random, and the patterns did not indicate magma movement. Additionally, thermal anomalies at the lava dome were less intense, ash emissions had decreased, and gas emissions remained relatively stable.

Source: Servicio Geológico Colombiano (SGC)


31 May-6 June 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued during 31 May-6 June and was characterized by periodic gas, steam, and ash emissions, and thermal anomalies at the lava dome in Arenas Crater. Seismicity fluctuated at low levels; on 31 May SGC stated that during the past several days seismicity had decreased compared to the previous weeks. Daily gas-and-steam emissions were visible in webcam images and contained ash on most days; emissions rose as high as 2 km above the crater and mainly drifted NW. Ash emissions were confirmed in satellite images on the other days according to the Washington VAAC. A significant thermal anomaly was observed within the crater on 31 May. That same day a sulfur odor was reported in Cerro Gualí. Minor ashfall was reported in the municipalities of Villamaría (28 km NW) and Manizales (28 km NW) on 4 June. The Alert Level remained at Orange, Level II (the second highest level on a four-level scale).

Source: Servicio Geológico Colombiano (SGC)


17 May-23 May 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued during 17-23 May and was characterized by periodic gas, steam, and ash emissions, thermal anomalies at the lava dome in Arenas Crater, and elevated seismicity. Seismic signals indicating rock-fracturing events were located 3-8 km around the Arenas Crater at depths of 1-6 km. The largest event, a M 2.1, was recorded at 0341 on 21 May and was located 2 km below the Arenas crater. Gas-and-ash emissions rose as high as 1.5 km above the crater and drifted multiple directions. A thermal anomaly was observed within the crater on 18 May. The Alert Level remained at Orange, Level II (the second highest level on a four-level scale).

Source: Servicio Geológico Colombiano (SGC)


19 April-25 April 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that the eruption at Nevado del Ruiz continued during 18-25 April and was characterized by gas, steam, and ash emissions, thermal anomalies at the lava dome in Arenas Crater, and elevated seismicity. Seismic signals indicating rock-fracturing events were located 1-3 km W, SW, NE, and E of Arenas Crater and below the crater, at depths of 0.4-6.2 km. The largest event, a M 1.7, was recorded at 1735 on 24 April and was located 4.1 km E of the crater, at a depth of 3.2 km. The event was felt by residents in the Lagunilla river canyon. Additionally, signals indicating fluid movement fluctuated in intensity and were associated with daily gas-and-steam emissions, sometimes containing ash, that rose as high as 1.8 km above the crater rim. At 0711 on 18 April an ash plume rose 1.8 km above the crater rim and drifted SE, causing ashfall in the municipality of Anzoátegui, Tolima. At 2235 on 19 April and at 2248 on 21 April ash plumes rose 1.8 km and drifted SSE. Gas emissions with possible ash rose as high as 1.3 km and drifted SW and E during 20-21 April. Pulsating ash emissions were seen in webcam images during 23-25 April. The Alert Level remained at Orange, Level II (the second highest level on a four-level scale).

Source: Servicio Geológico Colombiano (SGC)


12 April-18 April 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that the eruption at Nevado del Ruiz continued during 11-18 April and was characterized by gas, steam, and ash emissions, thermal anomalies at the lava dome in Arenas Crater, and elevated seismicity. Seismic signals indicating rock-fracturing events continued to be located 2-6 km SW of Arenas Crater at depths of 2-4 km, though on 12 and 16 April signals were also located in the NE sector of the volcano at depths of 0.5-5 km. The number of daily events fluctuated through the week. Additionally, signals indicating fluid movement fluctuated in intensity and were associated with daily ash emissions. On 11 April ash-and-gas plumes rose as high as 2.5 km above the crater rim and drifted SW and NW, causing ashfall in the municipalities of Villamaría (Caldas) and Filandia (Quindío). Ash-and-gas plumes that rose as high as 1.8 km drifted SW and NW on 12 April, and 1.5 km high plumes drifted SW on 13 April. During 0759-1113 on 14 April and from 1515 on 14 April to 1257 on 15 April seismicity activity intensified and corresponded to continuous ash emissions that rose as high as 1.5 km and drifted SW. These emissions were visible from the municipalities of Murillo and Manizales. Later that day gas-and-ash plumes rose to 1.6 km and drifted NW. According to a news article 87 people had self-evacuated after the government called for the voluntary evacuation of around 2,500 families on 5 April. The Alert Level remained at Orange, Level II (the second highest level on a four-level scale).

Sources: Servicio Geológico Colombiano (SGC); CNN


5 April-11 April 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that the number of daily events detected by the seismic network at Nevado del Ruiz fluctuated during 3-8 April but declined overall. Earthquakes were generally located 2-5 km SW of Arenas Crater at depths of 3-4 km. On 9 April SGC noted that daily counts of events were no longer going to be posted in their daily reports and instead the focus will be on the location of the earthquakes. Gas emissions had also decreased in density. That same day Gestión del Riesgo de Desastres (UNGRD) reported that 2,000-2,500 families had been identified as living in high-risk areas and requested that local authorities expedite a preventive evacuation; families that had evacuated were staying with family and friends and not in evacuation shelters.

During 3-11 April the earthquakes were associated with daily emissions of gas-and-steam and gas-and-ash plumes. Ash-and-gas plumes rose as high as 1.5 km above the crater rim on 3 April and drifted NW and SW. During 6-7 April several pulsating ash emissions were observed in webcam images and by residents of La Cabaña (Murillo, Tolima). The emissions rose as high as 1.5 km and drifted SE and NE. Webcam images and La Cabaña residents again saw ash emissions on 10 April, rising as high as 1.8 km and drifting E and NE. Thermal anomalies from Arenas Crater were periodically visible through the week. The Alert Level remained at Orange, Level II (the second highest level on a four-level scale).

Sources: Servicio Geológico Colombiano (SGC); Gestión del Riesgo de Desastres (UNGRD)


29 March-4 April 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that thermal anomalies, persistent in Arenas Crater at Nevado del Ruiz since October 2022, were low-to-moderate in intensity. Seismicity increased significantly on 24 March, characterized by rock-fracturing earthquakes mainly located 2-5 km SW of Arenas crater at depths of 2-4 km. On 28 March there were 6,500 of these events, the highest daily count since 2010. The number of daily events continued to increase and on 29 March the seismic network recorded 11,000 earthquakes, the highest daily count since seismic monitoring began in 1985; on 30 March there were 11,600 earthquakes. The maximum magnitudes per day were also increasing, with a M 2.6 on 24 March, a M 2.7 on 29 March, and a M 3.1 on 30 March. The earthquake locations migrated towards Arenas Crater, though the depths remained within the same range. The Alert Level was raised to Orange, Level II (the second highest level on a four-level scale) on 30 March. In addition to the swarm, seismic signals indicating fluid movement continued to be recorded and some were associated with ash emissions; the tallest plume on 30 March rose 1.8 km above the summit and drifted NW and SW.

The number of earthquakes on 31 March totaled 8,800 with a maximum magnitude of 2.6 event at 1236. The number of signals indicating fluid movement increased during 31 March-1 April and were likely associated with ash emissions. Gas-and-ash plumes rose as high as 1.3 km above the summit and drifted SW and SE. A total of 10,400 earthquakes were recorded on 1 April with the largest event, a M 3.1, recorded at 1040. On 2 April a total of 5,400 earthquakes were recorded and the largest event (M 2.3) occurred at 1122 and was located 4.3 km SW of the crater. Ash-and-gas emissions persisted and rose to 1.2 km above the summit and drifted SW and NW. Ashfall was reported in Brisas y de Potosí by Parque Nacional Natural Los Nevados officials. The Gestión del Riesgo de Desastres (UNGRD) reported that there were 57,000 people living in 22 municipalities in the departments of Tolima, Caldas, Risaralda, Valle del Cauca, Quindío, and Cundinamarca who could be impacted by Nevado del Ruiz. Preparations and coordination for a possible evacuation of residents were centered on areas in high-risk zones including the municipalities of Villamaría in the department of Caldas, Casabianca, Herveo, Murillo, and Villahermosa in Tolima, and the sector of the Gualí River in the municipality of Guaduas, Cundinamarca.

Sources: Servicio Geológico Colombiano (SGC); Gestión del Riesgo de Desastres (UNGRD)


15 March-21 March 2023 Citation IconCite this Report

Servicio Geológico Colombiano (SGC) reported that several ash emissions at Nevado del Ruiz were visible in webcam images and reported by residents during 18-20 March. The emissions were associated with seismic signals indicating fluid movement in the conduit. An ash emission at 0902 on 20 March rose 2.7 km above the summit and drifted SW. It was one of the tallest plumes recorded in recent days and was visible from the municipalities of Caldas, Tolima, and Risaralda. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


1 March-7 March 2023 Citation IconCite this Report

Servicio Geológico Colombiano (SGC) reported that seismicity at Nevado del Ruiz began increasing on 27 February characterized by events indicting fluid movement. The elevated seismicity was sustained. On 4 March the intensity of the signals intensified and were associated with mostly continuous ash emissions with occasional pulses. Ashfall was reported in Manizales (27 km NW). The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


18 January-24 January 2023 Citation IconCite this Report

Servicio Geológico Colombiano (SGC) reported that at 0710 on 23 January an ash cloud rose from Nevado del Ruiz and drifted NW, causing ashfall in the municipality of Manizales (27 km NW). The ash emission occurred simultaneously with a seismic signal that indicated moving fluids within the volcano’s conduit. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


4 January-10 January 2023 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that at 0706 on 6 January an ash cloud rose from Nevado del Ruiz and drifted NE, causing ashfall in Villahermosa (27 km NE). The ash emission occurred simultaneously with a seismic signal indicated moving fluids within the volcano’s conduit. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


14 December-20 December 2022 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that seismicity at Nevado del Ruiz began to increase at around 1550 on 13 December. The signals indicated moving fluids within the volcano’s conduit, and some were associated with pulsating gas-and-ash emissions seen from several surrounding municipalities. Ashfall was reported on 14 December in several municipalities including Dosquebradas (40 km WSW), Santa Rosa de Cabal (34 km W), and Pereira (40 km WSW in Risaralda), Manizales (27 km NW) and Villamaría (26 km NW in Caldas), and in the Los Nevados National Natural Park sector. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


30 November-6 December 2022 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that increased seismicity at Nevado del Ruiz began to be recorded at around 1016 on 2 December and increased further on 3 December. The signals indicated moving fluids within the volcano’s conduit and were associated with gas-and-ash emissions seen from several municipalities in Tolima and Caldas. The gas-and-ash plumes generally rose less than 900 m above the summit and drifted SW but occasionally rose as high as 2.9 km. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


9 November-15 November 2022 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that during 8-14 November seismicity associated with rock fracturing at Nevado del Ruiz increased in number and energy compared to the previous week. Some of the signals were associated with gas-and-ash emissions. The hypocenters were located 0.6-7 km deep. The largest event was an M 3.1 that was recorded at 0225 on 10 November at a depth of 3.6 km below the crater and 2.7 km SW of the crater. The Washington VAAC reported ash plumes that rose to 6.4-7.3 km altitude (21,000-24,000 ft) and drifted S and SE on 11 November, based on satellite and webcam images. During 13-14 November ash plumes rose to 6.7 km altitude (22,000 ft) and drifted NE based on satellite and webcam images. Several low-to-moderate thermal anomalies in Arenas Crater were identified in satellite images. Gas-and-steam plumes (mainly sulfur dioxide) continued to be emitted, rising as high as 1.8 km above the summit on 8 November and drifting NW, SW, SE, and NE. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC)


26 October-1 November 2022 Citation IconCite this Report

On 1 November Servicio Geológico Colombiano’s (SGC) reported that during the previous week seismicity at Nevado del Ruiz was variable and indicated continuing growth of the lava dome in Arenas Crater. The number and size of seismic signals indicating fluid movement had decreased compared to the week before. Some of the signals were associated with gas-and-ash emissions. Although seismic signals indicating rock fracturing decreased in number, magnitudes were higher previous week. The hypocenters were located 0.2-7 km deep, mainly beneath the NE and SW parts of Arenas Crater, and beneath the E, SE, and NW flanks. The largest event was a local M 1.8 that was recorded at 0518 on 28 October at a depth of 1.8 km below the crater. Several low-to-moderate thermal anomalies in Arenas Crater were identified in satellite images and minor changes to the dome and crater floor were visible. Plumes of steam and gas (mainly sulfur dioxide) continued to be emitted, rising as high as 1.8 km above the summit on 31 October and drifting SE, ESE, and ENE. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


17 August-23 August 2022 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that at 1751 on 18 August an ash emission at Nevado del Ruiz rose 3.2 km and drifted WNW and was associated with a seismic signal indicating fluid movement. The plume was visible on webcams and from Manizales. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


3 August-9 August 2022 Citation IconCite this Report

On 2 August Servicio Geológico Colombiano’s (SGC) reported that during the previous week the number and size of seismic signals indicating fluid movement had increased at Nevado del Ruiz compared to the week before, though they remained at moderate levels. Although seismic signals indicating rock fracturing increased in number, magnitudes were similar to the previous week. Several episodes of drumbeat seismicity were recorded, indicating continuing growth of the lava dome. Gas-and-steam emissions rose from the crater, reaching just over 2.4 km above the summit on 30 July. Several thermal anomalies in Arenas Crater were identified in satellite images during 0500-0600 on 4 August, and seismic signals indicating emissions were recorded during 4-5 August. Ashfall was reported in the municipalities of Santa Rosa de Cabal, Pereira, Villamaría, Manizales, and Dosquebradas. Tephra deposits were visible near the crater and in areas up to 3 km away. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


4 May-10 May 2022 Citation IconCite this Report

On 10 May Servicio Geológico Colombiano’s (SGC) reported that during the previous week the number of seismic signals indicating both rock fracturing and fluid movement at Nevado del Ruiz had increased compared to the week before. Several episodes of drumbeat seismicity were recorded on 5 and 8 May, indicting growth of the lava dome. Some low-temperature thermal anomalies were also identified at Arenas Crater. Gas-and-ash emissions were periodically visible in webcam images. A small ash emission on 3 May caused minor ashfall in the municipalities of Manizales (25 km N), Dosquebradas (40 km W), Santa Rosa, and Pereira (40 km WSW). At 0857 on 9 May an ash plume drifted NW, W, and SW, causing ashfall in Manizales, Villamaría (28 km NW), and Chinchiná (30 km WNW) in the department of Caldas, and in Pereira, Dosquebradas, and Santa Rosa de Cabal (33 km W) in the department of Risaralda. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


6 April-12 April 2022 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that at 1713 on 11 April a seismic signal at Nevado del Ruiz was recorded along with an ash, gas, and steam plume. The plume rose almost 3.3 km above the summit and drifted N, causing minor ashfall around the volcano as reported by Parque Nacional Natural Los Nevados staff. It was also visible in webcam images and from the city of Manizales, 28 km NW. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


9 February-15 February 2022 Citation IconCite this Report

On 15 February Servicio Geológico Colombiano’s (SGC) reported that during the previous week seismicity at Nevado del Ruiz was at similar levels to the weeks before, characterized by periods of continuous volcanic tremor, harmonic tremor, long-period events, and very-long-period earthquakes, indicating movement of fluids. These earthquakes occurred in the vicinity of Arenas Crater. Additional earthquake signals indicating rock fracturing were located at Arenas Crater and in areas to the SE and had decreased in size and frequency since the previous week. Two periods of “drumbeat” seismicity, indicting growth of the lava dome, were recorded on 10 February. Gas-and-ash emissions were periodically visible in webcam images. A small explosion on 11 February generated an ash plume that rose above the crater. According to the Washington VAAC an ash plume rose to 7 km (23,000 ft) a.s.l. and drifted N at 1130 that same day. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC)


29 December-4 January 2022 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 28 December 2021 to 3 January 2022 seismicity at Nevado del Ruiz was at similar levels to the week before, characterized by periods of continuous volcanic tremor, long-period events, and very-long-period earthquakes, indicating movement of fluids. These earthquakes occurred in the vicinity of Arenas Crater. Additional earthquake signals indicating rock fracturing were located in the SW, SE, and NE parts of the volcano. Several periods of “drumbeat” seismicity, indicting growth of the lava dome, were recorded during 29-30 December and 3 January. Several low-level thermal anomalies were identified in satellite images during the week. The highest gas-and-steam plume rose about 1.2 km above the summit, recorded on 3 January. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


3 November-9 November 2021 Citation IconCite this Report

On 9 November Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that intense seismicity at Nevado del Ruiz had been recorded for the previous few weeks. Deformation data indicated minor changes. Low-temperature thermal anomalies were visible in satellite images during the previous week. Gas-and-steam emissions were sometimes visible in satellite data and webcam images rising as high as 1.9 km above the summit and drifting NE and E. These emissions sometimes contained ash; during 0735-0815 on 3 November an ash plume rose 1.4 km above the summit. Ash emissions on 7 November drifted W and NW, causing ashfall in Manizales and Villamar?a, both 25 km NW. The La Nubia airport temporarily suspended operations. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


25 August-31 August 2021 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 25-31 August seismicity at Nevado del Ruiz had generally decreased compared to the previous week. Deformation data indicated minor changes. Gas-and-steam emissions were sometimes visible in satellite data and webcam images rising as high as 1.2 km above the summit and drifting NW and W. These emissions sometimes contained ash; on 26 August an ash emission rose 490 m and drifted WNW. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


14 July-20 July 2021 Citation IconCite this Report

On 21 July Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity at Nevado del Ruiz was generally characterized by higher number of earthquakes that had larger magnitudes than the previous week. Gas-and-steam emissions were sometimes visible in webcam images rising as high as 1.1 km above the summit and drifting WNW and WSW; these emissions sometimes contained ash. Episodes of drumbeat seismicity were recorded during 13-14 and 17 July, indicating ascent or growth of a lava dome in Arenas Crater. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


2 December-8 December 2020 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 1-8 December seismicity at Nevado del Ruiz was generally characterized by higher number of earthquakes that had larger magnitudes than the previous week. Several episodes of drumbeat signals were recorded, indicating ascent or growth of a lava dome in Arenas Crater. Gas-and-ash emissions were sometimes visible in webcam images. Two thermal anomalies were visible in satellite data. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


29 July-4 August 2020 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) reported that a seismic signal associated with fluid movement beneath Nevado del Ruiz was recorded at 0636 on 30 July. Concurrently a small gas-and-ash plume visible with the webcam rose as high as 560 m above the summit. The Alert Level remained at 3, Yellow (the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


27 May-2 June 2020 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 27 May-2 June seismicity at Nevado del Ruiz was at similar levels to the week before, with signals dominated by periods of continuous volcanic tremor, tremor pulses, long-period, and very-long-period earthquakes. Some of the earthquakes were associated with minor gas-and-ash emissions that drifted N and were recorded by the webcam. The highest gas-and-steam plume rose about 1.3 km above the summit, recorded on 29 May. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


22 April-28 April 2020 Citation IconCite this Report

On 28 April Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that small ash-and-gas emissions from Nevado del Ruiz were periodically visible in webcam images and observed by Parque Nacional Natural Los Nevados officials during the previous week. These emissions drifted WSW and NW. A gas-and-steam plume rose 1.2 km above the crater rim on 21 April. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


18 March-24 March 2020 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that small and periodic ash-and-gas emissions from Nevado del Ruiz were visible in satellite and webcam images during 18-24 March. These emissions drifted NE and SE. A gas-and-steam plume rose 1.5 km above the crater rim on 23 March. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


11 March-17 March 2020 Citation IconCite this Report

Servicio Geológico Colombiano (SGC) reported that three gas-and-ash emissions from Nevado del Ruiz recorded on 10 March (at 0742, 1029, and 1055) rose 345-700 m above the summit and drifted SW, S, and SE. Minor ashfall was reported around the volcano and in towns downwind. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


2 October-8 October 2019 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 24 September-1 October seismicity at Nevado del Ruiz increased in both frequency and magnitude compared to the previous week. Steam-and-gas plumes rose as high as 1.4 km above the summit and drifted mainly NW. A tremor pulse recorded at 2353 on 29 September was associated with an ash plume that drifted NW and was observed by Parque Nacional Natural los Nevados (PNNN) officials, SGC staff in the field, and residents of Manizales (25 km NW). Seismicity continued to indicate gas-and-ash emissions during 1-4 October. Beginning at 0138 on 4 October seismicity increased; several ash emissions were visible during the morning in webcam images and by SGC staff in the field. The emissions rose as high has 800 m and drifted mainly NW, causing ashfall locally and in Manizales. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


24 July-30 July 2019 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 23-30 July small plumes of gas and ash rose from Nevado del Ruiz based on webcam images. A weak thermal anomaly was identified in satellite data. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


24 October-30 October 2018 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 24-30 October seismicity at Nevado del Ruiz continued to indicate unrest. Seismicity increased during 26-27 October, with signals concentrated in an area 4.6 km WSW of Arenas Crater at depths of 4-6 km. Plumes of water vapor, ash, and gas continued to rise from the volcano, and on 26 October a plume rose as high as 1.5 km above the crater rim. A weak thermal anomaly was identified in satellite data. The Alert Level remained at 3 (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


9 August-15 August 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 8-14 August seismicity at Nevado del Ruiz continued to indicate unrest; seismicity decreased as compared to the previous week. Plumes of water vapor and gas continued to be emitted from the volcano. A gas-and-steam plume rose 450 m above the crater rim on 8 August and drifted NW. A thermal anomaly was identified on 14 August. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


24 May-30 May 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 23-29 May seismicity at Nevado del Ruiz continued to indicate unrest. Five episodes of drumbeat seismicity (low-energy long-period events) were recorded between 1343 and 1930 on 29 May, likely signifying growing lava domes. Significant amounts of water vapor and gas continued to be emitted. Gas, steam, and ash plumes rose 880 m above the crater rim on 27 May and drifted NW and SW. A thermal anomaly was identified on 28 May. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


10 May-16 May 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 9-15 May seismicity at Nevado del Ruiz continued to indicate unrest; the number and magnitude of events were higher compared to the previous week. Significant amounts of water vapor and gas continued to be emitted. Gas, steam, and ash plumes rose 1.7 km above the crater rim on 12 May and drifted NW and SW. According to the Washington VAAC the Bogota MWO reported an ash emission on 13 May. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


26 April-2 May 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 25 April-2 May seismicity at Nevado del Ruiz continued to indicate unrest; the number and magnitude of events were higher compared to the previous week. Significant amounts of water vapor and gas continued to be emitted. Gas, steam, and ash plumes rose 1.2 km above the crater rim on 26 April and drifted NW and SW. A low-energy thermal anomaly was identified on 28 April. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


12 April-18 April 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 1822 on 14 April a seismic event at Nevado del Ruiz was recorded, associated with a gas-and-ash emission recorded by the webcam that rose almost 1.2 km above the crater. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


5 April-11 April 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 4-11 April seismicity at Nevado del Ruiz continued to indicate unrest. Signals indicating fracturing rock slightly increased in both size and number as compared to the previous week. During 10-11 April a period of short-duration and very low energy drumbeat signals were recorded, indicating rising magma. Water vapor and gas continued to be emitted. Gas, steam, and ash plumes rose 1.5 km above the crater rim on 10 April and drifted NW. Thermal anomalies were identified on 4, 6, and 7 April. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


22 March-28 March 2017 Citation IconCite this Report

Based on info from Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales, the Washington VAAC reported that on 26 March ash plumes from Nevado del Ruiz rose to an altitude of 7 km (23,000 ft) a.s.l. On 27 March the observatory reported that at 1029 a gas-and-ash plume rose 1.6 km above the crater rim and drifted E. The emission was associated with a seismic event and was also recorded by a webcam.

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC)


15 March-21 March 2017 Citation IconCite this Report

Based on satellite and webcam images, the Washington VAAC reported that on 17 and 20 March ash plumes from Nevado del Ruiz rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted NW and SW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


1 March-7 March 2017 Citation IconCite this Report

Based on satellite images, the Washington VAAC reported that on 4 March an ash plume from Nevado del Ruiz rose to an altitude of 7.6 km (25,000 ft) a.s.l. and drifted over 31 km NW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


22 February-28 February 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 21-27 February seismicity at Nevado del Ruiz continued to indicate unrest. Seismicity was highest during 23-26 February with earthquakes located at depths of 1.1-4 km, in areas SW of the volcano; the largest event was a local M 3.2. Signals indicating fracturing rock increased in both size and number as compared to the previous week. Significant amounts of water vapor and gas continued to be emitted. Gas, steam, and ash plumes rose 2 km above the crater rim on 25 February and drifted NW and SW. Thermal anomalies were identified on 21, 23, and 26 February. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


15 February-21 February 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 14-20 February seismicity at Nevado del Ruiz continued to indicate unrest. Earthquakes were located at depths of 1.1-1.7 km, in areas N, NE, SE, and SW of the volcano, but mainly beneath Arenas Crater. The largest event was a local M 1.4. Signals indicating fracturing rock increased in both size and number as compared to the previous week. Significant amounts of water vapor and gas continued to be emitted. Gas, steam, and ash plumes rose 1.2 km above the crater rim on 18 February and drifted NE, SE, and SW. Thermal anomalies were identified by the MIROVA system during 14, 16-17, and 19-20 February. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


25 January-31 January 2017 Citation IconCite this Report

Based on analysis of satellite images, the Washington VAAC reported that on 31 January an ash plume from Nevado del Ruiz rose to an altitude of 7 km (23,000 ft) a.s.l. and drifted W.

Source: Washington Volcanic Ash Advisory Center (VAAC)


11 January-17 January 2017 Citation IconCite this Report

Based on information from Servicio Geológico Colombiano (SGC), the Washington VAAC reported that on 13 January an ash emission rose from Nevado del Ruiz to an altitude of 7 km (23,000 ft) a.s.l. and drifted N. Weather clouds prevented satellite views of the emission, and the webcam recorded gas-and-steam emissions with possible ash content.

Source: Washington Volcanic Ash Advisory Center (VAAC)


4 January-10 January 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 3-9 January seismicity at Nevado del Ruiz continued to indicate unrest. Some of the seismic signals were associated with gas-and-ash emissions, as confirmed by webcam images and officials in the Parque Nacional Natural los Nevados. A low-energy thermal anomaly was identified by the MIROVA system on 9 January. On 6 January a gas, water vapor, and ash plume rose 2.5 km above the crater rim and drifted between SW and NE directions. A seismic event at 0745 on 8 January was associated with an ash emission which drifted SW. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


28 December-3 January 2017 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 27 December 2016-2 January 2017 seismicity at Nevado del Ruiz continued to indicate unrest. Some of the seismic signals were associated with gas-and-ash emissions, as confirmed by webcam images and officials in the Parque Nacional Natural los Nevados. A low-energy thermal anomaly was identified by the MIROVA system on 29 December. On 2 January a gas, water vapor, and ash plume rose 1.2 km above the crater rim and drifted between SW and NW directions. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


7 December-13 December 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 6-12 December seismicity at Nevado del Ruiz was characterized by a decrease in the number and magnitude of earthquakes compared to the previous week. Significant amounts of water vapor and gas rose from the crater. On 7 December a low-energy thermal anomaly near Arenas Crater was detected by the MIROVA system. On 9 December gas and water vapor plumes sometimes containing ash rose 2 km above the crater rim and drifted between SW and NW directions. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


30 November-6 December 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 29 November-5 December seismicity at Nevado del Ruiz was characterized by a decrease in the number and magnitude of earthquakes compared to the previous week. Significant amounts of water vapor and gas rose from the crater. On 2 December a gas, water vapor, and ash plume rose 2 km above the crater rim and drifted between SW and NW directions. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


16 November-22 November 2016 Citation IconCite this Report

Based on information from the Bogota MWO, the Washington VAAC reported on 16 November an ash plume from Nevado del Ruiz rose to an altitude of 6.7 km (22,000 ft) a.s.l. and drifted NE. Weather clouds prevented satellite views.

Source: Washington Volcanic Ash Advisory Center (VAAC)


26 October-1 November 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismic signals indicating ash emissions from Nevado del Ruiz were recorded at 0608 on 27 October and 1341 on 30 October. The ash plume from the 27 October event drifted NE; weather clouds prevented conformation of the second event. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


19 October-25 October 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 18-24 October seismicity at Nevado del Ruiz was characterized by a slight decrease in the number and magnitude of earthquakes compared to the previous week. Some seismic signals were associated with gas-and-ash emissions which were confirmed by webcam images, and Parque Nacional Natural los Nevados (PNNN) and SGC officials. A steam, gas, and ash plume rose 2 km above the crater and drifted W on 18 October. Two low-energy thermal anomalies were detected on 18 and 20 October. The Washington VAAC reported that on 19 and 20 October ash plumes rose to altitudes of 7.3 and 6.1 km (24,000 and 20,000 ft) a.s.l. and drifted NW and SW, respectively. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC)


12 October-18 October 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 11-17 October seismicity at Nevado del Ruiz was characterized by a decrease in the number and magnitude of earthquakes compared to the previous week. Gas-and-ash plumes were visible on 12 and 13 October. On 15 October gas, steam, and ash plumes rose as high as 2.5 km above the crater and drifted NW. The number of long-period events increased during 1800-2300 on 17 October; some of the signals were associated with gas-and-ash emissions. Significant amounts of water vapor and gas rose from the crater. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


5 October-11 October 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 4-10 October the number and magnitude of volcano-tectonic earthquakes at Nevado del Ruiz increased compared to the previous week. Long-period and very-long-period signals as well as pulses of tremor were also recorded. Significant amounts of water vapor and gas rose from the crater. At 1746 on 5 October an episode of volcanic tremor was associated with ash emissions recorded by area webcams. Gas, steam, and ash plumes rose 2 km above the crater on 8 October and drifted NE. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


28 September-4 October 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that a webcam recorded an ash plume rising from Nevado del Ruiz at 0558 on 29 September. Based on information from the Bogota MWO, the Washington VAAC reported on the same day that an ash plume rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted WSW. Later that day ASHTAM reports indicated an ash emission to an altitude of 8.5 km (28,000 ft) a.s.l. and drifted 13 km S, though cloud cover prevented webcam and satellite image views. An ash emission reported by the Bogota MWO rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted NE on 3 October. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


21 September-27 September 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 20-26 September seismicity at Nevado del Ruiz was characterized by an increased number of earthquakes and a slight decrease in the seismic energy compared to the previous week. Significant amounts of water vapor and gas rose from the crater. Gas, steam, and ash plumes rose 700 m above the crater on 21 September and drifted NW. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


14 September-20 September 2016 Citation IconCite this Report

Based on notices from the Bogota MWO and model data, the Washington VAAC reported that on 15 September an ash plume from Nevado del Ruiz rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted W.

Source: Washington Volcanic Ash Advisory Center (VAAC)


7 September-13 September 2016 Citation IconCite this Report

Based on satellite images, the Washington VAAC reported that ash emissions at Nevado del Ruiz began at 0615 on 13 September, producing a plume that rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted W. By 1345 the ash had dissipated.

Source: Washington Volcanic Ash Advisory Center (VAAC)


31 August-6 September 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 23-29 August seismicity at Nevado del Ruiz was relatively unchanged compared to the previous week. Significant amounts of water vapor and gas rose from the crater. Ash emissions occurred on several days, and sometimes several times per day. Based on notices from the Bogota MWO, satellite and webcam images, and model data, the Washington VAAC reported that during 2-3 September ash plumes rose to altitudes of 6.1-6.4 km (20,000-21,000 ft) a.s.l. and drifted W and NW. SGC noted that gas, steam, and ash plumes occasionally rose 1.8 km above the crater rim and drifted NW and W on 4 and 6 September. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC)


24 August-30 August 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 23-29 August seismicity at Nevado del Ruiz slightly increased compared to the week before. Significant amounts of water vapor and gas rose from the crater. Thermal anomalies were detected on 24 and 29 August. A period of tremor that started at 1747 on 26 August was associated with an ash emission that rose 900 m above the crater. A gas-and-ash plume, associated with a seismic signal at 1050 on 27 August, was confirmed by a pilot. Based on webcam images and seismic signals, an ash plume rose 1.3 km and drifted NW on 28 August. Gas, steam, and ash plumes occasionally rose 2.3 km above the crater rim and drifted NW and W on 29 August. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


17 August-23 August 2016 Citation IconCite this Report

Based on information from the Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales, the Washington VAAC reported that on 19 August an ash plume from Nevado del Ruiz rose to an altitude of 6.9 km (22,000 ft) a.s.l. and drifted W and SW. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Sources: Washington Volcanic Ash Advisory Center (VAAC); Servicio Geológico Colombiano (SGC)


3 August-9 August 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 2-8 August seismicity at Nevado del Ruiz remained at similar levels as the week before. Significant amounts of water vapor and gas rose from the crater. A gas, steam, and ash plume rose 850 m above the crater rim and drifted NW and W on 6 August. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


27 July-2 August 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 26 July-1 August seismicity levels at Nevado del Ruiz slightly increased as compared to the week before. Significant amounts of water vapor and gas rose from the crater. A gas, steam, and ash plume rose 700 m above the crater rim and drifted NW and W on 29 July. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


20 July-26 July 2016 Citation IconCite this Report

Based on notices from the Bogota MWO and model data, the Washington VAAC reported that on 24 July a possible ash plume from Nevado del Ruiz rose to an altitude of 7.2 km (23,000 ft) a.s.l. On 26 July an ash plume recorded by the webcam and identified in satellite images rose to an altitude of 6.9 km (22,000 ft) a.s.l. and drifted W. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Washington Volcanic Ash Advisory Center (VAAC)


13 July-19 July 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 12-18 July seismicity at Nevado del Ruiz slightly increased as compared to levels the week before. Several episodes of “drumbeat” earthquakes were recorded during 13, 15, and 16-17 July. These signals were low energy and indicated a growing lava dome. Significant amounts of water vapor and gas rose from the crater. Gas, steam, and ash plumes rose at most 500 m above the crater rim and drifted NW on 13, 14, 16, and 17 July. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


6 July-12 July 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that a webcam recorded minor ash emissions rising from Nevado del Ruiz during 6-7 July. Based on notices from the Bogota MWO, satellite images, and model data, the Washington VAAC reported that on 8 July ash plumes rose to altitudes of 6.1-6.4 km (20,000-21,000 ft) a.s.l. and drifted W. A thermal anomaly was visible on 9 July. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC)


29 June-5 July 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 28 June-4 July seismicity at Nevado del Ruiz slightly decreased. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 850 m above the crater rim and drifted NW on 28 June. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


22 June-28 June 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0822 on 27 June and at 0748 on 28 June episodes of volcanic tremor were associated with ash emissions that rose 1.8 and 0.9 km above Nevado del Ruiz, respectively. The emissions were confirmed by national park authorities and local residents. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


25 May-31 May 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 24-30 May seismicity at Nevado del Ruiz was characterized by long-period and very-long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.8 km above the crater rim and drifted NW and W on 25 May. A minor thermal anomaly near Arenas Crater was detected in satellite images on 27 May. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


18 May-24 May 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 17-23 May seismicity at Nevado del Ruiz was characterized by long-period and very-long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions. Significant amounts of water vapor and gas rose from the crater during the week. Ashfall was reported in La Florida, Manizales, on 20 May. According to a news article an ash emission on 22 May prompted closure of the La Nubia airport in Manizales. Later that day a gas, steam, and ash plume rose 2.5 km and drifted NW and W. Based on information from SGC, the Washington VAAC reported that on 17 May an ash emission rose to an altitude of 7 km (23,000 ft) a.s.l. Cloud cover in the area prevented satellite observations of the activity. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC); Salon


11 May-17 May 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 10-16 May seismicity at Nevado del Ruiz was characterized by long-period and very-long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions. Thermal anomalies near Arenas Crater were identified in satellite images during 11-12 May. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.7 km and drifted NW and W on 12 May. Based on information from SGC, the Washington VAAC reported that on 17 May an ash emission rose to an altitude of 7 km (23,000 ft) a.s.l. Cloud cover in the area prevented satellite observations of the activity. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Sources: Washington Volcanic Ash Advisory Center (VAAC); Servicio Geológico Colombiano (SGC)


4 May-10 May 2016 Citation IconCite this Report

Based on webcam views and information from SGC, the Washington VAAC reported that on 5 May an ash emission from Nevado del Ruiz rose to an altitude of 6.7 km (22,000 ft) a.s.l. and drifted NW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


27 April-3 May 2016 Citation IconCite this Report

Based on a SGC notice, the Washington VAAC reported that on 2 May an ash emission from Nevado del Ruiz rose to an altitude of 7 km (23,000 ft) a.s.l. and drifted NW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


20 April-26 April 2016 Citation IconCite this Report

Based on an SGC notice, the Washington VAAC reported that ash plumes from Nevado del Ruiz drifted over 10 km on 22 April and almost 20 km on 24 April. Possible ash emissions rose from the volcano on 25 April. Extensive weather clouds prevented satellite views on all three days.

Source: Washington Volcanic Ash Advisory Center (VAAC)


13 April-19 April 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 12-18 April seismicity at Nevado del Ruiz was characterized by long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions. Thermal anomalies near Arenas Crater were periodically identified in satellite images. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.5 km and drifted NW and NE on 12 April. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).

Source: Servicio Geológico Colombiano (SGC)


30 March-5 April 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0804 on 31 March an episode of short-duration volcanic tremor was associated with an ash emission that rose 3.5 km above Nevado del Ruiz. According to the Washington VAAC the ash plume drifted NW and SW. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC)


23 March-29 March 2016 Citation IconCite this Report

Based on an ASHTAM (a special Notice to Airmen for airborne ash), the Washington VAAC reported a possible emission from Nevado del Ruiz on 28 March. Ash was not identified in satellite images, though a thermal anomaly was detected. A period of increased seismicity was detected the next day, and observers reported another possible ash emission.

Source: Washington Volcanic Ash Advisory Center (VAAC)


16 March-22 March 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0606 on 18 March an episode of volcanic tremor was associated with an ash emission that rose 1.7 km above Nevado del Ruiz. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


9 March-15 March 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 8-14 March seismicity at Nevado del Ruiz was characterized by long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions. A gas, steam, and ash plume rose 1.8 km and drifted SW on 8 March. The next day an episode of volcanic tremor was associated with an ash emission recorded by the webcam and observed by National Park officials. Seismicity increased during 12-13 March. The largest earthquake was recorded at 0233 on 12 March; it was a local M 3, NW of Arenas Crater at a depth of 5.6 km. Significant amounts of water vapor and gas rose from the crater during the week. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


2 March-8 March 2016 Citation IconCite this Report

SGC reported that an episode of volcanic tremor at Nevado del Ruiz began at 0923 on 3 March and was associated with an ash plume that rose 3 km above the crater. Based on satellite and webcam images, the Washington VAAC stated that an ash plume rose to an altitude of 9.1 km (30,000 ft) a.s.l. (about 800 m higher than the SGC estimate) and drifted NW. Later that day satellite images detected an ash plume drifting 40 km W. According to the VAAC, the Bogota MWO reported that on 7 March an ash plume rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted WNW.

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC)


24 February-1 March 2016 Citation IconCite this Report

Based on notices from the Bogota MWO, pilot observations, and wind data, the Washington VAAC reported that on 24 February an ash plume from Nevado del Ruiz possibly rose to altitudes of 5.5-6.1 km (18,000-20,000 ft) a.s.l. and drifted NW and S. According to the VAAC, SGC reported an ash emission on 29 February.

Source: Washington Volcanic Ash Advisory Center (VAAC)


10 February-16 February 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 9-15 February seismicity at Nevado del Ruiz was characterized by long-period earthquakes and pulses of volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 1 and 7.6 km. The largest event was recorded at 0857 on 10 February; it was a local M 1.1, N of Arenas Crater at a depth of 5.7 km. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.5 km and drifted NW on 13 February. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


27 January-2 February 2016 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 26 January-1 February seismicity at Nevado del Ruiz was characterized by long-period earthquakes and continuous volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 1 and 8.7 km. The largest event was recorded at 1300 on 28 January; it was a local M 0.9, N of Arenas Crater at a depth of 3.2 km. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 850 m and drifted NW on 26 January. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


23 December-29 December 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 22-28 December seismicity at Nevado del Ruiz was characterized by long-period earthquakes and continuous volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 1 and 7.7 km. The largest event was recorded at 1457 on 28 December; it was a local M 1.4, 7 km N of Arenas Crater at a depth of 5.4 km. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.7 km and drifted NW on 28 December. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


16 December-22 December 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that a volcanic tremor signal at 0214 on 18 December may have been associated with an ash emission from Nevado del Ruiz, although dark conditions prevented visual confirmation. Volcanic tremor which began at 1247 on 20 December was associated with an ash emission observed by numerous people both near the volcano and in Manizales (30 km NW). Many also reported a strong sulfur odor. The permanent DOAS (Differential Optical Absorption Spectrometer) station detected the highest levels of sulfur dioxide measured since the current activity began. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


11 November-17 November 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 9-16 November seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 1 and 8.1 km. The largest event was recorded at 1637 on 9 November; it was a local M 1.5, E of Arenas Crater at a depth of 2.1 km. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 2 km and drifted NW and SW on 14 and 17 November. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


28 October-3 November 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 27 October-2 November seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 1.3 and 8.2 km. The largest event was recorded at 1409 on 31 October; it was a local M 1.3, SW of Arenas Crater at a depth of 2.6 km. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.7 km and drifted NW on 30 October. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


21 October-27 October 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 20-26 October seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 1.1 and 8.8 km. The largest event was recorded at 0953 on 21 October, a local M 2.3, near Arenas Crater at a depth of 3.4 km. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 2 km on 22 October. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


14 October-20 October 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 13-19 October seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 0.9 and 8.5 km. The largest event was recorded at 2328 on 13 October, a local M 1.8, near Arenas Crater at a depth of 2.7 km. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.8 km and drifted NW on 17 October. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


7 October-13 October 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 6-12 October seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 1.4 and 8.2 km. The largest event was recorded at 0802 on 11 October, with a local M 3.4, near Arenas Crater at a depth of 3.6 km. That event was felt by residents and corresponded to a seismic increase at the NE part of Arenas Crater. Thermal anomalies over the crater were detected in satellite images during 7 and 9-10 October. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.7 km and drifted NW on 8 October. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


30 September-6 October 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 28 September-5 October seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 0.6 and 7 km. The largest event was recorded at 0138 on 4 October; the event was a local M 1.4, occurring at a depth of 4 km. Minor thermal anomalies over the crater were detected in satellite images on 28 and 30 September. Significant amounts of water-vapor and gas were emitted from the crater during the week. On 29 September a gas-and-ash plume rose 2 km above the crater and drifted mainly NW. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


23 September-29 September 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 22-28 September seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 1.3 and 7.5 km. The largest event was recorded at 1027 on 22 September, a local M 1.1, near Arenas Crater at a depth of 4 km. Water-vapor, gas, and ash plumes rose 2 km above the crater and drifted mainly NW. Thermal anomalies over the crater were sometimes detected in satellite images; a significant anomaly was detected on 26 September. A pulse of tremor at 1633 on 28 September was accompanied by an ash emission that drifted E and W. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


16 September-22 September 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 15-21 September seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Increases in seismicity were detected on 15 and 20 September, SW and N of Arenas Crater, respectively; the earthquakes were located at depths between 2.2 and 6.5 km, and were a maximum local M 2. Water-vapor-and-gas plumes rose 2.5 km above the crater and drifted mainly NW, and were sometimes tinged gray due to the presence of ash. Ashfall was reported in Manizales (30 km NW) and Pereira (40 km WSW). The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


9 September-15 September 2015 Citation IconCite this Report

On 14 September Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported continuing volcanic tremor at Nevado del Ruiz associated with gas-and-ash emissions. At 0725 an ash emission was also recorded by the webcam. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


2 September-8 September 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico and Sismológico de Manizales reported that during 1-7 September seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. In addition, volcano-tectonic (VT) events occurred at depths between 0.4 and 6.4 km. The largest VT event was recorded at 0017 on 2 September, was a local M 1.4, and was 1.5 km NE of Arenas Crater at a depth of 3.8 km. Incandescence was recorded by a webcam installed near the volcano. Water-vapor-and-gas plumes rose 1.4 km above the crater and drifted NW, and were sometimes tinged gray due to the presence of ash. Ashfall was reported in Manizales (30 km NW) and Pereira (40 km WSW). The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Sources: Servicio Geológico Colombiano (SGC); La Patria


26 August-1 September 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico and Sismológico de Manizales reported that during 25-31 August seismicity at Nevado del Ruiz increased; the network detected a large number of long-period earthquakes, and several episodes of tremor associated with gas-and-ash emissions. Water-vapor-and-gas plumes rose 2 km above the crater and were sometimes tinged gray due to the presence of ash. Volcano-tectonic (VT) events occurred at depths between 0.77 and 6.77 km. The largest VT event was recorded at 0144 on 27 August, was a local M 1.1, and was 2.8 km SW of Arenas Crater at a depth of 4.69 km. Periods of very-high-energy tremor were detected on 31 August. According to a news article, La Nubia airport ceased operations on 31 August due to ash emissions.

Sources: Servicio Geológico Colombiano (SGC); W Radio


19 August-25 August 2015 Citation IconCite this Report

On 23 August Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico and Sismológico de Manizales reported that volcanic tremor associated with ash emissions from Nevado del Ruiz continued. Ashfall was confirmed by officials from Civil Aviation and the Parque Nacional Natural de los Nevados, as well as residents in Pereira. Earthquakes were located under the NE part of Arenas Crater, at depths between 3.5 and 5 km. The largest event was local M 2.

Source: Servicio Geológico Colombiano (SGC)


5 August-11 August 2015 Citation IconCite this Report

Based on satellite images, the Washington VAAC reported that on 6 August two small ash puffs from Nevado del Ruiz rose to an altitude of 7.3 km (24,000 ft) a.s.l. and drifted NW. Ash emissions later that day drifted over 20 km NW.

Source: Washington Volcanic Ash Advisory Center (VAAC)


29 July-4 August 2015 Citation IconCite this Report

The Washington VAAC reported bright thermal anomalies at Nevado del Ruiz visible in satellite images on 31 July; a brief increase in seismicity was detected, and the thermal anomaly was weaker in subsequent images.

Source: Washington Volcanic Ash Advisory Center (VAAC)


22 July-28 July 2015 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico and Sismológico de Manizales reported increased tremor at Nevado del Ruiz during the morning of 26 July. The webcam recorded an ash plume at 0830 that rose 3 km and drifted NW to SW; ashfall was reported in areas downwind including the municipalities of Chinchiná, Palestina, Santa Rosa de Cabal, Dosquebradas, and Pereira. Later than day seismicity decreased and the webcam showed gas-and-steam emissions that rose 300 m.

Source: Servicio Geológico Colombiano (SGC)


15 July-21 July 2015 Citation IconCite this Report

According to the Washington VAAC, the Manizales Observatory reported that activity at Nevado del Ruiz increased at 0530 on 18 July, and an ash plume rose to an altitude of 6.1 km (20,000 ft) a.s.l. Weather clouds prevented satellite and webcam views. Later that day the Bogata MWO reported that an ash plume drifted SW at an altitude of 6.1 km (20,000 ft) a.s.l., and a NOTAM detailed an ash plume drifting S at the same altitude.

Source: Washington Volcanic Ash Advisory Center (VAAC)


3 June-9 June 2015 Citation IconCite this Report

Based on webcam views and information from the Manizales Observatory, the Washington VAAC reported that on 6 June an ash emission from Nevado del Ruiz rose 800 m above the summit and drifted WNW. Weather clouds prevented satellite views.

Source: Washington Volcanic Ash Advisory Center (VAAC)


27 May-2 June 2015 Citation IconCite this Report

The Washington VAAC reported that on 26 May an ash emission from Nevado del Ruiz was visible in the webcam and reported by the Air Force Weather Agency (AFWA). Weather clouds prevented satellite views.

Source: Washington Volcanic Ash Advisory Center (VAAC)


22 April-28 April 2015 Citation IconCite this Report

Based on satellite image analyses, the Washington VAAC reported that on 22 April a small puff of gas with minor amounts of ash from Nevado del Ruiz drifted over 40 km W and dissipated.

Source: Washington Volcanic Ash Advisory Center (VAAC)


7 January-13 January 2015 Citation IconCite this Report

According to a news article, increased ash emissions at Nevado del Ruiz prompted the closure of the La Nubia airport on 7 January.

Source: Prensa Latina


17 December-23 December 2014 Citation IconCite this Report

Based on a SIGMET notice from the Bogota MWO, the Washington VAAC reported that on 18 and 19 December ash plumes from Nevado del Ruiz rose to altitudes of 7.9 and 9.1 km (26,000 and 30,000 ft) a.s.l., respectively. The plumes drifted SSW. A faint thermal anomaly was detected between cloud cover.

Source: Washington Volcanic Ash Advisory Center (VAAC)


10 December-16 December 2014 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico and Sismológico de Manizales reported that on 15 December at 0738 seismic signals indicating ash emissions were detected, and then confirmed, by a local webcam and residents. Based on a pilot observation, the Washington VAAC noted that an ash plume drifted almost 20 km S that same day. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


10 July-16 July 2013 Citation IconCite this Report

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico and Sismológico de Manizales reported that during 8-14 July gas-and-steam plumes rose 600 m above Nevado del Ruiz’s crater and drifted NW. Sulfur dioxide emissions were significant. Seismicity was dominated by volcano-tectonic signals. The earthquakes were located NE, S, and SW of Arenas Crater; the largest was a M (local) 2.1 located SW of Arenas Crater at a depth of 3.4 km. Shallow seismicity associated with fluid movement occurred S and SE of the crater. During 11-12 July continuous volcanic tremor associated with emissions was detected; ashfall was reported in Los Nevados Natural Park and in some parts of Manizales (30 km NW). The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


10 April-16 April 2013 Citation IconCite this Report

INGEOMINAS reported that during 13-14 April seismicity associated with fluid movement beneath Nevado del Ruiz was detected along with volcano-tectonic earthquakes. The earthquakes were located NW of Arenas Crater at depths between 5 and 9 km; the largest was a M 2.6, felt by officials of Los Nevados National Park in the area of Brisas (50 km SW). During the early morning of 14 April webcams recorded a gas-and-ash plume that rose 630 m and drifted NW. On 15 April a M 3 volcano-tectonic earthquake was located NW of Arenas Crater at a depth of 6.6 km. Later that day a M 2.5 volcano-tectonic earthquake was located again NW of Arenas Crater at a depth of 5.78 km. On 16 April at 0714 a M 3.2 earthquake was located in the same area at a depth of 6.22 km. Earthquakes continued to be felt by officials in the National Park. A gas-and-steam plume rose 1 km above the crater and drifted SW. Sulfur dioxide emissions were significant and deformation was detected. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


16 January-22 January 2013 Citation IconCite this Report

Based on analysis of satellite imagery, the Washington VAAC reported that on 16 January a diffuse plume from Nevado del Ruiz possibly contained ash and drifted almost 55 km NE. A thermal anomaly was also detected. INGEOMINAS reported significant emissions of mostly gas and steam during 14-20 January; plumes rose 1.6 km above the crater and drifted E and SE, and then W during the later part of the week.

Sources: Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC)


14 November-20 November 2012 Citation IconCite this Report

Based on analysis of satellite imagery and reported seismic activity, the Washington VAAC issued a notice about a possible eruption from Nevado del Ruiz on 15 November. Cloud cover prevented observations of a possible ash plume but elevated seismicity was detected. A few hours later seismicity decreased and a faint thermal anomaly was detected. About six hours after that seismic activity remained low and no anomaly was detected.

Source: Washington Volcanic Ash Advisory Center (VAAC)


5 September-11 September 2012 Citation IconCite this Report

According to INGEOMINAS, on 5 September the Observatorio Vulcanológico and Sismológico de Manizales reported that seismicity at Nevado del Ruiz significantly decreased, both in the number and magnitude of the earthquakes. Field measurements and analysis of satellite imagery continued to show a significant amount of sulfur dioxide in the atmosphere. A steam-and-gas plume rose 400 m and drifted W. Later that day, INGEOMINAS decreased the Alert Level to III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


29 August-4 September 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 30-31 August variations in volcanic tremor amplitude were detected at Nevado del Ruiz, possibly associated with continuing gas and ash emissions. Seismic activity was low during 2-4 September. Cloud cover mostly prevented observations of the volcano; a white gas plume rose 200 m on 4 September and drifted W and SW. During 3-4 September field measurements and analysis of satellite imagery showed a significant amount of sulfur dioxide in the atmosphere. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


22 August-28 August 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 22-28 August variations in volcanic tremor amplitude were detected at Nevado del Ruiz, possibly associated with continuing gas and ash emissions. Cameras located near the volcano showed gas plumes rising 800 m above the crater and drifting NE on 23 August, and rising 1 km the next day. Gas plumes rose 300-500 m and drifted W and N during 26-28 August. Field measurements and analysis of satellite imagery showed a significant amount of sulfur dioxide in the atmosphere during 24 and 26-27 August. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


15 August-21 August 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 15-16 and 18-21 August variations in volcanic tremor amplitude were detected at Nevado del Ruiz, possibly associated with continuing gas and ash emissions. Earthquakes indicative of fracturing rock were located SE at depths of 1.5-4 km, with magnitudes less than 1. One event on 18 August was a M 2, located 1.17 km SW of Arenas Crater at a depth of 3.6 km. Web cameras showed gas-and-ash plumes rising 400 m and drifting W and NW during 15-16 August. A gas plume rose 400 m and drifted NW on 19 August. During 20-21 August field measurements and analysis of satellite imagery showed a significant amount of sulfur dioxide in the atmosphere. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


8 August-14 August 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 10-13 August low levels of tremor were detected at Nevado del Ruiz, possibly associated with continuing gas and ash emissions. On 12 August a total of 140 low-magnitude earthquakes (M < 1.8) were detected in a seismic swarm that began at 0956 and ended at 1800. The earthquakes were located about 4 km WSW of Arenas Crater at depths of less than 5 km. A gas-and-ash plume observed with a web camera rose 1 km above the crater and drifted W. Ashfall was reported in Brisas (50 km SW). Satellite images showed continuing sulfur dioxide emissions. On 13 August a seismic swarm was characterized by events less than M 1, and located NE of Arenas Crater at depths between 3 and 5 km. A thin layer of ash was deposited at the observatory in Manizales. Weather conditions prevented observations of the volcano. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


1 August-7 August 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 3-6 August low levels of tremor were detected at Nevado del Ruiz, possibly associated with continuing gas and ash emissions. Ashfall and a strong sulfur odor were reported in Manizales (30 km NW) and in the municipality of Chinchiná (30 km WNW). Satellite images showed continuing sulfur dioxide emissions on 6 August. Web cameras near the volcano recorded a gas-and-steam plume rising 700 m that drifted SW on 8 August. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


25 July-31 July 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that on 31 July web cameras at Nevado del Ruiz showed gas-and-ash plumes rising 300 m above the crater. Seismicity was low. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


18 July-24 July 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 22-24 July low levels of tremor were detected at Nevado del Ruiz, possibly associated with continuing gas and ash emissions. Satellite imagery and ground-based observations on 22 July showed high levels of sulfur dioxide emissions. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


11 July-17 July 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that on 11 July seismicity at Nevado del Ruiz decreased, however the data continued to indicate gas and ash emissions during 11-17 July. Satellite imagery and ground-based observations showed sulfur dioxide emissions. On 11 July ashfall was reported in Pereira (40 km WSW). The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


4 July-10 July 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 5-9 July seismic signals at Nevado del Ruiz indicated continuing gas and ash emissions. On 6 July a gas-and-ash plume rose 400 m above the crater and drifted SW. On 8 July gas-and-ash plumes rose 400-500 m above the crater and drifted NW and W. The Washington Volcanic Ash Advisory Center (VAAC) reported that a gas-and-ash plume was observed in satellite imagery drifting 65 km. On 9 July INGEOMINAS noted that a gas-and-ash plume, observed with a web camera, rose around 400 m above the crater. On 10 July satellite imagery and ground-based observations showed sulfur dioxide emissions. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Sources: Washington Volcanic Ash Advisory Center (VAAC); Servicio Geológico Colombiano (SGC)


27 June-3 July 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that a significant concentration of sulfur dioxide was detected rising from Nevado del Ruiz during 28-29 June. Seismic signals indicated continuing gas and ash emissions.

On 30 June an eruption produced an ash plume that rose 8 km above the crater and drifted SW. The Alert Level was raised to I (Red; "imminent eruption or in progress"). Ashfall was reported in areas near the volcano including Manizales (30 km NW) and Villamaría (28 km NW). According to news reports, communities around the volcano evacuated, and airports in Manizales, Pereira, and Armenia closed. By 2 July seismicity had decreased to low levels; the Alert Level was lowered to II (Orange; "eruption likely within days or weeks"). The Washington VAAC reported that a 7.5-km-wide ash plume was detected in satellite imagery drifting 75 km W. INGEOMINAS noted that seismic signals indicated continuing gas and ash emissions on 3 July.

Sources: Reuters; Servicio Geológico Colombiano (SGC); Washington Volcanic Ash Advisory Center (VAAC); Colombia Reports


20 June-26 June 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that a high concentration of sulfur dioxide was detected during 20-22 June. Reports on 22 and 25 June stated that seismic signals had indicated continuing gas and ash emissions. Web camera images showed steam-and-gas plumes rising 300 m and drifting NW on both days. On 26 June seismicity was low. Sulfur dioxide emissions continued to be significant. The Alert Level remained at II (Orange; "eruption likely within days or weeks") on 26 June.

Sources: Washington Volcanic Ash Advisory Center (VAAC); Servicio Geológico Colombiano (SGC)


13 June-19 June 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported on 15 June that satellite image analyses and field observers of Nevado del Ruiz indicated significant sulfur dioxide emissions. Seismic signals on 15 and 18 June indicated continuing ash emissions. Based on analysis of satellite imagery and web camera views, the Washington VAAC reported that on 17 June a 5.5-km-wide gas plume, possibly containing ash, drifted more than 90 km NW. The VAAC noted on 18 June that INGEOMINAS reported a gas-and-ash plume drifting N and NW at an altitude of 6.1 km (20,000 ft) a.s.l. The plume was later detected in satellite imagery drifting more than 90 km NW. The Alert Level remained at II (Orange; "eruption likely within days or weeks") on 19 June.

Sources: Washington Volcanic Ash Advisory Center (VAAC); Servicio Geológico Colombiano (SGC)


6 June-12 June 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that a satellite image of Nevado del Ruiz acquired on 6 June showed an ash plume rising from the crater and drifting NW, and ash deposits on the N, NW, W and SW flanks. Based on analysis of satellite imagery and information from INGEOMINAS, the Washington VAAC reported that gas plumes possibly containing some ash drifted 75-110 km W, WNW, and N during 7 and 9-10 June. Ash plumes drifted almost 30 km SE on 8 June. INGEOMINAS reported that on 11 June seismic signals indicated continuing ash emissions. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Sources: Washington Volcanic Ash Advisory Center (VAAC); Servicio Geológico Colombiano (SGC)


30 May-5 June 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that on 4 June observations of Nevado del Ruiz during an overflight and through web cameras located in the vicinity of Arenas Crater revealed that gas-and-ash plumes rose at most 1 km above the crater and drifted W and NW. The next day seismic signals indicated that ash emissions continued. Field observers noted that sulfur dioxide emissions were significant. Based on analysis of satellite imagery, the Washington VAAC reported that an ash plume drifted 40 km W. The VAAC also noted that the Bogota MWO reported ash emissions drifting NNW at an altitude of 9.1 km (30,000 ft) a.s.l. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


23 May-29 May 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that on 22 May a seismic signal possibly indicated an ash emission from Nevado del Ruiz, though it was not confirmed due to poor weather conditions. On 29 May activity significantly increased; at 0307 seismic signals indicated ash emissions that were confirmed by officials and residents near the volcano as well as with a web camera. The Alert Level was raised to II (Orange; "eruption likely within days or weeks"). A gas-and-ash plume rose 1 km above the crater and ashfall was reported in Anserma (65 km NW), Aranzazu (45 km NNW), Chinchiná (30 km WNW), Dosquebradas (40 km W), Filadelfia, La Merced (60 km NNW), Manizales (30 km NW), Marmato (70 km NNW), Neira (37 km NW), Palestina (40 km WNW), Pereira (40 km WSW), Risaralda (78 km WNW), Salamina (60 km NNW), San José (56 km NW), Santagueda (40 km NW), Santa Rosa de Cabal (33 km W), Supia (72 km NNW), Villamaria (28 km NW), and Viterbo (65 km WNW). Ash also fell in all municipalities in the department of Risaralda (76 km WNW) and El Aguila (85 km W, N of Valle del Cauca). Sulfur dioxide plumes were detected by satellite and a sulfur dioxide odor was reported in multiple towns. Later that day ash emissions rose 600 m above the crater.

Source: Servicio Geológico Colombiano (SGC)


2 May-8 May 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 1-2 May both satellite images and field observers indicated that steam and sulfur dioxide emissions rose from Nevado del Ruiz. Seismicity continued to decrease. On 3 May the Alert Level was lowered to III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


25 April-1 May 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 25-26 and 28-30 April video data and observers in the city of Manizales (25 km NW) indicated that gas-and-steam plumes rose 0.5-2 km above Nevado del Ruiz's crater. Cloud cover prevented observations on 27 April. Seismic signals indicated that an ash plume was emitted at 1248 on 30 April however cloud cover prevented observations. Seismicity fluctuated, but decreased. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


18 April-24 April 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 18-19 April multiple seismic signals recorded at Nevado del Ruiz possibly indicated ash emissions, but they could not be verified due to weather conditions. Video data and observers in the city of Manizales (25 km NW) indicated that gas-and-steam plumes rose 900 m above the crater and drifted SE during the morning on 18 April. Satellite imagery detected a steam and sulfur dioxide plume the next day. During 20-24 April high levels of sulfur dioxide were detected in satellite images. Gas-and-steam plumes rose 1-2 km above the crater. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


11 April-17 April 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that seismicity at Nevado del Ruiz decreased during 11-15 April then slightly increased during 16-17 April. Earthquakes were located below or N of Arenas crater at depths of 1.5-2 km during 11-12 April. Earthquake events at 1146 and 1149 on 15 April were possibly associated with ash emissions which were not verified due to weather conditions. Earthquakes detected on 16 April occurred E of Arenas crater at depths of 1.5-4 km.

Gas-and-steam plumes were observed mainly in satellite imagery, by cameras located near the volcano, and from the city of Manizales (25 km NW). On 12 April a sulfur odor was reported in the towns of Lebanon, Palocabildo, and Fresno (Tolima). Observes in Manila reported a gas-and-steam plume that rose 1.8 km above the crater on 16 April. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


4 April-10 April 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 4-10 April seismicity at Nevado del Ruiz fluctuated but remained elevated. Sulfur dioxide emissions also remained high; occasionally a sulfur odor was reported in Manizales, about 25 km NW. On 5 April a volcano-tectonic earthquake, M 2.8, occurred below Arenas crater at a depth of 1 km, and was the highest magnitude earthquake recorded since February. During 4-6 April gas-and-steam plumes drifted NW. Gas-and-steam plumes rose 3 km above the crater on 7 April and 1.5 km above the crater on 10 April; the plumes drifted SE both days. The Alert Level remained at II (Orange; "eruption likely within days or weeks").

Source: Servicio Geológico Colombiano (SGC)


28 March-3 April 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 24-31 March seismicity at Nevado del Ruiz increased significantly. Earthquakes indicating rock fracturing occurred W of Arenas crater, exhibiting a pattern observed prior to the eruptions in 1985 and 1989, although less energetic. Starting at 1054 on 29 March, and lasting for about 25 minutes, more than 135 earthquakes were detected S of Arenas crater at a depth of 4 km. At 0400 on 31 March earthquake signals indicating rock fracturing and fluid movement markedly increased. The Alert Level was raised to II (Orange; "eruption likely within days or weeks"). Seismicity remained elevated during 1-3 April; earthquakes were located below Arenas crater at depths between 0.5 and 3 km.

Source: Servicio Geológico Colombiano (SGC)


21 March-27 March 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 19-25 March seismicity at Nevado del Ruiz increased and gas emissions remained at significant levels. Gas plumes rose 2 km above Arenas crater and sulfur dioxide odors were reported by local people. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


14 March-20 March 2012 Citation IconCite this Report

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 12-18 March seismicity at Nevado del Ruiz decreased but gas emissions remained at significant levels. Gas plumes rose 2 km above the crater and sulfur dioxide odors were reported by local people. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").

Source: Servicio Geológico Colombiano (SGC)


7 March-13 March 2012 Citation IconCite this Report

INGEOMINAS reported a significant increase in seismicity at Nevado del Ruiz during 5-11 March. On 8 March scientists aboard an overflight observed a gas plume that rose 1.4 km above Arenas crater, originating from multiple emission sources and thermally anomalous areas within the crater. They noted ash deposits on the glacier, near the crater rim and on the E flank, likely from an explosion on 22 February. Later that day a small explosion detected by the seismic network produced an ash emission that was observed with a camera installed in La Piranha (NW). Increased sulfur dioxide emissions were also detected. Fieldwork revealed ash deposits at the headwaters of Gualí River, SW of Arenas crater.

Source: Servicio Geológico Colombiano (SGC)


29 September-5 October 2010 Citation IconCite this Report

INGEOMINAS reported a gradual increase in seismicity from Nevado del Ruiz on 30 September. Earthquakes were located beneath the Arenas crater at depths of 0.5-2 km. The largest earthquake was M 1.9. A plume of white gas rose 700 m above the caldera and a sulfur odor around the volcano was reported. The Alert Level was raised to III (Yellow; "changes in the behavior of volcanic activity") on 1 October. The report also noted changes in deformation and geochemistry during the previous few months. Seismic levels fluctuated during 2-3 October.

Source: Servicio Geológico Colombiano (SGC)


14 July-20 July 2010 Citation IconCite this Report

The Washington VAAC reported that a plume at an altitude of 7 km (23,000 ft) a.s.l. from a possible eruption from Nevado del Ruiz on 17 July was stated in a Bogota MWO SIGMET notice. A second VAAC report less than an hour later noted a brief seismic signal alert had been issued and that meteorological cloud cover prevented observations of the volcano. Ash was not seen in satellite imagery later that day nor were there any additional reports of activity. [INGEOMINAS later confirmed that no eruption had occurred.]

Source: Washington Volcanic Ash Advisory Center (VAAC)


12 June-18 June 2002 Citation IconCite this Report

On 9 June beginning at 2300 a swarm of volcano-tectonic earthquakes was recorded at Nevado del Ruiz. Next, hundreds of hybrid earthquakes were recorded, with more than 1,300 earthquakes occurring in 16 hours. High seismicity persisted for the following 3 days, with ~2,300 earthquakes recorded. This was the highest daily number of events recorded at Nevado del Ruiz since 1985. At the height of the activity the Alert Level was at Orange. In addition to heightened seismicity felt by residents near the volcano, jet-like sounds were reportedly heard that corresponded with some of the hybrid earthquakes, and the strong scent of SO2 was reported near the summit. No ash emissions were reported. By 13 June seismicity had decreased.

Sources: Servicio Geológico Colombiano (SGC); El Tiempo


Bulletin Reports - Index

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

05/1985 (SEAN 10:05) Increased seismicity and abnormal fumarolic activity

07/1985 (SEAN 10:07) Fumarolic activity increases; ash emissions

08/1985 (SEAN 10:08) Ash emission

09/1985 (SEAN 10:09) Phreatic activity and strong seismicity decline in October

10/1985 (SEAN 10:10) Lahars triggered by explosions kill more than 20,000

11/1985 (SEAN 10:11) Seismic swarms, latest with inflation; more on 13 November activity and products

12/1985 (SEAN 10:12) Small ash eruption; 15,000 evacuated; no new mudflows

01/1986 (SEAN 11:01) Seismicity; deformation; minor ash emission

02/1986 (SEAN 11:02) Strong SO2 emission; seismicity declines slightly

03/1986 (SEAN 11:03) Continued seismicity; minor deformation; small ash emission

05/1986 (SEAN 11:05) Six weeks of harmonic tremor; increased SO2; light ashfalls

06/1986 (SEAN 11:06) Strong seismicity continues; deformation NW of the summit

07/1986 (SEAN 11:07) Ash emissions preceded by B-type swarms and shallow events

08/1986 (SEAN 11:08) Stronger deformation; seismicity builds after brief decline

09/1986 (SEAN 11:09) Seismicity, deformation, and SO2 emission decline

10/1986 (SEAN 11:10) Strong earthquake swarm but weaker tremor

11/1986 (SEAN 11:11) High seismicity; temperatures increase in hot springs

12/1986 (SEAN 11:12) Shallow seismicity; minor ash emission; less SO2

01/1987 (SEAN 12:01) Seismicity, tilt, and gas emission remains stable

02/1987 (SEAN 12:02) Inflation precedes small ash eruptions

03/1987 (SEAN 12:03) More, shallower seismicity; deformation; gas kills animals

04/1987 (SEAN 12:04) Continued moderate-high seismicity; acid rain kills birds

05/1987 (SEAN 12:05) Ash emission; fine ash to 50 km W

06/1987 (SEAN 12:06) Peak 1987 SO2 emission; seismicity declines

07/1987 (SEAN 12:07) Seismicity continues; minor inflation

09/1987 (SEAN 12:09) Small ash emission; strong seismicity continues

10/1987 (SEAN 12:10) Small ash emission; seismicity; highest SO2 of 1987

11/1987 (SEAN 12:11) Seismicity increases; SO2 emission remains high

01/1988 (SEAN 13:01) Continued strong seismicity; slight SO2 increase

03/1988 (SEAN 13:03) Ash emission follows earthquake swarm

04/1988 (SEAN 13:04) More frequent ash emission; increased seismicity

05/1988 (SEAN 13:05) Small ash ejections; tremor; strong SO2 emission

06/1988 (SEAN 13:06) Daily ash emissions; continued strong seismicity

07/1988 (SEAN 13:07) SO2 emission and seismicity increase

08/1988 (SEAN 13:08) Small ash emissions; seismicity increases slightly

09/1988 (SEAN 13:09) Small ash emissions; continued strong seismicity

10/1988 (SEAN 13:10) Minor ash emission and continued vigorous seismicity

11/1988 (SEAN 13:11) Seismic energy release remains high

12/1988 (SEAN 13:12) High-frequency seismicity drops; energy release still high

01/1989 (SEAN 14:01) Seismic energy and number of event increase

02/1989 (SEAN 14:02) Seismic energy release increases; strong SO2 emission

03/1989 (SEAN 14:03) Small ash emissions; seismic energy release decreases

04/1989 (SEAN 14:04) Seismicity decreases

05/1989 (SEAN 14:05) High-energy seismic swarm

06/1989 (SEAN 14:06) Sharp increase in seismicity precedes ash emission

07/1989 (SEAN 14:07) Seismicity decreases; new summit depression

08/1989 (SEAN 14:08) Phreatomagmatic eruption; mudflow destroys bridge

09/1989 (SEAN 14:09) Small ash ejections; continued strong seismicity

10/1989 (SEAN 14:10) Seismic energy release declines

11/1989 (SEAN 14:11) Small ash explosions; moderate seismicity

12/1989 (SEAN 14:12) Small ash ejections; seismicity remains stable

01/1990 (BGVN 15:01) Four high-frequency seismic swarms N of the crater; weak tremor pulses but no ash emission; SO2 emission low

02/1990 (BGVN 15:02) Seismicity remains low

03/1990 (BGVN 15:03) Minor ash emission; seismicity remains low

04/1990 (BGVN 15:04) Seismicity remains low-moderate; glacial ablation significant

06/1990 (BGVN 15:06) Seismicity at low levels; no ash emissions

08/1990 (BGVN 15:08) Frequent ash emission with associated tremor; ashfall to 30 km; hot springs described

09/1990 (BGVN 15:09) Ash emissions with associated tremor; seismicity increases

10/1990 (BGVN 15:10) Small ash emissions and seismicity

11/1990 (BGVN 15:11) Minor ash emission; seismicity; SO2 flux declines

12/1990 (BGVN 15:12) Small ash emissions

01/1991 (BGVN 16:01) Minor ash emission; continued seismicity

02/1991 (BGVN 16:02) Small ash emissions with tremor

03/1991 (BGVN 16:03) Continued gas emission; two seismic swarms; ash to 30 km distance

04/1991 (BGVN 16:04) Tremor precedes several days of ash emission

05/1991 (BGVN 16:05) Frequent lithic ash emissions; occasional vigorous earthquake swarms

06/1991 (BGVN 16:06) Ash emission and low seismicity; increased SO2 flux

07/1991 (BGVN 16:07) Seismicity remains at low levels; small ash emissions

08/1991 (BGVN 16:08) Seismicity, deformation, and gas emission remain unchanged

09/1991 (BGVN 16:09) Seismicity and SO2 flux at low levels

10/1991 (BGVN 16:10) Continued weak seismicity and SO2 emission

11/1991 (BGVN 16:11) Seismicity weak; no deformation evident

01/1992 (BGVN 17:01) Weak steam emission; low-level seismicity

05/1994 (BGVN 19:05) Earthquake swarms in March and April end two years of low activity

05/1996 (BGVN 21:05) Earthquake swarms during July-September 1995 and January-April 1996

09/1996 (BGVN 21:09) Seismic swarms; gas plumes; newly found fumarolic field and hot spring

04/1999 (BGVN 24:04) Moderate earthquake swarm

05/2002 (BGVN 27:05) Largest earthquake swarm since 1985 occurs during June 2002

07/2012 (BGVN 37:07) 1988-2006 monitoring captures seismic swarms, deformation, and radon emissions

08/2012 (BGVN 37:08) Several years of escalating seismicity followed by ash explosions

07/2014 (BGVN 39:07) Frequent ash plumes during September 2012-July 2013; continuing gas emissions

06/2017 (BGVN 42:06) Intermittent ash emissions July 2012-December 2015; increased thermal activity October-December 2015

12/2019 (BGVN 44:12) Intermittent ash plumes with significant gas and steam emissions during January 2016-December 2017

01/2020 (BGVN 45:01) Intermittent ash, gas-and-steam, and SO2 plumes, and thermal anomalies during January 2018-December 2019

08/2020 (BGVN 45:08) Lava dome confirmed inside Arenas crater; intermittent thermal anomalies and ash emissions, January-June 2020

01/2021 (BGVN 46:01) Dome growth and ash emissions continue during July-December 2020

06/2021 (BGVN 46:06) Low-level thermal activity and dome growth continues during January-April 2021

01/2022 (BGVN 47:01) Ash emissions increase in frequency during November-December 2021; dome growth continues

08/2022 (BGVN 47:08) Intermittent ash emissions, thermal activity, and dome growth during January-July 2022

02/2023 (BGVN 48:02) Gas-and-ash emissions, dome growth, and seismicity continued during August 2022-January 2023

08/2023 (BGVN 48:08) Intermittent gas-and-ash plumes, ashfall events, and seismicity during February-July 2023




Information is preliminary and subject to change. All times are local (unless otherwise noted)


May 1985 (SEAN 10:05) Citation IconCite this Report

Increased seismicity and abnormal fumarolic activity

"Since late November 1984, local earthquakes have been felt near the summit. On 22 December, stronger earthquakes were detected, followed by a half hour of apparent harmonic tremor. During a visit to the crater in early January 1985, increased fumarolic activity, evidence of phreatic explosions, and the wide deposition of sulfur salts over the adjacent snowcap were noted. At times, a thin layer of ash had been ejected, which was analyzed by J. Tomblin and found to consist of alteration products and sulfur.

"Seismic activity continued, with 17 felt earthquakes in March and 18 in April. There are no operating seismographs in the region. Abnormal fumarolic activity also continued. The one hot spring with frequent temperature monitoring, NW of the crater, had not shown any variation in temperature.

"Ruiz is a glacier-clad stratovolcano (bordering Tolima and Caldas Departments). . . . Colombian officials have begun the necessary studies."

Information Contacts: M. Hall, Escuela Politécnica, Ecuador; J. Tomblin, UNDRO; O. Gómez, Civil Defense Coordinator, Manizales.


July 1985 (SEAN 10:07) Citation IconCite this Report

Fumarolic activity increases; ash emissions

Increased thermal and seismic activity have continued. Scientists from the Central Hidroeléctrica de Caldas visited the crater on 8 July and found evidence of increased activity since their previous visit on 22 February. They reported intense noise from the fumaroles as well as increased fuming which frequently made breathing difficult. Sulfur deposits were more extensive than those noted on their previous visit. On 22 February, there had been only a thin film of sulfur covering the surface near the fumaroles, but by July sand-sized material on the inner slopes of the crater was impregnated with sulfur deposits, creating a crust 10 cm thick. A new crack was observed near the crater rim; it was 1.5 m in length, 8 cm wide, and emitted hot gas and vapors. Ground temperatures were measured at various locations as the team descended into the crater. Isotopic studies are being conducted on waters collected at thermal vents on the flanks of the volcano.

Much of the bottom of the crater was covered by a green lake that emitted hot steam from its surface. On 22 February, the lake had a pH of 0.2. The water in the lake had risen at least 1 m since February, covering a mud pool and its surrounding "mud volcano" seen on 22 February, and also nearby fumaroles. Projecting into the SE side of the lake on 8 July was a peninsula that was thought to be the remnant of these features. An unusual thaw of the glacial ice that covers much of the summit area seemed to have contributed to the rise in the water level. Further evidence for thawing came from the presence of large blocks of ice scattered near the base of the crater.

A major increase in fumarolic activity producing an enormous yellow vapor cloud was reported on 23 July.

Information Contacts: B. Salazar A., M. Calvache V., and N. Garciá P., Central Hidroeléctrica de Caldas.


August 1985 (SEAN 10:08) Citation IconCite this Report

Ash emission

Ash emission began 11 September at about 1300 and lasted up to 7 hours, accompanied by a persistent roaring noise and electrical discharges. A few millimeters of ash fell on the cities of Manizales and Chinchiná (about 30 km NW and WNW of the volcano) and ashfall was reported to have locally reached 2 cm. A mudslide blocked a road on the E flank of the volcano. Before the eruption, tremors were recorded at about 1.5-hour intervals by seismographs about 3 km N, S, E, and W of the volcano's summit. Tremor was continuous during the ashfall, punctuated by discrete earthquakes.

On 13 September, morphological changes in the glaciers on the W side of Ruiz were reported by ground and air observers. New fissures were also reported on the icecap N of and below the active crater near a small growing pond on the glacier surface.

Nevado del Ruiz is a broad shield-shaped volcano covering more than 200 km2, composed of an extensive sequence of hypersthene-augite andesite, hornblende andesite, basaltic andesite, and dacite. Its 1595 eruption produced ash and lapilli falls and lahars that spilled down the Río Gualí and Río Lagunillas Valleys N and E of the volcano. Eruptions were reported in 1828 and 1829, but no descriptions exist. Apparently these events produced no tephra. Ruiz is also reported to have been "smoking" in 1831 and 1833 (Herd, 1982).

Reference. Herd, D.G., 1982, Glacial and volcanic geology of the Ruiz-Tolima Volcanic Complex, Cordillera Central, Colombia: Publicaciones Geológicas Especiales del INGEOMINAS, no. 8, 48 p.

Information Contacts: B. Salazar A., Central Hidroeléctrica de Caldas; Germán Mejía, Univ. Nacional, Manizales.


September 1985 (SEAN 10:09) Citation IconCite this Report

Phreatic activity and strong seismicity decline in October

After a series of magnitude-4 earthquakes on 22 December [1984] marked the onset of stronger seismicity, 25-30 events were felt each month until an episode of strong phreatic activity on 11 September. Seismologists have located about 100 earthquakes, centered 1-2 km NW of the active crater at average depths of 0-2 km below sea level. Increased thermal and phreatic activity began in early 1985 and continued after the 11 September episode into early October. No juvenile material has been recognized in the 1985 tephra.

The vigorous 11 September phreatic activity began at 1330 from the summit crater (Arenas) and had ended by the next morning. Ashfall was 1 cm or less near the volcano and a trace of ash reached Manizales and Chinchiná. Lithic blocks were deposited on snowfields as much as 2 km from the crater. Thunderous detonations and summit-area lightning accompanied the activity. A small- to moderate-sized lahar began at 1830, advancing 27 km down the valley of the NE flank's Río Azufrado, from 4,700 m to 3,000 m altitude. As it traveled at an estimated 10-30 km per hour, the lahar left the river channel at various locations, particularly along curves, and rose as high as 10-20 m up canyon walls. Valley residents were placed on alert but have not been evacuated. A hazard map has been prepared by the international team studying the volcano and distributed to Red Cross and Civil Defense officials.

For 5 days preceding the 11 September activity, seismographs registered a very regular pattern consisting of 15 minutes of strong high-frequency tremor every hour. Although similar seismicity was recorded during three other periods of a day or less in August and September, none of these episodes was as intense or long-lasting.

Phreatic activity was continuous for the rest of September, emitting variable amounts of ash, typically darkening the snow to a few kilometers from the crater. Heavier emissions occurred on 23, 24, and 29 September, producing dense dark plumes that deposited trace ashfalls more than 10 km from the crater and lithic blocks on nearby snowfields. Activity had declined by early October. A steam plume 1-3 km high was visible daily but contained no obvious ash. Seismographs recorded 5-10 microseismic events per day and an irregular harmonic tremor that may have been related to the steam plume. Geologists visited the crater at the beginning of October, noting a slight decline in fumarolic activity and little ash emission. Glaciers seemed unchanged since September.

Information Contacts: L. Jaramillo, INGEOMINAS, Bogotá; A. Rivera, Univ. de Caldas, Manizales; G. Duque, Univ. Nacional, Manizales; A. César, Central Hidroeléctrica de Caldas; A. Solano, Univ. Nacional de Colombia, Bogotá; M. Hall, Escuela Politécnica, Ecuador; D. Herd, USGS, Reston, VA.


October 1985 (SEAN 10:10) Citation IconCite this Report

Lahars triggered by explosions kill more than 20,000

An explosive eruption on 13 November melted ice and snow in the summit area, generating lahars that flowed tens of kilometers down flank river valleys, killing more than [25,000] people. This is history's fourth largest single-eruption death toll, behind only Tambora in 1815 (92,000), Krakatau in 1883 (36,000) and Mt. Pelée in May 1902 (28,000). The following briefly summarizes the very preliminary and inevitably conflicting information that had been received by press time. [An 11-page Appendix that originally appeared at the end of this issue presented a more detailed but equally preliminary chronology.]

After the moderate explosive activity (and 27-km lahar) of 11 September, there were several smaller ash ejection episodes through the end of September. Activity declined by early October to emission of a 1-3 km steam plume that contained no obvious ash. Low-level steaming with very little ash continued into late October, accompanied by occasional earthquakes, apparently tectonic, at about 12 km depth. Shallow (0-5 km) earthquakes, as many as 5 per day, were centered about 0.5 km N of the active crater. Three dry-tilt stations were established in late October, N, S, and W of the summit, and 11 days of data (before 5 November) suggested that some deflation was occurring.

Seismicity began to increase by 7 November, characterized by a series of high-frequency seismic swarms, although fewer than were associated with the 11 September ash emission. Continuous volcanic tremor began 10 November, but was weaker than the 11 September tremor.

No additional changes in seismicity were apparent before the onset of eruptive activity at about 1545 on 13 November. Ashfall reportedly began about 1600 in heavy rain at Mariquita (59 km NE of the summit) and lapilli with ash started falling about 1730 in Armero (46 km to the ENE) (figure 1). At 2109, Bernardo Salazar, tending seismic equipment 9 km from the summit, heard the start of strong explosions, much louder than those on 11 September, that shook the building and lit up the rain clouds "like a lamp." Heavy rains prevented Salazar from seeing the eruption column, but pumice to 15 cm in diameter began to fall by 2137, and 1-cm lapilli fell 18 km [W of] the summit. Ashfall at Armero increased about 2200. At 2220 a Caribbean Air Lines cargo plane flew through the eruption cloud at 8 km altitude. Pilot Manuel Cervera reported that "smoke" and the smell of sulfur filled the cabin, and his windows were etched. Two attempts to land at Bogotá failed, but he landed safely at Cali by putting his head out a side window.

Figure (see Caption) Figure 1. Map showing Ruiz volcano and its major drainages. Contour interval is 4,000 feet (about 1,200 m).

Lahars traveled down 11 flank valleys, the most destructive inundating the city of Armero, where an estimated [21,000] of 25,000 residents died. The first mud, which reached Armero about [2335], was cold [reports that the mud became increasingly hot were incorrect]. Resident E. Nieto described "A frightening noise and then a blast of wind hit us and we saw fire falling from the sky." On the volcano's W flank, low-lying neighborhoods of Chinchiná were also buried by mud, and officials estimated that [1,000] died there. Geologists estimated that the lahars advanced at 30-35 km per hour; Armero, at about 300 m elevation, is 5 vertical kilometers below the summit of Ruiz.

No pyroclastic flows were observed during the eruption, but geologists noted deposits with cross-stratification typical of those from surges. The Refugio (about 2 km NW of the summit) was knocked down and its walls scattered radially downslope.

In hand specimen, the 13 November tephra appeared to be a dacitic andesite, about 30-40% phenocrysts, with plagioclase dominant, more hornblende than pyroxene, and a trace of biotite. No estimates of tephra thickness, volume, or extent were available at press time, but ashfall was reported as far away as Táchira, Venezuela, 500 km to the NE. Tephra fell on all but the S and SE flanks.

NASA's Nimbus-7 polar orbiting satellite passed over Ruiz on 14 November at 1151. Using data from its TOMS instrument, Arlin Krueger calculated that a cloud containing more than 0.5 x 106 metric tons of SO2 covered a 650,000 km2 zone extending NE and slightly SW of the volcano (figure 2). Bernardo Londoño reported that the cloud extended to 10.5 km above the crater, but it remains uncertain whether the cloud reached the stratosphere. Heavy weather clouds prevented observation of the eruption on NOAA's weather satellite images. Lack of nearby wind data prevented precise altitude determination by correlation with cloud movement as indicated by Nimbus-7, but the available data suggested that it was upper tropospheric.

Figure (see Caption) Figure 2. Preliminary SO2 data from the TOMS instrument of the Nimbus-7 satellite at 1151 on 14 November 1985. Each number or letter represents the average SO2 value within an area 50 km across. Values above 9 are represented by A, B, C, etc. The area of perturbed values is shaded. Courtesy of Arlin Krueger.

As of 20 November, no additional strong explosions had occurred. Geologists who flew over the volcano reported that the crater had enlarged to about 300 m in diameter and 200 m deep, and that new fumaroles had developed 500-900 m from the crater, but they observed no lava flow. Newly installed telemetering seismometers recorded harmonic tremor of varying amplitude beginning 18 November at 0200 that preceded ash emission at 0600. An episode of stronger tremor that lasted from about 0600 to 0945 the next day was followed by a small explosion at 1030.

Information Contacts: B. Salazar A., Central Hidroeléctrica de Caldas; B. Londoño, Comité de Estudios Vulcanológicos, Manizales; D. Herd and R. Tilling, USGS, Reston, VA; N. Banks, USGS CVO, Vancouver, WA; A. Krueger, NASA/GSFC; M. Matson and W. Gould, NOAA/NESDIS; J. Tomblin, UNDRO; J. Barquero and R. van der Laat, Univ. Nacional, Heredia, Costa Rica; AP.


November 1985 (SEAN 10:11) Citation IconCite this Report

Seismic swarms, latest with inflation; more on 13 November activity and products

Since the 13 November eruption, activity at Ruiz has been limited to emission of a vapor plume and a few seismic swarms, one accompanied by measureable inflation. Work by numerous geologists has yielded new information on the 13 November eruption, its products, and pre-eruption activity.

Pre-13 November activity. The most vigorous seismic energy release at Ruiz occurred in the days preceding the 11 September ash emission. The rate of energy release increased prior to the 13 November eruption, but more gradually than before the 11 September activity. Hypocenters were concentrated N and NE of the summit with best-located events concentrated at depths 0-1 km below sea level (figure 3).

Figure (see Caption) Figure 3. Pre-13 November 1985 hypocenters projected onto a vertical E-W plane passing through the summit of Ruiz. Depths are below a datum at 3.8 km altitude. No vertical exaggeration. Reprinted from Estudio de los Riesgos Potentiales del Volcán Nevado del Ruiz; Informe de las Actividades Desarolladas (Periodo Octubre 8 - Noviembre 10, 1985); INGEOMINAS, Bogotá, Colombia.

The quoted material below is from a report from Rodolfo Van der Laat, Eduardo Parra, and Heyley Vergara.

"After 11 September, when there was a significant ash emission, activity at Ruiz had decreased notably through 10 November. The activity caused concern in Manizales (30 km NW of Arenas Crater), but the presentation by INGEOMINAS of a preliminary volcanic risk map (figure 4) calmed the population.

Figure (see Caption) Figure 4. Volcanic risk map presented by geologists from INGEOMINAS and the Univ. de Caldas to officials and the press before the 13 November 1985 eruption. Some redrafting has been done to facilitate reproduction in the Bulletin, but boundaries of hazard zones are unchanged.

"Seismic activity reached a maximum of 60 events per day 19-21 October, declining by 3 November to 3-5 daily locatable events. An increase in temperature of the thermal vent 'La Hedionda' (on the NE flank) may have been related to the increase in seismic activity.

"The height of the plume during this period decreased from about 3 km at the end of September and the beginning of October to about 800 m, with an occasional nucleus of ash 200-300 m high. There were two main fumarolic vents: one yellowish (sulfur), the smaller one gray/coffee-colored (ash derived from mud).

"A tilt network was established, detecting a general deflation 26 October-3 November, with small pulses of inflation of the order of 5-10 µrad per day. At the beginning of November, the first measurement was made of a geodesic net to monitor horizontal deformation by the Instituto Geográfico Agustín Codazzi."

13 November eruption and products. Details of the 13 November eruption sequence remain uncertain and field investigations were still in progress at press time. An initial explosion at 1530 deposited a very thin, fine-grained layer of ash around the summit and NNE of the volcano. The main explosion started at 2108 or 2109 and continued for 20-30 minutes. Five kilometers from the crater, tephra from the main explosion was 7 cm thick and included 30-cm pumice fragments, but the deposit thinned rapidly and was only 1-2 mm thick at Armero with similar amounts at Mariquita and Honda (75 km NE). Preliminary estimates by Haraldur Sigurdsson and Steven Carey place the volume of tephra at roughly 39 x 106 m3. Cloudy weather and lack of nearby wind data on 13 November impeded determination of the height of the Ruiz eruption column. Based on the position of tephra diameter isopleths, Sigurdsson and Carey inferred that the top of the eruption cloud reached [31] km altitude, but emphasized that most of the tephra probably remained in the upper troposphere [Naranjo and others, 1986].

Mudflows that moved E down the valleys of the Lagunillas and Azufrado rivers and inundated Armero were overlain by airfall tephra within 5-10 km of the volcano. However, the mudflow that moved W down the Río Claro valley to Chinchiná contained fresh pumice, and the fluid mudflow that traveled down the Gualí river washed tephra off vegetation, suggesting that both were generated after tephra ejection. The Armero mudflows emerged from both the Lagunillas and Azufrado valleys, which join upstream from the city. The first wave of mud, probably from the Lagunillas, was apparently colder, lighter colored, more water-rich, and formed a more extensive deposit than the second wave, probably from the Azufrado, which was hotter, coarser, and darker-colored. Donald Lowe estimated that outflow from the mouth of the Río Lagunillas reached about 47,500 m3/s. Preliminary calculations by Sigurdsson and Carey yield a volume of about 30-60 x 106 m3 for the deposits of the Armero, and Gualí and Chinchiná valley mudflows, plus about 30-90 x 106 m3 of water, roughly 6-18% of the pre-eruption volume of the summit ice cap. The Lagunillas mudflow probably included water from a lake that had been trapped behind a debris dam in that valley's headwaters for at least several months. Other estimates suggested that about 5% of the summit ice was removed during the 13 November eruption.

Preliminary chemical analyses of a few samples of the 13 November pumice suggest that it is a hypersthene andesite, very similar to an earlier pumice that was probably from Ruiz's last large eruption, in 1595. Little systematic variation was found in different-colored samples that had suggested mixed magma in hand specimen (table 1).

Table 1. Preliminary analyses of bulk compositions of Ruiz pumice (1-4) and glass septa (5-6). Numbers 1, 2, 5, and 6 are from electron microprobe analyses by William Melson and Deborah Reid Jerez; 3 and 4 are X-ray fluorescence analyses by Joseph Taggart.

Sample 1 2 3 4 5 6
SiO2 59.31 58.69 59.50 61.50 65.36 63.97
Al2O3 16.83 16.81 15.70 15.20 16.01 16.33
FeO* 5.87 5.72 5.94 5.44 3.98 4.14
MgO 5.40 5.13 4.94 3.98 1.51 1.54
CaO 6.30 6.04 6.11 5.43 3.81 4.24
K2O 1.87 1.85 3.67 3.66 3.47 3.15
Na2O 3.80 3.79 2.07 2.45 4.12 4.22
TiO2 0.82 0.81 0.67 0.65 0.77 0.77
P2O5 0.30 0.28 0.19 0.19 0.30 0.29
MnO -- -- 0.09 0.09 -- --
Total 100.50 99.12 98.90 98.60 99.33 98.65

Notes:
Samples 1 and 5: 13 November 1985 pumice collected by Stanley Williams. USNM116158.
Samples 2 and 6: Probable 1595 pumice collected by Stanley Williams. USNM116159.

Post-13 November activity. No significant eruptive activity occurred in the succeeding weeks. The vapor column varied in height from 200-300 m to 1-1.4 km. Rates of SO2 emission measured by COSPEC were 200 t/d on 18 November, 50 t/d on the 19th, and several thousand tons per day on 22 November. Possible new fissures have been observed near the summit along with possible development of a depression SW of the summit. However, the fissures may have been pre-existing features exposed by clearer weather and seasonal snowmelt. Slight advances of some of the summit glaciers have been noted, but no large-scale ice movements were apparent and there was no evidence of significant melting from below.

Six telemetering seismometers have been installed, ringing the summit at elevations of 4,000-4,500 m, supplementing the four-station seismic net that was in place before 13 November. Telemetering tiltmeters were emplaced at 4,200 m elevation on the NW flank, 4,600 m elevation on the NNW flank, and on the NE flank, and 8-10 EDM lines have been established, in addition to the dry-tilt network installed on the N flank in October.

Seismic energy release was at relatively low levels shortly after the 13 November eruption, but the slope of the energy release curve steepened in the succeeding weeks. Earthquake swarms that were small but of increasing energy occurred 19-20 and 27 November, and 6-7 December. Maximum magnitudes were 2.5-3 in the November swarms; the 6-7 December activity included two magnitude 3-3.5 shocks. Locations were available for only a few events, which were centered along a generally N-S trend, usually somewhat N of the crater. The swarms were not accompanied by measurable tilt episodes or obvious changes to the plume. The rate of seismic energy release doubled during the first day of a stronger swarm 12-13 December and Civil Defense personnel were put on alert. The same day, the NW flank tiltmeter recorded a 5 µrad tilt event, the first change recorded in the weeks since it was installed, and a NW flank EDM line shortened 14 cm between measurements 11 and 13 December. However, seismicity declined 13 December, and the seismic energy release curve was nearly flat 14-17 December.

Information Contacts: P. Medina, Comité de Estudios Vulcanológicos, Manizales; A. López R., INGEOMINAS, Bogotá; R. Van der Laat, Univ. Nacional, Heredia; E. Parra, INGEOMINAS, Medellín; H. Vergara, INGEOMINAS, Tolima; H. Sigurdsson and S. Carey, Univ. of Rhode Island; S. Williams and D. Lowe, Louisiana State Univ.; A. Londoño C., Univ. Nacional, Manizales; Néstor Garcia P., Industria Licorera de Caldas, Manizales; R. Stoiber and B. Gemmell, Dartmouth College; D. Harlow, USGS, Menlo Park, CA; C. Hearn, D. Klick, D. Herd, and R. Tilling, USGS, Reston, VA; J. Taggart, Jr., USGS, Denver, CO; W. Melson and D. Jerez, SI; P. Clemente-Colón, NOAA/NESDIS.


December 1985 (SEAN 10:12) Citation IconCite this Report

Small ash eruption; 15,000 evacuated; no new mudflows

Explosive activity on 4 January ejected a small amount of ash and was accompanied by vigorous seismicity. The 4 January activity did not generate mudflows or cause any apparent changes in river flow, but residents of low-lying areas were temporarily evacuated as a precautionary measure.

A series of earthquake swarms followed the 13 November eruption, including a strong swarm 12-13 December that was accompanied by deformation (figure 5). Seismicity then declined briefly, followed by a period of stronger seismicity 22-24 December, then diminished again at the end of December to about 10 events per day (M >= 0) and brief bursts of tremor. Epicenters were generally S of the active crater, extending E and W under the flanks. Before the 4 January eruption, focal depths decreased from 4-8 km to 2-5 km (below a datum at 3.8 km above sea level). EDM lines on the SW, N, NE, and E flanks began to show changes in the rate and/or direction of deformation between 19 and 24 December. Equipment problems prevented remeasurement of EDM lines immediately before the 4 January eruption, so the amount of pre-eruption inflation is uncertain. The net change in the lengths of several radial lines (of 5 km average length) measured 3 days after the eruption was about 10 cm, but this figure probably included substantial post-eruption deflation. By 28-30 December, small but distinct changes in rate or direction of tilt had begun to appear on all four electronic tilt stations (at 4,100 m elevation on the NE flank, 4,800 m on the W flank, about 3,900 m on the NW flank, and 4,600 m on the SE flank).

Figure (see Caption) Figure 5. Seismic energy release at Ruiz volcano, 20 July-19 December 1985. Timing of eruptions on 11 September and 13 November are shown. Courtesy of the Comité de Estudios Vulcanológicos.

Movement of cracks in summit glaciers continued through December and early January at roughly constant rates. Extensional changes of 5-10 cm per day were measured near the head of the Azufrado valley, and both extensional and compressional motion of a few mm to 5 cm per day elsewhere. Little baseline data exist on typical rates of glacier advance on Ruiz.

Strong seismicity began 3 January at about 2320, and was saturating seismographs within less than an hour. The seismicity was initially characterized by superimposed high- and low-frequency tremor, but tremor amplitude declined somewhat around 0115 and low-frequency (2-2.5 Hz) tremor began to dominate the seismic records at 0128. B-type earthquakes and explosion events accompanied the tremor. Darkness initially prevented direct observations of the summit, but ash began falling about 0300. The eruption cloud was small, generally 300-600 m high, occasionally rising to 1 km above the summit. Ashfalls were minor, concentrated around the summit and in a narrow zone to the WNW. Several hundred meters from the vent, new ash was only about 7 mm thick; 3 km downwind the deposit was only 2 mm deep; and only traces of ash were found more than 10 km away. Vigorous seismicity continued until about noon, then declined slowly until the eruption ended in mid-afternoon.

Evacuations of about 15,000 people from low-lying areas of the valleys of the Azufrado, Lagunillas, Recio, Gualí, Sabandija, and Chinchiná rivers began 4 January at about 0600. Most residents returned to their homes shortly after the eruption, but about 2,000 people remained evacuated 10 days later.

Smaller earthquake swarms occurred 5-7 January, then seismicity declined to about 1-2 A- or B-type events per hour, generally with magnitudes of 0 or less. No additional explosions or major increases in seismicity had occurred as of mid-January.

Further References. Herd, D.G., and Comité de Estudios Vulcanológicos, 1986, The 1985 Ruiz volcano disaster: EOS, v. 67, p. 457-460.

Katsui, Y., Takahashi, H., Egashira, S., Kawachi, S., and Watanabe, H., 1986, The 1985 eruption of Nevado del Ruiz volcano and associated mudflow disaster: Rep. Natur. Disast. Sci. Res., B-60-7, p. 1-102.

Naranjo, J.L., Sigurdsson, H., Carey, S., and Fritz, W.J., 1986, The November 13, 1985 eruption of Nevado del Ruiz volcano, Colombia: Tephra Fall and Lahars; Science, v. 233, p. 961-963.

Thouret, J.C., 1986, L'éruption du 13 Novembre 1985 au Nevado El Ruiz: L'originalité du dynamisme eruptif phréato-magmatique et plinien sur une calotte glaciaire aux latitudes equatoriales: Revue de Géographie Alpine, v. 74, no. 4, p. 373-391.

Valdiri Wagner, J. (ed.), 1987, Memorias del Simposio Internacional Sobre Neotectónica y Riesgos Volcánicos (Bogotá, Colombia, 1-3 Diciembre, 1986): Revista del Centro Interamericano de Fotointerpretación, v. 11, nos. 1-3, p. 1-399 (23 papers).

Williams, S.N., Stoiber, R.E., García, P.N., and others, 1986, Eruption of the Nevado del Ruiz volcano, Colombia, on November 13, 1985: gas flux and fluid geochemistry: Science, v. 233, p. 964-967.

Information Contacts: P. Medina, Comité de Estudios Vulcanológicos, Manizales; N. Banks, USGS CVO, Vancouver, WA; AP.


January 1986 (SEAN 11:01) Citation IconCite this Report

Seismicity; deformation; minor ash emission

Seismicity and deformation continued through early February, but there had been no eruptive episodes since the minor explosive activity on 4 January. Plume heights varied from 100 to ~1,000 m above the summit (often in a single day), partly dependent on the amount of rainwater accumulated in the crater. Weak ash emission occurred on some days, falling near the crater.

After the 4 January ash emission, about four mixed-frequency seismic events were recorded/day, declining to <1/day since 1 February. Between mid-January and mid-February, there were normally about 10 high-frequency events/day, with two small crises on 8 and 14 February of about 20 events each (M < 1). The low-frequency seismicity also registered about 10 events daily without significant variations. Depths were between 2 and 6 km below a datum at 3.8 km above sea level, with epicenters typically <2 km from the crater, closer than in December. In early February, events were concentrated in the NE part of the volcano [see also 11:02].

An electronic tilt station W of the crater measured inflation values of the order of 0.5 µrad/day until the end of January, then dropped to 0.2-0.3/day, while deformation on other flanks remained at lower rates (<0.1 µrad). A deformation event that started 18 January was measured by continuously recording tiltmeters 2 and 5 km NW of the summit and by EDM stations radiating W from the summit. About 20-25 mm/km of inflation accumulated before the episode ended 4-5 days later. Another small inflation episode was in progress on 13 February, totaling ~8 mm/km at a reflector ~4 km NE of the summit.

By February, rates of fissure displacements in the summit glaciers had slowed by as much as an order of magnitude, to millimeters or occasionally centimeters/day. Increased melting was observed but attributed to sunnier weather. Melting of ice caused buckling of overlying tephra layers that were as much as 6 m thick near the summit, producing features reminiscent of tumuli that form on top of block lava flows.

An improved alert system and additional hazard study has permitted some of the persons that had remained evacuated since 4 January to return to their homes.

Information Contacts: I. Mejía and E. Parra, Comité de Estudios Vulcanológicos, Manizales; A. Okamura, HVO.


February 1986 (SEAN 11:02) Citation IconCite this Report

Strong SO2 emission; seismicity declines slightly

Colombian geologists reported that microseismic activity diminished between mid-February and mid-March, with an average of 5 high-frequency and 12-15 low-frequency events daily. Seismic events of mixed frequency also diminished, to 1/day. Activity on 28 February was abnormally low, with only one low-frequency event. Epicenters were within 3-4 km of the crater, and focal depths were at 1-3 km below a datum at 4.7 km above sea level . . . .

The vapor column reached heights of 100-800 m, without significant ash emission. Rates of SO2 emission measured by COSPEC in early March were generally of the order of 500 t/d; during the afternoon of 4 March, values of ~1,000 t/d were recorded, about the same as a month earlier. Fissures in pyroclastic material on glaciers on the NE part of the volcano showed displacements of 20-30 mm/day. Electronic tilt instruments recorded ~0.1 µrad of inflation/day on the W flank. No significant changes were detected on the E flank.

Additional seismic information comes from Jim Zollweg. "After the 13 November eruption, a 6-station telemetry network was installed around the volcano. All stations use vertical 1-Hz seismometers and radio-telemeter to the Comité de Estudios Vulcanológicos headquarters in Manizales. Sites were chosen 4-10 km from Arenas, Ruiz's active crater. The first station was operating on 17 November, four stations were functioning by 28 November, and all six by 2 December, although some locations were changed later. Recording is analog using pen-and-ink or smoked paper.

"Seismic activity was moderate in November and December, consisting chiefly of high-frequency earthquakes with magnitudes to 3.5. There were about half as many low-frequency as high-frequency earthquakes during those months. About 1,300 earthquakes were counted in December (countable events had coda lengths of at least 5 seconds on the Olleta telemetry station). In January, activity was considerably lower because of a major decrease in the rate of occurrence of high-frequency events. Only a few surface-type events (gas emission signals or avalanches) were recorded by telemetry stations in any month. Instances of harmonic tremor sustained for more than a minute were also uncommon, particularly in December. The most important tremor recorded since the stations were installed occurred 3-5 January, preceding and during a minor eruption 4-5 January. This tremor was unusual because of its wide range of frequency content; frequencies of 7 Hz or more were recorded within a few hours of its onset, and frequencies as low as 0.7 Hz occurred later in the episode.

"Very few low-frequency earthquakes have been locatable, and those with epicenters that could be computed usually occurred near Arenas Crater (within the limits of accuracy of the solutions). More than 150 high-frequency earthquakes have been located, and 81 of the better solutions are plotted in figure 6. Events were located using the program HYPOINVERSE, and an ad-hoc crustal model based on geological considerations. Events plotted within the network have epicentral 95% confidence limits of 1 km or less. Those plotted outside the network may have epicentral 95% confidence limits as poor as 3 km, depending on distance from the network. Focal depths of the high-frequency events are usually between 2 and 5 km (beneath a datum at 4.7 km asl), but depend on the crustal model used. The probable error range makes it difficult to say whether there are significant depth differences between events.

Figure (see Caption) Figure 6. Earthquake epicenters at Ruiz, 28 November 1985-21 January 1986. The 5,000-m contour is outlined. Filled triangles are telemetered stations; others are shown by open triangles. Not all were operating simultaneously; PIRT and ARBO are no longer operating. Courtesy of Jim Zollweg.

"Most of the high-frequency earthquakes occurred in one of two linear zones that intersect under the center of Ruiz. The E-W-striking zone is ~6 km long and was responsible for most of the seismicity. There is an interesting temporal pattern to the epicenters. Locations between 28 November and 5 December mainly fell in the central and eastern parts of the E-W zone, whereas vigorous swarms 6-13 December were mainly confined to the W half of the zone. There was a pronounced hiatus in high-frequency activity 14-21 December, followed by a swarm of events 22-25 December along the second zone, striking NW-SE. Between 26 December and 3 January, earthquakes reverted to a small area near the intersection of the two zones. High-frequency activity was comparatively low in the weeks following the 4-5 January eruption. First motions have been mostly compressions for nearly all events under Ruiz, suggesting a normal faulting environment. The data for the high-frequency sequences suggest the intrusion of dike-like bodies of magma along pre-existing fault zones."

Deformation monitoring has been summarized by Barry Voight. "Preliminary data from EDM reflector stations suggest that much of the observed summit surface deformation is due to ice movement decoupled from underlying bedrock. The data place constraints on the volume of rock susceptible to massive gravitational failure. EDM reflector stations (Martica and Finger) were installed at ~5,100 m elevation near the center of the Río Azufrado headwall. They were first measured on 14 February. Preliminary data from repeated distance measurements to 7 March suggest that the motions of glacier ice and underlying bedrock are decoupled. The fracture pattern observed on the surface of the summit plateau E of Arenas Crater dominantly reflects the propagation of crevasse patterns through the veneer of surficial deposits. The steady outward motion of the summit area as deduced from observation of surficial fracturing and EDM monitoring mainly reflects movements in glacier ice rather than motion of underlying bedrock. At other locations, some cracks give the appearance of possibly extending into bedrock, for example at the septum separating the crater from the headwall of the Río Azufrado. Although my current impression is that all of the headwall is probably stable with respect to deep-seated rock failure, the potential for mass movement involving a portion of the crater remains to be thoroughly evaluated."

Fabian Hoyos P. reported that isotopic analyses of several hot springs and the crater fumarole were sampled on 8 July 1985 in cooperation with the Central Hidroeléctrica de Caldas (CHEC). Isotopic compositions of 8 July 1985 hot spring samples were similar to those reported in 1968 and 1980 to CHEC. Water vapor collected the same day from the summit crater fumarole had an isotopic composition corresponding to that of meteoric water precipitated at ~2,800 m asl (table 2). Other samples collected until just before the 13 November eruption are being analyzed.

Table 2. Isotope analyses by Sara Kealy, Arizona State Univ, of samples collected from fumaroles at Ruiz, 8 July 1985. Data courtesy of Fabian Hoyos P. and Sara Kealy.

Source delta 18O delta D
Aguas Blancas Hot Spring -102.1 -14.4
Termales Ruiz Hot Spring -104.8 -13.6
Crater fumarole -89.0 -12.9

Information Contacts: I. Mejía and E. Parra, Comité de Estudios Vulcanológicos, Manizales; A. Londoño, L. Rodriguez, and N. Rojas, Univ Nacional, Manizales; N. García, Industria Licorera de Caldas, Manizales; F. Hoyos, Univ Nacional, Medellín, Colombia; J. Zollweg, USGS, Univ of Washington; B. Voight, Penn State Univ; S. Williams, Louisiana State Univ.


March 1986 (SEAN 11:03) Citation IconCite this Report

Continued seismicity; minor deformation; small ash emission

Between mid-March and mid-April, the height of the vapor column varied between 300 and 1,000 m, with SO2 content, measured by COSPEC, of 300-1,000 t/d. Rates measured in early March were generally of the order of 500 t/d, down from ~1,000 t/d a month earlier. Ash contents of the plume were low.

Seismicity during the period generally remained similar to the previous month. The number of high-frequency events declined slightly to ~3/day, while low-frequency shocks increased somewhat to an average of 12 daily. Depths of high-frequency events were as much as 8 km (below a datum at 4.7 km altitude), with ~65% of the events deeper than 3 km. Epicenters were dominantly in the S part of the volcano. Around 21 March there was a small seismic crisis with 24 low-frequency and 13 high-frequency events that were associated with a small ash emission. On 6 and 7 April, two significant low-frequency events were registered, but they were not accompanied by any other activity. Colombian geologists noted that regional earthquakes could have some influence on the increase in low-frequency seismicity.

During the second week in April, data from EDM lines revealed slight deflation (of the order of 1 mm/day) at stations on the N and E sectors of the volcano. In contrast, a station in the SW sector (CISNE) indicated an inflation of ~3 mm daily during the same period. Dry and electronic tilt measurements have not shown significant changes. Rates of movement of ice near the summit have slowed since January to less than half the December rates.

Information Contacts: A. Núñez and F. Muñoz, Observatorio Vulcanológico de Colombia (INGEOMINAS-UNICALDAS), Manizales.


May 1986 (SEAN 11:05) Citation IconCite this Report

Six weeks of harmonic tremor; increased SO2; light ashfalls

Activity during 15 April-15 May. A substantial increase in seismic activity began in late April and was continuing in mid-May. Seismic records suggested that a minor ash emission occurred on 4 May, and ashfalls were reported within 3 km of the summit.

Seismicity remained at moderate levels until 20 April, when there was a swarm of 37 high-frequency events, with maximum magnitudes of 2.0. On 24 April a swarm of 24 low-frequency events was apparently accompanied by an increase in the SO2 content of the vapor column that emerges from Arenas Crater. No other eruptive changes were reported.

Harmonic tremor began on 4 May at 1300. A seismic signal with a maximum amplitude of 8 mm started at 1445 and lasted ~4 minutes, apparently marking a brief ash emission that was not directly observed. Periods of tremor of variable duration were recorded on 5, 7, 8, 9, 10, and 11 May, the longest ~26 hours, separated by brief quiet intervals. Tremor frequency remained relatively constant (5-6 Hz) but amplitudes varied significantly, reaching a maximum of 20 mm on 4 May between 2243 and 2300. The beginnings and ends of tremor episodes were often gradual, but on some occasions tremor ceased suddenly. On 7 May between 0000 and 0200, a swarm of high-frequency earthquakes was detected. One event had a magnitude of more than 2.0, the largest registered at Ruiz since December 1985.

dry-tilt data showed inflation of between 2 and 15 µrad on three of the four stations, while the fourth, on the NW flank, indicated 37 µrad of deflation. Electronic tilt measurements and EDM lines showed only minor changes.

COSPEC data yielded rates of SO2 emission that varied between 24 and 5,000 t/d. However, a station that measures wind direction and intensity has failed, and the raw COSPEC data can no longer be corrected for those factors.

Activity during 15 May-15 June. Seismic activity . . . remained dominated by harmonic tremor since 4 May. The tremor had a dominant frequency of 5 Hz, but strong components of frequencies as low as 1 Hz have been recorded at times. During a period of weak tremor on 29 May, there was a several-hour swarm of low-frequency events. About 1 day before this swarm, electronic tiltmeters began to show fluctuations, with daily changes of 1.5 µrad and periods of several hours to a few days. The pattern of all deformation measurements (EDM, dry-tilt, electronic tilt, and levelling) was inflationary as of mid-June, although small and irregular (0.4 µrad/day).

After 6 weeks, harmonic tremor fell to the noise level on 14 June and the number of low-frequency events increased again. Five shallow events, with durations of up to 3 minutes, were counted. Poor visibility prevented correlations with crater activity. Tremor resumed during the evening of 16 June and was continuing the next day.

Ash emissions were evident on many days, sometimes depositing thin layers on fresh snow. When winds forced the column down, a sulfur smell was strong as far as several tens of kilometers from the crater. During most of the few overflights permitted by weather conditions, the crater fumaroles again showed distinct behavior, with one emitting ash, the other only vapor. The most recent COSPEC data, collected at the beginning of June, showed an SO2 emission rate of 3,500-5,200 t/d, in contrast to previous weeks in which values fluctuated between 250 and 1,200 t/d. No significant changes to the summit ice cap were observed.

Because of the significant increase in activity, on 12 June the government released orders for permanent evacuation of a zone within 10 km of Arenas Crater (population ~1,700), and strongly recommended that the area within a radius of 10-20 km also be evacuated (population 8,000-10,000).

Information Contacts: H. Meyer (Scientist-in-Charge); E. Parra (Regional Director); A. Núñez, and F. Muñoz, INGEOMINAS, Observatorio Vulcanológico de Colombia, Manizales.


June 1986 (SEAN 11:06) Citation IconCite this Report

Strong seismicity continues; deformation NW of the summit

Activity during 15 June-10 July. "Harmonic tremor, which started on 4 May, still dominated the pattern of seismic activity at Ruiz as of 10 July. Several times, swarm-like single event sequences of mostly low-frequency earthquakes changed the pattern for hours or even days.

"On 5 July the tremor declined almost to background level. At the same time the frequency of events increased sharply, totaling ~300 (minimum 5-second duration) by 10 July at Olleta station (4.2 km W of Arenas Crater), the highest number for a 5-day period since the 13 November eruption. The maximum magnitude was 2.2 and most events were of the low-frequency type.

"A comprehensive analysis of all deformation data (EDM, electronic tilt, dry-tilt, and levelling) now clearly shows asymmetric behavior of the volcanic edifice. Most deformation data have been gathered in the NW sector and the least in the SE sector (where only one electronic tiltmeter is sensing deformation now, apparently with considerable electronic or geologic drift). However, comparison of the data sets suggests strongly that movements are most pronounced in the NW sector, somewhere between the main crater Arenas and the dormant crater La Olleta, on the W flank.

"dry-tilt station Molinos (3.2 km N of Olleta and 5.0 km NW of Arenas) recorded a fluctuating change of several tens of microradians, corresponding to upward movement in a direction E of Olleta (toward the summit) between mid-April and mid-June. There was a general agreement with this sense of deformation at Inderena electronic tiltmeter (1.1 km NE of Molinos dry-tiltmeter). The start of this anomaly corresponds roughly to the reactivation of seismicity (20 April). The deformation at Molinos reversed to downward movement around 17 June, while seismic activity continued.

"A comparison of all EDM lines also reveals that deformation is concentrated in the NW sector (line Arbolito). New EDM lines and dry-tilt stations are now being installed, to allow for more resolution of the deformation pattern.

"Ash emission seemed to be more or less continuous at one of the fumaroles in the crater. Samples of ash, taken from recent falls, were examined under the microscope. No signs of juvenile material were evident. The vapor column, although quite dense, was not seen at heights above 500 m. No correlation has been found yet between the fumarolic activity and the amplitude/period of the harmonic tremor."

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


July 1986 (SEAN 11:07) Citation IconCite this Report

Ash emissions preceded by B-type swarms and shallow events

Activity during 11 July-13 August. "For the first time in the present period of increased activity (since 20 April), strong ash emissions occurred on 20 and 29 July. Harmonic tremor changed its pattern, especially after the prolonged ash emission of 29 July, becoming stronger and changing spectra. Deformation slowed after the 20 July emission. Under the microscope, ash samples from both emissions showed no signs of juvenile origin.

"The first emission, on 20 July at 0600, was short (~2 minutes) and more vigorous, rising to >4 km above Arenas Crater. It also contained a visible amount of vapor. The 29 July emission, detected at 0630, lasted longer. Pulses of ash were observed between 0635 and 0758, but were less vigorous than on 20 July and vapor was not visible. The ash cloud spilled over the crater and down the W flank (over the Farallones). After 0758 the tremor decreased. Ash emission continued, at a lower rate and more steadily, until about noon. Dominant dry-season winds carried ash from both emissions at least 30-40 km to the W, but no change was observed in W flank streams, although the snow was covered with ash.

"Vigorous phases of both emissions were accompanied by strong tremor that partially saturated instruments. The most interesting feature of the seismic activity, however, preceded both ash emissions. Swarms of small B-type events, most visible at Refugio station 3.6 km W of Arenas Crater, started 7-8 hours before the emissions. Attempts to link this station by telemetry have been impeded for several weeks by high levels of gas and lack of accessible shelter in the area. Both emissions were also preceded by shallow seismic events occurring 20-120 minutes in advance.

"Both emissions produced 4-6 Hz tremor. After the 29 July emission, several tens of hours of tremor with a dominant component of 0.6-1.0 Hz were recorded at Recio (4 km SE of Arenas) and less strongly at Olleta (4 km W). Following several days of intermittent tremor, the tremor frequency increased again after 7 August to 4-5 Hz and showed strong variations in amplitude, which could be correlated between the three nearest telemetering stations Rubi (4.6 km N of the crater), Olleta, and Recio.

"During a period of low-amplitude tremor on 8 August, several shallow events and one A-type swarm (>20 events) occurred, followed by ash emission. Ash emissions that were considerably smaller than those of 20 and 29 July were seen 9 and 10 August. Activity declined 11-12 August, but increased again on the morning of the 13th, when alternating emissions of pulsating ash plumes and vapor were observed.

"Deformation started to slow simultaneously with the 20 July emission, but still showed changes reflecting inflation at most stations."

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


August 1986 (SEAN 11:08) Citation IconCite this Report

Stronger deformation; seismicity builds after brief decline

Activity during 13 August-12 September. "No more strong ash emissions occurred after 29 July, although prolonged and weak emissions have been reported. We assume that the record of weak emissions is incomplete due to weather conditions and frequent snowfall.

"After a strong phase until about 20 August, the amplitude of harmonic tremor decreased, but tremor remained continuous and maintained 5 Hz as a dominant frequency. Occurrence of seismic events reached a mimimum 17-23 August, with no events above the tremor level for >40 hours. Seismicity then increased again, reaching a maximum of ~120 events on 9 September. During this maximum, several long-period events were recorded, quite similar to but smaller than those observed before November 1985. About half of the remaining events were of high frequency (A-type) and most of the rest were B-types.

"COSPEC measurements resumed on 15 August. Rates of SO2 emission ranged between 500 and 12,000 t/d, showing some correlation with tremor amplitude.

"The pattern of deformation changed in comparison to all previous months of 1986. By the end of August, most dry-tilt stations began to show fluctuating changes, with amplitudes 2-4 times as large as those observed since December 1985. Cumulative resulting vectors pointed approximately to the summit area."

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


September 1986 (SEAN 11:09) Citation IconCite this Report

Seismicity, deformation, and SO2 emission decline

"After peaking in the first half of September, most indicators of activity have been at lower levels. The seismic event count (120 on 9 September) did not exceed 25 events/day. Long-period events, however, continued to occur at about the same rate as before. The most recent large ones were recorded on 5 October (duration ~35 seconds) and 11 October (~25 seconds). Harmonic tremor continued at intermediate levels, but was less stable in amplitude. Long-period and shallow seismic events tended to occur more frequently during periods of low tremor amplitude. Deformation, as measured by dry and electronic tilt, has diminished. September deformation rates were the highest since 1985, but, similar to dry-tilt data from October-November 1985, recent changes were fluctuating rather than uniform in character. The highest SO2 emission rate during the report period was 7,200 t/d, measured on 18 September. As of 11 October, the rate was 1,000-2,000 t/d. Ashfall has been observed on many days. None of the analyzed samples were of juvenile origin.

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


October 1986 (SEAN 11:10) Citation IconCite this Report

Strong earthquake swarm but weaker tremor

Activity during 11 October-11 November. "A swarm of tectonic earthquakes on 28 October was the major recorded seismic activity for the report period. The swarm lasted 7.5 hours, and included >180 events with durations >= 5 seconds. Maximum magnitude was 2.9. The events were centered ~3 km W of Arenas Crater and 1 km NE of Olleta Crater, at ~5 km below summit level. In comparison, the much smaller swarm that initiated the present period of higher activity on 20 April occurred SE of Arenas Crater, at a shallower depth (~3 km).

"Long-period seismic events were less frequent than during September. Low-frequency seismic events continued at about the same rate and most still appeared to be centered near the SE station (Regio). Since about 6 November the seismic station nearest Arenas Crater (Refugio, 2.8 km to the W) recorded an increase in shallow seismic activity.

"Harmonic tremor was the lowest of any period since 4 May. Several times, the signal declined to background level for hours or days. As of early November, tremor typically lasted for a few hours, often beginning after low-frequency or shallow seismic events then slowly declining. At times, the increase or decrease in signal intensity was not simultaneous at all stations, suggesting that there was more than one tremor source.

"The highest SO2 emission rate, 5,400 t/d, was measured on 31 October during a tremorless period. The average emission rate was ~3,000 t/d. Evidence of ash emission was less than during the previous month.

"After relatively strong fluctuating changes in September, deformation was weaker and less regular. The resultant tilt vectors pointed less consistently to the summit area. Some changes in deformation measurements may have been due to the effects of heavy rainfall."

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


November 1986 (SEAN 11:11) Citation IconCite this Report

High seismicity; temperatures increase in hot springs

"Activity remained at about the same level as . . .11 October-11 November, but showed different character and location. Shallow (non-tectonic) seismic events, which increased at the end of October and early November, were more frequent than during any previous month in 1986. From measurements of station-to station amplitude ratios this high-frequency activity appeared to be W of the volcano. Low-frequency events during earlier months had been centered more to the E, suggesting a possible relationship with tectonic-type swarms in April and late October. During the same period, the frequency of shallow (explosion-type) seismic events increased. Harmonic tremor remained at low levels with occasional increases correlating with increases in shallow seismic activity.

"The crater fumarole generally emitted very small steam plumes, but some plumes reached more than 1 km when wind speeds were low. Hot springs 10 km NW of Arenas Crater showed a decrease in pH and an increase in temperature for the first time since the pre-eruption period of 1985. Ash emission was the lowest since 4 May. COSPEC measurements were infrequent due to poor weather conditions but average SO2 emissions were between 2,000 and 3,000 t/d. The latest measurement, on 10 December, was 1,700 t/d."

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


December 1986 (SEAN 11:12) Citation IconCite this Report

Shallow seismicity; minor ash emission; less SO2

"There was no significant change in the average level and character of activity.

"Shallow B-type events still dominated the seismic activity, remaining as frequent as during the two previous months. A small swarm of tectonic events (A-types) on 22 December, centered SE of the main (Arenas) crater, marked an increase in D-type occurrence, which averages more than 50 events/day. Only a few brief (hours) and low-amplitude episodes of harmonic tremor were recorded. Deformation measurements yielded only minor, fluctuating changes.

"The hot springs NW of the main crater had started to show changes in pH and temperature the previous month, and these values continued to fluctuate. The vapor column remained vigorous, fluctuating in height and intensity, and pulsating. Only a few reports of minor ashfall were received. The rate of SO2 emission (measured by COSPEC) decreased; the average was ~1,400 t/d, the highest values 2,700 t/d. After 2-3 months with very little snowfall, some glaciers were showing signs of strong melting and fracturing.

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


January 1987 (SEAN 12:01) Citation IconCite this Report

Seismicity, tilt, and gas emission remains stable

The activity level fluctuated during the 11 January-11 February report period, but remained similar to the previous 30 days. Shallow, low-frequency seismic events dominated activity but a few long-period events occurred (for the first time since November) during the last 2 weeks of the report period. Larger tectonic and low-frequency events (M > 1.0) occasionally occurred at the SE limit of the active zone, 2-4 km from Arenas Crater. No clearly discernable tremor was recorded.

Electronic tilt was the quietest since the first observations in October 1985 but increased on 7 February. Very small fluctuating changes were seen from dry-tilt measurements until the end of January when small (less than a microradian/week) but consistent deformation began.

COSPEC data indicated that the SO2 emission rate remained fairly stable, averaging 1,400 t/d. However, the H2O content in the column again seemed to have increased significantly. There was no evidence of ash emissions.

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


February 1987 (SEAN 12:02) Citation IconCite this Report

Inflation precedes small ash eruptions

No major change in activity level has been observed during the 11 February-11 March report period but a correlation between measured data and crater activity was established. Most dry-tiltmeters began to show stronger variations (maximum amplitude 10 µrad) by the end of January. Electronic tiltmeter 'Inderena' (5.9 km NW of Arenas Crater) began to record inflation after 7 February that increased between 15 and 19 February to 0.5 µrad/day, the strongest anomaly since late September 1986.

After deformation flattened out on 20 February, several small ash emissions occurred 20-25 February. COSPEC values increased to a maximum of 4,900 t/d during this period but there was no recognizable correlation with the seismicity. The number of shallow, small-magnitude B-type events remained about the same since December 1986. Only harmonic tremor increased between 20 and 25 February. Its shallow source was evident from amplitude relations.

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


March 1987 (SEAN 12:03) Citation IconCite this Report

More, shallower seismicity; deformation; gas kills animals

Seismicity, particularly shallow B-type activity, began to decline slightly on 20 March. In the following weeks, long-period events were more frequent, and high-frequency (A-type) events shifted N towards Arenas Crater and became more shallow. About 1-2 events were recorded daily. Tremor was weak but more continuous than during the previous report period.

Deformation, consisting mainly of NW-SE fluctuations, remained at slightly elevated levels, comparable to September/October 1986. Changes were recorded more strongly on lower-altitude stations. From 4-10 April an electronic tiltmeter (Inderena) 5.9 km NW of Arenas Crater recorded 2-3 µrad/day of eastward inflationary movement. Other tiltmeters recorded only minor amounts of inflation.

SO2 emission, measured by COSPEC, declined to an average of 620 t/d (maximum 1,060 t/d on 27 March). There have been no reports of ash emission since late February. About 3 April, [hundreds to thousands of] dead [migratory] birds and small mammals were found 10-20 km from the crater, mostly to the NE (downwind). Preliminary analyses showed sulfur emission rates and rain acidity to be well below peak values, but biological analyses of animals revealed signs of carbon monoxide effects [see also 12:05].

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


April 1987 (SEAN 12:04) Citation IconCite this Report

Continued moderate-high seismicity; acid rain kills birds

Seismicity continued at moderately high levels in April; 920 low-frequency and 172 high-frequency events were registered. The tremor signal has remained weak compared to 1986. Seismic activity peaked on 16 and 17 April when 80-90 events were recorded each day [see also 12:05]. One week later, deformation measurements showed changes of as much as 5 µrad/day. SO2 levels, measured by COSPEC, averaged 1,000-1,200 t/d.

Information Contacts: E. Parra, INGEOMINAS, Manizales.


May 1987 (SEAN 12:05) Citation IconCite this Report

Ash emission; fine ash to 50 km W

Activity increased again after several months at low to moderate levels. Swarms of high-frequency earthquakes occurred 21 and 22 May, 3-6 km SW of the active crater (Arenas), at an average depth of ~6 km. 125 events were registered above the count threshold, with a maximum magnitude of 2.0. Low-frequency events (B-type) remained stable. Slightly shallower seismic events were recorded following the swarm, similar to observations after the previous swarm (16 April).

Harmonic tremor was generally absent or just above background, but increased suddenly on 9 June at 2007 to levels close to saturation, similar to the tremor activity recorded for months after the 4 May 1986 ash emission. Ashfall was first reported more than an hour later at 2115 (at Cerro Gualí) but visibility was poor, so the onsets of ash emission from Arenas Crater and tremor may have been simultaneous. Fine ash fell 40-50 km to the W, and by the afternoon of 10 June, 3.5 cm had accumulated 6 km W of the volcano. Initial microscopic inspection indicated no fresh glass in the ash. A helicopter overflight 11 hours after activity began revealed no impact craters or other evidence of ejection of large tephra. Minor melting of summit-area ice caused small increases in the flows of W flank rivers, but no evacuations were necessary. No pyroclastic flows were observed. After the first day of activity, ash emission declined irregularly, and had ended four days later. Tremor declined steadily, with no apparent correlation between its amplitude and observed fluctuations in ash emission.

COSPEC data showed that SO2 emission rates increased slightly for a few days after the May earthquake swarm, to a maximum of 2,300 t/d. Weather clouds and ash hampered COSPEC measurements during the ash emission period. Values ranged from 850 t/d on the first day of the activity to 3,600 t/d the second and fifth days, but because of masking effects of the ash, these are minimum values.

Deformation measurements did not yield values that correlated clearly between stations or with seismic and eruptive activity. One dry-tilt station N of the summit showed a change of 12 µrad just before the May seismic swarm, and a SE-flank electronic tilt station recorded ~11 µrad of inflation in the week before the swarm.

The deaths of birds mentioned in 12:03 [and originally in 12:04] were observed 2-4 April, 25-26 km NE of Arenas Crater (in Casabianca, Villahermosa, and Herveo) and at 4,200 m altitude 8 km S of the crater (at Laguna Verde). An estimated 2,000 birds died in that 3-day period, during which clouds and rain were almost continuous, and residents reported a constant rotten egg odor. Most of the affected birds, generally migrants en route to North America, fell to the ground between the hours of 0300 and 0400. Some were still alive but had evident breathing problems, and some survived several days before dying. Seventeen birds were taken to the Instituto Colombiano de Agricultura for study. All had lung damage, and autopsies suggested that they died from carbon monoxide poisoning. There were no reports of ill effects to humans. Similar bird mortalities were reported at the end of the 19th century during a period of increased fumarolic activity at Ruiz.

Information Contacts: H. Meyer, INGEOMINAS, Manizales.


June 1987 (SEAN 12:06) Citation IconCite this Report

Peak 1987 SO2 emission; seismicity declines

Low- and high-frequency earthquakes continued at moderate levels after 16 June. Tremor fluctuated but remained weak, reaching a maximum amplitude of 2 mm at the Olleta reference station (4 km W of Arenas crater). The rate of SO2 emission measured by COSPEC reached 5,640 t/d on 17 June, the highest value of 1987. Emission rates then declined to an average of 1,000 t/d for the rest of the month. Little change in deformation was measured.

Information Contacts: A. Acevedo, INGEOMINAS, Manizales.


July 1987 (SEAN 12:07) Citation IconCite this Report

Seismicity continues; minor inflation

No new eruptive activity has been reported since the 4-day ash eruption that started 9 June. Seismic activity declined after the eruption and has continued at moderate levels since mid-June. During July, 162 high-frequency, 445 low-frequency, and 68 shallow explosion events were recorded. The actual number of events was obscured by tremor that filled the records on some days. Major high-frequency swarms occurred on 17 July (57 events) and the night of 31 July-1 August (120 events). Strong tremor occurred 14-16 and 23-26 July, with peak-to-peak amplitudes of 9-10 mm. Additional earthquake swarms were recorded on 6 August (high-frequency) and 9 August (low-frequency).

Deformation measurements were more stable in July than in June. On 7 July, all stations showed inflationary trends, with a maximum value of 10 µrad. The SO2 content of the plume as measured by COSPEC decreased to the lowest values yet measured, 170 t/d.

Information Contacts: E. Parra, INGEOMINAS, Manizales.


September 1987 (SEAN 12:09) Citation IconCite this Report

Small ash emission; strong seismicity continues

August data are from the Boletín Informativo, published by the Observatorio Vulcanológico de Colombia. Energy release from the high-frequency earthquake swarm of 31 July-1 August was the fourth largest since the seismic crisis of November-December 1985. Maximum magnitude of swarm events was 2.2. The number of both high- and low-frequency events increased slightly in August, to 299 and 585 from 162 and 445 in July, but shallow explosion events declined from 68 in July to 50 in August. All of the August high-frequency events were centered in a zone 3-6 km S-SE of the crater, about 2/3 with focal depths 2.5-4 km below the summit. The remainder were shallower. Swarm events had epicenters 3.5 km S of the crater with similar depth distributions. After the swarm, seismic energy release accumulated in August at a rate similar to that of July. Tremor amplitude and period varied considerably, but energy was generally lower during the month. Highest amplitudes were recorded on 17 August, associated with an apparent minor ash emission. A small amount of ash was also visible in the plume at about 1000 on 22 August; poor weather prevented observations during other periods of increased tremor. Measurements of rates of SO2 emission were hampered by large variations in wind direction and velocity; values varied from ~450 to 2,600 t/d. Deformation measurements showed no major changes.

A small ash emission on 10 September dispersed ash 4-5 km SW. Seismic activity associated with the ash emission was the strongest of the month and saturated the records of stations close to the crater for more than 10 minutes. A strong deformation change was recorded by the Refugio station (3.6 km W of Arenas Crater) a few minutes before the ash emission, but was not detected at other deformation stations.

Seismic activity in September was characterized by an oscillatory tremor signal that fluctuated between high and moderate levels. Three more seismic episodes similar to that of 10 September occurred during the month but did not saturate instruments. A swarm of high-frequency events occurred 25 September. September totals were 154 high-frequency and 533 low-frequency events. Deformation changes were minor. The rate of SO2 emission grew to an average of 2,000 t/d, compared to the year's average of 1,000 t/d.

Information Contacts: E. Parra and A. Acevedo, INGEOMINAS, Manizales.


October 1987 (SEAN 12:10) Citation IconCite this Report

Small ash emission; seismicity; highest SO2 of 1987

A small ash emission occurred on 25 October at 0946. Seismicity had begun to migrate toward the crater in mid-October, and the activity was accompanied by a sudden increase in harmonic tremor that lasted for ~15 minutes. Tremor was otherwise very weak during October. During the month, 301 high-frequency, 593 low-frequency, and 125 shallow (explosion) events were recorded, up from 154, 533, and 15 in September. Changes in deformation remained small to moderate. Rates of SO2 emission were higher than in any previous month of 1987, with median values of close to 2,000 t/d.

Information Contacts: E. Parra, INGEOMINAS, Manizales.


November 1987 (SEAN 12:11) Citation IconCite this Report

Seismicity increases; SO2 emission remains high

Since a strong seismic crisis in July, seismicity has remained at elevated levels, . . . . Minor ash emission has occasionally been seen since August. During November, high- and low-frequency earthquake activity increased. The number of high-frequency events rose slightly, to 330 . . ., and low-frequency events increased to 933 . . ., but energy release was relatively low. Shallow (explosion) seismicity declined to 111 recorded shocks. . . . No ash was emitted and deformation measurements showed low to moderate changes. The average rate of SO2 emission was ~1,500 t/d. Occasional minor ash emission has occurred since . . .ash emission in June.

Information Contacts: E. Parra, INGEOMINAS, Manizales.


January 1988 (SEAN 13:01) Citation IconCite this Report

Continued strong seismicity; slight SO2 increase

Seismic activity continued at high levels in December and January. During December, 423 high-frequency and 714 low-frequency earthquakes were recorded; a swarm of 101 high-frequency earthquakes occurred on the 11th. In January, low-frequency earthquakes increased to 1540 while high-frequency events decreased to 280. Shallow earthquakes were steady, with 62 recorded in December and 65 in January. The amount of seismic energy released increased slightly. Tremor signal was low and no ash emission was detected.

COSPEC measurements of SO2 ranged from 450 to 3,000 t/d at the end of January, when a slight increase in SO2 content was recorded in the plume. Deformation measurements that month showed minor to moderate changes. Most (70%) of dry-tilt changes were <8 µrad; Molinos Station (on the NW flank) continued to show instability with tilt variations reaching 15 µrad. The telemetric tilt data did not show any significant changes.

Information Contacts: M. Calvache, A. Nieto, and C. Carvajal, INGEOMINAS, Manizales.


March 1988 (SEAN 13:03) Citation IconCite this Report

Ash emission follows earthquake swarm

February data are from the Boletín Informativo, published monthly by the Observatorio Vulcanológico de Colombia. The number of high-frequency events increased significantly in the second half of February, totaling 707 for the month, as compared to 280 in January (figure 7). Hypocenters, at 1-5 km depth, were clustered in three zones: near Nevado de Santa Isabel (~10 km SW of the active Arenas Crater) on 10 February; to the NE at Nevado del Cisne (~6 km SW of Arenas) on 21 February; and an especially active sequence at Arenas 12-22 February. Low-frequency events declined slightly to 1,362, from 1,540 the previous month, and did not parallel the late February increase in high-frequency shocks. A few more shallow earthquakes were recorded in February (74) than in January (65). Tremor remained at minimal amplitudes until the end of the month, when brief episodes of long-period (0.7-1 second) tremor reached maximum peak-to-peak amplitudes of 7 mm. The rate of SO2 emission measured by COSPEC ranged from ~1,000 to 3,000 t/d and averaged 1,843 t/d. Deformation changes, monitored by dry and electronic tilt and electronic distance measurements, appeared to be small.

Figure (see Caption) Figure 7. Daily number of recorded earthquakes at Ruiz, 20 July 1985-31 March 1988. Larger eruptive episodes are labeled. Courtesy of INGEOMINAS.

Ash emission began on 22 March at 0935, the day after a long-period earthquake swarm. Activity briefly became more vigorous on 25 March before declining that night. Eruption column heights did not exceed 2-3 km and were usually <1 km. Ash fell to the NW, where 2 mm accumulated in Manizales (~30 km from the crater) and 15 mm were deposited closer to the volcano. No fresh magma was observed in the ash. Tremor increased rapidly 20 minutes after the onset of ash emission, remained at a high level for the next six days, then decreased slowly before reaching a minimum on 29 March. Civil Defense officials declared an orange alert and ordered the evacuation of the area within 10 km of the crater. Several hundred people left the hazard zone, but the press reported that at least 1,000 chose to remain. The warning was reduced to a yellow alert on 27 March, signaling that the activity was not imminently dangerous.

The number of recorded seismic events was 220% higher in March than in February. Most events were centered in two zones, one beneath the active Arenas crater (sometimes called Cumanday) and the other 3.5 km from the crater on the SW flank. Depths ranged from 0.15 to 5 km. Maximum daily seismic energy release was 124 x 106 ergs (figure 8). Rates of SO2 emission reached 7,700 t/d (figure 9), the highest measured since September 1986. The average daily rate in March was 2,800 t/d (figure 10) but values declined after ash emission began, a pattern similar to that associated with the June and October 1987 ash emissions. No significant changes were observed in deformation data.

Figure (see Caption) Figure 8. Seismic energy release at Ruiz, in 106 ergs, 20 July 1985-31 March 1988. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 9. Daily SO2 flux at Ruiz, measured by COSPEC in March 1988. Dashed lines mark the 22-25 March ash emission. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 10. Average daily SO2 flux for each month, July 1986-March 1988. Courtesy of INGEOMINAS.

Information Contacts: R. Mendez, O. Bohorquez, A. Nieto, and M. Calvache, INGEOMINAS, Manizales; UPI; AP.


April 1988 (SEAN 13:04) Citation IconCite this Report

More frequent ash emission; increased seismicity

Small ash emission episodes that lasted ~2-5 minutes were frequent in the second half of April, as seismicity increased significantly. Ash fell ~10 km NW and SW of the summit crater, troubling cattle on nearby farms.

The number of high-frequency events increased significantly during the last six days of April, reaching a total of 2,683 for the month. The number of low-frequency shocks also increased in April, totaling 2,303. Epicenters were dominantly aligned NE-SW in two principal zones; one beneath the summit (Arenas Crater) at 1-5 km depth, the other 3 km to the SW (between Arenas and Nevado del Cisne) at 3-5 km depth. Maximum daily seismic energy release was 2.04 x 108 ergs on 29 April (figure 11), when 338 high-frequency and 247 low-frequency events were recorded. Pulses of tremor that began suddenly and reached high amplitude occurred almost daily, but declined very quickly (after 2-5 minutes). Several of the tremor pulses were associated with small emissions of ash that fell near the crater. SO2, measured by COSPEC, declined at the beginning of April then increased to an average of 3,000 t/d (figure 12), very close to March values. Deformation data continued to show no significant changes.

Figure (see Caption) Figure 11. Daily seismic energy release (in 106 ergs) at Ruiz, April 1988. Courtesy of the Observatorio Vulcanológico de Colombia.
Figure (see Caption) Figure 12. Rate of SO2 emission (in 103 t/d) measured by COSPEC at Ruiz, April 1988. Courtesy of the Observatorio Vulcanológico de Colombia.

Information Contacts: A. Nieto, A. Acevedo, and E. Parra, INGEOMINAS, Manizales.


May 1988 (SEAN 13:05) Citation IconCite this Report

Small ash ejections; tremor; strong SO2 emission

In May, minor ash emissions were associated with pulses of high-amplitude tremor that lasted a few minutes at the beginning of the month, and had longer durations after 21 May. Seismicity decreased in May but remained at high levels. The number of high-frequency events declined from 2,683 in April to 1624 in May, and low-frequency shocks dropped from 2,303 to 1,902. Hypocenters were concentrated S and SW of Arenas Crater at depths of 1-5 km. The maximum daily energy release (1.2 x 108 ergs) occurred 31 May when 42 high-frequency and 306 low-frequency earthquakes were registered. Relatively good weather and consistent winds (1-5 m/s velocity) allowed SO2 measurements by COSPEC on 13 days. The maximum measured rate of SO2 emission was 5,190 t/d on 13 May, with a monthly average of 2,435 t/d. Most of the highest SO2 values corresponded with ash emissions and increases in the tremor signal. No significant changes were registered by electronic or dry-tilt.

Information Contacts: M. Calvache, F. Gil, and C. Carvajal, INGEOMINAS, Manizales.


June 1988 (SEAN 13:06) Citation IconCite this Report

Daily ash emissions; continued strong seismicity

Several small brief ash emissions occurred daily during June, all associated with increased harmonic tremor. Ash fell to the W, usually <10 km from the vent. High-frequency earthquakes increased to 2,362 in June, while low-frequency events decreased to 1,758. A significant high-frequency swarm (273 events) occurred on 15 June (figure 13). There were 212 shallow events in June and daily energy release tended to increase, continuing a trend that began in late 1987 (figure 14). Average SO2 content was 1,700 t/d (measured by COSPEC), a decrease from May's average of 2,435 t/d. Deformation measurements showed no significant changes.

Figure (see Caption) Figure 13. Daily number of recorded seismic events of high (solid line) and low frequency (dashed line), June 1988. Courtesy of the Observatorio Vulcanológico de Colombia.
Figure (see Caption) Figure 14. Cumulative seismic energy release at Ruiz, June 1985-February 1988. The solid line sums high- and low-frequency energy release, indicated by dashed and dotted lines, respectively. Courtesy of the Observatorio Vulcanológico de Colombia.

Information Contacts: E. Parra, R. Mendez, and F. Muñoz, INGEOMINAS, Manizales.


July 1988 (SEAN 13:07) Citation IconCite this Report

SO2 emission and seismicity increase

Several ash emissions in July deposited 2 mm of lithic ash as far as 5 km from the crater. COSPEC measurements indicated an increase in SO2 emission during the second half of the month (figure 15) with highest contents recorded on 18 July (5,560 t/d) and on 26 July (4,850 t/d).

Figure (see Caption) Figure 15. July 1988 SO2 emissions from Ruiz, as measured by COSPEC.

Seismic activity also increased in July. The highest energy earthquake swarm in July occurred at the beginning of the month near Nevado Santa Isabel, ~5 km SW of the volcano. At month's end, most activity occurred 2 km SW of Arenas crater at depths of 0.5-5 km. Short-duration tremor was also measured. Only minor deformation changes were detected.

Information Contacts: M. Calvache, J. Patiño, and C. Carvajal, INGEOMINAS, Manizales.


August 1988 (SEAN 13:08) Citation IconCite this Report

Small ash emissions; seismicity increases slightly

Small, brief ash emissions similar to those of July continued during August. Seismic energy release and the number of low-frequency earthquakes increased slightly (figure 16). Some clusters of high-frequency events occurred, especially ~2 km NE and SW and 4 km SE of the crater. No significant deformation was recorded. SO2 emissions (figure 17) averaged 2,139 t/d.

Figure (see Caption) Figure 16. Number of seismic events (high- and low-frequency)/day, June 1985-mid-September 1988, courtesy of the Observatorio Vulcanológico de Colombia. The 11 September and 13 November 1985 eruptions are indicated by arrows.
Figure (see Caption) Figure 17. Daily SO2 flux as measured by COSPEC, mid 1986-early September 1988. Courtesy of the Observatorio Vulcanológico de Colombia.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


September 1988 (SEAN 13:09) Citation IconCite this Report

Small ash emissions; continued strong seismicity

The number of high- and low-frequency seismic events increased in September. Although seismic energy release declined slightly from August, energy release has risen substantially during 1988 (figure 18). Most September seismicity was centered ~4 km SE of the crater at depths of 0.5-7 km. A high-frequency earthquake swarm 2 km SE of the crater occurred 18 September. Brief increases in tremor were associated with small ash emissions. Tremor amplitude was at one of the year's highest levels. SO2 emissions averaged 2,870, up from 2,139 t/d in August (figure 19). No significant deformation was recorded.

Figure (see Caption) Figure 18. Seismic energy release at Ruiz, June 1985-September 1988. Periods of tephra emission are labeled. Courtesy of the Observatorio Vulcanológico de Colombia.
Figure (see Caption) Figure 19. Daily SO2 flux as measured by COSPEC at Ruiz, mid-1986 to September 1988. Courtesy of the Observatorio Vulcanológico de Colombia.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


October 1988 (SEAN 13:10) Citation IconCite this Report

Minor ash emission and continued vigorous seismicity

The number of earthquakes and seismic energy release remained at high levels during October, continuing the pattern of vigorous seismicity that began to build in late 1987. Tremor amplitude declined slightly. Fluctuations in tremor amplitude were associated with small explosions that briefly emitted ash. A swarm of 212 high-frequency events was recorded 1 October from 1,410 to 1,450. The month's two strongest shocks (M 2.3) occurred on the 9th and 12th. Several of the locatable events were scattered SE of the volcano, while others were centered near the crater at depths of 1-4 km (figure 20). No significant deformation was recorded.

Figure (see Caption) Figure 20. Epicenters of 49 seismic events at Ruiz, October 1988. Courtesy of the Observatorio Vulcanológico de Colombia.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


November 1988 (SEAN 13:11) Citation IconCite this Report

Seismic energy release remains high

Energy released in November by high- and low-frequency earthquakes and volcanic tremor remained similar to October values. A tremor episode on 23 November was associated with fumarolic activity and a brief landslide in the canyon of the Río Azufrado, 2 km NE of the crater (figure 21).

Figure (see Caption) Figure 21. Epicenters of high-frequency earthquakes, November 1988, and the position of the Palestina Fault. Courtesy of the Observatorio Vulcanológico de Colombia.

Although the tremor episode lasted only a few minutes, it produced one of the largest displacements of the energy release curve since 1986. A slight increase in seismicity followed for the next few hours. The month's main high-frequency activity was centered parallel to the regional Palestina Fault, occurring in two clusters. Depths were between 0.5 and 6 km. No significant deformation was measured during the month.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


December 1988 (SEAN 13:12) Citation IconCite this Report

High-frequency seismicity drops; energy release still high

The number and energy release of high-frequency seismic events at Ruiz continued to decline in December, while low-frequency seismicity was similar to previous months (figure 22). Total seismic energy release remained substantially elevated (figure 23). There were two main clusters of high-frequency events, one roughly 4 km E of the crater at ~2.5 km depth, the second 3 km SW of the volcano at ~2 km depth. Brief increases in tremor intensity occurred more often in December, but their energy was low. No significant deformation was measured during the month. The rate of SO2 emission averaged ~1,220 t/d.

Figure (see Caption) Figure 22. Number of seismic events/month at Ruiz (left) and monthly seismic energy release (right) for high-frequency (top) and low-frequency events (bottom), January-December 1988. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 23. Daily seismic energy release at Ruiz, July 1985-December 1988. Courtesy of INGEOMINAS.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


January 1989 (SEAN 14:01) Citation IconCite this Report

Seismic energy and number of event increase

During January, total seismic energy release increased (figure 24a), as did the number of low- and high-frequency events (figure 24b). Most of the high-frequency seismicity was centered in an elongate NW-SE zone between Arenas Crater and Nevado del Cisne (figure 25). Focal depths generally ranged from 0.5 to 4.5 km. Swarms of long-period events occurred on the 17th and 29th, but their energy release was relatively low. Brief increases in the intensity of shallow tremor were usually associated with small ash emissions. A different type of tremor occurred 2-3 January; with a monochromatic signal, a dominant period of 0.35-0.45 seconds, and low energy. During the month, deformation did not exceed 10 µrad except at Molinas station (4 km NW of Arenas crater), which was affected by rainfall.

Figure (see Caption) Figure 24. Cumulative seismic energy release at Ruiz, June 1985-January 1989.
Figure (see Caption) Figure 25. Locations of high-frequency events at Ruiz, January 1989.

Information Contacts: C. Carvajal and F. Muñoz, INGEOMINAS, Manizales.


February 1989 (SEAN 14:02) Citation IconCite this Report

Seismic energy release increases; strong SO2 emission

Daily seismic energy release showed a large increase in February, with the highest telemetric reading since monitoring began in 1985. The number of seismic events was similar to recent months. Long-period and high-frequency events dominated the seismicity. Tremor generally remained at lower levels, with brief pulses of high-amplitude, low-energy tremor.

Deformation changes (measured by dry-tilt and a short level-line) were generally only small to moderate. Electronic distance measurements were stable at the Refugio and Recio stations (~1.1 and 2.2 km from the summit, respectively). Nine SO2 measurments were made by COSPEC during the month. One reading (on the 9th) showed an emission rate of 8,949 t/d. Mean rates in December and January were 1,220 and 1,800 t/d.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


March 1989 (SEAN 14:03) Citation IconCite this Report

Small ash emissions; seismic energy release decreases

Seismic energy and the number of high-frequency events decreased during March continuing a general long-term decline. Short pulses (averaging 5 minutes) of low-energy tremor with periods of ~0.25-0.30 seconds were associated with small ash emissions. Dry and electronic tilt and short leveling vectors showed little change. SO2 emissions measured by COSPEC varied from 900 to 4,500 t/d with a monthly average of 1,921 t/d (see figure 26). Emissions were blown SE.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


April 1989 (SEAN 14:04) Citation IconCite this Report

Seismicity decreases

Seismic activity (high- and low-frequency earthquakes, long-period events, and tremor) significantly decreased in April, continuing a 2-month trend. SO2 emissions measured by COSPEC varied between 700 and 3,700 t/d with a monthly average of 1,800 t/d (figure 26). No significant changes in deformation were measured.

Figure (see Caption) Figure 26. Rates of SO2 emission measured by COSPEC at Ruiz, July 1986-April 1989. Courtesy of the Observatorio Vulcanológico de Colombia.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


May 1989 (SEAN 14:05) Citation IconCite this Report

High-energy seismic swarm

A swarm of more than 500 high-frequency events on 13-14 May had the second highest energy release since telemetric monitoring began in 1985. Seismic energy release increased 3.5x during the swarm, centered <2 km below Arenas crater (figure 27). Brief pulses of low-energy tremor and a small number of long-period events were also recorded during the month. Deformation (dry and electronic tilt) was low. SO2 emissions continued to decrease, to an average of 1,046 t/d in May.

Figure (see Caption) Figure 27. Epicenters (left) and cross sections showing depths (right) of 44 seismic events at Ruiz, May 1989. Courtesy of the Observatorio Vulcanológico de Colombia.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


June 1989 (SEAN 14:06) Citation IconCite this Report

Sharp increase in seismicity precedes ash emission

Seismic energy release has been at increased levels since about February 1988. A sharp increase in seismicity began on 24 June 1989 with a felt earthquake (M 3.1) in Arenas crater. The next day, a shallow swarm of high-frequency events (also in Arenas crater) began at 1130 and continued for 1 hour. From 0100 to 1100 on the 26th, another high-frequency swarm was centered at 4 km depth, 3 km W and SW of Olleta crater (Olleta is roughly 5 km W of Arenas crater). Late that evening, a shallow high-frequency swarm began in Arenas crater, followed by strong tremor associated with a small ash emission that deposited 1 mm of ash, 4 km from the crater. The press reported that the civil aeronautics board issued a warning to airline pilots to avoid a 60-km area around the volcano. Tremor gradually diminished, disappearing on 28 June. SO2 emission was moderate during June. Dry and electronic tilt did not show significant changes. As of 10 July, a yellow alert remained in effect for population within a 10-km radius of the volcano.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales; Reuters.


July 1989 (SEAN 14:07) Citation IconCite this Report

Seismicity decreases; new summit depression

After a sharp increase in seismicity on 24 June and a small ash emission 2 days later, seismicity gradually decreased in late June. High- and low-frequency events stabilized at 200-300/day by the end of the month (figure 28), and tremor was almost absent. A depression, 150-200 m in diameter and 80 m deep, apparently formed on 26 June ~50-100 m SW of the principal (Arenas) crater. It probably developed because of high-pressure gas emission and destabilization of the walls of Arenas crater.

Figure (see Caption) Figure 28. Daily number of high- and low-frequency events at Ruiz, July 1989. Courtesy of the the Observatorio Vulcanológico de Colombia.

Deformation measurements showed no significant changes in July. SO2 flux averaged 1,200 t/d, a slight increase from May (1,046 t/d) and June.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


August 1989 (SEAN 14:08) Citation IconCite this Report

Phreatomagmatic eruption; mudflow destroys bridge

Increased seismicity since mid-August was followed on 1 September by a summit phreatomagmatic eruption that deposited tephra NE of the crater and generated a damaging mudflow.

Vigorous earthquake activity was recorded during August, with numerous A-and B-type events, continuing a trend of increased seismicity that began about February 1988. The month's strongest high-frequency seismic energy release was on 19 August, from a swarm of events centered S of Arenas Crater (figure 29), the main vent of the fatal 1985 eruption. The rate of SO2 emission generally increased in August, oscillating between 416 and 3,800 t/d, for an average of 1,762 t/d (figure 30). Little change was noted in August dry-tilt data and no major changes were detected by electronic tilt instruments. However, the N-S component of the Refugio tilt station (2.3 km WNW of Arenas Crater) has shown a gradual inflationary trend since May 1987 that totaled ~64 µrad by the end of August 1989; the E-W component has registered only minor fluctuations (figure 31).

Figure (see Caption) Figure 29. Epicenters of 35 high-frequency earthquakes near Ruiz, August 1989. Courtesy of the Observatorio Vulcanológico de Colombia.
Figure (see Caption) Figure 30. Monthly means of rates of SO2 emission measured by COSPEC at Ruiz, July 1986-August 1989. Courtesy of the Observatorio Vulcanológico de Colombia.
Figure (see Caption) Figure 31. N-S (top) and E-W (bottom) components of electronic tilt recorded at the Refugio station, March 1987-August 1989. Courtesy of the Observatorio Vulcanológico de Colombia.

Long-period earthquakes increased sharply in the week before the eruption. Tremor (3 mm peak to peak) began late 30 August, associated with ash emission, and ash was emitted again the next day. COSPEC SO2 data provided no obvious short-term warning, with measurements ~18 hours before the eruption yielding values of roughly 2,500 t/d. The day before the eruption, increasing high-frequency seismicity was centered in two zones, NW and just S of Arenas Crater. Staff from the Observatorio Vulcanológico de Colombia met with government officials on 31 August to express concern about the possibility of an eruption.

The phreatomagmatic eruption began at about 0215 on 1 September as seismicity increased. Witnesses saw incandescence in the crater and forest guards reported the fall of bean-sized pumice. Tremor began to increase about 0240, and by 0330 stations more than 10 km from the crater were saturated; 40 cm2 of reduced displacement were recorded during the most vigorous activity. The exact timing of cessation of activity was uncertain, but the eruption had ended by 0900. Pumice and lithic fragments were deposited along a sector from N30°W to N80°W, toward the Pacific Ocean (figure 32). The maximum measured tephra thickness was 5 cm (at Inderena) 5 km N60°W from the crater. The tephra deposit was 2 cm thick in Manizales (~30 km from the crater), composed of lithic fragments, pumice, and crystals of plagioclase, quartz, ferromagnesian components, and biotite, covered by a layer of fine dust. The activity generated a lahar, rich in large (>2 m) andesitic clasts, with coarse sand and sporadic pumice fragments, that advanced 7 km NE down the Azufrado river valley and destroyed a bridge along the Manizales-Murillo road. At the bridge site, the lahar was 5 m thick and 20 m wide.

Figure (see Caption) Figure 32. Preliminary isopach map of the 1 September 1989 eruption. Courtesy of the Observatorio Vulcanológico de Colombia.

The Nimbus-7 satellite's TOMS showed little or no enhancement in SO2 values as it gathered data over the Ruiz area at about local noon on 1 and 2 September. Heavy weather clouds obscured the area, and no plume was detected on weather satellite images.

The Observatorio Vulcanológico de Colombia and the Comité Regional de Emergencia declared a red alert at 0450 and triggered sirens along the principal rivers. Evacuation began from 16 communities (total population <5,000) within 10 km of the crater. As eruptive and seismic activity had declined, the alert status was downgraded to orange at about 1500 and residents were allowed to return to their homes.

The next morning, the vigorous 200-300-m gas plume that was emerging from the summit did not appear to contain any ash. Rates of SO2 emission measured by COSPEC were roughly 2,500-3,500 t/d the day after the eruption, and had risen to 6,000 t/d on 3 September; similar increases have been observed after previous eruptive episodes. The pH of hot springs 7 km NNE and 11 km NW of the crater (at Aguas Calientes and Hotel Termales) had dropped from previous values of 1.2-1.5 to 0.84 and 0.94, but temperatures remained unchanged. Changes in temperature, pH, and sulfur/chlorine ratios had been detected at the same hot springs in late 1986. A M 3.3 earthquake centered under the crater occurred on 5 September at 1845. This event was felt and subterranean noises were heard in the 10-km evacuation area. As of 15 September, no additional strong eruptive activity had occurred. Strong seismicity was continuous, dominated by high-frequency earthquakes centered 6 km W of Arenas Crater at 4-6 km depth. Some of the events have been felt near the volcano.

Information Contacts: C. Carvajal, F. Muñoz, and A. Nieto, INGEOMINAS, Manizales; S. Williams, Louisiana State Univ; N. Banks, CVO; S. Doiron, GSFC; J. Smith, AID/OFDA, Bogotá.


September 1989 (SEAN 14:09) Citation IconCite this Report

Small ash ejections; continued strong seismicity

Tephra ejections continued in September, with ashfalls reported on the 2nd, 3rd, 11th, 12th, 14th, and 17th. SO2 flux averaged 2,625 t/d, with 14 measurements ranging from 218-6,384 t/d (figure 33). Similar increases have followed previous eruptive episodes.

Figure (see Caption) Figure 33. Daily SO2 emissions measured by COSPEC at Ruiz, 1 January-28 September 1989. Courtesy of the Observatorio Vulcanológico de Colombia.

Although the number of A-type events increased in September, the number of B-type shocks decreased from August values. Most September epicenters fell along a roughly NE-SW trend (figure 34). Several events were felt on the volcano. Seismic energy release was highest on 14 September when a swarm of A-type events occurred, centered on the W part of the summit. dry-tilt measurements showed deflation, while electronic tilt measurements showed no significant changes.

Figure (see Caption) Figure 34. Epicenters of 97 high-frequency earthquakes near Ruiz in September 1989. Courtesy of the Observatorio Vulcanológico de Colombia.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


October 1989 (SEAN 14:10) Citation IconCite this Report

Seismic energy release declines

In October, seismic energy release and the number of high- and low-frequency events decreased to the lowest level since early 1988 (figure 35). High-frequency events were centered under and N of the crater. Tremor was unstable during October, with frequencies oscillating between 5 and 1.8 Hz during the first days of the month. Near the end of the month, tremor frequency reached 1.6 Hz with a reduced displacement of 0.38 cm2. SO2 emission ranged from 174 to 2,648 t/d, averaging 1,345 t/d during the month. Deformation measurements (electronic and dry-tilt) showed no significant changes.

Figure (see Caption) Figure 35. Daily seismic energy release (low- and high-frequency events) at Ruiz, July 1985-October 1989. Courtesy of INGEOMINAS.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


November 1989 (SEAN 14:11) Citation IconCite this Report

Small ash explosions; moderate seismicity

Seismicity . . . remained at moderate-low levels in November. Seismic energy was highest on the 22nd, when 694 low-frequency events released 1.8 x 108 ergs. High-frequency seismicity increased only slightly in the second half of the month, with events located N and SW of the active crater at 0.5-6 km depths. Low-frequency tremor was often recorded through the 15th. Brief tremor pulses occurred throughout the month, particularly in the second half, when the majority were associated with small explosions that deposited ash around Arenas crater. SO2 emissions averaged 1,770 t/d (corrected for wind conditions), a slight increase from last month's average. Dry and electronic tilt showed no significant changes.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


December 1989 (SEAN 14:12) Citation IconCite this Report

Small ash ejections; seismicity remains stable

Seismicity dropped in late September, reaching the lowest level since early 1988 in October, and remained at low to moderate levels in November. Seismic activity remained relatively stable in December, with no significant changes in the daily number of high- or low-frequency earthquakes. The energy release of low-frequency events increased slightly toward the end of the month, while the energy released by high-frequency events decreased slightly. High-frequency events were centered in three zones; N of, beneath, and scattered around Arenas Crater at 1-6 km depth. Swarms of these events occurred on the 16th and 18th. Short pulses of low-energy tremor were associated with small ash emissions, one of which deposited a thin layer of ash over Manizales (30 km from Arenas crater) on the 27th. Dry and electronic tilt and short leveling vectors showed no significant variations. SO2 emissions measured by COSPEC were moderate, averaging 1,800 t/d.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


January 1990 (BGVN 15:01) Citation IconCite this Report

Four high-frequency seismic swarms N of the crater; weak tremor pulses but no ash emission; SO2 emission low

Seismicity was at low levels during the first ten days of January, then the number and energy release of high-frequency events increased significantly. Swarms of high-frequency events, mostly centered in a zone ~6 km N of the crater at ~6 km depth, caused four energy release peaks (figure 36). A small number of low-frequency events were recorded during the month. Short pulses of low-energy tremor were not associated with ash emission. Deformation measurements showed no significant changes in January. Five SO2 measurements during January yielded an average of 980 t/d, only about half that of the previous month.

Figure (see Caption) Figure 36. Daily seismic energy release at Ruiz, January 1990. Low-frequency events are shown by a dashed line, high-frequency events by a solid line. Courtesy of INGEOMINAS.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


February 1990 (BGVN 15:02) Citation IconCite this Report

Seismicity remains low

Seismic energy release and the number of earthquakes were at low levels in February. A swarm of low-energy, high-frequency events occurred NW of Arenas crater at 6.5 km depth on 7 February. Pulses of low-energy tremor were also detected. The average measured dry-tilt change in February was only 4 µrad. Variations in electronic tilt (at the Refugio station) were associated with tremor (1.5-2.0 km depth) 14-16 February.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


March 1990 (BGVN 15:03) Citation IconCite this Report

Minor ash emission; seismicity remains low

The number of earthquakes and seismic energy release remained low in March. Located events were centered W and SW of the crater. The strongest recorded earthquake (M 2.1) occurred 21 March. Only a few short pulses of low-energy tremor were recorded, except for a high-energy episode on 12 March at 2301, associated with a small ash emission. Five COSPEC measurements yielded an average SO2 flux of 1,540 t/d, similar to the previous month. Deformation measurements showed no significant changes.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


April 1990 (BGVN 15:04) Citation IconCite this Report

Seismicity remains low-moderate; glacial ablation significant

Seismic energy release and the number of earthquakes were at low to moderate levels in April. Seismicity peaked on 11 April with 162 low-frequency events. Earthquakes were dispersed around the crater, with focal depths of 0.5-6.5 km. Pulses of low-energy tremor began 26 April and persisted until the 29th, when an episode of continuous low-energy tremor was associated with a small ash emission. Dry and electronic tilt showed no substantial changes. Measurements of glacial behavior showed significant ablation, reaching a rate of the order of 240 m3/day. The average rate of SO2 emission, measured by COSPEC, was 1,467 t/d.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


June 1990 (BGVN 15:06) Citation IconCite this Report

Seismicity at low levels; no ash emissions

Seismic activity was at low levels during May and June, with a decrease in seismic energy in early June, then an increase to moderate levels during the second half of the month. Earthquake locations were aligned with the Palestina fault at depths of 0.5 to 12 km, or were oriented oblique to the fault and at shallower depths. Pulses of low-energy tremor were also recorded. There was no significant deformation, although there was a slight increase at the Refugio Station (7 km W of the crater). Glacial measurements indicated a decrease in ablation. June SO2 flux was relatively high, averaging 5,985 t/d as determined by COSPEC.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


August 1990 (BGVN 15:08) Citation IconCite this Report

Frequent ash emission with associated tremor; ashfall to 30 km; hot springs described

Ash emissions were reported during May, July, and August, frequently with associated tremor. Tremor intensity and the number of high- and low-frequency earthquakes fluctuated, roughly corresponding with increased explosive activity. SO2 flux was moderate with the exception of high fluxes recorded during June, and the geochemistry of the hydrothermal system remained unchanged from December 1988.

Ash emissions. Ash was emitted on seven days during May (5, 6, 8, 12, 14, 17, and 24), deposited primarily to the N, NW, and W. On 14 May, ash was reported falling in Manizales (25 km W of the volcano) from 1120 to 1530 with an average cumulative thickness of 0.43 g/m2. No ash was reported during June, but five small ash emissions were reported during July, with a total accumulation of 500 g/m2 at Refugio (2.0 km NW of the crater). The largest emission, on 25 July, deposited ash 30 km from the volcano. The deposits, 2 mm thick at Refugio, were composed exclusively of lithic material. Several small ash emissions were also reported during August.

Volcanic tremor. Tremor was frequently associated with the ash emissions (and with long-period events in August), and its frequency of occurrence and intensity roughly corresponded with the frequency and intensity of ash emissions. During May and July, tremor was more frequent and more intense; the reduced displacement was 3.2 cm2 on 12 May, 2.85 cm2 on 14 May, 3.05 cm2 on 22 May, and reached 3.5 cm2 in July (these were considered moderate to below moderate levels for Ruiz). During June and August when there was little or no ash emission activity, reduced displacements were 0.32 cm2 on 9 June, 0.88 cm2 on 26 June, and <1.0 cm2 in August. During May-August, tremor episodes had periods of 0.1-0.5 seconds (0.15-0.4 seconds during August) and originated at <1 km depth. These episodes usually occurred in pulses with durations of 5-15 minutes, but occasionally were continuous (13-15 May and the end of August).

A second type of tremor, characterized as low-intensity and short-duration, has been noted at Ruiz. It is considered to be from a deeper source and is not associated with ash emissions. During July it originated W of the crater at >=1 km depth.

Other seismicity. Seismic activity increased during May with 1,326 high-frequency and 1,982 low-frequency recorded earthquakes (up from 579 and 1,580 respectively in April). Of these, 247 high- and 156 low-frequency earthquakes, occurred during a swarm on 31 May. The earthquakes were centered in three clusters; NE of, SW of, and under the crater, aligned with the Palestina fault, and at depths from 0.5 to 4.5 km. During June, 1,664 high- and 1,422 low-frequency earthquakes of M <= 2.8 were recorded, at depths of 0.5-12 km. Epicenters were aligned with and transverse to the Palestina Fault. Seismicity increased during July, with mainly long-period earthquakes and bursts of seismicity consisting of many high- and low-frequency earthquakes occurring in trains. The earthquakes were located around the crater at depths of 0.5-5.0 km. A swarm of 400 earthquakes (M <=2.6), with three felt shocks at the onset, were recorded over a 6-hour period on 28 August (figure 37). The swarm was located NE of the crater with focal depths < 1.5 km (figure 38).

Figure (see Caption) Figure 37. Seismicity at Ruiz, August 1990. Solid line, high-frequency events; dashed line, low-frequency events. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 38. Epicenters of high-frequency earthquakes at Ruiz, August 1990. Courtesy of INGEOMINAS.

Deformation. Deformation continued to be monitored at Ruiz using a network of dry-tilt and EDM stations; one new EDM station was added to the network in June near the Bis seismic station (at 5,030 m, almost 6 km NW of the crater). A few short-term episodes of moderate deformation were noted during May, but no significant deformation was detected during June-mid-August. On 13 August, the Refugio EDM station showed a rapid 100-µrad displacement (figure 39), but this did not correspond with any other recognized changes in activity (seismic, geochemical, or deformational) at the volcano.

Figure (see Caption) Figure 39. Deformation at Refugio EDM station, Ruiz, August 1990. Courtesy of INGEOMINAS.

Measurement of topographic controls on the summit glaciers indicated a decrease in ablation in June with respect to April and May.

Plume geochemistry. COSPEC monitoring indicated a decrease in SO2 flux following high levels in June. The monthly average SO2 flux was 1,519 t/d in May (11 measurements with a range of 367-3,869 t/d), 5,985 t/d in June (three measurements, 5,208-7,498 t/d), 1,097 t/d in July (six measurements, 406-2,672 t/d), and 2,437 t/d in August (figure 40).

Figure (see Caption) Figure 40. Monthly average SO2 flux from Ruiz, 1988-90. Upper line is calculated with measured wind data; lower line without wind data. Courtesy of INGEOMINAS.

Geochemistry of the hydrothermal system. The following is by S. Williams, S. Schaefer, and José Vasquez.

"The large white gas column continues to boil continuously from Ruiz. We visited and sampled hydrothermal springs between 11 and 16 August. The geochemistry of all of the sites has been studied and is reported in Sturchio and others (1988) and Williams and others (1990). His isotopic data are reported in Sano and others, 1990. The Azufrera Nereidas gas vent, located in the Nereidas valley at 3,575 m elevation, had maximum temperatures of 86°C. Gas release appeared to be unchanged from the previous visit in December 1988. The hot spring, located in the river canyon below the gas vent, was found to have temperatures of 51°C and pH of 6.1. The flow rate was estimated to be between 1 and 5 liters/minute. Abundant sulfur deposition is evident at the spring. In Botero Londoño hotspring, at 15 km distance and 2,450 m elevation, spouting hot water had a maximum temperature of 95°C and pH of 7.6. The springs closest to the crater, Río Gualí (at 3 km and 4,670 m) had a maximum temperature of 57°C and pH of ~3.8. These are located within ~50 m of the tongue of the glacier in the Gualí valley. Aguas Calientes, at 7 km and 3,780 m elevation, was found to be unchanged from the previous visit (December 1989) with a maximum temperature of 61°C and pH of 1.6. Other hot springs sampled in July included El Recodo and the Hotel Termales del Ruiz. El Recodo, a bicarbonate spring, had a temperature of 60°C and pH of 7.8, unchanged from measurements made in December 1986. The Hotel is a strong acid-sulfate-chloride spring with a temperature of 64°C and pH of 1.1."

References. Sano, Y., Wakita, H., and Williams, S.N., 1990, Helium isotope anomaly in Nevado del Ruiz volcano, Colombia: implications for volcanic hydrothermal system: JVGR, v. 42, p. 41-52.

Sturchio, N.C., Williams, S.N., García P., N., and Londoño C., A., 1988, The hydrothermal system of Nevado del Ruiz Volcano, Colombia: BV, v. 50, p. 399-412.

Williams, S.N., Sturchio, N.C., Calvache, M.L., Mendez, R., Londoño C., A., and García P., N., 1990, Sulfur dioxide flux from Nevado del Ruiz volcano, Colombia: total flux and isotopic constraints on its origin: JVGR, v. 42, 53-68.

Information Contacts: C. Carvajal and F. Cruz, INGEOMINAS, Manizales; S. Williams and S. Schaefer, Louisiana State Univ; J. Vasquez, Beloit College.


September 1990 (BGVN 15:09) Citation IconCite this Report

Ash emissions with associated tremor; seismicity increases

The number of high-frequency earthquakes and total seismic energy release increased during September (figure 41). A swarm of high-frequency earthquakes on 17 September was centered NW of the summit at depths of 3.0-7.0 km (figure 42). Pulses of volcanic tremor (periods of 0.2-0.3 seconds) were recorded throughout the month, and were occasionally associated with small ash emissions. Tremor was continuous from 27 September through the end of the month, with associated ash emissions. Although dry-tilt did not show any significant changes, 6.56 µrad of deformation were measured 7 km from the summit (at Refugio station) on 4 and 8 September, with coincident seismic activity. The average SO2 flux for the month, measured by COSPEC, was 2,448 t/d. A "Japanese box" sampling device (an open beaker containing a 10 N KOH solution placed within the volcanic plume), operated 2.5 km from the summit in July, contained 1.52 mole % SO2 and 0.59 mole % HCl.

Figure (see Caption) Figure 41. Daily seismic energy release at Ruiz, 1985-90. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 42. Epicenters of 54 high-frequency earthquakes at Ruiz, September 1990. Courtesy of INGEOMINAS.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


October 1990 (BGVN 15:10) Citation IconCite this Report

Small ash emissions and seismicity

Many small ash emissions occurred during October, although seismicity remained at low levels. Two small swarms of high-frequency earthquakes were recorded on 14 and 22 October. Tremor episodes (2 cm2 maximum reduced displacement) were prominent and were occasionally associated with small ash emissions. Although EDM measurements showed important changes, dry-tilt did not show ground deformation. Similarly, EDM indicated 6.6 µrad of deformation at one station during September, while dry-tilt did not show any significant changes. The average SO2 flux for the month, measured by COSPEC, was 1,630 t/d, compared to 2,448 t/d in September.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


November 1990 (BGVN 15:11) Citation IconCite this Report

Minor ash emission; seismicity; SO2 flux declines

Many small ash emissions occurred and high-frequency seismicity was at high levels during November. Hypocenters were located around the crater at shallow depths. Pulses of tremor occurred frequently, often associated with the ash emissions. Low-frequency seismicity was at low levels and there was no measured ground deformation. The SO2 flux continued to decrease, averaging 860 t/d.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


December 1990 (BGVN 15:12) Citation IconCite this Report

Small ash emissions

Several ash emissions occurred during December. Seismic activity was characterized by high-frequency earthquakes (figure 43), centered W and SW of the the crater. Tremor was frequent, but of low energy. Ground deformation measurements showed no significant changes. The month's average SO2 flux was 1,464 t/d, up from 860 t/d in November.

Figure (see Caption) Figure 43. Daily seismic energy release at Ruiz, December 1990. Solid line, high-frequency events; dashed line, low-frequency events. Courtesy of INGEOMINAS.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


January 1991 (BGVN 16:01) Citation IconCite this Report

Minor ash emission; continued seismicity

Sporadic minor ash emission occurred during January. Seismic activity was characterized by high-frequency events with typical low levels of energy release (figure 44). Some increases occurred to high energy levels.

Figure (see Caption) Figure 44. Daily seismic energy release at Ruiz, January 1991. Solid line – high-frequency events; dashed line – low-frequency events. Courtesy of INGEOMINAS.

Tremor episodes were brief (around 10 minutes) and of low intensity during the month. Low-frequency events were uncommon and of low energy. On 16 January at 0242, a M 3.8 high-frequency event, centered 1.5 km S of Arenas crater at 3.8 km depth, was felt around the volcanic complex.

Dry-tilt stations and the electronic tiltmeters at Refugio and Recio recorded no deformation. Morphologic changes were observed at Diablos Rojos B glacier. The average rate of SO2 emission measured during the month was about 1,140 t/d, down slightly from 1,464 t/d in December.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


February 1991 (BGVN 16:02) Citation IconCite this Report

Small ash emissions with tremor

Sporadic, small ash emissions continued, while seismicity remained at low levels during February. No significant variations in energy release or number of events were recorded. High-frequency earthquakes occurred in three zones; at the crater, and to its S and E (earthquakes had not recently occurred in the latter zone). Low-level tremor pulses were often associated with the ash emissions. No significant changes in deformation were observed. The monthly average SO2 flux, measured by COSPEC, was 753 t/d.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


March 1991 (BGVN 16:03) Citation IconCite this Report

Continued gas emission; two seismic swarms; ash to 30 km distance

Two high-frequency earthquake swarms were recorded in March, the first centered N of Arenas crater, and the second to the S. The number of events, energy released, and tremor amplitude were all at low levels. No significant changes in deformation were observed. Ashfall was reported up to 30 km WNW (Villamaría), from an emission on 5 March. The monthly average SO2 flux, measured by COSPEC, was 2,233 t/d, an increase from 753 t/d in February and 1,140 t/d in January.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


April 1991 (BGVN 16:04) Citation IconCite this Report

Tremor precedes several days of ash emission

An increase in the number of tremor pulses preceded several days of ash emission at the end of April. Lithic and crystalline ash (<2 mm in diameter) was reported W of the volcano in Pereira (40 km from the summit), Santa Rosa de Cabal (35 km), Chinchiná (35 km), and Manizales (25 km), and NE of the volcano in Mariquita (55 km). High- and low-frequency seismicity was generally at low levels in April, with a slight increase in released energy from low-frequency events. The monthly average SO2 flux, measured by COSPEC, was ~2,740 t/d, up from 2,233 t/d in March.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


May 1991 (BGVN 16:05) Citation IconCite this Report

Frequent lithic ash emissions; occasional vigorous earthquake swarms

Lithic ash emissions were frequent during May, depositing material to Manizales (30 km WNW) on 1 May. Short pulses of shallow tremor were associated with the emissions. High-frequency seismicity reached very high levels during a swarm on 8 May (figure 45), which included a M 2.1 earthquake, 2.5 km N of Arenas crater at 5 km depth. A similar swarm occurred on 14 May. Low-frequency seismicity was at a moderate level in May, with peaks of vigorous seismicity on 4 days. Deformation measurements showed no significant changes. The SO2 flux was low; the monthly average was 930 t/d, compared to ~2,740 t/d in April.

Figure (see Caption) Figure 45. Daily number of seismic events (bottom) and energy release (top) at Ruiz, May 1991. Solid line, high-frequency events; dashed line, low-frequency events. Courtesy of INGEOMINAS.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


June 1991 (BGVN 16:06) Citation IconCite this Report

Ash emission and low seismicity; increased SO2 flux

Activity was generally at low levels in June, although there were one large ash emission and a high-frequency seismic swarm. The ash emission was associated with low to moderate levels of tremor, and deposited material on Manizales (30 km WNW). One earthquake, located 2.5 km S of the summit crater, was felt during the swarm. The monthly average SO2 flux, measured by COSPEC, was 2,275 t/d, compared to 930 t/d in May and ~2,740 t/d in April. Deformation measurements did not show significant changes.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


July 1991 (BGVN 16:07) Citation IconCite this Report

Seismicity remains at low levels; small ash emissions

Seismicity was at very low levels in July, although tremor reached slightly higher levels at the beginning of the month. Deformation measurements showed no significant changes. The SO2 flux continued to fluctuate, with a monthly average of ~1,220 t/d. Two small ash emissions, restricted to the summit region, were observed during July.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


August 1991 (BGVN 16:08) Citation IconCite this Report

Seismicity, deformation, and gas emission remain unchanged

Seismicity remained at low levels in August, with earthquakes mainly W and N of the crater at 0-5 km depths. Tremor episodes were brief and of low energy. Deformation showed no significant changes. The monthly average SO2 flux was 1,135 t/d, similar to July.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


September 1991 (BGVN 16:09) Citation IconCite this Report

Seismicity and SO2 flux at low levels

The number of seismic events and the amount of released energy were both at low levels in September. Only a few short pulses of very low-energy tremor were recorded. Deformation showed no significant changes. The monthly average SO2 flux was low, declining to ~925 t/d from 1,135 t/d in August.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


October 1991 (BGVN 16:10) Citation IconCite this Report

Continued weak seismicity and SO2 emission

Although seismicity remained at very low levels in October (figure 46), there was a slight relative increase in long-period activity. High-frequency earthquakes were centered NE and SW of the summit. The SO2 flux varied between moderate and low values, and deformation measurements showed no significant changes.

Figure (see Caption) Figure 46. Daily seismic energy release (top) and number of earthquakes (bottom) recorded at Ruiz, January-October 1991. Horizontal lines indicate classification thresholds (used in previous Bulletins) for different levels of activity. Courtesy of INGEOMINAS.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


November 1991 (BGVN 16:11) Citation IconCite this Report

Seismicity weak; no deformation evident

Seismic energy release and the number of earthquakes were at low levels, and only a few pulses of tremor were recorded in November. Deformation measurements showed no significant changes.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


January 1992 (BGVN 17:01) Citation IconCite this Report

Weak steam emission; low-level seismicity

Weak steam emission from the active Arenas crater produced a white plume 800 m high in January. Volcanic seismicity was at very low levels and tremor was infrequent. A small swarm of high-frequency earthquakes on 2 January caused a peak in seismicity, with high levels of released energy. High-frequency events were centered around Arenas crater and the S flank at 0.5-5 km depths. Deformation measurements showed no significant changes.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.


May 1994 (BGVN 19:05) Citation IconCite this Report

Earthquake swarms in March and April end two years of low activity

A high-frequency earthquake swarm in mid-March and early April ended nearly two years of low activity. Significant long-period earthquakes began in mid-April. Several swarms on 19, 22, and 23 April culminated in an explosion at 1554 on the 23rd. Seismic activity gradually declined after the explosion. The Emergency Committee of Caldas declared a yellow alert and suspended visitor and tourist passes until the seismicity had decreased to acceptable levels. [INGEOMINAS stated that there was no emission of ash at the time of the 23 April earthquake swarm.]

Information Contacts: INGEOMINAS, Manizales; U.S. Embassy, Bogota.


May 1996 (BGVN 21:05) Citation IconCite this Report

Earthquake swarms during July-September 1995 and January-April 1996

Almost two years of low-level seismicity ended in mid-March 1994 with the occurrence of a high-frequency earthquake swarm followed by long-period events and an explosion on 23 April (BGVN 19:05). Activity returned to low levels through the rest of 1994.

A mid-sized landslide in January 1995 descended the upper reach of the Lagunillas River but caused no significant damage. It was primarily caused by ground and ice-cap instability, not volcanism. Seismicity in July and August 1995 was stronger than in April 1994. Swarms of long-period events reached a maximum count of 1,050 events on 26 July with more than 6.3 x 108 ergs of energy released. Some of the events were related to explosions heard by scientists doing fieldwork some kilometers away from the Arenas Crater, but ash emission was not confirmed. No significant volcano-tectonic activity was registered. Swarms of long-period events during early September 1995 were similar to those of July-August, but were fewer in number and had less energy. This volcanic related seismicity was located mostly toward the Arenas Crater and the SW part of the volcano at shallow depths.

Seismicity during January-April 1996 remained low, except for the first 10 days of January when there was an increase of long-period screw-type events, with a high of seven on the 5th. Most of these events were located at shallow depths near Arenas Crater and over its W side. Screw-type events have become significant since May 1995. Some volcano-tectonic earthquake swarms also occurred during these four months. Two significant swarms were located toward the S part of the volcano, near the RECI seismic station (figure 47). In both swarms, maximum magnitudes were close to 3. Tremor signals were intermittent; some saturated the stations closest to Arenas Crater, but none were correlated to ash emissions. The electronic tiltmeter 800 m from Arenas Crater (FARA) did not show significant variations. During these four months there were a total of 657 volcano-tectonic earthquakes and 1,308 long-period events recorded by the observatory network. This suggests that processes related to fluids within the volcanic conduits were dominant over fracture-related processes.

Figure (see Caption) Figure 47. Location of telemetered stations and significant seismic events recorded at Ruiz during January-April 1996. Courtesy of INGEOMINAS.

Nevado del Ruiz, located 33 km SE of Manizales, is a broad stratovolcano of andesitic and dacitic lavas and andesitic pyroclastic deposits that cover more than 200 km2. Steep headwalls of massive landslides cut its flanks, and melting of its summit ice cap during historical eruptions resulted in devastating lahars. The last eruption began with moderate phreatic ejections on 11 September 1985. On 13 November 1985 an explosive eruption produced pyroclastic flows and surges that melted part of the summit ice cap. Major mudflows subsequently devastated Armero and other towns on the flanks of the volcano, causing over 23,000 fatalities. Intermittent minor ash emissions with occasional stronger phreato-magmatic eruptions continued until July 1991.

Information Contacts: John Jairo Sánchez A., Fernando Gil Cruz, Alvaro Pablo Acevedo, John Makario Londoño, and Jairo Patiño Cifuentes, INGEOMINAS Observatorio Vulcanológico y Sismológico de Manizales (OVSM), A.A. 1296, Manizales, Caldas, Colombia.


September 1996 (BGVN 21:09) Citation IconCite this Report

Seismic swarms; gas plumes; newly found fumarolic field and hot spring

During May-July, seismic activity at Ruiz remained quite low. Significant volcano-tectonic earthquake swarms occurred on 8, 10, 11, 16, and 23 May, and 7, 15, and 18 June (figure 48). Most were located at depths of <7 km and within 3 km of Arenas Crater. The strongest volcano-tectonic earthquake (M 2.2) was recorded at 1636 on 10 May. Swarms of long-period events were registered on 9, 20, 23, and 25 May. Scientists working in the field reported that an isolated long-period event at 1153 on 29 May was correlated with an explosion-like sound possibly caused by the fall of solid material. The analog recorders detected this event, but the digital systems did not.

Figure (see Caption) Figure 48. Released energy and number of volcano-tectonic and long-period events at Ruiz during May-July 1996. Scales are approximate. Courtesy of INGEOMINAS.

Visual monitoring indicated that normal white gas plumes occurred over the Ruiz summit and reached an altitude of <2 km. The FARALLONES electronic tiltmeter did not record any significant deformations during May-July.

A new fumarolic field and a hot spring, both called "El Calvario," were found 1.7 km NE of Arenas Crater at an elevation of 4,628 m. The fumarole had a temperature of 84°C and pH of 3.8. Emissions consisted of: H2O vapor, 95.5%; CO2, 4.3%; total S, 0.18%; and HCl, 0.001%. The water from the hot spring had the following features: temperature, 66.4°C; pH, 2.7; Cl, 10 ppm; and SO4, 1,545 ppm.

Information Contacts: John Jairo Sánchez, Alvaro Pablo Acevedo, Fernando Gil Cruz, John Makario Londoño, Jairo Patiño Cifuentes, Claudia Alfaro Valero, Hector Mora Páez, Cesar A. Carvajal, Luis Fernando Guarnizo, and Jair Ramirez, INGEOMINAS Observatorio Vulcanológico y Sismológico de Manizales (OVSM), A.A. 1296, Manizales, Caldas, Colombia.


April 1999 (BGVN 24:04) Citation IconCite this Report

Moderate earthquake swarm

A press release on 31 March noted that small long-period earthquakes had been detected at Ruiz throughout the month, although some may have been related to glacier movement; one long-period event on 24 March saturated the seismic stations near the crater. After several months of low seismicity, a moderate swarm of 80 volcanic-tectonic earthquakes within an hour was recorded on 15 April. The largest had a magnitude of 1.3. Small long-period earthquakes were present during the entire month of April, centered on the SW flank near the crater. Seismicity was still at low levels as of 25 May.

Information Contacts: INGEOMINAS, Volcanological and Seismological Observatory of Manizales, Avenida 12 de Octubre No. 15 - 47, Manizales, Colombia (URL: http://www.umanizales.edu.co/~uom/).


May 2002 (BGVN 27:05) Citation IconCite this Report

Largest earthquake swarm since 1985 occurs during June 2002

The last reported activity at Nevado del Ruiz was a moderate earthquake swarm during late March through April 1999 (BGVN 24:04). On 9 June 2002 at 2300 another swarm of volcano-tectonic earthquakes began. Following the swarm, hundreds of hybrid earthquakes were recorded, with more than 1,300 earthquakes occurring in 16 hours. High seismicity marked the following 3 days during which a total of ~2,300 earthquakes were recorded. This is the highest number of events recorded per day at Nevado del Ruiz since 1985. According to news reports, the earthquakes had magnitudes up to ~2.3 and occurred at depths of 0.5-3 km. In addition to heightened seismicity that was felt by people near the volcano, jet-like sounds corresponded with some of the hybrid earthquakes, and a strong odor of SO2 was reported near the summit. No ash emissions were reported, and seismicity decreased by 13 June. At the height of the activity the Alert Level was at Orange.

General References. Lescinsky, D., 1990, Nevado del Ruiz volcano, Colombia: a comprehensive bibliography: JVGR, v. 42, p. 211-224.

Williams, S., ed., 1990, Nevado del Ruiz, Colombia; (I) JVGR, v. 41, p. 1-379 (18 papers); (II) JVGR, v. 42, p. 1-224 (13 papers).

Information Contacts: John Macario Londoño Bonilla, Volcanological and Seismological Observatory of INGEOMINAS, Avenida 12 Octubre 15-47, Manizales, Colombia (URL: https://www2.sgc.gov.co/); El Tiempo; La Libertad.


July 2012 (BGVN 37:07) Citation IconCite this Report

1988-2006 monitoring captures seismic swarms, deformation, and radon emissions

Our last report on Nevado del Ruiz (BGVN 27:05) focused on a swarm of earthquakes that occurred in June 2002, when the Instituto Colombiano de Geología y Minería (INGEOMINAS) raised the Alert Level to II ("Orange", on a scale from I-IV, where the highest Alert Level is I, "Red"). Monthly reports from the INGEOMINAS Manizales Observatory became available online beginning in March 2006 and continued through the time period covered in this report, March-December 2006. We also include the long-term datasets of deformation recorded from 1988 to 2006 and radon-gas monitoring from 2002 to 2006.

INGEOMINAS characterized overall activity at Nevado del Ruiz from March to December 2006 as limited to small earthquakes, minor rockfalls, and intermittent vapor plumes. They measured continuous deformation trends (primarily from 3 tilt stations), and low levels of radon-gas emissions with a peak in March 2006 at two stations. No Alert Level was defined for this time period.

Seismicity during 2006. INGEOMINAS reported that low seismicity generally prevailed from March through December 2006; 217-673 events occurred per month at depths of 6-10 km below the summit with maximum local magnitudes of 0.95-2.3. Long period (LP) events occurred slightly more often than volcano-tectonic (VT) events; 1-5 hybrid events were detected each month except in December when these events were absent. Tremor was recorded only once in September and twice in October.

Two small VT earthquake swarms were recorded, one in March and the other in May. The swarm on 9 March occurred as a cluster of events 2-4 km deep centered to the SE of the crater (figure 49). The swarm on 29 May was characterized by ~20 events located SE of the crater with magnitudes less than 1.02.

Figure (see Caption) Figure 49. Maps and cross-sections showing epicenters and hypocenters for VT events detected at Nevado del Ruiz for March (top) and December (bottom) 2006. Note that the colored depth scales are different for the two months (labeled as "Profund." in each frame). The bottom and right-hand edges of the maps show vertical cross sections with horizontal lines at 2 km depth intervals. More earthquakes were located in March (647) than December 2006 (290), however, events as deep as 8 km were located in December. Courtesy of INGEOMINAS.

Rockfalls, ice movement, and debris flows were also detected by the seismic network from March to December 2006. For these kinds of events, typically more than 250-600 per month were detected; however, fewer events were detected in April and June, 61 and 47 events respectively.

Vapor plumes in 2006. During most of 2006 vapor plumes were visible from the summit area of Nevado del Ruiz. Often appearing intermittently, these plumes were white or white-to-gray colored and reached 100-600 m over the crater rim. Plume emissions have been associated with the fumaroles within the summit crater.

Deformation summary. The deformation network at Nevado del Ruiz in March 2006 contained 12 dry tiltmeter stations (Piraña, Rubí, Bis, Molinos, Tumbas, Refugio, Nereidas, Pequeño, Pijao, Arenales, Alfombrales, and Recio) and four stations for leveling campaigns (Piraña, Bis, Tumbas, and Nereidas; figure 50). This network was developed to cover the W and N flanks; the S and E flanks did not have network coverage during this reporting period. Fieldwork was planned to include leveling at sites Arenales, Alfombrales, and Recio since they had not been occupied for several years. Four tilt stations showed inflation and deflation trends (Bis, Nereidas, Refugio, and Tumbas) and are discussed in the text below.

Figure (see Caption) Figure 50. Map of station locations for deformation monitoring at Nevado del Ruiz. Tiltmeter stations (red triangles) are marked 1-12 while line-leveling stations (short blue lines indicating line orientation) are 13-16. Courtesy of INGEOMINAS.

Tilt station Bis was established in late 1988 on the NW flank ~5.7 km NW of the active crater (figure 50). As seen on figure 51, inflation had been recorded at Bis from 1988 through 1999 with a cumulative tilt increase of as much as 40-60 microradians (µrad; figure 51). Since the beginning of 2000 until the end of 2004, this station recorded stable conditions with a small amount (4 µrad) of inflation. From 2004 through March 2006 there was another significant increase in the inflation trend; a cumulative 22 µrad N component and 15 µrad E component inflation.

Figure (see Caption) Figure 51. Deformation trends measured by the dry tilt station "Bis" (on the NW flank of Nevado del Ruiz) from 1988 to March 2006. N and E components are shown in blue and red, respectively. Courtesy of INGEOMINAS.

Tilt station Nereidas was installed 4.6 km SW of the active crater and measured significant changes primarily from late March 1993 to March 2006. Inflation and deflation trends were recorded, 13 µrad N and 11 µrad E, respectively.

Station Refugio, located 2.6 km NW of the active crater, has primarily recorded stable conditions since 1990.

Station Tumbas was located on the NW flank of the volcano ~4.8 km from the crater. This station has shown deflation from both components since 2000. Since February 2005 the cumulative deflation of the N component was 7 µrad and 13 µrad in the E component. From 2005 to March 2006 there were fluctuations from this station within the measurable range of the tiltmeters.

Long-term radon gas measurements. Radon monitoring at Nevado del Ruiz has been based on six stations. In particular, INGEOMINAS has long records from stations Gualí and Hotel Termales since 2002 and 2003, respectively (figure 52). The locations of the radon gas sampling stations were not disclosed, however a 1986 map of instrumentation places the Hotel Termales (labeled "Termales" with a square and "X")and Río Gualí (marked with a circle near the river) stations within 12 km to the NW of the summit crater (figure 53). In March 2006, results from three radon monitoring sites suggested to INGEOMINAS that there was a possible correlation with the earthquake swarms detected on 9 March 2006. Stations Río Gualí, Gualí, and Rubí recorded an increase in radon emission on 5 March while stations Condor and Cajones maintained low levels (55 pico Curies per Liter, pCi/L). From April through December 2006, no major changes were noted in radon gas emissions.

Figure (see Caption) Figure 52. Nevado del Ruiz radon gas emission measurements (pico Curies per Liter, pCi/L) from stations Hotel Termales (January 2002-May 2006, top frame) and Río Gualí (January 2005-May 2006, middle frame) and daily earthquake counts for both VT and LP events for March 2006 (bottom frame). The green dashed squares indicate correlated time periods for each plot. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 53. A 1986 map of monitoring networks at Nevado del Ruiz including temperature (open circles), geochemistry (open triangles), electronic distance measurement (EDM) stations and reflectors (red filled triangles and yellow filled circles, respectively), dry tilt (purple filled circles), electronic tilt (green filled cirles), and seismometers (orange and red filled circles). Major features are also highlighted including the summit crater (the area concentrically colored red around orange in the center), the extent of persistent ice on the edifice (blue shaded areas), neighboring peaks, lakes (areas filled with vertical lines), rivers (dark blue lines), roads (red lines), and the town Murillo (the most proximal settlement to the volcano, shown at the far right). Courtesy of INGEOMINAS.

Information Contacts: Instituto Colombiano de Geología y Minería (INGEOMINAS), Volcanological and Seismological Observatory, Avenida 12 Octubre 15-47, Manizales, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html).


August 2012 (BGVN 37:08) Citation IconCite this Report

Several years of escalating seismicity followed by ash explosions

Our last report on Nevado del Ruiz (BGVN 37:07) summarized monitoring efforts by the Instituto Colombiano de Geología y Minería (INGEOMINAS) volcano observatory based in Manizales, highlighting the long records of geophysical and radon-gas data starting in 1988 and continuing through 2006. Here we follow up on volcanic activity from 2007 to 2012, including an escalation leading to explosions in February 2012. Elevated seismicity, wide-spread ashfall, and very high SO2 fluxes (~30,000 tons/day) resulted in a Level I Red Alert announcement (on a scale from IV to I, Alert Level I is the highest, "Red Alert") in June 2012 and public notices of evacuations. Activity subsided in July 2012 and remained low through the remainder of this reporting period ending 9 September 2012.

Seismicity from 2007-August 2010. From 2007 to August 2010, INGEOMINAS reported numerous volcano-tectonic (VT) and long-period (LP) events originating at depths of 1-12 km below Nevado del Ruiz. Rare hybrid and tremor earthquakes were detected, and seismic swarms occurred intermittently (19-78 events per swarm; figure 54). Seismicity was frequently concentrated within the crater and to the SE, S, SW, and W (table 3).

Figure (see Caption) Figure 54. Maps of located earthquakes at Nevado del Ruiz during the month of April 2010. (Left) This map shows the distribution of VT events and cross-sections for depths in 1 km intervals; the 15 April 2010 swarm is circled. (Right) This map shows 209 registered LP events (M 0.09-2.15); frequencies were below 5 Hz with average event durations of 0.3 s. LP events were concentrated in a zone to the W of the crater, a characteristic observed in records since 2006. Courtesy of INGEOMINAS.
Figure (see Caption) Table 3. Seismicity types and counts at Nevado del Ruiz registered from 2006 to September 2012 compiled from INGEOMINAS reports. The LP Total column accounts for all forms of LPs including hybrid and tornillo when present; tornillo earthquakes are described by Narváez and others (1997). The TR/TO column contains tremor ("TR") and tornillos ("TO"). Epicenter Clustering refers to directions relative to the crater, and to epicenters occurring within the immediate crater region "C". Notable Seismicity includes swarms with dates and the number of events provided when known in parentheses; seismicity interpreted as possible explosions is listed as "ES" (explosion signature); multi-events ("ME") refer to seismicity that is described in figure 56; pseudo-tornillo events are listed ("PT"), a class of earthquakes also detected at Galeras volcano (BGVN 37:04) and illustrated in figure 55. For all entries with "na," this represents seismicity that has been recorded but only tallied within the LP Total column. The "x" indicates values not currently available. Shading (yellow, orange, and red) corresponds to the alert announcements released by authorities according to the level of hazardous conditions. Courtesy of INGEOMINAS.

Geodesy, 2007-August 2010. Deformation monitoring expanded in late 2007 when INGEOMINAS installed additional electronic tilt stations, augmenting their dry tilt datasets. Dry tilt measurements had been recorded since at least 1986 (see the station distribution map, figure 10 in BGVN 37:07). While the term "dry tilt" is pervasive in volcano monitoring literature, this can cause confusion as it was originally adopted to differentiate measurements made with water leveling techniques (Yamashita, 1992). Alternative terms are "single-setup leveling" or "tilt leveling" however, the term "inclinómetro seco," has been used consistently throughout INGEOMINAS monthly technical reports since March 2006. Tilt measurements collected with site occupation techniques are manually intensive, requiring extensive field time, reliable benchmark pairs, a spirit level, and leveling rods. In August 2010, dry tilt values were available from three stations and electronic tilt values were available from five operating stations; results were reported in the INGEOMINAS technical bulletin (available online).

In August 2008, electronic distance meter (EDM) base stations and reflectors were installed on the W flank of the volcano. Site occupations at Olleta and Refugio recorded stable conditions from September 2008 through August 2010.

Gas emissions, 2007-August 2010. Frequent steam plumes were visible reaching 50-850 m above the crater from January 2007 through August 2010. On 17 July 2010, the Washington Volcanic Ash Advisory Center (VAAC) was alerted to a spike in seismicity detected at Nevado del Ruiz. Several aviation alerts were released; however, no volcanic ash was detected in satellite imagery and advisories were canceled that same day. Several peaks in diffuse soil CO2 emissions were detected in mid-2008 from two geochemical stations, Gualí and Cajones (N and S of the summit, respectively).

Radon-gas emissions measured at Gualí and Cajones also showed peaks in early 2010. INGEOMINAS had maintained emission records since 1995 and was investigating links between radon emissions and earthquakes (Garzón and others, 2003). Radon hazard investigations had been conducted in Manizales (located ~30 km NW of the volcano) by INGEOMINAS that determined water supply and household levels of radon (Salazar and others, 2003). This baseline data was mapped for SE Manizales and showed low levels of radon in water supplies and also low levels at the 43 indoor sites where passive sampling detected an average of 1.9 pCi/L.

During fieldwork on 30 November-1 December 2009, INGEOMINAS installed two scanning Differential Optical Absorption Spectrometer (DOAS) systems within 5 km W of the edifice. Stations Bruma and Alfombrales were telemetered to send SO2 flux data to the Manizales observatory where results were analyzed with NOVAC software. The Network for Observation of Volcanic and Atmospheric Change (NOVAC), designed by the European Commission's Sixth Framework Program, supported this installation. Colombia was one of seven countries participating in the program that sought to monitor and assess SO2 emissions from active volcanoes (Galle and others, 2009). During 2-29 December, SO2 flux ranged 195-554 t/d at Bruma and 41-140 t/d at Alfombrales.

Escalating seismicity from September 2010 to 2011. Seismicity notably increased in September 2010 and prompted authorities to raise the alert to Level III (Yellow, on the four-level scale) on 30 September (table 3). Within four months, pseudo-tornillo earthquakes (figure 55) and possible explosive signatures appeared in the seismic record. From September 2010 through December 2011, an average of more than 890 VT earthquakes per month were recorded, almost eight times as many events as recorded during the previous 12 months. A similar increase in LP events was also observed during this time period; however, epicenters were clustered in the same regions as previous years: within the crater, to the SE, S, SW, and W (as in figure 54).

Figure (see Caption) Figure 55. This long-period earthquake (described as a pseudo-tornillo) was recorded on 6 January 2011 at 1343 from Nevado del Ruiz on seven seismic stations (appearing strongest on station BISz, the trace second from the top). BISz is the closest seismic station to the volcano, located ~2 km W of the crater. The spectra (right) show a dominant frequency of ~6.25 Hz; this characteristic, in addition to the relatively short coda, classified the event as a pseudo-tornillo (Narváez and others, 1997). Courtesy of INGEOMINAS.

A type of earthquake classified as "multi-event" began to appear in February 2011 (see ME events in table 3). These events frequently occurred from February through August and were attributed to small explosions and degassing (figure 56). Tremor and tornillo earthquakes were recorded in March of 2011 and, over the next six months, occurred more frequently with time.

Figure (see Caption) Figure 56. Seismic traces of a "multi-event" registered at 1351 on 6 October 2011 as recorded at five stations around Nevado del Ruiz. The earthquake appeared strongest at BISz, the closest station to the volcano, and much weaker-to-unrecognizable at other stations. Courtesy of INGEOMINAS.

Geodesy, September 2010-2011. During September 2010-2011, INGEOMINAS recorded stable conditions with minor fluctuations from the EDM stations Refugio and Olleta. Both stations were surveyed in February, October, and November 2011, and only Refugio was surveyed in September and December.

INGEOMINAS noted an increasing trend at the electronic tilt station LISA that began in October 2010 and continued through 2011; the two components registered a cumulative increase of 20 µrad. RECIO had been recording stable conditions until May 2011; from May through December 2011, the N component increased by 23 µrad and the E component decreased by 10 µrad. Corrective measures had been taken to protect the BIS and REFUGIO tilt stations from thermal effects, however, cyclical changes persisted in their datasets. By December 2011, seven electronic tilt stations were online and were recording minor fluctuations primarily due to temperature change.

Permanent GPS stations Gualí and Nereidas were installed on the lower W flanks between May and August 2011 and a third station, Olletas, was online by November 2011. GPS instrumentation and continuous data processing were part of a collaborative effort between INGEOMINAS and the University of Wisconsin, Madison.

SO2 emissions, 2010-2012. Since installation of the two scanning DOAS stations in late 2009, background levels of SO2 were rarely higher than 1,000 t/d until September 2010. INGEOMINAS recorded increased SO2 emissions in late 2010 (figure 57), while plumes rose to heights of 220-1,000 m above the crater (averaging ~700 m) through 2011. An increase was observed from November 2010 through much of 2011; maximum daily values of SO2 flux frequently exceeded 1,500 t/d. Occasional peaks above 3,000 t/d were recorded from November 2010 to January 2011 (a), June-July 2011 (b), and November 2011 to February 2012 (c). Beginning in February 2012, emissions dramatically increased during a period of escalated seismicity (table 3). SO2 flux peaked during May and June; the three strongest peaks were greater than 33,000 t/d. By late June, emissions were declining.

Figure (see Caption) Figure 57. (Top) The map of the geochemical network for Nevado del Ruiz shows sites for thermal springs, scanning Differential Optical Absorption Spectrometer (DOAS) stations (white triangles show coverage area directed toward the crater), alkaline sampling, and radon gas sampling. (Bottom) The histogram summarizes maximum daily SO2 flux from scanning DOAS stations from January 2010 through August 2012. Following a period of low emissions during January-September 2010 (highlighted in yellow), three periods of increased SO2 flux occurred (a, b, c) and significant escalation was observed during February-March 2012 and May-June 2012 (vertical yellow bars). Annotated areas are approximations of time periods. Courtesy of INGEOMINAS.

Explosive activity in 2012. In late January 2012, while SO2 flux began to increase dramatically (figure 57), explosion signatures (also described as strong degassing events) and multi-events continued to appear in the seismic records. On 8 March an overflight of the summit provided INGEOMINAS scientists a view of ash-covered snow on the E flank and near the crater rim (figure 58); in their monthly report, INGEOMINAS suggested this ash may have fallen during an explosion detected on 22 February 2012.

Figure (see Caption) Figure 58. This photo was taken during a flight past Nevado del Ruiz's active crater at 0705 on 8 March 2012. Viewed from the Azufrado sector (NE of the summit crater), a column of gas was rising to a maximum height of ~1,400 m above the crater. A thin layer of ash was visible on the snow near the crater (in the foreground of the image). Courtesy of INGEOMINAS.

On 29 March authorities raised the alert to Level II (Orange) when LP seismicity underwent a ~100-fold increase and banded tremor persisted (table 3).

Based in part on information captured by webcameras around the volcano (including one in Manizales located 30 km NW of Nevado del Ruiz), INGEOMINAS reported that plume heights had increased significantly in March 2012 (figure 59). Reports from local populations around the volcano also alerted INGEOMINAS of sulfur odors. Residents smelled these odors during March; April, May, and August reports were from Manizales, Lebanon, Palocabildo, and Chinchiná.

Figure (see Caption) Figure 59. (Top) The map of Nevado del Ruiz's geophysical monitoring network includes webcameras, meteorological stations, mudflow stations with acoustic flow sensors, and infrasound. (Bottom) Plot of plume height above the crater as measured from webcameras located near the flanks (including sites Piraña (PIRA), Gualí (GUAL), and Manizales (OVSM)) from January through June 2012. Courtesy of INGEOMINAS.

The national park surrounding the volcano, Los Nevados National Park, closed in April 2012 due to possible ashfall and lahar hazards. The rainy season (March-June) had begun and mass wasting on the steep slopes, especially of remobilized ash, was a major concern. "Most lahars are initiated as dilute, subcritical flows high on volcanic slopes, but quickly increase their volumes as they incorporate sediment along travel paths (Lockwood and Hazlett, 2010)."

On 16 and 19 April 2012, INGEOMINAS observed ash emissions from the summit and on 22 April, Washington VAAC announced possible ash in the steam plume. Volcanic ash was detected later with satellite imagery, spreading ~110 km NE of the summit on 29 May.

Seismicity decreased in early May 2012 to levels observed before the escalation began in February, and fewer explosions and multi-events were recorded. On 3 May authorities lowered the alert to Level III (Yellow). Conditions at Nevado del Ruiz continued to change, however, and when seismicity abruptly increased, the Alert Level was raised to Level II (Orange) on 29 May (table 3, figure 60). That day, explosions from the crater generated ash plumes that dispersed over more than 20 communities located to the WNW, NW, and NNW. Washington VAAC released four notices on 29 May describing ash up to 11 km altitude. News media reported that three primary airports in the region (Manizales, Pereira, and Armenian) collectively canceled ~20 flights that affected ~700 passengers on 29 May.

Figure (see Caption) Figure 60. A seismic record from Nevado del Ruiz starting just prior to 29 May 2012 and ending slightly past noon on 1 June 2012. The notes explain the start of ash emissions (top shaded bar), alert announcement (orange diamond), and intervals of tremor (shaded bars with orange connected lines). Translation of text: Initial pulse of ash emission at 0397 on 29 May. Throughout the seismogram, volcanic tremor is present and in parts, appears as banded tremor that increases in amplitude. Courtesy of INGEOMINAS.

Widespread ashfall in early June 2012 required field maintenance by INGEOMINAS to clear ash from solar panels and equipment (figure 61). Imagery captured by the NASA satellite EO-1 revealed a two-toned summit disclosing partial ash cover over the white summit glacier (figure 62). The seismic station INDERENA, acoustic flow station MOLINOS, and the radio repeater that served Nevado del Ruiz, Tolima, and Santa Izabel volcanoes were disabled due to ash cover. Washington VAAC released advisories regularly until 24 June; ash reached altitudes in the range of ~5.5-7.6 km. Plumes tended to drift N, NW, WNW, and W; however, an ash plume on 8 June drifted ~28 km SE. The range of plume lengths was 28-110 km until a period of quiescence during 25 June-2 July.

Figure (see Caption) Figure 61. Ash covered several solar panels as well as field equipment located near Nevado del Ruiz's W flank in June 2012. Here, at near-equatorial latitude (~5° N), the panels are typically oriented near-horizontal for effective solar exposure which also makes it easy for ash to collect and not wash away. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 62. (Left) This image was taken by the NASA Expedition 23 crew on 23 April 2010, with a Nikon D3S digital camera fitted with an 800 mm lens. A steam plume drifts SW from the summit crater, blending in with the snow-cover. The summit crater is indicated with a black arrow and the neighboring features, Cráter de Olleta and Altas de Piraña correspond with the outlined field of view in yellow in the left image. Note the scale is approximate and there is some skew to this image as it was taken from a shuttle flight as opposed to the orbiting satellite. Courtesy of NASA. (Right) This satellite image of Nevado del Ruiz was taken during significant ash explosions on 6 June 2012. The summit glacier displays the sharp contrast of muted gray on the NW due to ash cover and bright white on the SE where ash had not fallen. The black arrow points to the summit crater and white clouds are concentrated in the NW and SE corners of the image that also partially cover the peak Altas de Piraña. Image courtesy of NASA by Jesse Allen and Robert Simmon using EO-1 Advanced Land Imager data.

On 30 June 2012, seismicity increased and large plumes of ash vented from the summit (figure 63). At 1700 that day, authorities raised the alert to Level I (Red). Local news media reported the preventative evacuation notice provided by the Emergency Committee of Caldas; Caldas is the department of Colombia encompassing Nevado del Ruiz and six districts, 27 municipalities, and the capital, Manizales. An estimated 300 families were ordered to evacuate from the rural zones of districts Chinchiná (30 km WNW), Villamaría (28 km NW), Palestina (40 km WNW), and Manizales (30 km NW) due to both escalated explosions and also the potential for flooding along the rivers Chinchiná and Río Claro. In the Department of Tolima, located S of Caldas there was a recommendation to evacuate 1,500 families in risk zones in eight municipalities.

Figure (see Caption) Figure 63. A snapshot of the seismic record from Nevado del Ruiz on 30 June 2012 and annotated to mark when officials announced the maximum Alert Level (Level I). Colored circles indicate events associated with fracturing (red), gas and fluid movement (yellow), and tremor resulting from gas or ash emissions (blue). Note that time stamps are not included except for the 1740 arrow. Courtesy of INGEOMINAS.

On 2 July 2012, Washington VAAC announced a 7.5-km-wide plume visible in satellite imagery that had drifted ~75 km W. Seismicity was decreasing, however, and that same day, authorities lowered the Alert Level to II (Orange). Airborne ash remained visible in satellite images until 8 July and continued to be observed at low elevations based on webcamera images. Ashfall was reported in Pereira (40 km WSW) on 11 July, and on 31 July a plume of ash and gas was observed rising 300 m above the crater.

Low levels of tremor had been detected in late July and throughout much of August 2012. Seismic swarms were detected on 12 and 13 August (table 3) with ~140 low-magnitude events under 5 km deep concentrated WSW of the Arenas Crater. On 6 August, ashfall was reported in Manizales and Chinchiná; on 12 August there were reports of ash in Manizales and Brisas (50 km SW). Through the end of August, plumes (ranging 200-800 m above the crater) were visible from the summit. Field measurements by INGEOMINAS and remote sensing with OMI determined that SO2 emissions remained high (figure 64) through August and early September. On 5 September 2012 authorities reduced the Alert Level to III (Yellow).

Figure (see Caption) Figure 64. A Nevado del Ruiz SO2 plume was detected by the Ozone Monitoring Instrument (OMI) on NASA's AURA satellite on 9 September 2012 from 1328-1507 (local time), extending well over the Pacific Ocean. The mass of SO2 was 1.28 kt, covering an area of 44,199 km2, and the maximum was 4.23 Dobson Units (DU) at 1331 local time. Courtesy of Simon Carn, Michigan Technological University and Joint Center for Earth Systems Technology, University of Maryland Baltimore County.

Recalling 1985 and additional hazard mitigation efforts. Nevado del Ruiz's most deadly natural disaster was a lahar that, on 13 November 1985, scoured the Lagunillas River (E flank drainage system) and suddenly flooded the towns of Armero, Chinchiná, Mariquita, and Honda (figure 65). Armero was completely destroyed and more than 23,000 residents died. Light ashfall had been reported that day and a seismic network was in place, but no early warning system had been established to initiate evacuations (Lockwood and Hazlett, 2010).

Figure (see Caption) Figure 65. Released in 2007, this hazard map of Nevado del Ruiz is dominated by lahar and pyroclastic flow scenarios. Highest risk areas are shaded red with lower risk areas in yellow; note that the town of Armero (Antiguo Armero, 48 km E of the summit) is in a region of high risk. A topographic assessment augmented with substantial field evidence determined flow paths and inundation probabilities within the major drainages of Gualí, Azufrado, Lagunillas, Recio, and Chinchiná (listed clockwise starting with the NE drainage). Pyroclastic flow, ashfall, and lava inundation were also considered and the radial sectors directed NE attribute hazards to lateral explosions based on crater morphology and geologic mapping of tephra units. Names highlighted in green indicate major towns. Courtesy of INGEOMINAS.

Since 1985, realtime geophysical monitoring greatly increased, including acoustic flow sensors designed to detect impulsive flooding in local drainages. Other advances included mobile gas monitoring (mini-DOAS) that augmented routine geochemical sampling at Nevado del Ruiz and recent hazard map revisions that emphasized inundation scenarios with zoning that clearly communicates areas at highest risk (figure 65). International collaborations with universities and agencies (for example, the University of Wisconsin and the European Union mentioned previously) have focused on mitigation efforts through training and technical resources.

Following the disastrous 1985 lahars, the USGS and the U.S. Office of Foreign Disaster Assistance (OFDA) developed the Volcano Disaster Assistance Program (VDAP) to respond to selected volcanic crises around the world (Ewert and others, 1997). The VDAP mission is to work with international counterparts to reduce fatalities and economic losses in those countries experiencing a volcano emergency. The VDAP website states that "Between crises, VDAP scientists focus on building and improving volcano monitoring systems and conduct joint activities to reduce volcanic risk by improving understanding of volcanic hazards [figure 66]."

Figure (see Caption) Figure 66. The USGS/OFDA Volcano Disaster Assistance Program sent a team of scientists to aid INGEOMINAS and local authorities mitigating risk at Nevado del Ruiz on 28 May 2012. Courtesy of The Columbian.

References. Ewert, J.W., Miller, C.D., Hendley, J.W., and Stauffer, P.H., 1997. Mobile Response Team Saves Lives in Volcano Crises, USGS Fact Sheet: 064-97.

Galle, B. and the NOVAC Team, 2009. NOVAC - A global network for volcanic gas monitoring, 6th Alexander von Humboldt International Conference, Abstract AvH6-34-1, 2010.

Garzón, G., Serna, D., Diago, J., and Morán, C., 2003. Radon soil increases before volcano-tectonic earthquakes in Colombia, Proceedings of ICGG7: 6-7.

Lockwood, J.P., and Hazlett, R.W., 2010. Volcanoes: Global Perspectives, Wiley-Blackwell, Hoboken, NJ, ix, p.539.

Narváez, L.M., Torres, R.A., Gómez, D.M., Cortez, G.P., Cepeda, H.V., and Stix, J., 1997. 'Tornillo'-type seismic signals at Galeras volcano, Colombia, 1992-1993, Journal of Volcanology and Geothermal Research, 77: 159-171.

Salazar, S., Carvajal, C., and Garzón, G., 2003. Radiological geohazard survey in the south east of Manizales city (Colombia), Proceedings of ICGG7: 3-5.

Yamashita, K.M., 1992. Single-Setup Leveling Used to Monitor Vertical Displacement (Tilt) on Cascades Volcanoes, in Ewert, J. and Swanson, D. (Eds.), Monitoring volcanoes; techniques and strategies used by the staff of the Cascades Volcano Observatory, 1980-90, U.S. Geological Survey Bulletin 1966, pp. 143-149.

Information Contacts: Instituto Colombiano de Geologia y Mineria (INGEOMINAS), Volcanological and Seismological Observatory, Avenida 12 Octubre 15-47, Manizales, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); Ozone Monitoring Instrument (OMI), Sulfur Dioxide Group, Joint Center for Earth Systems Technology, University of Maryland Baltimore County (UMBC), 1000 Hilltop Circle, Baltimore, MD 21250, USA (URL: https://so2.gsfc.nasa.gov/); El Colombiano (URL: http://www.elcolombiano.com/); The Columbian (URL: http://www.columbian.com/).


July 2014 (BGVN 39:07) Citation IconCite this Report

Frequent ash plumes during September 2012-July 2013; continuing gas emissions

During September 2012-July 2014 the Servicio Geológico Colombiano (SGC) maintained Alert Level Yellow at Nevado del Ruiz due to elevated SO2 flux, seismicity, and intermittent ash emissions; the Alert Level had been lowered to Yellow on 5 September. No major geophysical changes were noted during this time period.

Gas plumes were frequently visible rising as high as 3,500 m above the summit (figure 67). Minor gas-and-ash plumes occasionally occurred throughout this reporting period, and were often associated with episodes of tremor. Ashfall was reported from areas around the volcano (figure 68), notably on 11 July 2013 when ash reached Manizales (~30 km NW). The Washington Volcanic Ash Advisory Center (VAAC) reported ash plumes visible in satellite images on 10 October 2012 (reaching ~7 km altitude) and 11 July 2013 (reaching ~6 km altitude). A possible ash plume was detected at ~7.6 km altitude on 16 June 2013.

Figure (see Caption) Figure 67. White gas plumes frequently rise 750-3,500 m above the Nevado del Ruiz crater rim, as seen in this webcamera image taken at 0648 on 3 April 2014. The camera location is ~6 km NE of Arenas crater (Piraña station). Courtesy of SGC.
Figure (see Caption) Figure 68. Persistent ashfall challenged the local monitoring systems for Nevado del Ruiz in September 2012. These two stations, a ScanDOAS station Bruma/Azufrado (left) and the GPS station at Gualí (right), were the focus of fieldwork by SGC staff in September. Courtesy of SGC.

SGC reported continuous and elevated SO2 emissions during this reporting period. Gas monitoring included satellite images, field installations (ScanDOAS), and MobileDOAS. ScanDOAS values captured the dramatic increase in SO2 flux during the explosive eruptions of early 2012 (BGVN 37:08). Since September 2012, the maximum daily average frequently exceeded 6,000 tons per day and exceeded 9,500 tons/day three times: twice in June 2013 and once in July 2014. MobileDOAS measurements were collected by the SGC during field campaigns and the values are reported in monthly technical bulletins available online (in Spanish).

Seismicity. Volcano-tectonic earthquakes (VT), long-period earthquakes (LP), and tremor were detected by the monitoring network throughout this reporting period. Earthquakes were detected from the summit glaciers, as well, notably in February 2014. Increased VT seismicity was notable during October 2012 (figure 69), 23-24 February 2013, 13 April-4 May 2013, 5-10 October 2013, 18-27 June 2014, and 29 July 2014 (figure 70). Maximum local magnitudes of VT earthquakes in the range of 1.6-4.4 were detected during this time period at depths of 0.5-13 km.

Figure (see Caption) Figure 69. Seismicity from Nevado del Ruiz during October 2012 was elevated; 2,179 VT earthquakes were located. Two main areas of concentration were located N and NE of the summit (circled in red). Black squares are seismic stations; color coding refers to depth; circle size correlates with earthquake magnitudes. Courtesy of SGC.
Figure (see Caption) Figure 70. Elevated seismicity from Nevado del Ruiz on 29 July 2014 consisted of 746 VT earthquakes detected in a zone ~2 km long SSW of the main crater, Arenas. Red lines correspond to local faults as well as Palestina, the regional, cross-cutting fault trending NE-SW. Depths of earthquakes are correlated to colors in the key as well as magnitudes based on circle size. Courtesy of SGC.

Information Contacts: Servicio Geológico Colombiano (SGC), Volcanological and Seismological Observatory, Avenida 12 Octubre 15-47, Manizales, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).


June 2017 (BGVN 42:06) Citation IconCite this Report

Intermittent ash emissions July 2012-December 2015; increased thermal activity October-December 2015

A February 2012 ash explosion of Colombia's Nevado del Ruiz volcano was the first confirmed ash emission in over 20 years. The broad, glacier-capped volcano has an eruption history documented back 8,600 years, and historical observations since 1570. Notably, a large explosion at night in heavy rain on 13 November 1985 generated large lahars that washed down 11 flank valleys, inundating most severely the town of Armero where over 20,000 residents were killed. It remains the second deadliest volcanic eruption of the 20th century after Mt. Pelee in 1902 killed 28,000.

This report summarizes and concludes the February 2012-April 2014 eruption (BGVN 37:08, 39:07), and then describes details of new activity beginning in November 2014, through December 2015. The volcano is monitored by the Servicio Geologico Colombiano (SGC) and aviation reports are provided by the Washington Volcanic Ash Advisory Center (VAAC).

Summary of activity, November 1985-June 2012. After the large explosions and deadly lahars of November 1985, activity at Ruiz continued with intermittent ash emissions and significant seismic activity through July 1991. Seismicity, deformation, and SO2 emissions have been closely monitored since the 1985 eruption. Between 1991 and February 2012 intermittent high-frequency seismic events (earthquake swarms) were recorded, but no ash emissions were observed. In September 2010, seismicity notably increased in frequency and diversity of event type until early 2012 when fresh ashfall was observed. INGEOMINAS (Instituto Colombiano de Geología y Minería, precursor to SGC) also noted an inflationary trend in the geodetic data from October 2010 through 2011.

A March 2012 overflight by INGEOMINAS noted minor amounts of ash-covered snow on the E flank, which they surmised came from an explosion on 22 February (BGVN 37:08). During March, long-period seismicity underwent a 20-fold increase. SO2 emissions also dramatically increased between March and June 2012. Several ash emissions from the summit were observed during April-June 2012 (BGVN 37:08). An ash plume that rose to 11 km altitude on 29 May caused ashfall in over 20 communities to the NW and closures at three nearby airports. Widespread ashfall during June covered solar panels on field equipment. An EO-1 satellite image from 6 June 2012 shows a plume and significant ashfall around the summit (figure 71).

Figure (see Caption) Figure 71. Satellite image of Nevado del Ruiz taken on 6 June 2012 showing an active ash plume from the Arenas crater and ash deposits NW of the summit. It was acquired by the Advanced Land Imager (ALI) aboard the Earth Observing-1 (EO-1) satellite. Courtesy NASA Earth Observatory.

Summary of activity, July 2012-December 2015. Explosions and seismic tremor with ash emissions continued during July and August 2012. Ashfall was reported within 30 km on numerous occasions. From September 2012 through early July 2013 minor amounts of ashfall were reported a few times each month, mostly in the immediate vicinity of the volcano. After a larger explosion on 11 July 2013, sparse and intermittent ash emissions were reported between August 2013 and April 2014. Between May and October 2014 there were no reports of ash emissions or thermal anomalies.

A significant increase in seismicity occurred during the second week of November 2014, and ash was seen at the summit during an overflight on 19 November. Ash fell in communities within 30 km several times each month through December 2015. Seismic evidence suggesting possible lava dome extrusion first appeared in August 2015, and stronger signals were recorded on 22 October. Thermal anomalies around the summit crater increased in frequency and magnitude during the last three months of 2015.

Activity during July 2012-October 2014. A large ash plume on 30 June 2012 prompted evacuation warnings to several communities within 30 km and closed three nearby airports for the second time within 30 days. On 2 July the Washington VAAC reported a 7.5-km-wide ash plume at 6.1 km altitude drifting 75 km W (BGVN 37:08). Additional VAAC reports were issued on 8, 9, and 10 July for SO2 emissions containing minor volcanic ash. SGC noted that explosions and ash emissions continued throughout the month in spite of a decrease in seismicity. Ashfall was reported near the volcano, and in municipalities in the departments of Caldas (W) and Risaralda (SW), steadily throughout the month.

Tremors associated with continuing gas and ash emissions occurred throughout August 2012; ash plumes were observed rising 200-800 m above the summit crater. During 3-6 August, gas and ash emissions were seen from Manizales (30 km NW) and Chinchiná (30 km WNW). On 12 August, a gas-and-ash plume observed with a webcam rose 1 km above the crater and drifted W, and ashfall was reported in Brisas (50 km SW). A layer of ash was deposited at the Observatorio Vulcanológico y Sismológico de Manizales (OVSM) on 13 August; they also reported ash emissions associated with seismic signals the next evening. Webcams showed gas-and-ash plumes rising 400 m and drifting W and NW during 15-16 August.

Minor amounts of ashfall were reported by SGC in areas around the volcano each month during September 2012 through 11 July 2013 (table 4), when a larger ash emission occurred. A noted increase in seismicity beginning on 13 April 2013 was also reported by SGC. The ash emission on 11 July was captured by the webcam in the Parque Nacional Natural Los Nevados (PNNN) (figure 72), and fine ash fell in Manizales. The Washington VAAC reported the ash plume at 6.1 km altitude. Multispectral imagery showed the plume extending 55 km NW. After 12 July 2013 there were no further reports from the Washington VAAC until December 2014.

Table 4. Ash emission events at Ruiz during September 2012-July 2013. Data compiled from various sources as shown.

Date Event Details Source
06 Sep 2012 Small explosion Small ash emission. SGC Weekly Report, 3-9 Sep 2012
10 Oct 2012 Ash plume 7.3 km altitude, drifting 35 km NW. Washington VAAC
15-16 Nov 2012 Possible ash emission Weather clouds prevented observation, faint thermal anomaly detected. Washington VAAC
10 Dec 2012 Tremor Early morning, gas and ash emissions. SGC Weekly Report, 3-9 Dec (published 11 Dec) 2012
09 Jan 2013 Tremor Ash and gas emission, ashfall reported in the Valle de las Tumbas, W of the summit crater. SGC Weekly Report, 7-13 Jan 2013
16 Jan 2013 Faint ash plume Drifting NE 50 km; hot spot. Washington VAAC
11 Feb 2013 Gas and ash plume Webcam images and visual observation from Observatorio Manizales, 1,600 m above the crater. SGC Monthly Technical Report, February 2013
07-10 Mar 2013 Continuous tremor Gas and ash emissions reported by officials from the Parque Nacional Natural los Nevados (PNNN). SGC Weekly Report, 4-10 Mar 2013.
11-17 Mar 2013 Continuous tremor Gas and ash emissions. SGC Weekly Report, 11-17 Mar 2013
10-30 Apr 2013 Constant tremor Small gas and ash emissions beginning 10 April. SGC Monthly Technical Report, Apr 2013
14 Apr 2013 Gas and ash plume Webcam image of gas and ash plume rose 630 m and drifted NW. INGEOMINAS daily report, 14 Apr 2013
15-21 Apr 2013 Ashfall confirmed Ashfall confirmed near Villahermosa (Tolima), 30 km NE. SGC Weekly Report, 15-21 Apr 2013
22 and 27 May 2013 Ash and gas emissions Confirmed by seismic signals as well as the webcams. SGC Monthly Report, May 2013
Jun 2013 Low-energy tremors Associated with gas and ash emissions, pulses of low energy. SGC Monthly Technical Report, June 2013
11 Jul 2013 Small ash emission Confirmed by OVSM webcams, and officials at PNNN. Ashfall reported in Valle de las Tumbas and Manizales. SGC Monthly Technical Report, July 2013; SGC Weekly Report 8-14 July 2013; Washington VAAC
Figure (see Caption) Figure 72. Ash emission at Ruiz on 11 July 2013 at 1143. The column of gases and gray ash stands out among the white clouds. Photo by Julián Peña, courtesy of SGC (Informe-Technico, July 2013).

Evidence for ash emissions between August 2013 and April 2014 is sparse and intermittent. The SGC Monthly reports during this time mention pulses of low-energy tremor associated with emissions of gases, steam, and small amounts of ash every month except November, when they reported only steam and gas, but no specific dates are given. SGC's Technical Information Monthly reports mention occasional grayish coloration, suggesting ash in the gas-and-steam plumes during August-October 2013. Tremors associated with small amounts of ash and grayish coloration in the plumes are again noted from January through April 2014 without describing specific events.

The weekly activity reports issued by SGC make no mention of ash from August through November 2013. They note in weekly reports for 2-8 and 9-15 December that gray emissions possibly associated with ash in plumes of mostly water vapor and gases were observed. During the week of 16-23 December they recorded low-energy tremors associated with the output of small amounts of ash, which were reported in trace quantities in Manizales. In their 31 December 2013-6 January 2014 and 10-16 February 2014 weekly reports they noted the occurrence of tremors associated with ash and gas. There is no mention of ash in their March or April 2014 weekly reports. There is also no mention of ash emission in SGC monthly reports during May-October 2014. The MIROVA thermal anomaly data do show minor thermal anomalies in latest August and more persistent anomalies at the beginning of October 2014 (figure 73) prior to the reports of ash emissions during November.

Figure (see Caption) Figure 73. MIROVA signal of MODIS data for the year ending on 15 May 2015. Persistent thermal anomalies are present between late October 2014 and mid-April 2015. Courtesy of the MIROVA project supported by the Centre for Volcanic Risk of the Italian Civil Protection Department via SGC (Informe de Actividad, April 2015).

Activity during November 2014-December 2015. A significant change in seismicity occurred beginning in the second week of November 2014. There was an increase in the number of long-period (LP) earthquakes, pulses of volcanic tremor, and several periods of continuous tremor (lasting for hours or even days) associated with fluid movement, and with emissions of gas and ash (table 5). Several of these periods were preceded by an LP event. The first significant pulse of volcanic tremor began on the evening of 18 November following an LP event and lasted more than 12 hours.

Table 5. Periods of continuous tremor associated with ash emissions at Ruiz during November 2014. Some of the tremor episodes were preceded by long-period (LP) events. Courtesy of SGC (Informe de Actividad, November 2014).

Date Time (local) Duration LP event (local time)
18 Nov 2014 1918 More than 12 hours 1918
20 Nov 2014 0224 More than 20 hours 0223
21 Nov 2014 0108 More than 4 hours --
28 Nov 2014 1310 More than 4 hours 1305
28 Nov 2014 1941 More than 8 hours --
29 Nov 2014 1307 More than 48 hours 1305

The Unidad Nacional de Gestion de Riesgo de Desastres (UNGRD, National Disaster Risk Management Unit) coordinated an overflight during 19-21 November 2014 and observed fresh ash deposits on the S flank. Ash emissions were also verified in satellite imagery (figure 74) and by reports from nearby communities. The ash dispersed generally SE and SW during 18-21 November. Ash was again observed on the N side of the Arenas crater on 29 November in the early morning after a lengthy period of continuous tremor was recorded the previous day (see table 5).

Figure (see Caption) Figure 74. Image of Ruiz on 24 November 2014 taken by the OLI-TIRS sensor on the Landsat 8 Satellite at 1018 local time. Ash deposits are dispersed SE and SW of the summit crater, and the steam plume is drifting W. Courtesy of SGC (Informe de Actividad, November 2014).

During the second half of December 2014, SGC reported significant concentrations of ash in the emissions that were associated with continuous tremor episodes. On 15 December seismic signals indicating ash emissions were detected, and then confirmed by a local webcam and nearby residents. The Washington VAAC also noted an ash emission based on a pilot observation extending 16 km S at 7.6 km altitude. The next day they reported a narrow plume of minor volcanic ash extending 22 km SW of the summit at 6.1 km altitude. On 18 and 19 December the Washington VAAC reported ash plumes to altitudes of 7.9 and 9.1 km, respectively, that drifted SSW and dissipated within a few hours. A faint thermal anomaly was also detected. A satellite image taken on 26 December 2014 clearly shows ash deposits in nearly all directions from the Arenas crater (figure 75). Ashfall was reported during this time in the Caldas (W) and Risaralda (SW) departments.

Figure (see Caption) Figure 75. An ASTER image from the OLI-TIRS Sensor on the Landsat 8 satellite taken on 26 December 2014 of Ruiz (N is to the top) showing fresh ash deposits covering the summit glacier in nearly all directions. Courtesy of SGC (Informe de Actividad, December 2014).

According to the news source Prensa Latina, increased ash emissions at Ruiz prompted closure of the La Nubia airport (22 km NW) on 7 January 2015. On 14 January, the Washington VAAC reported an ash plume visible in satellite imagery extending 16 km SW of the summit at 6.7 km altitude. SGC reported seven episodes of continuous tremor on 4, 7, 14, 24, 26, 28, and 29 January, almost all of which were associated with ash emissions (figures 76). Ashfall was reported several times after these episodes in the Eje Cafetero area to the W of Ruiz.

Figure (see Caption) Figure 76. Ash emissions on six different dates during January 2015 at Ruiz. Photographs taken by the webcam located in the Azufrado sector (NW). Courtesy of SGC (Informe de Actividad, January 2015).

Occasional minor ash emissions were reported during February 2015 during periods of continuous tremor, but most of the emissions were steam and gas. On 9 February, ashfall was reported in El Libano (29 km E), El Oso (10 km SE), and Murillo (17 km E). Although seismic tremors were diminished during March from the previous month, emissions associated with these tremors contained gases and minor amounts of ash from 8 March through the end of the month. Ashfall was reported after a tremor in the evening on 8 March by personnel from the Parque Nacional Natural Los Nevados (PNNN), the Observatorio Vulcanológico y Sismológico de Manizales (OVSM), and from the municipalities of Manizales and Villamaria (27 km NW).

An increase in several types of seismicity was observed by SGC during April 2015. Volcanic tremor, associated with gas and ash emissions, were confirmed through photographs taken by the webcams (figure 77), and by officials at PNNN and SGC. Ashfall was reported on 20 April in the municipalities of Manizales and Villamaría. The Washington VAAC reported a small puff of gas and minor amounts of ash visible in satellite imagery on 22 April at 7.3 km altitude drifting W about 40 km before dissipating. The MIROVA signal from the MODIS thermal anomaly data shows persistent thermal activity from late October 2014 through mid-April 2015 (figure 73).

Figure (see Caption) Figure 77. Plumes of ash-and-gas from Ruiz during April 2015. Confirmed ash emissions were observed on 9, 22, 27, and 29 April. Courtesy of SGC (Informe de Actividad, April 2015).

Ash emissions were photographed by the webcams located in the Azufrado and Cerro Guali regions on at least eleven dates during May 2015. The Washington VAAC reported possible emissions on 19 and 26 May, but extensive weather clouds prevented satellite observations. Most of the frequent episodes of volcanic tremor during June were also associated with ash emissions which were photographed at least six times during the month. The Observatory at Manizales reported ash moving WNW on 6 June at about 800 m above the summit; weather clouds obscured satellite observations by the Washington VAAC.

A significant increase in ashfall was reported during July 2015 (figure 78), including in the regions of Caldas, Tolima, and Risaralda, as well as by officials in the Park (PNNN). The Observatory at Manizales (OVSM) reported an ash plume on 6 July at about 7.3 km altitude, but it was not observed in satellite data due to weather. The Washington VAAC noted ash emissions visible in satellite data and the webcam on 13 July, with a plume at 7 km altitude drifting NW a few tens of kilometers before dissipating. OVSM reported plumes at about 6 km moving S and W during 18-20 July. Seismic signals indicating emissions were reported on 23 July and observed in the webcam, according to the Washington VAAC. SGC noted seismic tremors and a plume on the morning of 26 July that rose to 3 km above the summit (8.2 km altitude) (figure 79); near summit-level emissions were also observed via the webcam on 26 and 27 July. Seismic data indicated continued occasional bursts of ash drifting W to WSW during the next few days. Ashfall was reported downwind in the municipalities of Chinchina (33 km NW), Palestina (35 km NW), Santa Rosa de Cabal (33 km W), Dosquebradas (40 km WSW), and Pereira (40 km WSW). A bright thermal anomaly was reported in satellite imagery on 31 July, but no ash was observed.

Figure (see Caption) Figure 78. Gas, steam, and ash plumes from the Arenas crater at Ruiz during July 2015. Photographs captured by the cameras located in the area of Azufrado, Cerro Gualí, and in the OVSM. Courtesy of SGC (Informe de Actividad, July 2015).
Figure (see Caption) Figure 79. Seismic and visual images of tremors that produced ash emissions at Ruiz between 0800 and 1559 on 26 July 2015. The digital seismogram and spectrogram are from station BIS (2 km W of Arenas Crater) and show a characteristic spasmodic tremor (1, 2, and 3) that was associated with ash emissions recorded on the Piranha-Azufrado webcamera in the lower images. Courtesy of SGC (Informe de Actividad, July 2015).

SGC reported greater instability at Ruiz compared with previous months during August 2015. Seismicity related to fracturing and fluid flow both increased during the month. Energy levels for spasmodic tremor related to gas and ash emissions were also generally higher. The Washington VAAC reported ash visible in satellite imagery on 6 August at 7.3 km altitude moving NW as far as 20 km for about 10 hours before dissipating. They noted another possible plume with minor ash on 12 August at 6.7 km drifting 55 km NW from the summit. Ashfall was reported on 23 August from officials of PNNN and residents of Pereira. A brief emission containing minor ash on 28 August, observed in a webcam, was reported by the Washington VAAC as extending about 35 km W. Ongoing emissions rising a few hundred meters above the summit with occasional small bursts of ash continued for the next two days.

The tremor event on 31 August 2015 was the largest since 18 November 2014; ashfall affected numerous cities and municipalities, including Manizales (30 km NW) (with the largest particle sizes towards the E side of the city), La Linda, La Cabaña (36 km NW), and trace amounts in Santagueda (40 km NW), Arauca (48 km NW), Kilómetro 41, Villamaría (27 km NW), Chinchiná, Palestina, and Neira (36 km NW) (figure 80). A news article reported that the La Nubia airport closed that day due to ash emissions. Most ash emissions during the month affected the regions of Caldas and Risaralda NW of the volcano.

Figure (see Caption) Figure 80. Ashfall was recorded in a number of cities during the 31 August 2015 emission event at Ruiz. The four left images are from the city of Manizales. The six right images are from different towns in the department of Caldas. Courtesy of SGC (Informe de Actividad, August 2015).

The Washington VAAC issued advisory reports on 3, 12-15, 17, 23-24, 27, and 29-30 September 2015. Most reports were based on observations from the webcams near the volcano and/or seismic activity, but many events were not visible in satellite imagery due to weather clouds. Plume altitudes ranged from 5.5 to 7.9 km. Incandescence observed in a webcam on 4 September was followed by a high-energy tremor. The ash plumes reported by the Washington VAAC on 12 and 13 September rose to 7.9 km and drifted in several directions. Ash was moving to the NW below 5.2 km and extended for over 90 km; between 5.2 and 7.9 km altitude it extended about 80 km SW. Ongoing emissions with small bursts of ash continued through 15 September with a new emission to 7.6 km around 1600 that day.

The OVSM reported a strong seismic signal at 0728 on 17 September, but weather clouds blocked observation from satellite imagery of the potential ash plume. The largest tremor of the month occurred in the afternoon of 18 September and ash emissions were verified in the webcams as well as by SGO officials doing fieldwork in the area; ash emissions were also observed in the webcam on 19 September at 1556. SGO reported a seismic event on 22 September that produced water-vapor, gas, and ash plumes that rose 2 km above the crater and drifted mainly NW. An ash plume was confirmed by the Washington VAAC in a satellite image on 27 September extending about 70 km WNW at 6.1 km altitude. An advisory issued on 29 September noted ash to 8.5 km within 16 km of the summit. SGO noted that the 29 September emissions were observed both E and W of the volcano.

The Washington VAAC confirmed continuous ash emissions on 5 October 2015 at 7 km altitude extending about 25 km W of the summit. A gas, steam, and ash plume rose 1.7 km and drifted NW on 8 October. Another report of volcanic ash early on 9 October was not visible in satellite imagery, although a thermal anomaly persisted and seismicity was elevated. A small ash emission was spotted in imagery data drifting WNW late on 9 October. A gas, steam, and ash plume rose 1.8 km and drifted NW on 17 October. A discrete emission of ash rose to 9.1 km altitude on 22 October and drifted N. SGO reported ash emissions observed in webcams on 26 October, but weather clouds prevented satellite observation by the Washington VAAC. A gas, steam, and ash plume rose 1.7 km and drifted NW on 30 October.

SGC first noticed an unusual pattern of seismicity known as a "drumbeat" signal, for which they issued a special report on 20 August 2015. The "drumbeat" signal is characterized by discrete episodes of short duration (about 30 minutes each) that repeat at regular time intervals and show similar waveforms and energy. They are interpreted by volcanologists to represent phenomena associated with the ascent of high-viscosity magma to the surface and thus are an indicator of near-surface extrusion or dome building. SGC recorded the same signal on 8 September, and then again on 22 October (figure 81). Thermal anomalies near the Arenas crater were observed by SGO on 26, 28, and 30 September, and were again recorded on 7, 9, and 10 October 2015.

Figure (see Caption) Figure 81. Episodes of seismic "drumbeats" at Ruiz recorded on 22 October 2015. The top box is the vertical component seismic record from station BIS, the larger yellow shaded box highlights the entire 'drumbeat' episode. The seismogram from the OLLETA station (lower left) shows a clearer view of the first episode (1). The lower right images show details of the signal at three different time intervals highlighted in smaller boxes in the top image. This signal is interpreted to represent phenomena associated with the ascent of high-viscosity magma to the surface and thus are an indicator of near-surface extrusion or dome building over the emission conduit. Courtesy of SGC (Informe de Actividad, October 2015).

Seismic activity decreased slightly during November 2015, but there still were episodes of volcanic tremor associated with gas and ash emissions that were recorded by the webcams and personnel at PNNN. Continuous tremor signal was recorded on 1 and 4 November. The "drumbeat" signal was again briefly recorded on 13 November. Thermal anomalies increased in frequency and were observed on 4, 18, 20, 22, 26, and 27 November. SGC confirmed ash emissions on 5, 10, 14, 27, and 29 November. The Washington VAAC reported an ash plume on 14 November at 6.4 km altitude moving SW. SGC captured images of the ash plume from two different webcams (figure 82).

Figure (see Caption) Figure 82. Photographs of the ash emission at Ruiz of 14 November 2015 at 0537 from two different webcams. Top image is from the Azufrado webcam (5 km NE) and the lower image is from the Pitayo webcam. Courtesy of SGC (Informe de Actividad, November 2015).

Thermal alerts captured by the University of Hawai'i's MODVOLC system appeared in December 2015 for the first time in several years. They were recorded on 3, 22, 26, and 31 December. Additionally, the MIROVA thermal anomaly system showed significant increases in anomalies at Ruiz during the last three months of 2015 (figure 83).

Figure (see Caption) Figure 83. MIROVA data for the year ending 2 January 2016 showing the substantial increase in frequency and magnitude of thermal anomalies at Ruiz during the last three months of 2015. Courtesy of MIROVA via SGC (Informe de Actividad, December 2015).

Minor episodes of volcanic tremor with ash emissions were reported by SGC during the first two weeks of December 2015. A significant volcanic tremor with ash emissions occurred on 20 December, and ashfall was reported by SGC officials, PNNN personnel, and residents near the volcano and in the city of Manizales. The Washington VAAC noted the ash plume at 6.1 km altitude with 25 km of the summit. A gas, steam and ash plume rose 1.7 km and drifted NW on 28 December.

Sulfur Dioxide emissions, June 2012-2015. Persistent, large SO2 plumes were captured from Ruiz many times during June 2012-December 2015 (figure 84 and 85). Every month during this period the OMI (Ozone Measuring Instrument) on the Aura satellite recorded days with SO2 emissions exceeding 2 DU (Dobson Units); many months had more than half of the recording days with values > 2 DU. Dobson Units are the number of molecules in a square centimeter of the atmosphere. If you were to compress all of the sulfur dioxide in a column of the atmosphere into a flat layer at standard temperature and pressure, one Dobson Unit would be 0.01 millimeters thick and contain 0.0285 grams of SO2 per square meter.

Figure (see Caption) Figure 84. Select Aura/OMI images of SO2 plumes from Ruiz, 2012-2013. Top left: 14 June 2012, the SO2 plume drifts NW. Top right: 18 August 2012, the SO2 plume from Ruiz drifts W. An SO2 plume is also visible drifting W from Ecuador's Cotopaxi in the lower left corner of the image. Bottom left: A 10.26 DU (Dobson Unit) SO2 plume sits directly over Ruiz on 7 December 2012. Bottom right: The SO2 plume drifts south on 19 December 2013. See text above for description of Dobson Units. Courtesy of NASA Goddard Space Flight Center (NASA/GSFC).
Figure (see Caption) Figure 85. Select Aura/OMI images of SO2 plumes from Ruiz, 2014-2015. Top left: On 3 February 2014 an SO2 plume from Ruiz drifts due W while another plume drifts NE from Guagua Pichincha in northern Ecuador. Top right: A 24 September 2014 SO2 plume drifts NW from Ruiz as far as the coastline. Bottom left: On 5 March 2015, a plume drifts slightly W from Ruiz. Bottom right: A W-drifting SO2 plume from Ruiz on 4 October 2015 is visible along with W-drifting plumes from both Cotopaxi and Tungurahua in Ecuador. Courtesy of NASA/GSFC.

Information Contacts: Servicio Geologico Colombiano (SGC), Observatorio Vulcanologico Y Sismologico Manizales, Diagonal 53 N0. 34 - 53 - Bogotá D.C. Colombia (URL: http://www2.sgc.gov.co/Manizales.aspx); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Prensa Latina, Agencia Informativa Latinoamericana (URL: http://www.plenglish.com/).


December 2019 (BGVN 44:12) Citation IconCite this Report

Intermittent ash plumes with significant gas and steam emissions during January 2016-December 2017

Nevado del Ruiz is a glaciated volcano in Colombia (figure 86). It is known for the 13 November 1985 eruption that produced an ash plume and associated pyroclastic flows onto the glacier, triggering a lahar that approximately 25,000 people in the towns of Armero (46 km west) and Chinchiná (34 km east). Since 1985 activity has intermittently occurred at the Arenas crater. The eruption that began on 18 November 2014 included ash plumes dominantly dispersed to the NW of Arenas crater (BGVN 42:06). This bulletin summarizes activity during January 2016 through December 2017 and is based on reports by Servicio Geologico Colombiano and Observatorio Vulcanológico y Sismológico de Manizales, Washington Volcanic Ash Advisory Center (VAAC) notices, and satellite data.

Figure (see Caption) Figure 86. A satellite image of Nevado del Ruiz showing the location of the active Arenas crater. September 2019 Monthly Mosaic image copyright Planet Labs 2019.

Activity during 2016. Throughout January 2016 ash and steam plumes were observed reaching up to a few kilometers. Significant water vapor and volcanic gases, especially SO2, were detected throughout the month. Thermal anomalies were detected in the crater on the 27th and 31st. Significant water vapor and volcanic gas plumes, in particular SO2, were frequently detected by the SCAN DOAS (Differential Optical Absorption Spectroscopy) station and satellite data (figure 87). A M3.2 earthquake was felt in the area on 18 January. Similar activity continued through February with notable ash plumes up to 1 km, and a M3.6 earthquake was felt on the 6th. Ash and gas-and-steam plumes were reported throughout March with a maximum of 3.5 km on the 31st (figure 88). Significant water vapor and gas plumes continued from the Arenas crater throughout the month, and a thermal anomaly was noted on the 28th. An increase in seismicity was reported on the 29th.

Figure (see Caption) Figure 87. Examples of SO2 plumes from Nevado del Ruiz detected by the Aura/OMI instrument on 10, 26, and 31 January 2019. Courtesy of Goddard Space Flight Center.
Figure (see Caption) Figure 88. Ash plumes at Nevado del Ruiz during March. Webcam images courtesy of Servicio Geologico Colombiano, various 2016 reports.

The activity continued into April with a M 3.0 earthquake felt by nearby inhabitants on the 8th, an increase in seismicity reported in the week of 12-18, and another significant increase on the 28th with earthquakes felt around Manizales. Thermal anomalies were noted during 12-18 April with the largest on the 16th. Ash plumes continued through the month as well as significant steam-and-gas plumes. Ashfall was reported in Murillo on the 29th.

The elevated activity continued through May with significant steam plumes up to 1.7 km above the crater during the week of 10-16. Thermal anomalies were reported on the 11th and 12th. Steam, gas, and ash plumes reached 2.5 km above the crater and dispersed to the W and NW. Ashfall was reported in La Florida on the 20th (figure 89) and multiple ash plumes on the 22nd reached 2.5 km and resulted in the closure of the La Nubia airport in Manizales. Ash and gas-and-steam emission continued during June (figure 90).

Figure (see Caption) Figure 89. Ash plumes at Nevado del Ruiz on 17, 18, and 20 May 2016 with fine ash deposited on a car in La Florida, Manizales on the 20th. Webcams located in the NE Guali sector of the volcano, courtesy of Servicio Geologico Colombiano 20 May 2016 report.
Figure (see Caption) Figure 90. Examples of gas-and-steam and ash plumes at Nevado del Ruiz during June and July 2016. Courtesy of Servicio Geologico Colombiano (7 July 2016 report).

Similar activity was reported in July with gas-and-steam and ash plumes often dispersing to the NW and W. Ashfall was reported to the NW on 16 July (figure 91). Drumbeat seismicity was detected on 13, 15, 16, and 17 July, with two hours on the 16th being the longest duration episode do far. Drumbeat seismicity was noted by SGC as indicating dome growth. Significant water vapor and gas emissions continued through August. Ash plumes were reported through the month with plumes up to 1.3 km above the crater on 28 and 2.3 km on 29. Similar activity was reported through September as well as a thermal anomaly and ash deposition apparent in satellite data (figure 92). Drumbeat seismicity was noted again on the 17th.

Figure (see Caption) Figure 91. The location of ashfall resulting from an explosion at Nevado del Ruiz on 16 July 2016 and a sample of the ash under a microscope. The ash is composed of lithics, plagioclase and pyroxene crystals, and minor volcanic glass. Courtesy of Servicio Geologico Colombiano (16 July 2016 report).
Figure (see Caption) Figure 92. This Sentinel-2 thermal infrared satellite image shows elevated temperatures in the Nevado del Ruiz Arenas crater (yellow and orange) on 16 September 2016. Ash deposits are also visible to the NW of the crater. In this image blue is snow and ice. False color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

During the week of 4-10 October it was noted that activity consisting of regular ash plumes had been ongoing for 22 months. Ash plumes continued with reported plumes reaching 2.5 above the crater throughout October (figure 93), accompanied by significant steam and water vapor emissions. A M 4.4 earthquake was felt nearby on the 7th. Similar activity continued through November and December 2016 with plumes consisting of gas and steam, and sometimes ash reaching 2 km above the crater.

Figure (see Caption) Figure 93. An ash plume rising above Nevado del Ruiz on 27 October 2016. Courtesy of Servicio Geologico Colombiano.

Activity during 2017. Significant steam and gas emissions, especially SO2, continued into early 2017. Ash plumes detected through seismicity were confirmed in webcam images and through local reports; the plumes reached a maximum height of 2.5 km above the volcano on the 6th (figure 94). Drumbeat seismicity was recorded during 3-9, and on 22 January. Inflation was detected early in the month and several thermal anomalies were noted.

Intermittent deformation continued into February. Significant steam-and-gas emissions continued with intermittent ash plumes reaching 1.5-2 km above the volcano. Thermal anomalies were noted throughout the month and there was a significant increase in seismicity during 23-26 February.

Figure (see Caption) Figure 94. Ash plumes at Nevado del Ruiz on 6 January 2017. Courtesy of Servicio Geologico Colombiano.

Thermal anomalies continued to be detected through March. Ash plumes continued to be observed and recorded in seismicity and maximum heights of 2 km above the volcano were noted. Deflation continued after the intermittent inflation the previous month. On 10-11 April a period of short-duration and very low-energy drumbeat seismicity was recorded. Significant gas and steam emission continued through April with intermittent ash plumes reaching 1.5 km above the volcano. Thermal anomalies were detected early in the month.

Unrest continued through May with elevated seismicity, significant steam-and-gas emissions, and ash plumes reaching 1.7 km above the crater. Five episodes of drumbeat seismicity were recorded on 29 May and intermittent deformation continued. There were no available reports for June and July.

Variable seismicity was recorded during August and deflation was measured in the first week. Gas-and-steam plumes were observed rising to 850 m above the crater on the 3rd, and 450 m later in the month. A thermal anomaly was noted on the 14th. There were no available reports for September through December.

On 18 December 2017 the Washington VAAC issued an advisory for an ash plume to 6 km that was moving west and dispersing. The plume was described as a "thin veil of volcanic ash and gasses" that was seen in visible satellite imagery, NOAA/CIMSS, and supported by webcam imagery.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html); Observatorio Vulcanológico y Sismológico de Manizales (URL: https://www.facebook.com/ovsmanizales); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


January 2020 (BGVN 45:01) Citation IconCite this Report

Intermittent ash, gas-and-steam, and SO2 plumes, and thermal anomalies during January 2018-December 2019

Nevado del Ruiz is a glaciated stratovolcano located in Colombia. It is most known for the eruption on 13 November 1985 that produced an ash plume and pyroclastic flows onto the glacier, triggering a lahar and killing approximately 25,000 people in the towns of Armero (46 km W) and Chinchiná (34 km E). Since the September 1985-July 1991 eruption, volcanism has occurred dominantly at the Arenas crater, with eruptive periods during February 2012-July 2013 and November 2014-May 2017 (BGVN 42:06 and 44:12). The previous eruption included ash and gas-and-steam plumes, ashfall, and thermal anomalies through May 2017, after which no clear observations of ongoing activity were available until an ash plume was seen in satellite and webcam images on 18 December 2017. This report provides data and observations from January 2018 through December 2019 using information primarily from reports by the Servicio Geologico Colombiano and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and various satellite data.

Summary of activity during December 2017-December 2019. Although data is incomplete, the current eruptive period is considered to have begun with the emission of an ash plume on 18 December 2017. The Washington VAAC issued an advisory that day for an ash plume to 6 km that was moving west and dispersing, further describing it as a "thin veil of volcanic ash and gasses" that was seen in visible satellite imagery, NOAA/CIMSS, and supported by webcam imagery.

Reports of significant ash plumes visible in satellite imagery were infrequent in 2018 and 2019, with a few notable pulses in July 2018, February-March 2019, and August-September 2019 (figure 95). Sentinel-2 thermal satellite data in comparison with Suomi NPP/VIIRS sensor data, and the MODVOLC algorithm for MODIS data registered infrared thermal hotspots intermittently throughout 2018 to 2019 with more frequent anomalies during January-March 2018, August 2018, October 2018-February 2019, and November-December 2019; observations during March-June of each year were low. Identification of SO2 emissions were frequent and consistent during all of 2018-2019 (figure 96).

Figure (see Caption) Figure 95. Timeline summary of observed activity at Nevado del Ruiz from January 2018 through December 2019. VAAC reports typically indicate a significant ash plume. Satellite-based SO2 data is variable with respect to volume of emitted gas, but reflects a point source at the volcano. For Sentinel-2, MODVOLC, and VIIRS data, the dates indicated represents detected thermal anomalies. White areas indicate no activity was observed, which may also be due to meteoric clouds. Data courtesy of Washington VAAC, NASA Goddard Space Flight Center, Sentinel Hub Playground, HIGP, and NASA Worldview using the "Fire and Thermal Anomalies" layer.
Figure (see Caption) Figure 96. Examples of SO2 plumes from Nevado del Ruiz detected by the Aura/OMI instrument during 12 May (top left), 7 October (top middle), and 29 November 2018 (top right) and 9 January (bottom left), 30 March (bottom middle), and 6 October 2019 (bottom right). Courtesy of NASA Goddard Space Flight Center.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows weak thermal anomalies within 5 km of the summit occurring dominantly between October 2018 through March 2019 (figure 97). Between April and October 2019, the number of thermal anomalies was low, registering eight during this time. The number of thermal signatures increased at the beginning of November 2019 and continued through the rest of 2019.

Figure (see Caption) Figure 97. Weak thermal anomalies at Nevado del Ruiz for 25 September 2018 through December 2019 as recorded by the MIROVA system (log radiative power) occurred mostly during December 2018 through March 2019. Activity was low during April to October 2019 with renewed signatures in November 2019. Courtesy of MIROVA.

Seismicity that occurred during 2018-2019 was located mainly in the Arenas crater and consisted of low-frequency (LF) and very low-frequency (VLF) earthquakes and volcanic tremors, many of which were associated with minor gas-and-steam and ash emissions confirmed through webcams. The number of earthquakes reported by SGC fluctuated each week, but the energy remained relatively consistent. The highest magnitude earthquake that occurred during 2018 was on 26 October reaching 3.1 ML (local magnitude) and during 2019 the largest was 2.8 ML on 21 April.

Activity during 2018. Throughout 2018, gas-and-steam plumes, mostly composed of water vapor and sulfur dioxide frequently occurred, rising to a maximum of 2.2 km above the Arenas crater on 24 March. Weak thermal anomalies were seen intermittently in thermal satellite imagery from Sentinel-2 and NASA Worldview during 4 January through March and September to December (figure 98). Activity during March to April 2018 was relatively low and consisted dominantly of gas-and-steam emissions, low-energy seismicity, and intermittent thermal anomalies. Between 9 May and 5 August, no thermal signatures were detected.

Figure (see Caption) Figure 98. Sentinel-2 thermal satellite imagery detected thermal anomalies (bright yellow-orange) within the Arenas crater at Nevado del Ruiz that were mostly visible during the beginning and last months of 2018. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

Ash plumes were seen in GOES-EAST satellite imagery, through webcams, and by SGC personnel. The first ash plume of 2018 occurred on 21 April at 0800, six days after NASA Worldview detected a thermal anomaly within the Arenas crater. The plume rose 6 km altitude and drifted NW as seen in GOES-EAST satellite imagery and reported by the Washington VAAC. Weak gas-and-steam and ash emissions were confirmed by webcams on 22 July, associated with a volcanic tremor. On 11 August 2018, another ash plume was reported in a VAAC notice rising 6.7 km altitude drifting W. During the week of 21 August, SGC reported that seismicity in the Arenas crater was associated with minor gas-and-steam and ash emissions, as confirmed by webcams.

The number of ash plumes increased during September (figure 99), one of which reached a maximum altitude of 7.3 km on 2 September. On 5 September, a continuous volcanic tremor occurred and was accompanied by an ash plume rising 7 km altitude drifting W, according to a Washington VAAC report. Ashfall was observed during the week of 11 September in Manizales (30 km NW) and Villamaría (27 km NW). A new volcanic tremor occurred on 15 September and was accompanied by various ash emissions reaching 1.4 km above the crater and drifting NW as confirmed by PNNN, inhabitants within the vicinity of the volcano, and the Washington VAAC. Seismicity continuing into the weeks of 25 September and 2 October was also accompanied by ash emissions, rising to an altitude of 1.4 km above the crater on 22 September. The number of reported gas-and-steam and ash emissions decreased after September; ash emissions were reported by SGC on 19, 22, 26, and 31 October, 6, 9, and 17 November, and 14 December.

Figure (see Caption) Figure 99. Webcam images of gas-and-steam and ash plumes rising from Nevado del Ruiz during 2018. Courtesy of Servicio Geologico Colombiano.

Activity during 2019. Gas-and-steam and ash emissions continued intermittently through 2019, with an increased number of ash emissions compared to the previous year. Infrared hotspots were detected in Sentinel-2 satellite imagery primarily during January-February 2019 and December 2019, often accompanied by gas-and-steam emissions (figure 100). An ash plume was seen in GOES-EAST satellite imagery on 2 January 2019, rising to an altitude of 5.8 km and drifting NW, according to a Washington VAAC report. On 7 January, ashfall in Manizales and Villamaría was observed. A thermal hotspot was detected in multispectral imagery, according to a Washington VAAC report on 29 January. Slight ground deformation was observed by GNSS and electronic inclinometers during the weeks of 29 January and 10 September. Volcanism was relatively low during February to March and consisted of mostly gas-and-steam emissions and rare ash plumes; these ash emissions were reported on 2 and 9 February and 16 March by the Washington VAAC rising between 5.8-6.7 km altitude. Gas-and-steam emission were detected on 6 and 17 February and 17 and 21 March.

Figure (see Caption) Figure 100. Sentinel-2 thermal satellite imagery detected thermal anomalies (bright yellow-orange) mostly visible within the Arenas crater at Nevado del Ruiz during the last three months of 2019 and were accompanied by gas-and-steam emissions. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

The number of ash emissions detected in satellite imagery increased after March, occurring on 4, 7, 16, 17-19, and 23-26 April and 2 and 4-5 May. Ash plumes were detected on 27 June, 4, 7, 8, and 29 July, 1 August, and on 19, 29, and 30 September. Los Nevados National Natural Park (PNNN) personnel reported that the ash plume on 8 July was accompanied by gas-and-steam emissions and a continuous tremor occurring at 0722 (figure 101). These emissions rose 450 m above the crater and drifted W. On 29 September, a tremor associated with an ash plume occurred at 2353. The ash plume rose to a maximum altitude of 8.5 km drifted NW, resulting in ashfall confirmed by PNNN, GOES-EAST satellite imagery, and SGC personnel in the field.

Seismicity increased during the week of 1 October compared to the previous week, which was accompanied by several gas-and-steam and ash emissions rising 1 km altitude drifting NW observed by webcams, PNNN personnel, and GOES-EAST satellite imagery. An ash plume rising 7 km altitude drifting NW on 4 October resulted in fine ashfall in Manizales. Ash plumes rose to an altitude of 7.3 km drifting N on 5, 9, and 16 October and was seen in the GOES-EAST satellite according to Washington VAAC notices. Ash emissions were observed frequently during November; 11 Washington VAAC notices, the most for any month during 2019, reported emissions ranging 5.8 to 7 km altitude drifting in different directions. Gas-and-steam plumes rose to a maximum of 2.4 km above the crater during 14 and 30 November. The number of reported emissions decreased during December with one ash emission observed on 4 December.

Figure (see Caption) Figure 101. Webcam images of gas-and-steam and ash plumes rising from Nevado del Ruiz during 2019. Courtesy of Servicio Geologico Colombiano.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).


August 2020 (BGVN 45:08) Citation IconCite this Report

Lava dome confirmed inside Arenas crater; intermittent thermal anomalies and ash emissions, January-June 2020

Colombia’s broad, glacier-capped Nevado del Ruiz has an eruption history documented back 8,600 years, and historical observations since 1570. It’s profound notoriety stems from an eruption on 13 November 1985 that produced an ash plume and pyroclastic flows onto the glacier, triggering large lahars that washed down 11 valleys, inundating most severely the towns of Armero (46 km W) and Chinchiná (34 km E) where approximately 25,000 residents were killed. It remains the second deadliest volcanic eruption of the 20th century after Mt. Pelee killed 28,000 in 1902. Ruiz remained quiet for 20 years after the September 1985-July 1991 eruption until a new explosive event occurred in February 2012; a series of explosive events lasted into 2013. Renewed activity beginning in November 2014 included ash and gas-and-steam plumes, ashfall, and the appearance of a lava dome inside the Arenas crater in August 2015 which has regularly displayed thermal anomalies through 2019. This report covers ongoing activity from January-June 2020 using information primarily from reports by the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and various sources of satellite data.

Gas and ash emissions continued at Nevado del Ruiz throughout January-June 2020; they generally rose to 5.8-6.1 km altitude with the highest reported plume at 7 km altitude during early March. SGC confirmed the presence of the growing lava dome inside Arenas crater during an overflight in January; infrared satellite imagery indicated a continued heat source from the dome through April. SGC interpreted repeated episodes of ‘drumbeat seismicity’ as an indication of continued dome growth throughout the period. Small- to moderate-density sulfur dioxide emissions were measured daily with satellite instruments. The MIROVA graph of thermal activity indicated a heat source consistent with a growing dome from January through April (figure 102).

Figure (see Caption) Figure 102. The MIROVA graph of thermal activity at Nevado del Ruiz from 2 July 2019 through June 2020 indicated persistent thermal anomalies from mid-November 2019-April 2020. Courtesy of MIROVA.

Activity during January-March 2020. During January 2020 some of the frequent tremor seismic events were associated with gas and ash emissions, and several episodes of "drumbeat” seismicity were recorded; they have been related by SGC to the growth of the lava dome on the floor of the Arenas crater. An overflight on 10 January, with the support of the Colombian Air Force, confirmed the presence of the dome which was first proposed in August 2015 (BGVN 42:06) (figure 103). The Arenas crater had dimensions of 900 x 980 m elongate to the SW-NE and was about 300 m deep (figure 104). The dome inside the crater was estimated to be 173 m in diameter and 60 m high with an approximate volume of 1,500,000 m3 (figures 105 and 106). In addition to the dome, the scientists also noted ash deposits on the summit ice cap (figure 107). The Washington VAAC reported an ash plume on 19 January that rose to 5.5 km altitude and drifted SW, dissipating quickly. On 30 January they reported an ash plume visible in satellite imagery extending 15 km NW from the summit at 5.8 km altitude. A single MODVOLC alert was issued on 15 January and data from the VIIRS satellite instrument reported thermal anomalies inside the summit crater on 14 days of the month. Sulfur dioxide plumes with DU values greater than 2 were recorded by the TROPOMI satellite instrument daily during the month.

Figure (see Caption) Figure 103. SGC confirmed the presence of a lava dome inside the Arenas crater at Nevado del Ruiz on 10 January 2020. The dome is shown in brown, and zones of fumarolic activity are labelled around the dome. Courtesy of SGC (El Nuevo Domo de Lava del Volcán Nevado del Ruiz y la Geomorfología Actual del Cráter Arenas 2020).
Figure (see Caption) Figure 104. A view of the Arenas crater at the summit of Nevado del Ruiz on 10 January 2020 (left) is compared with a view from 2010 (right). They were both taken during overflights supported by the Colombian Air Force (FAC). Ash deposits on the ice fields are visible in both images. Fumarolic activity rises from the inner walls of the crater in January 2020. Courtesy of SGC (El Nuevo Domo de Lava del Volcán Nevado del Ruiz y la Geomorfología Actual del Cráter Arenas 2020).
Figure (see Caption) Figure 105. The dome inside the Arenas crater at Nevado del Ruiz appeared dark against the crater rim and ash-covered ice field on 10 January 2020. Features observed include (A) the edge of the Arenas crater, (B) a secondary crater 150 m in diameter located to the west, (C) interior cornices, (D) the lava dome, (E) a depression in the center of the dome caused by possible subsidence and cooling of the lava, (F) a source of gas and ash emission with a diameter of approximately 15 m (secondary crater), and (G, H, and I) several sources of gas emission located around the crater. Courtesy of SGC (El Nuevo Domo de Lava del Volcán Nevado del Ruiz y la Geomorfología Actual del Cráter Arenas 2020).
Figure (see Caption) Figure 106. Images of the summit of Nevado del Ruiz captured by the PlanetScope satellite system on 14 March 2018 (A) and 10 January 2020 (B) show the lava dome at the bottom of Arenas crater. Courtesy Planet Lab Inc. and SGC (El Nuevo Domo de Lava del Volcán Nevado del Ruiz y la Geomorfología Actual del Cráter Arenas 2020).
Figure (see Caption) Figure 107. Ash covered the snow and ice field around the Arenas crater at the summit of Nevado del Ruiz on 10 January 2020. The lava dome is the dark area on the right. Courtesy of SGC (posted on Twitter @sgcol).

The Washington VAAC reported multiple ash plumes during February 2020. On 4 February an ash plume was observed in satellite imagery drifting 35 km W from the summit at 5.8 km altitude. The following day a plume rose to 6.1 km altitude and extended 37 km W from the summit before dissipating by the end of the day (figure 108). On 6 February an ash cloud was observed in satellite imagery centered 45 km W of the summit at 5.8 km altitude. Although it had dissipated by midday, a hotspot remained in shortwave imagery until the evening. Late in the day another plume rose to 6.7 km altitude and drifted W. Diffuse ash was seen in satellite imagery on 13 February fanning towards the W at 5.8 km altitude. On 18 February at 1720 UTC the Bogota Meteorological Weather Office (MWO) reported an ash emission drifting NW at 5.8 km altitude; a second plume was reported a few hours later at the same altitude. Intermittent emissions continued the next day at 5.8-6.1 km altitude that reached as far as 50 km NW before dissipating. A plume on 21 February rose to 6.7 km altitude and drifted W (figure 109). Occasional emissions on 25 February at the same altitude reached 25 km SW of the summit before dissipating. A discrete ash emission around 1550 UTC on 26 February rose to 6.1 km altitude and drifted W. Two similar plumes were reported the next day. On 28 and 29 February plumes rose to 5.8 km altitude and drifted W.

Figure (see Caption) Figure 108. Emissions rose from the Arenas crater at Nevado del Ruiz on 5 February 2020. The Washington VAAC reported an ash plume that day that rose to 6.1 km altitude and drifted 37 km W before dissipating. Courtesy of Camilo Cupitre.
Figure (see Caption) Figure 109. Emissions rose from the Arenas crater at Nevado del Ruiz around 0600 on 21 February 2020. The Washington VAAC reported ash emissions that day that rose to 6.7 km altitude and drifted W. Courtesy of Manuel MR.

SGC reported several episodes of drumbeat type seismicity on 2, 8, 9, and 27 February which they attributed to effusion related to the growing lava dome in the summit crater. Sentinel-2 satellite imagery showed ring-shaped thermal anomalies characteristic of dome growth within Arenas crater several times during January and February (figure 110). The VIIRS satellite instrument recorded thermal anomalies on twelve days during February.

Figure (see Caption) Figure 110. Persistent thermal anomalies from Sentinel-2 satellite imagery during January and February 2020 suggested that the lava dome inside Nevado del Ruiz’s Arenas crater was still actively growing. Atmospheric penetration rendering (bands 12, 11, 8A) courtesy of Sentinel Hub Playground.

On 4, 14, and 19 March 2020 thermal anomalies were visible in Sentinel-2 satellite data from within the Arenas crater. Thermal anomalies were recorded by the VIIRS satellite instrument on eight days during the month. Several episodes of drumbeat seismicity were recorded during the first half of the month and on 30-31 March. Distinct SO2 plumes with DU values greater than 2 were recorded by the TROPOMI satellite instrument daily throughout February and March (figure 111). The Washington VAAC reported an ash emission on 1 March that rose to 5.8 km altitude and drifted NW; it was centered 15 km from the summit when detected in satellite imagery. The next day a plume was seen in satellite imagery moving SW at 7.0 km altitude, extending nearly 40 km from the summit. Additional ash emissions were reported on 4, 14, 15, 21, 28, 29, and 31 March; the plumes rose to 5.8-6.7 km altitude and drifted generally W, some reaching 45 km from the summit before dissipating.

Figure (see Caption) Figure 111. Distinct SO2 plumes with Dobson values (DU) greater than 2 were recorded by the TROPOMI satellite instrument daily during February and March 2020. Ecuador’s Sangay produced smaller but distinct plumes most of the time as well. Dates are shown at the top of each image. Courtesy of NASA’s Sulfur Dioxide Monitoring Page.

Activity during April-June 2020. The Washington VAAC reported an ash emission that rose to 6.7 km altitude and drifted W on 1 April 2020. On 2 April, emission plumes were visible from the community of Tena in the Cundinamarca municipality which is located 100 km ESE (figure 112). The unusually clear skies were attributed to the reduction in air pollution in nearby Bogota resulting from the COVID-19 Pandemic quarantine. On 4 April the Bogota MWO reported an emission drifting SW at 5.8 km altitude. An ash plume on 8 April rose to 6.7 km altitude and drifted W. On 25 April the last reported ash plume from the Washington VAAC for the period rose to 6.1 km altitude and was observed in satellite imagery moving W at 30 km from the summit; after that, only steam and gas emissions were observed.

Figure (see Caption) Figure 112. On the evening of 2 April 2020, emission plumes from Nevado del Ruiz were visible from Santa Bárbara village in Tena, Cundinamarca municipality which is located 100 km ESE. The unusually clear skies were attributed to the reduction in air pollution in the nearby city of Bogota resulting from the COVID-19 Pandemic quarantine. Photo by Williama Garcia, courtesy of Semana Sostenible (3 April 2020).

Distinct SO2 plumes with DU values greater than 2 were recorded by the TROPOMI satellite instrument daily throughout the month. On 13 April, a Sentinel-2 thermal image showed a hot spot inside the Arenas crater largely obscured by steam and clouds. Cloudy images through May and June prevented observation of additional thermal anomalies in satellite imagery, but the VIIRS thermal data indicated anomalies on 3, 4, and 26 April. SGC reported low-energy episodes of drumbeat seismicity on 4, 9, 10, 12, 15, 16, 20, and 23 April which they interpreted as related to growth of the lava dome inside the Arenas crater. The seismic events were located 1.5-2.0 km below the floor of the crater.

Small emissions of ash and gas were reported by SGC during May 2020 and the first half of June, with the primary drift direction being NW. Gas and steam plumes rose 560-1,400 m above the summit during May and June (figure 113). Drumbeat seismicity was reported a few times each month. Sulfur dioxide emissions continued daily; increased SO2 activity was recorded during 10-13 June (figure 114).

Figure (see Caption) Figure 113. Gas and steam plumes rose 560-1,400 m above the summit of Nevado del Ruiz during May and June 2020, including in the early morning of 11 June. Courtesy of Carlos-Enrique Ruiz.
Figure (see Caption) Figure 114. Increased SO2 activity during 10-13 June 2020 at Nevado del Ruiz was recorded by the TROPOMI instrument on the Sentinel-5P satellite. Sangay also emitted SO2 on those days. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Information Contacts: El Servicio Geológico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www.sgc.gov.co/volcanes, https://twitter.com/sgcol); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Camilo Cupitre (URL: https://twitter.com/Ccupitre/status/1225207439701704709); Manuel MR (URL: https://twitter.com/ElPlanetaManuel/status/1230837262088384512); Semana Sostenible (URL: https://sostenibilidad.semana.com/actualidad/articulo/fumarola-del-nevado-del-ruiz-fue-captada-desde-tena-cundinamarca/49597); Carlos-Enrique Ruiz (URL: https://twitter.com/Aleph43/status/1271800027841794049).


January 2021 (BGVN 46:01) Citation IconCite this Report

Dome growth and ash emissions continue during July-December 2020

Colombia’s broad, glacier-capped Nevado del Ruiz has an eruption history documented back 8,600 years, including documented observations since 1570. Ruiz remained quiet for 20 years after the deadly September 1985-July 1991 eruption until a period of explosive activity from February 2012 into 2013. Renewed activity beginning in November 2014 included ash and gas-and-steam plumes, ashfall, and the appearance of a slowly growing lava dome inside the Arenas crater in August 2015. Additional information has caused a revision to earlier reporting that eruptive activity ended in May 2017 and began again that December (BGVN 44:12); activity appears to have continued throughout 2017 with intermittent ash emissions and thermal evidence of dome growth. Periods of increased thermal activity alternated with periods of increased explosive activity during 2018-2019 and into 2020; SO2 emissions persisted at significant levels. The lava dome has continued to grow through 2020. This report covers ongoing activity from July-December 2020 using information from reports by the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and various sources of satellite data.

Gas and ash emissions continued throughout July-December 2020; they generally rose to 5.8-6.1 km altitude with the highest reported plume at 6.7 km altitude on 7 December. SGC interpreted repeated episodes of “drumbeat seismicity” as an indication of continued dome growth throughout the period. Satellite thermal anomalies also suggested that dome growth continued. The MIROVA graph of thermal activity suggests that the dome was quiet in July and early August, but small pulses of thermal energy were recorded every few weeks for the remainder of 2020 (figure 115). Plots of the cumulative number and magnitude of seismic events at Nevado del Ruiz between January 2010 and November 2020 show a stable trend with periodic sharp increases in activity or magnitude throughout that time. SGC has adjusted the warning levels over time according to changes in the slope of the curves (figure 116).

Figure (see Caption) Figure 115. Thermal energy shown in the MIROVA graph of log radiative power at Nevado del Ruiz from 3 February 2020 through the end of the year indicates that higher levels of thermal energy lasted through April 2020; a quieter period from late May-early August was followed by low-level persistent anomalies through the end of the year. Courtesy of MIROVA.
Figure (see Caption) Figure 116. Changes in seismic frequency and energy at Nevado del Ruiz have been monitored by SGC for many years. Left: the cumulative number of daily VT, LP-VLP, TR, and HB seismic events, recorded between 1 January 2010 and 30 November 2020. The arrows highlight the days with the highest number of seismic events; the number and type of event is shown under the date. Right: The cumulative VT and HB seismic energy recorded between 1 January 2010 and 30 November 2020. The arrows highlight the days with the highest energy; the local magnitude of the event is shown below the date. SGC has adjusted the warning levels over time (bar across the bottom of each graph) according to changes in the slope of the curves. Courtesy of SGC (INFORME TÉCNICO – OPERATIVO DE LA ACTIVIDAD VOLCÁNICA, SEGMENTO VOLCÁNICO NORTE DE COLOMBIA – NOVIEMBRE DE 2020).

Activity during July-December 2020. Seismic energy increased during July compared to June 2020 with events localized around the Arenas crater. The depth of the seismicity varied from 0.3-7.8 km. Some of these signals were associated with small emissions of gas and ash, which were confirmed through webcams and by reports from officials of the Los Nevados National Natural Park (NNNP). The Washington VAAC reported a possible ash emission on 8 July that rose to 6.1 km altitude and drifted NW. On 21 July a webcam image showed an ash emission that rose to the same altitude and drifted W; it was seen in satellite imagery possibly extending 35 km from the summit but was difficult to confirm due to weather clouds. Short- to moderate-duration (less than 40 minutes) episodes of drumbeat seismicity were recorded on 5, 13, 17, and 21 July. SCG interprets this type of seismic activity as related to the growth of the Arenas crater lava dome. Primarily WNW drifting plumes of steam and SO2 were observed in the webcams daily. The gas was occasionally incandescent at night. The tallest plume of gas and ash reached 1,000 m above the crater rim on 30 July and was associated with a low-energy tremor pulse; it produced ashfall in parts of Manizales and nearby communities (figure 117).

Figure (see Caption) Figure 117. Images captured by a traditional camera (top) and a thermal camera (bottom) at Nevado del Ruiz showed a small ash emission in the early morning of 30 July 2020. Ashfall was reported in Manizales. The cameras are located 3.7 km W of the Arenas crater. Courtesy of SGC (Emisión de ceniza Volcan Nevado del Ruiz Julio 30 de 2020).

Seismicity increased in August 2020 with respect to July. Some of the LP and TR (tremor) seismicity was associated with small emissions of gas and ash, confirmed by web cameras, park personnel, and the Washington VAAC. The Washington VAAC received a report from the Bogota MWO of an ash emission on 1 August that rose to 6.1 km altitude and drifted NW; it was not visible in satellite imagery. Various episodes of short duration drumbeat seismicity were recorded during the month. The tallest steam and gas plume reached 1,800 m above the rim on 31 August. Despite the fact that in August the meteorological conditions made it difficult to monitor the surface activity of the volcano, three ash emissions were confirmed by SGC.

Seismicity decreased during September 2020 with respect to August. Some of the LP and TR (tremor) seismicity was associated with small emissions of gas and ash, confirmed by web cameras, park personnel and the Washington VAAC. The Washington VAAC reported an ash emission on 16 September that rose to 6.1 km altitude and drifted NW. A minor ash emission on 20 September drifted W from the summit at 5.8 km altitude. A possible emission on 23 September drifted NW at 6.1 km altitude for a brief period before dissipating. Two emissions were reported drifting WNW of the summit on 26 September at 5.8 and 5.5 km altitude. Continuous volcanic tremors were registered throughout September, with the higher energy activity during the second half of the month. One episode of drumbeat seismicity on 15 September lasted for 38 minutes and consisted of 25 very low energy earthquakes. Steam and gas plumes reached 1,800 m above the crater rim during 17-28 September (figure 118). Five emissions of ash were confirmed by the webcams and park officials during the month, in spite of difficult meteorological conditions; three of them occurred between 15 and 20 September.

Figure (see Caption) Figure 118. A dense plume of steam rose from Nevado del Ruiz in the morning of 17 September 2020. Courtesy of Gonzalo.

Seismicity increased during October with respect to September. A few of the LP and tremor seismic events were associated with small emissions of gas and ash, confirmed by web cameras, park personnel, and the Washington VAAC. The Washington VAAC issued advisories of possible ash emissions on 2, 6, 9, 11, 15, 17, 18, and 21 October. The plumes rose to 5.6-6.4 km altitude and drifted primarily W and NW. Steam plumes were visible most days of the month (figure 119). Only a few were visible in satellite data, but most were visible in the webcams. Several episodes of drumbeat seismicity were recorded on 13, 22-25, and 27 October, which were characterized by being of short duration and consisting of very low energy earthquakes. The tallest plume during the month rose about 2 km above the crater rim on 18 October. Ash emissions were recorded eight times during the month by SGC.

Figure (see Caption) Figure 119. A steam plume mixed with possible ash drifted SE from Nevado del Ruiz on 7 October 2020. Courtesy of vlucho666.

During November 2020, the number of seismic events decreased relative to October, but the amount of energy released increased. Some of the seismicity was associated with small emissions of gas and ash, confirmed by webcams around the volcano. The Washington VAAC reported ash emissions on 22 and 30 November; the 22 November event was faintly visible in satellite images and was also associated with an LP seismic event. They rose to 5.8-6.1 km altitude and drifted W. Various episodes of drumbeat seismicity registered during November were short- to moderate-duration, very low energy, and consisted of seismicity associated with rock fracturing (VT). Multiple steam plumes were visible from communities tens of kilometers away (figure 120).

Figure (see Caption) Figure 120. Multiple dense steam plumes were photographed from communities around Nevado del Ruiz during November 2020, including on 18 (top) and 20 (bottom) November. Top image courtesy of Jose Fdo Cuartas, bottom image courtesy of Efigas Oficial.

Seismic activity increased in December 2020 relative to November. It was characterized by continuous volcanic tremor, tremor pulses, long-period (LP) and very long-period (VLP) earthquakes. Some of these signals were associated with gas and ash emissions, one confirmed through the webcams. The Washington VAAC reported ash emissions on 5 and 7 December. The first rose to 5.8 km altitude and drifted NW. The second rose to 6.7 km altitude and drifted W. A single discrete cloud was observed 35 km W of the summit; it dissipated within six hours. Drumbeat seismic activity increased as well in December; the episode on 3 December was the most significant. Steam and gas emissions continued throughout the month; a plume of gas and ash reached 1,700 m above the summit on 20 December, and drifted NW.

Sentinel-2 satellite data showed at least one thermal anomaly inside the Arenas crater each month during August-December 2020, corroborating the seismic evidence that the dome continued to grow throughout the period (figure 121). Sulfur dioxide emissions were persistent, with many days every month recording DU values greater than two with the TROPOMI instrument on the Sentinel 5-P satellite (figure 122).

Figure (see Caption) Figure 121. Thermal anomalies at Nevado del Ruiz were recorded at least once each month during August-December 2020 suggesting continued growth of the dome within the Arenas crater at the summit. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 122. Sulfur dioxide emissions were persistent at Nevado del Ruiz during August-December 2020, with many days every month recording DU values greater than two with the TROPOMI instrument on the Sentinel 5-P satellite. Ecuador’s Sangay had even larger SO2 emissions throughout the period. Dates are at the top of each image. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Additional reports of activity during 2017. Activity appears to have continued during June-December 2017. Ash emissions were reported by the Bogota Meteorological Weather Office (MWO) on 13 May, and by SGC on 28 May. During June, some of the recorded seismic events were associated with minor emissions of ash; these were confirmed by webcams and by field reports from both the staff of SGC and the Los Nevados National Natural Park (PNNN). Ash emissions were confirmed in webcams by park officials on 3, 16, and 17 June. Gas emissions from the Arenas crater during July 2017 averaged 426 m above the crater rim, generally lower than during June. The emissions were mostly steam with small amounts of SO2. Emissions were similar during August, with most steam and gas plumes drifting NW. No ash emissions were reported during July or August.

SGC reported steam and gas plumes during September that rose as high as 1,650 m above the crater rim and drifted NW. On 21 September the Washington VAAC received a report of an ash plume that rose to 6.4 km altitude and drifted NNW, although it was not visible in satellite imagery. Another ash emission rising to 6.7 km altitude was reported on 7 October; weather clouds prevented satellite observation. An episode of drumbeat seismicity was recorded on 9 October, the first since April 2017. While SGC did not explicitly mention ash emissions during October, several of the webcam images included in their report show plumes described as containing ash and gas (figure 123).

Figure (see Caption) Figure 123. Plumes of steam, gas, and ash rose from Arenas crater at Nevado del Ruiz most days during October 2017. Photographs were captured by the webcams installed in the Azufrado Canyon and Cerro Gualí areas. Courtesy of SGC (INFORME DE ACTIVIDAD VOLCANICA SEGMENTO NORTE DE COLOMBIA, OCTUBRE DE 2017).

The Washington VAAC received a report from the Bogota MWO of an ash emission that rose to 6.1 km altitude and drifted NE on 8 November 2017. A faint plume was visible in satellite imagery extending 15 km NE from the summit. SGC reported that plumes rose as high as 2,150 m above the rim of Arenas crater during November. The plumes were mostly steam, with minor amounts of SO2. A diffuse plume of ash was photographed in a webcam on 24 November. SGC did not report any ash emissions during December 2017, but the Washington VAAC reported “a thin veil of volcanic ash and gases” visible in satellite imagery and webcams on 18 December that dissipated within a few hours. In addition to the multiple reports of ash emissions between May and December 2017, Sentinel-2 thermal satellite imagery recorded at least one image each month during June-December showing a thermal anomaly at the summit consistent with the slowly growing dome first reported in August 2015 (figure 124).

Figure (see Caption) Figure 124. Thermal anomalies from the growing dome inside Arenas crater at the summit of Nevado del Ruiz appeared at least once each month from June-December 2017. A strong anomaly was slightly obscured by clouds on 3 June (top left). On 2 August, a steam plume obscured most of the crater, but a small thermal anomaly is visible in its SE quadrant (top right). Strong anomalies on 30 November and 20 December (bottom) have a ring-like form suggestive of a growing dome. Atmospheric penetration rendering (bands 12, 11, 8A), courtesy of Sentinel Hub Playground.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Gonzalo (URL: https://twitter.com/chaloc22/status/1306581929651843076); Jose Fdo Cuartas (URL: https://twitter.com/JoseFCuartas/status/1329212975434096640); Vlucho666 (URL: https://twitter.com/vlucho666/status/1313791959954268161); Efigas Oficial (URL: https://twitter.com/efigas_oficial/status/1329780287920873472).


June 2021 (BGVN 46:06) Citation IconCite this Report

Low-level thermal activity and dome growth continues during January-April 2021

Colombia’s broad, glacier-capped Nevado del Ruiz has dated eruptions going back 8,600 years, including observed activity since 1570. Ruiz remained quiet for 20 years after the deadly September 1985-July 1991 eruption until new explosive activity occurred from February 2012 into 2013. Renewed activity beginning in November 2014 included ash and gas-and-steam plumes, ashfall, and the appearance of a slowly growing lava dome inside the Arenas crater in August 2015. Intermittent ash emissions and thermal evidence of dome growth continued with alternating periods of increased thermal and explosive activity during 2015-2020; SO2 emissions persisted at significant levels. This report covers ongoing activity from January-April 2021 using information from the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and satellite information.

Steam and gas emissions continued throughout January-April 2021, but ash emissions were infrequent and only confirmed visually during April. Thermal activity continued at a low level (figure 125); infrequent satellite data confirmed continued growth of the dome (figure 126). Sulfur dioxide emissions recorded daily by satellite instruments were weak in January and weak to moderate during February. A period of strong daily SO2 emissions in early March was followed by weak and moderate emissions for the rest of the month and during April 2021 (figure 127).

Figure (see Caption) Figure 125. Thermal activity continued at a low level at Nevado del Ruiz during January-April 2021, with infrequent anomalies recorded a few times each month in the MIROVA log radiative power graph from 28 June 2020 through April 2021. Courtesy of MIROVA.
Figure (see Caption) Figure 126. Infrequent ring-shaped thermal anomalies inside the Arenas crater of Nevado del Ruiz supported seismic evidence of continued dome growth during January-April 2021. Meteoric clouds prevented views in most Sentinel-2 satellite images other than 28 January (left) and 9 March 2021 (right). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 127. Daily sulfur dioxide emissions from Nevado del Ruiz persisted during January-April 2021 and were recorded by the TROPOMI instrument on the Sentinel-5P satellite. A period of strong emissions occurred in early March; the rest of the time emission levels were low to moderate. Ecuador’s Sangay (lower left plume in each image) often had larger SO2 emissions. Dates are recorded above each image. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Overall activity was low during January 2021. The number and intensity of seismic Volcano-tectonic (VT) events related to rock fracturing decreased from December 2020. Low levels of tremor continued throughout the month, and there were two episodes of drumbeat seismicity interpreted by SGC as related to dome growth. The tallest steam and gas plume reached about 1.5 km above the rim of Arenas crater on 30 January, but no ash emissions were reported during the month. An overflight on 29 January revealed the continued slow growth of the dome inside the crater and minor emissions of gas and steam (figure 128).

Figure (see Caption) Figure 128. Weak emissions of steam and gas surrounded the dome growing inside Arenas crater (inset) at the summit of Nevado del Ruiz during an overflight on 29 January 2021. Inset image brightness enhanced due to shadows. View is looking down towards the west with the unvegetated La Olleta lava dome at upper right. Courtesy of SGC (SGC identifica cambios morfológicos en el domo de lava del cráter Arenas del Volcán Nevado del Ruiz, 01 de febrero de 2021).

Both the number of seismic events and the amount of energy released decreased again during February 2021 from the previous month. Most of the VT seismic events were related to rock fracturing in the immediate vicinity of the volcano. Low-level harmonic tremors were recorded during 4-5 February. Three short episodes of very low-energy drumbeat seismicity, between 3 and 33 minutes long, were recorded on 16, 19, and 22 February. On 26 February gas and steam plumes reached about 1.5 km above the crater rim. The Washington VAAC reported a possible ash emission on 21 February moving SE at 5.8 km altitude seen in the summit webcam, but weather clouds made the observation uncertain.

Seismicity related to both rock fracturing and fluid movement increased during March 2021, with events primarily within the Arenas crater and SE, SSW, and NW of the crater within a radius of 4 km. Episodes of drumbeat seismicity associated with rock fracturing (VT) and dome growth were recorded on 2-4, 14, 15, 17, and 26-28 March. On 26 March the highest daily rate of this type of seismicity occurred so far in 2021, with a total of 411 VT earthquakes distributed in 14 episodes. Most of the seismicity associated with fluid movement was located in the Arenas crater or around it, within a radius of 2 km. Harmonic tremor was recorded on 2, 7, 11, 12 and 13 March with durations of 20 to 55 min. All of the episodes were very low energy.

Visibility from the webcams was poor for much of the month due to strong precipitation and clouds. On 29 March 2021 the gas plume reached about 2.5 km above the crater rim. SGC noted that a few of the seismic signals related to the fluid movement inside the volcano were likely associated with emission of gas and possibly ash, although none were confirmed visually due to clouds. The Washington VAAC reported an ash emission on 19 March that rose to an altitude of 6.4 km and drifted N. A possible ash emission on 27 March rose to 6.1 km altitude and also drifted N, but extensive cloud cover obscured visibility.

Minor ash emissions and low-level thermal anomalies were reported during April 2021. Seismic activity (VT) decreased during April in both frequency and energy level compared with March. Episodes of drumbeat seismicity associated with rock fracturing were recorded on 2, 5, 14, 17, 19, 22-23, and 26-27 April. Drumbeats associated with fluid dynamics were recorded on 16 and 18 April. They were very low energy, and a few had longer durations than those recorded earlier in the year, ranging from 29-50 minutes. Harmonic tremor was recorded on 12, 13, and 19 April. On 20 April gas and steam reached more than 2 km above the crater. Webcams and field observers confirmed that seismic signals were associated with gas and ash emissions on 1, 16, 26, and 30 April. The Washington VAAC reported an ash emission on 1 April that rose to 5.8 km altitude and drifted SW. Ash emissions were also reported on 26 and 30 April that rose to 6.1 and 5.8 km altitude and drifted NW and N, respectively, for a few hours before dissipating.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www.sgc.gov.co/volcanes); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


January 2022 (BGVN 47:01) Citation IconCite this Report

Ash emissions increase in frequency during November-December 2021; dome growth continues

Colombia’s broad, glacier-capped Nevado del Ruiz has dated eruptions going back 8,600 years, including observed activity since 1570. Ruiz remained quiet for 20 years after the deadly September 1985-July 1991 eruption until new explosive activity occurred from February 2012 into 2013. Renewed activity beginning in November 2014 included ash and gas-and-steam plumes, ashfall, and the appearance of a slowly growing lava dome inside the Arenas crater in August 2015. Intermittent ash emissions and thermal evidence of dome growth has continued with alternating periods of increased thermal and explosive activity into 2021; daily SO2 emissions are detectable with satellite instruments. This report covers ongoing similar activity from May-December 2021 using information from the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and satellite information.

Although there were very few thermal anomalies recorded during May-December 2021, the number of ash emissions, and the density of the plumes, increased throughout the period. The Washington VAAC reported only a few sporadic emissions in May, and increased frequency in June. By July they were reported on most days, and during August-October there were very few days when they were not reported. Multiple VAAC reports were issued daily during November and December. Most of the satellite images during May-December were cloud covered. Steam plumes were visible in many images, but thermal anomalies were infrequent and not observed in more than one image per month until December. Small to moderate-sized sulfur dioxide plumes were recorded daily in satellite imagery with plumes drifting in multiple directions (figure 129).

Figure (see Caption) Figure 129. Sulfur dioxide emissions from Nevado del Ruiz were recorded daily throughout May-December 2021 with the TROPOMI instrument on the Sentinel-5P satellite. Ecuador’s Sangay (bottom center of images) had similar size plumes most days. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

The number of seismic events decreased during May 2021 compared with April but remained the same with respect to the amount of energy released. Continuous tremor, pulsating tremor, LP, and VLP-type seismicity were all recorded. A few of these events were associated with minor ash emissions that were visible in webcams. Episodes of drumbeat seismicity, which SGC associates with growth of the lava dome inside Arenas crater, were reported on 1, 2, 19, and 28-30 May. Steam and gas plumes were recorded daily with plume heights around 1 km on most days. The highest plume, on 31 May, reached 2,700 m above the summit. The Washington VAAC reported an ash emission at 5.8 km altitude drifting NW on 21 May that was not seen in satellite imagery due to clouds, but a similar height plume was observed drifting NW on 27 May.

During June 2021, seismicity increased in the number of events but declined in the amount of energy released relative to May. A few of the seismic events were associated with small emissions of ash confirmed by the webcams. The Washington VAAC reported dense ash emissions drifting NE to about 50 km from the summit at 6.5 km altitude on 11 June. The tallest gas-and-steam plume of the month reached about 2,200 m above the summit that day. A faint thermal anomaly was visible in satellite imagery under a dense white plume on 12 June. An ash plume on 15 June was observed in the summit webcam moving W at 5.8 km altitude. Two days later a plume was observed moving NW at 6.1 km altitude. A possible emission on 23 June drifted W at 5.8 km altitude. Low-energy drumbeat seismicity was recorded on 3, 5-10, 17, 22, 23, and 25 June.

Seismicity increased in both number of events and amount of energy released during July 2021, specifically in the number of pulsating tremors, and in the energy of the continuous tremors. Short-duration, low-energy drumbeat seismicity was recorded on 1, 2, 10, 12-14, 17, 28, and 30 July. The number of ash emissions also increased; they were observed in the webcams, and by residents in communities around the volcano multiple times. Ash was visible up to 90 km NW on 6 July. Ashfall was reported to the WNW in Manizales on the morning of 14 July (figure 130). Three explosions were recorded by the webcams in the morning of 19 July; plume heights rose 420-520 m and drifted WNW. The Washington VAAC issued ash advisories on most days during July. Plume altitudes ranged from 5.8-6.7 km altitude and drifted either W or NW. The maximum height steam and gas plume rose about 2,200 m above the summit on 28 July.

Figure (see Caption) Figure 130. A dense ash plume rose from Nevado del Ruiz on the morning of 14 July 2021 and caused ashfall in Manizales. Courtesy of SGC.

The numbers of pulsating tremor and continuous tremor seismic events, and ash emissions all increased during August 2021; ash emissions were observed in the webcams, by nearby residents, and by SGC and PNNLN (Parque Nacional Natural Los Nevados) personnel working in the area. A weak thermal anomaly was present in satellite imagery under a white plume at the summit on 8 August. Two episodes of low-level drumbeat seismicity, interpreted as dome growth by SGC, were recorded on 22 August. Ash emissions were observed in the webcams on the morning of 26 August that rose 490 m above the summit and drifted WNW (figure 131). The Washington VAAC reported ash emissions almost every day of the month. The plumes reached 5.8-6.4 km altitude and drifted primarily NW but switched to the NE briefly on 15 August.

Figure (see Caption) Figure 131. Ash emissions rose 490 m above the summit of Nevado del Ruiz on the morning of 26 August 2021 and drifted WNW. Courtesy of SGC.

The energy level of the continuous tremor events decreased during September 2021 along with the number of pulsating tremors. Drumbeat seismicity was recorded on 17, 19, 22, 27, and 30 September. Park and SGC personnel witnessed small ash emissions that were also confirmed in the webcams. Steam and gas plumes rose as high as 1,500 m above the summit on 6 September. There were only a few days in September when the Washington VAAC did not report ash emissions reaching 5.8-6.4 km altitude and drifting mostly NW.

The energy level of the continuous tremor events rose in October 2021 while the number of seismic events overall remained similar to the previous month. Drumbeat seismicity was recorded on 2, 5, 11-13, 15, and 24-27 October. Ash emissions were confirmed by webcams, Park, and SGC personnel. Some of the increases in the energy of the seismic events corresponded to ash emissions that lasted for several hours. On 3 October the Washington VAAC reported ash emissions that reached 6.7 km altitude and drifted WNW from the summit. Ash emissions on 8 October drifted 35 km NW from the summit at 5.8 km altitude. Intermittent puffs of ash were detected in satellite imagery drifting NNE on 10 October at 6.1 km altitude. Drift direction was more variable during October than September, and ash plumes were reported daily from 3 October through the end of the month at altitudes of 5.8-6.7 km. On the morning of 18 October ashfall was reported in several areas of Manizales. The highest gas-and-steam plume of the month rose to 2,400 m above the summit on 29 October. Gas-and-ash emissions were captured in webcam images early on 29 October (figure 132). A faint thermal anomaly was present in Sentinel satellite imagery on 30 October under a dense white plume.

Figure (see Caption) Figure 132. Gas and ash emissions at Nevado del Ruiz were captured multiple times in webcam images on 29 October 2021. Courtesy of SGC.

Similar activity continued during November and December 2021, with extended periods of ash emissions reported a number of times, observed in webcams and by personnel in the field. SGC reported an ash plume visible in webcams early on 1 November that reached 2,500 m above the summit and drifted NE (figure 133). Continuous ash emissions associated with a seismic tremor signal were reported in the morning of 7 November rising 500 m and drifting WNW, causing trace amounts of ashfall in Manizales and Villamaria (figure 134). The airport in La Nubia briefly suspended operations as a result of the ashfall. SGC officials needed to clear ash off the solar panels of the monitoring stations at the volcano on 9, 10, and 11 November after emissions during the previous days (figure 135). Daily steam and gas plumes usually rose to heights of 1,500-1,800 m above the summit. Multiple daily reports from the Washington VAAC confirmed ongoing ash emissions that rose to altitudes of 5.8-6.7 km through the end of the year. They were observed as far as 75 km NW from the volcano on 6 November, and similar distances on several other occasions. Ash could be seen in Sentinel satellite imagery on 24 November. Trace amounts of ashfall were also reported during the morning of 26 November in various sectors of Manizales. Continuous ash emissions were observed in satellite imagery moving W from the summit at 7 km altitude on 29 November.

Figure (see Caption) Figure 133. SGC reported an ash plume at Nevado del Ruiz visible in webcams early on 1 November 2021 that reached 2,500 m above the summit and drifted NE. Courtesy of SGC.
Figure (see Caption) Figure 134. Continuous ash emissions associated with a seismic tremor signal at Nevado del Ruiz were reported in the morning of 7 November 2021 rising 500 m and drifting WNW causing trace amounts of ashfall in the Park, Villamaria, and briefly halting flights at La Nubia airport in Manizales. Courtesy of SGC.
Figure (see Caption) Figure 135. SGC staff needed to clear ash off solar panels at the Nevado del Ruiz monitoring stations on 9, 10, and 11 November 2021 after emissions during the previous days. Courtesy of SGC.

Steam and gas plumes usually rose 1,500-1,800 m above the summit during December 2021 but reached 2,650 m on 12 December. The only clear Sentinel satellite image of the dome inside Arenas crater during the period was on 14 December, when a ring-shaped thermal anomaly was recorded (figure 136). Trace amounts of ashfall were reported in Manizales and Villamaria on 17 and 18 December from gas and ash emissions during those days. Ash emissions were also visible in the webcams early on 23 December. On 24 December, two thermal anomalies were recorded through a diffuse meteoric cloud cover. Low-energy drumbeat seismicity returned on 29 and 30 December. SGC reported that analysis of satellite imagery indicated that the dome appeared to lose volume during the last days of the month.

Figure (see Caption) Figure 136. Thermal anomalies at Nevado del Ruiz in Sentinel-2 satellite data were infrequent during May-December 2021. The only day of the period when a clear ring-like anomaly inside the crater was recorded was on 14 December (left). Two small anomalies appeared below diffuse clouds on 24 December (right). Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www.sgc.gov.co/volcanes); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/).


August 2022 (BGVN 47:08) Citation IconCite this Report

Intermittent ash emissions, thermal activity, and dome growth during January-July 2022

Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia, covering more than 200 km2. It contains the 1-km-wide, 240-m-deep Arenas crater that occupies the summit. Eruptions are dated to 8,600 years before present, including observed activity since 1570. This current eruption period has been ongoing since November 2014 and has more recently consisted of continued dome growth, ash emissions, ashfall, and seismicity. This report covers intermittent ash emissions, ashfall, thermal activity, and seismicity during January through July 2022 based on information from the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales and various satellite data.

Occasional thermal anomalies were recorded during January through July 2022, with the highest number of anomalies detected during January through February, according to the MIROVA graph (Log Radiative Power) (figure 137). Some of these anomalies were detected in the summit crater in Sentinel-2 infrared satellite imagery, accompanied by gas-and-steam emissions (figure 138). Small-to-moderate-sized sulfur dioxide plumes were often recorded with the TROPOMI instrument on the Sentinel-5P satellite (figure 139). Many of these plumes had maximum mass burdens in excess of 2 Dobson Units (DU) and drifted in multiple directions. The Washington VAAC reported that ash plumes rose to 5.8-8.5 km altitude and drifted in multiple directions. The highest plume occurred on 11 April.

Figure (see Caption) Figure 137. Intermittent thermal anomalies were detected at Nevado del Ruiz during December 2021 through July 2022, according to this MIROVA graph (Log Radiative Power). A larger number of anomalies occurred during January through February, after which the frequency of the anomalies declined. Courtesy of MIROVA.
Figure (see Caption) Figure 138. Sentinel-2 infrared satellite images showed occasional small thermal anomalies at the summit crater of Nevado del Ruiz on 28 January 2022 (top left), 2 February 2022 (top right), 9 March 2022 (bottom left), and 3 May 2022 (bottom right). White gas-and-steam emissions were intermittently observed in these images as well. Images use Atmospheric penetration rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 139. Sulfur dioxide emissions from Nevado del Ruiz were frequently recorded throughout January through July 2022 with the TOPOMI instrument on the Sentinel-5P satellite. Plumes drifted in different directions and often exceeded 2 Dobson Units (DU) on 24 January 2022 (top left), 20 February 2022 (top middle), 9 March 2022 (top right), 24 April 2022 (bottom left), 15 June 2022 (bottom middle), and 7 July 2022 (bottom right). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during January and February was relatively low and mainly consisted of seismicity in the Arenas crater. Seismic events included continuous volcanic tremor, tremor pulses, harmonic tremor, long period, and very long period earthquakes of variable intensity; these events indicated fluid movements. Drumbeat type seismicity was reported on 3, 25, 28, and 30 January and 2, 3, 4, 10, 19, 23, 26, and 28 February. According to SGC, this type of seismicity is related to the continued lava dome growth at the bottom of the crater. Gas-and-steam plumes were intermittently reported, the highest of which rose as 2.2 km above the crater on 24 January and drifted in various directions. Some of the seismic signals were associated with ash emissions and incandescence was observed in webcam images. During the night of 3 and 4 February two small explosions were observed with a FLIR camera. Gas-and-steam emissions rose as high as 2.9 km above the crater on 23 February and drifted in multiple directions. Another small explosion was reported on 11 February, which included an ash plume that rose above the crater; the Washington VAAC issued a notice that reported an ash plume that rose to 7 km altitude and drifted N at 1130.

During March and April low activity consisting of dome growth, ash emissions, and seismicity persisted. Seismicity included continuous volcanic tremor, tremor pulses, long period, and very long period earthquakes, all of which varied in intensity. Intermittent gas-and-ash emissions were also reported. Drumbeat type events were recorded on 1, 8, 9, 10, 11, 13, 16, and 22 March. Gas-and-steam emissions rose as high as 2.2 km above the crater on 13 March and drifted in multiple directions. During 9-10 April gas-and-ash emissions rose 3.3 km and 3.2 km high above the crater at 1713 and 0858 and drifting N and SW, respectively. Minor ashfall around the volcano was reported by Parque Nacional Natural Los Nevados staff. It was also visible in webcam images and from the city of Manizales (25 km N). During 25-26 April ashfall deposits were reported in Manizales and Villamaría (28 km NW), relating to gas-and-ash emissions.

Seismicity and dome growth continued during May, June, and July with continuous volcanic tremor, tremor pulses, long period, and very long period earthquakes each of variable intensities. An ash plume at 0536 on 3 May rose 2.1 km above the crater and drifted W. Resulting ashfall was detected in the municipalities of Santa Rosa de Cabal (33 km W), Dosquebradas (40 km W), Pereira (40 km WSW), and Manizales. Continued gas-and-steam emissions rose as high as 3 km above the crater on 10 May and drifted in different directions. Drumbeat type events were detected on 5, 8, and 12 May and 2, 3, 6, 7, 11, 13, 14, 15, 18, 22, and 26 June. A gas-and-ash plume rose 3 km above the volcano at 0857 on 9 May and resulted in ashfall in Manizales, Villamaría, Chinchiná (30 km WNW), Pereira, Dosquebradas, and Santa Rosa. Ashfall deposits were also detected during 25 and 26 May in Manizales and other towns located to the W and NW of the volcano. On 22 June, ashfall was reported in Manizales. During July, drumbeat-type events occurred on 11, 12, 16, and 22 July.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www.sgc.gov.co/volcanes); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/).


February 2023 (BGVN 48:02) Citation IconCite this Report

Gas-and-ash emissions, dome growth, and seismicity continued during August 2022-January 2023

Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. It contains the 1-km-wide, 240-m-deep Arenas summit crater. Eruptions have been documented since 1570 CE. The current eruption period has been ongoing since November 2014 and more recently has consisted of intermittent ash emissions, thermal activity, and lava dome growth (BGVN 47:08). This report updates activity including gas-and-ash emissions, dome growth, and seismicity during August 2022 through January 2023 using information from the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and various satellite data.

Intermittent thermal anomalies were recorded during August 2022 through January 2023, with three peaks of strong and frequent hotspots detected during late October, mid-December, and late January, according to the MIROVA graph (Log Radiative Power) (figure 140). Some of this thermal activity was also visible in Sentinel-2 infrared satellite imagery, occasionally accompanied by white gas-and-steam emissions (figure 141). According to data from the TROPOMI instrument on the Sentinel-5P satellite, sulfur dioxide plumes were also detected throughout the reporting period, many of which had a maximum mass that exceeded 2 Dobson Units (DU) and drifted in different directions (figure 142).

Figure (see Caption) Figure 140. Intermittent thermal anomalies were detected at Nevado del Ruiz during August 2022 through January 2023, according to this MIROVA graph (Log Radiative Power). Slightly stronger and more frequent anomalies were detected during late October, mid-December, and late January. Two gradual declines in both power and frequency were observed during November and late-December. Courtesy of MIROVA.
Figure (see Caption) Figure 141. Sentinel-2 infrared satellite images showed an occasional thermal anomaly at the summit crater of Nevado del Ruiz, seen here on 25 September 2022 (top left), 30 October 2022 (top right), 29 December 2022 (bottom left), and 28 January 2023 (bottom right). Sometimes white gas-and-steam emissions accompanied the thermal activity, as shown on 25 September, 30 October, and 29 December. Images use “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 142. Sulfur dioxide emissions from Nevado del Ruiz were often recorded during August 2022 through January 2023 with the TROPOMI instrument on the Sentinel-5P satellite. Plumes drifted in different directions and often exceeded 2 Dobson Units (DU) on 29 August 2022 (top left), 8 September 2022 (top middle), 20 October 2022 (top right), 29 November 2022 (bottom left), 14 December 2022 (bottom middle), and 17 January 2023 (bottom right). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during August and September remained relatively low, consisting of seismicity and gas-and-ash emissions and continued lava dome growth in the Arenas crater. Seismic events included volcanic tremor, tremor pulses, and very long period earthquakes. Gas-and-ash emissions were associated with some of these seismic signals. Additionally, occasional drumbeat-type seismicity, associated with rock fracturing and the evolution of the growing lava dome, was reported. Gas-and-ash emissions rose to 2 km above the summit during 4-5 August and drifted NW, W, and SW. As a result, ash fell in the nearby towns of Santa Rosa de Cabal (33 km W), Pereira (40 km WSW), Villamaría (28 km NW), and Manizales (25 km N). On 12, 18, and 25 August gas-and-steam plumes rose 2-3.2 km above the summit and drifted NW, W, and SW; a gas-and-ash emission was reported at 1751 on 18 August and rose 3.2 km above the summit and drifted WNW. During the week of 23-30 August gas-and-ash emissions resulted in ashfall in Villamaría and Manizales. Gas-and-steam emissions rose 2.3-2.5 km above the summit on 10, 13, 26, and 28 September and drifted NW, W, SW, WNW, N, and NE.

During October and November similar low levels of seismicity, dome growth, and plumes of gas-and-steam plumes (mostly sulfur dioxide) with some ash, persisted. Gas-and-steam emissions rose 1.8-2.9 km above the summit on 5, 13, 22, and 31 October and drifted in various directions. SGC reported that there was an increase in sulfur dioxide degassing values on 20 October, with the maximum recorded mass value of approximately 5,000 tons. Gas-and-steam emissions rose 1.8-2.2 km above the summit on 4, 8, 16, and 25 November and drifted NW, SW, SE, ESE, and NE. According to data from the Washington VAAC, ash plumes rose to 6.4-7.3 km altitude and drifted S and SE on 11 November based on satellite and webcam images. During 13-14 November ash plumes rose to 6.7 km altitude and drifted NE.

Seismicity and gas-and-steam emissions continued during December and January 2023. Pulses of gas-and-ash emissions associated with seismic signals were also reported. Additionally, people in the municipalities of Tolima and Manizales (Caldas) reported sightings of continuous ash emissions during 2-13 December. Gas-and-steam emissions rose 1.7-2.9 km above the summit on 2, 13, 21, and 31 December and drifted SW, SE, SSE, NE, W, and NW. On 7 December gas-and-steam and ash emissions rose 2 km above the summit and drifted W. Ashfall was detected in Dosquebradas (40 km WSW), Santa Rosa de Cabal (34 km W), and Pereira (40 km WSW in Risaralda), Manizales (27 km NW) and Villamaría (26 km NW in Caldas), and in the Los Nevados National Natural Park sector on 14 December and to the N near Tolima during 3-9 January as ash emissions continued intermittently for several hours at a time. Gas-and-steam emissions rose 1.3-2.9 km above the summit and drifted in different directions on 6, 14, 22, 25 January. An ash cloud was observed at 0706 on 6 January that caused ashfall in Villahermosa (27 km NE). On 23 January ashfall was reported in Manizales and on 29 January ash was remobilized and caused ashfall in Eje Cafetero.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www.sgc.gov.co/volcanes); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


August 2023 (BGVN 48:08) Citation IconCite this Report

Intermittent gas-and-ash plumes, ashfall events, and seismicity during February-July 2023

Nevado del Ruiz is located in central Colombia and covers more than 200 km2. It contains the 1-km-wide, 240-m-deep Arenas summit crater. Eruptions have been documented since 1570 CE. The current eruption period has been ongoing since November 2014 and more recently has consisted of intermittent ash emissions, lava dome growth, and thermal activity (BGVN 48:02). This report describes intermittent ash plumes, ashfall events, gas-and-steam emissions, and seismicity during February through July 2023, based on information from the Servicio Geologico Colombiano (SGC) and the Observatorio Vulcanológico y Sismológico de Manizales, the Washington Volcanic Ash Advisory Center (VAAC) notices, and various satellite data.

Occasional thermal anomalies were recorded during February through July 2023, with slightly stronger and more frequent anomalies occurring during mid-March through early May, according to MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data (figure 143). A total of seven thermal alerts were detected by the MODVOLC thermal alert system on 22 March, 7, 10, and 19 April, and 8 May. Some of that stronger thermal activity was captured in infrared satellite images on 7 February, 18 April, 23 April, and 8 May; weather clouds often obscured clear views of the summit (figure 144). According to data from the TROPOMI instrument on the Sentinel-5P satellite, sulfur dioxide plumes were frequently detected throughout the reporting period, many of which had maximum column densities that exceeded 2 Dobson Units (DU) and drifted in different directions (figure 145).

Figure (see Caption) Figure 143. Occasional thermal anomalies were detected at Nevado del Ruiz during February through July 2023, according to this MIROVA graph (Log Radiative Power). Slightly stronger and more frequent anomalies were detected during mid-March through early May. Only two anomalies were detected during mid-June and three during July. Courtesy of MIROVA.
Figure (see Caption) Figure 144. Infrared (bands B12, B11, B4) satellite images showing a strong thermal anomaly at the summit crater of Nevado del Ruiz on 18 April 2023 (left) and 8 May 2023 (right). Courtesy of Copernicus Browser.
Figure (see Caption) Figure 145. Sulfur dioxide emissions from Nevado del Ruiz were frequently captured with the TROPOMI instrument on the Sentinel-5P satellite during February through July 2023. Plumes drifted in different directions and often exceeded 2 Dobson Units (DU), as shown on 23 February 2023 (top left), 3 March 2023 (top middle), 15 April 2023 (top right), 13 May 2023 (bottom left), 19 June 2023 (bottom middle), and 28 July 2023 (bottom right). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during February and most of March was relatively low and consisted of gas-and-steam and ash emissions and low seismicity. Gas-and-steam plumes mainly composed of sulfur dioxide were reported once a week, rising 1.3-3.2 km above the summit and drifting in different directions during February, the latter of which was recorded on 8 February. During March gas-and-ash plumes rose 2-3 km above the summit and drifted NW and SW, the latter of which occurred on 11 March. On 4 March seismic signals increased in intensity and were associated with mostly continuous ash emissions with occasional pulses. Ashfall was reported in Manizales (27 km NW). Webcam images and reports from residents captured several ash emissions during 18-20 March. The emissions were associated with seismic signals indicating fluid movement in the conduit. A gas-and-ash emission rose 2.7 km above the summit and drifted SW at 0902 on 20 March and was visible from several municipalities including: Caldas, Tolima, and Risaralda. This plume was one of the tallest recorded in recent days. Two notable seismic increases were recorded on 24 and 31 March, mainly characterized by rock-fracturing earthquakes; seismicity mainly affected the SW flank. On 28 March there were 6,500 rock-fracturing events detected, the highest daily count since 2010. The number of daily events continued to increase and on 29 March the seismic network recorded 11,000 earthquakes, the highest daily count since seismic monitoring began in 1985. On 30 March, 11,600 earthquakes were detected. The Alert Level was raised to Orange, Level II (the second highest level on a four-level scale) on 30 March. In addition to the seismic swarm, seismic signals indicating fluid movement continued, some of which were associated with ash emissions. On 30 March ash emissions rose as high as 1.8 km above the summit and drifted NW and SW, and the next day, gas-and-ash emissions reached 1.3 km above the summit and drifted SW and SE. The total number of earthquakes on 31 March was 8,800.

During the first half of April, seismicity showed a gradual decrease in the number of recorded events, ranging from 5,000-10,000 events during 1-5 April to 500-3,000 during 6-13 April. For the rest of the month, about 100 events occurred each day. Gas-and-ash emissions rose 1.2 km above the summit and drifted SW and NW during 1-2 April; officials from the Los Navados National Natural Park reported ashfall in Brisas and Potosí. During 3-4 April gas-and-ash plumes rose 1.1-1.5 km above the summit and drifted SW and NW. On 5 April at 0216 a strong earthquake of M 3.9 was recorded and felt by residents in Villamaría (28 km NW). SGC noted that this was the highest magnitude earthquake recorded in the SW part of the volcano since instrumental monitoring was installed in 1985. According to a news article, 87 people had self-evacuated after the government called for a voluntary evacuation of roughly 2,500 families. Continuous gas-and-ash emissions rose 1.2-1.8 km above the summit and drifted SW, SE, NE, and E during 6-10 April, based on webcam images and reports from residents in La Cabaña (Murillo, Tolima) (figure 146). Drumbeat-type seismicity associated with the growth of the lava dome located at the bottom of the Arenas crater was detected on 8, 13, 14, 17, 18, and 21 April. During 11-13 April gas-and-ash plumes rose 1.8-2.5 km above the summit and drifted N, NE, SW, and NW, and there were reports of ashfall in Villamaría (Caldas) and Filandia (Quindío). As many as 2,000 daily drumbeat-type events were also recorded on 13 April. During 0759-1113 on 14 April and from 1515 on 14 April to 0057 on 15 April seismicity intensified and corresponded to continuous ash emissions that rose as high as 1.5 km above the summit and drifted SW, as observed by residents in Murillo and Manizales. During 16-19 and 21-22 April gas-and-steam plumes possibly containing some ash rose 1.1-1.8 km above the summit and drifted in different directions; ashfall was reported in Anzoátegui, Tolima on 18 April after an ash plume was reported at 0711. Pulsating ash emissions were visible in webcam images during 23-29 April, rising 1.1-2.5 km above the summit and drifting in multiple directions. The ash emissions on 25 April were visible from Tolima, Caldas, and Risaralda. The ash emission reported at 0837 on 27 April was followed by reports of ashfall in Manizales a few hours later.

Figure (see Caption) Figure 146. Photo of an ash cloud from Nevado del Ruiz as seen from Murillo, Tolima, Colombia taken on 7 April 2023. Courtesy of Joaquin Sarmiento via CNN.

According to SGC, the sulfur dioxide emission rate increased during the first week of May compared to those emitted during April. Drumbeat-type events continued to occur on 6, 16, 17, 26, 27, and 31 May. Gas-and-steam plumes rose 1.9 km and 2.7 km above the summit on 12 and 25 May, respectively, and drifted generally W. A sulfur odor was reported in several parts of Manizales on 15 May. A significant thermal anomaly was observed within the crater on 31 May. On that same day, a sulfur odor was reported in Cerro Gualí.

SGC reported that the rate of sulfur dioxide emissions had decreased in June compared to May. Several short-duration drumbeat-type events were recorded on 1, 5, and 26 June. Gas-and-steam emissions that possibly contained some ash rose 2-2.4 km above the summit and drifted NW on 4 June. As a result, minor ashfall was reported in Manizales and Villamaría. Continuous ash emissions was visible in webcam images during the afternoon of 20 June and ashfall was reported in Manizales. Ash emissions rose as high as 1.3 km above the summit on 21 June and drifted WSW; they continued to rise as high as 4 km above the summit that same day. Crater incandescence was observed, coinciding with pulsating ash emissions during 20-23 June. Gas-and-ash plumes rose 900-1,800 m above the summit during 24-27 June and drifted NW. Minor ashfall was reported in Villamaría and Manizales on 22 and 25 June, respectively. The Alert Level was lowered to Yellow, Level III (the second level on a four-level scale) on 27 June. SGC noted that monitoring data was more stable in recent weeks, thermal anomalies at the lava dome were less intense, ash emissions had decreased, and gas-and-steam emissions remained relatively stable.

Low seismicity and gas-and-ash emissions were reported during July. Drumbeat-type events were detected on 1, 3, 7, 8, 10, 12, 15, 17, 24, 26, 27, 28, and 29 July. Incandescence was observed on 4 July, accompanied by an ash emission at 2048 that rose 2km above the summit and drifted NW and SW. Occasional gas-and-steam plumes mainly consisting of sulfur dioxide rose 1.2-1.8 km above the summit and drifted NW and WSW. During 24-25 July a gas-and-ash plume rose 1.8 km above the summit and drifted NW and WNW, causing light ashfall in Manizales. On 27 July at 0617 a gas-and-ash plume rose 2.3-3.5 km above the summit and drifted NW and WNW; light ashfall was reported in Manizales on several occasions.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www.sgc.gov.co/volcanes); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard MD 20771, USA (URL: https://so2.gsfc.nasa.gov/); Copernicus Data Space Ecosystem, European Space Agency (URL: https://dataspace.copernicus.eu/browser/); CNN, One CNN Center, 12th Floor, North Tower, Atlanta, GA 30303, USA, “A deadly volcano could erupt ‘within days or weeks’ in Colombia. But only a small fraction of locals have evacuated”(URL: https://edition.cnn.com/2023/04/15/americas/nevado-del-ruiz-colombia-volcano-intl-latam/index.html).

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Eruptive History

There is data available for 20 confirmed Holocene eruptive periods.

2014 Nov 18 - 2024 Oct 17 (continuing) Confirmed Eruption VEI: 2

Episode 1 | Eruption Arenas crater
2014 Nov 18 - 2017 Oct 11 Evidence from Observations: Reported

List of 204 Events for Episode 1 at Arenas crater

Start Date End Date Event Type Event Remarks
2014 Oct 15
(in or after)
2015 Apr 15
(in or before)
Thermal Anomaly The MIROVA signal from the MODIS thermal anomaly data shows persistent thermal activity from late October 2014 through mid-April 2015.
2014 Nov 18 2014 Nov 21 Seismicity (tremor) Three periods of continuous tremor associated with ash emissions were recorded.
2014 Nov 18 2014 Nov 21 Ash Plume Three periods of continuous tremor associated with ash emissions were recorded. Ash emissions were verified in satellite imagery and by reports from nearby communities. The ash dispersed generally SE and SW.
2014 Nov 19 2014 Nov 21 Ashfall The Unidad Nacional de Gestion de Riesgo de Desastres (UNGRD, National Disaster Risk Management Unit) coordinated an overflight and observed fresh ash deposits on the S flank.
2014 Nov 28 2014 Nov 29 Seismicity (tremor) Three periods of continuous tremor associated with ash emissions were recorded.
2014 Nov 28 2014 Nov 29 Ash Plume Three periods of continuous tremor associated with ash emissions were recorded.
2014 Nov 29    - - - - Ashfall Ash was observed on the N side of the Arenas crater in the early morning after a lengthy period of continuous tremor was recorded the previous day.
2014 Dec 15 2014 Dec 19 Ash Plume On 15 December seismic signals indicating ash emissions were detected, and then confirmed by a local webcam and nearby residents. The Washington VAAC also noted an ash emission based on a pilot observation extending 16 km S at 7.6 km altitude. The next day they reported a narrow plume of minor volcanic ash extending 22 km SW of the summit at 6.1 km altitude. On 18 and 19 December the Washington VAAC reported ash plumes to altitudes of 7.9 and 9.1 km, respectively, that drifted SSW and dissipated within a few hours.
2014 Dec 19    - - - - VEI (Explosivity Index) VEI 2
2014 Dec 26
(in or before)
   - - - - Ashfall A satellite image clearly shows ash deposits in nearly all directions from the Arenas crater. Ashfall was reported during this time in the Caldas (W) and Risaralda (SW) departments.
2015 Jan 4 2015 Jan 29 Seismicity (tremor) SGC reported seven episodes of continuous tremor on 4, 7, 14, 24, 26, 28, and 29 January, almost all of which were associated with ash emissions.
2015 Jan 4 2015 Jan 29 Ash Plume SGC reported seven episodes of continuous tremor on 4, 7, 14, 24, 26, 28, and 29 January, almost all of which were associated with ash emissions.
2015 Jan 4 2015 Jan 29 Ashfall Ashfall was reported several times after these episodes in the Eje Cafetero area to the W of Ruiz.
2015 Jan 7    - - - - Ashfall According to a news article, increased ash emissions at Nevado del Ruiz prompted the closure of the La Nubia airport.
2015 Jan 14    - - - - Ash Plume The Washington VAAC reported an ash plume visible in satellite imagery extending 16 km SW of the summit at 6.7 km altitude.
2015 Feb 1
(in or after)
2015 Feb 28
(in or before)
Ash Plume Occasional minor ash emissions were reported during February 2015 during periods of continuous tremor, but most of the emissions were steam and gas.
2015 Feb 9    - - - - Ashfall Ashfall was reported in El Libano (29 km E), El Oso (10 km SE), and Murillo (17 km E).
2015 Mar 7    - - - - Ash Plume According to the VAAC, the Bogota MWO reported that an ash plume rose to an altitude of 6.1 km and drifted WNW.
2015 Mar 8
(in or after)
2015 Mar 31
(in or before)
Seismicity (tremor) Emissions associated with tremors contained gases and minor amounts of ash.
2015 Mar 8
(in or after)
2015 Mar 31
(in or before)
Ash Plume Emissions associated with tremors contained gases and minor amounts of ash.
2015 Mar 8    - - - - Ashfall Ashfall was reported after a tremor in the evening by personnel from the Parque Nacional Natural Los Nevados (PNNN), the Observatorio Vulcanológico y Sismológico de Manizales (OVSM), and from the municipalities of Manizales and Villamaria (27 km NW).
2015 Apr 9 2015 Apr 29 Ash Plume Confirmed ash emissions were observed on 9, 22, 27, and 29 April.
2015 Apr 20    - - - - Ashfall Ashfall was reported in the municipalities of Manizales and Villamaría.
2015 Apr 22    - - - - Ash Plume The Washington VAAC reported a small puff of gas and minor amounts of ash visible in satellite imagery at 7.3 km altitude drifting W about 40 km before dissipating.
2015 May 1
(in or after)
2015 May 31
(in or before)
Ash Plume Ash emissions were photographed by the webcams located in the Azufrado and Cerro Guali regions on at least eleven dates during May 2015.
2015 May 19    - - - - Ash Plume The Washington VAAC reported possible emissions, but extensive weather clouds prevented satellite observations.
2015 May 26    - - - - Ash Plume The Washington VAAC reported that an ash emission was visible in the webcam and reported by the Air Force Weather Agency (AFWA).
2015 Jun 1
(in or after)
2015 Jun 30
(in or before)
Seismicity (tremor) Most of the frequent episodes of volcanic tremor during June were also associated with ash emissions which were photographed at least six times during the month.
2015 Jun 1
(in or after)
2015 Jun 30
(in or before)
Ash Plume Most of the frequent episodes of volcanic tremor during June were also associated with ash emissions which were photographed at least six times during the month.
2015 Jun 6    - - - - Ash Plume The Observatory at Manizales reported ash moving WNW at about 800 m above the summit; weather clouds obscured satellite observations by the Washington VAAC.
2015 Jul 1
(in or after)
2015 Jul 31
(in or before)
Ashfall A significant increase in ashfall was reported during July 2015, including in the regions of Caldas, Tolima, and Risaralda, as well as by officials in the Park (PNNN).
2015 Jul 6    - - - - Ash Plume The Observatory at Manizales (OVSM) reported an ash plume at about 7.3 km altitude, but it was not observed in satellite data due to weather.
2015 Jul 13    - - - - Ash Plume The Washington VAAC noted ash emissions visible in satellite data and the webcam, with a plume at 7 km altitude drifting NW a few tens of kilometers before dissipating.
2015 Jul 18 2015 Jul 20 Ash Plume OVSM reported plumes at about 6 km moving S and W during 18-20 July.
2015 Jul 23    - - - - Seismicity (volcanic) Seismic signals indicating emissions were reported and observed in the webcam, according to the Washington VAAC.
2015 Jul 23    - - - - Ash Plume Seismic signals indicating emissions were reported and observed in the webcam, according to the Washington VAAC.
2015 Jul 26 2015 Jul 28 ± 2 days Ash Plume SGC noted seismic tremors and a plume on the morning of 26 July that rose to 3 km above the summit (8.2 km altitude); near summit-level emissions were also observed via the webcam on 26 and 27 July. Seismic data indicated continued occasional bursts of ash drifting W to WSW during the next few days.
2015 Jul 26 2015 Jul 28 ± 2 days Ashfall Ashfall was reported downwind in the municipalities of Chinchina (33 km NW), Palestina (35 km NW), Santa Rosa de Cabal (33 km W), Dosquebradas (40 km WSW), and Pereira (40 km WSW).
2015 Jul 31    - - - - Thermal Anomaly The Washington VAAC reported bright thermal anomalies visible in satellite images; a brief increase in seismicity was detected, and the thermal anomaly was weaker in subsequent images.
2015 Aug 6    - - - - Ash Plume Based on satellite images, the Washington VAAC reported that two small ash puffs rose to an altitude of 7.3 km and drifted NW. Ash emissions later that day drifted over 20 km NW.
2015 Aug 12    - - - - Ash Plume The Washington VAAC reported a possible plume with minor ash at 6.7 km drifting 55 km NW from the summit.
2015 Aug 20    - - - - Lava dome SGC first noticed an unusual pattern of seismicity known as a "drumbeat" signal, for which they issued a special report on 20 August 2015. The "drumbeat" signal is characterized by discrete episodes of short duration (about 30 minutes each) that repeat at regular time intervals and show similar waveforms and energy. They are interpreted by volcanologists to represent phenomena associated with the ascent of high-viscosity magma to the surface and thus are an indicator of near-surface extrusion or dome building.
2015 Aug 23    - - - - Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico and Sismológico de Manizales reported that volcanic tremor associated with ash emissions continued.
2015 Aug 23    - - - - Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico and Sismológico de Manizales reported that volcanic tremor associated with ash emissions continued.
2015 Aug 23    - - - - Ashfall Ashfall was confirmed by officials from Civil Aviation and the Parque Nacional Natural de los Nevados, as well as residents in Pereira.
2015 Aug 28 2015 Aug 30 Ash Plume A brief emission containing minor ash, observed in a webcam, was reported by the Washington VAAC as extending about 35 km W. Ongoing emissions rising a few hundred meters above the summit with occasional small bursts of ash continued for the next two days.
2015 Aug 31    - - - - Seismicity (tremor) A tremor event was the largest since 18 November 2014.
2015 Aug 31    - - - - Ashfall Ashfall affected numerous cities and municipalities, including Manizales (30 km NW) (with the largest particle sizes towards the E side of the city), La Linda, La Cabaña (36 km NW), and trace amounts in Santagueda (40 km NW), Arauca (48 km NW), Kilómetro 41, Villamaría (27 km NW), Chinchiná, Palestina, and Neira (36 km NW).
2015 Sep 1
(in or after)
2015 Sep 7
(in or before)
Ash Plume Water-vapor-and-gas plumes rose 1.4 km above the crater and drifted NW, and were sometimes tinged gray due to the presence of ash.
2015 Sep 1
(in or after)
2015 Sep 7
(in or before)
Ashfall Ashfall was reported in Manizales (30 km NW) and Pereira (40 km WSW).
2015 Sep 1
(in or after)
2015 Sep 7
(in or before)
Incandescence Incandescence was recorded by a webcam installed near the volcano.
2015 Sep 3 2015 Sep 30 Ash Plume The Washington VAAC issued advisory reports on 3, 12-15, 17, 23-24, 27, and 29-30 September 2015. Plume altitudes ranged from 5.5 to 7.9 km.
2015 Sep 4    - - - - Seismicity (tremor) Incandescence observed in a webcam was followed by a high-energy tremor.
2015 Sep 4    - - - - Incandescence Incandescence observed in a webcam was followed by a high-energy tremor.
2015 Sep 8    - - - - Lava dome SGC recorded drumbeat seismicity.
2015 Sep 12 2015 Sep 15 Ash Plume The ash plumes reported by the Washington VAAC on 12 and 13 September rose to 7.9 km and drifted in several directions. Ash was moving to the NW below 5.2 km and extended for over 90 km; between 5.2 and 7.9 km altitude it extended about 80 km SW. Ongoing emissions with small bursts of ash continued through 15 September with a new emission to 7.6 km around 1600 that day.
2015 Sep 15
(in or after)
2015 Sep 21
(in or before)
Ashfall Ashfall was reported in Manizales (30 km NW) and Pereira (40 km WSW).
2015 Sep 17 2015 Sep 18 Seismicity (tremor) The OVSM reported a strong seismic signal at 0728 on 17 September, but weather clouds blocked observation from satellite imagery of the potential ash plume. The largest tremor of the month occurred in the afternoon of 18 September and ash emissions were verified in the webcams as well as by SGO officials doing fieldwork in the area.
2015 Sep 18 2015 Sep 19 Ash Plume The largest tremor of the month occurred in the afternoon of 18 September and ash emissions were verified in the webcams as well as by SGO officials doing fieldwork in the area; ash emissions were also observed in the webcam on 19 September at 1556.
2015 Sep 22    - - - - Ash Plume SGO reported a seismic event that produced water-vapor, gas, and ash plumes that rose 2 km above the crater and drifted mainly NW.
2015 Sep 22
(in or after)
2015 Sep 28
(in or before)
Thermal Anomaly Thermal anomalies over the crater were sometimes detected in satellite images; a significant anomaly was detected on 26 September.
2015 Sep 27 2015 Sep 29 Ash Plume An ash plume was confirmed by the Washington VAAC in a satellite image on 27 September extending about 70 km WNW at 6.1 km altitude. An advisory issued on 29 September noted ash to 8.5 km within 16 km of the summit. SGO noted that the 29 September emissions were observed both E and W of the volcano.
2015 Sep 28    - - - - Seismicity (tremor) A pulse of tremor at 1633 was accompanied by an ash emission that drifted E and W.
2015 Sep 28 2015 Sep 30 Thermal Anomaly Minor thermal anomalies over the crater were detected in satellite images on 28 and 30 September.
2015 Oct 1
(in or after)
2015 Oct 31
(in or before)
Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions.
2015 Oct 1
(in or after)
2015 Oct 31
(in or before)
Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions.
2015 Oct 5    - - - - Ash Plume The Washington VAAC confirmed continuous ash emissions at 7 km altitude extending about 25 km W of the summit.
2015 Oct 7 2015 Oct 10 Thermal Anomaly Thermal anomalies over the crater were detected in satellite images during 7 and 9-10 October.
2015 Oct 8    - - - - Ash Plume A gas, steam, and ash plume rose 1.7 km and drifted NW.
2015 Oct 17    - - - - Ash Plume A gas, steam, and ash plume rose 1.8 km and drifted NW.
2015 Oct 22    - - - - Ash Plume A discrete emission of ash rose to 9.1 km altitude and drifted N.
2015 Oct 22    - - - - Lava dome SGC recorded drumbeat seismicity.
2015 Oct 26    - - - - Ash Plume SGO reported ash emissions observed in webcams.
2015 Oct 30    - - - - Ash Plume A gas, steam, and ash plume rose 1.7 km and drifted NW.
2015 Nov 4 2015 Nov 27 Thermal Anomaly Thermal anomalies increased in frequency and were observed on 4, 18, 20, 22, 26, and 27 November.
2015 Nov 5 2015 Nov 29 Ash Plume SGC confirmed ash emissions on 5, 10, 14, 27, and 29 November.
2015 Nov 13    - - - - Lava dome The "drumbeat" signal was again briefly recorded.
2015 Nov 14    - - - - Ash Plume The Washington VAAC reported an ash plume at 6.4 km altitude moving SW. SGC captured images of the ash plume from two different webcams.
2015 Nov 17    - - - - Ash Plume A gas, steam, and ash plume rose 2 km and drifted NW and SW.
2015 Dec 1
(in or after)
2015 Dec 15
(in or before)
Seismicity (tremor) Minor episodes of volcanic tremor with ash emissions were reported by SGC during the first two weeks of December 2015.
2015 Dec 1
(in or after)
2015 Dec 15
(in or before)
Ash Plume Minor episodes of volcanic tremor with ash emissions were reported by SGC during the first two weeks of December 2015.
2015 Dec 3    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2015 Dec 20    - - - - Seismicity (tremor) A significant volcanic tremor with ash emissions occurred, and ashfall was reported by SGC officials, PNNN personnel, and residents near the volcano and in the city of Manizales.
2015 Dec 20    - - - - Ash Plume A significant volcanic tremor with ash emissions occurred, and ashfall was reported by SGC officials, PNNN personnel, and residents near the volcano and in the city of Manizales. The Washington VAAC noted the ash plume at 6.1 km altitude with 25 km of the summit.
2015 Dec 20    - - - - Ashfall A significant volcanic tremor with ash emissions occurred, and ashfall was reported by SGC officials, PNNN personnel, and residents near the volcano and in the city of Manizales.
2015 Dec 22    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2015 Dec 26    - - - - Thermal Anomaly Two MODVOLC thermal alerts were issued.
2015 Dec 28    - - - - Ash Plume A gas, steam and ash plume rose 1.7 km and drifted NW on 28 December.
2015 Dec 31    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2016 Jan 6    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2016 Jan 9 2016 Jan 13 Thermal Anomaly Five MODVOLC thermal alerts were issued.
2016 Jan 16 2016 Jan 18 Thermal Anomaly Two MODVOLC thermal alerts were issued.
2016 Jan 22    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2016 Jan 25 2016 Jan 29 Thermal Anomaly Five MODVOLC thermal alerts were issued.
2016 Jan 26 2016 Feb 1 Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity at Nevado del Ruiz was characterized by long-period earthquakes and continuous volcanic tremor associated with gas-and-ash emissions.
2016 Jan 26    - - - - Ash Plume A gas, steam, and ash plume rose 850 m and drifted NW.
2016 Jan 26 2016 Feb 1 Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity at Nevado del Ruiz was characterized by long-period earthquakes and continuous volcanic tremor associated with gas-and-ash emissions.
2016 Feb 1 2016 Feb 3 Thermal Anomaly Two MODVOLC thermal alerts were issued.
2016 Feb 7    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2016 Feb 9 2016 Feb 15 Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity at Nevado del Ruiz was characterized by long-period earthquakes and pulses of volcanic tremor associated with gas-and-ash emissions.
2016 Feb 9 2016 Feb 15 Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 9-15 February seismicity at Nevado del Ruiz was characterized by long-period earthquakes and pulses of volcanic tremor associated with gas-and-ash emissions.
2016 Feb 13    - - - - Ash Plume A gas, steam, and ash plume rose 1.5 km and drifted NW.
2016 Feb 24    - - - - Ash Plume Based on notices from the Bogota MWO, pilot observations, and wind data, the Washington VAAC reported that an ash plume possibly rose to altitudes of 5.5-6.1 km and drifted NW and S.
2016 Feb 29    - - - - Ash Plume According to the VAAC, SGC reported an ash emission.
2016 Mar 3    - - - - Seismicity (tremor) SGC reported that an episode of volcanic tremor at Nevado del Ruiz began at 0923 and was associated with an ash plume that rose 3 km above the crater.
2016 Mar 3    - - - - Ash Plume SGC reported that an episode of volcanic tremor at Nevado del Ruiz began at 0923 and was associated with an ash plume that rose 3 km above the crater. Based on satellite and webcam images, the Washington VAAC stated that an ash plume rose to an altitude of 9.1 km (about 800 m higher than the SGC estimate) and drifted NW. Later that day satellite images detected an ash plume drifting 40 km W.
2016 Mar 8 2016 Mar 14 Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity was characterized by long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions.
2016 Mar 8 2016 Mar 14 Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity was characterized by long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions. A gas, steam, and ash plume rose 1.8 km and drifted SW on 8 March. The next day an episode of volcanic tremor was associated with an ash emission recorded by the webcam and observed by National Park officials.
2016 Mar 18    - - - - Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0606 an episode of volcanic tremor was associated with an ash emission that rose 1.7 km above Nevado del Ruiz.
2016 Mar 18    - - - - Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0606 an episode of volcanic tremor was associated with an ash emission that rose 1.7 km above Nevado del Ruiz.
2016 Mar 28 2016 Mar 29 Ash Plume Based on an ASHTAM (a special Notice to Airmen for airborne ash), the Washington VAAC reported a possible emission on 28 March. Ash was not identified in satellite images, though a thermal anomaly was detected. A period of increased seismicity was detected the next day, and observers reported another possible ash emission.
2016 Mar 28    - - - - Thermal Anomaly A thermal anomaly was detected.
2016 Mar 31    - - - - Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0804 an episode of short-duration volcanic tremor was associated with an ash emission that rose 3.5 km above Nevado del Ruiz. According to the Washington VAAC the ash plume drifted NW and SW.
2016 Mar 31    - - - - Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0804 an episode of short-duration volcanic tremor was associated with an ash emission that rose 3.5 km above Nevado del Ruiz. According to the Washington VAAC the ash plume drifted NW and SW.
2016 Apr 12 2016 Apr 18 Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity was characterized by long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions.
2016 Apr 12 2016 Apr 18 Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity was characterized by long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions. A gas, steam, and ash plume rose 1.5 km and drifted NW and NE on 12 April.
2016 Apr 12 2016 Apr 18 Thermal Anomaly Thermal anomalies near Arenas Crater were periodically identified in satellite images.
2016 Apr 16    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2016 Apr 22 2016 Apr 25 Ash Plume Based on an SGC notice, the Washington VAAC reported that ash plumes drifted over 10 km on 22 April and almost 20 km on 24 April. Possible ash emissions rose from the volcano on 25 April.
2016 Apr 29    - - - - Ashfall Ashfall was reported in Murillo.
2016 May 2    - - - - Ash Plume Based on a SGC notice, the Washington VAAC reported that an ash emission rose to an altitude of 7 km and drifted NW.
2016 May 5    - - - - Ash Plume Based on webcam views and information from SGC, the Washington VAAC reported that an ash emission rose to an altitude of 6.7 km and drifted NW.
2016 May 10 2016 May 30 Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity was characterized by long-period and very-long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions.
2016 May 10 2016 May 30 Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity was characterized by long-period and very-long-period earthquakes, episodes of continuous tremor, and pulses of volcanic tremor associated with gas-and-ash emissions.
2016 May 11 2016 May 12 Thermal Anomaly Thermal anomalies near Arenas Crater were identified in satellite images.
2016 May 12    - - - - Ash Plume A gas, steam, and ash plume rose 1.7 km and drifted NW and W.
2016 May 17    - - - - Ash Plume Based on information from SGC, the Washington VAAC reported that an ash emission rose to an altitude of 7 km.
2016 May 20    - - - - Ashfall Ashfall was reported in La Florida, Manizales.
2016 May 22    - - - - Ash Plume According to a news article an ash emission prompted closure of the La Nubia airport in Manizales. Later that day a gas, steam, and ash plume rose 2.5 km and drifted NW and W.
2016 May 25    - - - - Ash Plume A gas, steam, and ash plume rose 1.8 km above the crater rim and drifted NW and W.
2016 May 27    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2016 May 27    - - - - Thermal Anomaly A minor thermal anomaly near Arenas Crater was detected in satellite images.
2016 Jun 27 2016 Jun 28 Seismicity (tremor) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0822 on 27 June and at 0748 on 28 June episodes of volcanic tremor were associated with ash emissions that rose 1.8 and 0.9 km above Nevado del Ruiz, respectively.
2016 Jun 27 2016 Jun 28 Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 0822 on 27 June and at 0748 on 28 June episodes of volcanic tremor were associated with ash emissions that rose 1.8 and 0.9 km above Nevado del Ruiz, respectively. The emissions were confirmed by national park authorities and local residents. A gas, steam, and ash plume rose 850 m above the crater rim and drifted NW on 28 June.
2016 Jul 6 2016 Jul 7 Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that a webcam recorded minor ash emissions rising from Nevado del Ruiz.
2016 Jul 8    - - - - Ash Plume Based on notices from the Bogota MWO, satellite images, and model data, the Washington VAAC reported that ash plumes rose to altitudes of 6.1-6.4 km and drifted W.
2016 Jul 9    - - - - Thermal Anomaly A thermal anomaly was visible.
2016 Jul 12 2016 Jul 18 Lava dome Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 12-18 July seismicity at Nevado del Ruiz slightly increased as compared to levels the week before. Several episodes of “drumbeat” earthquakes were recorded during 13, 15, and 16-17 July. These signals were low energy and indicated a growing lava dome.
2016 Jul 13 2016 Jul 17 Ash Plume Gas, steam, and ash plumes rose at most 500 m above the crater rim and drifted NW on 13, 14, 16, and 17 July.
2016 Jul 24    - - - - Ash Plume Based on notices from the Bogota MWO and model data, the Washington VAAC reported that a possible ash plume rose to an altitude of 7.2 km.
2016 Jul 26    - - - - Ash Plume An ash plume recorded by the webcam and identified in satellite images rose to an altitude of 6.9 km and drifted W.
2016 Jul 29    - - - - Ash Plume A gas, steam, and ash plume rose 700 m above the crater rim and drifted NW and W.
2016 Aug 6    - - - - Ash Plume A gas, steam, and ash plume rose 850 m above the crater rim and drifted NW and W.
2016 Aug 19    - - - - Ash Plume Based on information from the Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales, the Washington VAAC reported that an ash plume rose to an altitude of 6.9 km and drifted W and SW.
2016 Aug 24 2016 Aug 29 Thermal Anomaly Thermal anomalies were detected on 24 and 29 August.
2016 Aug 26 2016 Aug 28 Seismicity (tremor) A period of tremor that started at 1747 on 26 August was associated with an ash emission that rose 900 m above the crater. A gas-and-ash plume, associated with a seismic signal at 1050 on 27 August, was confirmed by a pilot. Based on webcam images and seismic signals, an ash plume rose 1.3 km and drifted NW on 28 August.
2016 Aug 26 2016 Aug 29 Ash Plume A period of tremor that started at 1747 on 26 August was associated with an ash emission that rose 900 m above the crater. A gas-and-ash plume, associated with a seismic signal at 1050 on 27 August, was confirmed by a pilot. Based on webcam images and seismic signals, an ash plume rose 1.3 km and drifted NW on 28 August. Gas, steam, and ash plumes occasionally rose 2.3 km above the crater rim and drifted NW and W on 29 August.
2016 Sep 2 2016 Sep 6 Ash Plume Based on notices from the Bogota MWO, satellite and webcam images, and model data, the Washington VAAC reported that during 2-3 September ash plumes rose to altitudes of 6.1-6.4 km and drifted W and NW. SGC noted that gas, steam, and ash plumes occasionally rose 1.8 km above the crater rim and drifted NW and W on 4 and 6 September.
2016 Sep 13    - - - - Ash Plume Based on satellite images, the Washington VAAC reported that ash emissions at Nevado del Ruiz began at 0615, producing a plume that rose to an altitude of 6.1 km and drifted W. By 1345 the ash had dissipated.
2016 Sep 15    - - - - Ash Plume Based on notices from the Bogota MWO and model data, the Washington VAAC reported that an ash plume rose to an altitude of 6.1 km and drifted W.
2016 Sep 21    - - - - Ash Plume Gas, steam, and ash plumes rose 700 m above the crater and drifted NW.
2016 Sep 29    - - - - Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that a webcam recorded an ash plume rising at 0558. Based on information from the Bogota MWO, the Washington VAAC reported on the same day that an ash plume rose to an altitude of 6.1 km and drifted WSW. Later that day ASHTAM reports indicated an ash emission to an altitude of 8.5 km and drifted 13 km S, though cloud cover prevented webcam and satellite image views.
2016 Oct 3    - - - - Ash Plume An ash emission reported by the Bogota MWO rose to an altitude of 6.1 km and drifted NE.
2016 Oct 5    - - - - Seismicity (tremor) At 1746 an episode of volcanic tremor was associated with ash emissions recorded by area webcams.
2016 Oct 5    - - - - Ash Plume At 1746 an episode of volcanic tremor was associated with ash emissions recorded by area webcams.
2016 Oct 8    - - - - Ash Plume Gas, steam, and ash plumes rose 2 km above the crater and drifted NE.
2016 Oct 12 2016 Oct 17 Ash Plume Gas-and-ash plumes were visible on 12 and 13 October. On 15 October gas, steam, and ash plumes rose as high as 2.5 km above the crater and drifted NW. The number of long-period events increased during 1800-2300 on 17 October; some of the signals were associated with gas-and-ash emissions.
2016 Oct 18 2016 Oct 20 Ash Plume A steam, gas, and ash plume rose 2 km above the crater and drifted W on 18 October. The Washington VAAC reported that on 19 and 20 October ash plumes rose to altitudes of 7.3 and 6.1 km and drifted NW and SW, respectively.
2016 Oct 18 2016 Oct 20 Thermal Anomaly Two low-energy thermal anomalies were detected on 18 and 20 October.
2016 Oct 20    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2016 Oct 27 2016 Oct 30 Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismic signals indicating ash emissions from Nevado del Ruiz were recorded at 0608 on 27 October and 1341 on 30 October. The ash plume from the 27 October event drifted NE; weather clouds prevented confirmation of the second event.
2016 Nov 16    - - - - Ash Plume Based on information from the Bogota MWO, the Washington VAAC reported an ash plume from Nevado del Ruiz rose to an altitude of 6.7 km and drifted NE. Weather clouds prevented satellite views.
2016 Dec 2    - - - - Ash Plume A gas, water vapor, and ash plume rose 2 km above the crater rim and drifted between SW and NW directions.
2016 Dec 7    - - - - Thermal Anomaly A low-energy thermal anomaly near Arenas Crater was detected by the MIROVA system.
2016 Dec 9    - - - - Ash Plume Gas and water vapor plumes sometimes containing ash rose 2 km above the crater rim and drifted between SW and NW directions.
2016 Dec 19    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2016 Dec 29    - - - - Thermal Anomaly A low-energy thermal anomaly was identified by the MIROVA system.
2016 Dec 30    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2017 Jan 1    - - - - Ash Plume Based on satellite and wind information, the Washington VAAC reported a possible ash emission moving W at 7.6 km altitude.
2017 Jan 2    - - - - Ash Plume A gas, water vapor, and ash plume rose 1.2 km above the crater rim and drifted between SW and NW directions.
2017 Jan 3 2017 Jan 9 Seismicity (volcanic) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported seismic signals were associated with gas-and-ash emissions, as confirmed by webcam images and officials in the Parque Nacional Natural los Nevados.
2017 Jan 3 2017 Jan 9 Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported seismic signals were associated with gas-and-ash emissions, as confirmed by webcam images and officials in the Parque Nacional Natural los Nevados.
2017 Jan 6    - - - - Ash Plume SGC reported that a gas, water vapor, and ash plume rose 2.5 km above the crater rim and drifted between SW and NE directions.
2017 Jan 8    - - - - Seismicity (volcanic) SGC reported that a seismic event at 0745 was associated with an ash emission which drifted SW.
2017 Jan 8    - - - - Ash Plume A seismic event at 0745 was associated with an ash emission which drifted SW. The Washington VAAC noted the plume was reported to 7.3 km altitude moving E but was not visible in satellite imagery under mostly cloudy skies.
2017 Jan 13    - - - - Ash Plume Based on information from Servicio Geológico Colombiano (SGC), the Washington VAAC reported that an ash emission rose to an altitude of 7 km and drifted N. Weather clouds prevented satellite views of the emission, and the webcam recorded gas-and-steam emissions with possible ash content.
2017 Jan 13    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2017 Jan 22    - - - - Seismicity (volcanic) Drumbeat seismicity was recorded.
2017 Jan 22    - - - - Ash Plume Based on satellite and Bogota MWO information, the Washington VAAC reported an eruption with an ash plume that rose to 8.2 km altitude and drifted SW. Two discrete ash emissions were observed in satellite imagery.
2017 Jan 22 2017 Jan 24 Thermal Anomaly Two MODVOLC thermal alerts were issued.
2017 Jan 31    - - - - Ash Plume Based on analysis of satellite images, the Washington VAAC reported that an ash plume rose to an altitude of 7 km and drifted W.
2017 Feb 9    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2017 Feb 18    - - - - Ash Plume SGO reported that gas, steam, and ash plumes rose 1.2 km above the crater rim and drifted NE, SE, and SW.
2017 Feb 19    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2017 Feb 23 2017 Feb 26 Seismicity (volcanic) Seismicity was high with earthquakes located at depths of 1.1-4 km, in areas SW of the volcano.
2017 Feb 25    - - - - Ash Plume SGO reported that gas, steam, and ash plumes rose 2 km above the crater rim and drifted NW and SW.
2017 Mar 4    - - - - Ash Plume Based on satellite images, the Washington VAAC reported that an ash plume rose to an altitude of 7.6 km and drifted over 31 km NW.
2017 Mar 4    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2017 Mar 17 2017 Mar 20 Ash Plume Based on satellite and webcam images, the Washington VAAC reported that on 17 and 20 March ash plumes rose to an altitude of 6.1 km and drifted NW and SW.
2017 Mar 26    - - - - Ash Plume Based on info from Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales, the Washington VAAC reported that ash plumes rose to an altitude of 7 km.
2017 Mar 27    - - - - Ash Plume The observatory reported that at 1029 a gas-and-ash plume rose 1.6 km above the crater rim and drifted E.
2017 Apr 3    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2017 Apr 4    - - - - Ash Plume Based on satellite and Bogota MWO information, the Washington VAAC reported an ash emission moving W at 7.0 km altitude.
2017 Apr 10 2017 Apr 11 Seismicity (volcanic) A period of short-duration and very low-energy drumbeat seismicity was recorded.
2017 Apr 10    - - - - Ash Plume SGO reported that gas, steam, and ash plumes rose 1.5 km above the crater rim and drifted NW.
2017 Apr 12    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2017 Apr 14    - - - - Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that at 1822 a seismic event was recorded, associated with a gas-and-ash emission recorded by the webcam, that rose almost 1.2 km above the crater.
2017 Apr 16    - - - - Ash Plume Based on satellite and Bogota MWO information, the Washington VAAC noted an ash emission reported moving W at 7 km altitude, that was not visible in satellite data.
2017 Apr 26    - - - - Ash Plume SGO reported that gas, steam, and ash plumes rose 1.2 km above the crater rim and drifted NW and SW.
2017 Apr 29    - - - - Ash Plume The Bogota MWO reported an ash emission moving NW at 6.1 km altitude. No ash was observed by the Washington VAAC in satellite imagery.
2017 May 12    - - - - Ash Plume SGO reported that gas, steam, and ash plumes rose 1.7 km above the crater rim and drifted NW and SW.
2017 May 13    - - - - Ash Plume According to the Washington VAAC the Bogota MWO reported an ash emission that was not visible in satellite imagery.
2017 May 29    - - - - Seismicity (volcanic) Five episodes of drumbeat seismicity (low-energy long-period events) were recorded between 1343 and 1930, likely signifying growing lava domes.
2017 May 29    - - - - Lava dome Five episodes of drumbeat seismicity (low-energy long-period events) were recorded between 1343 and 1930, likely signifying growing lava domes.
Episode 2 | Eruption Arenas crater
2017 Sep 21 - 2018 Jan 9 Evidence from Observations: Aviation

List of 7 Events for Episode 2 at Arenas crater

Start Date End Date Event Type Event Remarks
2017 Sep 21    - - - - Ash Plume The Bogota MWO reported an ash emission drifting NNW at 6.4 km altitude. It was not identified in satellite imagery under partly clear weather conditions by the Washington VAAC.
2017 Oct 7    - - - - Ash Plume The Bogota MWO reported an eruption with an ash plume that rose to 6.7 km altitude and drifted W. It was not identified by the Washington VAAC in satellite imagery due to weather clouds.
2017 Oct 7    - - - - VEI (Explosivity Index) VEI 2
2017 Oct 30    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
2017 Nov 8    - - - - Ash Plume The Bogota MWO reported an ash emission to 6.1 km altitude; a faint plume extending 15 km NE from the summit was observed in satellite imagery.
2017 Dec 18    - - - - Ash Plume The Washington VAAC issued an advisory for an ash plume to 6 km altitude that was moving W and dispersing. The plume was described as a "thin veil of volcanic ash and gasses" that was seen in visible satellite imagery, NOAA/CIMSS, and supported by webcam imagery.
2018 Jan 9    - - - - Thermal Anomaly A MODVOLC thermal alert was issued.
Episode 3 | Eruption Arenas crater
2018 Apr 21 - 2024 Oct 17 (continuing) Evidence from Observations: Satellite (visual)

List of 27 Events for Episode 3 at Arenas crater

Start Date End Date Event Type Event Remarks
2018 Apr 21    - - - - Ash Plume Based on GEOS-EAST and NWP Models, at 0930 UTC the Washington VAAC reported a discrete ash emission moving NW at 6.1 km altitude, observed in satellite imagery around 0800 UTC. By 1515 UTC ash had dissipated.
2018 Jul 22    - - - - Ash Plume SGC reported weak gas-and-steam and ash emissions confirmed by webcams, associated with a volcanic tremor.
2018 Aug 10 2018 Aug 11 Ash Plume Based on GOES-EAST, NWP models, Volcano webcam, and CIMSS VOLCAT information, at 0430 UTC on 11 August the Washington VAAC reported an ash emission at approximately 0245 UTC moving W at 6.7 km altitude. A distinct puff moving W of the summit and fanning slightly and thinning was observed. By 1030 UTC the ash had dissipated. The webcam showed no ash or gas.
2018 Aug 17    - - - - Ash Plume Based on GOES-EAST, NWP models, Bogoto MWO, and CIMSS VOLCAT information, at 1615 UTC the Washington VAAC reported an ash emission at approximately 1500 UTC. Meteoric clouds obscured summit observation. Ash was not detected in on satellite imagery. By 2200 UTC satellite information indicated no ash present.
2018 Aug 21
(in or after)
2018 Aug 28
(in or before)
Ash Plume During the week of 21 August, SGC reported that seismicity in the Arenas crater was associated with minor gas-and-steam and ash emissions, as confirmed by webcams.
2018 Sep 1    - - - - Ash Plume Based on GOES-EAST, NWP models, and CIMSS VOLCAT information, at 0030 UTC on 2 September the Washington VAAC reported a new ash emission moving W at 7.3 km altitude. A patch of ash was located 50 km WNW from the summit. By 0630 UTC ash had dissipated and no additional emissions were detected in satellite imagery.
2018 Sep 5    - - - - Ash Plume Based on GOES-EAST, NWP models, Bogoto MWO, and CIMSS VOLCAT information, at 0730 UTC the Washington VAAC reported an ash emission at 0710 UTC moving W at 7.0 km altitude. By 1315 UTC ash was not identifiable in satellite data.
2018 Sep 11
(in or after)
2018 Sep 18
(in or before)
Ashfall Ashfall was observed during the week of 11 September in Manizales (30 km NW) and Villamaría (27 km NW).
2018 Sep 15    - - - - Seismicity (tremor) A new volcanic tremor occurred and was accompanied by various ash emissions reaching 1.4 km above the crater and drifting NW as confirmed by PNNN, inhabitants within the vicinity of the volcano, and the Washington VAAC.
2018 Sep 15    - - - - Ash Plume A new volcanic tremor occurred and was accompanied by various ash emissions reaching 1.4 km above the crater and drifting NW as confirmed by PNNN, inhabitants within the vicinity of the volcano, and the Washington VAAC.
2018 Sep 16 2018 Sep 17 Ash Plume Based on GOES-EAST, NWP models, ABBA, and CIMSS VOLCAT information, at 0430 UTC the Washington VAAC reported an ash emission at approximately 0400 UTC moving NW at 6.7 km altitude. A new ash puff was seen in various modes of satellite imagery and alerted to by VOLCAT. The puff coincided with a bright hotspot. At 0915 UTC ongoing ash emissions were moving up to 90 km NW. At 1515 UTC ongoing ash emissions extended 65 km WNW. By 2045 UTC the ash had dissipated and no hotspot activity could be seen.
2018 Sep 19 2018 Sep 20 Ash Plume Based on GOES-EAST, NWP models, Bogoto MWO, CIMSS VOLCAT information, and the Volcano Webcam, at 0415 UTC the Washington VAAC reported a new ash emission moving NW at 6.7 km altitude. A small puff of ash was seen in satellite imagery. By 0900 UTC ash emissions had ended.
2018 Sep 20 2018 Sep 22 Ash Plume Based on GOES-EAST, NWP models, SGC, HYSPLIT, and CIMSS VOLCAT information, at 1600 UTC the Washington VAAC reported an ash emission observed moving NW at 6.4 km altitude. Continuous ash emission was seen in satellite data extending about 90 km NW. At 2145 UTC ongoing ash emissions extended 25 km NW. At 0345 UTC on 21 September continuous ash emission extended 45 km NW at 6.7 km altitude. At 0945 UTC continuous ash emissions extended 75 km NW. At 1515 UTC ongoing ash emissions extended about 110 km WNW. At 2100 UTC ongoing ash emissions extended 55 km WNW. Ot 0200 UTC on 22 September ash was obscured by weather clouds. At 0330 UTC occasional ash emissions extended 55 km NW. At 0645 UTC ash extended 35 km W. At 1500 UTC possible minor ash was streaming W. At 2115 UTC no ash was detected.
2018 Sep 22    - - - - Seismicity (tremor) SGC reported seismicity and ash emissions, rising to an altitude of 1.4 km above the crater.
2018 Sep 25
(in or after)
2018 Oct 8
(in or before)
Seismicity (tremor) Seismicity continuing into the weeks of 25 September and 2 October was accompanied by ash emissions.
2018 Sep 25 2018 Oct 8
(in or before)
Ash Plume Seismicity continuing into the weeks of 25 September and 2 October was accompanied by ash emissions.
2018 Oct 19    - - - - Ash Plume Ash emissions were reported by SGC.
2018 Oct 22    - - - - Ash Plume Ash emissions were reported by SGC.
2018 Oct 26 2018 Oct 27 Seismicity (volcanic) Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that seismicity increased, with signals concentrated in an area 4.6 km WSW of Arenas Crater at depths of 4-6 km.
2018 Oct 26    - - - - Ash Plume Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that plumes of water vapor, ash, and gas continued to rise from the volcano, and a plume rose as high as 1.5 km above the crater rim.
2018 Oct 31    - - - - Ash Plume Ash emissions were reported by SGC.
2018 Nov 6    - - - - Ash Plume Ash emissions were reported by SGC.
2018 Nov 6    - - - - Ash Plume Based on GOES-EAST, CIMSS VOLCAT and NWP Models at 2145 UTC the Washington VAAC reported a new ash emission moving E at 6.7 km altitude extending 35 km E. By 0330 UTC on 7 November the ash had dissipated.
2018 Nov 9    - - - - Ash Plume Ash emissions were reported by SGC.
2018 Nov 17    - - - - Ash Plume Ash emissions were reported by SGC.
2018 Dec 14    - - - - Ash Plume Ash emissions were reported by SGC.
2018 Dec 14    - - - - Ash Plume Based on GOES-EAST, Volcano webcam and NWP Model information, at 1445 UTC the Washington VAAC reported a possible ash emission moving NW at 6.1 km altitude. A faint plume that may have contained ash was seen in visible satellite imagery. By 2015 UTC ash was not identifiable in satellite imagery.

2012 Feb 22 - 2013 Jul 12 (?) Confirmed Eruption VEI: 3 (?)

Episode 1 | Eruption Arenas Crater
2012 Feb 22 - 2013 Jul 12 (?) Evidence from Observations: Reported

List of 67 Events for Episode 1 at Arenas Crater

Start Date End Date Event Type Event Remarks
2012 Feb 22    - - - - Explosion INGEOMINAS reported an explosion.
2012 Mar 5 2012 Mar 11 Seismicity (volcanic) INGEOMINAS reported a significant increase in seismicity.
2012 Mar 5 ± 5 days    - - - - Ashfall Fieldwork revealed ash deposits at the headwaters of Gualí River, SW of Arenas crater.
2012 Mar 8    - - - - Explosion A small explosion detected by the seismic network produced an ash emission that was observed with a camera installed in La Piranha (NW).
2012 Mar 8    - - - - Ash Plume A small explosion detected by the seismic network produced an ash emission that was observed with a camera installed in La Piranha (NW).
2012 Mar 8    - - - - Observation Scientists aboard an overflight observed a gas plume that rose 1.4 km above Arenas crater, originating from multiple emission sources and thermally anomalous areas within the crater. They noted ash deposits on the glacier, near the crater rim and on the E flank, likely from an explosion on 22 February.
2012 Mar 24 2012 Mar 31 Seismicity (volcanic) Seismicity increased significantly. Earthquakes indicating rock fracturing occurred W of Arenas crater, exhibiting a pattern observed prior to the eruptions in 1985 and 1989, although less energetic. Starting at 1054 on 29 March, and lasting for about 25 minutes, more than 135 earthquakes were detected S of Arenas crater at a depth of 4 km. At 0400 on 31 March earthquake signals indicating rock fracturing and fluid movement markedly increased.
2012 Apr 15    - - - - Seismicity (volcanic) Earthquake events at 1146 and 1149 were possibly associated with ash emissions which were not verified due to weather conditions.
2012 Apr 15    - - - - Ash Plume Earthquake events at 1146 and 1149 were possibly associated with ash emissions which were not verified due to weather conditions.
2012 Apr 18 2012 Apr 19 Seismicity (volcanic) Multiple seismic signals possibly indicated ash emissions, but they could not be verified due to weather conditions.
2012 Apr 18 2012 Apr 19 Ash Plume Multiple seismic signals possibly indicated ash emissions, but they could not be verified due to weather conditions.
2012 Apr 22    - - - - Ash Plume Based on satellite information, wind models, and the volcano web camera, the Washington VAAC issued an advisory for a possible volcanic ash plume drifting NW at 7.6 km altitude.
2012 Apr 30    - - - - Seismicity (volcanic) Seismic signals indicated that an ash plume was emitted at 1248 however cloud cover prevented observations.
2012 Apr 30    - - - - Ash Plume Seismic signals indicated that an ash plume was emitted at 1248 however cloud cover prevented observations.
2012 May 22    - - - - Seismicity (volcanic) A seismic signal possibly indicated an ash emission, though it was not confirmed due to poor weather conditions.
2012 May 22    - - - - Ash Plume A seismic signal possibly indicated an ash emission, though it was not confirmed due to poor weather conditions.
2012 May 29    - - - - Seismicity (volcanic) At 0307 seismic signals indicated ash emissions that were confirmed by officials and residents near the volcano as well as with a web camera.
2012 May 29    - - - - Ash Plume At 0307 seismic signals indicated ash emissions that were confirmed by officials and residents near the volcano as well as with a web camera. A gas-and-ash plume rose 1 km above the crater. Later that day ash emissions rose 600 m above the crater.
2012 May 29    - - - - Explosion Based on satellite information, wind models, seismic detection, the Air Force Weather Agency, and information from IG, the Washington VAAC reported an explosive eruption at 0800 UTC that produced an ash plume that rose to 13.7 km altitude (8.7 km above the summit) and drifted over 100 km NE.
2012 May 29    - - - - Ash Plume Based on satellite information, wind models, seismic detection, the Air Force Weather Agency, and information from IG, the Washington VAAC reported an explosive eruption at 0800 UTC that produced an ash plume that rose to 13.7 km altitude (8.7 km above the summit) and drifted over 100 km NE. Three hours later, a large area of remnant ash extended up to 275 km NE at 11 km altitude.
2012 May 29    - - - - Ashfall Ashfall was reported in Anserma (65 km NW), Aranzazu (45 km NNW), Chinchiná (30 km WNW), Dosquebradas (40 km W), Filadelfia, La Merced (60 km NNW), Manizales (30 km NW), Marmato (70 km NNW), Neira (37 km NW), Palestina (40 km WNW), Pereira (40 km WSW), Risaralda (78 km WNW), Salamina (60 km NNW), San José (56 km NW), Santagueda (40 km NW), Santa Rosa de Cabal (33 km W), Supia (72 km NNW), Villamaria (28 km NW), and Viterbo (65 km WNW). Ash also fell in all municipalities in the department of Risaralda (76 km WNW) and El Aguila (85 km W, N of Valle del Cauca).
2012 May 29    - - - - VEI (Explosivity Index) VEI 3
2012 Jun 1    - - - - Ash Plume Based on satellite data, wind models, radiosonde data and information from the Bogota MWO and IG, the Washington VAAC reported an ash emission, not identifiable in satellite data, that was reported at 4.9-6.1 km altitude. The observatory indicated it was moving SW.
2012 Jun 4    - - - - Ash Plume Observations during an overflight and through web cameras located in the vicinity of Arenas Crater revealed that gas-and-ash plumes rose at most 1 km above the crater and drifted W and NW.
2012 Jun 5    - - - - Seismicity (volcanic) Seismic signals indicated that ash emissions continued.
2012 Jun 5    - - - - Ash Plume Seismic signals indicated that ash emissions continued. Based on analysis of satellite imagery, the Washington VAAC reported that an ash plume drifted 40 km W. The VAAC also noted that the Bogota MWO reported ash emissions drifting NNW at an altitude of 9.1 km.
2012 Jun 6 2012 Jun 11 Ash Plume A satellite image acquired on 6 June showed an ash plume rising from the crater and drifting NW. Based on analysis of satellite imagery and information from INGEOMINAS, the Washington VAAC reported that gas plumes possibly containing some ash drifted 75-110 km W, WNW, and N during 7 and 9-10 June. Ash plumes drifted almost 30 km SE on 8 June. INGEOMINAS reported that on 11 June seismic signals indicated continuing ash emissions.
2012 Jun 6    - - - - Ashfall A satellite image showed ash deposits on the N, NW, W and SW flanks.
2012 Jun 15 2012 Jun 18 Ash Plume Seismic signals on 15 and 18 June indicated continuing ash emissions. Based on analysis of satellite imagery and web camera views, the Washington VAAC reported that on 17 June a 5.5-km-wide gas plume, possibly containing ash, drifted more than 90 km NW. The VAAC noted on 18 June that INGEOMINAS reported a gas-and-ash plume drifting N and NW at an altitude of 6.1 km. The plume was later detected in satellite imagery drifting more than 90 km NW.
2012 Jun 22 2012 Jun 29 Ash Plume Reports stated that seismic signals had indicated continuing gas and ash emissions.
2012 Jun 30    - - - - Explosion An explosion produced an ash plume that rose 8 km above the crater and drifted SW.
2012 Jun 30    - - - - Ash Plume INGEOMINAS reported an explosion late in the day produced an ash plume that rose 8 km above the crater and drifted SW. The Washington VAAC noted an Observatory report that indicated an eruption beginning at 2240 UTC on 30 June that produced a plume that rose to 7.6 km altitude, and included reports of ashfall. No ash was detected in satellite imagery due to weather clouds.
2012 Jun 30    - - - - Ashfall Ashfall was reported in areas near the volcano including Manizales (30 km NW) and Villamaría (28 km NW).
2012 Jun 30    - - - - Evacuations According to news reports, communities around the volcano evacuated, and airports in Manizales, Pereira, and Armenia closed.
2012 Jun 30    - - - - VEI (Explosivity Index) VEI 3 (?)
2012 Jul 2    - - - - Ash Plume Based on satellite data, wind models, seismic detection and information from INGEOMINAS, the Washington VAAC reported a 7.5-km-wide plume of gases and ash visible in satellite imagery extending 75 km W from the summit at 6.1 km altitude.
2012 Jul 3 2012 Jul 9 Ash Plume INGEOMINAS noted that seismic signals indicated continuing gas and ash emissions on 3 July. During 5-9 July seismic signals at Nevado del Ruiz indicated continuing gas and ash emissions. On 6 and 8 July a gas-and-ash plume rose 400-500 m above the crater and drifted SW, NW, and W. The Washington Volcanic Ash Advisory Center (VAAC) reported that a gas-and-ash plume was observed in satellite imagery drifting 65 km on 8 July. On 9 July INGEOMINAS noted that a gas-and-ash plume, observed with a web camera, rose around 400 m above the crater.
2012 Jul 11 2012 Jul 17 Ash Plume Data indicated gas and ash emissions.
2012 Jul 11    - - - - Ashfall Ashfall was reported in Pereira (40 km WSW).
2012 Jul 22 2012 Jul 24 Ash Plume Low levels of tremor were detected, possibly associated with continuing gas and ash emissions.
2012 Jul 31    - - - - Ash Plume Web cameras showed gas-and-ash plumes rising 300 m above the crater.
2012 Aug 3 2012 Aug 6 Ash Plume Low levels of tremor were detected, possibly associated with continuing gas and ash emissions.
2012 Aug 3 2012 Aug 6 Ashfall Ashfall and a strong sulfur odor were reported in Manizales (30 km NW) and in the municipality of Chinchiná (30 km WNW).
2012 Aug 10 2012 Aug 13 Ash Plume Low levels of tremor were detected, possibly associated with continuing gas and ash emissions. A gas-and-ash plume observed with a web camera rose 1 km above the crater and drifted W on 12 August.
2012 Aug 12 2012 Aug 13 Seismicity (volcanic) A total of 140 low-magnitude earthquakes (M < 1.8) were detected in a seismic swarm that began at 0956 and ended at 1800. The earthquakes were located about 4 km WSW of Arenas Crater at depths of less than 5 km. On 13 August a seismic swarm was characterized by events less than M 1, and located NE of Arenas Crater at depths between 3 and 5 km.
2012 Aug 12    - - - - Ashfall Ashfall was reported in Brisas (50 km SW).
2012 Aug 13    - - - - Ashfall A thin layer of ash was deposited at the observatory in Manizales.
2012 Aug 15 2012 Aug 28 Ash Plume Variations in volcanic tremor amplitude were detected, possibly associated with continuing gas and ash emissions. Web cameras showed gas-and-ash plumes rising 400 m and drifting W and NW during 15-16 August. A gas plume rose 400 m and drifted NW on 19 August.
2012 Aug 30 2012 Aug 31 Ash Plume Variations in volcanic tremor amplitude were detected, possibly associated with continuing gas and ash emissions.
2012 Sep 6    - - - - Ash Plume A small explosion with a small ash emission was reported in SGC's weekly report.
2012 Oct 10    - - - - Ash Plume The Washington Volcanic Ash Advisory Center (VAAC) reported ash plumes visible in satellite images at 7.3 km altitude, drifting 35 km NW.
2012 Nov 15    - - - - Ash Plume The Washington VAAC issued a notice about a possible eruption. Cloud cover prevented observations of a possible ash plume but elevated seismicity was detected.
2012 Dec 10    - - - - Ash Plume Early morning, gas and ash emissions were reported during a tremor event by SGC in their Weekly Report.
2013 Jan 9    - - - - Ash Plume Ash and gas emission and ashfall after a tremor event was reported in the SGC Weekly Report.
2013 Jan 9    - - - - Ashfall Ashfall reported in the Valle de las Tumbas, W of the summit crater.
2013 Jan 16    - - - - Ash Plume Based on analysis of satellite imagery, the Washington VAAC reported a diffuse plume possibly contained ash and drifted almost 55 km NE.
2013 Feb 11    - - - - Ash Plume A gas and ash plume was seen in webcam images and in visual observation from Observatorio Manizales, 1,600 m above the crater.
2013 Mar 7 2013 Mar 17 Ash Plume Gas and ash emissions were reported by officials from the Parque Nacional Natural los Nevados (PNNN).
2013 Apr 13 2013 Apr 16 Seismicity (volcanic) INGEOMINAS reported that seismicity associated with fluid movement beneath Nevado del Ruiz was detected on 13-14 April along with volcano-tectonic earthquakes. The earthquakes were located NW of Arenas Crater at depths between 5 and 9 km; the largest was a M 2.6, felt by officials of Los Nevados National Park in the area of Brisas (50 km SW). On 15 April a M 3 volcano-tectonic earthquake was located NW of Arenas Crater at a depth of 6.6 km. Later that day a M 2.5 volcano-tectonic earthquake was located again NW of Arenas Crater at a depth of 5.78 km. On 16 April at 0714 a M 3.2 earthquake was located in the same area at a depth of 6.22 km. Earthquakes continued to be felt by officials in the National Park.
2013 Apr 14    - - - - Ash Plume During the early morning of 14 April webcams recorded a gas-and-ash plume that rose 630 m and drifted NW.
2013 Apr 15 2013 Apr 21 Ashfall Ashfall confirmed near Villahermosa (Tolima), 30 km NE.
2013 May 22 2013 May 27 Ash Plume Ash and gas emissions were confirmed by seismic signals as well as the webcams on 22 and 27 May.
2013 Jun 1 2013 Jun 30 Ash Plume Low-energy tremors were associated with gas and ash emissions and pulses of low energy.
2013 Jun 16    - - - - Ash Plume A possible ash plume was detected at ~7.6 km altitude.
2013 Jul 11 2013 Jul 12 Seismicity (tremor) Continuous volcanic tremor associated with emissions was detected; ashfall was reported in Los Nevados Natural Park and in some parts of Manizales (30 km NW).
2013 Jul 11    - - - - Ash Plume A small ash plume was confirmed by OVSM webcams and officials at PNNN.
2013 Jul 11 2013 Jul 12 Ashfall Continuous volcanic tremor associated with emissions was detected; ashfall was reported in Los Nevados Natural Park and in some parts of Manizales (30 km NW).

[ 1994 Apr 23 - 1994 Apr 23 ] Uncertain Eruption

Episode 1 | Eruption
1994 Apr 23 - 1994 Apr 23 Evidence from Unknown

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Seismicity (tremor)
   - - - -    - - - - Phreatic activity Uncertain
   - - - -    - - - - Earthquakes (undefined) Before.

1985 Sep 11 - 1991 Jul 13 Confirmed Eruption VEI: 3

Episode 1 | Eruption Arenas Crater
1985 Sep 11 - 1991 Jul 13 Evidence from Observations: Reported

List of 20 Events for Episode 1 at Arenas Crater

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Seismicity (tremor) Before eruption.
   - - - -    - - - - Seismicity (tremor)
   - - - -    - - - - Explosion
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Eruption cloud
   - - - -    - - - - Pyroclastic flow
   - - - -    - - - - Ash
   - - - -    - - - - Earthquakes (undefined) After.
   - - - -    - - - - Deformation (inflation)
   - - - -    - - - - Deformation (deflation)
   - - - -    - - - - Lahar or Mudflow
   - - - -    - - - - Fauna Kill Terrestrial.
   - - - -    - - - - Property Damage
   - - - -    - - - - Evacuations
1985 Sep 11    - - - - VEI (Explosivity Index)
1985 Nov 13    - - - - Fatalities
1985 Nov 13    - - - - VEI (Explosivity Index)
1986 Jan 4    - - - - Evacuations
1988 Mar 22    - - - - Evacuations
1989 Sep 1    - - - - Evacuations

1984 Dec 22 - 1985 Mar 19 (?) Confirmed Eruption VEI: 1

Episode 1 | Eruption Arenas Crater
1984 Dec 22 - 1985 Mar 19 (?) Evidence from Observations: Reported

List of 5 Events for Episode 1 at Arenas Crater

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Seismicity (tremor)
   - - - -    - - - - Phreatic activity weak or small
   - - - -    - - - - Ash
   - - - -    - - - - Crater Summit.
1984 Dec 22    - - - - VEI (Explosivity Index)

1916 Confirmed Eruption VEI: 2

Episode 1 | Eruption
1916 - Unknown Evidence from Observations: Reported

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Ash
1916    - - - - VEI (Explosivity Index)

1845 Feb 19 Confirmed Eruption VEI: 3

Episode 1 | Eruption Arenas and La Olleta(?) craters, R1 tephra
1845 Feb 19 - Unknown Evidence from Observations: Reported

List of 10 Events for Episode 1 at Arenas and La Olleta(?) craters, R1 tephra

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Pyroclastic flow
   - - - -    - - - - Lava flow Uncertain
   - - - -    - - - - Avalanche
   - - - -    - - - - Earthquakes (undefined)
   - - - -    - - - - Lahar or Mudflow
   - - - -    - - - - Property Damage
1845 Feb 19    - - - - Fatalities
1845 Feb 19    - - - - VEI (Explosivity Index)

[ 1833 ] Uncertain Eruption

Episode 1 | Eruption
1833 - Unknown Evidence from Unknown

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity Uncertain
   - - - -    - - - - Fumarolic or Solfataric Uncertain
1833    - - - - VEI (Explosivity Index)

1831 Confirmed Eruption VEI: 2

Episode 1 | Eruption
1831 - Unknown Evidence from Observations: Reported

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity Uncertain
   - - - -    - - - - Ash
1831    - - - - VEI (Explosivity Index)

1829 Jun 18 Confirmed Eruption VEI: 2

Episode 1 | Eruption
1829 Jun 18 - Unknown Evidence from Observations: Reported

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity Uncertain
   - - - -    - - - - Ash
1829 Jun 18    - - - - VEI (Explosivity Index)

1828 Jun Confirmed Eruption VEI: 2

Episode 1 | Eruption
1828 Jun - Unknown Evidence from Observations: Reported

List of 2 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity
1828 Jun    - - - - VEI (Explosivity Index)

[ 1826 ] Uncertain Eruption

Episode 1 | Eruption
1826 - Unknown Evidence from Unknown

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity Uncertain
   - - - -    - - - - Volcanic "smoke"
1826    - - - - VEI (Explosivity Index)

1805 Mar 14 Confirmed Eruption VEI: 2

Episode 1 | Eruption
1805 Mar 14 - Unknown Evidence from Observations: Reported

List of 4 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Phreatic activity Uncertain
   - - - -    - - - - Ash
1805 Mar 14    - - - - VEI (Explosivity Index)

1623 Confirmed Eruption VEI: 1 (?)

Episode 1 | Eruption Near Arenas Crater
1623 - Unknown Evidence from Observations: Reported

List of 4 Events for Episode 1 at Near Arenas Crater

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain
   - - - -    - - - - Phreatic activity Uncertain
   - - - -    - - - - Incandescence Event was "Glow"
1623    - - - - VEI (Explosivity Index)

1595 Mar 9 (in or before) Confirmed Eruption VEI: 4

Episode 1 | Eruption Arenas Crater, R2 tephra
1595 Mar 9 (in or before) - Unknown Evidence from Observations: Reported

List of 11 Events for Episode 1 at Arenas Crater, R2 tephra

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Pyroclastic flow
   - - - -    - - - - Avalanche
   - - - -    - - - - Ash
   - - - -    - - - - Lapilli
   - - - -    - - - - Lahar or Mudflow
   - - - -    - - - - Edifice Destroyed Collapse/avalanche
   - - - -    - - - - Property Damage
1595 Mar 9
(in or before)
   - - - - VEI (Explosivity Index)
1595 Mar 12    - - - - Fatalities
1595 Mar 12    - - - - VEI (Explosivity Index)

1570 Confirmed Eruption  

Episode 1 | Eruption Arenas Crater?
1570 - Unknown Evidence from Observations: Reported

List of 2 Events for Episode 1 at Arenas Crater?

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Flames

[ 1541 ] Uncertain Eruption

Episode 1 | Eruption
1541 - Unknown Evidence from Unknown

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity Uncertain

1350 (?) Confirmed Eruption VEI: 4

Episode 1 | Eruption Arenas Crater, R4 tephra
1350 (?) - Unknown Evidence from Isotopic: 14C (uncalibrated)

List of 4 Events for Episode 1 at Arenas Crater, R4 tephra

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Pumice
   - - - -    - - - - Lahar or Mudflow
1350
(?)
   - - - - VEI (Explosivity Index)

0675 ± 50 years Confirmed Eruption VEI: 3

Episode 1 | Eruption Arenas Crater, R5 tephra
0675 ± 50 years - Unknown Evidence from Isotopic: 14C (uncalibrated)

List of 5 Events for Episode 1 at Arenas Crater, R5 tephra

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Pyroclastic flow
   - - - -    - - - - Pumice
   - - - -    - - - - Lahar or Mudflow
0675 ± 50 years    - - - - VEI (Explosivity Index)

0350 ± 300 years Confirmed Eruption VEI: 3

Episode 1 | Eruption West flank, La Olleta, R-6 tephra
0350 ± 300 years - Unknown Evidence from Isotopic: 14C (uncalibrated)

List of 3 Events for Episode 1 at West flank, La Olleta, R-6 tephra

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Tephra
0350 ± 300 years    - - - - VEI (Explosivity Index)

0200 BCE ± 100 years Confirmed Eruption VEI: 4

Episode 1 | Eruption Arenas Crater, R7 tephra
0200 BCE ± 100 years - Unknown Evidence from Isotopic: 14C (uncalibrated)

List of 3 Events for Episode 1 at Arenas Crater, R7 tephra

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Pumice
0200 BCE ± 100 years    - - - - VEI (Explosivity Index)

0850 BCE (?) Confirmed Eruption VEI: 4

Episode 1 | Eruption Arenas Crater, R8 tephra
0850 BCE (?) - Unknown Evidence from Correlation: Tephrochronology

List of 6 Events for Episode 1 at Arenas Crater, R8 tephra

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Pyroclastic flow
   - - - -    - - - - Lapilli
   - - - -    - - - - Pumice
   - - - -    - - - - Lahar or Mudflow
0850 BCE
(?)
   - - - - VEI (Explosivity Index)

1245 BCE ± 150 years Confirmed Eruption  

Episode 1 | Eruption ENE flank ? (Alto la Piramide ?)
1245 BCE ± 150 years - Unknown Evidence from Isotopic: 14C (uncalibrated)

List of 9 Events for Episode 1 at ENE flank ? (Alto la Piramide ?)

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Pyroclastic flow
   - - - -    - - - - Lava dome Uncertain
   - - - -    - - - - Avalanche
   - - - -    - - - - Ash
   - - - -    - - - - Pumice
   - - - -    - - - - Lahar or Mudflow
   - - - -    - - - - Edifice Destroyed Collapse/avalanche

6660 BCE (in or before) Confirmed Eruption  

Episode 1 | Eruption Arenas Crater, R9 tephra
6660 BCE (in or before) - Unknown Evidence from Correlation: Tephrochronology

List of 4 Events for Episode 1 at Arenas Crater, R9 tephra

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Pyroclastic flow
   - - - -    - - - - Tephra
   - - - -    - - - - Lahar or Mudflow
Deformation History

There is no Deformation History data available for Nevado del Ruiz.

Emission History

There is data available for 3 emission periods. Expand each entry for additional details.


Emissions during 1989 Sep 01 - 1989 Sep 01 [12 kt SO2 at 15 km altitude]

Start Date: 1989 Sep 01 Stop Date: 1989 Sep 01 Method: Satellite (Nimbus-7 TOMS)
SO2 Altitude Min: 15 km SO2 Altitude Max: 15 km Total SO2 Mass: 12 kt

Data Details

Date Start Date End Assumed SO2 Altitude SO2 Algorithm SO2 Mass
19890901 15.3 12.000

Emissions during 1985 Sep 12 - 1985 Sep 12 [90 kt SO2 at 15 km altitude]

Start Date: 1985 Sep 12 Stop Date: 1985 Sep 12 Method: Satellite (Nimbus-7 TOMS)
SO2 Altitude Min: 15 km SO2 Altitude Max: 15 km Total SO2 Mass: 90 kt

Data Details

Date Start Date End Assumed SO2 Altitude SO2 Algorithm SO2 Mass
19850912 15.0 90.000

Emissions during 1985 Nov 14 - 1985 Nov 14 [660 kt SO2 at 25 km altitude]

Start Date: 1985 Nov 14 Stop Date: 1985 Nov 14 Method: Satellite (Nimbus-7 TOMS)
SO2 Altitude Min: 25 km SO2 Altitude Max: 25 km Total SO2 Mass: 660 kt

Data Details

Date Start Date End Assumed SO2 Altitude SO2 Algorithm SO2 Mass
19851114 25.0 660.000
Photo Gallery

The catastrophic 1985 eruption of Nevado del Ruiz began with moderate phreatic explosions on September 11. On November 13 a relatively moderate explosive eruption occurred, producing pyroclastic flows and surges that melted part of the summit icecap. These caused major lahars that devastated Amero and other towns on the flanks of the volcano, killing more than 23,000 people. Intermittent minor ash emissions, such as this one on November 28, and occasional stronger phreatomagmatic eruptions continued until July 1991.

Copyrighted photo by Katia and Maurice Krafft, 1985.
The 1985 eruption of Colombia's Nevado del Ruiz volcano produced the deadliest lahars (volcanic mudflows) in recorded history. A relatively moderate explosive eruption melted parts of the summit icecap and sent lahars down four major drainages. The town of Armero, shown here, was destroyed by a lahar that had traveled 74 km east of the summit and exited a narrow canyon above the town in a 40-m-high wave. Three-quarters of the 28,000 inhabitants of Armero were killed because officials and residents were not prepared for the danger the volcano posed.

Copyrighted photo by Katia and Maurice Krafft, 1985.
Two weeks after the 13 November 1985 eruption, a plume rises from Las Arenas, the summit crater of Nevado del Ruiz. This view from the NNW shows pyroclastic surge and pyroclastic flow deposits mantling the summit icecap. Grooves descending the upper glacier surface were scoured by pyroclastic surges, which reached 5.5 km NW and NE of the summit. Melting of the summit icecap during the eruption led to devastating lahars that traveled as far as 100 km from the volcano and caused 24,000 fatalities.

Photo by Norm Banks, 1985 (U.S. Geological Survey).
A record of the 13 November 1985 eruption of Nevado de Ruiz was preserved in ice-rich levees of pyroclastic flows. This photo, taken a month later, shows parallel-bedded pyroclastic-surge deposits, composed of snow grains and tephra, which were deposited over a pre-existing ice at the bottom of the photo. The surge layers are overlain at the top by coarser-grained pyroclastic-flow deposits. The clast of glacial ice (located left of the upper part of the ice axe) was scoured and incorporated into the pyroclastic flow.

Photo by Tom Pierson, 1985 (U.S. Geological Survey).
On 13 November 1985 lahars traveled down the upper Guali River drainage on the N flank of Nevado del Ruiz, seen here descending diagonally from right of center to the lower left. Farmhouses are visible on the opposite side of the channel for scale. The lahars traveled down the Río Guali at velocities up to 17 meters/second to over 100 km from the volcano.

Photo by Tom Pierson, 1985 (U.S. Geological Survey).
A cluster of rounded boulders was deposited on a river terrace by a lahar in the Río Chinchina valley, 59 km WNW of the summit of Colombia's Nevado del Ruiz volcano on 13 November 1985. The boulders were carried within the lahar and deposited against the tree that served as an obstruction to flow. Note the mudline on the tree that marks the upper flow surface of the lahar.

Photo by Tom Pierson, 1985 (U.S. Geological Survey).
A plume rises from the summit crater of Nevado del Ruiz volcano on 10 December 1985. Pyroclastic surge and ashfall deposits from the 13 November eruption coat the glaciers. Glaciers on the upper NE-flank headwall of the Azufrado valley (foreground) were scoured by pyroclastic surges.

Photo by Tom Pierson, 1985 (U.S. Geological Survey).
Nevado del Ruiz is a broad glacier-covered volcano that covers more than 200 km2. The modern cone consists of a cluster of lava domes constructed within the summit caldera of an older edifice. The ash-mantled summit is seen here from the ESE on 18 December 1985, a little more than a month after the catastrophic eruption of 13 November. The devastating 1985 lahars swept down four major river drainages that day and caused around 24,000 fatalities.

Photo by Norm Banks, 1985 (U.S. Geological Survey).
The glacier on Nevado del Ruiz is seen here above the Azufrado valley on the NE flank. Debris avalanche deposits from an eruption roughly 3,100 years ago, and from the 1595 eruption, appear in the foreground. The major eruption about 3,100 years ago produced a large ashfall deposit, the debris avalanche, and associated lahars and pyroclastic surges. The 1595 eruption, the largest from Ruiz in historical time, was similar. Lahars in 1595 caused over 600 fatalities.

Photo by Jean-Claude Thouret (Université Grenoble).
GVP Map Holdings

Maps are not currently available due to technical issues.

Smithsonian Sample Collections Database

The following 162 samples associated with this volcano can be found in the Smithsonian's NMNH Department of Mineral Sciences collections, and may be availble for research (contact the Rock and Ore Collections Manager). Catalog number links will open a window with more information.

Catalog Number Sample Description Lava Source Collection Date
NMNH 116158 Pumice -- --
NMNH 116159 Pumice -- --
NMNH 116160 Pumice -- --
NMNH 116161 Pumice -- --
NMNH 116162 Pumice -- --
NMNH 116163 Pumice -- --
NMNH 116164 Pumice -- --
NMNH 116165 Pumice -- --
NMNH 116166 Pumice -- --
NMNH 116167 Pumice -- --
NMNH 116168 Pumice -- --
NMNH 116169 Pumice -- --
NMNH 116170 Pumice -- --
NMNH 116175 Pumice -- --
NMNH 116176 Pumice -- --
NMNH 116185-1 Welded Tuff -- --
NMNH 116185-10 Pumice -- --
NMNH 116185-100 Lava -- --
NMNH 116185-101 Lava -- --
NMNH 116185-102 Lava -- --
NMNH 116185-103 Lava -- --
NMNH 116185-104 Lava -- --
NMNH 116185-105 Pumice -- --
NMNH 116185-106 Pumice -- --
NMNH 116185-107 Pumice -- --
NMNH 116185-108 Tephra -- --
NMNH 116185-109 Pumice -- --
NMNH 116185-11 Volcanic Ash -- --
NMNH 116185-110 Pumice -- --
NMNH 116185-111 Lava -- --
NMNH 116185-112 Pumice -- --
NMNH 116185-113 Pumice -- --
NMNH 116185-114 Tephra -- --
NMNH 116185-115 Pumice -- --
NMNH 116185-116 Pumice -- --
NMNH 116185-117 Pumice -- --
NMNH 116185-118 Pumice -- --
NMNH 116185-119 Pumice -- --
NMNH 116185-12 Tephra -- --
NMNH 116185-120 Sand -- --
NMNH 116185-121 Clay -- --
NMNH 116185-122 Soil -- --
NMNH 116185-123 Soil -- --
NMNH 116185-124 Soil -- --
NMNH 116185-125 Pumice -- --
NMNH 116185-126 Soil -- --
NMNH 116185-127 Soil -- --
NMNH 116185-128 Sand -- --
NMNH 116185-129 Mud -- --
NMNH 116185-13 Tephra -- --
NMNH 116185-130 Tephra -- --
NMNH 116185-131 Sand -- --
NMNH 116185-132 Sand -- --
NMNH 116185-133 Sand -- --
NMNH 116185-134 Mud -- --
NMNH 116185-135 Pumice -- --
NMNH 116185-136 Lava -- --
NMNH 116185-137 Lava -- --
NMNH 116185-138 Pumice -- --
NMNH 116185-139 Pumice -- --
NMNH 116185-14 Tephra -- --
NMNH 116185-140 Pumice -- --
NMNH 116185-141 Pumice -- --
NMNH 116185-15 Tephra -- --
NMNH 116185-16 Tephra -- --
NMNH 116185-17 Tephra -- --
NMNH 116185-18 Mud -- --
NMNH 116185-19 Mud -- --
NMNH 116185-2 Welded Tuff -- --
NMNH 116185-20 Volcanic Ash -- --
NMNH 116185-21 Tephra -- --
NMNH 116185-22 Tephra -- --
NMNH 116185-23 Sediment -- --
NMNH 116185-24 Pumice -- --
NMNH 116185-25 Pumice -- --
NMNH 116185-26 Pumice -- --
NMNH 116185-27 Pumice -- --
NMNH 116185-28 Scoria -- --
NMNH 116185-29 Pumice -- --
NMNH 116185-3 Welded Tuff -- --
NMNH 116185-30 Pumice -- --
NMNH 116185-31 Pumice -- --
NMNH 116185-32 Pumice -- --
NMNH 116185-33 Pumice -- --
NMNH 116185-34 Pumice -- --
NMNH 116185-35 Pumice -- --
NMNH 116185-36 Pumice -- --
NMNH 116185-37 Pumice -- --
NMNH 116185-38 Pumice -- --
NMNH 116185-39 Soil -- --
NMNH 116185-4 Welded Tuff -- --
NMNH 116185-40 Pumice -- --
NMNH 116185-41 Pumice -- --
NMNH 116185-42 Pumice -- --
NMNH 116185-43 Volcanic Ash -- --
NMNH 116185-44 Volcanic Ash -- --
NMNH 116185-45 Volcanic Ash -- --
NMNH 116185-46 Sand -- --
NMNH 116185-47 Pumice -- --
NMNH 116185-48 Soil -- --
NMNH 116185-49 Pumice -- --
NMNH 116185-5 Welded Tuff -- --
NMNH 116185-50 Volcanic Ash -- --
NMNH 116185-51 Soil -- --
NMNH 116185-52 Clay -- --
NMNH 116185-53 Sand -- --
NMNH 116185-54 Pumice -- --
NMNH 116185-55 Pumice -- --
NMNH 116185-56 Pumice -- --
NMNH 116185-57 Soil -- --
NMNH 116185-58 Pumice -- --
NMNH 116185-59 Breccia -- --
NMNH 116185-6 Welded Tuff -- --
NMNH 116185-60 Pumice -- --
NMNH 116185-61 Pumice -- --
NMNH 116185-62 Pumice -- --
NMNH 116185-63 Pumice -- --
NMNH 116185-64 Pumice -- --
NMNH 116185-65 Pumice -- --
NMNH 116185-66 Pumice -- --
NMNH 116185-67 Pumice -- --
NMNH 116185-68 Pumice -- --
NMNH 116185-69 Pumice -- --
NMNH 116185-7 Welded Tuff -- --
NMNH 116185-70 Pumice -- --
NMNH 116185-71 Pumice -- --
NMNH 116185-72 Pumice -- --
NMNH 116185-73 Pumice -- --
NMNH 116185-74 Pumice -- --
NMNH 116185-75 Volcanic Ash -- --
NMNH 116185-76 Lava -- --
NMNH 116185-77 Lava -- --
NMNH 116185-78 Andesite -- --
NMNH 116185-79 Lava -- --
NMNH 116185-8 Welded Tuff -- --
NMNH 116185-80 Lava -- --
NMNH 116185-81 Lava -- --
NMNH 116185-82 Lava -- --
NMNH 116185-83 Lava -- --
NMNH 116185-84 Lava -- --
NMNH 116185-85 Lava -- --
NMNH 116185-86 Lava -- --
NMNH 116185-87 Lava -- --
NMNH 116185-88 Lava -- --
NMNH 116185-89 Lava -- --
NMNH 116185-9 Welded Tuff -- --
NMNH 116185-90 Soil -- --
NMNH 116185-91 Soil -- --
NMNH 116185-92 Soil -- --
NMNH 116185-93 Soil -- --
NMNH 116185-94 Soil -- --
NMNH 116185-95 Soil -- --
NMNH 116185-96 Soil -- --
NMNH 116185-97 Soil -- --
NMNH 116185-98 Volcanic Ash -- --
NMNH 116185-99 Tephra -- --
NMNH 116185-9A Welded Tuff -- --
NMNH 116185-9B Welded Tuff -- --
NMNH 116430-1 Airfall Tephra -- --
NMNH 116430-2 Airfall Tephra -- --
NMNH 116430-3 Airfall Tephra -- --
NMNH 116468 Andesite Pumice -- --
External Sites