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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

Sangay (Ecuador) Ash plumes, lava flows, pyroclastic flows, and lahars during July-December 2020; larger explosions in September

Ebeko (Russia) Continued explosions, ash plumes, and ashfall; June-November 2020

Kuchinoerabujima (Japan) Intermittent thermal anomalies and small eruptions in May and August 2020

Raung (Indonesia) Explosions with ash plumes and a thermal anomaly at the summit crater, July-October 2020

Nyamuragira (DR Congo) Numerous thermal anomalies and gas emissions from the lava lake through November 2020

Sinabung (Indonesia) Explosions begin again on 8 August 2020; dome growth confirmed in late September

Heard (Australia) Persistent thermal anomalies in the summit crater from June through October 2020

Sabancaya (Peru) Daily explosions produced ash plumes, SO2 plumes, and thermal anomalies during June-September 2020

Rincon de la Vieja (Costa Rica) Frequent small phreatic explosions with intermittent ash plumes during April-September 2020

Fuego (Guatemala) Daily explosions, ash emissions, and block avalanches during August-November 2020

Kikai (Japan) Explosion on 6 October 2020 and thermal anomalies in the crater

Manam (Papua New Guinea) Intermittent ash plumes, thermal anomalies, and SO2 emissions in April-September 2020



Sangay (Ecuador) — January 2021 Citation iconCite this Report

Sangay

Ecuador

2.005°S, 78.341°W; summit elev. 5286 m

All times are local (unless otherwise noted)


Ash plumes, lava flows, pyroclastic flows, and lahars during July-December 2020; larger explosions in September

Sangay is one of the most active volcanoes in Ecuador with the current eruptive period continuing since 26 March 2019. Activity at the summit crater has been frequent since August 1934, with short quiet periods between events. Recent activity has included frequent ash plumes, lava flows, pyroclastic flows, and lahars. This report summarizes activity during July through December 2020, based on reports by Ecuador's Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN), ash advisories issued by the Washington Volcanic Ash Advisory Center (VAAC), webcam images taken by Servicio Integrado de Seguridad ECU911, and various satellite data.

Overall activity remained elevated during the report period. Recorded explosions were variable during July through December, ranging from no explosions to 294 reported on 4 December (figure 80), and dispersing mostly to the W and SW. SO2 was frequently detected using satellite data (figure 81) and was reported several times to be emitting between about 770 and 2,850 tons/day. Elevated temperatures at the crater and down the SE flank were frequently observed in satellite data (figure 82), and less frequently by visual observation of incandescence. Seismic monitoring detected lahars associated with rainfall events remobilizing deposits emplaced on the flanks throughout this period.

Figure (see Caption) Figure 80. A graph showing the daily number of explosions at Sangay recorded during July through December 2020. Several dates had no recorded explosions due to lack of seismic data. Data courtesy of IG-EPN (daily reports).
Figure (see Caption) Figure 81. Examples of stronger SO2 plumes from Sangay detected by the Sentinel 5P/TROPOMI instrument, with plumes from Nevado del Ruiz detected to the north. The image dates from left to right are 31 August 2020, 17 September 2020, 1 October 2020 (top row), 22 November 2020, 3 December 2020, 14 December 2020 (bottom row). Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 82. This log radiative power MIROVA plot shows thermal output at Sangay during February through December 2020. Activity was relatively constant with increases and decreases in both energy output and the frequency of thermal anomalies detected. Courtesy of MIROVA.

Activity during July-August 2020. During July activity continued with frequent ash and gas emission recorded through observations when clouds weren’t obstructing the view of the summit, and Washington VAAC alerts. There were between one and five VAAC alerts issued most days, with ash plumes reaching 570 to 1,770 m above the crater and dispersing mostly W and SE, and NW on two days (figure 83). Lahar seismic signals were recorded on the 1st, 7th, three on the 13th, and one on the 19th.

Figure (see Caption) Figure 83. Gas and ash plumes at Sangay during July 2020, at 0717 on the 17th, at 1754 on the 18th, and at 0612 on the 25th. Bottom picture taken from the Macas ECU 911 webcam. All images courtesy of IG-EPN daily reports.

During August there were between one and five VAAC alerts issued most days, with ash plumes reaching 600 to 2,070 m above the crater and predominantly dispersing W, SW, and occasionally to the NE, S, and SE (figure 84). There were reports of ashfall in the Alausí sector on the 24th. Using seismic data analysis, lahar signals were identified after rainfall on 1, 7, 11-14, and 21 August. A lava flow was seen moving down the eastern flank on the night of the 15th, resulting in a high number of thermal alerts. A pyroclastic flow was reported descending the SE flank at 0631 on the 27th (figure 85).

Figure (see Caption) Figure 84. This 25 August 2020 PlanetScope satellite image of Sangay in Ecuador shows an example of a weak gas and ash plume dispersing to the SW. Courtesy of Planet Labs.
Figure (see Caption) Figure 85. A pyroclastic flow descends the Sangay SE flank at 0631 on 27 August 2020. Webcam by ECU911, courtesy of courtesy of IG-EPN (27 August 2020 report).

Activity during September-October 2020. Elevated activity continued through September with two significant increases on the 20th and 22nd (more information on these events below). Other than these two events, VAAC reports of ash plumes varied between 1 and 5 issued most days, with plume heights reaching between 600 and 1,500 m above the crater. Dominant ash dispersal directions were W, with some plumes traveling SE, S, SE, NE, and NW. Lahar seismic signals were recorded after rainfall on 1, 2, 5, 8-10, 21, 24, 25, 27, and 30 September. Pyroclastic flows were reported on the 19th (figure 86), and incandescent material was seen descending the SE ravine on the 29th. There was a significant increase in thermal alerts reported throughout the month compared to the July-August period, and Sentinel-2 thermal satellite images showed a lava flow down the SE flank (figure 87).

Figure (see Caption) Figure 86. Pyroclastic flows descended the flank of Sangay on 19 (top) and 20 (bottom) September 2020. Webcam images by ECU911 from the city of Macas, courtesy of IG-EPN (14 August 2018 report).
Figure (see Caption) Figure 87. The thermal signature of a lava flow is seen on SW flank of Sangay in this 8 September 2020 Sentinel-2 thermal satellite image, indicated by the white arrow. False color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Starting at 0420 on the morning of 20 September there was an increase in explosions and emissions recorded through seismicity, much more energetic than the activity of previous months. At 0440 satellite images show an ash plume with an estimated height of around 7 km above the crater. The top part of the plume dispersed to the E and the rest of the plume went W. Pyroclastic flows were observed descending the SE flank around 1822 (figure 88). Ash from remobilization of deposits was reported on the 21st in the Bolívar, Chimborazo, Los Ríos, Guayas and Santa Elena provinces. Ash and gas emission continued, with plumes reaching up to 1 km above the crater. There were seven VAAC reports as well as thermal alerts issued during the day.

Figure (see Caption) Figure 88. An eruption of Sangay on 22 September 2020 produced a pyroclastic flow down the SE flank and an ash plume that dispersed to the SW. PlanetScope satellite image courtesy of Planet Labs.

Ash plumes observed on 22 September reached around 1 km above the crater and dispersed W to NW. Pyroclastic flows were seen descending the SE flank (figure 89) also producing an ash plume. A BBC article reported the government saying 800 km2 of farmland had experienced ashfall, with Chimborazo and Bolívar being the worst affected areas (figure 90). Locals described the sky going dark, and the Guayaquil was temporarily closed. Ash plume heights during the 20-22 were the highest for the year so far (figure 91). Ash emission continued throughout the rest of the month with another increase in explosions on the 27th, producing observed ash plume heights reaching 1.5 km above the crater. Ashfall was reported in San Nicolas in the Chimborazo Province in the afternoon of the 30th.

Figure (see Caption) Figure 89. A pyroclastic flow descending the flank of Sangay on 22 September 2020. Webcam image by ECU911 from the city of Macas, courtesy of IG-EPN (Sangay Volcano Special Report - 2020 - No 5, 22 September 2020).
Figure (see Caption) Figure 90. Ashfall from an eruption at Sangay on 22 September 2020 affected 800 km2 of farmland and nearby communities. Images courtesy of EPA and the Police of Ecuador via Reuters (top-right), all via the BBC.
Figure (see Caption) Figure 91. Ash plume heights (left graph) at Sangay from January through to late September, with the larger ash plumes during 20-22 September indicated by the red arrow. The dominant ash dispersal direction is to the W (right plot) and the average speed is 10 m/s. Courtesy of IG-EPN (Sangay Volcano Special Report - 2020 - No 5, 22 September 2020).

Thermal alerts increased again through October, with a lava flow and/or incandescent material descending the SE flank sighted throughout the month (figure 92). Pyroclastic flows were seen traveling down the SE flank during an observation flight on the 6th (figure 93). Seismicity indicative of lahars was reported on 1, 12, 17, 19, 21, 23, 24, and 28 October associated with rainfall remobilizing deposits. The Washington VAAC released one to five ash advisories most days, noting plume heights of 570-3,000 m above the crater; prevailing winds dispersed most plumes to the W, with some plumes drifting NW, N, E to SE, and SW. Ashfall was reported in Alausí (Chimborazo Province) on the 1st and in Chunchi canton on the 10th. SO2 was recorded towards the end of the month using satellite data, varying between about 770 and 2,850 tons on the 24th, 27th, and 29th.

Figure (see Caption) Figure 92. A lava flow descends the SE flank of Sangay on 2 October 2020. Webcam images courtesy of ECU 911.
Figure (see Caption) Figure 93. A pyroclastic flow descends the Sangay SE flank was seen during an IG-EPN overflight on 6 October 2020. Photo courtesy of S. Vallejo, IG-EPN.

Activity during November-December 2020. Frequent ash emission continued through November with between one and five Washington VAAC advisories issued most days (figure 94). Reported ash and gas plume heights varied between 570 and 2,700 m above the crater, with winds dispersing plumes in all directions. Thermal anomalies were detected most days, and incandescent material from explosions was seen on the 26th. Seismicity indicating lahars was registered on nine days between 15 and 30 November, associated with rainfall events.

Figure (see Caption) Figure 94. Examples of gas and ash plumes at Sangay during November 2020. Webcam images were published in IG-EPN daily activity reports.

Lahar signals associated with rain events continued to be detected on ten out of the first 18 days of November. Ash emissions continued through December with one to five VAAC alerts issued most days. Ash plume heights varied from 600 to 1,400 m above the crater, with the prevailing wind direction dispersing most plumes W and SW (figure 95). Thermal anomalies were frequently detected and incandescent material was observed down the SE flank on the 3rd, 14th, and 30th, interpreted as a lava flow and hot material rolling down the flank. A webcam image showed a pyroclastic flow traveling down the SE flank on the 2nd (figure 96). Ashfall was reported on the 10th in Capzol, Palmira, and Cebadas parishes, and in the Chunchi and Guamote cantons.

Figure (see Caption) Figure 95. Examples of ash plumes at Sangay during ongoing persistent activity on 9, 10, and 23 December 2020. Webcam images courtesy of ECU 911.
Figure (see Caption) Figure 96. A nighttime webcam image shows a pyroclastic flow descending the SE flank of Sangay at 2308 on 2 December 2020. Image courtesy of ECU 911.

Geologic Background. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Information Contacts: Instituto Geofísico (IG-EPN), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec); ECU911, Servicio Integrado de Seguridad ECU911, Calle Julio Endara s / n. Itchimbía Park Sector Quito – Ecuador. (URL: https://www.ecu911.gob.ec/; Twitter URL: https://twitter.com/Ecu911Macas/); 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/); 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/); Planet Labs, Inc. (URL: https://www.planet.com/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); BBC News “In pictures: Ash covers Ecuador farming land” Published 22 September 2020 (URL: https://www.bbc.com/news/world-latin-america-54247797).


Ebeko (Russia) — December 2020 Citation iconCite this Report

Ebeko

Russia

50.686°N, 156.014°E; summit elev. 1103 m

All times are local (unless otherwise noted)


Continued explosions, ash plumes, and ashfall; June-November 2020

Volcanism at Ebeko, located on the N end of the Paramushir Island in the Kuril Islands, has been ongoing since October 2016, characterized by frequent moderate explosions, ash plumes, and ashfall in Severo-Kurilsk (7 km ESE) (BGVN 45:05). Similar activity during this reporting period of June through November 2020 continues, consisting of frequent explosions, dense ash plumes, and occasional ashfall. Information for this report primarily comes from the Kamchatka Volcanic Eruptions Response Team (KVERT) and satellite data.

Activity during June was characterized by frequent, almost daily explosions and ash plumes that rose to 1.6-4.6 km altitude and drifted in various directions, according to KVERT reports and information from the Tokyo VAAC advisories using HIMAWARI-8 satellite imagery and KBGS (Kamchatka Branch of the Geophysical Service) seismic data. Satellite imagery showed persistent thermal anomalies over the summit crater. On 1 June explosions generated an ash plume up to 4.5 km altitude drifting E and S, in addition to several smaller ash plumes that rose to 2.3-3 km altitude drifting E, NW, and NE, according to KVERT VONA notices. Explosions on 11 June generated an ash plume that rose 2.6 km altitude and drifted as far as 85 km N and NW. Explosions continued during 21-30 June, producing ash plumes that rose 2-4 km altitude, drifting up to 5 km in different directions (figure 26); many of these eruptive events were accompanied by thermal anomalies that were observed in satellite imagery.

Figure (see Caption) Figure 26. Photo of a dense gray ash plume rising from Ebeko on 22 June 2020. Photo by L. Kotenko (color corrected), courtesy of IVS FEB RAS, KVERT.

Explosions continued in July, producing ash plumes rising 2-5.2 km altitude and drifting for 3-30 km in different directions. On 3, 6, 15 July explosions generated an ash plume that rose 3-4 km altitude that drifted N, NE, and SE, resulting in ashfall in Severo-Kurilsk. According to a Tokyo VAAC advisory, an eruption on 4 July produced an ash plume that rose up to 5.2 km altitude drifting S. On 22 July explosions produced an ash cloud measuring 11 x 13 km in size and that rose to 3 km altitude drifting 30 km SE. Frequent thermal anomalies were identified in satellite imagery accompanying these explosions.

In August, explosions persisted with ash plumes rising 1.7-4 km altitude drifting for 3-10 km in multiple directions. Intermittent thermal anomalies were detected in satellite imagery, according to KVERT. On 9 and 22 August explosions sent ash up to 2.5-3 km altitude drifting W, S, E, and SE, resulting in ashfall in Severo-Kurilsk. Moderate gas-and-steam activity was reported occasionally during the month.

Almost daily explosions in September generated dense ash plumes that rose 1.5-4.3 km altitude and drifted 3-5 km in different directions. Moderate gas-and-steam emissions were often accompanied by thermal anomalies visible in satellite imagery. During 14-15 September explosions sent ash plumes up to 2.5-3 km altitude drifting SE and NE, resulting in ashfall in Severo-Kurilsk. On 22 September a dense gray ash plume rose to 3 km altitude and drifted S. The ash plume on 26 September was at 3.5 km altitude and drifted SE (figure 27).

Figure (see Caption) Figure 27. Photos of dense ash plumes rising from Ebeko on 22 (left) and 26 (right) September 2020. Photos by S. Lakomov (color corrected), IVS FEB RAS, KVERT.

During October, near-daily ash explosions continued, rising 1.7-4 km altitude drifting in many directions. Intermittent thermal anomalies were identified in satellite imagery. During 7-8, 9-10, and 20-22 October ashfall was reported in Severo-Kurilsk.

Explosions in November produced dense gray ash plumes that rose to 1.5-5.2 km altitude and drifted as far as 5-10 km, mainly NE, SE, E, SW, and ENE. According to KVERT, thermal anomalies were visible in satellite imagery throughout the month. On clear weather days on 8 and 11 November Sentinel-2 satellite imagery showed ashfall deposits SE of the summit crater from recent activity (figure 28). During 15-17 November explosions sent ash up to 3.5 km altitude drifting NE, E, and SE which resulted in ashfall in Severo-Kurilsk on 17 November. Similar ashfall was observed on 22-24 and 28 November due to ash rising to 1.8-3 km altitude (figure 29). Explosions on 29 November sent an ash plume up to 4.5 km altitude drifting E (figure 29). A Tokyo VAAC advisory reported that an ash plume drifting SSE on 30 November reached an altitude of 3-5.2 km.

Figure (see Caption) Figure 28. Sentinel-2 satellite imagery of a gray-white gas-and-ash plume at Ebeko on 8 (left) and 11 (right) November 2020, resulting in ashfall (dark gray) to the SE of the volcano. Images using “Natural Color” rendering (bands 4, 3, 2), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 29. Photos of continued ash explosions from Ebeko on 28 October (left) and 29 November (right) 2020. Photos by S. Lakomov (left) and L. Kotenko (right), courtesy of IVS FEB RAS, KVERT.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows a pulse in low-power thermal activity beginning in early June through early August (figure 30). On clear weather days, the thermal anomalies in the summit crater are observed in Sentinel-2 thermal satellite imagery, accompanied by occasional white-gray ash plumes (figure 31). Additionally, the MODVOLC algorithm detected a single thermal anomaly on 26 June.

Figure (see Caption) Figure 30. A small pulse in thermal activity at Ebeko began in early June and continued through early August 2020, according to the MIROVA graph (Log Radiative Power). The detected thermal anomalies were of relatively low power but were persistent during this period. Courtesy of MIROVA.
Figure (see Caption) Figure 31. Sentinel-2 satellite imagery showed gray ash plumes rising from Ebeko on 11 June (top left) and 16 July (bottom left) 2020, accompanied by occasional thermal anomalies (yellow-orange) within the summit crater, as shown on 24 June (top right) and 25 August (bottom right). The ash plume on 11 June drifted N from the summit. Images using “Natural Color” rendering (bands 4, 3, 2) on 11 June (top left) and 16 July (bottom left) and the rest have “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

Geologic Background. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

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/); Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences (KB GS RAS) (URL: http://www.emsd.ru/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); 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).


Kuchinoerabujima (Japan) — November 2020 Citation iconCite this Report

Kuchinoerabujima

Japan

30.443°N, 130.217°E; summit elev. 657 m

All times are local (unless otherwise noted)


Intermittent thermal anomalies and small eruptions in May and August 2020

Kuchinoerabujima encompasses a group of young stratovolcanoes located in the northern Ryukyu Islands. All historical eruptions have originated from the Shindake cone, with the exception of a lava flow that originated from the S flank of the Furudake cone. The current eruptive period began in January 2020 and has been characterized by small explosions, ash plumes, ashfall, a pyroclastic flow, and gas-and-steam emissions. This report covers activity from May to October 2020, which includes small explosions, ash plumes, crater incandescence, and gas-and-steam emissions. The primary source of information for this report comes from monthly and annual reports from the Japan Meteorological Agency (JMA) and advisories from the Tokyo Volcanic Ash Advisory Center (VAAC).

Volcanism at Kuchinoerabujima remained relatively low during May through October 2020, according to JMA. During this time, SO2 emissions ranged from 40 to 3,400 tons/day; occasional gas-and-steam emissions were reported, rising to a maximum of 900 m above the crater. Sentinel-2 satellite images showed a particularly strong thermal anomaly in the Shindake crater on 1 May (figure 10). The thermal anomaly decreased in power after 1 May and was only visible on clear weather days, which included 19 August and 3 and 13 October. Global Navigation Satellite System (GNSS) observations identified continued slight inflation at the base of the volcano during the entire reporting period.

Figure (see Caption) Figure 10. Sentinel-2 thermal satellite images showed a strong thermal anomaly (bright yellow-orange) in the Shindake crater at Kuchinoerabujima on 1 May 2020 (top left). Weaker thermal anomalies were also seen in the Shindake crater during 19 August (top right) and 3 (bottom left) and 13 (bottom right) October 2020. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images; courtesy of Sentinel Hub Playground.

Three small eruptions were detected by JMA on 5, 6, and 13 May, which produced an ash plume rising 500 m above the crater on each day, resulting in ashfall on the downwind flanks. Incandescence was observed at night using a high-sensitivity surveillance camera (figure 11). On 5 and 13 May the Tokyo VAAC released a notice that reported ash plumes rising 0.9-1.2 km altitude, drifting NE and S, respectively. On 20 May weak fumaroles were observed on the W side of the Shindake crater. The SO2 emissions ranged from 700-3,400 tons/day.

Figure (see Caption) Figure 11. Webcam images of an eruption at Kuchinoerabujima on 6 May 2020 (top), producing a gray ash plume that rose 500 m above the crater. Crater incandescence was observed from the summit crater at night on 25 May 2020 (bottom). Courtesy of JMA (Monthly bulletin report 509, May 2020).

Activity during June and July decreased compared to May, with gas-and-steam emissions occurring more prominently. On 22 June weak incandescence was observed, accompanied by white gas-and-steam emissions rising 700 m above the crater. Weak crater incandescence was also seen on 25 June. The SO2 emissions measured 400-1,400 tons/day. White gas-and-steam emissions were again observed on 31 July rising to 800 m above the crater. The SO2 emissions had decreased during this time to 300-700 tons/day.

According to JMA, the most recent eruptive event occurred on 29 August at 1746, which ejected bombs and was accompanied by some crater incandescence, though the eruptive column was not visible due to the cloud cover. However, white gas-and-steam emissions could be seen rising 1.3 km above the Shindake crater drifting SW. The SO2 emissions measured 200-500 tons/day. During August, the number of volcanic earthquakes increased significantly to 1,032, compared to the number in July (36).

The monthly bulletin for September reported white gas-and-steam emissions rising 900 m above the crater on 9 September and on 11 October the gas-and-steam emissions rose 600 m above the crater. Seismicity decreased between September and October from 1,920 to 866. The SO2 emissions continued to decrease compared to previous months, totaling 80-400 tons/day in September and 40-300 tons/day in October.

Geologic Background. A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km W of Yakushima. The Furudake, Shindake, and Noikeyama cones were erupted from south to north, respectively, forming a composite cone with multiple craters. All historical eruptions have occurred from Shindake, although a lava flow from the S flank of Furudake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shindake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Raung (Indonesia) — December 2020 Citation iconCite this Report

Raung

Indonesia

8.119°S, 114.056°E; summit elev. 3260 m

All times are local (unless otherwise noted)


Explosions with ash plumes and a thermal anomaly at the summit crater, July-October 2020

A massive stratovolcano in easternmost Java, Raung has over sixty recorded eruptions dating back to the late 16th Century. Explosions with ash plumes, Strombolian activity, and lava flows from a cinder cone within the 2-km-wide summit crater have been the most common activity. Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) has installed webcams to monitor activity in recent years. An eruption from late 2014 through August 2015 produced a large volume of lava within the summit crater and formed a new pyroclastic cone in the same location as the previous one. The eruption that began in July 2020 is covered in this report with information provided by PVMBG, the Darwin Volcanic Ash Advisory Center (VAAC), and several sources of satellite data.

The 2015 eruption was the largest in several decades; Strombolian activity was reported for many months and fresh lava flows covered the crater floor (BGVN 45:09). Raung was quiet after the eruption ended in August of that year until July of 2020 when seismicity increased on 13 July and brown emissions were first reported on 16 July. Tens of explosions with ash emissions were reported daily during the remainder of July 2020. Explosive activity decreased during August, but thermal activity didn’t decrease until mid-September. The last ash emissions were reported on 3 October and the last thermal anomaly in satellite data was recorded on 7 October 2020.

Eruption during July-October 2020. No further reports of activity were issued after August 2015 until July 2020. Clear Google Earth imagery from October 2017 and April 2018 indicated the extent of the lava from the 2015 eruption, but no sign of further activity (figure 31). By August 2019, many features from the 2015 eruption were still clearly visible from the crater rim (figure 32).

Figure (see Caption) Figure 31. Little change can be seen at the summit of Raung in Google Earth images dated 19 October 2017 (left) and 28 April 2018 (right). The summit crater was full of black lava flows from the 2015 eruption. Courtesy of Google Earth.
Figure (see Caption) Figure 32. A Malaysian hiker celebrated his climbing to the summit of Raung on 30 August 2019. Weak fumarolic activity was visible from the base of the breached crater of the cone near the center of the summit crater, and many features of the lava flow that filled the crater in 2015 were still well preserved. Courtesy of MJ.

PVMBG reported that the number and type of seismic events around the summit of Raung increased beginning on 13 July 2020, and on 16 July the height of the emissions from the crater rose to 100 m and the emission color changed from white to brown. About three hours later the emissions changed to gray and white. The webcams captured emissions rising 50-200 m above the summit that included 60 explosions of gray and reddish ash plumes (figure 33). The Raung Volcano Observatory released a VONA reporting an explosion with an ash plume that drifted N at 1353 local time (0653 UTC). The best estimate of the ash cloud height was 3,432 m based on ground observation. They raised the Aviation Color Code from unassigned to Orange. About 90 minutes later they reported a second seismic event and ash cloud that rose to 3,532 m, again based on ground observation. The Darwin VAAC reported that neither ash plume was visible in satellite imagery. The following day, on 17 July, PVMBG reported 26 explosions between midnight and 0600 that produced brown ash plumes which rose 200 m above the crater. Based on these events, PVMBG raised the Alert Level of Raung from I (Normal) to II (Alert) on a I-II-III-IV scale. By the following day they reported 95 explosive seismic events had occurred. They continued to observe gray ash plumes rising 100-200 m above the summit on clear days and 10-30 daily explosive seismic events through the end of July; plume heights dropped to 50-100 m and the number of explosive events dropped below ten per day during the last few days of the month.

Figure (see Caption) Figure 33. An ash plume rose from the summit of Raung on 16 July 2020 at the beginning of a new eruption. The last previous eruption was in 2015. Courtesy of Volcano Discovery and PVMBG.

After a long period of no activity, MIROVA data showed an abrupt return to thermal activity on 16 July 2020; a strong pulse of heat lasted into early August before diminishing (figure 34). MODVOLC thermal alert data recorded two alerts each on 18 and 20 July, and one each on 21 and 30 July. Satellite images showed no evidence of thermal activity inside the summit crater from September 2015 through early July 2020. Sentinel-2 satellite imagery first indicated a strong thermal anomaly inside the pyroclastic cone within the crater on 19 July 2020; it remained on 24 and 29 July (figure 35). A small SO2 signature was measured by the TROPOMI instrument on the Sentinel-5P satellite on 25 July.

Figure (see Caption) Figure 34. MIROVA thermal anomaly data indicated renewed activity on 16 July 2020 at Raung as seen in this graph of activity from 13 October 2019 through September 2020. Satellite images indicated that the dark lines at the beginning of the graph are from a large area of fires that burned on the flank of Raung in October 2019. Heat flow remained high through July and began to diminish in mid-August 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 35. Thermal anomalies were distinct inside the crater of the pyroclastic cone within the summit crater of Raung on 19, 24, and 29 July 2020. Data is from the Sentinel-2 satellite shown with Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

After an explosion on 1 August 2020 emissions from the crater were not observed again until steam plumes were seen rising 100 m on 7 August. They were reported rising 100-200 m above the summit intermittently until a dense gray ash plume was reported by PVMBG on 11 August rising 200 m. After that, diffuse steam plumes no more than 100 m high were reported for the rest of the month except for white to brown emissions to 100 m on 21 August. Thermal anomalies of a similar brightness to July from the same point within the summit crater were recorded in satellite imagery on 3, 8, 13, 18, and 23 August. Single MODVOLC thermal alerts were reported on 1, 8, 12, and 19 August.

In early September dense steam plumes rose 200 m above the crater a few times but were mostly 50 m high or less. White and gray emissions rose 50-300 m above the summit on 15, 20, 27, and 30 September. Thermal anomalies were still present in the same spot in Sentinel-2 satellite imagery on 2, 7, 12, 17, and 27 September, although the signal was weaker than during July and August (figure 36). PVMBG reported gray emissions rising 100-300 m above the summit on 1 October 2020 and two seismic explosion events. Gray emissions rose 50-200 m the next day and nine explosions were recorded. On 3 October, emissions were still gray but only rose 50 m above the crater and no explosions were reported. No emissions were observed from the summit crater for the remainder of the month. Sentinel-2 satellite imagery showed a hot spot within the summit crater on 2 and 7 October, but clear views of the crater on 12, 17, and 22 October showed no heat source within the crater (figure 37).

Figure (see Caption) Figure 36. The thermal anomaly at Raung recorded in Sentinel-2 satellite data decreased in intensity between August and October 2020. It was relatively strong on 13 August (left) but had decreased significantly by 12 September (middle) and remained at a lower level into early October (right). Data shown with Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground
Figure (see Caption) Figure 37. A small but distinct thermal anomaly was still present within the pyroclastic cone inside the summit crater of Raung on 7 October 2020 (left) but was gone by 12 October (middle) and did not reappear in subsequent clear views of the crater through the end of October. Satellite imagery of 7 and 12 October processed with Atmospheric penetration rendering (bands 12, 11, 8A). Natural color rendering (bands 4, 3, 2) from 17 October (right) shows no clear physical changes to the summit crater during the latest eruption. Courtesy of Sentinel Hub Playground.

Geologic Background. Raung, one of Java's most active volcanoes, is a massive stratovolcano in easternmost Java that was constructed SW of the rim of Ijen caldera. The unvegetated summit is truncated by a dramatic steep-walled, 2-km-wide caldera that has been the site of frequent historical eruptions. A prehistoric collapse of Gunung Gadung on the W flank produced a large debris avalanche that traveled 79 km, reaching nearly to the Indian Ocean. Raung contains several centers constructed along a NE-SW line, with Gunung Suket and Gunung Gadung stratovolcanoes being located to the NE and W, respectively.

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/); 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/); 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/); 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/); Google Earth (URL: https://www.google.com/earth/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); MJ (URL: https://twitter.com/MieJamaludin/status/1167613617191043072).


Nyamuragira (DR Congo) — December 2020 Citation iconCite this Report

Nyamuragira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


Numerous thermal anomalies and gas emissions from the lava lake through November 2020

Nyamuragira (also known as Nyamulagira) is a shield volcano in the Democratic Republic of the Congo with a 2 x 2.3 km caldera at the summit. A summit crater lies in the NE part of the caldera. In the recent past, the volcano has been characterized by intra-caldera lava flows, lava emissions from its lava lake, thermal anomalies, gas-and-steam emissions, and moderate seismicity (BGVN 44:12, 45:06). This report reviews activity during June-November 2020, based on satellite data.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed numerous thermal anomalies associated with the volcano during June-November 2020, although some decrease was noted during the last half of August and between mid-October to mid-November (figure 91). Between six and seven thermal hotspots per month were identified by MODVOLC during June-November 2020, with as many as 4 pixels on 11 August. In the MODVOLC system, two main hotspot groupings are visible, the largest being at the summit crater, on the E side of the caldera.

Figure (see Caption) Figure 91. MIROVA graph of thermal activity (log radiative power) at Nyamuragira during March 2020-January 2021. During June-November 2020, most were in the low to moderate range, with a decrease in power during November. Courtesy of MIROVA.

Sentinel-2 satellite images showed several hotspots in the summit crater throughout the reporting period (figure 92). By 26 July and thereafter, hotspots were also visible in the SW portion of the caldera, and perhaps just outside the SW caldera rim. Gas-and-steam emissions from the lava lake were also visible throughout the period.

Figure (see Caption) Figure 92. Sentinel-2 satellite images of Nyamuragira on 26 July (left) and 28 November (right) 2020. Thermal activity is present at several locations within the summit crater (upper right of each image) and in the SW part of the caldera (lower left). SWIR rendering (bands 12, 8A, 4). Courtesy of Sentinel Hub Playground.

Geologic Background. Africa's most active volcano, Nyamuragira, is a massive high-potassium basaltic shield about 25 km N of Lake Kivu. Also known as Nyamulagira, it has generated extensive lava flows that cover 1500 km2 of the western branch of the East African Rift. The broad low-angle shield volcano contrasts dramatically with the adjacent steep-sided Nyiragongo to the SW. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Historical eruptions have occurred within the summit caldera, as well as from the numerous fissures and cinder cones on the flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Historical lava flows extend down the flanks more than 30 km from the summit, reaching as far as Lake Kivu.

Information Contacts: Observatoire Volcanologique de Goma (OVG), Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; 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/exp).


Sinabung (Indonesia) — November 2020 Citation iconCite this Report

Sinabung

Indonesia

3.17°N, 98.392°E; summit elev. 2460 m

All times are local (unless otherwise noted)


Explosions begin again on 8 August 2020; dome growth confirmed in late September

Indonesia’s Sinabung volcano in north Sumatra has been highly active since its first confirmed Holocene eruption during August and September 2010. It remained quiet after the initial eruption until September 2013, when a new eruptive phase began that continued through June 2018. A summit dome emerged in late 2013 and produced a large lava “tongue” during 2014. Multiple explosions produced ash plumes, block avalanches, and deadly pyroclastic flows during the eruptive period. A major explosion in February 2018 destroyed most of the summit dome. After a pause in eruptive activity from September 2018 through April 2019, explosions resumed during May and June 2019. The volcano was quiet again until an explosion on 8 August 2020 began another eruption that included a new dome. This report covers activity from July 2019 through October 2020 with information provided by Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), referred to by some agencies as CVGHM or the Indonesian Center of Volcanology and Geological Hazard Mitigation, the Darwin Volcanic Ash Advisory Centre (VAAC), and the Badan Nacional Penanggulangan Bencana (National Disaster Management Authority, BNPB). Additional information comes from satellite instruments and local news reports.

Only steam plumes and infrequent lahars were reported at Sinabung during July 2019-July 2020. A new eruption began on 8 August 2020 with a phreatic explosion and dense ash plumes. Repeated explosions were reported throughout August; ashfall was reported in many nearby communities several times. Explosions decreased significantly during September, but SO2 emissions persisted. Block avalanches from a new growing dome were first reported in early October; pyroclastic flows accompanied repeated ash emissions during the last week of the month. Thermal data suggested that the summit dome continued growing slowly during October.

Activity during July 2019-October 2020. After a large explosion on 9 June 2019, activity declined significantly, and no further emissions or incandescence was reported after 25 June (BGVN 44:08). For the remainder of 2019 steam plumes rose 50-400 m above the summit on most days, occasionally rising to 500-700 m above the crater. Lahars were recorded by seismic instruments in July, August, September, and December. During January-July 2020 steam plumes were reported usually 50-300 m above the summit, sometimes rising to 500 m. On 21 March 2020 steam plumes rose to 700 m, and a lahar was recorded by seismic instruments. Lahars were reported on 26 and 28 April, 3 and 5 June, and 11 July.

A swarm of deep volcanic earthquakes was reported by PVMBG on 7 August 2020. This was followed by a phreatic explosion with a dense gray to black ash plume on 8 August that rose 2,000 m above the summit and drifted E; a second explosion that day produced a plume that rose 1,000 m above the summit. According to the Jakarta Post, ash reached the community of Berastagi (15 km E) along with the districts of Naman Teran (5-10 km NE), Merdeka (15 km NE), and Dolat Rayat (20 km E). Continuous tremor events were first recorded on 8 August and continued daily until 26 August. Two explosions were recorded on 10 August; the largest produced a dense gray ash plume that rose 5,000 m above the summit and drifted NE and SE (figure 77). The Darwin VAAC reported the eruption clearly visible in satellite imagery at 9.7 km altitude and drifting W. Later they reported a second plume drifting ESE at 4.3 km altitude. After this large explosion the local National Disaster Management Authority (BNPB) reported significant ashfall in three districts: Naman Teran, Berastagi and Merdeka. Emissions on 11 and 12 August were white and gray and rose 100-200 m. Multiple explosions on 13 August produced white and gray ash plumes that rose 1,000-2,000 m above the summit. Explosions on 14 August produced gray and brown ash plumes that rose 1,000-4,200 m above the summit and drifted S and SW (figure 77). The Darwin VAAC reported that the ash plume was partly visible in satellite imagery at 7.6 km altitude moving W; additional plumes were moving SE at 3.7 km altitude and NE at 5.5 km altitude.

Figure (see Caption) Figure 77. Numerous explosions were recorded at Sinabung during August 2020. An ash plume rose to 5,000 m above the summit on 10 August (left) and drifted both NE and SE. On 14 August gray and brown ash plumes rose 1,000-4,200 m above the summit and drifted S, SW, SE and NE (right) while ashfall covered crops SE of the volcano. Courtesy of PVMBG (Sinabung Eruption Notices, 10 and 14 August 2020).

White, gray, and brown emissions rose 800-1,000 m above the summit on 15 and 17 August. The next day white and gray emissions rose 2,000 m above the summit. The Darwin VAAC reported an ash plume visible at 5.2 km altitude drifting SW. A large explosion on 19 August produced a dense gray ash plume that rose 4,000 above the summit and drifted S and SW. Gray and white emissions rose 500 m on 20 August. Two explosions were recorded seismically on 21 August, but rainy and cloudy weather prevented observations. White steam plumes rose 300 m on 22 August, and a lahar was recorded seismically. On 23 August, an explosion produced a gray ash plume that rose 1,500 m above the summit and pyroclastic flows that traveled 1,000 m down the E and SE flanks (figure 78). Continuous tremors were accompanied by ash emissions. White, gray, and brown emissions rose 600 m on 24 August. An explosion on 25 August produced an ash plume that rose 800 m above the peak and drifted W and NW (figure 79). During 26-30 August steam emissions rose 100-400 m above the summit and no explosions were recorded. Dense gray ash emissions rose 1,000 m and drifted E and NE after an explosion on 31 August. Significant SO2 emissions were associated with many of the explosions during August (figure 80).

Figure (see Caption) Figure 78. On 23 August 2020 an explosion at Sinabung produced a gray ash plume that rose 1,500 m above the summit and produced pyroclastic flows that traveled 1,000 m down the E and SE flanks. Courtesy of PVMBG (Sinabung Eruption Notice, 23 August 2020).
Figure (see Caption) Figure 79. An explosion on 25 August 2020 at Sinabung produced an ash plume that rose 800 m above the peak and drifted W and NW. Courtesy of PVMBG (Sinabung Eruption Notice, 25 August 2020).
Figure (see Caption) Figure 80. Significant sulfur dioxide emissions were measured at Sinabung during August 2020 when near-daily explosions produced abundant ash emissions. A small plume was also recorded from Kerinci on 19 August 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Explosive activity decreased substantially during September 2020. A single explosion reported on 5 September produced a white and brown ash plume that rose 800 m above the summit and drifted NNE. During the rest of the month steam emissions rose 50-500 m above the summit before dissipating. Two lahars were reported on 7 September, and one each on 11 and 30 September. Although only a single explosion was reported, anomalous SO2 emissions were present in satellite data on several days.

The character of the activity changed during October 2020. Steam plumes rising 50-300 m above the summit were reported during the first week and a lahar was recorded by seismometers on 4 October. The first block avalanches from a new dome growing at the summit were reported on 8 October with material traveling 300 m ESE from the summit (figure 81). During 11-13 October block avalanches traveled 300-700 m E and SE from the summit. They traveled 100-150 m on 14 October. Steam plumes rising 50-500 m above the summit were reported during 15-22 October with two lahars recorded on 21 October. White and gray emissions rose 50-1,000 m on 23 October. The first of a series of pyroclastic flows was reported on 25 October; they were reported daily through the end of the month when the weather permitted, traveling 1,000-2,500 m from the summit (figure 82). In addition, block avalanches from the growing dome were observed moving down the E and SE flanks 500-1,500 m on 25 October and 200-1,000 m each day during 28-31 October (figure 83). Sentinel-2 satellite data indicated a very weak thermal anomaly at the summit in late September; it was slightly larger in late October, corroborating with images of the slow-growing dome (figure 84).

Figure (see Caption) Figure 81. A new lava dome appeared at the summit of Sinabung in late September 2020. Block avalanches from the dome were first reported on 8 October. Satellite imagery indicating a thermal anomaly at the summit was very faint at the end of September and slightly stronger by the end of October. The dome grew slowly between 30 September (top) and 22 October 2020 (bottom). Photos taken by Firdaus Surbakti, courtesy of Rizal.
Figure (see Caption) Figure 82. Pyroclastic flows at Sinabung were accompanied ash emissions multiple times during the last week of October, including the event seen here on 27 October 2020. Courtesy of PVMBG and CultureVolcan.
Figure (see Caption) Figure 83. Block avalanches from the growing summit dome at Sinabung descended the SE flank on 28 October 2020. The dome is visible at the summit. Courtesy of PVMBG and MAGMA.
Figure (see Caption) Figure 84. A very faint thermal anomaly appeared at the summit of Sinabung in Sentinel 2 satellite imagery on 28 September 2020 (left). One month later on 28 October the anomaly was bigger, corroborating photographic evidence of the growing dome. Atmospheric penetration rendering (bands 12, 11, 8A) courtesy of Sentinel Hub Playground.

Geologic Background. Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical andesitic-to-dacitic edifice is at the southern end of the four overlapping summit craters. The youngest deposit is a SE-flank pyroclastic flow 14C dated by Hendrasto et al. (2012) at 740-880 CE. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.

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/); 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/); 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/); 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/); The Jakarta Post, 3rd Floor, Gedung, Jl. Palmerah Barat 142-143 Jakarta 10270 (URL: https://www.thejakartapost.com/amp/news/2020/08/08/mount-sinabung-erupts-again-after-year-of-inactivity.html);Rizal (URL: https://twitter.com/Rizal06691023/status/1319452375887740930); CultureVolcan (URL: https://twitter.com/CultureVolcan/status/1321156861173923840).


Heard (Australia) — November 2020 Citation iconCite this Report

Heard

Australia

53.106°S, 73.513°E; summit elev. 2745 m

All times are local (unless otherwise noted)


Persistent thermal anomalies in the summit crater from June through October 2020

The remote Heard Island is located in the southern Indian Ocean and contains the Big Ben stratovolcano, which has had intermittent activity since 1910. The island’s activity, characterized by thermal anomalies and occasional lava flows (BGVN 45:05), is primarily monitored by satellite instruments. This report updates activity from May through October 2020 using information from satellite-based instruments.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed frequent thermal activity in early June that continued through July (figure 43). Intermittent, slightly higher-power thermal anomalies were detected in late August through mid-October, the strongest of which occurred in October. Two of these anomalies were also detected in the MODVOLC algorithm on 12 October.

Figure (see Caption) Figure 43. A small pulse in thermal activity at Heard was detected in early June and continued through July 2020, according to the MIROVA system (Log Radiative Power). Thermal anomalies appeared again starting in late August and continued intermittently through mid-October 2020. Courtesy of MIROVA.

Sentinel-2 thermal satellite imagery showed a single thermal anomaly on 3 May. In comparison to the MIROVA graph, satellite imagery showed a small pulse of strong thermal activity at the summit of Big Ben in June (figure 44). Some of these thermal anomalies were accompanied by gas-and-steam emissions. Persistent strong thermal activity continued through July. Starting on 2 July through at least 17 July two hotspots were visible in satellite imagery: one in the summit crater and one slightly to the NW of the summit (figure 45). Some gas-and-steam emissions were seen rising from the S hotspot in the summit crater. In August the thermal anomalies had decreased in strength and frequency but persisted at the summit through October (figure 45).

Figure (see Caption) Figure 44. Thermal satellite images of Heard Island’s Big Ben volcano showed strong thermal signatures (bright yellow-orange) sometimes accompanied by gas-and-steam emissions drifting SE (top left) and NE (bottom right) during June 2020. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 45. Thermal satellite images of Heard Island’s Big Ben volcano showed persistent thermal anomalies (bright yellow-orange) near the summit during July through October 2020. During 14 (top left) and 17 (top right) July a second hotspot was visible NW of the summit. By 22 October (bottom right) the thermal anomaly had significantly decreased in strength in comparison to previous months. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. Heard Island on the Kerguelen Plateau in the southern Indian Ocean consists primarily of the emergent portion of two volcanic structures. The large glacier-covered composite basaltic-to-trachytic cone of Big Ben comprises most of the island, and the smaller Mt. Dixon lies at the NW tip of the island across a narrow isthmus. Little is known about the structure of Big Ben because of its extensive ice cover. The historically active Mawson Peak forms the island's high point and lies within a 5-6 km wide caldera breached to the SW side of Big Ben. Small satellitic scoria cones are mostly located on the northern coast. Several subglacial eruptions have been reported at this isolated volcano, but observations are infrequent and additional activity may have occurred.

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).


Sabancaya (Peru) — October 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 produced ash plumes, SO2 plumes, and thermal anomalies during June-September 2020

Sabancaya, located in Peru, is a stratovolcano that has been very active since 1986. The current eruptive period began in November 2016 and has recently been characterized by lava dome growth, daily explosions, ash plumes, ashfall, SO2 plumes, and ongoing thermal anomalies (BGVN 45:06). Similar activity continues into this reporting period of June through September 2020 using information from weekly reports from the Observatorio Vulcanologico INGEMMET (OVI), the Instituto Geofisico del Peru (IGP), and various satellite data. The Buenos Aires Volcanic Ash Advisory Center (VAAC) issued a total of 520 reports of ongoing ash emissions during this time.

Volcanism during this reporting period consisted of daily explosions, nearly constant gas-and-ash plumes, SO2 plumes, and persistent thermal anomalies in the summit crater. Gas-and-ash plumes rose to 1.5-4 km above the summit crater, drifting up to 35 km from the crater in multiple directions; several communities reported ashfall every month except for August (table 7). Sulfur dioxide emissions were notably high and recorded almost daily with the TROPOMI satellite instrument (figure 83). The satellite measurements of the SO2 emissions exceeded 2 DU (Dobson Units) at least 20 days each month of the reporting period. These SO2 plumes sometimes persisted over multiple days and ranged between 1,900-10,700 tons/day. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows frequent thermal activity through September within 5 km of the summit crater, though the power varied; by late August, the thermal anomalies were stronger compared to the previous months (figure 84). This increase in power is also reflected by the MODVOLC algorithm that detected 11 thermal anomalies over the days of 31 August and 4, 6, 13, 17, 18, 20, and 22 September 2020. Many of these thermal hotspots were visible in Sentinel-2 thermal satellite imagery, occasionally accompanied by gas-and-steam and ash plumes (figure 85).

Table 7. Persistent activity at Sabancaya during June through September included multiple daily explosions that produced ash plumes rising several kilometers above the summit and drifting in multiple directions; this resulted in ashfall in communities within 35 km of the volcano. Satellite instruments recorded daily SO2 emissions. Data courtesy of OVI-INGEMMET, IGP, and the NASA Global Sulfur Dioxide Monitoring Page.

Month Avg. daily explosions by week Max plume heights (km above the crater) Plume drift (km) and direction Communities reporting ashfall Minimum days with SO2 over 2 DU SO2 emissions per day (tons) by week
Jun 2020 20, 10, 9, 13 1.5-4 30 km, SE, S, SW, NE, W, E Chivay, Achoma, Ichupampa, Yanque, and Coporaque, Sallali, Madrigal, Lari, and Ichupampa 28 8,400, 2,200, 3,100, 7,600
Jul 2020 20, 15, 11, 12, 19 2-2.6 15-30 km E, NE, NW, SE, SW, S, W Achoma and Chivay 23 4,400, 6,000, 1,900, 2,100, 5,900
Aug 2020 18, 12, 9, 29 1.7-3.6 20-30 km W, SW, SE, S, E, NW - 20 2,300, 3,800, 5,300, 10,700
Sep 2020 39, 35, 33, 38, 40 1.8-3.5 25-35 km SE, S, SW, W, E, NE, N, NW, W Lari, Achoma, Maca, Chivay, Taya, Huambo, Huanca, and Lluta 28 9,700, 2,600, 8,800, 7,800, 4,100
Figure (see Caption) Figure 83. Sulfur dioxide plumes were captured almost daily from Sabancaya during June through September 2020 by the TROPOMI instrument on the Sentinel-5P satellite. Some of the largest SO2 plumes occurred on 19 June (top left), 5 July (top right), 30 August (bottom left), and 10 September (bottom right) 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 84. Thermal activity at Sabancaya varied in power from 13 October 2019 through September 2020, but was consistent in frequency, according to the MIROVA graph (Log Radiative Power). A pulse in thermal activity is shown in late August 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 85. Sentinel-2 thermal satellite imagery showed frequent gas-and-steam and ash plumes rising from Sabancaya, accompanied by ongoing thermal activity from the summit crater during June through September 2020. On 23 June (top left) a dense gray-white ash plume was visible drifting E from the summit. On 3 July (top right) and 27 August (bottom left) a strong thermal hotspot (bright yellow-orange) was accompanied by some degassing. On 1 September (bottom right) the thermal anomaly persisted with a dense gray-white ash plume drifting SE from the summit. Images using “Natural Color” rendering (bands 4, 3, 2) on 23 June 2020 (top left) and the rest have “Atmospheric penetration” rendering (bands 12, 11, 8a). Courtesy of Sentinel Hub Playground.

OVI detected slight inflation on the N part of the volcano, which continued to be observed throughout the reporting period. Persistent thermal anomalies caused by the summit crater lava dome were observed in satellite data. The average number of daily explosions during June ranged from 18 during 1-7 June to 9 during 15-21 June, which generated gas-and-ash plumes that rose 1.5-4 km above the crater and drifted 30 km SE, S, SW, NE, W, and E (figure 86). The strongest sulfur dioxide emissions were recorded during 1-7 June measuring 8,400 tons/day. On 20 June drone video showed that the lava dome had been destroyed, leaving blocks on the crater floor, though the crater remained hot, as seen in thermal satellite imagery (figure 85). During 22-28 June there were an average of 13 daily explosions, which produced ash plumes rising to a maximum height of 4 km, drifting NE, E, and SE. As a result, ashfall was reported in the districts of Chivay, Achoma, Ichupampa, Yanque, and Coporaque, and in the area of Sallali. Then, on 27 June ashfall was reported in several areas NE of the volcano, which included the districts of Madrigal, Lari, Achoma, Ichupampa, Yanque, Chivay, and Coporaque.

Figure (see Caption) Figure 86. Multiple daily explosions at Sabancaya produced ash plumes that rose 1.5-4 km above the crater during June 2020. Images are showing 8 (left) and 27 (right) June 2020. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-24-2020/INGEMMET Semana del 08 al 14 de junio del 2020 and RSSAB-26-2020/INGEMMET Semana del 22 al 28 de junio del 2020).

Slight inflation continued to be monitored in July, occurring about 4-6 km N of the crater, as well as on the SE flank. Daily explosions continued, producing gas-and-ash plumes that rose 2-2.6 km above the crater and drifting 15-30 km E, NE, NW, SE, SW, S, and W (figure 87). The number of daily explosions increased slightly compared to the previous month, ranging from 20 during 1-5 July to 11 during 13-19 July. SO2 emissions that were measured each week ranged from 1,900 to 6,000 tons/day, the latter of which occurred during 6-12 July. Thermal anomalies continued to be observed in thermal satellite data over the summit crater throughout the month. During 6-12 July gas-and-ash plumes rose 2.3-2.5 km above the crater, drifting 30 km SE, E, and NE, resulting in ashfall in Achoma and Chivay.

Figure (see Caption) Figure 87. Multiple daily explosions at Sabancaya produced ash plumes that rose 2-3.5 km above the crater during July 2020. Images are showing 7 (left) and 26 (right) July 2020. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-28-2020/INGEMMET Semanal: del 06 al 12 de julio del 2020 and RSSAB-30-2020/INGEMMET Semanal: del 20 al 26 de julio del 2020).

OVI reported continued slight inflation on the N and SE flanks during August. Daily explosive activity had slightly declined in the first part of the month, ranging from 18 during the 3-9 August to 9 during 17-23 August. Dense gray gas-and-ash plumes rose 1.7-3.6 km above the crater, drifting 20-30 km in various directions (figure 88), though no ashfall was reported. Thermal anomalies were observed using satellite data throughout the month. During 24-30 August a pulse in activity increased the daily average of explosions to 29, as well as the amount of SO2 emissions (10,700 tons/day); nighttime incandescence accompanied this activity. During 28-29 August higher levels of seismicity and inflation were reported compared to the previous weeks. The daily average of explosions increased again during 31 August-6 September to 39; nighttime incandescence remained.

Figure (see Caption) Figure 88. Multiple daily explosions at Sabancaya produced ash plumes that rose 1.7-3.6 km above the crater during August 2020. Images are showing 1 (left) and 29 (right) August 2020. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-31-2020/INGEMMET Semanal del 27 de julio al 02 de agosto del 2020 and RSSAB-35-2020/INGEMMET Semanal del 24 al 30 de agosto del 2020).

Increased volcanism was reported during September with the daily average of explosions ranging from 33 during 14-20 September to 40 during 28 September-4 October. The resulting gas-and-ash plumes rose 1.8-3.5 km above the crater drifting 25-35 km in various directions (figure 89). SO2 flux was measured by OVI ranging from 2,600 to 9,700 tons/day, the latter of which was recorded during 31 August to 6 September. During 7-13 September an average of 35 explosions were reported, accompanied by gas-and-ash plumes that rose 2.6-3.5 km above the crater and drifting 30 km SE, SW, W, E, and S. These events resulted in ashfall in Lari, Achoma, and Maca. The following week (14-20 September) ashfall was reported in Achoma and Chivay. During 21-27 September the daily average of explosions was 38, producing ash plumes that resulted in ashfall in Taya, Huambo, Huanca, and Lluta. Slight inflation on the N and SE flanks continued to be monitored by OVI. Strong activity, including SO2 emissions and thermal anomalies over the summit crater persisted into at least early October.

Figure (see Caption) Figure 89. Multiple daily explosions at Sabancaya produced ash plumes that rose 1.8-2.6 km above the crater during September 2020. Images are showing 4 (left) and 27 (right) September 2020. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-36-2020/INGEMMET Semanal del 31 de agosto al 06 de septiembre del 2020 and RSSAB-39-2020/INGEMMET Semanal del 21 al 27 de septiembre 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); Instituto Geofisico del Peru (IGP), Calle Badajoz N° 169 Urb. Mayorazgo IV Etapa, Ate, Lima 15012, Perú (URL: https://www.gob.pe/igp); 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); 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).


Rincon de la Vieja (Costa Rica) — October 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)


Frequent small phreatic explosions with intermittent ash plumes during April-September 2020

Rincón de la Vieja is a remote volcanic complex in Costa Rica that contains an acid lake. Frequent weak phreatic explosions have occurred since 2011 (BGVN 44:08). The most recent eruption period began in January 2020, which consisted of small phreatic explosions, gas-and-steam plumes, pyroclastic flows, and lahars (BGVN 45:04). This reporting period covers April through September 2020, with activity characterized by continued small phreatic explosions, three lahars, frequent gas-and-steam plumes, and ash plumes. The primary source of information for this report is the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA) using weekly bulletins and the Washington Volcanic Ash Advisory Center (VAAC).

Small, frequent, phreatic explosions were common at Rincón de la Vieja during this reporting period. One to several eruptions were reported on at least 16 days in April, 15 days in May, 8 days in June, 10 days in July, 18 days in August, and 13 days in September (table 5). Intermittent ash plumes accompanied these eruptions, rising 100-3,000 m above the crater and drifting W, NW, and SW during May and N during June. Occasional gas-and-steam plumes were also observed rising 50-2,000 m above the crater rim.

Table 5. Monthly summary of activity at Rincón de la Vieja during April through September 2020. Courtesy of OVSICORI-UNA.

Month Minimum total days of eruptions Ash plume height (m above the crater) Notable plume drift Gas-and-steam plume height (m above the crater)
Apr 2020 16 200-1,000 - 50-1,500
May 2020 15 200-3,000 W, NW, SW 200-2,000
Jun 2020 8 100-2,000 N -
Jul 2020 10 1,000 - -
Aug 2020 18 500-1,000 - 500
Sep 2020 13 700 - 50

During April small explosions were detected almost daily, some of which generated ash plumes that rose 200-1,000 m above the crater and gas-and-steam emissions that rose 50-1,500 m above the crater. On 4 April an eruption at 0824 produced an ash plume that rose 1 km above the crater rim. A small hydrothermal explosion at 0033 on 11 April, recorded by the webcam in Sensoria (4 km N), ejected water and sediment onto the upper flanks. On 15 April a phreatic eruption at 0306 resulted in lahars in the Pénjamo, Azufrada, and Azul rivers, according to local residents. Several small explosions were detected during the morning of 19 April; the largest phreatic eruption ejected water and sediment 300 m above the crater rim and onto the flanks at 1014, generated a lahar, and sent a gas-and-steam plume 1.5 km above the crater (figure 30). On 24 April five events were recorded by the seismic network during the morning, most of which produced gas-and-steam plumes that rose 300-500 m above the crater. The largest event on this day occurred at 1020, ejecting water and solid material 300 m above the crater accompanied by a gas-and-steam plume rising up to 1 km.

Figure (see Caption) Figure 30. Webcam image of small hydrothermal eruptions at Rincón de la Vieja on 19 April 2020. Image taken by the webcam in Dos Ríos de Upala; courtesy of OVSICORI-UNA.

Similar frequent phreatic activity continued in May, with ash plumes rising 200-1,500 m above the crater, drifting W, NW, and SW, and gas-and-steam plumes rising up to 2 km. On 5 May an eruption at 1317 produced a gas-and-steam plume 200 m above the crater and a Washington VAAC advisory reported that an ash plume rose to 2.1 km altitude, drifting W. An event at 1925 on 9 May generated a gas-and-steam plume that rose almost 2 km. An explosion at 1128 on 15 May resulted in a gas-and-steam plume that rose 1 km above the crater rim, accompanied by a gray, sediment-laden plume that rose 400 m. On 21 May a small ash eruption at 0537 sent a plume 1 km above the crater (figure 31). According to a Washington VAAC advisory, an ash plume rose 3 km altitude, drifting NW on 22 May. During the early evening on 25 May an hour-long sequence of more than 70 eruptions and emissions, according to OVSICORI-UNA, produced low gas-and-steam plumes and tephra; at 1738, some ejecta was observed above the crater rim. The next day, on 26 May, up to 52 eruptive events were observed. An eruption at 2005 was not visible due to weather conditions; however, it resulted in a minor amount of ashfall up to 17 km W and NW, which included Los Angeles of Quebrada Grande and Liberia. A phreatic explosion at 1521 produced a gray plume that rose 1.5 km above the crater (figure 31). An eruption at 1524 on 28 May sent an ash plume 3 km above the crater that drifted W, followed by at least three smaller eruptions at 1823, 1841, and 1843. OVSICORI-UNA reported that volcanism began to decrease in frequency on 28-29 May. Sulfur dioxide emissions ranged between 100 and 400 tons per day during 28 May to 15 June.

Figure (see Caption) Figure 31. Webcam images of gray gas-and-steam and ash emissions at Rincón de la Vieja on 21 (left), and 27 (right) May 2020. Both images taken by the webcam in Dos Ríos de Upala and Sensoria; courtesy of OVSICORI-UNA.

There were eight days with eruptions in June, though some days had multiple small events; phreatic eruptions reported on 1-2, 13, 16-17, 19-20, and 23 June generated plumes 1-2 km above the crater (figure 32). During 2-8 June SO2 emissions were 150-350 tons per day; more than 120 eruptions were recorded during the preceding weekend. Ashfall was observed N of the crater on 4 June. During 9-15 June the SO2 emissions increased slightly to 100-400 tons per day. During 16-17 June several small eruptive events were detected, the largest of which occurred at 1635 on 17 June, producing an ash plume that rose 1 km above the crater.

Figure (see Caption) Figure 32. Webcam images of gray gas-and-steam and ash plumes rising from Rincón de la Vieja on 1 (top left), 2 (top right), 7 (bottom left), and 13 (bottom right) June 2020. The ash plume on 1 June rose between 1.5 and 2 km above the crater. The ash plume on 13 June rose 1 km above the crater. Courtesy of OVSICORI-UNA.

Explosive hydrothermal activity was lower in June-September compared to January-May 2020, according to OVSICORI-UNA. Sporadic small phreatic explosions and earthquakes were registered during 22-25 and 29 July-3 August, though no lahars were reported. On 25 July an eruptive event at 0153 produced an ash plume that rose 1 km above the crater. Similar activity continued into August. On 5 and 6 August phreatic explosions were recorded at 0546 and 0035, respectively, the latter of which generated a plume that rose 500 m above the crater. These events continued to occur on 10, 16, 19-20, 22-25, 27-28, and 30-31 August, generating plumes that rose 500 m to 1 km above the crater.

On 3 September geologists observed that the acid lake in the main crater had a low water level and exhibited strong gas emissions; vigorous fumaroles were observed on the inner W wall of the crater, measuring 120°C. Gas-and-steam emissions continued to be detected during September, occasionally accompanied by phreatic eruptions. On 7 September an eruption at 0750 produced an ash plume that rose 50 m above the crater while the accompanying gas-and-steam plume rose 500 m. Several low-energy phreatic explosions occurred during 8-17, 20, and 22-28 September, characterized primarily by gas-and-steam emissions. An eruption on 16 September ejected material from the crater and generated a small lahar. Sulfur dioxide emissions were 100 tons per day during 16-21 September. On 17 September an eruption at 0632 produced an ash plume that rose 700 m above the crater (figure 33). A relatively large eruptive event at 1053 on 22 September ejected material out of the crater and into N-flank drainages.

Figure (see Caption) Figure 33. Webcam image of an eruption plume rising above Rincón de la Vieja on 17 September 2020. Courtesy of OVSICORI-UNA.

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 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 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 3,500 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/); 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).


Fuego (Guatemala) — December 2020 Citation iconCite this Report

Fuego

Guatemala

14.473°N, 90.88°W; summit elev. 3763 m

All times are local (unless otherwise noted)


Daily explosions, ash emissions, and block avalanches during August-November 2020

Guatemala's Volcán de Fuego has been erupting vigorously since 2002 with reported eruptions dating back to 1531. These eruptions have resulted in major ashfalls, pyroclastic flows, lava flows, and damaging lahars, including a series of explosions and pyroclastic flows in early June 2018 that caused several hundred fatalities. Eruptive activity consisting of explosions with ash emissions, block avalanches, and lava flows began again after a short break and has continued; activity during August-November 2020 is covered in this report. Daily reports are provided by the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH); aviation alerts of ash plumes are issued by the Washington Volcanic Ash Advisory Center (VAAC). Satellite data provide valuable information about heat flow and emissions.

Summary of activity during August-November 2020. Eruptive activity continued at Fuego during August-November 2020, very similar to that during the first part of the year (table 22). Ash emissions were reported daily by INSIVUMEH with explosions often in the 6-12 per hour range. Most of the ash plumes rose to 4.5-4.7 km altitude and generally drifted SW, W, or NW, although rarely the wind direction changed and sent ash to the S and SE. Multiple daily advisories were issued throughout the period by the Washington VAAC warning aviators about ash plumes, which were often visible on the observatory webcam (figure 136). Some of the communities located SW of the volcano received ashfall virtually every day during the period. Block avalanches descended the major drainages daily as well. Sounds were heard and vibrations felt from the explosions most days, usually 7-12 km away. The stronger explosions could be felt and heard 20 km or more from the volcano. During late August and early September a lava flow was active on the SW flank, reaching 700 m in length during the second week of September.

Table 22. Eruptive activity was consistently high at Fuego throughout August – November 2020 with multiple explosions every hour, ash plumes, block avalanches, and near-daily ashfall in the communities in certain directions within 10-20 km of the volcano. Courtesy of INSIVUMEH daily reports.

Month Explosions per hour Ash Plume Heights (km) Ash plume distance (km) and direction Drainages affected by block avalanches Communities reporting ashfall
Aug 2020 2-15 4.3-4.8 SW, W, NW, S, N, 8-20 km Seca, Taniluya, Ceniza, Trinidad, Las Lajas, Honda, Santa Teresa Panimaché I and II, Morelia, Rochela, Finca Palo Verde, Yepocapa, Santa Sofia, El Porvenir, Palo Verde, Sangre de Cristo, Santa Lucía Cotzumalguapa
Sep 2020 3-16 4.3-4.9 W, SW, NW, N, S, 8-20 km Seca, Taniluya, Ceniza, Trinidad, Las Lajas, Honda, Santa Teresa Panimaché I and II, Morelia, Santa Sofía, Finca Palo Verde, Sangre de Cristo, Yepocapa, Porvenir, Yucales, Ojo de Agua, Finca La Conchita
Oct 2020 3-19 4.1-4.8 SW, W, S, SE, N, E, 10-20 km Seca, Taniluya, Ceniza, Trinidad, Las Lajas, Honda, Santa Teresa Panimache I and II, Morelia, Sangre de Cristo, Yepocapa, La Rochela, El Porvenir, Ceilán, Santa Sofía, Yucales, Finca Palo Verde
Nov 2020 4-14 4.0-4.8 S, SW, SE, W, NW, 10-35 km Seca, Taniluya, Ceniza, Trinidad, Las Lajas, Honda, Santa Teresa El Jute Panimaché I and II, Sangre de Cristo, Morelia, Ceilan, La Rochela, El Zapote, Santa Sofía, Yucales, San Juan Alotenango, Ciudad Vieja, San Miguel Dueñas y Antigua Guatemala, Palo Verde, El Porvenir, San Pedro Yepocapa, Quisaché, Santa Emilia
Figure (see Caption) Figure 136. Consistent daily ash emissions produced similar looking ash plumes at Fuego during August-November 2020. Plumes usually rose to 4.5-4.8 km altitude and drifted SW. Courtesy of INSIVUMEH.

The frequent explosions, block avalanches, and lava flows produced a strong thermal signal throughout the period that was recorded in both the MIROVA project Log Radiative Power graph (figure 137) and in numerous Sentinel-2 satellite images (figure 138). MODVOLC data produced thermal alerts 4-6 days each month. At least one lahar was recorded each month; they were most frequent in September and October.

Figure (see Caption) Figure 137. The MIROVA graph of activity at Fuego for the period from 15 January through November 2020 suggested persistent moderate to high-level heat flow for much of the time. Courtesy of MIROVA.
Figure (see Caption) Figure 138. Atmospheric penetration rendering of Sentinel-2 satellite images (bands 12, 11, 8A) of Fuego during August-November 2020 showed continued thermal activity from block avalanches, explosions, and lava flows at the summit and down several different ravines. Courtesy of Sentinel Hub Playground.

Activity during August-November 2020. The number of explosions per hour at Fuego during August 2020 was most often 7-10, with a few days that were higher at 10-15. The ash plumes usually rose to 4.5-4.8 km altitude and drifted SW or W up to 15 km. Incandescence was visible 100-300 m above the summit crater on most nights. All of the major drainages including the Seca, Santa Teresa, Ceniza, Trinidad, Taniluyá, Las Lajas, and Honda were affected by block avalanches virtually every day. In addition, the communities of Panimaché I and II, Morelia, Santa Sofía, Finca Palo Verde, El Porvenir, San Pedro Yepocapa, and Sangre de Cristo reported ashfall almost every day. Sounds and vibrations were reported multiple days every week, often up to 12 km from the volcano, but occasionally as far as 20 km away. Lahars carrying blocks of rocks and debris 1-2 m in diameter descended the SE flank in the Las Lajas and Honda ravines on 6 August. On 27 August a lava flow 150 m long appeared in the Ceniza ravine. It increased in length over the subsequent few days, reaching 550 m long on 30 August, with frequent block avalanches falling off the front of the flow.

The lava flow in the Ceniza ravine was reported at 100 m long on 5 September. It grew to 200 m on 7 September and reached 700 m long on 12 September. It remained 200-350 m long through 19 September, although instruments monitored by INSIVUMEH indicated that effusive activity was decreasing after 16 September (figure 139). A second flow was 200 m long in the Seca ravine on 19 September. By 22 September, active flows were no longer observed. The explosion rate varied from a low of 3-5 on 1 September to a high of 12-16 on 4, 13, 18, and 22-23 September. Ash plumes rose to 4.5-4.9 km altitude nearly every day and drifted W, NW, and SW occasionally as far as 20 km before dissipating. In addition to the active flow in the Ceniza ravine, block avalanches persisted in the other ravines throughout the month. Ashfall continued in the same communities as in August, but was also reported in Yucales on 4 September along with Ojo de Agua and Finca La Conchita on 17 September. The Las Lajas, Honda, and El Jute ravines were the sites of lahars carrying blocks up to 1.5 m in diameter on 8 and 18 September. On 19 and 24 September lahars again descended Las Lajas and El Jute ravines; the Ceniza ravine had a lahar on 19 September.

Figure (see Caption) Figure 139. Avalanche blocks descended the Ceniza ravine (left) and the Las Lajas ravine (right) at Fuego on 17 September 2020. The webcam that captured this image is located at Finca La Reunión on the SE flank. Courtesy of INSIVUMEH (BOLETÍN VULCANOLÓGICO ESPECIAL BEVFGO # 76-2020, 18 de septiembre de 2020, 14:30 horas).

The same activity continued during October 2020 with regard to explosion rates, plume altitudes, distances, and directions of drift. All of the major ravines were affected by block avalanches and the same communities located W and SW of the summit reported ashfall. In addition, ashfall was reported in La Rochela on 2, 3, 7-9 and 30 October, in Ceilán on 3 and 7-9 October, and in Yucales on 5, 14, 18 and 19 October. Multiple strong explosions with abundant ash were reported in a special bulletin on 14 October; high levels of explosive activity were recorded during 16-23 October. Vibrations and sounds were often felt up to 15 km away and heard as far as 25 km from the volcano during that period. Particularly strong block avalanches were present in the Seca and Ceniza ravines on 20, 25, and 30 October. Abundant rain on 9 October resulted in lahars descending all of the major ravines. The lahar in the Las Lajas ravine overflowed and forced the closure of route RN-14 road affecting the community of San Miguel on the SE flank (figure 140). Heavy rains on 15 October produced lahars in the Ceniza, Las Lajas, and Hondas ravines with blocks up to 2 m in diameter. Multiple lahars on 27 October affected Las Lajas, El Jute, and Honda ravines.

Figure (see Caption) Figure 140. Heavy rains on 9 October 2020 at Fuego caused lahars in all the major ravines. Debris from Las Lajas ravine overflowed highway RN-14 near the community of San Miguel on the SE flank, the area devastated by the pyroclastic flow of June 2018. Courtesy of INSIVUMEH (BEFGO #96 VOLCAN DE FUEGO- ZONA CERO RN-14, SAN MIGUEL LOS LOTES y BARRANCA LAS LAJAS, 09 de octubre de 2020).

On 8 November 2020 a lahar descended the Seca ravine, carrying rocks and debris up to 1 meter in diameter. During the second week of November 2020, the wind direction changed towards the SE and E and brought ashfall to San Juan Alotenango, Ciudad Vieja, San Miguel Dueñas, and Antigua Guatemala on 8 November. Especially strong block avalanches were noted in the Seca and Ceniza ravines on 14, 19, 24, and 29 November. During a period of stronger activity in the fourth week of November, vibrations were felt and explosions heard more than 20 km away on 22 November and more than 25 km away on 27 November. In addition to the other communities affected by ashfall during August-November, Quisaché and Santa Emilia reported ashfall on 30 November.

Geologic Background. Volcán Fuego, one of Central America's most active volcanoes, is also one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between Fuego and Acatenango to the north. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at the mostly andesitic Acatenango. Eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

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/ ); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground);Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); 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).


Kikai (Japan) — November 2020 Citation iconCite this Report

Kikai

Japan

30.793°N, 130.305°E; summit elev. 704 m

All times are local (unless otherwise noted)


Explosion on 6 October 2020 and thermal anomalies in the crater

Kikai is a mostly submarine caldera, 19-km-wide, just S of the Ryukyu Islands of Japan. At the NW rim of the caldera lies the island of Satsuma Iwo Jima (also known as Satsuma-Iojima and Tokara Iojima), and the island’s highest peak, Iodake, a steep stratovolcano. Recent weak ash explosions at Iodake occurred on 2 November 2019 and 29 April 2020 (BGVN 45:02, 45:05). The volcano is monitored by the Japan Meteorological Agency (JMA) and satellite sensors. This report covers the period May-October 2020. During this time, the Alert Level remained at 2 (on a 5-level scale).

Activity at Kikai has been relatively low since the previous eruption on 29 April 2020. During May through October occasional white gas-and-steam emissions rose 0.8-1.3 km above the Iodake crater, the latter of which was recorded in September. Emissions were intermittently accompanied by weak nighttime incandescence, according to JMA (figure 17).

Figure (see Caption) Figure 17. White gas-and-steam emissions rose 1 km above the crater at Satsuma Iwo Jima (Kikai) on 25 May (top) 2020. At night, occasional incandescence could be seen in the Iodake crater, as seen on 29 May (bottom) 2020. Both images taken by the Iwanoue webcam. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, May 2nd year of Reiwa [2020]).

A small eruption at 0757 on 6 October occurred in the NW part of the Iodake crater, which produced a grayish white plume rising 200 m above the crater (figure 18). Faint thermal anomalies were detected in Sentinel-2 thermal satellite imagery in the days just before this eruption (28 September and 3 October) and then after (13 and 23 October), accompanied by gas-and-steam emissions (figures 19 and 20). Nighttime crater incandescence continued to be observed. JMA reported that sulfur dioxide emissions measured 700 tons per day during October, compared to the previous eruption (400-2,000 tons per day in April 2020).

Figure (see Caption) Figure 18. Webcam images of the eruption at Satsuma Iwo Jima (Kikai) on 6 October 2020 that produced an ash plume rising 200 m above the crater (top). Nighttime summit crater incandescence was also observed (bottom). Images were taken by the Iwanoue webcam. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, October 2nd year of Reiwa [2020]).
Figure (see Caption) Figure 19. Weak thermal hotspots (bright yellow-orange) were observed at Satsuma Iwo Jima (Kikai) during late September through October 2020. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 20. Webcam image of a white gas-and-steam plume rising 1.1 km above the crater at Satsuma Iwo Jima (Kikai) on 27 October 2020. Image was taken by the Iwanoue webcam. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, October 2nd year of Reiwa [2020]).

Geologic Background. Kikai is a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. It was the source of one of the world's largest Holocene eruptions about 6,300 years ago when rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake lava dome and Inamuradake scoria cone, as well as submarine lava domes. Historical eruptions have occurred at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km E of Tokara-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Tokara-Iojima.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Manam (Papua New Guinea) — October 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)


Intermittent ash plumes, thermal anomalies, and SO2 emissions in April-September 2020

Manam, located 13 km off the N coast of Papua New Guinea, is a basaltic-andesitic stratovolcano with historical eruptions dating back 400 years. Volcanism has been characterized by 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 period has been ongoing since 2014, typically with minor explosive activity, thermal activity, and SO2 emissions (BGVN 45:05). This reporting period updates information from April through September 2020, consisting of intermittent ash plumes from late July to mid-September, persistent thermal anomalies, and SO2 emissions. Information comes from Papua New Guinea's Rabaul Volcano Observatory (RVO), part of the Department of Mineral Policy and Geohazards Management (DMPGM), the Darwin Volcanic Ash Advisory Center (VAAC), and various satellite data.

Explosive activity was relatively low during April through late July; SO2 emissions and low power, but persistent, thermal anomalies were detected by satellite instruments each month. The TROPOMI instrument on the Sentinel-5P satellite recorded SO2 emissions, many of which exceeded two Dobson Units, that drifted generally W (figure 76). Distinct SO2 emissions were detected for 10 days in April, 4 days in May, 10 days in June, 4 days in July, 11 days in August, and 8 days in September.

Thermal anomalies recorded by the MIROVA (Middle InfraRed Observation of Volcanic Activity) system were sparse from early January through June 2020, totaling 11 low-power anomalies within 5 km of the summit (figure 77). From late July through September a pulse in thermal activity produced slightly stronger and more frequent anomalies. Some of this activity could be observed in Sentinel-2 thermal satellite imagery (figure 78). Occasionally, these thermal anomalies were accompanied by gas-and-steam emissions or ash plumes, as shown on 28 July. On 17 August a particularly strong hotspot was detected in the S summit crater. According to the MODVOLC thermal alert data, a total of 10 thermal alerts were detected in the summit crater over four days: 29 July (5), 16 August (1), and 3 (1) and 8 (3) September.

Figure (see Caption) Figure 76. Distinct sulfur dioxide plumes rising from Manam and drifting generally W were detected using data from the TROPOMI instrument on the Sentinel-5P satellite on 28 April (top left), 24 May (top right), 16 July (bottom left), and 12 September (bottom right) 2020. Courtesy of the NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 77. Intermittent thermal activity at Manam increased in power and frequency beginning around late July and continuing through September 2020, as shown on the MIROVA Log Radiative Power graph. Courtesy of MIROVA.
Figure (see Caption) Figure 78. Sentinel-2 thermal satellite images showing a persistent thermal anomaly (yellow-orange) at Manam’s summit craters (Main and South) each month during April through August; sometimes they were seen in both summit craters, as shown on 8 June (top right), 28 July (bottom left), and 17 August (bottom right). A particularly strong anomaly was visible on 17 August (bottom right). Occasional gas-and-steam emissions accompanied the thermal activity. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Activity during mid-July slightly increased compared to the previous months. On 16 July seismicity increased, fluctuating between low and moderate RSAM values through the rest of the month. In Sentinel-2 satellite imagery a gray ash plume was visible rising from the S summit crater on 28 July (figure 78). RSAM values gradually increased from a low average of 200 to an average of 1200 on 30 July, accompanied by thermal hotspots around the summit crater; a ground observer reported incandescent material was ejected from the summit. On 31 July into 1 August ash plumes rose to 4.3 km altitude, accompanied by an incandescent lava flow visible at the summit, according to a Darwin VAAC advisory.

Intermittent ash plumes continued to be reported by the Darwin VAAC on 1, 6-7, 16, 20, and 31 August. They rose from 2.1 to 4.6 km altitude, the latter of which occurred on 31 August and drifted W. Typically, these ash plumes extended SW, W, NW, and WSW. On 11 September another ash plume was observed rising 2.4 km altitude and drifting W.

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 basaltic-andesitic stratovolcano to its lower flanks. These 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 observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent 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; 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/); 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).

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Scientific Event Alert Network Bulletin - Volume 07, Number 10 (October 1982)

Managing Editor: Lindsay McClelland

Asamayama (Japan)

Abrupt seismic event increase; explosion two days later

Atmospheric Effects (1980-1989) (Unknown)

Ejecta from El Chichón reaches both poles; lidar and sunset observations

Cameroon (Cameroon)

Fissure eruption on upper SW flank; lava flow

Chichon, El (Mexico)

High H2S and NO in plume; slow diffusion of stratospheric cloud

Fuss Peak (Russia)

Increased thermal activity

Galunggung (Indonesia)

Explosions continue

Karymsky (Russia)

Lava dome fills crater before being destroyed by explosions

Kusatsu-Shiranesan (Japan)

Phreatic explosion; volcanic tremor

Langila (Papua New Guinea)

Vulcanian explosions; ashfalls; glow

Long Valley (United States)

More earthquake swarms

Lopevi (Vanuatu)

Ash emission

Manam (Papua New Guinea)

Ash emission; weak glow

Masaya (Nicaragua)

Small explosion; strong vapor emission; seismicity

Nyiragongo (DR Congo)

Lava lake level high, but growing at slower rate

Ruapehu (New Zealand)

No explosive activity

Soputan (Indonesia)

Strongest explosion since eruption began

St. Helens (United States)

SO2 emission declines; no deformation

Whakaari/White Island (New Zealand)

Localized inflation continues



Asamayama (Japan) — October 1982 Citation iconCite this Report

Asamayama

Japan

36.406°N, 138.523°E; summit elev. 2568 m

All times are local (unless otherwise noted)


Abrupt seismic event increase; explosion two days later

A small explosion occurred at 0958 on 2 October, after a sudden increase in seismicity to 108 events on 30 September then a decrease to five events the next day. The explosion caused slight ashfall on the N side of the volcano, and was accompanied by a ground shock with 2.0 µm amplitude recorded 2.0 km S of the summit.

After the 26 April explosion local seismicity had been at its usual level until July, when volcanic tremor was recorded for 15 minutes on the 6th. The level was again low until mid-August, then increased gradually in September, peaking on the 30th. On 7 October, 17 volcanic tremor events were recorded, but no explosion occurred; four were recorded the next day. As of 4 November no further explosions have been recorded, although seismicity has remained at a high level.

Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.

Information Contacts: JMA, Tokyo.


Atmospheric Effects (1980-1989) (Unknown) — October 1982 Citation iconCite this Report

Atmospheric Effects (1980-1989)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Ejecta from El Chichón reaches both poles; lidar and sunset observations

In late October and early November, a NASA Electra aircraft with a package of remote sensing instruments on board gathered data on El Chichón's stratospheric cloud from about 46°N to 46°S. Only very preliminary results were available at press time. Lidar profiles were collected over the entire flight path, optical depths of the atmosphere were determined by sun photometry at 13 wavelengths, and the total SO2 and O3 columns over the aircraft were measured. No dramatic changes in the position or morphology of the cloud appeared to have occurred since a similar flight (N Hemisphere only) 8-13 July. Stratospheric material was detected over the entire flight path, and M. P. McCormick believes that ejecta from El Chichón has reached both poles. As in July, there was a distinct boundary between the much more dense cloud at lower northern latitudes and more diffuse material farther from the volcano. The densest portion of the cloud extended only a few degrees farther N in November than in July. A similar boundary was found at lower southern latitudes. The strongest concentration of aerosols was typically at 23-24 km altitude, with the base of the cloud at about 21 km, but considerable variation in its morphology was observed.

From lower northern latitudes, ground-based lidar continued to detect stratospheric debris from El Chichón, but peak backscattering ratios were smaller and occurred at slightly lower altitudes in October than in September. Farther north, however, new layers have been observed since 3 November over Garmisch-Partenkirchen, West Germany.

Edward M. Brooks resumed daily sunrise and sunset observations from Jeddah, Saudi Arabia on 26 August. Between April and June, brilliant colors had been visible 40 minutes from sunrise and sunset, indicating material at 20-25 km altitude, but by October, only faint remnants of color could be seen that long before sunrise and after sunset. However, Brooks continued to see unusual colors, although somewhat nearer to sunrise and sunset, and at dawn on 21 October observed a brown NNW-SSE-trending band that looked like volcanic ash at 10° above the ESE horizon. In early November, the timing of the appearance and disappearance of color indicated that the layers being illuminated may have only been in the upper troposphere. H. H. Lamb observed brilliant sunsets from Norwich, England in early and mid-September, but reported that sunset colors were less spectacular, although still usually abnormal, by late October.

Geologic Background. 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 here.

Information Contacts: P. McCormick, NASA; T. DeFoor, MLO; M. Hirono, Kyushu Univ., Japan; S. Hayashida and A. Ono, Nagoya Univ., Japan; R. Reiter, Garmisch-Partenkirchen, W. Germany; E. Brooks, Saudi Arabia; H. Lamb, Univ. of East Anglia, England.


Cameroon (Cameroon) — October 1982 Citation iconCite this Report

Cameroon

Cameroon

4.203°N, 9.17°E; summit elev. 4095 m

All times are local (unless otherwise noted)


Fissure eruption on upper SW flank; lava flow

On 16 October, residents of Buea, ~10 km SE of the summit, were frightened by rumbling sounds and saw a red glow on the W flank. The next day, a helicopter making a survey flight over the area observed an eruption along a fissure ~6.5 km SW of the summit (on the SW border of the terminal plateau, at 4.15°N, 9.13°E). Steam was emitted from the upper part of the fissure, which began at 2,600 m altitude and trended NNE-SSW, parallel to the general tectonic trend. Basaltic lava emerged from the fissure at 2,500 m altitude and moved downslope at 20 km/hour in a 3-m-wide flow that reached forested areas. At night, glow from the lava was visible 50 km away. By 19 October, the active vent had built a cone 20 m high and 50 m in long dimension, and was emitting steam, ash, and lava fountains. Activity fluctuated 20-22 October, with periods of vigorous degassing lasting about 50 minutes. The crater included two active vents that ejected gas, ash, and bombs to 300-400 m height. Short, noisy explosions every 5-10 seconds made talking difficult 200 m from the crater. At 2450 m altitude, a lava flow poured out of the fissure at 20 km/hour. Newspapers reported some slowing of the lava advance during the night of 21-22 October, and by then the lava had moved through heavy rain forest to about 6 km from the seacoast village of Bakingili (population 300) on the SSW flank. Geologists reported that similar vent activity continued 22-30 October, and was audible 15-20 km away. On 30 October, the flow was about 200 m wide and 20 m thick, and its front had apparently stopped at 1,200 m above sea level. However, the eruption was reported to be continuing. Total lava output was estimated at 107 m3. Gas and aerosols were collected by a CNRS team. The eruption plume reached 4,000 m altitude. Total SO2 output was about 1,000 tons/day.

At press time, Fitton, Hughes, and Kilburn reported that the moderate lava outflow and Strombolian activity observed 7-8 November had declined to a very sluggish trickle on the 9th, and the eruption had apparently ended 10 November.

Most of the 300 inhabitants of Bakingili were evacuated, as were the residents of Tsonko (Isongo), a nearby coastal town. Larger towns and an oil refinery were not endangered by the current activity, but palm oil plantations have reportedly been damaged.

Geologic Background. Mount Cameroon, one of Africa's largest volcanoes, rises above the coast of west Cameroon. The massive steep-sided volcano of dominantly basaltic-to-trachybasaltic composition forms a volcanic horst constructed above a basement of Precambrian metamorphic rocks covered with Cretaceous to Quaternary sediments. More than 100 small cinder cones, often fissure-controlled parallel to the long axis of the 1400 km3 edifice, occur on the flanks and surrounding lowlands. A large satellitic peak, Etinde (also known as Little Cameroon), is located on the S flank near the coast. Historical activity was first observed in the 5th century BCE by the Carthaginian navigator Hannon. During historical time, moderate explosive and effusive eruptions have occurred from both summit and flank vents. A 1922 SW-flank eruption produced a lava flow that reached the Atlantic coast, and a lava flow from a 1999 south-flank eruption stopped only 200 m from the sea. Explosive activity from two vents on the upper SE flank was reported in May 2000.

Information Contacts: F. LeGuern, D. Polian, CNRS; B. Déruelle, F. Tchoua, Univ. of Yaoundé; Dr. Betah and Dr. Ngungi, Ministère des Mines et Energie, Yaoundé; Drs. Kergomard, Lorfsher, and Rousset, Elf Serepca, Douala; P. Vincent, Univ. de Clermont; Dr. Lonne, Ardic Cameroun Aerienne, Douala; G. Fitton, Univ. of Edinburgh; C. Kilburn, Univ. of London; D. Hughes, Portsmouth Polytechnic; Ambassador H. Horan, U.S. Embassy, Yaoundé; L. Matteson, U.S. Consulate, Douala; British Consulate, Douala; J. Baade and T. Humphrey, Gulf Oil, Douala; R. Shaw, IATA, Montreal; D. Haller, NOAA/NESS; Cameroon Tribune.


El Chichon (Mexico) — October 1982 Citation iconCite this Report

El Chichon

Mexico

17.36°N, 93.228°W; summit elev. 1150 m

All times are local (unless otherwise noted)


High H2S and NO in plume; slow diffusion of stratospheric cloud

As of early November, no new eruptive activity has been reported from El Chichón since the small ash ejection of 11 September described last month. Mexican and American geologists flew over the volcano on 4 November (during the NASA mission to observe the stratospheric cloud ejected 4 April). Little new vegetation could be seen on the volcano and 1ahar deposits were evident in stream valleys. The two crater lakes observed in September had combined into a single bright yellow-green lake that covered more than 80% of the crater floor. A sulfur slick covered the lake and sulfur deposits were visible along its shore. Vapor was emitted from 6-8 vents distributed around the shore and churning of the lake water indicated that gases were also emerging from sources beneath its surface. The gas emission fed a relatively diffuse, low-altitude plume that was visible within ~ 15 km of the volcano. Filter samples collected from the NASA aircraft showed that the plume was relatively poor in ash. The ratio of NO (measured by a chemoluminescent technique) to total sulfur gases (analyzed by flame photometry) was an order of magnitude higher in the El Chichón plume than at Arenal, Poás, Colima, and Mt. St. Helens during similar sampling in February. H2S made up more than 95% of the sulfur gases in the plume.

Michael Matson provided additional data on the initial heights and subsequent directions of movement of different layers of the eruption clouds from the largest El Chichón explosions (table 1). Blackbody temperatures of the tops of dense eruption columns are determined from GOES East geostationary weather satellite digital data, and are compared to temperature/altitude profiles from radiosondes launched from Veracruz, México (19.15°N, 96.12°W) at 0600 and 1800 daily. Note that the cloud top temperatures are usually for eruption columns that have just been ejected from the volcano and thus have not yet reached their maximum altitudes. Accurate temperatures cannot be assigned to diffuse plumes because data from the plume are mixed with data from the underlying terrain. However, their direction and speed of drift can be measured on a series of satellite images and then compared with known wind directions and speeds at various heights (in this case from the Veracruz radiosondes) to estimate altitudes.

Table 1. Determinations from satellite and radiosonde data of initial cloud top altitudes (rows with temperature and tropopause data) and later downwind drift of ejecta (rows with drift data) from the four largest explosions of El Chichón, March-April 1982. Altitudes could not be determined for the two largest clouds, marked by an asterisk (*) because they yielded unrealistically low temperatures, indicating that they did not radiate as perfect blackbodies, perhaps because of high tephra content. [Carey and Sigurdsson (1986) calculate average column altitudes of 20, 24, and 22 km respectively for the 29 March and the two 4 April explosions.]

Date Time Temperature (°C) Tropopause (km) Altitude (km) Direction of Drift
29 Mar 1982 0230 -75.2 16.5 16.3 --
  1500 -- -- 0-5.6 SW
    -- -- 10.4-15.2 NE
    -- -- 24 SW
03 Apr 1982 0400 -71.2 17 15.1 --
  0900 -- -- 0-4.9 SW
    -- -- 13.7-16.3 NE
  2200 -78.2 16.9 * --
04 Apr 1982 0100 -- -- 13.7-18.5 NE
    -- -- 20.7-24 SW
  0744 -83.0 16.9 * --
  1730 -- -- 9.2-20.7 NE
    -- -- 24-31 SW

Further Reference. Carey, S.N. and Sigurdsson, H., 1986, The 1982 Eruptions of El Chichón Volcano México (2): observations and numerical modelling of tephra-fall distribution: BV, v. 48, no. 2/3, p. 127-141.

Geologic Background. El Chichón is a small, but powerful trachyandesitic tuff cone and lava dome complex that occupies an isolated part of the Chiapas region in SE México far from other Holocene volcanoes. Prior to 1982, this relatively unknown volcano was heavily forested and of no greater height than adjacent nonvolcanic peaks. The largest dome, the former summit of the volcano, was constructed within a 1.6 x 2 km summit crater created about 220,000 years ago. Two other large craters are located on the SW and SE flanks; a lava dome fills the SW crater, and an older dome is located on the NW flank. More than ten large explosive eruptions have occurred since the mid-Holocene. The powerful 1982 explosive eruptions of high-sulfur, anhydrite-bearing magma destroyed the summit lava dome and were accompanied by pyroclastic flows and surges that devastated an area extending about 8 km around the volcano. The eruptions created a new 1-km-wide, 300-m-deep crater that now contains an acidic crater lake.

Information Contacts: J. Friend, Drexel Univ.; S. de la Cruz-Reyna, UNAM, México; M. Matson, NOAA/NESS.


Fuss Peak (Russia) — October 1982 Citation iconCite this Report

Fuss Peak

Russia

50.267°N, 155.246°E; summit elev. 1742 m

All times are local (unless otherwise noted)


Increased thermal activity

Recent aerial infrared surveys and ground investigations have shown increasing thermal activity at Fuss Peak. Gorshkov (1967) reported that there was no fumarolic activity at the volcano, E. K. Markhinin found only very minor signs of it in 1969, and fumaroles were not observed during 1971-1976 overflights. In 1973, an aerial infrared survey detected weak thermal anomalies over an area of about 104 m2 in the N and E parts of the crater and on its E rim (Gusev and Zelenov, 1979). When the volcano was resurveyed in 1978, intense thermal anomalies were measured over most of the 700-m-diameter crater, extending down to its bottom about 200 m below the rim. Weak fumaroles were observed in the E and central part of the crater. The 1978 resurvey also found a 50-80 m-wide zone of anomalously high temperatures extending 250-300 m down the E flank from the crater rim (Gusev and Zelenov, 1979). Fumaroles were seen on the E flank during an overflight in the fall of 1981.

G. S. Steinberg visited the volcano in September 1982 and found fumaroles at the base of both the W and E sides of the crater's small median ridge. Activity was stronger at the E base of the ridge, where there were two groups of fumaroles, each with three powerful vapor jets with temperatures of 95-96°C. Bright yellow sulfur crystals were present in some of the vents. Despite the fumaroles, the majority of the crater floor was snow-covered. Many weak fumaroles were observed in a zone of small fissures on the upper flank in the immediate vicinity of the crater rim, but none had deposited sulfur. About halfway down the cone, in a narrow, shallow canyon that was apparently an extension of the upper flank fissure zone, there were three groups of fumaroles, separated by 30-60 m, vigorously emitting a mixture of steam and other gases. Temperatures at these vents were 94-96°C and they had deposited bright yellow sulfur. Within the fissure zone, temperatures at 30-40 cm depth were 9-13°C. Temperatures at similar depths outside the zone were 3-4°C.

References. Gorshkov, G.S., 1967, Vulkanizm Kurilskoi Ostrovnoi Dugi: Nauka, Moscow, 288 p.

Gusev, N.A., and Zelenov, E.N., 1979, The activization of heat regime of the Fuss Peak volcano according to the heat aerial surveying: Volcanology and Seismology, no. 4, p. 102.

Geologic Background. Fuss Peak in the northern Kuriles forms a peninsula that lies across a low isthmus on the SW coast of Paramushir Island. The volcano rises 2800 m from the floor of the Sea of Okhotsk to a height of 1742 m. This isolated symmetrical andesitic stratovolcano has a 700-m-wide, steep-walled crater that is 300 m deep. A deep notch cuts the NW rim of the crater to the level of the crater floor, at the head of a canyon that reaches the coast. Well-preserved lava flows occupy the middle and lower flanks, particularly on the E and SE sides. Only one unambiguous historical eruption, in 1854, is known. Reports of eruptions in 1737, 1793, 1857, and 1859 are false (Gorshkov, 1970). Murayama (1987) also listed an eruption in 1742 (only earthquakes and a tsunami are cited by Sapper, 1917) and "smoke" emission in 1933.

Information Contacts: G. Steinberg, Sakhalin Complex Institute.


Galunggung (Indonesia) — October 1982 Citation iconCite this Report

Galunggung

Indonesia

7.25°S, 108.058°E; summit elev. 2168 m

All times are local (unless otherwise noted)


Explosions continue

Occasional explosions continued through early November. On 14 October, emission of thick grayish clouds was accompanied by intermittent thunderous rumbling sounds. An explosion at 1145 ejected ash that fell on the area around the volcano. At 1300, a GMS image showed a small plume moving SE. By the next image, three hours later, the plume was dispersing. After roughly two weeks of quiet, strong earthquakes were felt and several flashes of light preceded an explosion during the night of 3-4 November that ejected a thick cloud. Ash again fell near the volcano. GMS images showed a moderate to small plume from activity that probably began about 1700 on 4 November. The plume, which drifted SSE, was visible on the 1900 image but had dissipated four hours later. Inspection of satellite data revealed no other explosions, but the rainy season has begun in Indonesia and weather clouds are making eruption plumes considerably more difficult to detect by satellite.

Local authorities and villagers were building small dams near the volcano to prevent lahars from causing damage in river valleys during the rainy season.

Geologic Background. The forested slopes Galunggung in western Java are cut by a large horseshoe-shaped caldera breached to the SE that has served to channel the products of recent eruptions in that direction. The "Ten Thousand Hills of Tasikmalaya" dotting the plain below the volcano are debris-avalanche hummocks from the collapse that formed the breached caldera about 4,200 years ago. Historical eruptions have been infrequent and restricted to the central vent near the caldera headwall, but have caused much devastation. The first historical eruption in 1822 produced pyroclastic flows and lahars that killed over 4,000 people. A strong explosive eruption during 1982-1983 caused severe economic disruption to nearby populated areas.

Information Contacts: D. Haller, E. Hooper, and A. Smith, NOAA; AFP; Kantor Berita Antara, Jakarta.


Karymsky (Russia) — October 1982

Karymsky

Russia

54.049°N, 159.443°E; summit elev. 1513 m

All times are local (unless otherwise noted)


Lava dome fills crater before being destroyed by explosions

Lava dome growth continued in 1982, filling the crater by mid-year. Small to moderate explosions were frequent January-July. Less frequent but more violent explosions occurred in August and September, then decreased gradually and ended by 10-11 October. The lava dome was destroyed, leaving a bowl-shaped crater similar to that prior to the 1978 eruption.

Reference. Ivanov, B.V., Chirkov, A.M., Dubik, Yu. M., Khrenov, A.P., Dvigalo, V.N., Razina, A.A., Stepanov, V.V., and Chubarova, O.S., 1984, Active volcanoes of Kamchatka and Kurile Islands: status in 1982: Volcanology and Seismology, v. 6, p. 623-634 (English translation of paper in Volcanology and Seismology, 1984, no. 4, p. 104-110).

Geologic Background. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Information Contacts: see Reference.


Kusatsu-Shiranesan (Japan) — October 1982 Citation iconCite this Report

Kusatsu-Shiranesan

Japan

36.618°N, 138.528°E; summit elev. 2165 m

All times are local (unless otherwise noted)


Phreatic explosion; volcanic tremor

A brief phreatic explosion from three vents on 26 October ejected a dark column that rose 100 m above the lakes in two summit craters, Yugama and Karagama (figure 1). Onset time of the explosion was uncertain, but the seismograph at the Maebashi District Meteorological Observatory, 1.1 km NE of Yugama, began to record volcanic tremor with an amplitude of 0.2 µm at 0855. Gray plumes were recognized at 0905. The tremor gradually increased in amplitude and peaked about an hour after onset.

Figure (see Caption) Figure 1. Map of the summit region of Kusatsu-Shirane. Small circles indicate fumaroles; the other marks represent vents active since the 27 October 1982 eruption. An 'x' indicates an emission point of the 26 October 1982 eruption plume. The large open circle is Pit No. 6; the concentric circles are Pit No. 7. The solid circle is a new pit that formed on 13 November. Pits No. 2 and 3 (not shown) are on the W inner wall of Yugama. Courtesy of JMA.

Activity at Karagama ended at 0920, only 15 minutes after it was first recognized, and at 0930 activity at Yugama was reduced to white vapor emission (which ended the next day). Volcanic tremor, however, continued at peak levels for a few hours then gradually weakened, ceasing at 0124 on 30 October. A swarm of volcanic earthquakes lasting 5 hours was recorded on 26-27 October, and there was another minor swarm on [27] October.

JMA reported that a strong wind carried ash from as far as 3 km to the SE; ash was 1 mm thick on the crater rim. Tokiko Tiba reported a maximum of 3 cm of ash in the summit area. The total volume of ejecta was estimated to be 2,800-3,400 tons. No damage was reported. As of 2 November no further eruptions had been reported, and fumarolic activity in Yugama had declined. . . .

Geologic Background. The Kusatsu-Shiranesan complex, located immediately north of Asama volcano, consists of a series of overlapping pyroclastic cones and three crater lakes. The andesitic-to-dacitic volcano was formed in three eruptive stages beginning in the early to mid-Pleistocene. The Pleistocene Oshi pyroclastic flow produced extensive welded tuffs and non-welded pumice that covers much of the E, S, and SW flanks. The latest eruptive stage began about 14,000 years ago. Historical eruptions have consisted of phreatic explosions from the acidic crater lakes or their margins. Fumaroles and hot springs that dot the flanks have strongly acidified many rivers draining from the volcano. The crater was the site of active sulfur mining for many years during the 19th and 20th centuries.

Information Contacts: T. Tiba, National Science Museum, Tokyo; JMA, Tokyo.


Langila (Papua New Guinea) — October 1982 Citation iconCite this Report

Langila

Papua New Guinea

5.525°S, 148.42°E; summit elev. 1330 m

All times are local (unless otherwise noted)


Vulcanian explosions; ashfalls; glow

"The level of activity in October was similar to that observed in September. Grey and brown ash emissions from Crater 2 were seen on about 50% of days; otherwise, white vapours were emitted. Ashfalls in areas about 10 km from the volcano were reported on 4, 5, and 6 October. Vulcanian explosions were observed on 7 and 30 October. On the 7th a dark brown eruption column rose to about 3.5 km, and incandescent ejecta started fires in vegetation at the foot of the volcano. The explosion on the 30th was much smaller, the ash column rising only a few hundred meters. Crater 2 was more active from the 22nd. Crater glow was seen on 22, 24, and 25 October, and weak to strong rumbling sounds from the crater were heard on 22, 23, 24, 26, and 29 October.

"Crater 3 continued its low level of activity, releasing white and blue vapours in small volumes. Seismic activity remained at a low level. A few Vulcanian explosion earthquakes were recorded."

Geologic Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower E flank of the extinct Talawe volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the N and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: C. McKee, RVO.


Long Valley (United States) — October 1982 Citation iconCite this Report

Long Valley

United States

37.7°N, 118.87°W; summit elev. 3390 m

All times are local (unless otherwise noted)


More earthquake swarms

Occasional earthquake swarms have been located in the S side of the caldera, but the region that had been most active seismically has remained quiet since the swarm of 7-8 May. The earthquake swarms since 7-8 May have not included spasmodic tremor. Hypocenters for the swarms have typically been restricted to pipe-like zones. The typical swarm pattern has begun with a burst of deep events, followed by a shallow burst, then a series of events beneath the two.

On 19 September, 40-50 events occurred at depths of 3-6.5 km along an intracaldera branch of the Hilton Creek Fault, on the edge of the resurgent dome about 4 km NE of Casa Diablo Hot Springs (figure 1). The largest event , M 3.2, occurred well after the beginning of the swarm. Roughly 9 km to the WSW, a swarm of more than 100 shocks started 18 October. Most of the events occurred the first day, but a few continued through 24 October. All ranged from 3.5-6.5 km depth (most 5-6 km) and the maximum magnitude was 2.5. On 3 November at 0945, a swarm of more than 100 events began near a thermal area about 2.5 km N of the 19 September epicenters. Depths ranged from roughly 3.5-10 km and the maximum magnitude was 2.9. Only very small events were recorded after 2113.

Geologic Background. The large 17 x 32 km Long Valley caldera east of the central Sierra Nevada Range formed as a result of the voluminous Bishop Tuff eruption about 760,000 years ago. Resurgent doming in the central part of the caldera occurred shortly afterwards, followed by rhyolitic eruptions from the caldera moat and the eruption of rhyodacite from outer ring fracture vents, ending about 50,000 years ago. During early resurgent doming the caldera was filled with a large lake that left strandlines on the caldera walls and the resurgent dome island; the lake eventually drained through the Owens River Gorge. The caldera remains thermally active, with many hot springs and fumaroles, and has had significant deformation, seismicity, and other unrest in recent years. The late-Pleistocene to Holocene Inyo Craters cut the NW topographic rim of the caldera, and along with Mammoth Mountain on the SW topographic rim, are west of the structural caldera and are chemically and tectonically distinct from the Long Valley magmatic system.

Information Contacts: R. Bailey, USGS, Reston, VA; R. Cockerham, USGS, Menlo Park, CA; A. Ryall, University of Nevada, Reno.


Lopevi (Vanuatu) — October 1982 Citation iconCite this Report

Lopevi

Vanuatu

16.507°S, 168.346°E; summit elev. 1413 m

All times are local (unless otherwise noted)


Ash emission

A. Macfarlane reported that Lopevi ejected a black ash cloud on 24 October that rose to an altitude of about 6 km and drifted NW. Weather clouds prevented satellite observations until late that day, when no plume was visible. On 25 October, the area's first daylight image (at 0645) from the GOES West geostationary weather satellite showed a relatively diffuse plume extending about 250 km S from the volcano. By 0900, the far end of the cloud was roughly 500 km S of Lopevi and feeding appeared to be ending. The cloud had clearly begun to dissipate on the next image, an hour later. As of early November, no additional activity had been reported either in Vanuatu or by Solair pilots (who fly near Lopevi three days a week). Macfarlane notes that such activity at Lopevi is not unusual. Lopevi was last reported active on 12 September 1979, when small amounts of ash were emitted from cones on the SW flank.

Geologic Background. The small 7-km-wide conical island of Lopevi, known locally as Vanei Vollohulu, is one of Vanuatu's most active volcanoes. A small summit crater containing a cinder cone is breached to the NW and tops an older cone that is rimmed by the remnant of a larger crater. The basaltic-to-andesitic volcano has been active during historical time at both summit and flank vents, primarily along a NW-SE-trending fissure that cuts across the island, producing moderate explosive eruptions and lava flows that reached the coast. Historical eruptions at the 1413-m-high volcano date back to the mid-19th century. The island was evacuated following major eruptions in 1939 and 1960. The latter eruption, from a NW-flank fissure vent, produced a pyroclastic flow that swept to the sea and a lava flow that formed a new peninsula on the western coast.

Information Contacts: A. Macfarlane, Geological Survey, Vanuatu; F. Coulson, Ministry of Natural Resources, Solomon Islands; D. Haller, NOAA/NESS; R. Shaw, IATA.


Manam (Papua New Guinea) — October 1982 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)


Ash emission; weak glow

"Little change was noted in the mode of activity in October compared with activity in the second half of September. Both craters continued to produce pale, dark grey and brown ash-laden emissions in moderate quantities. Occasionally, an eruption column 0.5-1 km high was formed. Rumbling sounds were commonly heard coming from the S crater and occasionally from the main crater. The only instances of crater incandescence were observations of weak glow from the S crater on 13 and 14 October.

"Ashfalls were reported from the Sw and E coastal areas, about 5 km from the summit, on about 50% of days. Tiltmeter measurements showed no trends, and seismicity remained at a fairly low level."

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 basaltic-andesitic stratovolcano to its lower flanks. These 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 observed eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent 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: C. McKee, RVO.


Masaya (Nicaragua) — October 1982 Citation iconCite this Report

Masaya

Nicaragua

11.985°N, 86.165°W; summit elev. 594 m

All times are local (unless otherwise noted)


Small explosion; strong vapor emission; seismicity

A small, brief, explosive eruption from the bottom of the lava lake in Santiago Crater occurred at dawn on 7 October. Tephra, including blocks with volumes to 55 cm3, fell 300 m SE and covered an area of 150,000 m2. The eruption killed a few trees and animals near the summit. Heat from the ejecta melted asphalt on a road, which was also slightly damaged by impact from larger tephra. Rumbling and explosion sounds were heard through the day. After the initial explosion, no additional tephra was ejected, but gas emission increased considerably, forming wide vapor columns that reached high altitudes.

The eruption was preceded by a change in the pattern of seismicity and accompanied by a magnitude 2.3 event lasting 3.7 seconds. After the eruption, small earthquakes occurred about every 6 minutes until 1100 on 8 October.

The 7 October eruption was larger than Masaya's previous explosion on 26 December 1981 (7:1). Strong vapor emission has made observations of the bottom of the crater difficult, obscuring any changes that may have occurred to the lava lake.

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras caldera and is itself a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The Nindirí and Masaya cones, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6,500 years ago. Historical lava flows cover much of the caldera floor and there is a lake at the far eastern end. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals have caused health hazards and crop damage.

Information Contacts: G. Hodgson V., INETER.


Nyiragongo (DR Congo) — October 1982 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Lava lake level high, but growing at slower rate

By 23 July, lava from several vents had formed a lake about 300 m deep with an estimated volume of 36 x 106 m3. By mid-September, the volume of the lava lake had approximately doubled, but the eruption rate was declining slowly (table 1).

Table 1. Daily eruption rates at Nyiragongo over various time periods between 21 June and 15 September 1982. Calculated by M. Krafft.

Dates Eruption Rate (x 106 m3/day)
21-26 Jun 1982 0.2
27-30 Jun 1982 0.6
01-07 Jul 1982 2.5
08-21 Jul 1982 1.0
21-31 Jul 1982 0.5
01 Aug-15 Sep 1982 0.4

Geologists climbed to the crater rim on 31 July, 4 and 17 August, and 3 and 15 September. Between 24 and 31 July, the level of the lake surface rose about 20 m. On 4 August, however, the domical upwellings of lava that had marked the location of the 2 vents beneath the NW part of the lake on 23 July were not active. The entire surface of the lake was chilled and no glow was visible. On 17 August, an area of upwelling about 100 m in diameter and 10 m high was again active over one of the vents. A geologist descended to the surface of the lava lake 3 September and took samples. In hand specimen, these appeared to have a composition very similar to the melilite nephelinite of the 1928-1977 lake. A glowing red fissure that averaged about 30 cm wide and 20 cm deep ringed the lake ~2 m from its edge, emitting gases.

Between late July and 15 September, the lava lake continued to grow, raising its surface an additional 100 m to about 400 m below the highest point on the crater rim. The lake's average diameter on 15 September was 700 m, its depth was 400 m, and it contained ~70 x 106 m3 of lava. The zone of upwelling over the active vent was 250 m across and lava fountains reached a maximum height of 70 m. At the time of the 1977 eruption, the lava lake volume was ~20 x 106 m3 and the surface stood about 200 m from the crater rim. The surface of the more voluminous 1982 lava lake was roughly 200 m lower than that of the 1977 lake because morphological changes associated with the 1977 eruption considerably increased the volume of the crater.

Further References. Krafft, M. and Krafft, K., 1983, Le reapparition du lac de lave dans le cratère du volcan Nyiragongo de Juin a Septembre 1982 (Kivu-Zaire), histoire, dynamisme, debits et risques volcaniques: C.R. Acad. Sci. Paris, serie II, v. 296, p. 797-802.

Tazieff, H., 1984, Mt. Nyiragongo: Renewed activity of the lava lake: JVGR, v. 20, p. 267-280.

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

Information Contacts: M. Krafft, Cernay.


Ruapehu (New Zealand) — October 1982 Citation iconCite this Report

Ruapehu

New Zealand

39.28°S, 175.57°E; summit elev. 2797 m

All times are local (unless otherwise noted)


No explosive activity

Few changes have been observed since the end of July. NZGS personnel visited Ruapehu on 19-20 and 24 August, 17-18 September, and 21 October.

On all the visits the gray Crater Lake had yellow sulfur patches on its surface and minor to moderate upwelling in the center and near the N shore. Snow lay within 0.5 m of the water's edge and showed no sign of water surge. Water temperatures were 24°C on 24 August, 29° on 17 September, and 25° on 21 October. Magnesium concentration in the water has remained unchanged since February, but chloride concentration has increased. The Mg/Cl ratio has gradually declined from 0.130 in February to 0.115 on 24 August and 0.113 on 17 September. Deformation surveys indicated no apparent summit inflation.

Volcanic tremor has been recorded for some time and peaked in early September. The NZGS interpreted the low [normal] tremor frequency and the unchanged magnesium concentration to indicate that magma is still deep beneath Crater Lake. The increased chloride concentration suggested that gas can freely vent into the bottom of the lake, and the slow rate of lake refilling suggested that no shallow magmatic intrusion had occurred.

Geologic Background. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The dominantly andesitic 110 km3 volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake (Te Wai a-moe), is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3,000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys.

Information Contacts: P. Otway, NZGS, Wairakei; I. Nairn, B. Scott, NZGS, Rotorua; A. Cody, F.R.I., Rotorua.


Soputan (Indonesia) — October 1982 Citation iconCite this Report

Soputan

Indonesia

1.112°N, 124.737°E; summit elev. 1785 m

All times are local (unless otherwise noted)


Strongest explosion since eruption began

VSI reported that explosive activity resumed at 2045 on 9 November. Ash rose to ~5 km altitude and was blown NW, falling in the city of Amurang, 20 km away. A light ashfall was also reported at the VSI's Kakaskasen Observatory, 30 km N of Soputan. Newspapers reported that ash fell 40 km from the volcano and that within hours streets near the volcano were covered by as much as 10 cm of ash, halting traffic in many areas. VSI reported that rumbling and detonations accompanied the activity, and lightning flashes were observed at 4 km altitude. The eruption ended at about 1800 on 10 November, and no rumbling was heard that night.

A VSI seismograph at Silian, 6 km S of the volcano, recorded tremors for 4 hours before the eruption. The Teledyne seismograph, set at a magnification of 2,000, indicated a maximum amplitude of 6 mm during the early morning of 10 November and 4 mm in the afternoon. Deep (tectonic) earthquakes and two shallow volcanic events also preceded the explosive activity.

The GMS satelliteshowed no activity from Soputan at 1700, but on the next image, at 2000, there was a plume extending ~150 km W from the volcano. From the plume's development and rate of drift, satellite specialists estimated that gas emission had begun shortly after 1700, or well before the first explosive activity noticed on the ground at 2045. By 0200 on 10 November, relatively diffuse, apparently low-level material was drifting N and NW, while higher-altitude ejecta formed a dense plume that moved almost directly W. Satellite data continued to show feeding of the cloud through 1400 on 10 November. On the next image, at 1700, the cloud had separated from the volcano. By 2000, a plume with dense and diffuse patches extended from about 3°N, 123°E to 4°S, 117°E, a length of more than 1,000 km, and had a maximum width of ~500 km, considerably larger than the August and September plumes.

Further Reference. Sawada, Y., 1983, Attempt on surveillance of volcanic activity by eruption cloud image from artificial satellite: Bulletin of the Volcanological Society of Japan, v. 28, p. 357-373.

Geologic Background. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano is located SW of Riendengan-Sempu, which some workers have included with Soputan and Manimporok (3.5 km ESE) as a volcanic complex. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

Information Contacts: A. Sudradjat and Suratman, VSI; D. Haller and M. Matson, NOAA; Sinar Harapan, Jakarta; AFP.


St. Helens (United States) — October 1982 Citation iconCite this Report

St. Helens

United States

46.2°N, 122.18°W; summit elev. 2549 m

All times are local (unless otherwise noted)


SO2 emission declines; no deformation

Seismicity remained at background levels through early November, and no significant deformation has been measured. SO2 emission ranged from 20 to 70 t/d in October, the lowest rate since the eruption of 18 May 1980.

Geologic Background. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fujisan of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago and has been the most active volcano in the Cascade Range during the Holocene. Prior to 2,200 years ago, tephra, lava domes, and pyroclastic flows were erupted, forming the older edifice, but few lava flows extended beyond the base of the volcano. The modern edifice consists of basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the north flank, and were witnessed by early settlers.

Information Contacts: T. Casadevall, D. Swanson, USGS CVO, Vancouver, WA; S. Malone, University of Washington.


Whakaari/White Island (New Zealand) — October 1982 Citation iconCite this Report

Whakaari/White Island

New Zealand

37.52°S, 177.18°E; summit elev. 294 m

All times are local (unless otherwise noted)


Localized inflation continues

When NZGS personnel inspected the volcano on 8 October, two months after the last visit on 31 July, they found no new tephra deposits. There has been no significant tephra accumulation on the main crater floor since January 1982, the longest interval without deposition since the eruption began in December 1976. Much of the tephra cover in the W half of the main crater, where the fumaroles are, has been subjected to intense hydrothermal alteration.

Substantial steam columns were being emitted from vents on the floor and walls of 1978 Crater, and from Donald Mound and Noisy Nellie fumaroles. The strongest fumarolic activity was on the N side of 1978 Crater, near the new collapse pit. The small green pond in the SE part of the crater was still present; in a muddy black pond N of it, there was vigorous geysering. Fumarole temperatures measured at 4 places on the main crater floor ranged from 470°C in vents with low gas pressure to 695°C in high-pressure vents near Donald Mound.

Inflation of the Donald Mound area has continued at a steady rate. The E side had risen 9 mm since 31 July, and 58 mm since 21 May 1981 (figure 8), equivalent to 500 µrad of tilt. A deflationary trend was continuing about 200 m N of the Mound. The NZGS interpreted the inflation as a possible precursor of eruptive activity in this area.

Between 5 July and 1 October the number of low-frequency (B-type) seismic events did not exceed 10/day except in early July, when it increased to 31/day on the 9th and 10th, then declined. All the low-frequency events were small. High-frequency (volcano-tectonic) events usually numbered fewer than 5/day in this period, except as shown in table 4. These events were also generally small.

Table 4. Days between 5 July and 1 October 1982 when more than five high-frequency events were recorded at White Island.

Date Number of High-Frequency Events
18 Jul 1982 67
07 Aug 1982 9
15 Aug 1982 15
18 Aug 1982 8
28 Aug 1982 10
06 Sep 1982 11
14 Sep 1982 18

Moderately high frequency volcanic tremor began about 2200 on 28 July and gradually increased in amplitude until 0800 on 30 July, when a distinct decline in amplitude was apparent; tremor ceased by 1600 that day. Wide-band earthquake sequences indicative of eruption were recorded on 9, 15, and 26 September, but no eruptions were reported. Medium-frequency volcanic earthquakes were recorded on 16, 17, and 26 July, 14 August, and 4 and 18 September. The NZGS interpreted these as possible intrusive events.

Geologic Background. The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Information Contacts: I. Nairn and B. Scott, NZGS, Rotorua.

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