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Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information is preliminary at time of publication and subject to change.

Recently Published Bulletin Reports

Erta Ale (Ethiopia) Continued lava flow outbreaks and thermal anomalies during November 2019 to early April 2020

Rincon de la Vieja (Costa Rica) Weak phreatic explosions during August 2019-March 2020; ash and lahars reported in late January

Manam (Papua New Guinea) Minor explosive activity, continued thermal activity, and SO2 emissions, October 2019-March 2020.

Stromboli (Italy) Strombolian activity continues at both summit crater areas, September-December 2019

Semeru (Indonesia) Ash plumes and thermal anomalies continue during September 2019-February 2020

Popocatepetl (Mexico) Dome growth and destruction continues along with ash emissions and ejecta, September 2019-February 2020

Santa Maria (Guatemala) Daily explosions with ash plumes and block avalanches continue, September 2019-February 2020

Villarrica (Chile) Brief increase in explosions, mid-September 2019; continued thermal activity through February 2020

Semisopochnoi (United States) Intermittent small explosions detected in December 2019 through mid-March 2020

Ubinas (Peru) Explosions produced ash plumes in September 2019; several lahars generated in January and February 2020

Yasur (Vanuatu) Strombolian activity continues during June 2019 through February 2020

Cleveland (United States) Intermittent thermal anomalies and lava dome subsidence, February 2019-January 2020



Erta Ale (Ethiopia) — May 2020 Citation iconCite this Report

Erta Ale

Ethiopia

13.6°N, 40.67°E; summit elev. 613 m

All times are local (unless otherwise noted)


Continued lava flow outbreaks and thermal anomalies during November 2019 to early April 2020

Erta Ale is a shield volcano located in Ethiopia and contains multiple active pit craters in the summit and southeastern caldera. Volcanism has been characterized by lava flows and large lava flow fields since 2017. Surficial lava flow activity continued within the southeastern caldera during November 2019 until early April 2020; source information was primarily from various satellite data.

The number of days that thermal anomalies were detected using MODIS data in MODVOLC and NASA VIIRS satellite data was notably higher in November and December 2019 (figure 96); the number of thermal anomalies in the Sentinel-2 thermal imagery was substantially lower due to the presence of cloud cover. Across all satellite data, thermal anomalies were identified for 29 days in November, followed by 30 days in December. After December 2019, the number of days thermal anomalies were detected decreased; hotspots were detected for 17 days in January 2020 and 20 days in February. By March, these thermal anomalies became rare until activity ceased. Thermal anomalies were identified during 1-4 March, with weak anomalies seen again during 26 March-8 April 2020.

Figure (see Caption) Figure 96. Graph comparing the number of thermal alerts using calendar dates using MODVOLC, NASA VIIRS, and Sentinel-2 satellite data for Erta Ale during November 2019-March 2020. Data courtesy of HIGP - MODVOLC Thermal Alerts System, NASA Worldview using the “Fire and Thermal Anomalies” layer, and Sentinel Hub Playground.

MIROVA (Middle Infrared Observation of Volcanic Activity) analysis of MODIS satellite data showed frequent strong thermal anomalies from 18 April through December 2019 (figure 97). Between early August 2019 and March 2020, these thermal signatures were detected at distances less than 5 km from the summit. In late December the thermal intensity dropped slightly before again increasing, while at the same time moving slightly closer to the summit. Thermal anomalies then became more intermittent and steadily decreased in power over the next two months.

Figure (see Caption) Figure 97. Two time-series plots of thermal anomalies from Erta Ale from 18 April 2019 through 18 April 2020 as recorded by the MIROVA system. The top plot (A) shows that the thermal anomalies were consistently strong (measured in log radiative power) and occurred frequently until early January 2020 when both the power and frequency visibly declined. The lower plot (B) shows these anomalies as a function of distance from the summit, including a sudden decrease in distance (measured in kilometers) in early August 2019, reflecting a change in the location of the lava flow outbreak. A smaller distance change can be identified at the end of December 2019. Courtesy of MIROVA.

Unlike the obvious distal breakouts to the NE seen previously (BGVN 44:04 and 44:11), infrared satellite imagery during November-December 2019 showed only a small area with a thermal anomaly near the NE edge of the Southeast Caldera (figure 98). A thermal alert was seen at that location using the MODVOLC system on 28 December, but the next day it had been replaced by an anomaly about 1.5 km WSW near the N edge of the Southeast Caldera where the recent flank eruption episode had been centered between January 2017 and January 2018 (BGVN 43:04). The thermal anomaly that was detected in the summit caldera was no longer visible after 9 January 2020, based on Sentinel-2 imagery. The exact location of lava flows shifted within the same general area during January and February 2020 and was last detected by Sentinel-2 on 4 March. After about two weeks without detectable thermal activity, weak unlocated anomalies were seen in VIIRS data on 26 March and in MODIS data on the MIROVA system four times between 26 March and 8 April. No further anomalies were noted through the rest of April 2020.

Figure (see Caption) Figure 98. Sentinel-2 thermal satellite imagery of Erta Ale volcanism between November 2019 and March 2020 showing small lava flow outbreaks (bright yellow-orange) just NE of the southeastern calderas. A thermal anomaly can be seen in the summit crater on 15 November and very faintly on 20 December 2019. Imagery on 19 January 2020 showed a small thermal anomaly near the N edge of the Southeast Caldera where the recent flank eruption episode had been centered between January 2017 and January 2018. The last weak thermal hotspot was detected on 4 March (bottom right). Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

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/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).


Rincon de la Vieja (Costa Rica) — April 2020 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

10.83°N, 85.324°W; summit elev. 1916 m

All times are local (unless otherwise noted)


Weak phreatic explosions during August 2019-March 2020; ash and lahars reported in late January

Rincón de la Vieja is a remote volcanic complex in Costa Rica containing an acid lake that has regularly generated weak phreatic explosions since 2011 (BGVN 44:08). The most recent eruptive period occurred during late March-early June 2019, primarily consisting of small phreatic explosions, minor deposits on the N crater rim, and gas-and-steam emissions. The report period of August 2019-March 2020 was characterized by similar activity, including small phreatic explosions, gas-and-steam plumes, ash and lake sediment ejecta, and volcanic tremors. The most significant activity during this time occurred on 30 January, where a phreatic explosion ejected ash and lake sediment above the crater rim, resulting in a pyroclastic flow which gradually turned into a lahar. Information for this reporting period of August 2019-March 2020 comes from the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA) using weekly bulletins.

According to OVSICORI-UNA, a small hydrothermal eruption was recorded on 1 August 2019. The seismicity was low with a few long period (LP) earthquakes around 1 August and intermittent background tremor. No explosions or emissions were reported through 11 September; seismicity remained low with an occasional LP earthquake and discontinuous tremor. The summit’s extension that has been recorded since the beginning of June stopped, and no significant deformation was observed in August.

Starting again in September 2019 and continuing intermittently through the reporting period, some deformation was observed at the base of the volcano as well as near the summit, according to OVSICORI-UNA. On 12 September an eruption occurred that was followed by volcanic tremors that continued through 15 September. In addition to these tremors, vigorous sustained gas-and-steam plumes were observed. The 16 September weekly bulletin did not describe any ejecta produced as a result of this event.

During 1-3 October small phreatic eruptions were accompanied by volcanic tremors that had decreased by 5 October. In November, volcanism and seismicity were relatively low and stable; few LP earthquakes were reported. This period of low activity remained through December. At the end of November, horizontal extension was observed at the summit, which continued through the first half of January.

Small phreatic eruptions were recorded on 2, 28, and 29 January 2020, with an increase in seismicity occurring on 27 January. On 30 January at 1213 a phreatic explosion produced a gas column that rose 1,500-2,000 m above the crater, with ash and lake sediment ejected up to 100 m above the crater. A news article posted by the Universidad de Costa Rica (UCR) noted that this explosion generated pyroclastic flows that traveled down the N flank for more than 2 km from the crater. As the pyroclastic flows moved through tributary channels, lahars were generated in the Pénjamo river, Zanjonuda gorge, and Azufrosa, traveling N for 4-10 km and passing through Buenos Aires de Upala (figure 29). Seismicity after this event decreased, though there were still some intermittent tremors.

Figure (see Caption) Figure 29. Photo of a lahar generated from the 30 January 2020 eruption at Rincon de la Vieja. Photo taken by Mauricio Gutiérrez, courtesy of UCR.

On 17, 24, and 25 February and 11, 17, 19, 21, and 23 March, small phreatic eruptions were detected, according to OVSICORI-UNA. Geodetic measurements observed deformation consisting of horizontal extension and inflation near the summit in February-March. By the week of 30 March, the weekly bulletin reported 2-3 small eruptions accompanied by volcanic tremors occurred daily during most days of the week. None of these eruptions produced solid ejecta, pyroclastic flows, or lahars, according to the weekly OVSICORI-UNA bulletins during February-March 2020.

Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 km3 Río Blanca tephra about 3500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/, https://www.facebook.com/OVSICORI/); Luis Enrique Brenes Portuguéz, University of Costa Rica, Ciudad Universitaria Rodrigo Facio Brenes, San José, San Pedro, Costa Rica (URL: https://www.ucr.ac.cr/noticias/2020/01/30/actividad-del-volcan-rincon-de-la-vieja-es-normal-segun-experto.html).


Manam (Papua New Guinea) — May 2020 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Minor explosive activity, continued thermal activity, and SO2 emissions, October 2019-March 2020.

Manam is a basaltic-andesitic stratovolcano that lies 13 km off the northern coast of mainland Papua New Guinea; it has a 400-year history of recorded evidence for recurring low-level ash plumes, occasional Strombolian activity, lava flows, pyroclastic avalanches, and large ash plumes from Main and South, the two active summit craters. The current eruption, ongoing since June 2014, produced multiple large explosive eruptions during January-September 2019, including two 15-km-high ash plumes in January, repeated SO2 plumes each month, and another 15.2 km-high ash plume in June that resulted in ashfall and evacuations of several thousand people (BGVN 44:10).

This report covers continued activity during October 2019 through March 2020. Information about Manam is primarily provided by Papua New Guinea's Rabaul Volcano Observatory (RVO), part of the Department of Mineral Policy and Geohazards Management (DMPGM). This information is supplemented with aviation alerts from the Darwin Volcanic Ash Advisory Center (VAAC). MODIS thermal anomaly satellite data is recorded by the University of Hawai'i's MODVOLC thermal alert recording system, and the Italian MIROVA project; sulfur dioxide monitoring is done by instruments on satellites managed by NASA's Goddard Space Flight Center. Satellite imagery provided by the Sentinel Hub Playground is also a valuable resource for information about this remote location.

A few modest explosions with ash emissions were reported in early October and early November 2019, and then not again until late March 2020. Although there was little explosive activity during the period, thermal anomalies were recorded intermittently, with low to moderate activity almost every month, as seen in the MODIS data from MIROVA (figure 71) and also in satellite imagery. Sulfur dioxide emissions persisted throughout the period producing emissions greater than 2.0 Dobson Units that were recorded in satellite data 3-13 days each month.

Figure (see Caption) Figure 71. MIROVA thermal anomaly data for Manam from 17 June 2019 through March 2020 indicate continued low and moderate level thermal activity each month from August 2019 through February 2020, after a period of increased activity in June and early July 2019. Courtesy of MIROVA.

The Darwin VAAC reported an ash plume in visible satellite imagery moving NW at 3.1 km altitude on 2 October 2019. Weak ash emissions were observed drifting N for the next two days along with an IR anomaly at the summit. RVO reported incandescence at night during the first week of October. Visitors to the summit on 18 October 2019 recorded steam and fumarolic activity at both of the summit craters (figure 72) and recent avalanche debris on the steep slopes (figure 73).

Figure (see Caption) Figure 72. Steam and fumarolic activity rose from Main crater at Manam on 18 October 2019 in this view to the south from a ridge north of the crater. Google Earth inset of summit shows location of photograph. Courtesy of Vulkanologische Gesellschaft and Claudio Jung, used with permission.
Figure (see Caption) Figure 73. Volcanic debris covered an avalanche chute on the NE flank of Manam when visited by hikers on 18 October 2019. Courtesy of Vulkanologische Gesellschaft and Claudio Jung, used with permission.

On 2 November, a single large explosion at 1330 local time produced a thick, dark ash plume that rose about 1,000 m above the summit and drifted NW. A shockwave from the explosion was felt at the Bogia Government station located 40 km SE on the mainland about 1 minute later. RVO reported an increase in seismicity on 6 November about 90 minutes before the start of a new eruption from the Main Crater which occurred between 1600 and 1630; it produced light to dark gray ash clouds that rose about 1,000 m above the summit and drifted NW. Incandescent ejecta was visible at the start of the explosion and continued with intermittent strong pulses after dark, reaching peak intensity around 1900. Activity ended by 2200 that evening. The Darwin VAAC reported a discrete emission observed in satellite imagery on 8 November that rose to 4.6 km altitude and drifted WNW, although ground observers confirmed that no eruption took place; emissions were only steam and gas. There were no further reports of explosive activity until the Darwin VAAC reported an ash emission in visible satellite imagery on 20 March 2020 that rose to 3.1 km altitude and drifted E for a few hours before dissipating.

Although explosive activity was minimal during the period, SO2 emissions, and evidence for continued thermal activity were recorded by satellite instruments each month. The TROPOMI instrument on the Sentinel-5P satellite captured evidence each month of SO2 emissions exceeding two Dobson Units (figure 74). The most SO2 activity occurred during October 2019, with 13 days of signatures over 2.0 DU. There were six days of elevated SO2 each month in November and December, and five days in January 2020. During February and March, activity was less, with smaller SO2 plumes recording more than 2.0 DU on three days each month. Sentinel-2 satellite imagery recorded thermal anomalies at least once from one or both of the summit craters each month between October 2019 and March 2020 (figure 75).

Figure (see Caption) Figure 74. SO2 emissions at Manam exceeded 2 Dobson Units multiple days each month between October 2019 and March 2020. On 3 October 2019 (top left) emissions were also measured from Ulawun located 700 km E on New Britain island. On 30 November 2019 (top middle), in addition to a plume drifting N from Manam, a small SO2 plume was detected at Bagana on Bougainville Island, 1150 km E. The plume from Manam on 2 December 2019 drifted ESE (top right). On 26 January 2020 the plume drifted over 300 km E (bottom left). The plumes measured on 29 February and 4 March 2020 (bottom middle and right) only drifted a few tens of kilometers before dissipating. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 75. Sentinel-2 satellite imagery with Atmospheric penetration rendering (bands 12, 11, and 8a) showed thermal anomalies at one or both of Manam’s summit craters each month during October 2019-March 2020. On 17 October 2019 (top left) a bright anomaly and weak gas plume drifted NW from South crater, while a dense steam plume and weak anomaly were present at Main crater. On 25 January 2020 (top right) the gas and steam from the two craters were drifting E; the weaker Main crater thermal anomaly is just visible at the edge of the clouds. A clear image on 5 March 2020 (bottom left) shows weak plumes and distinct thermal anomalies from both craters; on 20 March (bottom right) the anomalies are still visible through dense cloud cover that may include steam from the crater vents as well. Courtesy of Sentinel Hub Playground.

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; 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/); 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); Vulkanologische Gesellschaft (URL: https://twitter.com/vulkanologen/status/1194228532219727874, https://twitter.com/vulkanologen/status/1193788836679225344); Claudio Jung, (URL: https://www.facebook.com/claudio.jung.1/posts/10220075272173895, https://www.instagram.com/jung.claudio/).


Stromboli (Italy) — April 2020 Citation iconCite this Report

Stromboli

Italy

38.789°N, 15.213°E; summit elev. 924 m

All times are local (unless otherwise noted)


Strombolian activity continues at both summit crater areas, September-December 2019

Near-constant fountains of lava at Stromboli have served as a natural beacon in the Tyrrhenian Sea for at least 2,000 years. Eruptive activity at the summit consistently occurs from multiple vents at both a north crater area (N area) and a southern crater group (CS area) on the Terrazza Craterica at the head of the Sciara del Fuoco, a large scarp that runs from the summit down the NW side of the volcano-island (figure 168). Periodic lava flows emerge from the vents and flow down the scarp, sometimes reaching the sea; occasional large explosions produce ash plumes and pyroclastic flows. Thermal and visual cameras that monitor activity at the vents are located on the nearby Pizzo Sopra La Fossa, above the Terrazza Craterica, and at multiple locations on the flanks of the volcano. Detailed information for Stromboli is provided by Italy's Istituto Nazionale di Geofisica e Vulcanologia (INGV) as well as other satellite sources of data; September-December 2019 is covered in this report.

Figure (see Caption) Figure 168. This shaded relief map of Stromboli’s crater area was created from images acquired by drone on 9 July 2019 (In collaboration with GEOMAR drone group, Helmholtz Center for Ocean Research, Kiel, Germany). Inset shows Stromboli Island, the black rectangle indicates the area of the larger image, the black curved and the red hatched lines indicate, respectively, the morphological escarpment and the crater edges. Courtesy of INGV (Rep. No. 50/2019, Stromboli, Bollettino Settimanale, 02/12/2019 - 08/12/2019, data emissione 10/12/2019).

Activity was very consistent throughout the period of September-December 2019. Explosion rates ranged from 2-36 per hour and were of low to medium-high intensity, producing material that rose from less than 80 to over 150 m above the vents on occasion (table 7). The Strombolian activity in both crater areas often sent ejecta outside the crater rim onto the Terrazza Craterica, and also down the Sciara del Fuoco towards the coast. After the explosions of early July and late August, thermal activity decreased to more moderate levels that persisted throughout the period as seen in the MIROVA Log Radiative Power data (figure 169). Sentinel-2 satellite imagery supported descriptions of the constant glow at the summit, revealing incandescence at both summit areas, each showing repeating bursts of activity throughout the period (figure 170).

Table 7. Monthly summary of activity levels at Stromboli, September-December 2019. Low-intensity activity indicates ejecta rising less than 80 m, medium-intensity is ejecta rising less than 150 m, and high-intensity is ejecta rising over 200 m above the vent. Data courtesy of INGV.

Month Activity
Sep 2019 Explosion rates varied from 11-36 events per hour and were of low- to medium intensity (producing 80-120 m high ejecta). Lapilli and bombs were typical from the N area, and coarse and finer-grained tephra (lapilli and ash) were most common in the CS area. The Strombolian activity in both crater areas often sent ejecta outside the crater rim onto the terrace, and also down the Sciara del Fuoco towards the coast.
Oct 2019 Typical Strombolian activity and degassing continued. Explosions rates varied from 2-21 events per hour. Low intensity activity was common in the N area (ejecta less than 80 m high) and low to moderate intensity activity was typical in the CS area, with a few explosions rising over 150 m high. Lapilli and bombs were typical from the N area, and coarse and finer-grained tephra (lapilli and ash) were most common in the CS area. Some of the explosions sent ejecta down the Sciara del Fuoco.
Nov 2019 Typical Strombolian activity and degassing continued. Explosion rates varied from 11-23 events per hour with ejecta rising usually 80-150 m above the vents. Occasional explosions rose 250 m high. In the N area, explosions were generally low intensity with coarse material (lapilli and bombs). In many explosions, ejecta covered the outer slopes of the area overlooking the Sciara del Fuoco, and some blocks rolled for a few hundred meters before stopping. In the CS area, coarse material was mixed with fine and some explosions sent ejecta onto the upper part of the Sciara del Fuoco.
Dec 2019 Strombolian activity and degassing continued. Explosion rates varied from 12-26 per hour. In the N area, explosion intensity was mainly medium-low (less than 150 m) with coarse ejecta while in the CS area it was usually medium-high (more than 150 m) with both coarse and fine ejecta. In many explosions, debris covered the outer slopes of the area overlooking the Sciara del Fuoco, and some blocks rolled for a few hundred meters before stopping. Spattering activity was noted in the southern vents of the N area.
Figure (see Caption) Figure 169. Thermal activity at Stromboli was high during July-August 2019, when two major explosions occurred. Activity continued at more moderate levels through December 2019 as seen in the MIROVA graph of Log Radiative Power from 8 June through December 2019. Courtesy of MIROVA.
Figure (see Caption) Figure 170. Stromboli reliably produced strong thermal signals from both of the summit vents throughout September-December 2019 and has done so since long before Sentinel-2 satellite imagery was able to detect it. Image dates are (top, l to r) 5 September, 15 October, 20 October, (bottom l to r) 14 November, 14 December 2019, and 3 January 2020. Sentinel-2 imagery uses Atmospheric penetration rendering with bands 12, 11, and 8A, courtesy of Sentinel Hub Playground.

After a major explosion with a pyroclastic flow on 28 August 2019, followed by lava flows that reached the ocean in the following days (BGVN 44:09), activity diminished in early September to levels more typically seen in recent times. This included Strombolian activity from vents in both the N and CS areas that sent ejecta typically 80-150 m high. Ejecta from the N area generally consisted of lapilli and bombs, while the material from the CS area was often finer grained with significant amounts of lapilli and ash. The number of explosive events remained high in September, frequently reaching 25-30 events per hour. The ejecta periodically landed outside the craters on the Terrazza Craterica and even traveled partway down the Sciara del Fuoco. An inspection on 7 September by INGV revealed four eruptive vents in the N crater area and five in the S crater area (figure 171). The most active vents in the N area were N1 with mostly ash emissions and N2 with Strombolian explosions rich in incandescent coarse material that sometimes rose well above 150 m in height. In the S area, S1 and S2 produced jets of lava that often reached 100 m high. A small cone was observed around N2, having grown after the 28 August explosion. Between 11 and 13 September aerial surveys with drones produced detailed visual and thermal imagery of the summit (figure 172).

Figure (see Caption) Figure 171. Video of the Stromboli summit taken with a thermal camera on 7 September 2019 from the Pizzo sopra la Fossa revealed four active vents in the N area and five active vents in the S area. Images prepared by Piergiorgio Scarlato, courtesy of INGV (Rep. No. 37.2/2019, Stromboli, Bollettino Giornaliero del 10/09/2019).
Figure (see Caption) Figure 172. An aerial drone survey on 11 September 2019 at Stromboli produced a detailed view of the N and CS vent areas (left) and thermal images taken by a drone survey on 13 September (right) showed elevated temperatures down the Sciara del Fuoco in addition to the vents in the N and CS areas. Images by E. De Beni and M. Cantarero, courtesy of INGV (Rep. No. 37.5/2019, Stromboli, Bollettino Giornaliero del 13/09/2019).

Strombolian activity from the N crater on 28 September and 1 October 2019 produced blocks and debris that rolled down the Sciara del Fuoco and reached the ocean (figure 173). Explosive activity from the CS crater area sometimes produced ejecta over 150 m high (figure 174). A survey on 26 November revealed that a layer of ash 5-10 cm thick had covered the bombs and blocks that were deposited on the Pizzo Sopra la Fossa during the explosions of 3 July and 28 August (figure 175). On the morning of 27 December a lava flow emerged from the CS area and traveled a few hundred meters down the Sciara del Fuoco. The frequency of explosive events remained relatively constant from September through December 2019 after decreasing from higher levels during July and August (figure 176).

Figure (see Caption) Figure 173. Strombolian activity from vents in the N crater area of Stromboli produced ejecta that traveled all the way to the bottom of the Sciara del Fuoco and entered the ocean. Top images taken 28 September 2019 from the 290 m elevation viewpoint by Rosanna Corsaro. Bottom images captured on 1 October from the webcam at 400 m elevation. Courtesy of INGV (Rep. No. 39.0/2019 and Rep. No. 40.3, Stromboli, Bollettino Giornaliero del 29/09/2019 and 02/10/2019).
Figure (see Caption) Figure 174. Ejecta from Strombolian activity at the CS crater area of Stromboli rose over 150 m on multiple occasions. The webcam located at the 400 m elevation site captured this view of activity on 8 November 2019. Courtesy of INGV (Rep. No. 45.5/2019, Stromboli, Bollettino Giornaliero del 08/11/2019).
Figure (see Caption) Figure 175. The Pizzo Sopra la Fossa area at Stromboli was covered with large blocks and pyroclastic debris on 6 September 2019, a week after the major explosion of 28 August (top). By 26 November, 5-10 cm of finer ash covered the surface; the restored webcam can be seen at the far right edge of the Pizzo (bottom). Courtesy of INGV (Rep. No. 49/2019, Stromboli, Bollettino Settimanale, 25/11/2019 - 01/12/2019, data emissione 03/12/2019).
Figure (see Caption) Figure 176. The average hourly frequency of explosive events at Stromboli captured by surveillance cameras from 1 June 2019 through 5 January 2020 remained generally constant after the high levels seen during July and August. The Total value (blue) is the sum of the average daily hourly frequency of all explosive events produced by active vents.

Geologic Background. Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy, (URL: http://www.ct.ingv.it/en/); 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).


Semeru (Indonesia) — April 2020 Citation iconCite this Report

Semeru

Indonesia

8.108°S, 112.922°E; summit elev. 3657 m

All times are local (unless otherwise noted)


Ash plumes and thermal anomalies continue during September 2019-February 2020

Semeru is a stratovolcano located in East Java, Indonesia containing an active Jonggring-Seloko vent at the Mahameru summit. Common activity has consisted of ash plumes, pyroclastic flows and avalanches, and lava flows that travel down the SE flank. This report updates volcanism from September 2019 to February 2020 using primary information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) and the Darwin Volcanic Ash Advisory Centre (VAAC).

The dominant activity at Semeru for this reporting period consists of ash plumes, which were frequently reported by the Darwin VAAC. An eruption on 10 September 2019 produced an ash plume rising 4 km altitude drifting WNW, as seen in HIMAWARI-8 satellite imagery. Ash plumes continued to rise during 13-14 September. During the month of October the Darwin VAAC reported at least six ash plumes on 13, 14, 17-18, and 29-30 October rising to a maximum altitude of 4.6 km and moving primarily S and SW. Activity in November and December was relatively low, dominated mostly by strong and frequent thermal anomalies.

Volcanism increased in January 2020 starting with an eruption on 17 and 18 January that sent a gray ash plume up to 4.6 km altitude (figure 38). Eruptions continued from 20 to 26 January, producing ash plumes that rose up to 500 m above the crater that drifted in different directions. For the duration of the month and into February, ash plumes occurred intermittently. On 26 February, incandescent ejecta was ejected up to 50 m and traveled as far as 1000 m. Small sulfur dioxide emissions were detected in the Sentinel 5P/TROPOMI instrument during 25-27 February (figure 39). Lava flows during 27-29 February extended 200-1,000 m down the SE flank; gas-and-steam and SO2 emissions accompanied the flows. There were 15 shallow volcanic earthquakes detected on 29 February in addition to ash emissions rising 4.3 km altitude drifting ESE.

Figure (see Caption) Figure 38. Ash plumes rising from the summit of Semeru on 17 (left) and 18 (right) January 2020. Courtesy of MAGMA Indonesia and via Ø.L. Andersen's Twitter feed (left).
Figure (see Caption) Figure 39. Small SO2 plumes from Semeru were detected by the Sentinel 5P/TROPOMI instrument during 25 (left) and 26 (right) February 2020. Courtesy of NASA Goddard Space Flight Center.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed relatively weak and intermittent thermal anomalies occurring during May to August 2019 (figure 40). The frequency and power of these thermal anomalies significantly increased during September to mid-December 2019 with a few hotspots occurring at distances greater than 5 km from the summit. These farther thermal anomalies to the N and NE of the volcano do not appear to be caused by volcanic activity. There was a brief break in activity during mid-December to mid-January 2020 before renewed activity was detected in early February 2020.

Figure (see Caption) Figure 40. Thermal anomalies were relatively weak at Semeru during 30 April 2019-August 2019, but significantly increased in power and frequency during September to early December 2019. There was a break in activity from mid-December through mid-January 2020 with renewed thermal anomalies around February 2020. Courtesy of MIROVA.

The MODVOLC algorithm detected 25 thermal hotspots during this reporting period, which took place during 25 September, 18 and 21 October 2019, 29 January, and 11, 14, 16, and 23 February 2020. Sentinel-2 thermal satellite imagery shows intermittent hotspots dominantly in the summit crater throughout this reporting period (figure 41).

Figure (see Caption) Figure 41. Sentinel-2 thermal satellite imagery detected intermittent thermal anomalies (bright yellow-orange) at the summit of Semeru, which included some lava flows in late January to early February 2020. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); 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/); 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/); Øystein Lund Andersen (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: http://www.oysteinlundandersen.com).


Popocatepetl (Mexico) — April 2020 Citation iconCite this Report

Popocatepetl

Mexico

19.023°N, 98.622°W; summit elev. 5393 m

All times are local (unless otherwise noted)


Dome growth and destruction continues along with ash emissions and ejecta, September 2019-February 2020

Frequent historical eruptions have been reported from Mexico's Popocatépetl going back to the 14th century. Activity increased in the mid-1990s after about 50 years of quiescence, and the current eruption, ongoing since January 2005, has included numerous episodes of lava-dome growth and destruction within the 500-m-wide summit caldera. Multiple emissions of steam and gas occur daily, rising generally 1-3 km above the summit at about 5,400 m elevation; many contain small amounts of ash. Larger, more explosive events with ash plumes and incandescent ejecta landing on the flanks occur frequently. Activity through August 2019 was typical of the ongoing eruption with near-constant emissions of water vapor, gas, and minor ash, as well as multiple explosions with ash plumes and incandescent blocks scattered on the flanks (BGVN 44:09). This report covers similar activity from September 2019 through February 2020. Information comes from daily reports provided by México's Centro Nacional de Prevención de Desastres (CENAPRED); ash plumes are reported by the Washington Volcanic Ash Advisory Center (VAAC). Satellite visible and thermal imagery and SO2 data also provide helpful observations of activity.

Activity summary. Activity at Popocatépetl during September 2019-February 2020 continued at the high levels that have been ongoing for many years, characterized by hundreds of daily low-intensity emissions that included steam, gas, and small amounts of ash, and periods with multiple daily minor and moderate explosions that produce kilometer-plus-high ash plumes (figure 140). The Washington VAAC issued multiple daily volcanic ash advisories with plume altitudes around 6 km for many, although some were reported as high as 8.2 km. Hundreds of minutes of daily tremor activity often produced ash emissions as well. Incandescent ejecta landed 500-1,000 m from the summit frequently. The MIROVA thermal anomaly data showed near-constant moderate to high levels of thermal energy throughout the period (figure 141).

Figure (see Caption) Figure 140. Emissions continued at a high rate from Popocatépetl throughout September 2019-February 2020. Daily low-intensity emissions numbered usually in the hundreds (blue, left axis), while less frequent minor (orange) and moderate (green) explosions, plotted on the right axis, occurred intermittently through November 2019, and increased again during February 2020. Data was compiled from CENAPRED daily reports.
Figure (see Caption) Figure 141. MIROVA log radiative power thermal data for Popocatépetl from 1 May 2019 through February 2020 showed a constant output of moderate energy the entire time. Courtesy of MIROVA.

Sulfur dioxide emissions were measured with satellite instruments many days of each month from September 2019 thru February 2020. The intensity and drift directions varied significantly; some plumes remained detectable hundreds of kilometers from the volcano (figure 142). Plumes were detected almost daily in September, and on most days in October. They were measured at lower levels but often during November, and after pulses in early and late December only small plumes were visible during January 2020. Intermittent larger pulses returned in February. Dome growth and destruction in the summit crater continued throughout the period. A small dome was observed inside the summit crater in late September. Dome 85, 210-m-wide, was observed inside the summit crater in early November. Satellite imagery captured evidence of dome growth and ash emissions throughout the period (figure 143).

Figure (see Caption) Figure 142. Sulfur dioxide emissions from Popocatépetl were frequent from September 2019 through February 2020. Plumes drifted SW on 7 September (top left), 30 October (top middle), and 21 February (bottom right). SO2 drifted N and NW on 26 November (top right). On 2 December (bottom left) a long plume of sulfur dioxide hundreds of kilometers long drifted SW over the Pacific Ocean while the drift direction changed to NW closer to the volcano. The SO2 plumes measured in January (bottom center) were generally smaller than during the other months covered in this report. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 143. Sentinel-2 satellite imagery of Popocatépetl during November 2019-February 2020 provided evidence for ongoing dome growth and explosions with ash emissions. Top left: a ring of incandescence inside the summit crater on 8 November 2019 was indicative of the growth of dome 85 observed by CENAPRED. Top middle: incandescence on 8 December inside the summit crater was typical of that observed many times during the period. Top right: a dense, narrow ash plume drifted N from the summit on 17 January 2020. Bottom left: Snow cover made ashfall on 6 February easily visible on the E flank. On 11 February, the summit crater was incandescent and nearly all the snow was covered with ash. Bottom right: a strong thermal anomaly and ash emission were captured on 21 February. Bottom left and top right images use Natural color rendering (bands 4, 3, 2); other images use Atmospheric penetration rendering to show infrared signal (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Activity during September-November 2019. On 1 September 2019 minor ashfall was reported in the communities of Atlautla, Ozumba, Juchitepec, and Tenango del Aire in the State of Mexico. The ash plumes rose less than 2 km above the summit and incandescent ejecta traveled less than 100 m from the summit crater. Twenty-two minor and three moderate explosions were recorded on 4-5 September along with minor ashfall in Juchitepec, Tenango del Aire, Tepetlixpa, and Atlautla. During a flyover on 5 September, officials did not observe a dome within the crater, and the dimensions remained the same as during the previous visit (350 m in diameter and 150 m deep) (figure 144). Ashfall was reported in Tlalmanalco and Amecameca on 6 September. The following day incandescent ejecta was visible on the flanks near the summit and ashfall was reported in Amecameca, Ayapango, and Tenango del Aire. The five moderate explosions on 8 September produced ash plumes that rose as high as 2 km above the summit, and incandescent ejecta on the flanks. Explosions on 10 September sent ejecta 500 m from the crater. Eight explosions during 20-21 September produced ejecta that traveled up to 1.5 km down the flanks (figure 145). During an overflight on 27 September specialists from the National Center for Disaster Prevention (CENAPRED ) of the National Coordination of Civil Protection and researchers from the Institute of Geophysics of UNAM observed a new dome 30 m in diameter; the overall crater had not changed size since the overflight in early September.

Figure (see Caption) Figure 144. CENAPRED carried out overflights of Popocatépetl on 5 (left) and 27 September (right) 2019; the crater did not change in size, but a new dome 30 m in diameter was visible on 27 September. Courtesy of CENAPRED (Sobrevuelo al volcán Popocatépetl, 05 y 27 de septiembre).
Figure (see Caption) Figure 145. Ash plumes at Popocatépetl on 19 (left) and 20 (right) September 2019 rose over a kilometer above the summit before dissipating. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 19 y 20 de septiembre).

Fourteen explosions were reported on 2 October 2019. The last one produced an ash plume that rose 2 km above the summit and sent incandescent ejecta down the E slope (figure 146). Ashfall was reported in the municipalities of Atlautla Ozumba, Ayapango and Ecatzingo in the State of Mexico. Explosions on 3 and 4 October also produced ash plumes that rose between 1 and 2 km above the summit and sent ejecta onto the flanks. Additional incandescent ejecta was reported on 6, 7, 15, and 19 October. The communities of Amecameca, Tenango del Aire, Tlalmanalco, Cocotitlán, Temamatla, and Tláhuac reported ashfall on 10 October; Amecameca reported more ashfall on 12 October. On 22 October slight ashfall appeared in Amecameca, Tenango del Aire, Tlalmanalco, Ayapango, Temamatla, and Atlautla.

Figure (see Caption) Figure 146. Incandescent ejecta at Popocatépetl traveled down the E slope on 2 October 2019 (left); an ash plume two days later rose 2 km above the summit (right). Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 2 y 4 de octubre).

During 2-3 November 2019 there was 780 minutes of tremor reported in four different episodes. The seismicity was accompanied by ash emissions that drifted W and NW and produced ashfall in numerous communities, including Amecameca, Juchitepec, Ozumba, Tepetlixpa, and Atlautla in the State of México, in Ayapango and Cuautla in the State of Morelos, and in the municipalities of Tlahuac, Tlalpan, and Xochimilco in Mexico City. A moderate explosion on 4 November sent incandescent ejecta 2 km down the slopes and produced an ash plume that rose 1.5 km and drifted NW. Minor ashfall was reported in Tlalmanalco, Amecameca, and Tenango del Aire, State of Mexico. Similar ash plumes from explosions occurred the following day. Scientists from CENAPRED and the Institute of Geophysics of UNAM observed dome number 85 during an overflight on 5 November 2019. It had a diameter of 210 m and was 80 m thick, with an irregular surface (figure 147). Multiple explosions on 6 and 7 November produced incandescent ejecta; a moderate explosion late on 11 November produced ejecta that traveled 1.5 km from the summit and produced an ash plume 2 km high (figure 148). A lengthy period of constant ash emission that drifted E was reported on 18 November. A moderate explosion on 28 November sent incandescent fragments 1.5 km down the slopes and ash one km above the summit.

Figure (see Caption) Figure 147. A new dome was visible inside the summit crater at Popocatépetl during an overflight on 5 November 2019. It had a diameter of 210 m and was 80 m thick. Courtesy of CENAPRED (Sobrevuelo al volcán Popocatépetl, 05 de noviembre).
Figure (see Caption) Figure 148. Ash emissions and explosions with incandescent ejecta continued at Popocatépetl during November 2019. The ash plume on 1 November changed drift direction sharply a few hundred meters above the summit (left). Incandescent ejecta traveled 1.5 km down the flanks on 11 November (right). Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 1 y 12 de noviembre).

Activity during December 2019-February 2020. Throughout December 2019 weak emissions of steam and gas were reported daily, sometimes with minor amounts of ash, and minor explosions were only reported on 21 and 27 December. On 21 December two new high-resolution webcams were installed around Popocatépetl, one 5 km from the crater at the Tlamacas station, and the second in San Juan Tianguismanalco, 20 km away. Ash emissions and incandescent ejecta 800 m from the summit were observed on 25 December (figure 149). Incandescence at night was reported during 27-29 December.

Figure (see Caption) Figure 149. Incandescent ejecta moved 800 m down the flanks of Popocatépetl during explosions on 25 December 2019 (left); weak emissions of steam, gas, and minor ash were visible on 27 December and throughout the month. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 25 y 27 de diciembre).

Continuous emissions of water vapor and gas with low ash content were typical daily during January 2020. A moderate explosion on 9 January produced an ash plume that rose 3 km from the summit and drifted NE. In addition, incandescent ejecta traveled 1 km from the crater rim. A minor explosion on 21 January produced a 1.5-km-high plume with low ash content and incandescent ejecta that fell near the crater (figure 150). The first of two explosions late on 27 January produced ejecta that traveled 500 m and a 1-km-high ash plume. Constant incandescence was observed overnight on 29-30 January.

Figure (see Caption) Figure 150. Although fewer explosions were recorded at Popocatépetl during January 2020, activity continued. An ash plume on 19 January rose over a kilometer above the summit (top left). A minor explosion on 21 January produced a 1.5-km-high plume with low ash content and incandescent ejecta that fell near the crater (top right). Smaller emissions with steam, gas, and ash were typical many days, including on 22 (bottom left) and 31 (bottom right) January 2019. Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl 19, 21, 22 y 31 de enero).

A moderate explosion on 5 February 2020 produced an ash plume that rose 1.5 km and drifted NNE. Explosions on 10 and 13 February sent ejecta 500 m down the flanks (figure 151). During an overflight on 18 February scientists noted that the internal crater maintained a diameter of 350 m and its approximate depth was 100-150 m; the crater was covered by tephra. For most of the second half of February the volcano had a continuous emission of gases with minor amounts of ash. In addition, multiple explosions produced ash plumes that rose 400-1,200 m above the crater and drifted in several different directions.

Figure (see Caption) Figure 151. Ash emissions and explosions continued at Popocatépetl during February 2020. Dense ash drifted near the snow-covered summit on 6 February (top left). Incandescent ejecta traveled 500 m down the flanks on 13 February (top right). Ash plumes billowed from the summit on 18 and 22 February (bottom row). Courtesy of CENAPRED (Reporte del monitoreo de CENAPRED al volcán Popocatépetl, 6, 15, 18 y 22 de febrero).

Geologic Background. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Information Contacts: Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México D.F. 04360, México (URL: http://www.cenapred.unam.mx/), Daily Report Archive http://www.cenapred.unam.mx:8080/reportesVolcanGobMX/BuscarReportesVolcan); 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/); 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).


Santa Maria (Guatemala) — April 2020 Citation iconCite this Report

Santa Maria

Guatemala

14.757°N, 91.552°W; summit elev. 3745 m

All times are local (unless otherwise noted)


Daily explosions with ash plumes and block avalanches continue, September 2019-February 2020

The dacitic Santiaguito lava-dome complex on the W flank of Guatemala's Santa María volcano has been growing and actively erupting since 1922. Ash explosions, pyroclastic, and lava flows have emerged from Caliente, the youngest of the four vents in the complex, for more than 40 years. A lava dome that appeared within the summit crater of Caliente in October 2016 has continued to grow, producing frequent block avalanches down the flanks. Daily explosions with ash plumes and block avalanches continued during September 2019-February 2020, the period covered in this report, with information primarily from Guatemala's INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meterologia e Hidrologia) and the Washington VAAC (Volcanic Ash Advisory Center).

Constant fumarolic activity with steam and gas persisted from the Caliente dome throughout September 2019-February 2020. Explosions occurred multiple times per day, producing ash plumes that rose to altitudes of 3.1-3.5 km and usually drifted a few kilometers before dissipating. Several lahars during September and October carried volcanic blocks, ash, and debris down major drainages. Periodic ashfall was reported in communities within 10 km of the volcano. An increase in thermal activity beginning in November (figure 101) resulted in an increased number of observations of incandescence visible at night from the summit of Caliente through February 2020. Block avalanches occurred daily on the flanks of the dome, often reaching the base, stirring up small clouds of ash that drifted downwind.

Figure (see Caption) Figure 101. The MIROVA project graph of thermal activity at Santa María from 12 May 2019 through February 2020 shows a gradual increase in thermal energy beginning in November 2019. This corresponds to an increase in the number of daily observations of incandescence at the summit of the Caliente dome during this period. Courtesy of MIROVA.

Constant steam and gas fumarolic activity rose from the Caliente dome, drifting W, usually rising to 2.8-3.0 km altitude during September 2019. Multiple daily explosions with ash plumes rising to 2.9-3.4 km altitude drifted W or SW over the communities of San Marcos, Loma Linda Palajunoj, and Monte Claro (figure 102). Constant block avalanches fell to the base of the cone on the NE and SE flanks. The Washington VAAC reported an ash plume visible in satellite imagery on 10 September at 3.1 km altitude drifting W. On 14 September another plume was spotted moving WSW at 4.6 km altitude which dissipated quickly; the webcam captured another plume on 16 September. Ashfall on 27 September reached about 1 km from the volcano; it reached 1.5 km on 29 September. Lahars descended the Rio Cabello de Ángel on 2 and 24 September (figure 102). They were about 15 m wide, and 1-3 m deep, carrying blocks 1-2 m in diameter.

Figure (see Caption) Figure 102. A lahar descended the Rio Cabello de Ángel at Santa Maria and flowed into the Rio Nima 1 on 24 September 2019. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 21 al 27 de septiembre de 2019).

Througout October 2019, degassing of steam with minor gases occurred from the Caliente summit, rising to 2.9-3.0 km altitude and generally drifting SW. Weak explosions took place 1-5 times per hour, producing ash plumes that rose to 3.2-3.5 km altitude. Ashfall was reported in Monte Claro on 2 October. Nearly constant block avalanches descended the SE and S flanks, disturbing recent layers of fine ash and producing local ash clouds. Moderate explosions on 11 October produced ash plumes that rose to 3.5 km altitude and drifted W and SW about 1.5 km towards Río San Isidro (figure 103). The following day additional plumes drifted a similar distance to the SE. The Washington VAAC reported an ash emission visible in satellite imagery at 4.9 km altitude on 13 October drifting NNW. Ashfall was reported in Parcelamiento Monte Claro on 14 October. Some of the block avalanches observed on 14 October on the SE, S, and SW flanks were incandescent. Ash drifted 1.5 km W and SW on 17 October. Ashfall was reported near la finca Monte Claro on 25 and 28 October. A lahar descended the Río San Isidro, a tributary of the Río El Tambor on 7 October carrying blocks 1-2 m in diameter, tree trunks, and branches. It was about 16 m wide and 1-2 m deep. Additional lahars descended the rio Cabello de Angel on 23 and 24 October. They were about 15 m wide and 2 m deep, and carried ash and blocks 1-2 m in diameter, tree trunks, and branches.

Figure (see Caption) Figure 103. Daily ash plumes were reported from the Caliente cone at Santa María during October 2019, similar to these from 30 September (left) and 11 October 2019 (right). Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 28 de septiembre al 04 de octubre de 2019; Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 05 al 11 de octubre de 2019).

During November 2019, steam plumes rose to 2.9-3.0 km altitude and generally drifted E. There were 1-3 explosions per hour; the ash plumes produced rose to altitudes of 3.1-3.5 km and often drifted SW, resulting in ashfall around the volcanic complex. Block avalanches descended the S and SW flanks every day. On 4 November ashfall was reported in the fincas (ranches) of El Faro, Santa Marta, El Viejo Palmar, and Las Marías, and the odor of sulfur was reported 10 km S. Incandescence was observed at the Caliente dome during the night of 5-6 November. Ash fell again in El Viejo Palmar, fincas La Florida, El Faro, and Santa Marta (5-6 km SW) on 7 November. Sulfur odor was also reported 8-10 km S on 16, 19, and 22 November. Fine-grained ash fell on 18 November in Loma Linda and San Marcos Palajunoj. On 29 November strong block avalanches descended in the SW flank, stirring up reddish ash that had fallen on the flanks (figure 104). The ash drifted up to 20 km SW.

Figure (see Caption) Figure 104. Ash plumes rose from explosions multiple times per day at Santa Maria’s Santiaguito complex during November 2019, and block avalanches stirred up reddish clouds of ash that drifted for many kilometers. Courtesy of INSIVUMEH. Left, 11 November 2019, from Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 09 al 15 de noviembre de 2019. Right, 29 November 2019 from BOLETÍN VULCANOLÓGICO ESPECIAL BESTG# 106-2019, Guatemala 29 de noviembre de 2019, 10:50 horas (Hora Local).

White steam plumes rising to 2.9-3.0 km altitude drifted SE most days during December 2019. One to three explosions per hour produced ash plumes that rose to 3.1-3.5 km altitude and drifted W and SW producing ashfall on the flanks. Several strong block avalanches sent material down the SW flank. Ash from the explosions drifted about 1.5 km SW on 3 and 7 December. The Washington VAAC reported a small ash emission that rose to 4.9 km altitude and drifted WSW on 8 December, and another on 13 December that rose to 4.3 km altitude. Ashfall was reported up to 10 km S on 24 December. Incandescence was reported at the dome by INSIVUMEH eight times during the month, significantly more than during the recent previous months (figure 105).

Figure (see Caption) Figure 105. Strong thermal anomalies were visible in Sentinel-2 imagery at the summit of the Caliente cone at Santa María’s Santiaguito’s complex on 19 December 2019. Image uses Atmospheric Penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Activity during January 2020 was similar to that during previous months. White plumes of steam rose from the Caliente dome to altitudes of 2.7-3.0 km and drifted SE; one to three explosions per hour produced ash plumes that rose to 3.2-3.4 km altitude and generally drifted about 1.5 km SW before dissipating. Frequent block avalanches on the SE flank caused smaller plumes that drifted SSW often over the ranches of San Marcos and Loma Linda Palajunoj. On 28 January ash plumes drifted W and SW over the communities of Calaguache, El Nuevo Palmar, and Las Marías. In addition to incandescence observed at the crater of Caliente dome at least nine times, thermal anomalies in satellite imagery were detected multiple times from the block avalanches on the S flank (figure 106).

Figure (see Caption) Figure 106. Incandescence at the summit and in the block avalanches on the S flank of the Caliente cone at Santa María’s Santiaguito’s complex was visible in Sentinel-2 satellite imagery on 8 and 13 January 2020. Atmospheric penetration rendering images (bands 12, 11, 8A) courtesy of Sentinel Hub Playground.

The Washington VAAC reported an ash plume visible in satellite imagery at 4.6 km altitude drifting W on 3 February 2020. INSIVUMEH reported constant steam degassing that rose to 2.9-3.0 km altitude and drifted SW. In addition, 1-3 weak to moderate explosions per hour produced ash plumes to 3.1-3.5 km altitude that drifted about 1 km SW. Small amounts of ashfall around the volcano’s perimeter was common. The ash plumes on 5 February drifted NE over Santa María de Jesús. On 8 February the ash plumes drifted E and SE over the communities of Calaguache, El Nuevo Palmar, and Las Marías. Block avalanches on the S and SE flanks of Caliente dome continued, creating small ash clouds on the flank. Incandescence continued frequently at the crater and was also observed on the S flank in satellite imagery (figure 107).

Figure (see Caption) Figure 107. Incandescence at the summit and on the S flank of the Caliente cone at Santa María’s Santiaguito’s complex was frequent during February 2020, including on 2 (left) and 17 (right) February 2020 as seen in Sentinel-2 imagery. Atmostpheric Penetration rendering imagery (bands 12, 11, 8A) courtesy of Sentinel Hub Playground.

Geologic Background. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/ ); 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); 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/).


Villarrica (Chile) — April 2020 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Brief increase in explosions, mid-September 2019; continued thermal activity through February 2020

Historical eruptions at Chile's Villarrica, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. An intermittently active lava lake at the summit has been the source of Strombolian activity, incandescent ejecta, and thermal anomalies for several decades; the current eruption has been ongoing since December 2014. Continuing activity during September 2019-February 2020 is covered in this report, with information provided by the Southern Andes Volcano Observatory (Observatorio Volcanológico de Los Andes del Sur, OVDAS), part of Chile's National Service of Geology and Mining (Servicio Nacional de Geología y Minería, SERNAGEOMIN), and Projecto Observación Villarrica Internet (POVI), part of the Fundacion Volcanes de Chile, a research group that studies volcanoes across Chile.

A brief period of heighted explosive activity in early September 2019 caused SERNAGEOMIN to raise the Alert Level from Yellow to Orange (on a four-color scale of Green-Yellow-Orange-Red) for several days. Increases in radiative power were visible in the MIROVA thermal anomaly data during September (figure 84). Although overall activity decreased after that, intermittent explosions were observed at the summit, and incandescence continued throughout September 2019-February 2020. Sentinel-2 satellite imagery indicated a strong thermal anomaly from the summit crater whenever the weather conditions permitted. In addition, ejecta periodically covered the area around the summit crater, and particulates often covered the snow beneath the narrow gas plume drifting S from the summit (figure 85).

Figure (see Caption) Figure 84. Thermal activity at Villarrica from 28 May 2019 through February 2020 was generally at a low level, except for brief periods in August and September 2019 when larger explosions were witnessed and recorded in seismic data and higher levels of thermal activity were noted by the MIROVA project. Courtesy of MIROVA.
Figure (see Caption) Figure 85. Natural-color (top) and Atmospheric penetration (bottom) renderings of three different dates during September 2019-February 2020 show typical continued activity at Villarica during the period. Dark ejecta periodically covered the snow around the summit crater, and streaks of particulate material were sometimes visible on the snow underneath the plumes of bluish gas drifting S from the volcano (top images). Persistent thermal anomalies were recorded in infrared satellite data on the same dates (bottom images). Dates recorded are (left to right) 28 September 2019, 20 December 2019, and 1 January 2020. Natural color rendering uses bands 4,3, and 2, and Atmospheric penetration rendering uses bands 12, 11, and 8a. Courtesy of Sentinel Hub Playground.

SERNAGEOMIN raised the Alert Level from Green to Yellow in early August 2019 due to the increase in activity that included incandescent ejecta and bombs reaching 200 m from the summit crater (BGVN 44:09). An increase in seismic tremor activity on 8 September was accompanied by vigorous Strombolian explosions reported by POVI. The following day, SERNAGEOMIN raised the Alert Level from Yellow to Orange. Poor weather prevented visual observations of the summit on 8 and 9 September, but high levels of incandescence were observed briefly on 10 September. Incandescent ejecta reached 200 m from the crater rim late on 10 September (figure 86). Activity increased the next day with ejecta recorded 400 m from the crater, and the explosions were felt 12 km from the summit.

Figure (see Caption) Figure 86. A new pulse of activity at Villarrica reached its maximum on 10 (left) and 11 (right) September 2019. Incandescent ejecta reached 200 m from the crater rim on 10 September and up to 400 m the following day. Courtesy of POVI (Volcan Villarrica, Resumen grafico del comportamiento, Septiembre 2019 a enero 2020).

Explosions decreased in intensity by 13 September, but avalanches of incandescent material were visible on the E flank in the early morning hours (figure 87). Small black plumes later in the day were interpreted by POVI as the result of activity from landslides within the crater. Fine ash deposited on the N and NW flanks during 16-17 September was attributed to wind moving ash from within the crater, and not to new emissions from the crater (figure 88). SERNAGEOMIN lowered the Alert Level to Yellow on 16 September as tremor activity decreased significantly. Activity continued to decrease during the second half of September; incandescence was moderate with no avalanches observed, and intermittent emissions with small amounts of material were noted. Degassing of steam plumes rose up to 120 m above the crater.

Figure (see Caption) Figure 87. By 13 September 2019, a decrease in activity at Villarrica was apparent. Incandescence (red arrow) was visible on the E flank of Villarrica early on 13 September (left). Fine ash, likely from small collapses of new material inside the vent, rose a short distance above the summit later in the day (right). Courtesy of POVI (Volcan Villarrica, Resumen grafico del comportamiento, Septiembre 2019 a Enero 2020).
Figure (see Caption) Figure 88. Fine-grained material covered the summit of Villarrica on 17 September 2019. POVI interpreted this as a result of strong winds moving fine ash-sized particles from within the crater and depositing them on the N and NW flanks. Courtesy of POVI (Volcan Villarrica, Resumen grafico del comportamiento, Septiembre 2019 a enero 2020).

Low-altitude degassing was typical activity during October-December 2019; occasionally steam and gas plumes rose 300 m above the summit, but they were generally less than 200 m high. Incandescence was visible at night when weather conditions permitted. Occasional Strombolian explosions were observed in the webcam (figure 89). During January and February 2020, similar activity was reported with steam plumes observed to heights of 300-400 m above the summit, and incandescence on nights where the summit was visible (figure 90). A drone overflight on 19 January produced a clear view into the summit crater revealing a 5-m-wide lava pit about 120 m down inside the crater (figure 91).

Figure (see Caption) Figure 89. Activity continued at a lower level at the summit of Villarrica from October-December 2019. The 30-m-wide vent at the bottom of the summit crater (120 m deep) of Villarrica (left) was emitting wisps of bluish gas on 30 October 2019. Sporadic Strombolian explosions ejected material around the crater rim on 12 December (right). Courtesy of POVI (Volcan Villarrica, Resumen grafico del comportamiento, Septiembre 2019 a enero 2020).
Figure (see Caption) Figure 90. Small explosive events were recorded at Villarrica during January and February 2020, including these events on 4 (left) and 18 (right) January where ejecta reached about 50 m above the crater rim. Courtesy of POVI (Volcan Villarrica, Resumen grafico del comportamiento, Septiembre 2019 a Enero 2020).
Figure (see Caption) Figure 91. An oblique view into the bottom of the summit crater of Villarrica on 19 January 2020 was captured by drone. The diameter of the lava pit was calculated at about 5 m and was about 120 m deep. Image copyright by Leighton M. Watson, used with permission; courtesy of POVI (Volcan Villarrica, Resumen grafico del comportamiento, Septiembre 2019 a Enero 2020).

Geologic Background. Glacier-clad Villarrica, one of Chile's most active volcanoes, rises above the lake and town of the same name. It is the westernmost of three large stratovolcanoes that trend perpendicular to the Andean chain. A 6-km-wide caldera formed during the late Pleistocene. A 2-km-wide caldera that formed about 3500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesitic cone at the NW margin of the Pleistocene caldera. More than 30 scoria cones and fissure vents dot the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Historical eruptions, documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Proyecto Observación Villarrica Internet (POVI) (URL: http://www.povi.cl/); 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); Leighton M. Watson, Department of Earth Sciences at the University of Oregon, Eugene, OR 97403-1272, USA (URL: https://earthsciences.uoregon.edu/).


Semisopochnoi (United States) — April 2020 Citation iconCite this Report

Semisopochnoi

United States

51.93°N, 179.58°E; summit elev. 1221 m

All times are local (unless otherwise noted)


Intermittent small explosions detected in December 2019 through mid-March 2020

Semisopochnoi is a remote stratovolcano located in the western Aleutians dominated by an 8 km-wide caldera containing the small (100 m diameter) Fenner Lake and a three-cone cluster: a northern cone known as the North cone of Mount Cerberus, an eastern cone known as the East cone of Mount Cerberus, and a southern cone known as the South cone of Mount Cerberus. Previous volcanism has included small explosions, ash deposits, and gas-and-steam emissions. This report updates activity during September 2019 through March 2020 using information from the Alaska Volcano Observatory (AVO). A new eruptive period began on 7 December 2019 and continued until mid-March 2020 with activity primarily focused in the North cone of Mount Cerberus.

During September-November 2019, low levels of unrest were characterized by intermittent weeks of elevated seismicity and gas-and-steam plumes visible on 8 September, 7-8 October, and 24 November. On 6 October an SO2 plume was visible in satellite imagery, according to AVO.

Seismicity increased on 5 December and was described as a strong tremor through 7 December. This tremor was associated with a small eruption on 7 December; intermittent explosions occurred and continued into the night. Increased seismicity was recorded throughout the rest of the month while AVO registered small explosions during 11-19 December. On 11-12 December, a gas-and-steam plume possibly containing some of ash extended 80 km (figure 2). Two more ash plumes were observed on 14 and 17 December, the latter of which extended 15 km SE. Sentinel-2 satellite images show gas-and-steam plumes rising from the North Cerberus crater intermittently at the end of 2019 and into early 2020 (figure 3).

Figure (see Caption) Figure 2. Sentinel-2 satellite image showing a gray ash plume extending up to 17 km SE from the North Cerberus crater on 11 December 2019. Image taken by Hannah Dietterich; courtesy of AVO.
Figure (see Caption) Figure 3. Sentinel-2 satellite images of gas-and-steam plumes at Semisopochnoi from late November 2019 through mid-March 2020. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

The month of January 2020 was characterized by low levels of unrest due to intermittent low seismicity. Small explosions were reported during 14-17 February and a gas-and-steam plume was visible on 26 February. Seismic unrest occurred between 18 February-7 March. Gas-and-steam plumes were visible on 1, 9, 14-17, 20, and 21 March (figure 4). During 15-17 March, small explosions occurred, according to AVO. Additionally, clear satellite images showed gas-and-steam emissions and minor ash deposits around North Cerberus’ crater rim. After 17 March the explosions subsided and ash emissions were no longer observed. However, intermittent gas-and-steam emissions continued and seismicity remained elevated through the end of the month.

Figure (see Caption) Figure 4. Satellite image of Semisopochnoi showing degassing within the North Cerberus crater on 22 March 2020. Image taken by Matt Loewen; courtesy of AVO.

Geologic Background. Semisopochnoi, the largest subaerial volcano of the western Aleutians, is 20 km wide at sea level and contains an 8-km-wide caldera. It formed as a result of collapse of a low-angle, dominantly basaltic volcano following the eruption of a large volume of dacitic pumice. The high point of the island is 1221-m-high Anvil Peak, a double-peaked late-Pleistocene cone that forms much of the island's northern part. The three-peaked 774-m-high Mount Cerberus volcano was constructed during the Holocene within the caldera. Each of the peaks contains a summit crater; lava flows on the northern flank of Cerberus appear younger than those on the southern side. Other post-caldera volcanoes include the symmetrical 855-m-high Sugarloaf Peak SSE of the caldera and Lakeshore Cone, a small cinder cone at the edge of Fenner Lake in the NE part of the caldera. Most documented historical eruptions have originated from Cerberus, although Coats (1950) considered that both Sugarloaf and Lakeshore Cone within the caldera could have been active during historical time.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Ubinas (Peru) — March 2020 Citation iconCite this Report

Ubinas

Peru

16.355°S, 70.903°W; summit elev. 5672 m

All times are local (unless otherwise noted)


Explosions produced ash plumes in September 2019; several lahars generated in January and February 2020

Ubinas, located 70 km from the city of Arequipa in Peru, has produced frequent eruptions since 1550 characterized by ash plumes, ballistic ejecta (blocks and bombs), some pyroclastic flows, and lahars. Activity is focused at the summit crater (figure 53). A new eruptive episode began on 24 June 2019, with an ash plume reaching 12 km altitude on 19 July. This report summarizes activity during September 2019 through February 2020 and is based on agency reports and satellite data.

Figure (see Caption) Figure 53. A PlanetScope satellite image of Ubinas on 16 December 2019. Courtesy of PlanetLabs.

Prior to September 2019 the last explosion occurred on 22 July. At 2145 on 1 September moderate, continuous ash emission occurred reaching nearly 1 km above the crater. An explosion produced an ash plume at 1358 on the 3rd that reached up to 1.3 km above the summit; six minutes later ashfall and lapilli up to 1.5 cm in diameter was reported 6 km away, with ashfall reported up to 8 km away (figure 54 and 55). Three explosions produced ash plumes at 0456, 0551, and 0844 on 4 September, with the two later ash plumes reaching around 2 km above the crater. The ash plume dispersed to the south and ashfall was reported in Ubinas, Tonohaya, San Miguel, Anascapa, Huatahua, Huarina, and Matalaque, reaching a thickness of 1 mm in Ubinas.

Figure (see Caption) Figure 54. An eruption at Ubinas produced an ash plume up to 1.3 km on at 1358 on 3 September 2019. Courtesy of INGEMMET.
Figure (see Caption) Figure 55. Ash and lapilli fall up to 1.5 cm in diameter was reported 6 km away from Ubinas on 3 September 2019 (top) and an Ingemmet geologist collects ash samples from the last three explosions. Courtesy of INGEMMET.

During 8-9 September there were three explosions generating ash plumes to less than 2.5 km, with the largest occurring at 1358 and producing ashfall in the Moquegua region to the south. Following these events, gas and water vapor were continuously emitted up to 1 km above the crater. There was an increase in seismicity during the 10-11th and an explosion produced a 1.5 km high (above the crater) ash plume at 0726 on the 12th, which dispersed to the S and SE (figure 56). During 10-15 September there was continuous emission of gas (blue in color) and steam up to 1.5 km above the volcano. Gas emission, thermal anomalies, and seismicity continued during 16-29 September, but no further explosions were recorded.

Figure (see Caption) Figure 56. An explosion at Ubinas on 12 September 2019 produced an ash plume to 1.5 km above the volcano. The ash dispersed to the S and SE. Courtesy of IGP.

Throughout October activity consisted of seismicity, elevated temperatures within the crater, and gas emissions reaching 800 to 1,500 m above the crater. No explosions were recorded. Drone footage released in early October (figure 57) shows the gas emissions and provided a view of the crater floor (figure 58). On the 15th IGP reported that the likelihood of an eruption had reduced.

Figure (see Caption) Figure 57. IGP flew a fixed-wing drone over Ubinas as part of their monitoring efforts. This photograph shows gas emissions rising from the summit crater, published on 7 October 2019. Courtesy of IGP.
Figure (see Caption) Figure 58. Drone image showing gas emissions and the summit crater of Ubinas. Image taken by IGP staff and released on 7 October 2019; courtesy of IGP.

Similar activity continued through early November with no reported explosions, and the thermal anomalies were no longer detected at the end of November (figure 59), although a faint thermal anomaly was visible in Sentinel-2 data in mid-December (figure 60). A rockfall occurred at 1138 on 13 November down the Volcanmayo gorge.

Figure (see Caption) Figure 59. This MIROA Log Radiative Power plot shows increased thermal energy detected at Ubinas during August through November 2019. Courtesy of MIROVA.
Figure (see Caption) Figure 60. Sentinel-2 thermal satellite image showing elevated temperatures in the Ubinas crater on 16 December 2019. Courtesy of Sentinel Hub Playground.

There were no explosions during January or February 2020, with seismicity and reduced gas emissions continuing. There was a small- to moderate-volume lahar generated at 1620 on 4 January down the SE flank. A second moderate- to high-volume lahar was generated at 1532 on 24 February, and three more lahars at 1325 and 1500 on 29 February, and at 1601 on 1 March, moved down the Volcanmayo gorge and the Sacohaya river channel. The last three lahars were of moderate to large volume.

Geologic Background. A small, 1.4-km-wide caldera cuts the top of Ubinas, Perú's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank about 3,700 years ago extend 10 km from the volcano. Widespread Plinian pumice-fall deposits include one of Holocene age about 1,000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Information Contacts: Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa, Peru (URL: http://ovi.ingemmet.gob.pe); Instituto Geofisico del Peru (IGP), Calle Badajoz N° 169 Urb. Mayorazgo IV Etapa, Ate, Lima 15012, Perú (URL: https://www.gob.pe/igp); 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/); Planet Labs, Inc. (URL: https://www.planet.com/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Yasur (Vanuatu) — March 2020 Citation iconCite this Report

Yasur

Vanuatu

19.532°S, 169.447°E; summit elev. 361 m

All times are local (unless otherwise noted)


Strombolian activity continues during June 2019 through February 2020

Yasur has remained on Alert Level 2 (on a scale of 0-4) since 18 October 2016, indicating "Major Unrest; Danger Zone remains at 395 m around the eruptive vents." The summit crater contains several active vents that frequently produce Strombolian explosions and gas plumes (figure 60). This bulletin summarizes activity during June 2019 through February 2020 and is based on reports by the Vanuatu Meteorology and Geo-Hazards Department (VMGD), visitor photographs and videos, and satellite data.

Figure (see Caption) Figure 60. The crater of Yasur contains several active vents that produce gas emissions and Strombolian activity. Photo taken during 25-27 October 2019 by Justin Noonan, used with permission.

A VMGD report on 27 June described ongoing Strombolian explosions with major unrest confined to the crater. The 25 July report noted the continuation of Strombolian activity with some strong explosions, and a warning that volcanic bombs may impact outside of the crater area (figure 61).

Figure (see Caption) Figure 61. A volcanic bomb (a fluid chunk of lava greater than 64 mm in diameter) that was ejected from Yasur. The pattern on the surface shows the fluid nature of the lava before it cooled into a solid rock. Photo taken during 25-27 October 2019 by Justin Noonan, used with permission.

No VMGD report was available for August, but Strombolian activity continued with gas emissions and explosions, as documented by visitors (figure 62). The eruption continued through September and October with some strong explosions and multiple active vents visible in thermal satellite imagery (figure 63). Strombolian explosions ejecting fluid lava from rapidly expanding gas bubbles were recorded during October, and likely represented the typical activity during the surrounding months (figure 64). Along with vigorous degassing producing a persistent plume there was occasional ash content (figure 65). At some point during 20-29 October a small landslide occurred along the eastern inner wall of the crater, visible in satellite images and later confirmed to have produced ashfall at the summit (figure 66).

Figure (see Caption) Figure 62. Different views of the Yasur vents on 7-8 August 2019 taken from a video. Strombolian activity and degassing were visible. Courtesy of Arnold Binas, used with permission.
Figure (see Caption) Figure 63. Sentinel-2 thermal satellite images show variations in detected thermal energy emitting from the active Yasur vents on 18 September and 22 December 2019. False color (bands 12, 11, 4) satellite images courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 64. Strombolian explosions at Yasur during 25-27 October 2019. Large gas bubbles rise to the top of the lava column and burst, ejecting volcanic bombs – fluid chunks of lava, out of the vent. Photos by Justin Noonan, used with permission.
Figure (see Caption) Figure 65. Gas and ash emissions rise from the active vents at Yasur between 25-27 October 2019. Photos by Justin Noonan, used with permission.
Figure (see Caption) Figure 66. Planet Scope satellite images of Yasur show a change in the crater morphology between 20 and 29 October 2019. Copyright of Planet Labs.

Continuous explosive activity continued in November-February with some stronger explosions recorded along with accompanying gas emissions. Gas plumes of sulfur dioxide were detected by satellite sensors on some days through this period (figure 67) and ash content was present at times (figure 68). Thermal anomalies continued to be detected by satellite sensors with varying intensity, and with a reduction in intensity in February, as seen in Sentinel-2 imagery and the MIROVA system (figures 69 and 70).

Figure (see Caption) Figure 67. SO2 plumes detected at Yasur by Aura/OMI on 21 December 2019 and 31 January 2020, drifting W to NW, and on 14 and 23 February 2020, drifting W and south, and NWW to NW. Courtesy of Global Sulfur Dioxide Monitoring Page, NASA.
Figure (see Caption) Figure 68. An ash plume erupts from Yasur on 20 February 2020 and drifts NW. Courtesy of Planet Labs.
Figure (see Caption) Figure 69. Sentinel-2 thermal satellite images show variations in detected thermal energy in the active Yasur vents during January and February 2020. False color (bands 12, 11, 4) satellite images courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 70. The MIROVA thermal detection system recorded persistent thermal energy emitted at Yasur with some variation from mid-May 2019 to May 2020. There was a reduction in detected energy after January. Courtesy of MIROVA.

Geologic Background. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); 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); Planet Labs, Inc. (URL: https://www.planet.com/); 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/); Justin Noonan (URL: https://www.justinnoonan.com/, Instagram: https://www.instagram.com/justinnoonan_/); Doro Adventures (Twitter: https://twitter.com/DoroAdventures, URL: http://doroadventures.com/).


Cleveland (United States) — March 2020 Citation iconCite this Report

Cleveland

United States

52.825°N, 169.944°W; summit elev. 1730 m

All times are local (unless otherwise noted)


Intermittent thermal anomalies and lava dome subsidence, February 2019-January 2020

Cleveland is a stratovolcano located in the western portion of Chuginadak Island, a remote island part of the east central Aleutians. Common volcanism has included small lava flows, explosions, and ash clouds. Intermittent lava dome growth, small ash explosions, and thermal anomalies have characterized more recent activity (BGVN 44:02). For this reporting period during February 2019-January 2020, activity largely consisted of gas-and-steam emissions and intermittent thermal anomalies within the summit crater. The primary source of information comes from the Alaska Volcano Observatory (AVO) and various satellite data.

Low levels of unrest occurred intermittently throughout this reporting period with gas-and-steam emissions and thermal anomalies as the dominant type of activity (figures 30 and 31). An explosion on 9 January 2019 was followed by lava dome growth observed during 12-16 January. Suomi NPP/VIIRS sensor data showed two hotspots on 8 and 14 February 2019, though there was no evidence of lava within the summit crater at that time. According to satellite imagery from AVO, the lava dome was slowly subsiding during February into early March. Elevated surface temperatures were detected on 17 and 24 March in conjunction with degassing; another gas-and-steam plume was observed rising from the summit on 30 March. Thermal anomalies were again seen on 15 and 28 April using Suomi NPP/VIIRS sensor data. Intermittent gas-and-steam emissions continued as the number of detected thermal anomalies slightly increased during the next month, occurring on 1, 7, 15, 18, and 23 May. A gas-and-steam plume was observed on 9 May.

Figure (see Caption) Figure 30. The MIROVA graph of thermal activity (log radiative power) at Cleveland during 4 February 2019 through January 2020 shows increased thermal anomalies between mid-April to late November 2019. Courtesy of MIROVA.
Figure (see Caption) Figure 31. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) confirmed intermittent thermal signatures occurring in the summit crater during March 2019 through October 2019. Some gas-and-steam plumes were observed accompanying the thermal anomaly, as seen on 17 March 2019 and 8 May 2019. Courtesy of Sentinel Hub Playground.

There were 10 thermal anomalies observed in June, and 11 each in July and August. Typical mild degassing was visible when photographed on 9 August (figure 32). On 14 August, seismicity increased, which included a swarm of a dozen local earthquakes. The lava dome emplaced in January was clearly visible in satellite imagery (figure 33). The number of thermal anomalies decreased the next month, occurring on 10, 21, and 25 September. During this month, a gas-and-steam plume was observed in a webcam image on 6, 8, 20, and 25 September. On 3-6, 10, and 21 October elevated surface temperatures were recorded as well as small gas-and-steam plumes on 4, 7, 13, and 20-25 October.

Figure (see Caption) Figure 32. Photograph of Cleveland showing mild degassing from the summit vent taken on 9 August 2019. Photo by Max Kaufman; courtesy of AVO/USGS.
Figure (see Caption) Figure 33. Satellite image of Cleveland showing faint gas-and-steam emissions rising from the summit crater. High-resolution image taken on 17 August 2019 showing the lava dome from January 2019 inside the crater (dark ring). Image created by Hannah Dietterich; courtesy of AVO/USGS and DigitalGlobe.

Four thermal anomalies were detected on 3, 6, and 8-9 November. According to a VONA report from AVO on 8 November, satellite data suggested possible slow lava effusion in the summit crater; however, by the 15th no evidence of eruptive activity had been seen in any data sources. Another thermal anomaly was observed on 14 January 2020. Gas-and-steam emissions observed in webcam images continued intermittently.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows intermittent weak thermal anomalies within 5 km of the crater summit during mid-April through November 2019 with a larger cluster of activity in early June, late July and early October (figure 30). Thermal satellite imagery from Sentinel-2 also detected weak thermal anomalies within the summit crater throughout the reporting period, occasionally accompanied by gas-and-steam plumes (figure 31).

Geologic Background. The beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Joined to the rest of Chuginadak Island by a low isthmus, Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.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); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).

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Bulletin of the Global Volcanism Network - Volume 27, Number 05 (May 2002)

Managing Editor: Richard Wunderman

Colima (Mexico)

New lava flows; change in deformation during 15-20 May 2002 prompts evacuation

Dieng Volcanic Complex (Indonesia)

Increase in seismicity and plume emission beginning in April 2002

Galeras (Colombia)

Tremor, earthquakes, and occasional rockfalls through early 2002

Kanlaon (Philippines)

Increased seismicity during March-April 2002

Karangetang (Indonesia)

Small explosions and increased seismicity during April 2002

Kilauea (United States)

New lava flows during early May burn over 1,000 hectares of forest

Manam (Papua New Guinea)

Strombolian eruption on 20 May followed by lower-level activity

Monowai (New Zealand)

Strong T-waves during May 2002 indicate explosive activity

Nyiragongo (DR Congo)

Increased tremor during April-May; lava fountain observed in crater

Ruiz, Nevado del (Colombia)

Largest earthquake swarm since 1985 occurs during June 2002

Santa Maria (Guatemala)

Active lava flow front continues to generate ash plumes through early 2002

Sheveluch (Russia)

Growing lava dome, seismicity, and 3-km ash-and-gas plumes through mid-June

Shishaldin (United States)

Seismicity increases briefly during mid-May 2002



Colima (Mexico) — May 2002 Citation iconCite this Report

Colima

Mexico

19.514°N, 103.62°W; summit elev. 3850 m

All times are local (unless otherwise noted)


New lava flows; change in deformation during 15-20 May 2002 prompts evacuation

New lava flows began on 14 February 2002 on the SW flank of the central crater of Colima. The lava flows were produced by the dome that had filled the crater through early February (BGVN 27:02). Figures 50 and 51 show the dome at the end of May 2002. Two main groups of lava flows were formed; the first was a flow with a maximum length of 1,400 m, and the second included two small branches with maximum lengths of 500 m (table 11). The total volume of lava reached 3,435,000 m3. Emplacement of the lava flows was accompanied by numerous incandescent rockfalls on the SW, S, and W slopes of the volcano along the ravines of La Lumbre, El Zarco, Cordoban, and San Antonio beginning on the evening of 4 February. The first pyroclastic flows of 1-2 km length were recorded on 9 February on the S and SW flanks, prior to the onset of the new lava flows. The number and intensity of the rockfalls and pyroclastic flows increased rapidly and from 15 February were recorded at a level of 200-300 per day through April (figure 52). Rockfalls reached a distance of 1-3 km from the crater.

Figure (see Caption) Figure 50. A S-looking view of the summit of Colima taken on 23 May 2002 showing the emerging dome dominating the summit area. Lava flows appeared to emerge from the dome. Courtesy of Secretaria de Comunicaciones y Transportes del estado de Colima.
Figure (see Caption) Figure 51. A sketch of the new lava flows on the W and SW slope of Colima at the end of May 2002. Courtesy of Observatorio Vulcanológico de la Universidad de Colima.

Table 11. Characteristics of the 2002 lava flows 1 and 2 of Colima (see figure 2). "--" indicates that the information was not reported. Courtesy of Observatorio Vulcanológico de la Universidad de Colima.

Date Flow 1 Length Flow 1 Volume Flow 1 Effusion rate Flow 2 Length Flow 2 Volume Flow 2 Effusion rate
22 Feb 2002 200 m 720,000 m3 6-9 m3/s -- -- --
22 Mar 2002 550 m 1,650,000 m3 0.6 m3/s -- -- --
26 Apr 2002 1,000 m 1,785,000 m3 0.07 m3/s 50 m 98,000 m3 --
30 May 2002 1,400 m 2,310,000 m3 0.2 m3/s 500 m 1,125,000 m3 0.3 m3/s
Figure (see Caption) Figure 52. Daily variations of the number of rockfalls and pyroclastic flows recorded by seismic station Soma at a distance of 1.7 km from the crater of Colima. Courtesy of Observatorio Vulcanológico de la Universidad de Colima.

The Washington VAAC reported that ash and steam were observed on 8 March extending E from Colima at 4.3-5.2 km altitude. The emission was too small to be visible on satellite imagery, although a faint hotspot was seen in shortwave imagery. On 25 March at 1040 a steam-and-ash emission rose to ~5-6 km altitude and drifted E.

On 25 March volcanic tremor began to occur during 1- to 3-hour intervals, and since 8 April tremor was observed daily for intervals from a few minutes to 10 hours. Degassing occurred starting on 25 April as very low-magnitude explosions. In many cases, the intervals of volcanic tremor were accompanied by an explosive event. The numerous but very small-amplitude tremor and explosive events occurred simultaneously and accompanied continuous records of rockfalls and pyroclastic flows.

Deformation of the volcanic edifice that was observed by an inclinometer network showed a sharp change in behavior on 15 May. On 20 May deformation became stable. A preventive evacuation of the village of La Yerbabuena occurred during 18 May-4 June. The 6.5-km-radius zone of exclusion around Colima remained in effect, with other restricted access continuing out to a radius of 11.5 km.

Geologic Background. The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the high point of the complex) on the north and the historically active Volcán de Colima at the south. A group of late-Pleistocene cinder cones is located on the floor of the Colima graben west and east of the complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, producing thick debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions have destroyed the summit (most recently in 1913) and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Information Contacts: Observatorio Vulcanológico de la Universidad de Colima, Ave. 25 de Julio 965, Colima 28045, Colima, México; Washington Volcanic Ash Advisory Center (VAAC), NOAA/NESDIS Satellite Analysis Branch, Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/).


Dieng Volcanic Complex (Indonesia) — May 2002 Citation iconCite this Report

Dieng Volcanic Complex

Indonesia

7.2°S, 109.879°E; summit elev. 2565 m

All times are local (unless otherwise noted)


Increase in seismicity and plume emission beginning in April 2002

The last reported activity at Dieng occurred during late June and early July 1998, when three M ~2 earthquakes were felt and a white steam plume was emitted from Sileri crater to a height of 50 m (BGVN 23:08). During April 2002, the Volcanological Survey of Indonesia (VSI) reported that activity at Dieng increased. Beginning on 19 April the number of deep and shallow volcanic earthquakes increased (table 1), and a white plume of variable thickness rose 25-50 m above Sileri crater. The temperatures of fumaroles in various craters were 50-95°C (table 2). Dieng remained at Alert Level 2 through at least 26 May 2002.

Table 1. Earthquakes recorded at Dieng during 15 April through 19 May 2002. Courtesy VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Far Tectonic Local Tectonic
15 Apr-21 Apr 2002 14 10 1 0
22 Apr-28 Apr 2002 75 121 1 1
29 Apr-05 May 2002 18 64 0 0
06 May-12 May 2002 6 82 0 0
13 May-19 May 2002 2 24 1 0

Table 2. Temperatures of various craters of Dieng during 15 April through 12 May 2002. "--" indicates that the information was not reported. Courtesy VSI.

Date Sikidang Sibateng Sileri Condrodimuko Sinila Siglagah Bitingan Pagerkandang
15 Apr-21 Apr 2002 90-94°C 91-94°C 68°C 90-93°C 70-74°C 90-94°C -- --
22 Apr-28 Apr 2002 91-95°C 92-94°C 69°C -- 76-75°C -- 50-57°C 90-94°C
29 Apr-05 May 2002 -- -- -- 90-93°C 74-75°C -- -- --
06 May-12 May 2002 -- -- 69°C -- -- -- 50-56°C --

Geologic Background. The Dieng plateau in the highlands of central Java is renowned both for the variety of its volcanic scenery and as a sacred area housing Java's oldest Hindu temples, dating back to the 9th century CE. The Dieng volcanic complex consists of two or more stratovolcanoes and more than 20 small craters and cones of Pleistocene-to-Holocene age over a 6 x 14 km area. Prahu stratovolcano was truncated by a large Pleistocene caldera, which was subsequently filled by a series of dissected to youthful cones, lava domes, and craters, many containing lakes. Lava flows cover much of the plateau, but have not occurred in historical time, when activity has been restricted to minor phreatic eruptions. Toxic gas emissions are a hazard at several craters and have caused fatalities. The abundant thermal features and high heat flow make Dieng a major geothermal prospect.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).


Galeras (Colombia) — May 2002 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Tremor, earthquakes, and occasional rockfalls through early 2002

The Observatorio Vulcanológico y Sismológico de Pasto (OVSP) reported that during 1 January-31 March 2002, volcanic activity at Galeras was at a low level, similar to that reported in recent years. During the report period, a total of 43 volcano-tectonic events were recorded with a total seismic energy of 1.25 x 1015 erg, based on their durations. The majority of these events were located toward the NE of the volcanic edifice and W of the active crater (figure 99).

Figure (see Caption) Figure 99. Epicenters of volcano-tectonic earthquakes that occurred in the Galeras region during January-March 2002. Courtesy OVSP.

On 7 January a small earthquake swarm, including eight small-magnitude events, was located beneath the western part of the active crater. Two earthquakes were felt in Pasto and Jenoy. The first occurred on 12 March at 0128 with a local magnitude of 2.4; it was located 5 km NE of the active crater and 8 km below the summit. The second occurred on 14 March at 1753 with a local magnitude of 3.1; it was located 6 km NE of the active crater and at a depth of 8 km below the summit.

Three long-period events and 37 tremor episodes with a total energy of 3.08 x 1013 erg were registered. Some of the tremor episodes were of harmonic type, with dominant frequencies between 2.2 and 2.5 Hz (figure 100), with the source located in the crater region at shallow levels.

Figure (see Caption) Figure 100. Digital record of a tremor episode at Galeras on 5 January 2002 at broad-band station Crater (1.6 km S of the active crater) and its normalized spectrum. Courtesy OVSP.

On 12 January a tornillo event was registered (figure 101) with a spectrum that showed frequency picks at 2.4, 6.9, and 8.9 Hz. The energy of this event, based on its duration, was 3.04 x 1013 erg.

Figure (see Caption) Figure 101. Digital record of tornillo event registered on 12 January 2002 at broad-band station Anganoy (0.9 km E of the active crater) and its normalized spectrum. Courtesy OVSP.

On 5 January 2002 three seismic events occurred that were associated with rockfalls that resulted from the physical instability of the volcanic edifice in the W sector, rains, and earthquakes near to that unstable region. Similar activity had occurred on 6 December 2001.

Geologic Background. Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Long-term extensive hydrothermal alteration has contributed to large-scale edifice collapse on at least three occasions, producing debris avalanches that swept to the west and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid-Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.

Information Contacts: Patricia Ponce, Observatorio Vulcanológico y Sismológico de Pasto (OVSP), INGEOMINAS, Carrera 31, 18-07 Parque Infantil, P.O. Box 1795, Pasto, Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html).


Kanlaon (Philippines) — May 2002 Citation iconCite this Report

Kanlaon

Philippines

10.412°N, 123.132°E; summit elev. 2435 m

All times are local (unless otherwise noted)


Increased seismicity during March-April 2002

In February 2002, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) reported sustained seismic activity that might lead to an explosion at Canlaon. PHIVOLCS noted an increase in seismic activity in Canlaon after five weeks of continuous and sustained earthquakes. During 27-28 February the Guintubdan seismic station detected at least 67 earthquakes, which was above the background seismic level of a few earthquakes per day. PHIVOLCS monitored both high- and low-frequency volcanic earthquakes at Canlaon; high-frequency events dominated, indicating that the volcano was undergoing possible magma intrusion. PHIVOLCS noted that such intrusions result in many high-frequency events intermixed with a few low-frequency earthquakes. The epicenters were detected over a large area, which could mean that a large body of magma was developing beneath the volcano. At this stage of activity, a major eruption was not anticipated because the earthquakes could also have been caused by rockslides along the volcano's faults.

On 27 February trekking was banned within the 4-km danger zone after PHIVOLCS declared Alert Level 1 (the volcano is in a restive state, but trekking or any human activity could be dangerous within the danger zone). PHIVOLCS issued a statement that the area near the volcano should be avoided because of "possible sudden phreatic or steam-driven explosions." In the meantime, monitoring instruments were to be installed at the Guintubdan seismic station, located near the crater, to monitor the volcano's seismic activities.

On 15 April PHIVOLCS concluded that the episodes of apparent seismic unrest at Canlaon could be traced to the Guintubdan and Mambucal areas. The Guintubdan area has been the site of earthquake swarms in the past, and these high-frequency events may be related to local fault movement and/or intrusions. On the other hand, earthquakes in the Mambucal area occurred when the Philippine National Oil Company (PNOC) pumped water into its geothermal wells and induced micro-earthquake fracturing at depth. In both instances, PHIVOLCS noted that significant earthquakes only occurred over a broad area N of the active crater of Canlaon, without distinct clustering or migration towards the crater. These observations suggest that earthquake activity, for now, is not related to a reactivation of the Canlaon magma system. With the return of seismic activity to baseline levels and having identified non-volcanic seismic sources in this area, PHIVOLCS lowered the alert status of Canlaon from Alert Level 1 to Alert level 0. However, visitors to the summit area were strongly urged to avoid entering the crater because sudden explosions may occur without warning. For the same reason, PHIVOLCS reminded the public that no permanent human activity is permitted within 4 km of the crater.

Geologic Background. Kanlaon volcano (also spelled Canlaon), the most active of the central Philippines, forms the highest point on the island of Negros. The massive andesitic stratovolcano is dotted with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km SW from Kanlaon. The summit contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller, but higher, historically active vent, Lugud crater, to the south. Historical eruptions, recorded since 1866, have typically consisted of phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, 5th & 6th Floors, Hizon building, 29 Quezon Avenue, Quezon City, Philippines.


Karangetang (Indonesia) — May 2002 Citation iconCite this Report

Karangetang

Indonesia

2.781°N, 125.407°E; summit elev. 1797 m

All times are local (unless otherwise noted)


Small explosions and increased seismicity during April 2002

During 25 February through at least 16 June 2002, seismicity at Karangetang was dominated by shallow volcanic (B-type) and tectonic earthquakes (table 4). Thick, white, medium-pressure plumes were typically emitted from the main crater (S) and reached 50-500 m above the crater rim. During late May through at least 16 June, a thin-medium white plume was emitted from crater II (N) and reached 150-200 m above the crater rim. During most of the report period a red reflection was observed around the summit at night, rising 10-75 m.

Table 4. Earthquakes recorded at Karangetang during 25 February through 16 June 2002. The Alert Level remained at 2 throughout this period. Courtesy VSI.

Date Deep volcanic (A-type) Shallow volcanic (B-type) Multiphase Tectonic
25 Feb-02 Mar 2002 52 5 6 62
03 Mar-10 Mar 2002 44 20 2 201
11 Mar-17 Mar 2002 29 8 9 100
18 Mar-24 Mar 2002 15 8 6 83
25 Mar-31 Mar 2002 20 9 2 112
01 Apr-07 Apr 2002 27 3 2 71
08 Apr-14 Apr 2002 17 64 -- 82
15 Apr-21 Apr 2002 26 74 -- 147
22 Apr-28 Apr 2002 17 61 2 146
29 Apr-05 May 2002 28 99 6 139
06 May-12 May 2002 22 70 0 132
13 May-19 May 2002 8 77 1 112
20 May-26 May 2002 22 93 6 146
27 May-02 Jun 2002 18 1228 4 113
03 Jun-09 Jun 2002 13 119 3 75
10 Jun-16 Jun 2002 12 62 1 45

Several eruptions occurred during the report period. An eruption on 5 March at 1344 emitted ash that reached 1.5 km above the summit. Ash fell on the NE flank and a lava avalanche also occurred. During the week of 3-10 March, 1 earthquake was felt. On 23 March 2002 at 1115 a thundering sound was heard from main crater, followed by a lava avalanche that flowed down to Kahetang and Batu Awang rivers. A thundering sound was heard beginning at 1615 on 28 March until 2007 on 29 March. No lava avalanches occurred during this time, but 3 earthquakes were felt during the last week of March. A medium explosion on 7 April at 2115 emitted thick gray ash to ~400 m above the crater rim.

The number of deep and shallow volcanic earthquakes increased during April (table 4). An ash explosion on 12 May at 1116 emitted ash that reached 750 m above the crater before falling to the sea on the E side. The explosion was followed by a lava avalanche that flowed ~500 m down the Batu Awang and Kahetang rivers. An explosion on 26 May at 1747 emitted white-gray ash that reached 300 m above the crater rim before falling to the sea on the W side. During 3-9 and 10-16 June, 2 and 5 small explosions occurred per week, respectively. Karangetang remained at Alert Level 2 throughout the report period.

Geologic Background. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi island. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).


Kilauea (United States) — May 2002 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


New lava flows during early May burn over 1,000 hectares of forest

Surface activity and seismicity continued at Kilauea during mid-April through early June 2002. Volcanic tremor was moderate at times and was accompanied by frequent long-period (LP) earthquakes during mid-May. Lava flows erupted during January and April 2002 (figure 154) were fed by several rootless shields located directly above the lava tube at elevations between 2,200 and 2,050 feet. Three significant lava flows began during mid-April and early May (figure 154) and had not yet terminated by the end of the report period. Two of these flows originated in the rootless shield area, and the third broke out from the lava tube system to the SW of Pu`u `O`o crater. The two flows from the rootless shields were the Boundary flow, along the edge of the national park, and the Royal Gardens flow, which approached the uppermost part of Royal Gardens subdivision on 21 May. The Royal Gardens flow entered the subdivision during the night of 22-23 May. From near Pu`u `O`o, the 12 May flow passed along the W side of the flow field and into the forest. The most recent ocean entries at East Kupapa'u and Kamoamoa stopped in mid-January and late January, respectively.

Figure (see Caption) Figure 154. A map showing lava flows erupted during the 1983-present activity of Pu'u 'O'o and Kupaianaha craters at Kilauea. Flows during 1-21 May (shown in black) originated from two sources, the area of the rootless shields and an area just SW of Pu'u 'O'o. Courtesy HVO.

Geophysical activity. Seismicity was at background levels and tiltmeters showed no significant activity until 23 April, when 10.1 µrad of rapid inflation was recorded at Pu`u `O`o crater. The inflation was inferred to be shallow because other tiltmeters recorded less inflation at greater distance from Pu`u `O`o. The summit showed little accompanying tilt change for this event.

Seismicity and tilt returned to normal levels until 28 April when Pu`u `O`o deflated rapidly and shortly thereafter began again to inflate slowly. Major deflation began on the morning of 12 May, and by 13 May Pu`u `O`o had deflated 18 µrad. Tremor increased to levels above those prior to the deflation and was accompanied by small LP earthquakes at the summit and Pu`u `O`o. Seismicity continued to increase beneath the caldera with one small LP earthquake every ~30 seconds. This swarm ended abruptly on 22 May, and by 24 May seismicity returned to normal background levels with tilt flat or fluctuating slightly. During 5-10 June swarms of frequent LP earthquakes occurred in the caldera accompanied by moderate tremor below Pu`u `O`o, which continued through 15 June.

Lava flows. Observers reported incandescence on 18 April in the East Pond vent and South Wall complex of the Pu`u `O`o crater. Partss of the rootless shield area were also glowing brightly. On a 24 April overflight observers reported a bright glow from the Puka Nui area and a small lava flow from the same area traveling SE. On the same day a lava flow had moved onto the floor of the Pu`u `O`o crater. By 2 May most activity in Pu`u `O`o had subsided to low incandescence.

Around 30 April a bifurcating lava flow originated in the SE corner of the rootless shield; it formed two of three significant flows during May; one occurred along the boundary of Volcano National Park and the other moved towards the Royal Gardens subdivision.

Incandescence waned but the rootless shield flows continued until 12 May when the two large surface flows broke out from the upper tube system near the SW base of Pu`u `O`o. On 12 May at about 1100 a video recording showed that the flows were ~3 m wide and extended an unknown distance downslope. During mid-May activity of the flow along the Park boundary fluctuated on the Pulama pali slope, but all three flows continued. By the end of the report period the 12 May flow was 800-1,000 m from the end of the Chain of Craters road after cascading down part of the 1995 Jason flow (BGVN 20:04). The Royal Gardens flow had advanced into the subdivision and the boundary flow showed dim incandescence and continued its movement along the park boundary.

The 12 May flow ignited fires as it traveled through the wooded areas above the Pulama pali. The fires burned over 1,000 hectares through 1 June and prompted the closure of the Chain of Craters road. By 10 June the fires were 65% contained and the road was reopened for nighttime viewing. No ocean entries occurred during the report period.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/).


Manam (Papua New Guinea) — May 2002 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Strombolian eruption on 20 May followed by lower-level activity

Mild eruptive activity began from South Crater on 13 January 2002. Weak gray-brown ash clouds were emitted and fine, light ashfall was reported. Weak, deep, roaring and rumbling noises accompanied occasional explosions and fluctuating incandescence (BGVN 27:03).

The Rabaul Volcano Observatory (RVO) reported that during March 2002 clouds obscured the view, but the vent produced weak-to-loud roaring and rumbling noises at intervals of 5-10 minutes on some days and about an hour on other days. The average interval was about 20-30 minutes. Explosions occurred on 15, 17, 21, 22 and 27 March. Explosions produced projections of dark brown ash clouds that were visible above the cloud cover. Fine ashfall was observed on the SE, and occasionally on the NW, parts of the island on many days of the month. Most ashfall occurred during 14-31 March, coinciding with the period of more numerous and vigorous explosions. Another notable observation was the sound of cascading boulders and rock fragments into the SE valley. These sounds were usually heard following explosions or loud roaring noises. Incandescence was observed on most nights of the month. During 1-13 March, generally steady incandescence varied between a dull and a bright, steady glow, and during 14-31 March the glow was marginally brighter. Occasionally (4, 17, and 31 March), projections of red incandescent lava fragments were observed. Main Crater continued to release only weak-to-moderate volumes of white vapor during periods of visibility. No instrumental (including seismicity) recording was done in March.

A moderate-sized Strombolian eruption occurred on 20 May. A pilot reported an ash plume at a maximum height of ~9 km on 20 May at 0500. At 0945 on the same day an eruption cloud was visible on satellite imagery extending SW. The Rabaul Volcano Observatory reported that a continuous eruption occurred until about 1400 on 20 May. After that, activity consisted of forceful ash emissions in moderate volumes. The decline in activity led to the reduction in Alert Level from 2 ("eruption expected within weeks to months") to 1 ("non-threatening, background level"). According to the Darwin VAAC, the ash cloud produced from the 20 May eruption was no longer visible on satellite imagery by 22 May at 1515. People were reminded to be cautious when near the valleys SE and SW of the volcano.

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: Ima Itikarai, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea; Darwin VAAC, Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina Northern Territory 0811 Australia (URL: http://www.bom.gov.au/info/vaac/).


Monowai (New Zealand) — May 2002 Citation iconCite this Report

Monowai

New Zealand

25.887°S, 177.188°W; summit elev. -132 m

All times are local (unless otherwise noted)


Strong T-waves during May 2002 indicate explosive activity

The last reported activity at Monowai occurred during June 1999 when a strong acoustic crisis was recorded (BGVN 24:06). During May 2002, strong T-waves coming from Monowai were detected by the French Polynesian Seismic Network. The signal began at 1522 on 24 May and suggested explosive activity. Several small events were detected during the next two hours. No further activity was recorded following the event.

General Reference. Davey, F.J., 1980, The Monowai Seamount: an active submarine volcanic centre on the Tonga-Kermadec Ridge (Note): New Zealand Journal of Geology and Geophysics, v. 23, p. 533-536.

Geologic Background. Monowai, also known as Orion seamount, rises to within 100 m of the sea surface about halfway between the Kermadec and Tonga island groups. The volcano lies at the southern end of the Tonga Ridge and is slightly offset from the Kermadec volcanoes. Small parasitic cones occur on the N and W flanks of the basaltic submarine volcano, which rises from a depth of about 1500 m and was named for one of the New Zealand Navy bathymetric survey ships that documented its morphology. A large 8.5 x 11 km wide submarine caldera with a depth of more than 1500 m lies to the NNE. Numerous eruptions from Monowai have been detected from submarine acoustic signals since it was first recognized as a volcano in 1977. A shoal that had been reported in 1944 may have been a pumice raft or water disturbance due to degassing. Surface observations have included water discoloration, vigorous gas bubbling, and areas of upwelling water, sometimes accompanied by rumbling noises.

Information Contacts: Dominique Reymond, Geophysical Laboratory, CEA/DASE, PO Box 640, Papeete, Tahiti, French Polynesia.


Nyiragongo (DR Congo) — May 2002 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Increased tremor during April-May; lava fountain observed in crater

During the catastrophic eruption of Nyiragongo on 17 January 2002 all lava drained from the summit, leaving an empty crater more than 700 m deep. Harmonic tremor that was registered at two seismic stations on Nyiragongo's S flank beginning in late April continued to increase irregularly in amplitude through at least May 2002. Anomalous clouds were noticed above the crater on two occasions since 1 May, but no glow was noted at night. A brief flight over the summit during daylight on 14 May failed to disclose eruptive activity. That day, increasing tremor amplitude (including many hours of banded tremor with a one-hour period), suggested that magma was moving within the summit area.

During 17-18 May an expedition traveled to the summit to look for any possible extrusive activity, and a small lava fountain was observed on the floor of the crater. It vented along the same NW-SE-trending fissure that apparently drained the crater in January. The lone fountain ejected incandescent spatter to a height of ~12 m and built a low spatter rampart, but no lake formed. Several small incandescent vents on the rubble-filled crater floor ejected hot gases. This observation indicated that magma had risen high within the edifice. A long period of extrusive activity could prevail in the years ahead, assuming the typical pattern of development in Nyiragongo's historical eruptions, and this was interpreted as no cause for immediate concerns. A similar pattern followed the January 1977 eruption, when in June 1982 activity resumed in Nyiragongo's main crater, beginning with a lava fountain that fed a new lava lake in less than two weeks. It remained active until September 1982.

Geologic Background. One of Africa's most notable volcanoes, Nyiragongo contained a lava lake in its deep summit crater that was active for half a century before draining catastrophically through its outer flanks in 1977. The steep slopes of a stratovolcano contrast to the low profile of its neighboring shield volcano, Nyamuragira. Benches in the steep-walled, 1.2-km-wide summit crater mark levels of former lava lakes, which have been observed since the late-19th century. Two older stratovolcanoes, Baruta and Shaheru, are partially overlapped by Nyiragongo on the north and south. About 100 parasitic cones are located primarily along radial fissures south of Shaheru, east of the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by voluminous lava flows that extend long distances down the flanks, which is characterized by the eruption of foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities, as did lava flows that inundated portions of the major city of Goma in January 2002.

Information Contacts: Celestin Kasereka, Jean-Pierre Bajope, and Mathieu Yalire, Goma Volcano Observatory, Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, Zaire; Jacques Durieux, Dario Tedesco, and Jack Lockwood, Groupe d'Etude des Volcans Actifs, 6, rue des Razes, 69320 Feyzin, France.


Nevado del Ruiz (Colombia) — May 2002 Citation iconCite this Report

Nevado del Ruiz

Colombia

4.892°N, 75.324°W; summit elev. 5279 m

All times are local (unless otherwise noted)


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).

Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

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.


Santa Maria (Guatemala) — May 2002 Citation iconCite this Report

Santa Maria

Guatemala

14.757°N, 91.552°W; summit elev. 3745 m

All times are local (unless otherwise noted)


Active lava flow front continues to generate ash plumes through early 2002

During early 2002 the block lava flow that began to extend S from the Caliente vent of Santa María during July 1999 (BGVN 25:06) remained active. As of 19 January 2002 the active flow front was in approximately the same location as during January 2001, ~3.4 km from the vent. The active flow front was ~40 m high and extended over an older, now inactive unit. This inactive unit extends 420 m farther down the narrow ravine of the Río Nimá II (figure 31). The flow front was ~315 m wide and was extremely active, being the source of frequent collapse events generating ash plumes that rose ten's to hundred's of meters.

Figure (see Caption) Figure 31. Map of the dome of Santa María obtained using a 19 January 2002 Landsat 7 Enhanced Thematic Mapper Plus image. The area shown in black is the extent of the main block lava flow field, along the Río Nimá II ravine, including active and inactive portions. "PF" marks the course of pyroclastic flows from the block-lava flow medial section, and "F" denotes valley fill observed during ground-based observations of this medial section. Courtesy Otoniel Matías, Gustavo Chigna, Yvonne Branan, Lizzette Rodriguez, Gregg Bluth, Matt Watson, Elly Bunzendahl, Janelle Byman, and William I. Rose.

During a 7.5-hour-long observation period on 10 January, flow front collapses generated ash plumes that reached altitudes sufficient to be observed from 5 km away on 63 occasions. The medial section of the block-lava flow displayed well-formed levees, defining a ~100 m wide channel with typical outer levee heights of 40-75 m. Maximum levee heights of 95-110 m (measured using a laser range finder and using shadows on a Landsat 7 ETM+ image) occurred in the vicinity of the January 2000 flow front location (figure 31). Within the channel, the flow surface was 20-30 m below the levees. The channelized section fed a 300-400 m-wide zone of dispersed flow that extended from the channel mouth to the flow front. This zone consisted of multiple lobes of inactive units, with a central active stream. The distal section was being resurfaced by a new flow lobe. This lobe began extending from the vent around 29 December 2001 and by 19 January 2002 it had extended ~780 m from the vent (advancing at a rate of 65 m per day). The extrusion of this new unit was coincident with a significant explosive/collapse event that generated a small pyroclastic flow down the E flank of the Caliente vent.

As in January 2000 (BGVN, 25:06), the Caliente vent was filled to the brim and the vent area was marked by a low dome-like feature. During 0710-1436 on 10 January, 38 ash eruptions occurred (~5 per hour). Eruptions typically occurred every 30 minutes. However, 10 of these events were paired consisting of two or three emissions separated by 1-5 minutes. Observations from the Santa Maria summit allowed measurements of a ring-shaped (diameter 143 ± 20 m) vent defined by ash-and-gas emissions in the early seconds of brief explosions (figure 32). SO2 flux measurements of the Caliente vent emissions gave large ranges of 15-180 metric tons/day. The larger emission rates are similar to those for the previous two years.

Figure (see Caption) Figure 32. View of the Caliente Vent (2,500 m elevation) as seen from Santa María summit (3,772 m elevation) at 0801 on 11 January 2002. The image is part of a digital video sequence at the beginning of an explosive event. The ring-like feature scales to ~ 140 m in diameter. Courtesy Otoniel Matías, Gustavo Chigna, Yvonne Branan, Lizzette Rodriguez, Gregg Bluth, Matt Watson, Elly Bunzendahl, Janelle Byman, and William I. Rose.

A news article reported that staff from Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH) stated that volcanic activity increased at the Santiaguito dome complex beginning on 11 March 2002. Until at least 14 March near-constant explosions opened fractures on the volcano and emitted ash. Ash rose to 600-900 m above the volcano and fell in the towns of Retalhuleu (25 km SSE of the volcano) and San Marcos, and towards the Mexican border.

Based on information from INSIVUMEH, the Washington VAAC reported that light ash fell near Santa Maria's summit on 13 May and an ash cloud was visible on satellite imagery drifting SW during the morning and more towards the W later in the day. The thickest ash was located very close to the summit, with light ash extending SW.

Geologic Background. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Information Contacts: Andy Harris, Luke Flynn, and Mark Davies, HIGP/SOEST, University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Otoniel Matías and Gustavo Chigna, INSIVUMEH, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala; Yvonne Branan, Lizzette Rodriguez, Gregg Bluth, Matt Watson, Elly Bunzendahl, Janelle Byman, William I. Rose, Department of Geological Engineering and Sciences, Michigan Technological University, Houghton, MI 49931, USA; Simon Carn UMBC, Baltimore, MD USA; Washington VAAC, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/); Prensa Libre (URL: http://www.prensalibre.com/).


Sheveluch (Russia) — May 2002 Citation iconCite this Report

Sheveluch

Russia

56.653°N, 161.36°E; summit elev. 3283 m

All times are local (unless otherwise noted)


Growing lava dome, seismicity, and 3-km ash-and-gas plumes through mid-June

During April through mid-June 2002, mild eruptive activity continued at Shiveluch. A lava dome continued to grow in the active crater, gas-and-steam and ash-and-gas emissions occurred, and seismicity remained above background levels. Plumes reached up to 3 km above the lava dome (table 1). Earthquakes reached magnitudes up to 2.4 at depths of 0-10 km. Many other local shallow seismic signals occurred that possibly indicated weak gas-ash explosions and avalanches. Episodes of weak spasmodic volcanic tremor were also registered. Thermal anomalies were visible on AVHRR satellite imagery throughout the report period (table 2). No ash was detected in any image.

Table 1. Plumes reported at Shiveluch during 30 March through 14 June 2002. Courtesy KVERT.

Date Time Plume type Height above dome Comment on plume
30 Mar 2002 2042 ash and gas 1.5 km --
31 Mar 2002 -- gas and steam 300-700 m --
31 Mar 2002 1310 ash -- view obscured by clouds
02 Apr 2002 -- gas and steam 300-700 m --
10 Apr 2002 0900 ash and gas 1 km --
15 Apr 2002 1906 ash and gas 1 km --
19 Apr 2002 -- gas and steam 1.0-1.5 km --
20 Apr 2002 ~1240 ash clouds 800 m --
21 Apr 2002 -- gas and steam 1.0-1.5 km --
21 Apr-23 Apr 2002 -- gas and steam 200-500 m --
25 Apr 2002 -- gas and steam 200-500 m --
26 Apr 2002 -- gas and steam 100 m --
29 Apr 2002 -- gas and steam 800 m extended 10 km E
30 Apr-01 May 2002 -- gas 200-600 m --
01 May 2002 morning transparent gray, dark blue -- extended 40 km S
01 May 2002 evening transparent gray, dark blue -- extended 5 km NW
05 May 2002 0800 gas; transparent gray-blue 100 m; 5 km SE --
05 May 2002 0945 ash and gas 1.5 km --
05 May 2002 -- gas and steam 200-800 m --
08 May-09 May 2002 -- gas and steam 200-800 m --
08 May 2002 -- gas, steam, and ash 200-800 m --
10 May 2002 -- gas, steam, and ash 300-500 m --
11 May 2002 -- gas and steam 1.0-1.6 km --
12 May 2002 morning gas, little ash 50 m --
13 May-15 May 2002 -- gas and steam 1.0-1.6 km --
16 May 2002 -- gas, steam, and ash 300-500 m --
17 May 2002 2100 gas and steam, little ash 800 m extended 10 km SE
21 May 2002 1707 ash and gas 800 m --
21 May 2002 evening gas and steam, possible little ash 600-800 m --
23 May 2002 evening gas and steam, possible little ash 600-800 m --
24 May 2002 -- gas and steam 1.2-1.5 km extended 5 km W
25 May 2002 -- gas and steam 300 m --
27 May 2002 -- gas and steam 1.2-1.5 km extended 5 km W
31 May 2002 evening gas and steam 1.3 km extended 5 km E
31 May 2002 -- steam -- extended 50 km SW
31 May 2002 -- gas and steam 900-2,500 m extended 5 km E
01 Jun 2002 -- gas and steam 200 m --
01 Jun 2002 1616 ash and gas 3 km --
01 Jun 2002 -- small gas and steam 1.3 km --
03 Jun 2002 -- gas and steam 900-2,500 m extended 5 km E
02 Jun-07 Jun 2002 -- ash and gas 0.7-1 km --
02 Jun-07 Jun 2002 -- gas 2.5 km --
07 Jun-14 Jun 2002 -- ash and gas ~1 km --

Table 2. Thermal anomalies visible in AVHRR satellite imagery at Shiveluch during 30 March through 13 June. On some days, clouds obscured the view. Courtesy KVERT.

Date Number of pixels Maximum band-3 temperature Background Comment
30 Mar 2002 5 20°C -15 to -20°C --
31 Mar-02 Apr 2002 -- -- -- Weak thermal anomalies visible through cloud cover.
19 Apr 2002 -- -- -- Thermal anomalies visible.
22 Apr-23 Apr 2002 -- -- -- Thermal anomalies visible.
23 Apr 2002 6 49°C -5 to -10°C Three pixels at max. band-3 temp. (near saturation).
30 Apr 2002 1-4 49°C 5 to -10°C --
01 May 2002 -- -- -- Small possible steam/aerosol cloud visible over the summit.
02 May 2002 1-4 49°C 5 to -10°C --
04 May 2002 2 35.4°C -4°C --
04 May 2002 -- -- -- Possible steam/aerosol plume visible extending ~100 km S.
05 May 2002 2 23.4°C -6°C --
17 May 2002 2-6 24°C -4 to 5°C --
19 May 2002 3-4 33-38°C 3-7°C Gas-and-steam plume visible extending 50 km to the SW.
23 May 2002 3-4 33-38°C 3-7°C Gas-and-steam plume visible extending 50 km to the SW.
28 May 2002 2 29.5°C -- --
31 May 2002 4 49.5°C -3°C Steam plume visible extending 50 km to the SW.
31 May 2002 5-9 ~49°C -5 to 4°C --
01 Jun 2002 9 47-49°C 0-5°C "Sensor" recovery pixel also observed.
01 Jun-04 Jun 2002 5-9 ~49°C -5 to 4°C --
09 Jun 2002 6 ~49°C ~0°C --
13 Jun 2002 6 ~49°C ~0°C --

At 1238 on 20 April a 15-minute-long series of shallow events was registered, and at 1240 an increase in eruptive activity was noticed from Klyuchi town (46 km S). Ash clouds rose 800 m along the entire dome. At the same time, a pilot reported an ash cloud 600 m wide and 800 m high above the dome. The character of the ash cloud, as well as photos and visual observations from Klyuchi town suggested that a rockfall had occurred at the dome.

Continuous volcanic tremor was recorded beginning on 3 May. On 5 May a short-lived eruption at 0945 produced an ash-and-gas plume that rose 1.5 km above the lava dome and was accompanied by a 4-minute-long shallow seismic event. At 0050 on 14 May incandescence was observed at the dome summit from Klyuchi town. During the afternoons of 13, 14, and 15 May the nearest seismic station registered high-frequency seismic signals for 14, 11, and 7 hours, respectively. KVERT suggested that the signals were caused by intense snow thawing and running water near the station, masking the volcanic seismicity.

At 2100 on 17 May a gas-and-steam plume containing a small amount of ash rose 800 m above the dome and extended 10 km to the SE; and at 2320 incandescence at the dome summit was observed from Klyuchi town. At 1707 on 21 May a short-lived explosive eruption sent an ash-gas plume to heights of 800 m above the dome. An accompanying 5-minute-long shallow seismic event was registered.

At 1530 on 31 May a large earthquake (ML 3.1) occurred. At 1616 on 1 June eruptive activity increased. Short-lived explosive eruptions sent an ash-gas plume to heights of 3.0 km above the dome, visible from Klyuchi town at 1616 and 1628. Two ~3-minute-long shallow seismic events were registered at 1615 and 1626. During the week, several short-lived explosive eruptions per day sent ash-gas plumes to heights of 700-1000 m above the dome. On 1 and 2 June two 11- and 100-minute-long episodes of strong high-frequency volcanic tremor were registered. The Concern Color Code was increased from Yellow ("volcano is restless") to Orange ("volcano is in eruption or eruption may occur at any time").

Shallow seismic events 4-5 minutes long registered during early June, and there were 1-3 short-lived explosive eruptions per day that probably sent ash-gas plumes to heights of ~1.0 km above the dome. Seismic data did not reveal any strong explosions. As of 14 June the Concern Color Code was returned to Yellow.

Geologic Background. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Information Contacts: Olga Chubarova, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tom Miller and Dave Schneider, Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA, b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA (URL: http://www.avo.alaska.edu/), and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Shishaldin (United States) — May 2002 Citation iconCite this Report

Shishaldin

United States

54.756°N, 163.97°W; summit elev. 2857 m

All times are local (unless otherwise noted)


Seismicity increases briefly during mid-May 2002

During mid-May 2002, the Alaska Volcano Observatory (AVO) detected an increase in background seismicity at Shishaldin that lasted for about one week. There was an increase in the number of located shallow low-frequency earthquakes and several 2-3-minute-long tremor-like signals that were inferred to be from a deep source. No thermal anomalies were visible on satellite imagery and there were no eyewitness reports of anomalous volcanic activity. Shishaldin remained at Concern Color Code Green ("volcano is in quiet, "dormant" state"). The last reported activity at Shishaldin included a thermal anomaly and small explosions during August 2000 (BGVN 25:08).

Geologic Background. The beautifully symmetrical Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steam plume often rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of Strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.

Atmospheric Effects

The enormous aerosol cloud from the March-April 1982 eruption of Mexico's El Chichón persisted for years in the stratosphere, and led to the Atmospheric Effects section becoming a regular feature of the Bulletin. Descriptions of the initial dispersal of major eruption clouds remain with the individual eruption reports, but observations of long-term stratospheric aerosol loading will be found in this section.

Atmospheric Effects (1980-1989)  Atmospheric Effects (1995-2001)

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements  Obituaries

Misc Reports

Reports are sometimes published that are not related to a Holocene volcano. These might include observations of a Pleistocene volcano, earthquake swarms, or floating pumice. Reports are also sometimes published in which the source of the activity is unknown or the report is determined to be false. All of these types of additional reports are listed below by subject.

Additional Reports  False Reports