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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

Sabancaya (Peru) Daily explosions with ash emissions, large SO2 flux, ongoing thermal anomalies, December 2019-May 2020

Sheveluch (Russia) Lava dome growth and thermal anomalies continue through April 2020, but few ash explosions

Dukono (Indonesia) Numerous ash explosions continue through March 2020

Etna (Italy) Strombolian explosions and ash emissions continue, October 2019-March 2020

Merapi (Indonesia) Explosions produced ash plumes, ashfall, and pyroclastic flows during October 2019-March 2020

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



Sabancaya (Peru) — June 2020 Citation iconCite this Report

Sabancaya

Peru

15.787°S, 71.857°W; summit elev. 5960 m

All times are local (unless otherwise noted)


Daily explosions with ash emissions, large SO2 flux, ongoing thermal anomalies, December 2019-May 2020

Although tephrochronology has dated activity at Sabancaya back several thousand years, renewed activity that began in 1986 was the first recorded in over 200 years. Intermittent activity since then has produced significant ashfall deposits, seismic unrest, and fumarolic emissions. A new period of explosive activity that began in November 2016 has been characterized by pulses of ash emissions with some plumes exceeding 10 km altitude, thermal anomalies, and significant SO2 plumes. Ash emissions and high levels of SO2 continued each week during December 2019-May 2020. The Observatorio Vulcanologico INGEMMET (OVI) reports weekly on numbers of daily explosions, ash plume heights and directions of drift, seismicity, and other activity. The Buenos Aires Volcanic Ash Advisory Center (VAAC) issued three or four daily reports of ongoing ash emissions at Sabancaya throughout the period.

The dome inside the summit crater continued to grow throughout this period, along with nearly constant ash, gas, and steam emissions; the average number of daily explosions ranged from 4 to 29. Ash and gas plume heights rose 1,800-3,800 m above the summit crater, and multiple communities around the volcano reported ashfall every month (table 6). Sulfur dioxide emissions were notably high and recorded daily with the TROPOMI satellite instrument (figure 75). Thermal activity declined during December 2019 from levels earlier in the year but remained steady and increased in both frequency and intensity during April and May 2020 (figure 76). Infrared satellite images indicated that the primary heat source throughout the period was from the dome inside the summit crater (figure 77).

Table 6. Persistent activity at Sabancaya during December 2019-May 2020 included multiple daily explosions with ash plumes that rose several kilometers above the summit and drifted in many directions; this resulted in ashfall in communities within 30 km of the volcano. Satellite instruments recorded SO2 emissions daily. Data courtesy of OVI-INGEMMET.

Month Avg. Daily Explosions by week Max plume Heights (m above crater) Plume drift (km) and direction Communities reporting ashfall Min Days with SO2 over 2 DU
Dec 2019 16, 13, 5, 5 2,600-3,800 20-30 NW Pinchollo, Madrigal, Lari, Maca, Achoma, Coporaque, Yanque, Chivay, Huambo, Cabanaconde 27
Jan 2020 10, 8, 11, 14, 4 1,800-3,400 30 km W, NW, SE, S Chivay, Yanque, Achoma 29
Feb 2020 8, 11, 20, 19 2,000-2,200 30 km SE, E, NE, W Huambo 29
Mar 2020 14, 22, 29, 18 2,000-3,000 30 km NE, W, NW, SW Madrigal, Lari, Pinchollo 30
Apr 2020 12, 12, 16, 13, 8 2,000-3,000 30 km SE, NW, E, S Pinchollo, Madrigal, Lari, Maca, Ichupampa, Yanque, Chivay, Coporaque, Achoma 27
May 2020 15, 14, 6, 16 1,800-2,400 30 km SW, SE, E, NE, W Chivay, Achoma, Maca, Lari, Madrigal, Pinchollo 27
Figure (see Caption) Figure 75. Sulfur dioxide anomalies were captured daily from Sabancaya during December 2019-May 2020 by the TROPOMI instrument on the Sentinel-5P satellite. Some of the largest SO2 plumes are shown here with dates listed in the information at the top of each image. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 76. Thermal activity at Sabancaya declined during December 2019 from levels earlier in the year but remained steady and increased slightly in frequency and intensity during April and May 2020, according to the MIROVA graph of Log Radiative Power from 23 June 2019 through May 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 77. Sentinel-2 satellite imagery of Sabancaya confirmed the frequent ash emissions and ongoing thermal activity from the dome inside the summit crater during December 2019-May 2020. Top row (left to right): On 6 December 2019 a large plume of steam and ash drifted N from the summit. On 16 December 2019 a thermal anomaly encircled the dome inside the summit caldera while gas and possible ash drifted NW. On 14 April 2020 a very similar pattern persisted inside the crater. Bottom row (left to right): On 19 April an ash plume was clearly visible above dense cloud cover. On 24 May the infrared glow around the dome remained strong; a diffuse plume drifted W. A large plume of ash and steam drifted SE from the summit on 29 May. Infrared images use Atmospheric penetration rendering (bands 12, 11, 8a), other images use Natural Color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

The average number of daily explosions during December 2019 decreased from a high of 16 the first week of the month to a low of five during the last week. Six pyroclastic flows occurred on 10 December (figure 78). Tremors were associated with gas-and-ash emissions for most of the month. Ashfall was reported in Pinchollo, Madrigal, Lari, Maca, Achoma, Coporaque, Yanque, and Chivay during the first week of the month, and in Huambo and Cabanaconde during the second week (figure 79). Inflation of the volcano was measured throughout the month. SO2 flux was measured by OVI as ranging from 2,500 to 4,300 tons per day.

Figure (see Caption) Figure 78. Multiple daily explosions at Sabancaya produced ash plumes that rose several kilometers above the summit. Left image is from 5 December and right image is from 11 December 2019. Note pyroclastic flows to the right of the crater on 11 December. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-49-2019/INGEMMET Semana del 2 al 8 de diciembre de 2019 and RSSAB-50-2019/INGEMMET Semana del 9 al 15 de diciembre de 2019).
Figure (see Caption) Figure 79. Communities to the N and W of Sabancaya recorded ashfall from the volcano the first week of December and also every month during December 2019-May 2020. The red zone is the area where access is prohibited (about a 12-km radius from the crater). Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-22-2020/INGEMMET Semana del 25 al 31 de mayo del 2020).

During January and February 2020 the number of daily explosions averaged 4-20. Ash plumes rose as high as 3.4 km above the summit (figure 80) and drifted up to 30 km in multiple directions. Ashfall was reported in Chivay, Yanque, and Achoma on 8 January, and in Huambo on 25 February. Sulfur dioxide flux ranged from a low of 1,200 t/d on 29 February to a high of 8,200 t/d on 28 January. Inflation of the edifice was measured during January; deformation changed to deflation in early February but then returned to inflation by the end of the month.

Figure (see Caption) Figure 80. Ash plumes rose from Sabancaya every day during January and February 2020. Left: 11 January. Right: 28 February. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-02-2020/INGEMMET Semana del 06 al 12 de enero del 2020 and RSSAB-09-2020/INGEMMET Semana del 24 de febrero al 01 de marzo del 2020).

Explosions continued during March and April 2020, averaging 8-29 per day. Explosions appeared to come from multiple vents on 11 March (figure 81). Ash plumes rose 3 km above the summit during the first week of March and again the first week of April; they were lower during the other weeks. Ashfall was reported in Madrigal, Lari, and Pinchollo on 27 March and 5 April. On 17 April ashfall was reported in Maca, Ichupampa, Yanque, Chivay, Coporaque, and Achoma. Sulfur dioxide flux ranged from 1,900 t/d on 5 March to 10,700 t/d on 30 March. Inflation at depth continued throughout March and April with 10 +/- 4 mm recorded between 21 and 26 April. Similar activity continued during May 2020; explosions averaged 6-16 per day (figure 82). Ashfall was reported on 6 May in Chivay, Achoma, Maca, Lari, Madrigal, and Pinchollo; heavy ashfall was reported in Achoma on 12 May. Additional ashfall was reported in Achoma, Maca, Madrigal, and Lari on 23 May.

Figure (see Caption) Figure 81. Explosions at Sabancaya on 11 March 2020 appeared to originate simultaneously from two different vents (left). The plume on 12 April was measured at about 2,500 m above the summit. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-11-2020/INGEMMET Semana del 9 al 15 de marzo del 2020 and RSSAB-15-2020/INGEMMET Semana del 6 al 12 de abril del 2020).
Figure (see Caption) Figure 82. Explosions dense with ash continued during May 2020 at Sabancaya. On 11 and 29 May 2020 ash plumes rose from the summit and drifted as far as 30 km before dissipating. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya , RSSAB-20-2020/INGEMMET Semana del 11 al 17 de mayo del 2020 and RSSAB-22-2020/INGEMMET Semana del 25 al 31 de mayo del 2020).

Geologic Background. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

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); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Sheveluch (Russia) — May 2020 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Lava dome growth and thermal anomalies continue through April 2020, but few ash explosions

The eruption at Sheveluch has continued for more than 20 years, with strong explosions that have produced ash plumes, lava dome growth, hot avalanches, numerous thermal anomalies, and strong fumarolic activity (BGVN 44:05). During this time, there have been periods of greater or lesser activity. The most recent period of increased activity began in December 2018 and continued through October 2019 (BGVN 44:11). This report covers activity between November 2019 to April 2020, a period during which activity waned. The volcano is monitored by the Kamchatka Volcanic Eruptions Response Team (KVERT) and Tokyo Volcanic Ash Advisory Center (VAAC).

During the reporting period, KVERT noted that lava dome growth continued, accompanied by incandescence of the dome blocks and hot avalanches. Strong fumarolic activity was also present (figure 53). However, the overall eruption intensity waned. Ash plumes sometimes rose to 10 km altitude and drifted downwind over 600 km (table 14). The Aviation Color Code (ACC) remained at Orange (the second highest level on a four-color scale), except for 3 November when it was raised briefly to Red (the highest level).

Figure (see Caption) Figure 53. Fumarolic activity of Sheveluch’s lava dome on 24 January 2020. Photo by Y. Demyanchuk; courtesy of KVERT.

Table 14. Explosions and ash plumes at Sheveluch during November 2019-April 2020. Dates and times are UTC, not local. Data courtesy of KVERT and the Tokyo VAAC.

Dates Plume Altitude (km) Drift Distance and Direction Remarks
01-08 Nov 2019 -- 640 km NW 3 November: ACC raised to Red from 0546-0718 UTC before returning to Orange.
08-15 Nov 2019 9-10 1,300 km ESE
17-27 Dec 2019 6.0-6.5 25 km E Explosions at about 23:50 UTC on 21 Dec.
20-27 Mar 2020 -- 45 km N 25 March: Gas-and-steam plume containing some ash.
03-10 Apr 2020 10 km 526 km SE 8 April: Strong explosion at 1910 UTC.
17-24 Apr 2020 -- 140 km NE Re-suspended ash plume.

KVERT reported thermal anomalies over the volcano every day, except for 25-26 January, when clouds obscured observations. During the reporting period, thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm recorded hotspots on 10 days in November, 13 days in December, nine days in January, eight days in both February and March, and five days in April. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected numerous hotspots every month, almost all of which were of moderate radiative power (figure 54).

Figure (see Caption) Figure 54. Thermal anomalies at Sheveluch continued at elevated levels during November 2019-April 2020, as seen on this MIROVA Log Radiative Power graph for July 2019-April 2020. Courtesy of MIROVA.

High sulfur dioxide levels were occasionally recorded just above or in the close vicinity of Sheveluch by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite, but very little drift was observed.

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: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); 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/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Dukono (Indonesia) — May 2020 Citation iconCite this Report

Dukono

Indonesia

1.693°N, 127.894°E; summit elev. 1229 m

All times are local (unless otherwise noted)


Numerous ash explosions continue through March 2020

The ongoing eruption at Dukono is characterized by frequent explosions that send ash plumes to about 1.5-3 km altitude (0.3-1.8 km above the summit), although a few have risen higher. This type of typical activity (figure 13) continued through at least March 2020. The ash plume data below (table 21) were primarily provided by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and the Darwin Volcanic Ash Advisory Centre (VAAC). During the reporting period of October 2019-March 2020, the Alert Level remained at 2 (on a scale of 1-4) and the public was warned to remain outside of the 2-km exclusion zone.

Table 21. Monthly summary of reported ash plumes from Dukono for October 2019-March 2020. The direction of drift for the ash plume through each month was highly variable; notable plume drift each month was only indicated in the table if at least two weekly reports were consistent. Data courtesy of the Darwin VAAC and PVMBG.

Month Plume Altitude (km) Notable Plume Drift
Oct 2019 1.8-3 Multiple
Nov 2019 1.8-2.3 E, SE, NE
Dec 2019 1.8-2.1 E, SE
Jan 2020 1.8-2.1 E, SE, SW, S
Feb 2020 2.1-2.4 S, SW
Mar 2020 1.5-2.3 Multiple
Figure (see Caption) Figure 13.Satellite image of Dukono from Sentinel-2 on 12 November 2019, showing an ash plume drifting E. Image uses natural color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

During the reporting period, high levels of sulfur dioxide were only recorded above or near the volcano during 30-31 October and 4 November 2019. High levels were recorded by the Ozone Mapping and Profiler Suite (OMPS) instrument aboard the Suomi National Polar-orbiting Partnership (NPP) satellite on 30 October 2019, in a plume drifting E. The next day high levels were also recorded by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite on 31 October (figure 14) and 4 November 2019, in plumes drifting SE and NE, respectively.

Figure (see Caption) Figure 14. Sulfur dioxide emission on 31 October 2019 drifting E, probably from Dukono, as recorded by the TROPOMI instrument aboard the Sentinel-5P satellite. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Geologic Background. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

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/); 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/); 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).


Etna (Italy) — April 2020 Citation iconCite this Report

Etna

Italy

37.748°N, 14.999°E; summit elev. 3320 m

All times are local (unless otherwise noted)


Strombolian explosions and ash emissions continue, October 2019-March 2020

Mount Etna is a stratovolcano located on the island of Sicily, Italy, with historical eruptions that date back 3,500 years. The most recent eruptive period began in September 2013 and has continued through March 2020. Activity is characterized by Strombolian explosions, lava flows, and ash plumes that commonly occur from the summit area, including the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). The newest crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC. This reporting period covers information from October 2019 through March 2020 and includes frequent explosions and ash plumes. The primary source of information comes from the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Summary of activity during October 2019-March 2020. Strombolian activity and gas-and-steam and ash emissions were frequently observed at Etna throughout the entire reporting period, according to INGV and Toulouse VAAC notices. Activity was largely located within the main cone (Voragine-Bocca Nuova complex), the Northeast Crater (NEC), and the New Southeast Crater (NSEC). On 1, 17, and 19 October, ash plumes rose to a maximum altitude of 5 km. Due to constant Strombolian explosions, ground observations showed that a scoria cone located on the floor of the VOR Crater had begun to grow in late November and again in late January 2020. A lava flow was first detected on 6 December at the base of the scoria cone in the VOR Crater, which traveled toward the adjacent BN Crater. Additional lava flows were observed intermittently throughout the reporting period in the same crater. On 13 March, another small scoria cone had formed in the main VOR-BN complex due to Strombolian explosions.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows multiple episodes of thermal activity varying in power from 22 June 2019 to March 2020 (figure 286). The power and frequency of these thermal anomalies significantly decreased between August to mid-September. The pulse of activity in mid-September reflected a lava flow from the VOR Crater (BGVN 44:10). By late October through November, thermal anomalies were relatively weaker and less frequent. The next pulse in thermal activity reflected in the MIROVA graph occurred in early December, followed by another shortly after in early January, both of which were due to new lava flows from the VOR Crater. After 9 January the thermal anomalies remained frequent and strong; active lava flows continued through March accompanied by Strombolian explosions, gas-and-steam, SO2, and ash emissions. The most recent distinct pulse in thermal activity was seen in mid-March; on 13 March, another lava flow formed, accompanied by an increase in seismicity. This lava flow, like the previous ones, also originated in the VOR Crater and traveled W toward the BN Crater.

Figure (see Caption) Figure 286. Multiple episodes of varying activity at Etna from 22 June 2019 through March 2020 were reflected in the MIROVA thermal energy data (Log Radiative Power). Courtesy of MIROVA.

Activity during October-December 2019. During October 2019, VONA (Volcano Observatory Notice for Aviation) notices issued by INGV reported ash plumes rose to a maximum altitude of 5 km on 1, 17, and 19 October. Strombolian explosions occurred frequently. Explosions were detected primarily in the VOR-BN Craters, ejecting coarse pyroclastic material that fell back into the crater area and occasionally rising above the crater rim. Ash emissions rose from the VOR-BN and NEC while intense gas-and-steam emissions were observed in the NSEC (figure 287). Between 10-12 and 14-20 October fine ashfall was observed in Pedara, Mascalucia, Nicolosi, San Giovanni La Punta, and Catania. In addition to these ash emissions, the explosive Strombolian activity contributed to significant SO2 plumes that drifted in different directions (figure 288).

Figure (see Caption) Figure 287. Webcam images of ash emissions from the NE Crater at Etna from the a) CUAD (Catania) webcam on 10 October 2019; b) Milo webcam on 11 October 2019; c) Milo webcam on 12 October 2019; d) M.te Cagliato webcam on 13 October 2019. Courtesy of INGV (Report 42/2019, ETNA, Bollettino Settimanale, 07/10/2019 - 13/10/2019, data emissione 15/10/2019).
Figure (see Caption) Figure 288. Strombolian activity at Etna contributed to significant SO2 plumes that drifted in multiple directions during the intermittent explosions in October 2019. Top left: 1 October 2019. Top right: 2 October 2019. Middle left: 15 October 2019. Middle right: 18 October 2019. Bottom left: 13 November 2019. Bottom right: 1 December 2019. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

The INGV weekly bulletin covering activity between 25 October and 1 November 2019 reported that Strombolian explosions occurred at intervals of 5-10 minutes from within the VOR-BN and NEC, ejecting incandescent material above the crater rim, accompanied by modest ash emissions. In addition, gas-and-steam emissions were observed from all the summit craters. Field observations showed the cone in the crater floor of VOR that began to grow in mid-September 2019 had continued to grow throughout the month. During the week of 4-10 November, Strombolian activity within the Bocca Nuova Crater was accompanied by gas-and-steam emissions. The explosions in the VOR Crater occasionally ejected incandescent ejecta above the crater rim (figures 289 and 290). For the remainder of the month Strombolian explosions continued in the VOR-BN and NEC, producing sporadic ash emissions. Isolated and discontinuous explosions in the New Southeast Crater (NSEC) also produced fine ash, though gas-and-steam emissions still dominated the activity at this crater. Additionally, the explosions from these summit craters were frequently accompanied by strong SO2 emissions that drifted in different directions as discrete plumes.

Figure (see Caption) Figure 289. Photo of Strombolian activity and crater incandescence in the Voragine Crater at Etna on 15 November 2019. Photo by B. Behncke, taken by Tremestieri Etneo. Courtesy of INGV (Report 47/2019, ETNA, Bollettino Settimanale, 11/11/2019 - 17/11/2019, data emissione 19/11/2019).
Figure (see Caption) Figure 290. Webcam images of summit crater activity during 26-29 November and 1 December 2019 at Etna. a) image recorded by the high-resolution camera on Montagnola (EMOV); b) and c) webcam images taken from Tremestieri Etneo on the southern slope of Etna showing summit incandescence; d) image recorded by the thermal camera on Montagnola (EMOT) showing summit incandescence at the NSEC. Courtesy of INGV (Report 49/2019, ETNA, Bollettino Settimanale, 25/11/2019 - 01/12/2019, data emissione 03/12/2019).

Frequent Strombolian explosions continued through December 2019 within the VOR-BN, NEC, and NSEC Craters with sporadic ash emissions observed in the VOR-BN and NEC. On 6 December, Strombolian explosions increased in the NSEC; webcam images showed incandescent pyroclastic material ejected above the crater rim. On the morning of 6 December a lava flow was observed from the base of the scoria cone in the VOR Crater that traveled toward the adjacent Bocca Nuova Crater. INGV reported that a new vent opened on the side of the saddle cone (NSEC) on 11 December and produced explosions until 14 December.

Activity during January-March 2020. On 9 January 2020 an aerial flight organized by RAI Linea Bianca and the state police showed the VOR Crater continuing to produce lava that was flowing over the crater rim into the BN Crater with some explosive activity in the scoria cone. Explosive Strombolian activity produced strong and distinct SO2 plumes (figure 291) and ash emissions through March, according to the weekly INGV reports, VONA notices, and satellite imagery. Several ash emissions during 21-22 January rose from the vent that opened on 11 December. According to INGV’s weekly bulletin for 21-26 January, the scoria cone in the VOR crater produced Strombolian explosions that increased in frequency and contributed to rapid cone growth, particularly the N part of the cone. Lava traveled down the S flank of the cone and into the adjacent Bocca Nuova Crater, filling the E crater (BN-2) (figure 292). The NEC had discontinuous Strombolian activity and periodic, diffuse ash emissions.

Figure (see Caption) Figure 291. Distinct SO2 plumes drifting in multiple directions from Etna were visible in satellite imagery as Strombolian activity continued through March 2020. Top left: 21 January 2020. Top right: 2 February 2020. Bottom left: 10 March 2020. Bottom right: 19 March 2020. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 292. a) A map of the lava field at Etna showing cooled flows (yellow) and active flows (red). The base of the scoria cone is outlined in black while the crater rim is outlined in red. b) Thermal image of the Bocca Nuova and Voragine Craters. The bright orange is the warmest temperature measure in the flow. Courtesy of INGV, photos by Laboratorio di Cartografia FlyeEye Team (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

Strombolian explosions continued into February 2020, accompanied by ash emissions and lava flows from the previous months (figure 293). During 17-23 February, INGV reported that some subsidence was observed in the central portion of the Bocca Nuova Crater. During 24 February to 1 March, the Strombolian explosions ejected lava from the VOR Crater up to 150-200 m above the vent as bombs fell on the W edge of the VOR crater rim (figure 294). Lava flows continued to move into the W part of the Bocca Nuova Crater.

Figure (see Caption) Figure 293. Webcam images of A) Strombolian activity and B) effusive activity fed by the scoria cone grown inside the VOR Crater at Etna taken on 1 February 2020. C) Thermal image of the lava field produced by the VOR Crater taken by L. Lodato on 3 February (bottom left). Image of BN-1 taken by F. Ciancitto on 3 February in the summit area (bottom right). Courtesy of INGV; Report 06/2020, ETNA, Bollettino Settimanale, 27/01/2020 - 02/02/2020, data emissione 04/02/2020 (top) and Report 07/2020, ETNA, Bollettino Settimanale, 03/02/2020 - 09/02/2020, data emissione 11/02/2020 (bottom).
Figure (see Caption) Figure 294. Photos of the VOR intra-crater scoria cone at Etna: a) Strombolian activity resumed on 25 February 2020 from the SW edge of BN taken by B. Behncke; b) weak Strombolian activity from the vent at the base N of the cone on 29 February 2020 from the W edge of VOR taken by V. Greco; c) old vent present at the base N of the cone, taken on 17 February 2020 from the E edge of VOR taken by B. Behncke; d) view of the flank of the cone, taken on 24 February 2020 from the W edge of VOR taken by F. Ciancitto. Courtesy of INGV (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

During 9-15 March 2020 Strombolian activity was detected in the VOR Crater while discontinuous ash emissions rose from the NEC and NSEC. Bombs were found in the N saddle between the VOR and NSEC craters. On 9 March, a small scoria cone that had formed in the Bocca Nuova Crater and was ejecting bombs and lava tens of meters above the S crater rim. The lava flow from the VOR Crater was no longer advancing. A third scoria cone had formed on 13 March NE in the main VOR-BN complex due to the Strombolian explosions on 29 February. Another lava flow formed on 13 March, accompanied by an increase in seismicity. The weekly report for 16-22 March reported Strombolian activity detected in the VOR Crater and gas-and-steam and rare ash emissions observed in the NEC and NSEC (figure 295). Explosions in the Bocca Nuova Crater ejected spatter and bombs 100 m high.

Figure (see Caption) Figure 295. Map of the summit crater area of Etna showing the active vents and lava flows during 16-22 March 2020. Black hatch marks indicate the crater rims: BN = Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Courtesy of INGV (Report 13/2020, ETNA, Bollettino Settimanale, 16/03/2020 - 22/03/2020, data emissione 24/03/2020).

Geologic Background. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Information Contacts: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/aeroweb/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/); 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); Boris Behncke, Sonia Calvari, and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: https://twitter.com/etnaboris, Image at https://twitter.com/etnaboris/status/1183640328760414209/photo/1).


Merapi (Indonesia) — April 2020 Citation iconCite this Report

Merapi

Indonesia

7.54°S, 110.446°E; summit elev. 2910 m

All times are local (unless otherwise noted)


Explosions produced ash plumes, ashfall, and pyroclastic flows during October 2019-March 2020

Merapi is a highly active stratovolcano located in Indonesia, just north of the city of Yogyakarta. The current eruption episode began in May 2018 and was characterized by phreatic explosions, ash plumes, block avalanches, and a newly active lava dome at the summit. This reporting period updates information from October 2019-March 2020 that includes explosions, pyroclastic flows, ash plumes, and ashfall. The primary reporting source of activity comes from Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG, the Center for Research and Development of Geological Disaster Technology, a branch of PVMBG) and Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM).

Some ongoing lava dome growth continued in October 2019 in the NE-SW direction measuring 100 m in length, 30 m in width, and 20 m in depth. Gas-and-steam emissions were frequent, reaching a maximum height of 700 m above the crater on 31 October. An explosion at 1631 on 14 October removed the NE-SW trending section of the lava dome and produced an ash plume that rose 3 km above the crater and extended SW for about 2 km (figures 90 and 91). The plume resulted in ashfall as far as 25 km to the SW. According to a Darwin VAAC notice, a thermal hotspot was detected in HIMAWARI-8 satellite imagery. A pyroclastic flow associated with the eruption traveled down the SW flank in the Gendol drainage. During 14-20 October lava flows from the crater generated block-and-ash flows that traveled 1 km SW, according to BPPTKG.

Figure (see Caption) Figure 90. An ash plume rising 3 km above Merapi on 14 October 2019.
Figure (see Caption) Figure 91. Webcam image of an ash plume rising above Merapi at 1733 on 14 October 2019. Courtesy of BPPTKG via Jaime S. Sincioco.

At 0621 on 9 November 2019, an eruption produced an ash plume that rose 1.5 km above the crater and drifted W. Ashfall was observed in the W region as far as 15 km from the summit in Wonolelo and Sawangan in Magelang Regency, as well as Tlogolele and Selo in Boyolali Regency. An associated pyroclastic flow traveled 2 km down the Gendol drainage on the SE flank. On 12 November aerial drone photographs were used to measure the volume of the lava dome, which was 407,000 m3. On 17 November, an eruption produced an ash plume that rose 1 km above the crater, resulting in ashfall as far as 15 km W from the summit in the Dukun District, Magelang Regency (figure 92). A pyroclastic flow accompanying the eruption traveled 1 km down the SE flank in the Gendol drainage. By 30 November low-frequency earthquakes and CO2 gas emissions had increased.

Figure (see Caption) Figure 92. An ash plume rising 1 km above Merapi on 17 November 2019. Courtesy of BPPTKG.

Volcanism was relatively low from 18 November 2019 through 12 February 2020, characterized primarily by gas-and-steam emissions and intermittent volcanic earthquakes. On 4 January a pyroclastic flow was recorded by the seismic network at 2036, but it wasn’t observed due to weather conditions. On 13 February an explosion was detected at 0516, which ejected incandescent material within a 1-km radius from the summit (figure 93). Ash plumes rose 2 km above the crater and drifted NW, resulting in ashfall within 10 km, primarily S of the summit; lightning was also seen in the plume. Ash was observed in Hargobinangun, Glagaharjo, and Kepuharjo. On 19 February aerial drone photographs were used to measure the change in the lava dome after the eruption; the volume of the lava had decreased, measuring 291,000 m3.

Figure (see Caption) Figure 93. Webcam image of an ash plume rising from Merapi at 0516 on 13 February 2020. Courtesy of MAGMA Indonesia and PVMBG.

An explosion on 3 March at 0522 produced an ash plume that rose 6 km above the crater (figure 94), resulting in ashfall within 10 km of the summit, primarily to the NE in the Musuk and Cepogo Boyolali sub-districts and Mriyan Village, Boyolali (3 km from the summit). A pyroclastic flow accompanied this eruption, traveling down the SSE flank less than 2 km. Explosions continued to be detected on 25 and 27-28 March, resulting in ash plumes. The eruption on 27 March at 0530 produced an ash plume that rose 5 km above the crater, causing ashfall as far as 20 km to the W in the Mungkid subdistrict, Magelang Regency, and Banyubiru Village, Dukun District, Magelang Regency. An associated pyroclastic flow descended the SSE flank, traveling as far as 2 km. The ash plume from the 28 March eruption rose 2 km above the crater, causing ashfall within 5 km from the summit in the Krinjing subdistrict primarily to the W (figure 94).

Figure (see Caption) Figure 94. Images of ash plumes rising from Merapi during 3 March (left) and 28 March 2020 (right). Images courtesy of BPPTKG (left) and PVMBG (right).

Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

Information Contacts: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), Center for Research and Development of Geological Disaster Technology (URL: http://merapi.bgl.esdm.go.id/, Twitter: @BPPTKG); 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/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/, Twitter: https://twitter.com/BNPB_Indonesia); 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/); Jamie S. Sincioco, Phillipines (Twitter: @jaimessincioco, Image at https://twitter.com/jaimessincioco/status/1227966075519635456/photo/1).


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/).

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Bulletin of the Global Volcanism Network - Volume 38, Number 11 (November 2013)

Managing Editor: Richard Wunderman

Ebulobo (Indonesia)

August 2013–glowing areas and hot plumes

Ibu (Indonesia)

Growing lava dome; numerous thermal alerts September 2011-March 2014

Nishinoshima (Japan)

November 2013 submarine flank eruption spurs island growth

Planchon-Peteroa (Chile)

February-June 2011 eruption; ashfall in local towns in May 2011

Soufriere Hills (United Kingdom)

By March 2014, an over 50-month-long decline in extrusion (Pause 5)

Yasur (Vanuatu)

Explosive activity during May, August, and November 2013



Ebulobo (Indonesia) — November 2013 Citation iconCite this Report

Ebulobo

Indonesia

8.817°S, 121.191°E; summit elev. 2096 m

All times are local (unless otherwise noted)


August 2013–glowing areas and hot plumes

Our last report (CSLP 19-69) discussed a summit eruption at Ebulobo stratovolcano, near the S coast of Central Flores island, that in 1969 had emitted ash and steam as well as "fire" (generally taken as incandescence but also possibly flames). CVGHM (Center for Volcanology and Mitigation of Geologic Disasters), issued a report on Ebulobo on 26 August 2013 informing readers that during August 2013, observers noted one or more hot emissions escaping from the crater. The resulting plume was of sparse consistency, white in color, under weak pressure, and it rose to 5-30 m above the peak. "Smoke" was noted.

The CVGHM report noted that on the night of 21 August 2013, observers on the volcano's N side saw incandescence at the summit area. Observations during the night of 22-23 August revealed points of glowing remained unchanged. The glowing was considered anomalous, having not been seen since 2011. The exact cause of the incandescent regions was not reported No new fissures, lava flows or pyroclastic flows were reported. The glowing later terminated as discussed in an October follow up report.

During June 2013, the system recorded the earthquakes shown in table 1.

Table 1. A summary of seismicity recorded at Ebulobo. Dashes signify cases without reported data. Extracted from the 26 August and 17 October CVGHM reports.

Month (2013) Shallow (VB) Deep volcanic (VA) Low-frequency (long period) Local tectonic (TL) Long distance (TJ)
June -- 12 1 18 47
July -- 19 1 18 38
August -- 57 -- 45 60
September 2 62 -- 27 67
1-16(?) October 2 13 7 7 35

During 1-22 August 2013, the seismic system also recorded tremor with maximum amplitudes in the range of 0.5-15 mm.

Ebulobo (figure 1) has a dedicated observation post and two seismic instruments as discussed further below.

Figure (see Caption) Figure 1. Ebulobo as seen in a photo taken 9 June 2009. Copyrighted photo by Andrzej-Muda.

Glow diminishes and Alert Level drops (to I). During September-October white plumes rose as high as 100 m above the crater. Despite that, the glowing area had remained absent after 27 August. On 17 October CVGHM scaled back the Alert from II to I (Normal, on a scale that reaches IV).

More background. The following was extracted from CVGHM reporting.

"Ebulobo Volcano is located in the district of Nagekeo, province of Nusa Tenggara Timur. Eruptions of Ebulobo generally have consisted of lava streams that quickly formed mounds but have never so far resulted in sudden eruptive outbursts that produced a symmetrically shaped mass to the volcano. Ebulobo's eruptions have occurred between 3 and 58 years. In its historical record, its latest eruptive activity took place in 1941 and consisted of a lava stream.

"Observation of Ebulobo's activity is carried out from its monitoring post in the village of Ekowolo, sub-district of Boa Wae and is done visually and according to tremor events. The monitoring is done by means of a Type VR-60 seismograph and a Type L4C seismometer. The readings are transmitted by a telemetric system."

Geologic Background. Ebulobo, also referred to as Amburombu or Keo Peak, is a steep-sided symmetrical stratovolcano in central Flores Island. The Watu Keli lava flow traveled down the N flank to 4 km from the summit in 1830, the first of only four recorded historical eruptions of the volcano.

Information Contacts: Center for Volcanology and Mitigation of Geologic Disasters (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); and theNational Agency for Disaster Management (BNPB), Gedung Graha 55 Jl. Tanah Abang II No. 57 Postal Code: 10120, Jakarta Pusat, Indonesia (URL: http://www.bnpb.go.id/).


Ibu (Indonesia) — November 2013 Citation iconCite this Report

Ibu

Indonesia

1.488°N, 127.63°E; summit elev. 1325 m

All times are local (unless otherwise noted)


Growing lava dome; numerous thermal alerts September 2011-March 2014

In the first nine months of 2011, Ibu was the scene of frequent avalanches and at least one weak explosion that generated minor white-to-gray plumes (BGVN 36:08). Seismic activity decreased during September 2011, prompting the Center of Volcanology and Geological Hazard Mitigation (CVGHM) to lower the Alert Level to 2 (on a scale of 1-4) on 8 September (the Level rose again later). This report discusses activity from 9 September 2011 through March 2014. The location of Ibu is shown in BGVN 36:08.

According to CVGHM, seismicity increased and volcanic tremor was detected during May through 6 June 2013. The lava dome grew, especially the N part, and by early June had grown taller than the N crater rim. White-to-gray plumes rose 200-450 m above the crater rim. Based on visual and instrumental observations, as well as the hazard potential, CVGHM increased the Alert Level to 3 on 7 June. The public was warned to stay at least 3 km away from the active crater.

CVGHM reported that during 7 June-9 December 2013, the lava dome continued to grow, and incandescent material from the dome filled the river valley in the direction of Duono village, about 5 km NW. The seismicity remained relatively stable. Observers saw occasional weak white-to-gray plumes. On 10 December 2013, the Alert Level was lowered to 2; however, the public was warned to stay at least 2 km away from the active crater, and 3.5 km away from the N part.

Between 1 September 2011 and March 2014, MODVOLC thermal alerts were issued on 70 days, or an average of almost one day every two weeks. Such alerts are consistent with dome growth such as that noted above. (Those alerts are derived from satellite data collected by the MODIS instrument and processed by the Hawai'i Institute of Geophysics and Planetology.) For comparison, between 1 January 2011 and 13 September 2011, these alerts only appeared about once every 2.4 weeks on average.

Geologic Background. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); 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/).


Nishinoshima (Japan) — November 2013 Citation iconCite this Report

Nishinoshima

Japan

27.247°N, 140.874°E; summit elev. 25 m

All times are local (unless otherwise noted)


November 2013 submarine flank eruption spurs island growth

A new island emerged on 20 November 2013 out of the ocean as the result of a Surtseyan eruption on the S flank of Nishinoshima, a small volcanic island in the Izu-Bonin arc, ~940 km S of Tokyo (figure 1). The new island, originally called Niijima ('new island') by the Japan Coast Guard (JCG), eventually merged with Nishinoshima on 24 December 2013. We continue to describe the now merged islands under the name 'Nishinoshima.'

Figure (see Caption) Figure 1. Location of Nishinoshima island shown on an annotated topographic map of the Izu-Bonin arc; the insert shows the area of the main map and the larger regional geography. The map highlights the location of Nishinoshima (Nsi). Other features located respectively from N to S are: Os–Oh–shima; Nij–Nii–jima; Myk–Miyake–jima; Mkr–Mikura–jima; Krs–Kurose hole; Hcj–Hachijo–jima; Shc–outh Hachijo caldera; Ags–Aoga–shima; Myn–Myojin knoll; Sms–South Sumisu; Ssc–South Sumisu caldera; Tsm–Torishima; Sfg–Sofugan; G–Getsuyo seamount; Ka–Kayo seamount; S–Suiyo seamount; Kn–Kinyo seamount; D–Doyo seamount; Nsi–Nishinoshima; Kkt–Kaikata seamount; Ktk–Kaitoku seamount; and Kij–Kita Iou-jima. After Kodaira and others (2007).

Niijima emerges. Niijima emerged by 20 November 2013 from the ocean surface at an area ~0.5 km SSE off the coast of Nishinoshima. The latter is a small (700 m2), uninhabited volcanic island that last erupted and expanded in during 1973-74. Additional background information is included at the end of this report.

Based on satellite images, the Tokyo Volcanic Ash Advisory Center (VAAC) reported that at 0717 UTC on 20 November 2013 a plume rose 600 m over a new island which emerged ~500 m S of Nishinoshima (figure 2). At 0630 UTC on 22 November, a plume rose 900 m. MODVOLC satellite thermal alerts were measured almost daily from 1635 UTC on 23 November and continued through the latest alert noted at 0120 UTC on 7 April 2014.

Figure (see Caption) Figure 2. Niijima produces a plume as it emerges from the ocean to form a new island off the coast of Nishinoshima on 20 November 2013. Courtesy of Kurtenbach (2013); image from the JCG.

On 21 November JCG and the Japan Meteorological Agency (JMA) noted that the island formed was by then ~200 m in diameter. A warning of dense black emissions from the eruption was issued by JCG on 20 November, and television footage (Frisk, 2013) showed on 21 November ash and rocks exploding from the crater as steam billowed out of the crater (figure 3). On 24 November, JCG reported lava flows coming from the newly-formed crater. They extended to the coastline of the island, and bombs continued to be ejected.

Figure (see Caption) Figure 3. A photograph of Niijima from 21 November 2013 shortly after it emerged from the ocean . Note the large airborne rock erupting from the crater. Courtesy of Kurtenbach (2013); picture provided by JCG.

The Advanced Land Imager (ALI) on NASA's Earth Observing-1 (EO-1) satellite captured a natural-color image on 8 December 2013 (figure 4). JMA reported that by early December the area of the new island had grown to 56,000 m2, about three times its initial size, and was 20 to 25 m above sea level.

Figure (see Caption) Figure 4. NASA Earth Observatory satellite image acquired on 8 December 2013 from the EO-1 ALI sensor. The discolored water around the island was attributed to material included volcanic minerals, gases, and seafloor sediment stirred up by the ongoing volcanic eruption. The faint white puffs above the center and SW portion of the island are likely steam and other volcanic gases associated with the eruption. Courtesy of NASA Earth Observatory web site.

Niijima merges with Nishinoshima. NASA's EO-1 ALI satellite again captured a natural-color image of Nishinoshima and Niijima islands on 24 December 2013 and shows only a narrow channel of water appearing to separate the two (figure 5). The water around the islands continued to be discolored by volcanic minerals and gases, as well as by seafloor sediment stirred up by the ongoing eruption. A faint plume, likely steam and other volcanic gases associated with the eruption, drifted SE. Infrared imagery from the same satellite on the same date showed intense heat from the fresh lava, which continued to build the new island. A strip of isolated, discolored (orange) seawater appeared at the junction of the two islands (figure 6).

Figure (see Caption) Figure 5. NASA Earth Observatory satellite image acquired 24 December 2013. Courtesy of NASA Earth Observatory; satellite image by Jesse Allen using EO-1 ALI data from the NASA EO-1 team.
Figure (see Caption) Figure 6. An aerial photograph just prior to the merger of the two islands, taken on 24 December 2013, with Niijima on the right and Nishinoshima on the left. Seawater trapped at the junction has been discolored to orange, attributed to the presence of particulate matter and biochemical activity of organisms in the water. Courtesy of the JCG.

Figure 7 is a drawing by the Japanese Coast Guard (JCG) showing the location of the coastline and the growth of the new island (Niijima) from 20 November 2013 to 26 December 2013. It is striking how much of the island expanded during 13-24 December 2013.

Figure (see Caption) Figure 7. Scale drawing of the merged islands showing the changing coastlines as the new island grew. Colored enclosing lines during the current eruption of Nishinoshima as shown for the following dates: 20, 21, 22, 26, and 30 November 2013, and 1, 4, 7, 13, 24, and 26 December 2013 (note legend translated from Japanese for dates and color of mapped shorelines). Image and interpretation courtesy of JCG.

According to JCG's aerial observation on 20 January 2014, the new part of Nishinoshima island had an area of 0.3 km2 (750 m E to W, and 600 m N to S) (figure 8).

Figure (see Caption) Figure 8. An aerial photograph, looking W, of Nishinoshima island taken on 20 January 2014. The newly merged island, Niijima, on the left, continued to expand NW. White and brown plumes rose from vents on the new land, and the water around the SW portion was discolored. Photo courtesy of the JCG.

New images from an overflight on 3 February (figure 9) confirmed that the activity on the former new island continued steadily. Over the past weeks, the vent fed several active lava flow fronts that enlarged the land in more or less all directions. In particular, there are two active flows relatively close to the vent which had been traveling E and formed a small, almost closed bay with green-orange discolored water inside. The previous shorelines for 20 January 2014 (yellow enclosing line) and 21 November 2013 (white enclosing line) are superimposed over the image to show the growth of the island.

Figure (see Caption) Figure 9. Aerial photography of the island on 3 February 2014. For comparison, the previous shorelines on 20 January 2014 (yellow enclosing line) and 21 November 2013 (white enclosing line). Image courtesy of JCG.

According to Pfeiffer (2014), the island continued growing with lava flows traveling in several directions (figure 10). Its highest peak, formed by the most western of the two active vents, was measured at 66 m. The new addition has more than doubled the size of the island by 16 February. A black-sand beach formed on the NE shore of the old part of the island, as a result of lava fragments washed up by currents and waves.

Figure (see Caption) Figure 10. Direction of lava flow from the western side of two active vents is show by vectors superimposed on the image of the island. North is to the top of the photo. The flow arrows were drawn by JCG over an aerial photograph of the island taken 16 February 2014. Courtesy of JCG.

In summary, the new addition to Nishinoshima grew ~500 m SSE of the island's S flank, beginning ~20 November 2013, from a depth of ~50 m to a height of ~65 m from an originating time no earlier than 1974, the time of the latest addition to the island. Based on continued emissions and satellite-based thermal alerts, it is apparent as of 13 March 2014 that Niijima was still expanding outward in all directions from the vents, and that Nishinoshima had grown to over three times its original size.

Further background. The new island was located in the Volcano Islands, a group of three Japanese active volcanic islands that lie atop the Izo-Bonin-Mariana arc system (Stern and Bloomer, 1992) that stretches S of Japan and N of the Marianas (figure 1).

According to the Geological Survey of Japan, Nishinoshima was an emerged submarine volcano in 1974 with a height of ~3,000 m from the surrounding ocean floor and ~30 km wide at its base.

For further details on earlier Nishinoshima activity refer to our earlier reports in predecessor publications, CSLP 93-73 (eight cards issued during 1973-1974), SEAN 04:07, and BVE 25. The latter (BVE 25) is a 1985 Smithsonian report called the Bulletin of Volcanic Eruptions noting that aerial observations on 2 December 1985 disclosed pale green water SW from the island.

The Geological Survey of Japan reported that Nishinoshima is of andesite to basaltic-andesite composition; Aoki and others (1983) classified the volcano's rocks as high-alkali tholeiite. Nishinoshima is surrounded on all sides by cones, vents, pillars, and parasitic seamounts, and its local bathymetry from surveys in 1911 and 1992 are shown in figure 11.

Figure (see Caption) Figure 11. Comparison of bathymetric maps (depths in meters) around Nishinoshima before and after 1973 eruption. The emerged island is shown in green. Depths of 0-100 m are in white, 100-400 m in light blue, 400-700 m in medium blue, and 700-1,000 m in darker blue. The map on the right shows a survey conducted in 1992, after the eruption, based on 1:50,000 basic map of "Nishino-shima" by the Japan Coast Guard (1993). The map on the left shows a survey conducted prior to the eruption, based on mapping in 1911 (Ossaka, 1973). The new island of Niijima first appeared above the sea surface ~500 m SSE of the S coast of Nishinoshima island shown in the 1992 map. Courtesy of the Geological Survey of Japan (2013).

From the 1992 bathymetric map seen at right on figure 11, it is apparent that the ocean depth from which Niijima erupted in 2013, was ~50 m. A sketch of the setting showing a cross sectional view (roughly NNW-SSE) appears in figure 12.

Figure (see Caption) Figure 12. A sketch depicting an approximately NNW (to the left) to SSE (to the right) cross-section across Nishinoshima (blue indicates sea water) portraying some historical stages of growth. The label "Current Nishinoshima" refers to the pre-existing island prior to and in the early stages of the 2013 eruption. Other labels indicate (a) "Nishinoshima before 1973" (also see 1911 bathymetric map in figure 11), (b) flanking material added to Nishinoshima as it "Emerged during the 1973-74 eruption" (also see 1992 bathymetric map in figure 11), and (c) Niijima "Emerging during ongoing eruption" (red area emerging from the sea early in the 2013 eruption). Original drawing courtesy of The Asahi Shimbun (2013).

References. Aoki, H., and Tokai University Research Group for Marine Volcano, 1983, Petrochemistry of the Nishinoshima Islands, La mer, v. 22, pp. 248-256.

Earth of Fire: Actualité volcanique, Article de fond sur étude de volcan, tectonique, récits et photos de voyage [Volcano News, Feature Article on study of volcanos, tectonics, travel stories and photos], 2013, Evolution of Nishino-shima's eruption, Earth-of-Fire web site (URL: http://www.earth-of-fire.com/page-8837676.html).

Frisk, A., 2013 (21 November), WATCH: Incredible video, photos show new island forming off Japan after volcanic eruption, Global News (URL: http://globalnews.ca/news/981245/watch-incredible-video-photos-show-new-island-forming-off-japan-after-volcanic-eruption/ ).

Geological Survey of Japan, 2013, Nishinoshima (URL: https://gbank.gsj.jp/volcano/Quat_Vol/volcano_data/G22.html).

Japan Coast Guard, 1993, 1:50,000 basic map of "Nishino-shima."

Kodaira, S., Sato, T., Takahashi, N., Miura, S., Tamura, Y., Tatsumi, Y., and Kaneda, Y., 2007, New seismological constraints on growth of continental crust in the Izu-Bonin intra-oceanic arc, Geology, v. 35, no. 11, pp. 1031-1034 (doi: 10.1130/G23901A.1).

Kurtenbach, E., 2013 (21 November), Volcano raises new island far south of Japan, AP (Associated Press) (URL: http://news.yahoo.com/volcano-raises-island-far-south-japan-054228644.html).

Ossaka, J., 1973, On the submarine eruption of Nishinoshima, Bulletin of the Volcanological Society of Japan, v. 18, no. 2, p. 97-98, 173-174.

Pfeiffer, T., 2014 (21 February), Nishinoshima volcano (Izu Islands, Japan): island has doubled in elevation, Volcano Discovery web site (URL: http://www.volcanodiscovery.com/nishino-shima/news/42781/Nishino-Shima-volcano-Izu-Islands-Japan-island-has-doubled-in-elevation.html).

Shun, N., 2014, Kaitei chikei (bottom topography), Nishinoshima Kazan (in Japanese), Geological Survey of Japan web site (URL: https://gbank.gsj.jp/volcano/Act_Vol/nishinoshima/page3.html).

The Asahi Shimbun, 2013 (22 November), Japan counts on survival of new island to expand territorial waters (URL: https://ajw.asahi.com/article/behind_news/social_affairs/AJ201311220084).

Geologic Background. The small island of Nishinoshima was enlarged when several new islands coalesced during an eruption in 1973-74. Another eruption that began offshore in 2013 completely covered the previous exposed surface and enlarged the island again. Water discoloration has been observed on several occasions since. The island is the summit of a massive submarine volcano that has prominent satellitic peaks to the S, W, and NE. The summit of the southern cone rises to within 214 m of the sea surface 9 km SSE.

Information Contacts: Japan Coast Guard (JCG) (URL: http://www.kaiho.mlit.go.jp/); MODVOLC, Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov); ANN (All Nippon News Network) (URL: https://www.youtube.com/user/ANNnewsCH); VolcanoCafe web site (URL: http://volcanocafe.wordpress.com); Earth of Fire web site (URL: http://www.earth-of-fire.com/); Demis web site (URL: http://www.demis.nl/home/pages/Gallery/examples.htm.).


Planchon-Peteroa (Chile) — November 2013 Citation iconCite this Report

Planchon-Peteroa

Chile

35.223°S, 70.568°W; summit elev. 3977 m

All times are local (unless otherwise noted)


February-June 2011 eruption; ashfall in local towns in May 2011

The last Bulletin report (BGVN 35:11) detailed an explosive eruption that began with gas-and-ash explosions in September 2010 and ended in mid-October 2010. Renewed activity began in February 2011 and continued through June 2011. In this report, we highlight the significant ash events from early-to-mid 2011 as well as the continuous monitoring efforts of Servicio Nacional de Geología y Minería (SERNAGEOMIN) during 2011-2013.

During 17 February-27 June 2011, unrest was detected from Planchón-Peteroa and significant meteorological information (SIGMET) notices were distributed by the Buenos Aires Volcanic Ash Advisory Center (VAAC) (table 3). Ash plumes were reported once or twice a month during this time period, although satellite images were not able to detect many of the events. Ash and gas plumes became continuous during late April, and ash plumes rose as high as 5.8 km above sea level(on 26 April). On 29 April, SERNAGEOMIN raised the Alert Level to 3 (Yellow).

Table 3.Emissions from Planchón-Peteroa during 18 February-27 June 2011. The Observatorio Volcanológico de los Andes del Sur (OVDAS) maintained a web-camera that contributed to numerous direct observations of emissions and is frequently listed as a source. Courtesy of VAAC.

Date Altitude (km) Drift Direction Info Sources Comments
18 Feb 2011 3-4.3 km SE SIGMET No ash visible in satellite images.
18 Mar 2011 3-4.3 km SE SIGMET; ODVAS Steam-and-gas plume visible from ODVAS web-camera. No ash visible in satellite images.
26 Mar 2011 -- -- SIGMET No ash visible in satellite images.
01-16 Apr 2011 -- -- SERNAGEOMIN White vapor plumes visible from the web-camera based in Romeral.
17 Apr 2011 4.6 NE SIGMET No ash visible in satellite images.
18 Apr 2011 4.6 NE SIGMET No ash visible in satellite images.
26 Apr 2011 5.8 E SIGMET No ash visible in satellite images.
16-19, 21, 25-29 Apr 2011 1.2-6.4 SW and NW SIGMET; SERNAGEOMIN Frequent ash plumes. Web-camera images captured plumes containing ash- to lapilli-sized particles during 17-19 and 29 Apr.
Alert Level 3 (Yellow) on 29 April 2011
30 Apr 2011 1.2-6.4 NW and N SIGMET; SERNAGEOMIN No ash visible in satellite images.
01 May 2011 4-6.1 NW SIGMET No ash visible in satellite images.
02-03 May 2011 4.6-5.5 NE and E SIGMET; ODVAS Ash-and-gas plumes.
04-05 May 2011 4.3-7.3 NW and ENE SERNAGEOMIN; ODVAS Overflight by SERNAGEOMIN on 4 May. No ash visible in satellite images. Ashfall was reported by proximal towns (see text).
06 May 2011 4.6-5.5 SE GOES A thin plume of ash, steam, and gas.
07-10 May 2011 4.3-5.5 SE SERNAGEOMIN; ODVAS Gas-and-ash plumes visible from ODVAS web-camera. No ash visible in satellite images.
Alert Level 2 (Green) on 13 June 2011
24-25 Jun 2011 4.6 W, NE, and E SIGMET No ash visible in satellite images.
27 Jun 2011 na NW Buenos Aires VAAC Gas-and-steam plumes possibly containing ash.

Seismicity in April 2011 was dominated by volcano-tectonic (VT) events; 405 were detected, and locations were primarily concentrated in an area 25 km NE of the volcanic complex as well as along the N flank, ~6 km from the crater. Earthquakes were MC 2) and 30 long-period (LP) (RD 4 cm2) events were also detected that month. SERNAGEOMIN frequently reported seismic data in terms of RD, which is the value calculated from reduced displacements.

SERNAGEOMIN reported that ash emissions on 17, 18, and 29 April correlated with episodes of tremor with RD oscillating between 1 and 3 cm2. Overflights conducted on 26, 27, and 29 April determined that the active crater had not changed geometry and also appeared structurally stable (figure 7). The observers noted that tephra deposits from the previous explosions were notable SE and SW of the volcano. Deposits from the 29 April explosion were particularly easy to define during the overflight.

Figure (see Caption) Figure 7. This photo of Planchón-Peteroa was taken during one of a series of overflights during 26, 27, and 29 April 2011. A column of ash rose from the active crater and tephra had visibly covered much of the snow immediately SE and SW of the crater. Courtesy of Orlando Rivera, Exploraciones Mineras Andinas S.A.

Buenos Aires VAAC reported a significant ash plume detected by satellite images on 2 May 2011. The plume drifted between 4.9 and 5.5 km above sea level. toward the NE at ~7.7 meters/second. The OVDAS web-camera also captured images of the plume appearing diffuse and ~3.7 km wide. The VAAC noted that the plume rapidly dissipated during 1315-1845 local time.

The following day, continuous emissions of ash, steam, and gas were reported by SIGMET and the VAAC, although satellite images were not able to detect any emissions. By 1000, the VAAC reported SIGMET data for a plume that rose 4.6-5.5 km above sea level, moving E. At 1500, satellite images captured a diffuse and ~15 km wide ash plume. The plume drifted E at 5 meters/second and had risen 5.5 km above sea level.

Elevated activity during 4-5 May produced ashfall that reached the towns of Minera Río Teno (about 70 km NW) and Las Leñas (in Argentina, 45 km ENE). An overflight conducted by SERNAGEOMIN confirmed continued ash emissions and explosions that occurred approximately every 30 seconds. The explosive activity rarely produced plumes higher than 1,000 m above the crater. Gray ash deposits were visible downwind of the crater; the wind tended to disperse tephra widely and the observers noted that wind directions were frequently directed to the E, NE, NNE, NNE, and NW. During 30 April-8 May, SERNAGEOMIN noted that seismicity included tremor (RD of 2-3 cm2) and VT earthquakes (ML

Geologists from SERNAGEOMIN conducted an overflight of Planchón-Peteroa on 13 June 2011. RedMaule interviewed the observers who were on the helicopter which included representatives of SERNAGEOMIN and Oficina Nacional de Emergencia del Ministerio del Interior y Seguridad Pública (OMENI) as well as the mayor of Maule, Chile. The observers noted that persistent degassing continued; a low-level white plume (

Figure (see Caption) Figure 8. During an overflight of Planchón-Peteroa on 13 June 2011, few bare rocks were visible around the active crater due to snow-cover and ice; a low-level plume of white vapor rose from the crater. These six photos are stillshots taken from a video interview camera; note that the look direction varies in each photo with the approximate direction noted in the upper-left-hand corner of each photo. The tall peak of Planchón is visible in the background of the photo looking N. Courtesy of SERNAGEOMIN and RedMaule.

During 30 April-8 May, SERNAGEOMIN noted that seismicity included tremor (RD of 2-3 cm2) and VT earthquakes (ML

The Buenos Aires VAAC released an ash advisory on 29 October 2011. Satellite images could not detect ash, but a SIGMET was available. No other reports were issued by the VAAC through the end of this reporting period (December 2013).

Seismicity during 2012-2013. Monthly reports from SERNAGEOMIN highlighted seismicity and visual observations from a network of local web-cameras. Each report also included links for additional information from OMI (http://so2.gsfc.nasa.gov/pix/daily/0314/cchile_0314z.html) and MODVOLC (http://modis.higp.hawaii.edu/).

Activity during 2012. An approximate average of 400 earthquakes per month was detected in 2012, and roughly 75% of the events were VT while 25% were cataloged as LP events. The VT events were rarely larger than ML 3.0 and depths were in range of 4-10 km; these earthquakes were frequently clustered in groups that correlated with local faults. LP earthquakes were typically MD ≤2.0 and RD ≤2.9 cm2.

SERNAGEOMIN reported tremor in April, May, November, and December (table 4). One notable seismic swarm occurred on 5 April. Approximately 123 VT earthquakes were detected during 0230-0730; these events were located ~20 km NE of the crater with depthsL1.7.

Table 4. Tremor was detected during four months in 2012. RD is the value calculated from the reduced displacements of seismicity. Courtesy of SERNAGEOMIN.

Month RD in cm2
Apr 2012 1.1
May 2012 1.1
Nov 2012 0.6
Dec 2012 0.3

On 30 October 2012, the Oficina Nacional de Emergencia del Ministerio del Interior y Seguridad Pública (OMENI) released a report highlighting several communities that would be included in the early warning system designed to report flood risks. The towns included Curicó, Romeral, and Teno, in the region Maule, which are especially vulnerable due to proximity to Planchón-Peteroa's major drainages (figure 9).

Figure (see Caption) Figure 9. This Google Earth image includes the location of Planchón-Peteroa (lower right-hand corner), major towns, and primary roads. The background image is a composite of Landsat images from 2014. Note that the yellow line crossing through the volcanic center is the international border for Chile and Argentina. The scale is approximate. Courtesy of Google Earth.

On 6 November 2012, the network of web-cameras captured images of a white plume rising from the crater. At 1620, the persistent plume rose to ~1.3 km and drifted NE. SERNAGEOMIN noted that this activity was related to fumarolic emissions.

Activity during 2013. During 2013, an approximate average of 200 earthquakes was detected per month. Of these events, ~80% were VT and ~20% were LP. Magnitudes and depths of the VT earthquakes were comparable to the previous year, although ML values were sparsely reported. LP seismicity was reported in ML, instead of MD and values were in range of 0.3 to 2.0. The reduced displacements (RD) of LP events were frequently reported on a monthly basis with values in range 0.3-8.4.

Tremor was rarely detected in 2013. SERNAGEOMIN reported six episodes of tremor, but these only occurred in January and the calculated RD was 0.5 cm2.

Geologic Background. Planchón-Peteroa is an elongated complex volcano along the Chile-Argentina border with several overlapping calderas. Activity began in the Pleistocene with construction of the basaltic-andesite to dacitic Volcán Azufre, followed by formation of basaltic and basaltic-andesite Volcán Planchón, 6 km to the north. About 11,500 years ago, much of Azufre and part of Planchón collapsed, forming the massive Río Teno debris avalanche, which traveled 95 km to reach Chile's Central Valley. Subsequently, Volcán Planchón II was formed. The youngest volcano, andesitic and basaltic-andesite Volcán Peteroa, consists of scattered vents between Azufre and Planchón. Peteroa has been active into historical time and contains a small steaming crater lake. Historical eruptions from the complex have been dominantly explosive, although lava flows were erupted in 1837 and 1937.

Information Contacts: Observatorio Volcanológico de los Andes del Sur-Servicio Nacional de Geologia y Mineria (OVDAS-SERNAGEOMIN), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Buenos Aires Volcanic Ash Advisory Center (VAAC) (URL: http://www.smn.gov.ar/vaac/buenosaires/productos.php); and Oficina Nacional de Emergencia del Ministerio del Interior y Seguridad Pública (OMENI) (URL: http://www.onemi.cl/index.html).


Soufriere Hills (United Kingdom) — November 2013 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


By March 2014, an over 50-month-long decline in extrusion (Pause 5)

A partial dome collapse took place at Soufrière Hills on 11 February 2010 (BGVN 35:03), an event followed by a lack of easily measured dome growth during an interval that continued into at least April 2014. Despite a lack of significant extrusion into the dome, pyroclastic flows continued, as did rockfalls and volcano-tectonic (VT) earthquakes. MVO describes intervals of this nature as extrusive pauses or more simply pauses. Pauses have been diagnosed as a prevalent behavior since they began following an extrusive phase starting in mid-1995. Our last issue (BGVN 36:08) covered part of the still-ongoing pause.

The various phases of activity at Soufrière Hills Volcano (SHV) during 1 January 1992 to 30 April 2013 are summarized in table 72. The table comes from a Montserrat Volcano Observatory (MVO) report providing a synthesis of activity during ~6 months ending in April 2013, and making authoritative and instructive comparisons to the overall eruption (table 72).

Table 72. Inventory of behavioral phases observed at SHV between 1 January 1992 and 30 April 2013. Pause 5 continued into at least April 2014. Taken from the MVO Scientific Report for Volcanic Activity between 13 October 2012 and 30 April 2013.

Figure (see Caption)

In brief, table 72 documents that an increase in seismicity occurred from 1992 to 1995, followed by a phreatic eruptive phase starting in mid-1995. That episode was followed by intervals of extrusion, transition, and pause. Extrusive phases included dome growth and frequent pyroclastic flows. During transition phases, dome growth slowed, but the risk to areas near the volcano continued.

As noted above, pauses are characterized by much slower dome growth (if at all), yet residual activity. The current pause is the longest yet recorded since the eruption began in 1995. Pause 5 began on 12 February 2010, and as of March 2014 was over 50 months long.

MVO established three criteria that indicate the potential for future activity. These criteria include low frequency seismic swarms and tremors, daily SO2 fluxes above 50 tons/day, and significant ground deformation. Most of the data reported in this Bulletin came from MVO Scientific Reports from 1 November 2011 to 30 April 2012, 1 May 2012 to 12 October 2012, and 13 October 2012 to 30 April 2013.

Short, intense swarms of VT earthquakes have occurred at Soufrière Hills since late 2007. The smaller swarms are often described by MVO as strings.

The most notable activity since September 2011 included intense Volcanic Tectonic (VT) earthquake swarms during 22-23 March 2012. Two small strings of VT events occurred in early August 2012, a brief VT string occurred on 24 December 2012, and a few VT strings of earthquakes took place during 4-6 February 2013.

The seismic events of 22-23 March 2012 and August 2012 were followed by ash venting. The venting in March resulted in the formation of two new craters. One developed inside the 11 February 2010 dome collapse scar; the other was outside the collapse scar to the (figure 91).

Figure (see Caption) Figure 91. The craters at Soufrière Hills that formed following the intense VT earthquake swarms during 22-23 March 2012 are labeled in the above aerial photographs, taken by the Montserrat Volcano Observatory (MVO). The upper photo looks S into the 11 February 2010 collapse scar, and the lower photo looks E from above Gage's Mountain. Courtesy of MVO.

On 20 November 2012, images of the S flank of the dome revealed a pervasively fractured area below the S rim of the explosion crater. That area was considered a potential source for large rockfalls or pyroclastic flows.

During the increased fumarole activity on 4-5 February 2013, a new crater was excavated around a gas vent on the floor of the 11 February 2010 collapse scar. This crater was 15 to 20 m across and 5 to 10 m deep.

The Hazard Level remained at 2, indicating daytime (0800 to 1600) access to Zone C and daytime-transit-only in maritime zone W (located W of the volcano; boats may sail through the zone but must not stop). A map of the zones on the island appeared in BGVN (22:05) and is found as figure 22 above.

Activity during 1 November 2011 to 30 April 2012. Throughout the entire reporting period, seismicity remained comparable to previous pauses in lava extrusion. Four strings of VT events, in this case referred to as "spasmodic bursts," occurred in the course of the interval 1 November 2011 to 30 April 2012. In early December 2011, 10 events were recorded in a 3 minute span; the largest in terms of local magnitude (ML, discussed further below) was 3.2. The 10 events were interpreted as a sequence of triggered events.

Two intense VT swarms occurred on 23 March 2012, with almost 50 VT earthquakes in each swarm. The largest VT earthquake ever recorded at Soufrière Hills, with ML of 3.9, was recorded during these swarms. The second more intense swarm was followed by mild ash venting, seven hybrid earthquakes, and three long-period (LP) earthquakes. Topics such as ML are discussed in a subsection below on seismicity.

On 30 March 2012, MVO detected unusually low-level VT seismicity sustained over several hours. This was atypical activity, as seismicity at Soufrière Hills is normally characterized by the occasional appearance of short bursts of VT strings.

November-December 2012. Seven lahars were seismically detected in the Belham Valley region during 1 November 2011 to 30 April 2012. Five took place during November-December 2011. They were associated with rainfall above 10 mm/hr.

A pyroclastic flow occurred in Gages Valley on 9 March 2012. The flow originated close to the summit of Chance's Peak and traveled 1.5 km down the W flank into Spring Ghaut. Although direct volume measurements couldn't be made, an empirical relationship between runout and flow volume suggested the pyroclastic flow deposit volume to be 104 m3.

A slight increase in rockfall activity occurred before the VT swarms of 23 March 2012. There were minor rockfalls on the steep N, E, SW and W sectors of the dome, averaging to less than one rockfall per day. The SW side of the dome above Gingoe's Ghaut was unstable with noticeable rockfall activity.

SO2 flux averaged 420 tons/day, a value below the multi-year eruption's average. Following the March VT swarms, a daily flux of 4,600 tons was observed, the third highest recorded by the optical spectrometer (DOAS) since its installation in 2002. After 2010, SO2 cycle fluctuations were dominated by variation with timescales on the order of weeks to months.

On 17 February 2012, a fumarole at the E base of the 2006-2007 dome was observed for the first time by MVO staff. An area with yellow and white sulfur deposits was also discovered on this cliff. Around January 2012, this site had temperatures near 60°C, but temperatures in February ranged from 90° to 275°C.

Ground deformation recorded by a GPS network continued to show a trend of ongoing inflation, a behavior similar to previous pauses.

Activity from 1 May 2012 to 12 October 2012. Among 21 bursts of small earthquakes, the most notable occurred on 11 September 2012. Over the course of 13 hours, a low amplitude VT swarm resulted in 17 events, with the maximum ML around 1.3. Eight rockfalls and two hybrid earthquakes were noted alongside typical seismic activity.

On 13 and 14 October 2012, tropical storm Rafael triggered eight seismically detected lahars in this region. The most noteworthy were those in the Belham Valley. Also, the SO2 flux was slightly decreased from the previous reporting period, with an average of 280 tons/day.

As of October 2012, the E and W flanks had been determined to be the most unstable areas of the edifice, based on the presence of fresh rockfall deposits and pyroclastic flows. A large pyroclastic flow from the W flank could travel into Plymouth, the former capital destroyed by previous pyroclastic flows.

On 29 August 2012, a large pyroclastic flow originated at the 2006-2007 dome. This has been the largest pyroclastic flow in Tar River since the end of Phase 5 extrusion. Another pyroclastic flow occurred on 19 September 2012 in Gage's Valley. It originated from the steep slope adjacent to Chance's Peak and traveled about 1 kilometer. The sources of these pyroclastic flows can be viewed in figure 92.

Figure (see Caption) Figure 92. Two photographs showing features at Soufrière Hills. The photograph on the left shows the source of the 19 September 2012 pyroclastic flow. The photograph on the right shows the source and flow direction of the 29 August pyroclastic flow. Courtesy of MVO.

A 10-minute exposure photo taken on 6 September 2012 determined no changes in location and number of incandescent areas on the N flank. However, the large fumarole in the floor of the 11 February 2010 collapse scar reached temperatures of ~300°C, and was the source of weak ash venting on 8 August 2012. Thermal IR camera imaging, showed the brightest point of incandescence, which reached temperatures over 400°C, originated from a hole in the rear of the collapse scar.

It should be noted that from August 2012 to November 2012, measurements at three local continuous GPS (cGPS) stations, AIRS, SPRI, and MVO1, had slight shortening of the radial distance between stations and vents, which may indicate short-term reversal of the long term inflation trend. Conclusions remain speculative without testing with more data.

Activity from 13 October 2012 to 30 April 2013. The largest of seven VT strings occurred on 30 November 2012. That swarm had a total of 23 earthquakes, with ML of 2.1 or less. As mentioned in the introduction, a brief VT swarm occurred on 24 December 2012, but the four swarms of main interest followed on 3-5 February 2013. The most intense, with a total of 36 events in 27 minutes, occurred on 4 February, with a maximum ML of 2.6. As a result, there was an increase in temperature of fumaroles residing on the 11 February 2010 collapse scar. This escalation continued until later in the evening, and at 1750 loud roaring sounds were heard, accompanied by minor ash venting. Activity and temperature returned to background levels the next day. This activity was noticeably similar to the events of 23 March 2012. Both were preceded by smaller VT strings, about 11 hours earlier, and the most intense phase had a 10-minute duration. There followed a VT string on 5 February associated with minor ash venting from the main gas vent in the floor of the 11 February 2010 collapse scar, as shown in figure 93.

Figure (see Caption) Figure 93. Two thermal images, viewed from MVO and Jack Boy Hill, show the source of the ash venting on 5 February 2013, as well as a newly observed incandescence. Courtesy of MVO.

The next prominent seismic activity occurred on 15 and 19 April 2013. The earthquakes had ML of 3.0 and 2.9, respectively, and neither were part of a VT string. The last time isolated VT earthquakes occurred was 28 June and 9 October 2011. Beside VT strings, 15 low-frequency earthquakes, which encompassed long-period and hybrid events, were observed during the October 2012 to April 2013 recording period. As of April 2013, 51 VT strings have occurred, and 13 have directly preceded surface activity.

Heavy rainfall on 28 and 30 March 2013 generated large lahars, lasting several hours, in various valleys around Soufrière Hills, including Belham Valley. The average daily SO2 flux, as of April 2013, was 511 metric tons/day, with a high of 2,381 tons on 6 February 2013. This was the highest value observed since the ash venting of 23 March 2012. The connection between SO2 flux and VT activity is still not thoroughly understood, but there seems to be an increase of SO2 a few days before seismic events at Soufrière Hills.

Pyroclastic flow activity had followed the trends of previous pauses. On 28 March 2013, a pyroclastic flow traveled 1.5 km E through Tar River Valley. This pyroclastic flow began at a peeled-away slab of lava on the near-vertical E face of the dome. This was one of the largest pyroclastic flows since the start of Pause 5, and it removed a large portion of the lava slab on the 2006-2007 dome. This flank became heavily fractured as a result of weather and erosion, continued cooling, and contraction of the E flank of the dome above Tar River. Consequently, the Tar River side of the dome will likely be the source of future pyroclastic flow activity. Rockfall activity has been at its lowest since 10 February 2010, consistent with the stabilization of the dome over the past three years.

After 5 February 2013, temperatures in the collapse scar were ~100°C higher than previously recorded. That increase may be due to MVO's use of a new more sensitive IR camera (a FLIR T650sc), replacing their old (Mikron) camera. The new camera records temperatures that are corrected for atmospheric conditions.

Figure 94 emphasizes the difference in sensitivity between the two cameras. However, the distance at which these images were captured, about 5.7 km from the dome, results in unreliable temperature readings. This is because infrared light is absorbed, scattered, and refracted by dust, air, and water (in solid, liquid, or gaseous states). Variables such as solar reflection, heat from direct sunlight, condensates, and high concentrations of SO2 in the atmosphere can also result in errors in image readings.

Figure (see Caption) Figure 94. For Soufrière Hills, a juxtaposition of thermal images to highlight the difference in resolution and displays between the old infrared-detecting (IR) camera (left) and the more sensitive and accurate new one (right). Although there are temperature scales to the right of each image (22.4-32.4 on the scale at right), they are not applicable in this instance owing to multiple factors (see text). Even at this distance, IR images give scientists greater clarity on dome behavior. Despite the loss of the temperature scale, the images serve as an important tool for monitoring the state of the dome. Both IR photos taken during early 2013. Courtesy of MVO.

According to Adam J. Stinton, a volcanologist at MVO, the new camera produces images twice the size of the older camera due to a larger internal sensor, and therefore the right-hand image was scaled down to a comparable size. Thermal imaging technology works by recording the intensity of radiation in the infrared part of the electromagnetic spectrum and converting it to a radiometric image, with every pixel in the image conveying a temperature measurement.

Using the FLIR camera, a strong fumarole on the summit of the 2006-2007 dome was recorded on 15 March 2013, the first time this fumarole was ever imaged. Its temperature was between 250 and 260°C. No other new thermal features or incandescence had been recorded during this period.

As of April 2013, the trend of long-term edifice inflation continued. This suggested that the magmatic system is still actively deforming surficial areas. MVO observed similar deformation signals during previous pauses in extrusion.

Activity during April 2013 to March 2014. On 14 January 2014, a helicopter assessment of several groups of fumaroles revealed temperatures of 140-340°C within the summit crater. These fumaroles were observed for the first time since 2011. Aside from this detection, there has been a low level of activity at Soufrière Hills, including occasional rockfalls and seismic activity.

Background on seismicity. According to Druitt and Kokelaar (2002), hybrid earthquakes are long-period earthquakes located at (shallow) depths of less than 2 km. LP earthquakes, on the other hand, are widely interpreted as earthquakes associated with the movement of pressurized fluids (eg., BGVN 20:08).

According to MVO, using ML offers possible advantages when calculating cumulative VT energy. The Gutenberg-Richter magnitude-energy relationship portrays an earthquake's size based on the amplitude of the resulting waves recorded on a seismogram. The concept is that the wave amplitude portrays the earthquake's size once the amplitudes are corrected for the decrease in magnitude with distance owing to geometric spreading and attenuation (Stein and Wysession, 2003). Local magnitude (often also termed Richter magnitude or the Richter scale). MVO employs the following (base 10) logarithmic equation, which associates ML to cumulative VT energy, E, as follows: Log E = 1.5 × ML + 11.8

MVO notes that this equation is a reliable calculation of cumulative energy, as opposed to amplitude measurements at a single station. Amplitude measurement data are easily affected by variables such as data gaps. As further background, magnitudes can be negative for very small displacements (eg. a small rockfall). Stein and Wysession (2003, p. 263) make the point that seismic magnitude scales are logarithmic, ". . . so an increase from magnitude "5" to "6," indicates a ten-fold increase in seismic wave amplitude. Measured displacements range more than 10 units because the displacements measured by seismometers span more than a factor of 1010." In practice, the amplitude is measured in microns of displacement after the effects of the seismometer are removed. Different magnitude scales (eg., ML, mb, Ms, Mw, etc.) yield different values (Stein and Wysession, 2003).

References: Cole, P., Bass, V., Christopher, T., Melander, S., Pascal, K., Smith, P., Stewart, R., Stinton, A., and Syers, R., undated, MVO Scientific Report for Volcanic Activity Between 1 May 2012 and 12 October 2012, Open File Report OFR 12-02; Montserrat Volcano Observatory, 47 pp. (URL: http://www.mvo.ms/pub/Open_File_Reports/MVO_OFR_12_02-MVO_Scientific_Report.pdf)

Cole, P., Bass, V., Christopher, Odhert, H., Smith, P., Stewart, R., Stinton, A., Syers, R., and Williams, P., undated, MVO Scientific Report for Volcanic Activity Between 1 November 2011 and 30 April 2012. Montserrat Volcano Observatory, (URL: http://www.mvo.ms/pub/Open_File_Reports/MVO_OFR_12_01-MVO_Scientific_Report.pdf)

Druitt, T. and Kokelaar, B., 2002, The Eruption of Soufriere Hills Volcano, Montserrat, form 1995 to 1999, Issue 21. Geological Society Memoir No. 21. UK: The Geological Society Publishing House, 2002.

Stein, S. and Wysession, M., 2003, An Introduction to Seismology, Earthquakes and Earth Structure, 2003, Blackwell Publishing, Oxford, 498 pp. [ISBN 0-86542- 078-5]

Stewart, R., Bass, V., Christopher, T., Cole, P., Dondin, F., Higgins, M., Joseph, E., Pascal, K., Smith, P., Stinton, A., Syers, R., and Williams, P., (27 May) 2013, MVO Scientific Report for Volcanic Activity Between 13 October 2012 and 30 April 2013, Open File Report, OFR 13-06. Montserrat Volcano Observatory. (URL: http://www.mvo.ms/pub/Open_File_Reports/MVO_OFR_13_06-Six_monthly_report.pdf )

Geologic Background. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Information Contacts: Montserrat Volcano Observatory (MVO), Fleming, Montserrat, West Indies (URL: http://www.mvo.ms/); Washington Volcanic Ash Advisory Center (VAAC); and Adam Stinton, MVO.


Yasur (Vanuatu) — November 2013 Citation iconCite this Report

Yasur

Vanuatu

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

All times are local (unless otherwise noted)


Explosive activity during May, August, and November 2013

Our previous report from May 2013 (BGVN 38:05) noted Strombolian activity, including volcanic bombs in July 2012 and ashfall and volcanic bombs in April and May 2013. The Vanuatu Geohazards Observatory (VGO) bulletin from 28 May 2013 noted that Yasur's explosive activity had increased slightly, compared to the recent past. The activity included Strombolian explosions (figure 43) and ash and steam plumes. This report discusses activity from June 2013 through February 2014, along with photographs taken in May 2013. A map of Vanuatu and nearby countries was provided in BGVN 35:06.

Figure (see Caption) Figure 43. Strombolian activity from Yasur recorded during May 2013. Courtesy of Volcano Discovery (Dietmar Berendes).

Observations and seismic data from early to mid-August 2013 suggested that explosive activity of the volcano had decreased slightly during that time. Explosions were weaker and less frequent. Therefore, on 29 August 2013, the VGO decreased the Alert Level from 2, where it had been since early April 2013, to 1. Level 1 (on a scale of 0-4) indicates "increased activity [but] danger near crater only". From 29 August 2013 until at least February 2014, the Alert Level has remained at 1.

Hazard zones at Yasur are indicated in figure 44. VGO has warned visitors that ejected volcanic bombs could hit the summit area, the tourist walk, and parking area.

Figure (see Caption) Figure 44. This danger map ('Denja Map') of Tanna Island containing Yasur volcano shows Red, Yellow, and Green zones to warn visitors and civilians of ashfall and other hazards. Yasur volcano is near the eastern end of the red, highest-risk zone. Map key and title are in a language with phonetic similarities to English that evolved with contact from traders (a lingua franca) but many other languages also remain in use in Vanuatu. Ash could likely fall well W of Yasur due to trade winds from the ESE. This image is of low to moderate resolution and some symbols are illegible. Courtesy of Vanuatu Geohazards Observatory.

Observations and seismic data from early to mid-August 2013 suggested that explosive activity of the volcano had decreased slightly during that time. Explosions were weaker and less frequent. Therefore, on 29 August 2013, the VGO decreased the Alert Level from 2, where it had been since early April 2013, to 1. Level 1 (on a scale of 0-4) indicates "increased activity [but] danger near crater only". From 29 August 2013 until at least February 2014, the Alert Level has remained at 1.

According to John Search, who has led tours of the volcano since 1998, activity increased beginning October 2013. A large ash emission caused widespread damage to vegetation on Tanna Island, and ashfall was reported on Erromango Island, 150 km N of Yasur. On the evening of 3 November 2013, Search witnessed large Strombolian explosions. These explosions ejected volcanic bombs, up to 4 m in diameter, 250 m from the vent, putting visitors at risk. According to Search, the explosions were some of the largest at Yasur since 1995.

On 19 November 2013, VGO reported that a new phase of ash emissions began on 3 November. The explosive intensity remained low.

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: Vanuatu Geohazards Observatory, Department of Geology, Mines and Water Resources of Vanuatu (URL: http://www.geohazards.gov.vu); John Seach, Volcanolive.com (URL: Volcanolive.com/Yasur.html); and Volcano Discovery (www.volcanodiscovery.com).

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