Logo link to homepage

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

Kavachi (Solomon Islands) Discolored water plumes observed in satellite imagery during early September 2020

Krakatau (Indonesia) Eruption ends in mid-April 2020, but intermittent thermal anomalies continue

Raung (Indonesia) Eruptions confirmed during 2012- 2013; lava fills inner crater in November 2014-August 2015

Klyuchevskoy (Russia) Strombolian activity, gas-and-steam and ash plumes, and a lava flow during June-early July 2020

Fuego (Guatemala) Ongoing explosions, ash plumes, lava flows, and lahars during April-July 2020

Nishinoshima (Japan) Major June-July eruption of lava, ash, and sulfur dioxide; activity declines in August 2020

Turrialba (Costa Rica) New eruptive period on 18 June 2020 consisted of ash eruptions

Etna (Italy) Effusive activity in early April; frequent Strombolian explosions and ash emissions during April-July 2020

Ol Doinyo Lengai (Tanzania) Multiple lava flows within the summit crater; September 2019-August 2020

Yasur (Vanuatu) Ash and gas explosions continue through August 2020

Villarrica (Chile) Continued summit incandescence February-August 2020 with larger explosions in July and August

Stromboli (Italy) Strombolian activity continues at both summit craters during May-August 2020



Kavachi (Solomon Islands) — October 2020 Citation iconCite this Report

Kavachi

Solomon Islands

8.991°S, 157.979°E; summit elev. -20 m

All times are local (unless otherwise noted)


Discolored water plumes observed in satellite imagery during early September 2020

Kavachi is an active submarine volcano in the SW Pacific, located in the Solomon Islands south of Gatokae and Vangunu islands. Volcanism has been characterized by phreatomagmatic explosions that ejected steam, ash, and incandescent bombs. The previous report described discolored water plumes extending from a single point during early 2018 and April 2020 (BGVN 45:05); similar activity was recorded for this current reporting period covering May through September 2020 and primarily using satellite data.

Activity at Kavachi is most frequently observed through satellite images and typically consists of discolored submarine plumes. On 2 September 2020 a slight yellow discoloration in the water was observed extending E from a specific point (figure 22). Similar faint plumes continued to be recorded on 5, 7, 12, and 17 September, each of which seemed to be drifting generally E from a point source above the summit where previous activity has occurred. On 7 September the discolored plume was accompanied by white degassing and possibly agitated water on the surface at the origin point (figure 22).

Figure (see Caption) Figure 22. Sentinel-2 satellite images of a discolored plume (light yellow) at Kavachi beginning on 2 September (top left) and continuing through 17 September 2020 (bottom right). The light blue circle on the 7 September image highlights the surface degassing and source of the discolored water plume. The white arrow on the bottom right image is pointing to the faint discolored plume. Images with “Natural color” rendering (bands 4, 3, 2); courtesy of Sentinel Hub Playground.

Geologic Background. Named for a sea-god of the Gatokae and Vangunu peoples, Kavachi is one of the most active submarine volcanoes in the SW Pacific, located in the Solomon Islands south of Vangunu Island. Sometimes referred to as Rejo te Kvachi ("Kavachi's Oven"), this shallow submarine basaltic-to-andesitic volcano has produced ephemeral islands up to 1 km long many times since its first recorded eruption during 1939. Residents of the nearby islands of Vanguna and Nggatokae (Gatokae) reported "fire on the water" prior to 1939, a possible reference to earlier eruptions. The roughly conical edifice rises from water depths of 1.1-1.2 km on the north and greater depths to the SE. Frequent shallow submarine and occasional subaerial eruptions produce phreatomagmatic explosions that eject steam, ash, and incandescent bombs. On a number of occasions lava flows were observed on the ephemeral islands.

Information Contacts: Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Krakatau (Indonesia) — October 2020 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 155 m

All times are local (unless otherwise noted)


Eruption ends in mid-April 2020, but intermittent thermal anomalies continue

Krakatau, located in the Sunda Strait between Indonesia’s Java and Sumatra Islands, experienced a major caldera collapse around 535 CE, forming a 7-km-wide caldera ringed by three islands. Presently, the caldera is underwater, except for three surrounding islands (Verlaten, Lang, and Rakata) and the active Anak Krakatau that was constructed within the 1883 caldera and has been the site of frequent eruptions since 1927. On 22 December 2018, a large explosion and flank collapse destroyed most of the 338-m-high island of Anak Krakatau (Child of Krakatau) and generated a deadly tsunami (BGVN 44:03). A larger explosion in December 2019 produced the beginnings of a new cone above the surface of crater lake (BGVN 45:02). The previous report (BGVN 45:06) described activity that included Strombolian explosions, ash plumes, and crater incandescence. This report updates information from June through September 2020 using information primarily from Indonesian Center for Volcanology and Geological Hazard Mitigation, also known as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and satellite data.

A VONA notice from PVMBG reported that the last eruptive event at Krakatau was reported on 17 April 2020, though the eruptive column was not observed. Activity after that was relatively low through September 2020, primarily intermittent diffuse white gas-and-steam emissions, according to PVMBG. No activity was reported during June-August, except for minor seismicity. During 11-13, 16, and 18 September, the CCTV Lava93 webcam showed intermittent white gas-and-steam emissions rising 25-50 m above the crater.

The MIROVA (Middle InfraRed Observation of Volcanic Activity) graph of MODIS thermal anomaly data showed intermittent hotspots within 5 km of the crater from May through September (figure 113). Some of these thermal hotspots were also detected in Suomi NPP/VIIRS sensor data. Sentinel-2 thermal satellite imagery showed faint thermal anomalies in the crater during June; no thermal activity was detected after June (figure 114).

Figure (see Caption) Figure 113. Intermittent thermal activity at Anak Krakatau from 13 October 2019-September 2020 shown on a MIROVA Low Radiative Power graph. The power of the thermal anomalies decreased after activity in April but continued intermittently through September. Courtesy of MIROVA.
Figure (see Caption) Figure 114. Sentinel-2 thermal satellite images showing a faint thermal anomaly in the crater during 1 (left) and 11 (right) June 2020. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

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/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).


Raung (Indonesia) — September 2020 Citation iconCite this Report

Raung

Indonesia

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

All times are local (unless otherwise noted)


Eruptions confirmed during 2012- 2013; lava fills inner crater in November 2014-August 2015

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. Visual reports of activity have often come from commercial airline flights that pass near the summit; 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 in 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. Confirmation and details of eruptions in 2012, 2013, and 2014-2015 are covered in this report with information provided by PVMBG, the Darwin Volcanic Ash Advisory Center (VAAC), several sources of satellite data, and visitors to the volcano.

Newly available visual and satellite information confirm eruptions at Raung during October 2012-January 2013, June-July 2013, and extend the beginning of the 2015 eruption back to November 2014. The 2015 eruption was the largest in several decades; Strombolian activity was reported for many months and fresh lava flows covered the crater floor. Raung was quiet after the 2015 eruption ended in August of that year until July 2020.

Eruption during October 2012-January 2013. A MODVOLC thermal alert appeared inside the summit crater of Raung on 14 October 2012, followed by another four alerts on 16 October. Multiple daily alerts were reported on many days through 8 November, most within the main crater. Single alerts appeared on 29 November and 1 December 2012 (figure 9). PVMBG raised the Alert Level on 17 October from 1 to 2 due to increased seismicity and raised it further to Level 3 on 22 October. A local news report by Aris Yanto indicted that a minor Strombolian eruption occurred inside the crater on 19 October. Strombolian activity was also observed inside the inner crater on 5 November 2012 by visitors (figure 10); they reported loud rumbling sounds that could be heard up to 15 km from the crater.

Figure (see Caption) Figure 9. Thermal activity at Raung during October and November 2012 included multiple days of multi-pixel anomalies, with almost all activity concentrated within the summit crater. Strombolian activity was observed on 5 November. Image shows all pixels from 23 September-1 December 2012. Courtesy of MODVOLC.
Figure (see Caption) Figure 10. Strombolian activity was observed inside the inner crater of Raung on 5 November 2012 by visitors. They reported loud rumbling sounds that could be heard up to 15 km from the crater. Photo by Galih, courtesy of Volcano Discovery.

The Darwin VAAC issued an advisory of an eruption plume to 9.1 km altitude reported at 0237 UTC on 8 November 2012. In a second advisory about two hours later they noted that an ash plume was not visible in satellite imagery. A press article released by the Center for Volcanology and Geological Hazard Mitigation (PVMBG) indicated that gray ash plumes were observed on 6 January 2013 that rose 300 m above the summit crater rim. Incandescence was observed around the crater and thundering explosions were heard by nearby residents.

Eruption during June-July 2013. Two MODVOLC thermal alerts were measured inside the summit crater on 29 June 2013. A photo taken on 21 July showed minor Strombolian activity at the inner crater (figure 11). A weak SO2 anomaly was detected in the vicinity of Raung by the OMI instrument on the Aura satellite on 27 July. Thermal alerts were recorded on 29 and 31 July. When Google Earth imageryrom 14 March 2011 created by Maxar Technologies is compared with imagery from 29 July 2013 captured by Landsat/Copernicus, dark tephra is filling the inner crater in the 2013 image; it was not present in 2011 (figure 12).

Figure (see Caption) Figure 11. Strombolian activity was observed inside the inner crater at the summit of Raung on 21 July 2013. Photo by Agus Kurniawan, courtesy of Volcano Discovery.
Figure (see Caption) Figure 12. Satellite imagery from Google Earth showing the eroded pyroclastic cone inside the summit crater of Raung on 14 March 2011 (left) and 29 July 2013 (right). Dark tephra deposits filling the inner crater in the 2013 image were not present in 2011. The crater of the pyroclastic cone is 200 m wide; N is to the top of the images. Courtesy of Google Earth.

Eruption during November 2014-August 2015. Information about this eruption was previously reported (BGVN 41:12), but additional details are provided here. Landsat-8 imagery from 28 October 2014 indicated clear skies and little activity within the summit crater. Local observers reported steam plumes beginning in mid-November (figure 13). MODVOLC thermal alerts within the summit crater were issued on 28 and 30 November, and then 15 alerts were issued on seven days in December. Thermal Landsat-8 imagery from cloudy days on 29 November and 15 December indicated an anomaly over the area of the pyroclastic cone inside the summit crater (figure 14).

Figure (see Caption) Figure 13. Local observers reported steam plumes at Raung beginning in mid-November 2014; this one was photographed on 17 November 2014. Courtesy of Volcano Discovery.
Figure (see Caption) Figure 14. Satellite evidence of new eruptive activity at Raung first appeared on 29 November 2014. The true color-pansharpened Landsat-8 image of Raung from 28 October 2014 (left) shows the summit crater and an eroded pyroclastic cone with its own crater (the inner crater) with no apparent activity. Although dense meteoric clouds on 29 November (center) and 15 December 2014 (right) blocked true color imagery, thermal imagery indicated a thermal anomaly from the center of the pyroclastic cone on both dates. Courtesy of Sentinel Hub Playground.

In January 2015 the MODVOLC system identified 25 thermal anomalies in MODIS data, with a peak of eight alerts on 8 January. Visitors to the summit crater on 6 January witnessed explosions from the inner crater approximately every 40 minutes that produced gas and small amounts of ash and tephra. They reported lava flowing continuously from the inner crater onto the larger crater floor, and incandescent activity was seen at night (figure 15). Landsat-8 images from 16 January showed a strong thermal anomaly covering an area of fresh lava (figure 16).

Figure (see Caption) Figure 15. Visitors to the summit crater of Raung on 6 January 2015 witnessed explosions from the inner crater approximately every 40 minutes that produced abundant gas and small amounts of ash and tephra. Lava was flowing continuously from the inner crater onto the larger crater floor, and incandescent activity was observed at night. Photos by Sofya Klimova, courtesy of Volcano Discovery.
Figure (see Caption) Figure 16. On a clear 16 January 2015, Landsat-8 satellite imagery revealed fresh lava flows NW of the pyroclastic cone within the summit crater at Raung. A strong thermal anomaly matches up with the dark material, suggesting that it flowed NW from within the pyroclastic cone. Left image is true color-pansharpened rendering, right image is thermal rendering. Courtesy of Sentinel Hub Playground.

Satellite images were obscured by meteoric clouds during February 2015, but PVMBG reported gray and brown plumes rising 300 m multiple times and incandescence and rumbling on 14 February. Visitors to the summit crater during the second half of February reported Strombolian activity with lava fountains from the inner crater, at times as frequently as every 15 minutes (figure 17). Loud explosions and rumbling were heard 10-15 km away. MODVOLC thermal alerts stopped on 25 February and did not reappear until late June.

Figure (see Caption) Figure 17. A report issued on 25 February 2015 from visitors to the summit of Ruang noted large Strombolian explosions with incandescent ejecta and lava flowing across the crater floor. The fresh lava on the crater floor covered a noticeably larger area than that shown in early January (figure 15). Photo by Andi, courtesy of Volcano Discovery.

PVMBG raised the Alert Level to 2 in mid-March 2015. Weak thermal anomalies located inside and NW of the pyroclastic cone were present in satellite imagery on 21 March. PVMBG reported gray and brown emissions during March, April, and May rising as high as 300 m above the crater. Landsat imagery from 22 April showed a small emission inside the pyroclastic cone, and on 8 May showed a clearer view of the fresh black lava NW and SW of the pyroclastic cone (figure 18).

Figure (see Caption) Figure 18. Fresh lava was visible in Landsat-8 satellite imagery in April and May 2015 at Raung. A small emission was present inside the pyroclastic cone at the summit of Raung on 22 April 2015 (left). Fresh dark material is also evident in the SW quadrant of the summit crater that was not visible on 16 January 2015. A clear view on 8 May 2015 also shows the extent of the fresh black material around the pyroclastic cone (right). The summit crater is 2 km wide. Courtesy of Sentinel Hub Playground.

Nine MODVOLC thermal alerts appeared inside the summit crater on 21 June 2015 after no alerts since late February, suggesting an increase in activity. The Darwin VAAC issued the first ash advisory for 2015 on 24 June noting an aviation report of recent ash. The following day the Ujung Pandang Meteorological Weather Office (MWO) reported an ash emission drifting W at 3.7 km altitude. The same day, 25 June, Landsat-8 imagery clearly showed a new lava flow on the W side of the crater and a strong thermal anomaly. The thermal data showed a point source of heat widening SW from the center of the crater and a second point source of heat that appeared to be inside the pyroclastic cone. A small ash plume was visible over the cone (figure 19). Strombolian activity and ash plumes were reported by BNPB and PVMBG in the following days. On 26 June the Darwin VAAC noted the hotspot had remained visible in infrared imagery for several days. PVMBG reported an ash emission to 3 km altitude on 29 June.

Figure (see Caption) Figure 19. A new lava flow and strong thermal anomaly appeared inside the summit crater of Raung on 25 June 2015 in Landsat-8 imagery. The new flow was visible on the W side of the crater. The darker area extending SW from the rising ash plume is a shadow. The thermal data showed a point source of heat widening SW from the center of the crater and spreading out in the SW quadrant and a second point source of heat on the flank of the pyroclastic cone. Left image is True color-pansharpened rendering, and right image is thermal rendering. Courtesy of Sentinel Hub Playground.

Activity increased significantly during July 2015 (BGVN 41:12). Ash plumes rose as high as 6.7 km altitude and drifted hundreds of kilometers in multiple directions, forcing multiple shutdowns at airports on Bali and Lombok, as well as Banyuwangi and Jember in East Java. The Darwin VAAC issued 152 ash advisories during the month. Ashfall was reported up to 20 km W during July and 20-40 km SE during early August. Visitors to the summit in early July observed a new pyroclastic cone growing inside the inner crater from incandescent ejecta and dense ash emissions (figure 20). Landsat-8 imagery from 11 July showed a dense ash plume drifting SE, fresh black lava covering the 2-km-wide summit caldera floor, and a very strong thermal anomaly most intense at the center near the pyroclastic cone and cooler around the inner edges of the crater (figure 21). On 12 July, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured a view of an ash-and-gas plume drifting hundreds of kilometers SE from Raung (figure 22).

Figure (see Caption) Figure 20. A new pyroclastic cone was growing inside the inner crater at the summit of Raung when photographed by Aris Yanto in early July 2015. Courtesy of Volcano Discovery.
Figure (see Caption) Figure 21. Landsat-8 imagery of Raung during July 2015 indicated dense ash emissions and a large thermal anomaly caused by fresh lava. On 11 July a dense ash plume drifted SE and a strong thermal anomaly was centered inside the summit crater. The 2-km-wide crater floor was covered with fresh lava (compare with 25 June image in figure 19). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 22. On 12 July 2015 the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured a natural-color view of a plume of ash and volcanic gases drifting hundreds of kilometers SE from Raung. Courtesy of NASA Earth Observatory.

A satellite image on 20 July showed fresh incandescent lava covering the floor of the summit crater and a dense ash plume drifting N from the summit (figure 23). Incandescent ejecta emerged from two vents on the new pyroclastic cone inside the inner crater on 26 July (figure 24). On 27 July a dense ash plume was visible again in satellite imagery drifting NW and the hottest part of the thermal anomaly was in the SE quadrant of the crater (figure 25). Substantial SO2 plumes were recorded by the OMI instrument on the Aura satellite during July and early August 2015 (figure 26).

Figure (see Caption) Figure 23. A satellite image of the summit of Raung on 20 July 2015 showed fresh, incandescent lava covering the floor of the summit crater and a dense ash plume drifting N from the summit. Thermal activity on the NE flank was likely the result of incandescent ejecta from the crater causing a fire. Image created by DigitalGlobe, captured by WorldView3, courtesy of Volcano Discovery.
Figure (see Caption) Figure 24. Incandescent ejecta emerged from two vents on the new pyroclastic cone growing inside the inner crater of Raung on 26 July 2015. Photo by Vianney Tricou, used with permission, courtesy of Volcano Discovery.
Figure (see Caption) Figure 25. Landsat-8 imagery of Raung during July 2015 indicated dense ash emissions and large thermal anomalies from fresh lava. The 2-km-wide crater floor was fully covered with fresh lava by 11 July. On 27 July the dense ash plume was drifting NW and the highest heat was concentrated in the SE quadrant of the crater. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 26. Substantial plumes of sulfur dioxide from Raung were measured by the OMI instrument on the AURA satellite during July and August 2015. The first plumes were measured in mid-June; they intensified during the second half of July and the first week of August, but had decreased by mid-August. Wind directions were highly variable throughout the period. The date is recorded above each image. Courtesy of NASA Global Sulfur Dioxide Page.

Significant ash emissions continued into early August 2015 with numerous flight cancellations. The Darwin VAAC reported ash plumes rising to 5.2 km altitude and extending as far as 750 km SE during the first two weeks in August (figure 27). Satellite imagery indicated a small ash plume drifting W from the center of the crater on 12 August and weak thermal anomalies along the E and S rim of the floor of the crater (figure 28). The summit crater was covered with fresh lava on 14 August when viewed by visitors, and ash emissions rose a few hundred meters above the crater rim from a vent in the SW side of the pyroclastic cone (figure 29). The visitors observed pulsating ash emissions rising from the SW vent on the large double-crater new cinder cone. The larger vent to the NE was almost entirely inactive except for two small, weakly effusive vents on its inner walls.

Figure (see Caption) Figure 27. A dense ash plume drifted many kilometers S from Raung on 2 August 2015 in this view from nearly 100 km W. Incandescence at the summit indicated ongoing activity from the major 2015 eruption. In the foreground is Lamongan volcano whose last known eruption occurred in 1898. Courtesy of Øystein Lund Andersen, used with permission.
Figure (see Caption) Figure 28. Landsat-8 satellite imagery of Raung indicated a small ash plume drifting W from the center of the crater on 12 August 2015. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 29. The summit crater of Raung on 14 August 2015 was filled with fresh lava from an eruption that began in November 2014. Ash emissions from a vent in the side of the newly grown pyroclastic cone within the crater rose a few hundred meters above the crater rim. Courtesy of Volcano Discovery.

The lengthy sequence of multiple daily VAAC reports that began in late June ended on 16 August 2015 with reports becoming more intermittent and ash plume heights rising to only 3.7-3.9 km altitude. Multiple discontinuous eruptions to 3.9 km altitude were reported on 18 August. The plumes extended about 100 km NW. The last report of an ash plume was from an airline on 22 August noting a low-level plume 50 km NW. Two MODVOLC alerts were issued that day. By 28 August only a very small steam plume was present at the center of the crater; the southern half of the edge of the crater floor still had small thermal anomalies (figure 30). The last single MODVOLC thermal alerts were on 29 August and 7 September. The Alert Level was lowered to 2 on 24 August 2015, and further lowered to 1 on 20 October 2016.

Figure (see Caption) Figure 30. By 28 August 2015 only a very small steam plume was present at the center of the summit crater of Raung, and the southern half of the edge of the crater floor only had weak thermal anomalies from cooling lava. 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/); 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/); 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/);Google Earth (URL: https://www.google.com/earth/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/, https://earthobservatory.nasa.gov/images/86213/eruption-of-raung-volcano); Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); Aris Yanto (URL: https://www.exploredesa.com/2012/11/mount-raung-produce-of-vulcanic-ash-plume-and-continue-eruption/); DigitalGlobe (URL: https://www.maxar.com/, https://twitter.com/Maxar/status/875449111398547457); Øystein Lund Andersen (URL: https://twitter.com/OysteinVolcano/status/1194879946042142726, http://www.oysteinlundandersen.com).


Klyuchevskoy (Russia) — September 2020 Citation iconCite this Report

Klyuchevskoy

Russia

56.056°N, 160.642°E; summit elev. 4754 m

All times are local (unless otherwise noted)


Strombolian activity, gas-and-steam and ash plumes, and a lava flow during June-early July 2020

Klyuchevskoy is a frequently active stratovolcano located in northern Kamchatka. Historical eruptions dating back 3,000 years have included more than 100 flank eruptions with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks. The previous report (BGVN 45:06) described ash plumes, nighttime incandescence, and Strombolian activity. Strombolian activity, ash plumes, and a strong lava flow continued. This report updates activity from June through August 2020 using weekly and daily reports from the Kamchatkan Volcanic Eruption Response Team (KVERT), the Tokyo Volcanic Ash Advisory (VAAC), and satellite data.

Moderate explosive-effusive activity continued in June 2020, with Strombolian explosions, frequent gas-and-steam emissions that contained some amount of ash, and an active lava flow. On 1 June a gas-and-steam plume containing some ash extended up to 465 km SE and E. The lava flow descended the SE flank down the Apakhonchich chute (figure 43). Occasionally, phreatic explosions accompanied the lava flow as it interacted with snow. Intermittent ash plumes, reported throughout the month by KVERT using video and satellite data and the Tokyo VAAC using HIMAWARI-8 imagery, rose to 5.5-6.7 km altitude and drifted in different directions up to 34 km from the volcano. On 12 and 30 June ash plumes rose to a maximum altitude of 6.7 km. On 19 June, 28-30 June, and 1-3 July some collapses were detected alongside the lava flow as it continued to advance down the SE flank.

Figure (see Caption) Figure 43. Gray ash plumes (left) and a lava flow descending the Apakhonchich chute on the SE flank, accompanied by a dark ash plume and Strombolian activity (right) were observed at the summit of Klyuchevskoy on 10 June 2020. Courtesy of E. Saphonova, IVS FEB RAS, KVERT.

During 1-3 July moderate Strombolian activity was observed, accompanied by gas-and-steam emissions containing ash and a continuous lava flow traveling down the Apakhonchich chute on the SE flank. On 1 July a Tokyo VAAC advisory reported an ash plume rising to 6 km altitude and extending SE. On 3 July the activity sharply decreased. KVERT reported there was some residual heat leftover from the lava flow and Strombolian activity that continued to cool through at least 13 July; KVERT also reported frequent gas-and-steam emissions, which contained a small amount of ash through 5 July, rising from the summit crater (figure 44). The weekly KVERT report on 16 July stated that the eruption had ended on 3 July 2020.

Figure (see Caption) Figure 44. Fumarolic activity continued in the summit crater of Klyuchevskoy on 7 July 2020. Courtesy of KSRS ME, Russia, KVERT.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows frequent and strong thermal activity within 5 km of the summit crater from March through June followed by a sharp and sudden decline in early July (figures 45). A total of six weak thermal anomalies were detected between July and August. According to the MODVOLC thermal algorithm, a total of 111 thermal alerts were detected at or near the summit crater from 1 June to 1 July, a majority of which were due to the active lava flow on the SE flank and Strombolian explosions in the crater. Sentinel-2 thermal satellite imagery frequently showed the active lava flow descending the SE flank as a strong thermal anomaly, sometimes even through weather clouds (figure 46). These thermal anomalies were also recorded by the Sentinel-2 MODIS Thermal Volcanic Activity data on a MIROVA graph, showing a strong cluster during June to early July, followed by a sharp decrease and then a hiatus in activity (figure 47).

Figure (see Caption) Figure 45. Thermal activity at Klyuchevskoy was frequent and strong during February through June 2020, according to the MIROVA graph (Log Radiative Power). Activity sharply decreased during July through August with six low-power thermal anomalies. Courtesy of MIROVA.
Figure (see Caption) Figure 46. Sentinel-2 thermal satellite images show the strong and persistent lava flow (bright yellow-orange) originating from the summit crater at Klyuchevskoy from 1 June through 1 July 2020. The lava flow was active in the Apakhonchich chute on the SE flank. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 47. Strong clusters of thermal anomalies were detected in the summit at Klyuchevskoy (red dots) during January through June 2020, as recorded by the Sentinel-2 MODIS Thermal Volcanic Activity data (bands 12, 11, 8A). Activity sharply decreased during July through August with few low-power thermal anomalies. Courtesy of MIROVA.

Geologic Background. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank 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/); 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/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Fuego (Guatemala) — September 2020 Citation iconCite this Report

Fuego

Guatemala

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

All times are local (unless otherwise noted)


Ongoing explosions, ash plumes, lava flows, and lahars during April-July 2020

Fuego, located in Guatemala, is a stratovolcano that has been erupting since 2002 with historical eruptions dating back to 1531. Volcanism is characterized by major ashfalls, pyroclastic flows, lava flows, and lahars. The previous report (BGVN 45:04) described recent activity that included multiple ash explosions, block avalanches, and intermittent lava flows. This report updates activity from April through July 2020 that consisted of daily explosions, ash plumes, block avalanches ashfall, intermittent lava flows, and lahars. The primary source of information comes from the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH), the Washington Volcanic Ash Advisory Center (VAAC), and various satellite data.

Summary of activity during April-July 2020. Daily activity throughout April-July 2020 was characterized by multiple hourly explosions, ash plumes that rose to a maximum of 4.9 km altitude, incandescent pulses that reached 600 m above the crater, block avalanches into multiple drainages, and ashfall affecting nearby communities (table 21). The highest rate of explosions occurred on 2 and 3 April and 2 May with up to 16 explosions per hour. White degassing occurred frequently during the reporting period, rising to a maximum altitude of 4.5 km and drifting in multiple directions. Intermittent lava flows were observed each month in the Seca (Santa Teresa) and Ceniza drainages (figure 132); the number of flows decreased in June through July, which is represented in the MIROVA analysis of MODIS satellite data, where the strength and frequency of thermal activity slightly decreased (figure 133). Occasional lahars were detected descending several drainages on the W and SE flanks, sometimes carrying tree branches and large blocks up to 1 m in diameter.

Table 21. Activity summary by month for Fuego with information compiled from INSIVUMEH daily reports.

Month Number of explosions per hour Ash plume heights (km) Ash plume distance (km) and direction Drainages affected by block avalanches Villages reporting ashfall
Apr 2020 5-16 4.3-4.9 km 8-20 km E, NE, SE, W, NW, SW, S, N Taniluyá, Ceniza, Las Lajas, Trinidad, Seca, Honda, and Santa Teresa Morelia, Panimaché I and II, Sangre de Cristo, Santa Sofía, Finca Palo Verde, San Pedro Yepocapa, Las Cruces Quisache, La Rochela, Ceylan, and Osuna
May 2020 4-16 4.3-4.9 km 10-17 km S, SW, W, N, NE, E, SE Trinidad, Taniluyá, Ceniza, Las Lajas, Santa Teresa, Seca, and Honda Panimaché I, La Rochela, Ceilán, Morelia, San Andrés Osuna, Finca Palo Verde, Santa Sofía, Seilán, San Pedro Yepocapa, Alotenango, Ciudad Vieja, San Miguel Dueñas, and Antigua Guatemala
Jun 2020 3-15 4.2-4.9 km 10-25.9 km E, SE, S, N, NE, W, SW, NW Seca, Taniluyá, Ceniza, Trinidad, Las Lajas, Santa Teresa and Honda San Pedro Yepocapa, Sangre de Cristo, Panimaché I and II, Morelia, Finca Palo Verde, El Porvenir, Yucales, Santa Emilia, Santa Sofía
Jul 2020 1-15 4-4.9 km 10-24 km W, NW, SW, S, NE Trinidad, Taniluyá, Ceniza, Honda, Las Lajas, Seca, and Santa Teresa Panimaché I and II, Morelia, Santa Sofía, Finca Palo Verde, Sangre de Cristo, San Pedro Yepocapa, and El Porvenir
Figure (see Caption) Figure 132. Sentinel-2 thermal satellite images of Fuego between 9 April 2020 and 13 July 2020 showing lava flows (bright yellow-orange) traveling generally S and W from the summit crater. Some lava flows were accompanied by gas emissions (9 April, 9 May, and 24 May 2020). Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 133. Thermal activity at Fuego was persistent and strong from 16 September through late May 2020, according to the MIROVA graph (Log Radiative Power). From early to mid-June activity seemed to stop briefly before resuming again at a lower rate. Courtesy of MIROVA.

Activity during April-May 2020. Activity in April 2020 consisted of 5-16 explosions per hour, generating ash plumes that rose 4.3-4.9 km altitude and drifted 8-20 km in multiple directions. Ashfall was reported in Morelia (9 km SW), Panimaché I and II (8 km SW), Sangre de Cristo (8 km WSW), Santa Sofía (12 km SW), Finca Palo Verde, San Pedro Yepocapa (8 km NW), Las Cruces Quisache (8 km NW), La Rochela, Ceylan, Osuna (12 km SW). The Washington VAAC issued multiple aviation advisories for a total of six days in April. Intermittent white gas-and-steam emissions reached 4.1-4.5 km altitude drifting in multiple directions. Incandescent ejecta was frequently observed rising 75-400 m above the crater; material ejected up to 600 m above the crater on 11 April. These constant explosions produced block avalanches that traveled down the Taniluyá (SW), Ceniza (SSW), Las Lajas (SE), Trinidad (S), Seca (W), Honda, and Santa Teresa (W) drainages. Effusive activity was reported on 6-13 and 15 April from the summit vent, traveling 150-800 m down the Ceniza drainage, accompanied by block avalanches in the front of the flow up to 1 km. Crater incandescence was also observed.

On 19-20 April a new lava flow descended the Ceniza drainage measuring 200-400 long, generating incandescent block avalanches at the front of the flow that moved up to 1 km. On 22 April lahars descended the Honda, Las Lajas, El Juté (SE), Trinidad, Ceniza, Taniluyá, Mineral, and Seca drainages and tributaries in Guacalate, Achiguate, and Pantaleón. During the evening of 23 April the rate of effusive activity increased; observatory staff observed a second lava flow in the Seca drainage was 170 m long and incandescent blocks from the flow traveled up to 600 m. Two lava flows in the Ceniza (130-400 m) and Seca (150-800 m) drainages continued from 23-28 April and had stopped by 30 April. On 30 April weak and moderate explosions produced ash plumes that rose 4.5-4.7 km altitude drifting S and SE, resulting in fine ashfall in Panimaché I, Morelia, Santa Sofía (figure 134).

Figure (see Caption) Figure 134. Photo of a small ash plume rising from Fuego on 30 April 2020. Photo has been slightly color corrected. Courtesy of William Chigna, CONRED.

During May 2020, the rate of explosion remained similar, with 4-16 explosions per hour, which generated gray ash plumes that rose 4.3-4.9 km altitude and drifted 10-17 km generally W and E. Ashfall was observed in Panimaché I, La Rochela, Ceilán, Morelia, San Andrés Osuna, Finca Palo Verde, Santa Sofía, Seilán, San Pedro Yepocapa, Alotenango (8 km ENE), Ciudad Vieja (13.5 km NE), San Miguel Dueñas (10 km NE), and Antigua Guatemala (18 km NE). The Washington VAAC issued volcanic ash advisory notices on six days in May. White gas-and-steam emissions continued, rising 4-4.5 km altitude drifting in multiple directions. Incandescent ejecta rose 100-400 m above the crater, accompanied by some crater incandescence and block avalanches in the Trinidad, Taniluyá, Ceniza, Las Lajas, Santa Teresa, Seca, and Honda drainages that moved up to 1 km and sometimes reached vegetated areas.

During 8-11 May a new 400 m long lava flow was detected in the Ceniza drainage, accompanied by constant crater incandescence and block avalanches traveling up to 1 km, according to INSIVUMEH. On 8 and 17 May moderate to strong lahars descended the Santa Teresa and Mineral drainages on the W flank and on 21 May they descended the Las Lajas drainage on the E flank and the Ceniza drainage on the SW flank. During 20-24 May a 100-400 m long lava flow was reported in the Ceniza drainage alongside degassing and avalanches moving up to 1 km and during 25-26 May a 150 m long lava flow was reported in the Seca drainage.

Activity during June-July 2020. The rate of explosions in June 2020 decreased slightly to 3-15 per hour, generating gray ash plumes that rose 4.2-4.9 km altitude and drifted 10-26 km in multiple directions (figure 135). As a result, intermittent ashfall was reported in San Pedro Yepocapa, Sangre de Cristo, Panimaché I and II, Morelia, Finca Palo Verde, El Porvenir (8 km ENE), Yucales (12 km SW), Santa Emilia, Santa Sofia, according to INSIVUMEH. VAAC advisories were published on eight days in June. Degassing persisted in the summit crater that rose 4.1-4.5 km altitude extending in different directions. Crater incandescence was observed occasionally, as well as incandescent pulses that rose 100-300 m above the crater. Block avalanches were observed descending the Seca, Taniluyá, Ceniza, Trinidad, Las Lajas, Santa Teresa, and Honda drainages, which could sometimes carry blocks up to 1 km in diameter.

On 2 June at 1050 a weak to moderate lahar was observed in the Las Lajas drainage on the SE flank. On 5 June, more lahars were detected in the Seca and Mineral drainages on the W flanks. A new lava flow was detected on 12 June, traveling 250 m down the Seca drainage on the NW flank, and accompanied by constant summit crater incandescence and gas emissions. The flow continued into 14 June, lengthening up to 300 m long. On 24 June weak and moderate explosions produced ash plumes that rose 4.3-4.7 km altitude drifting W and SW (figure 135). On 29 June at 1300 a weak lahar was reported in the Seca, Santa Teresa, and Mineral drainages on the W flank.

Figure (see Caption) Figure 135. Examples of small ash plumes at Fuego on 15 (left) and 24 (right) June 2020. Courtesy of William Chigna, CONRED.

Daily explosions and ash plumes continued through July 2020, with 1-15 explosions per hour and producing consistent ash plumes 4-4.9 km altitude drifting generally W for 10-24 km. These explosions resulted in block avalanches that descended the Trinidad, Taniluyá, Ceniza, Honda, Las Lajas, Seca, and Santa Teresa drainages. The number of white gas emissions decrease slightly compared to previous months and 4-4.4 km altitude. VAAC advisories were distributed on twenty different days in July. Incandescent ejecta was observed rising 100-350 m above the crater. Occasional ashfall was observed in Panimaché I and II, Morelia, Santa Sofía, Finca Palo Verde, Sangre de Cristo, San Pedro Yepocapa, and El Porvenir, according to INSIVUMEH.

On 4 July in the early morning, a lava flow began in the Seca drainage, which also produced some fine ash particles that drifted W. The lava flow continued into 5 July, measuring 150 m long. On the same day, weak to moderate lahars traveled only 20 m, carrying tree branches and blocks measuring 30 cm to 1 m. On 14, 24, and 29 July more lahars were generated in the Las Lajas drainages on the former date and both the Las Lajas and El Jute drainages on the two latter dates.

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/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); William Chigna, CONRED (URL: https://twitter.com/william_chigna).


Nishinoshima (Japan) — September 2020 Citation iconCite this Report

Nishinoshima

Japan

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

All times are local (unless otherwise noted)


Major June-July eruption of lava, ash, and sulfur dioxide; activity declines in August 2020

Japan’s Nishinoshima volcano, located about 1,000 km S of Tokyo in the Ogasawara Arc, erupted above sea level in November 2013 after 40 years of dormancy. Activity lasted through November 2015 and returned during mid-2017, continuing the growth of the island with ash plumes, ejecta, and lava flows. A short eruptive event in July 2018 produced a small lava flow and vent on the side of the pyroclastic cone. The next eruption of ash plumes, incandescent ejecta, and lava flows began in early December 2019, resulting in significant growth of the island. This report covers the ongoing activity from March-August 2020 when activity decreased. Information is provided primarily from Japan Meteorological Agency (JMA) monthly reports and the Japan Coast Guard (JCG), which makes regular overflights to make observations.

Renewed eruptive activity that began on 5 December 2019 continued during March-August 2020 but appeared to wane by the end of August. Major lava flows covered all sides of the island, with higher levels of activity during late June and early July. Ash emissions increased significantly during June and produced dense black ash plumes that rose up to 6 km altitude in early July. Explosive activity produced lightning and incandescent jets that rose 200 m and large bombs that fell to the base of the pyroclastic cone. Lava flow activity diminished at the end of July. Ash emissions decreased throughout August and appeared to cease after 27 August 2020. The MIROVA plot clearly reflects the high levels of thermal activity between December 2019 and August 2020 (figure 80); this event was reported by JMA as the largest eruption recorded to date. Sulfur dioxide emissions were very high during late June through early August, producing emissions that drifted across much of the western Pacific region.

Figure (see Caption) Figure 80. The MIROVA plot of thermal activity at Nishinoshima from 14 October 2019 through August 2020 indicates the high levels between early December 2019 and late July 2020 that resulted from the eruption of numerous lava flows on all flanks of the pyroclastic cone, significantly enlarging the island. Courtesy of MIROVA.

The Japan Coast Guard (JCG) conducted overflights of Nishinoshima on 9 and 15 March 2020 (figure 81). During both visits they observed eruptive activity from the summit crater, including ash emissions that rose to an altitude of approximately 1,000 m and lava flowing down the N and SE flanks (figure 82). Large ejecta was scattered around the base of the pyroclastic cone. The lava flowing north had reached the coast and was producing vigorous steam as it entered the water on 9 March; whitish gas emissions were visible on the N flank of the cone at the source of the lava flow (figure 83). On 9 March yellow-green discolored water was noted off the NE shore. The lava flow on the SE coast produced a small amount of steam at the ocean entry point and a strong signal in thermal imagery on 15 March (figure 84). Multiple daily MODVOLC thermal alerts were issued during 1-10, 17-24, and 27-30 March. Landsat-8 visual and thermal imagery on 30 March 2020 confirmed that thermal anomalies on the N and SE flanks of the volcano continued.

Figure (see Caption) Figure 81. The Japan Coast Guard conducted an overflight of Nishinoshima on 9 March 2020 and observed ash emissions rising 1,000 m above the summit and lava flowing into the ocean off the N flank of the island. Courtesy of Japan Coast Guard (JCG) and JMA.
Figure (see Caption) Figure 82. Lava flows at Nishinoshima during February and March 2020 were concentrated on the N and SE flanks. The areas in blue indicate topographical changes due to lava flows and pyroclastic deposits from the previous measurement. The growth of the SE-flank flow decreased during March while the N-flank flow rate increased significantly. Left image shows changes between 14 and 28 February and right image shows the differences between 28 February and 13 March. The correlated image analysis uses ALOS-2 / PALSAR-2 and is carried out with the cooperation of JAXA through the activities of the Satellite Analysis Group of the Volcano Eruption Prediction Liaison Committee. The software was developed by the Japan National Research Institute for Earth Science and Disaster Prevention and uses the technical data C1-No 478 of the Geospatial Information Authority of Japan. Courtesy of JAXA and JMA (Volcanic activity commentary material on Nishinoshima, March 2020).
Figure (see Caption) Figure 83. Vigorous steam emissions on the N flank of Nishinoshima on 9 March 2020 were caused by the active flow on the N flank. Whitish steam and gas midway up the flank indicated the outlet of the flow. Ash emissions rose from the summit crater and drifted E. Courtesy of Japan Coast Guard and JMA.
Figure (see Caption) Figure 84. Infrared imagery from 15 March 2020 at Nishinoshima showed the incandescent lava flow on the SE flank (foreground), blocks of ejecta scattered around the summit and flanks of the pyroclastic cone, and the active N-flank flow (left). Courtesy of Japan Coast Guard and JMA.

Ash emissions were not observed at Nishinoshima during JCG overflights on 6, 16, and 19 April 2020, but gas-and-steam emissions were noted from the summit crater, and a yellow discoloration interpreted by JMA to be sulfur precipitation was observed near the top of the pyroclastic cone. The summit crater was larger than during previous visits. Steam plumes seen each of those days on the N and NE coasts suggested active ocean entry of lava flows (figure 85). A lava flow was observed emerging from the E flank of the cone and entering the ocean on the E coast on 19 and 29 April (figure 86). During the overflight on 29 April observers noted lava flowing southward from a vent on the E flank of the pyroclastic cone. A narrow, brown, ash plume was visible on 29 April at the summit crater rising to an altitude of about 1,500 m. Thermal observations indicated continued flow activity throughout the month. Multiple daily MODVOLC thermal alerts were recorded during 2-6, 10-11, 17-23, and 28-30 April. Significant growth of the pyroclastic cone occurred between early February and late April 2020 (figure 87).

Figure (see Caption) Figure 85. Multiple entry points of lava flowed into the ocean producing jets of steam along the N flank of Nishinoshima on 6 April 2020. Courtesy of JCG and JMA.
Figure (see Caption) Figure 86. Lava flowed down the E flank of Nishinoshima from a vent below the summit on 19 April 2020. The ocean entry produced a vigorous steam plume (left). Courtesy of JCG.
Figure (see Caption) Figure 87. The pyroclastic cone at Nishinoshima grew significantly in size between 4 February (left), 9 March (middle), and 19 April 2020 (right). View is to the E. Courtesy of JMA and JCG.

Infrared satellite imagery from 17 May 2020 showed a strong thermal anomaly at the summit and hot spots on the NW flank indicative of flows. Visible imagery confirmed emissions at the summit and steam plumes on the NW flank (figure 88). Gray ash plumes rose to about 1,800 m altitude on 18 May during the only overflight of the month made by the Japan Coast Guard. In addition, white gas emissions rose from around the summit area and large blocks of ejecta were scattered around the base of the pyroclastic cone (figure 89). Steam from ocean-entry lava on the N flank was reduced from previous months, but a new flow moving NW into the ocean was generating a steam plume and a strong thermal signature. Multi-pixel thermal alerts were measured by the MODVOLC system on 1-3, 9-10, 13-15, 18, and 26-30 May. Sulfur dioxide emissions had been weak and intermittent from March through early May 2020 but became more persistent during the second half of May. Although modest in size, the plumes were detectible hundreds of kilometers away from the volcano (figure 90).

Figure (see Caption) Figure 88. Landsat-8 satellite imagery of Nishinoshima from 17 May 2020 confirmed continued eruptive activity. Visible imagery showed emissions at the summit and steam plumes on the NW flank (left) and infrared imagery showed a strong thermal anomaly at the summit and anomalies on the NW flank indicative of lava flows (right). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 89. Lava continued to enter the ocean at Nishinoshima during May 2020. A new lava flow on the NW flank produced a strong steam plume at an ocean entry (left) on 18 May 2020. In addition to a light gray plume of gas and ash, steaming blocks of ejecta were visible on the flanks of the pyroclastic cone. The strong thermal signature of the NW-flank flow in infrared imagery that same day showed multiple new lobes flowing to the ocean (right). Courtesy of JCG and JMA.
Figure (see Caption) Figure 90. Small but distinct SO2 emissions from Nishinoshima were recorded by the TROPOMI instrument on the Sentinel-5P satellite during the second half of May 2020. The plumes drifted tens to hundreds of kilometers away from the volcano in multiple directions as the wind directions changed. Nishinoshima is about 1,000 kilometers S of Tokyo. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity increased significantly during June 2020. Satellite imagery from 2 June revealed two intense thermal anomalies at the summit indicating a new crater, and lava flows active on the NW and NE flanks, all showing gas or steam emissions (figure 91). Dense brown and gray ash emissions were observed rising from the summit crater during JCG overflights on 7 and 15 June (figure 92). Plumes reached at least 1,500 m altitude, and ejecta reached the base of the pyroclastic cone. Between 5 and 19 June the lava flow on the WNW coast slowed significantly, while the flows to the N and E became significantly more active (figure 93). The Tokyo VAAC reported the first ash plume since mid-February on 12 June rose to 2.1 km and drifted NE. On 14 June they reported an ash plume extending E at 2.7 km altitude. Dense emissions continued to drift N and E at 2.1-2.7 km altitude until the last week of the month. The JCG overflight on 19 June observed darker ash emissions than two weeks earlier that drifted at least 180 km NE (figure 94) and incandescent tephra that exploded from the enlarged summit area where three overlapping craters trending E-W had formed.

Figure (see Caption) Figure 91. Landsat-8 satellite imagery on 2 June 2020 confirmed ongoing activity at Nishinoshima. Lava produced ocean-entry steam on the NE coast; a weak plume on the NW coast suggested reduced activity in that area (left). In addition, a dense steam plume drifted E from the summit, while a fainter plume adjacent to it also drifted E. The infrared image (right) indicated two intense anomalies at the summit, and weaker anomalies from lava flows on the NW and NE flanks. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 92. Lava flows at Nishinoshima entered the ocean on the N and NE coasts (left) on 7 June 2020, and dense, gray ash emissions rose to at least 1,500 m altitude. Courtesy of JCG.
Figure (see Caption) Figure 93. The lava flow on the WNW coast of Nishinoshima slowed significantly in early June 2020, while the flows to the N and E covered large areas of those flanks between 5 and 19 June. The areas in blue indicate topographical changes due to lava flows and pyroclastic deposits from the previous measurement. Left image shows the differences between 22 May and 5 June and right image shows changes between 5 and 19 June. The correlated image analysis uses ALOS-2 / PALSAR-2 and is carried out with the cooperation of JAXA through the activities of the Satellite Analysis Group of the Volcano Eruption Prediction Liaison Committee. The software was developed by the National Research Institute for Earth Science and Disaster Prevention and uses the technical data C1-No 478 of the Geospatial Information Authority of Japan. Courtesy of JAXA and JMA (Volcanic activity commentary material on Nishinoshima, June 2020).
Figure (see Caption) Figure 94. Ash emissions and explosive activity at Nishinoshima increased significantly during the second half of June. Dense black ash rose to 2.4 km altitude and drifted at least 180 km to the NE on 19 June 2020. Vigorous white steam plumes rose from the ocean on the E flank where a lava flow entered the ocean. Courtesy of JCG.

The Tokyo VAAC reported ash emissions that rose to 4.6 km altitude and drifted NE on 25 June. For the remainder of the month they rose to 2.7-3.9 km altitude and drifted N and NE. By the time of the JCG overflight on 29 June, the new crater that had opened on the SW flank had merged with the summit crater (figure 95). Dense black ash emissions rose to 3.4 km altitude and drifted NE, lava flowed down the SW flank into the ocean producing violent steam explosions, and incandescent tephra was scattered at least 200 m from the base of the pyroclastic cone from ongoing explosive activity (figure 96). Multiple layers of recent flow activity were visible along the SW coast (figure 97). Yellow-green discolored water encircled the entire island with a width of 1,000 m.

Figure (see Caption) Figure 95. The new crater on the SW flank of Nishinoshima had merged with the summit crater by 29 June 2020. Courtesy of JCG and JMA.
Figure (see Caption) Figure 96. Dense black ash emissions rose to 3.4 km altitude and drifted NE from the summit of Nishinoshima on 29 June 2020. Lava flowed down the SW flank into the ocean producing steam explosions, and incandescent tephra was scattered at least 200 m from the base of the pyroclastic cone from ongoing explosive activity at the summit (inset). Courtesy of JCG.
Figure (see Caption) Figure 97. Different textures of lava flows were visible along the SW flank of Nishinoshima on 29 June 2020. The active flow appeared dark brown and blocky, and produced steam explosions at the ocean entry site (right). Slightly older, brownish-red lava (center) still produced steam along the coastline. Courtesy of JCG.

MODVOLC thermal alerts reached their highest levels of the period during June 2020 with multi-pixel alerts recorded on most days of the month. Sulfur dioxide emissions increased steadily throughout June to the highest levels recorded for Nishinoshima; by the end of the month plumes of SO2 were drifting thousands of kilometers across the Pacific Ocean and being captured in complex atmospheric circulation currents (figure 98).

Figure (see Caption) Figure 98. Sulfur dioxide emissions at Nishinoshima increased noticeably during the second half of June 2020 as measured by the TROPOMI instrument on the Sentinel-5P satellite. Atmospheric circulation currents produced long-lived plumes that drifted thousands of kilometers from the volcano. Nishinoshima is 1,000 km S of Tokyo. Courtesy of NASA Sulfur Dioxide Monitoring Page.

By early July 2020, satellite data indicated that the NE quadrant of the island was covered with ash, and a large amount of new lava had flowed down the SW flank, creating fans extending into the ocean (figure 99). The Tokyo VAAC reported ash emissions that rose to 3.7-4.9 km altitude and drifted N during 1-6 July. The altitude increased to 6.1 km during 8 and 9 July, and ranged from 4.6-6.1 km during 10-14 July while the drift direction changed to NE. The marine meteorological observation ship "Ryofu Maru" reported on 11 July that dense black ash was continuously erupting from the summit crater and drifting W at 1,700 m altitude or higher. They observed large volcanic blocks scattered around the base of the pyroclastic cone, and ash falling from the drifting plume. During the night of 11 July incandescent lava and volcanic lightning rose to about 200 m above the crater rim (figure 100).

Figure (see Caption) Figure 99. By early July 2020, satellite data from Nishinoshima indicated that the NE quadrant of the island was covered with ash, and a large amount of new lava had flowed down the SW flank creating fans extending into the ocean. The areas in blue indicate topographical changes due to lava flows and pyroclastic deposits from the previous measurement. Left image shows differences between 5 and 19 June and the right image shows changes between 19 June and 3 July that included abundant ashfall on the NE flank. The correlated image analysis uses ALOS-2 / PALSAR-2 and is carried out with the cooperation of JAXA through the activities of the Satellite Analysis Group of the Volcano Eruption Prediction Liaison Committee. The software was developed by the National Research Institute for Earth Science and Disaster Prevention and uses the technical data C1-No 478 of the Geospatial Information Authority of Japan. Courtesy of JAXA and JMA (Volcanic activity commentary material on Nishinoshima, June 2020).
Figure (see Caption) Figure 100. High levels of activity were observed at Nishinoshima by crew members aboard the marine meteorological observation ship "Ryofu Maru” on 11 July 2020. Abundant ash emissions filled the sky and tephra fell out of the ash cloud for several kilometers downwind (left, seen from 6 km NE). Incandescent explosions rose as much as 200 m into the night sky (right, seen from 4 km E). Courtesy of JMA.

During 16-26 July 2020 the Tokyo VAAC reported ash emissions at 3.7-5.2 km altitude that drifted primarily N and NE. The vessel "Keifu Maru" passed Nishinoshima on 20 July and crewmembers observed continuing emissions from the summit of dense, black ash. JCG observed an ash plume rising to at least 2.7 km altitude during their overflight of 20 July. A large dome of fresh lava was visible on the SW flank of the island (figure 101). Lower ash emissions from 2.4-3.7 km altitude were reported by the Tokyo VAAC during 27-29 July, but the altitude increased to 5.5-5.8 km during the last two days of the month. During an overflight on 30 July by the National Research Institute for Earth Science and Disaster Prevention, dark and light gray ash emissions rose to 3.0 km altitude, but no flowing lava or large bombs were observed. They also noted thick deposits of brownish-gray ash on the N side of the island (figure 102).

Figure (see Caption) Figure 101. JCG observed an ash plume at Nishinoshima rising to at least 2.7 km altitude during their overflight of 20 July 2020. A large dome of fresh lava was visible on the SW flank of the island. Courtesy of JCG.
Figure (see Caption) Figure 102. Ash emissions changed from dark to light gray on 30 July 2020 at Nishinoshima as seen during an overflight by the National Research Institute for Earth Science and Disaster Prevention. Thick brownish-gray ash was deposited over the lava on the N side of the island. Courtesy of JMA (Information on volcanic activity in Nishinoshima, July 2020).

JMA reported a sharp decrease in the lava eruption rate during July with thermal anomalies decreasing significantly mid-month. Multiple daily MODVOLC thermal alerts were recorded during the first half of the month but were reduced to two or three per day during the last third of July. Throughout July, SO2 emissions were the highest recorded in modern times for Nishinoshima. High levels of emissions were measured daily, producing streams with high concentrations of SO2 that were caught up in rotating wind currents and drifted thousands of kilometers across the Pacific Ocean (figure 103).

Figure (see Caption) Figure 103. Complex atmospheric wind patterns carried the largest SO2 plumes recorded from Nishinoshima thousands of kilometers around the western Pacific Ocean during July 2020. Nishinoshima is about 1,000 km S of Tokyo. Top and bottom left images both show 6 July but at different scales. Courtesy of NASA Sulfur Dioxide Monitoring Page.

Thermal activity was greatly reduced during August 2020. Only one or two MODVOLC alerts were issued on 11, 18, 20, 21, 29, and 30 August, and no fresh lava flows were observed. The Tokyo VAAC reported ash emissions daily from 1-20 August. Plume heights were 4.9-5.8 km altitude during 1-4 August after which they dropped to 3.9 km altitude through 15 August. A brief pulse to 4.6 km altitude was recorded on 16 August, but then they dropped to 3.0 km or lower through the end of the month and became intermittent. The last ash emission was reported at 2.7 km altitude drifting W on 27 August.

No eruptive activity was observed during the Japan Coast Guard overflights on 19 and 23 August. High temperatures were measured on the inner wall of the summit crater on 19 August (figure 104). Steam plumes rose from the summit crater to about 2.5 km altitude during both visits (figure 105). Yellow-green discolored water was present on 23 August around the NW and SW coasts. No lava flows were observed, and infrared cameras did not measure any surface thermal anomalies outside of the crater. Very high levels of SO2 emissions were measured through 12 August when they began to noticeably decrease (figure 106). By the end of the month, only small amounts of SO2 were measured in satellite data.

Figure (see Caption) Figure 104. A strong thermal anomaly was still present inside the newly enlarged summit crater at Nishinoshima on 19 August 2020. Courtesy of JCG.
Figure (see Caption) Figure 105. Only steam plumes were observed rising from the summit crater of Nishinoshima during the 23 August 2020 overflight by the Japan Coast Guard. Courtesy of JCG.
Figure (see Caption) Figure 106. Sulfur dioxide emissions remained very high at Nishinoshima until 12 August 2020 when they declined sharply. Circulating air currents carried SO2 thousands of kilometers around the western Pacific region. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

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

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Japan Coast Guard (JCG), Hydrographic and Oceanographic Department, 3-1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8932, Japan (URL: https://www1.kaiho.mlit.go.jp/GIJUTSUKOKUSAI/kaiikiDB/kaiyo18-e1.htm); 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/); 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/); Japan Aerospace Exploration Agency-Earth Observation Research Center (JAXA-EORC), 7-44-1 Jindaiji Higashi-machi, Chofu-shi, Tokyo 182-8522, Japan (URL: http://www.eorc.jaxa.jp/); 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/).


Turrialba (Costa Rica) — September 2020 Citation iconCite this Report

Turrialba

Costa Rica

10.025°N, 83.767°W; summit elev. 3340 m

All times are local (unless otherwise noted)


New eruptive period on 18 June 2020 consisted of ash eruptions

Turrialba is a stratovolcano located in Costa Rica that overlooks the city of Cartago. Three well-defined craters occur at the upper SW end of a broad 800 x 2,200 m summit depression that is breached to the NE. Activity described in the previous report primarily included weak ash explosions and minor ash emissions (BGVN 44:11). This reporting period updates information from November 2019-August 2020; volcanism dominantly consists of ash emissions during June-August, based on information from daily and weekly reports by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA) and satellite data.

Volcanism during November 2019 through mid-June was relatively low, dominated by low SO2 emissions (100-300 tons/day) and typical low seismic tremors. A single explosion was recorded at 1850 on 7 December 2019, and two gas-and-steam plumes rose 800 m and 300 m above the crater on 25 and 27 December, respectively. An explosion was detected on 29 January 2020 but did not result in any ejecta. An overflight during the week of 10 February measured the depth of the crater (140 m); since the previous measurements made in February 2019 (220 m), the crater has filled with 80 m of debris due to frequent collapses of the NW and SE internal crater walls. Beginning around February and into at least early May 2020 the Sentinel-2 MODIS Thermal Volcanic Activity graph provided by the MIROVA system detected a small cluster of thermal anomalies (figure 52). Some of these anomalies were faintly registered in Sentinel-2 thermal satellite imagery during 10 and 25 April, with a more distinct anomaly occurring on 15 May (figure 53).

Figure (see Caption) Figure 52. A small cluster of thermal anomalies were detected in the summit area of Turrialba (red dots) during February-May 2020 as recorded by the Sentinel-2 MODIS Thermal Volcanic Activity data (bands 12, 11, 8A). Courtesy of MIROVA.
Figure (see Caption) Figure 53. Sentinel-2 thermal satellite imagery detected minor gas-and-steam emissions (left) and a weak thermal anomaly (right) in the summit crater at Turrialba on 11 January and 15 May 2020, respectively. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

On 18 June activity increased, which marked the start of a new eruptive period that produced ash emissions rising 100 m above the crater rim at 1714, 1723, and 1818. The next morning, 19 June, two more events at 1023 and 1039 resulted in ash emissions rising 100 m above the crater. During 23-26 June small ash emissions continued to occur each day, rising no higher than 100 m above the crater. A series of small ash eruptions that rose 100 m above the crater occurred during 28 and 29 June; four events were recorded at 0821, 1348, 1739, and 2303 on 28 June and five more were recorded at 0107, 0232, 0306, 0412, and 0818 on 29 June. The two events at 0107 and 0412 were accompanied by ballistics ejected onto the N wall of the crater, according to OVSICORI-UNA.

Almost daily ash emissions continued during 1-7 July, rising less than 100 m above the crater; no ash emissions were observed on 3 July. On 6 July, gas-and-steam and ash emissions rose hundreds of meters above the crater at 0900, resulting in local ashfall. Passive gas-and-steam emissions with minor amounts of ash were occasionally visible during 9-10 July. On 14 July an eruptive pulse was observed, generating brief incandescence at 2328, which was likely associated with a small ash emission. Dilute ash emissions at 1028 on 16 July preceded an eruption at 1209 that resulted in an ash plume rising 200 m above the crater. Ash emissions of variable densities continued through 20 July rising as high as 200 m above the crater; on 20 July incandescence was observed on the W wall of the crater. An eruptive event at 0946 on 29 July produced an ash plume that rose 200-300 m above the crater rim. During 30-31 July a series of at least ten ash eruptions were detected, rising no higher than 200 m above the crater, each lasting less than ten minutes. Some incandescence was visible on the SW wall of the crater during this time.

On 1 August at 0746 an ash plume rose 500 m above the crater. During 4-5 August a total of 19 minor ash emissions occurred, accompanied by ash plumes that rose no higher than 200 m above the crater. OVSICORI-UNA reported on 21 August that the SW wall of the crater had fractured; some incandescence in the fracture zone had been observed the previous month. Two final eruptions were detected on 22 and 24 August at 1253 and 2023, respectively. The eruption on 24 August resulted in an ash plume that rose to a maximum height of 1 km above the crater.

Geologic Background. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

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/); 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).


Etna (Italy) — September 2020 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Effusive activity in early April; frequent Strombolian explosions and ash emissions during April-July 2020

Etna, located on the island of Sicily, Italy, is a stratovolcano that has had historical eruptions dating back 3,500 years. Its most recent eruptive period began in September 2013 and has continued through July 2020, characterized by Strombolian explosions, lava flows, and ash plumes. Activity has commonly originated from the summit areas, including the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). The newest crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC. Volcanism during this reporting period from April through July 2020 includes frequent Strombolian explosions primarily in the Voragine and NSEC craters, ash emissions, some lava effusions, and gas-and-steam emissions. Information primarily comes from weekly reports by the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Summary of activity during April-July 2020. Degassing of variable intensity is typical activity from all summit vents at Etna during the reporting period. Intra-crater Strombolian explosions and ash emissions that rose to a maximum altitude of 5 km on 19 April primarily originated from the Voragine (VOR) and New Southeast Crater (NSEC) craters. At night, summit crater incandescence was occasionally visible in conjunction with explosions and degassing. During 18-19 April small lava flows were observed in the VOR and NSEC craters that descended toward the BN from the VOR Crater and the upper E and S flanks of the NSEC. On 19 April a significant eruptive event began with Strombolian explosions that gradually evolved into lava fountaining activity, ejecting hot material and spatter from the NSEC. Ash plumes that were produced during this event resulted in ashfall to the E of Etna. The flows had stopped by the end of April; activity during May consisted of Strombolian explosions in both the VOR and NSEC craters and intermittent ash plumes rising 4.5 km altitude. On 22 May Strombolian explosions in the NSEC produced multiple ash plumes, which resulted in ashfall to the S. INGV reported that the pit crater at the bottom of BN had widened and was accompanied by degassing. Explosions with intermittent ash emissions continued during June and July and were primarily focused in the VOR and NSEC craters; mild Strombolian activity in the SEC was reported in mid-July.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows multiple episodes of thermal activity throughout the reporting period (figure 296). In early April, the frequency and power of the thermal anomalies began to decrease through mid-June; in July, they had increased in power again but remained less frequent compared to activity in January through March. According to the MODVOLC thermal algorithm, a total of seven alerts were detected in the summit craters during 10 April (1), 17 April (1), 24 April (2), 10 July (1), 13 July (1), and 29 July (1) 2020. These thermal hotspots were typically registered during or after a Strombolian event. Frequent Strombolian activity contributed to distinct SO2 plumes that drifted in different directions (figure 297).

Figure (see Caption) Figure 296. Multiple episodes of varying thermal activity at Etna from 14 October 2019 through July 2020 were reflected in the MIROVA data (Log Radiative Power). In early April, the frequency and power of the thermal anomalies decreased through mid-June. In July, the thermal anomalies increased in power, but did not increase in frequency. Courtesy of MIROVA.
Figure (see Caption) Figure 297. Distinct SO2 plumes from Etna were detected on multiple days during April to July 2020 due to frequent Strombolian explosions, including, 24 April (top left), 9 May (top right), 25 June (bottom left), and 21 July (bottom right) 2020. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Activity during April-May 2020. During April, INGV reported Strombolian explosions that produced some ash emissions and intra-crater effusive activity within the Voragine Crater (VOR) and abundant degassing from the New Southeast Crater (NSEC), Northeast Crater (NEC), and from two vents on the cono della sella (saddle cone) that were sometimes accompanied by a modest amount of ash (figure 298). At night, summit crater incandescence was observed in the cono della salla. The Strombolian activity in the VOR built intra-crater scoria cones while lava flows traveled down the S flank of the largest, main cone. On 18 April effusive activity from the main cone in the VOR Crater traveled 30 m toward the Bocca Nuova (BN) Crater; the pit crater at the bottom of the BN crater had widened compared to previous observations. A brief episode of Strombolian explosions that started around 0830 on 19 April in the NSEC gradually evolved into modest lava fountaining activity by 0915, rising to 3 km altitude and ejecting bombs up to 100 m (figure 299). A large spatter deposit was found 50 m from the vent and 3-4 small lava flows were descending the NSEC crater rim; two of these summit lava flows were observed at 1006, confined to the upper E and S flanks of the cone. Around 1030, one or two vents in the cono della sella produced a gas-and-steam and ash plume that rose 5 km altitude and drifted E, resulting in ashfall on the E flank of Etna in the Valle del Bove, as well as between the towns of Zafferana Etnea (10 km SE) and Linguaglossa (17 km NE). At night, flashes of incandescence were visible at the summit. By 1155, the lava fountaining had gradually slowed, stopping completely around 1300. The NEC continued to produce gas-and-steam emissions with some intra-crater explosive activity. During the week of 20-26 April, Strombolian activity in the VOR intra-crater scoria cone ejected pyroclastic material several hundred meters above the crater rim while the lava flows had significantly decreased, though continued to travel on the E flank of the main cone. Weak, intra-crater Strombolian activity with occasional ash emissions and nightly summit incandescence were observed in the NSEC (figure 300). By 30 April there were no longer any active lava flows; the entire flow field had begun cooling. The mass of the SO2 emissions varied in April from 5,000-15,000 tons per day.

Figure (see Caption) Figure 298. Photos of Strombolian explosions at Etna in the Voragine Crater (top left), strong degassing at the Northeast Crater (NEC) (top right), and incandescent flashes and Strombolian activity in the New Southeast Crater (NSEC) seen from Tremestieri Etneo (bottom row) on 10 April 2020. Photos by Francesco Ciancitto (top row) and Boris Behncke (bottom row), courtesy of INGV.
Figure (see Caption) Figure 299. Strombolian activity at Etna’s “cono della sella” of the NSEC crater on 19 April 2020 included (a-b) lava fountaining that rose 3 km altitude, ejecting bomb-sized material and a spatter deposit captured by the Montagnola (EMOV) thermal camera. (c-d) An eruptive column and increased white gas-and-steam and ash emissions were captured by the Montagnola (EMOV) visible camera and (e-f) were also seen from Tremestieri Etneo captured by Boris Behncke. Courtesy of INGV (Report 17/2020, ETNA, Bollettino Settimanale, 13/04/2020 – 19/04/2020, data emissione 21/04/2020).
Figure (see Caption) Figure 300. Webcam images showing intra-crater explosive activity at Etna in the Voragine (VOR) and New Southeast Crater (NSEC) on 24 April 2020 captured by the (a-b) Montagnola and (c) Monte Cagliato cameras. At night, summit incandescence was visible and accompanied by strong degassing. Courtesy of INGV (Report 18/2020, ETNA, Bollettino Settimanale, 20/04/2020 – 26/04/2020, data emissione 28/04/2020).

Strombolian explosions produced periodic ash emissions and ejected mild, discontinuous incandescent material in the VOR Crater; the coarse material was deposited onto the S flank of BN (figure 301). Pulsating degassing continued from the summit craters, some of which were accompanied by incandescent flashes at night. The Strombolian activity in the cono della sella occasionally produced reddish ash during 3-4 May. During 5 and 8 May, there was an increase in ash emissions at the NSEC that drifted SSE. A strong explosive event in the VOR Crater located E of the main cone produced a significant amount of ash and ejected coarse material, which included blocks and bombs measuring 15-20 cm, that fell on the W edge of the crater, as well as on the S terrace of the BN Crater (figure 302).

Figure (see Caption) Figure 301. Photos of Strombolian explosions and summit incandescence at Etna on 4 May (left) and during the night of 11-12 May. Photos by Gianni Pennisi (left) and Boris Behncke (right, seen from Tremestieri Etneo). Courtesy of INGV.
Figure (see Caption) Figure 302. A photo on 5 May (left) and thermal image on 8 May (right) of Strombolian explosions at Etna in the Voragine Crater accompanied by a dense, gray ash plume. Photo by Daniele Andronico. Courtesy of INGV (Report 20/2020, ETNA, Bollettino Settimanale, 04/05/2020 – 10/05/2020, data emissione 12/05/2020).

On 10 May degassing continued in the NSEC while Strombolian activity fluctuated in both the VOR and NSEC Craters, ejecting ballistics beyond the crater rim; in the latter, some of the blocks fell back in, accumulated on the edge, and rolled down the slopes (figure 303). During the week of 11-17 May, eruptive activity at the VOR Crater was the lowest observed since early March; there were 4-5 weak, low intensity pulses not accompanied by bombs or ashfall in the VOR Crater. Degassing continued in the BN Crater. The crater of the cono della sella had widened further N following collapses due to the Strombolian activity, which exposed the internal wall.

Figure (see Caption) Figure 303. Map of the summit craters of Etna showing the active vents, the area of cooled lava flows (light green), and the location of the widening pit crater in the Bocca Nuova (BN) Crater (light blue circle) updated on 9 May 2020. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Black hatch marks indicate the crater rims: BN = Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. Courtesy of INGV (Report 29/2020, ETNA, Bollettino Settimanale, 06/07/2020 – 12/07/2020, data emissione 14/07/2020).

On 18 May an ash plume from the NSEC rose 4.5 km altitude and drifted NE. Strombolian explosions on 22 May at the NSEC produced multiple ash plumes that rose 4.5 km altitude and drifted S and SW (figure 304), depositing a thin layer of ash on the S slope, and resulting in ashfall in Catania (27 km S). Explosions from the VOR Crater had ejected a deposit of large clasts (greater than 30 cm) on the NE flank, between the VOR Crater and NEC on 23 May. INGV reported that the pit crater in the BN continued to widen and degassing was observed in the NSEC, VOR Crater, and NEC. During the week of 25-31 May persistent visible flashes of incandescence at night were observed, which suggested there was intra-crater Strombolian activity in the SEC and NSEC. The mass of the SO2 plumes varied between 5,000-9,000 tons per day.

Figure (see Caption) Figure 304. Photo of repeated Strombolian activity and ash emissions rising from Etna above the New Southeast Crater (NSEC) on 22 May 2020 seen from Zafferana Etnea on the SE flank at 0955 local time. Photo by Boris Behncke, INGV.

Activity during June-July 2020. During June, moderate intra-crater Strombolian activity with intermittent ash emissions continued in the NSEC and occurred more sporadically in the VOR Crater; at night, incandescence of variable intensity was observed at the summit. During the week of 8-14 June, Strombolian explosions in the cono della sella generated some incandescence and rare jets of incandescent material above the crater rim, though no ash emissions were reported. On the morning of 14 June a sequence of ten small explosions in the VOR Crater ejected incandescent material just above the crater rim and produced small ash emissions. On 25 June an overflight showed the developing pit crater in the center of the BN, accompanied by degassing along the S edge of the wall; degassing continued from the NEC, VOR Crater, SEC, and NSEC (figure 305). The mass of the SO2 plumes measured 5,000-7,000 tons per day, according to INGV.

Figure (see Caption) Figure 305. Aerial photo of Etna from the NE during an overflight on 25 June 2020 by the Catania Coast Guard (2 Nucleo Aereo della Guardia Costiera di Catania) showing degassing of the summit craters. Photo captured from the Aw139 helicopter by Stefano Branca. Courtesy of INGV (Report 27/2020, ETNA, Bollettino Settimanale, 22/06/2020 – 28/06/2020, data emissione 30/06/2020).

Similar modest, intra-crater Strombolian explosions in the NSEC, sporadic explosions in the VOR Crater, and degassing in the BN, VOR Crater, and NEC persisted into July. On 2 July degassing in the NEC was accompanied by weak intra-crater Strombolian activity. Intermittent weak ash emissions and ejecta from the NSEC and VOR Crater were observed during the month. During the week of 6-12 July INGV reported gas-and-steam emissions continued to rise from the vent in the pit crater at the bottom of BN (figure 306). On 11 July mild Strombolian activity, nighttime incandescence, and degassing was visible in the SEC (figure 307). By 15 July there was a modest increase in activity in the NSEC and VOR Craters, generating ash emissions and ejecting material over the crater rims while the other summit craters were dominantly characterized by degassing. On 31 July an explosion in the NSEC produced an ash plume that rose 4.5 km altitude.

Figure (see Caption) Figure 306. Photos of the bottom of the Bocca Nuova (BN) crater at Etna on 8 July 2020 showing the developing pit crater (left) and degassing. Minor ash emissions were visible in the background at the Voragine Crater (right). Both photos by Daniele Andronico. Courtesy of INGV (Report 29/2020, ETNA, Bollettino Settimanale, 06/07/2020 – 12/07/2020, data emissione 14/07/2020).
Figure (see Caption) Figure 307. Mild Strombolian activity and summit incandescence in the “cono della sella” (saddle vent) at the Southeast crater (SEC) of Etna on 11 July 2020, seen from Piano del Vescovo (left) and Piano Vetore (right). Photo by Boris Behncke, INGV.

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

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


Ol Doinyo Lengai (Tanzania) — September 2020 Citation iconCite this Report

Ol Doinyo Lengai

Tanzania

2.764°S, 35.914°E; summit elev. 2962 m

All times are local (unless otherwise noted)


Multiple lava flows within the summit crater; September 2019-August 2020

Ol Doinyo Lengai, located near the southern end of the East African Rift in Tanzania, is a stratovolcano known for its unique low-temperature carbonatitic lava. Frequent eruptions have been recorded since the late 19th century. Activity primarily occurs in the crater offset to the N about 100 m below the summit where hornitos (small cones) and pit craters produce lava flows and spattering. Lava began overflowing various flanks of the crater in 1993. The eruption transitioned to significant explosive activity in September 2007, which formed a new pyroclastic cone inside the crater. Repeated ash emissions reached altitudes greater than 10 km during March 2008. By mid-April 2008 explosive activity had decreased. In September new hornitos with small lava flows formed on the crater floor. The most recent eruptive period began in April 2017 and has been characterized by spattering confined to the crater, effusive activity in the summit crater, and multiple lava flows (BGVN 44:09). Effusive activity continued in the summit crater during this reporting period from September 2019 through August 2020, based on data and images from satellite information.

Throughout September 2019 to August 2020, evidence for repeated small lava flows was recorded in thermal data and satellite imagery. A total of seven low-level pulses of thermal activity were detected within 5 km from the summit in MIROVA data during September 2019 (1), February (2), March (2), and August (2) 2020 (figure 207). Sentinel-2 satellite imagery also provided evidence of multiple lava flows within the summit crater throughout the reporting period. On clear weather days, intermittent thermal anomalies were observed in thermal satellite imagery within the summit crater; new lava flows were detected due to the change in shape, volume, and location of the hotspot (figure 208). During a majority of the reporting period, the thermal anomaly dominantly appeared in the center of the crater, though occasionally it would also migrate to the SE wall, as seen on 3 February, the E wall on 12 July, or the NE wall on 31 August. In Natural Color rendering, fresh lava flows appear black within the crater that quickly cools to a white-brown color. These satellite images showed the migration of new lava flows between February, March, and June (figure 209). The flow on 8 February occurs in the center and along the W wall of the crater; the flow on 9 March is slightly thinner and is observed in the center and along the E wall of the crater; finally, the flow on 17 June is located in the center and along the N wall of the crater.

Figure (see Caption) Figure 207. Seven low-level pulses of thermal activity within 5 km of the summit of Ol Doinyo Lengai were recorded in the MIROVA thermal data between September 2019 to August 2020; one in early September 2019, two in February, two in March, and two in August 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 208. Sentinel-2 thermal satellite images of Ol Doinyo Lengai from November 2019 to August 2020 show intermittent thermal anomalies (bright yellow-orange) within the summit crater. The location of these anomalies occasionally changes, indicating new lava flows. Images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 209. Sentinel-2 satellite images of new lava flows within the summit crater at Ol Doinyo Lengai during 8 February (left), 9 March (middle), and 17 June (right) 2020. Lava flows appear black in the center of the crater that changes in volume and location from February to June. Images with “Natural Color” (bands 4, 3, 2) rendering; courtesy of Sentinel Hub Playground.

During August, multiple lava flows were detected in Sentinel-2 satellite imagery. On relatively clear days, lava flows were visible in the middle of the summit crater, occasionally branching out to one side of the crater (figure 210). On 6 August, a thin lava flow branched to the E flank, which became thicker by 11 August. On 16 and 21 August, the lava remained mostly in the center of the crater. A large pulse of fresh lava occurred on 31 August, extending to the NW and SE sides of the crater.

Figure (see Caption) Figure 210. Sentinel-2 images of multiple new lava flows at Ol Doinyo Lengai during August 2020. When visible in the first half of August, dark lava is concentrated in the center and E side of the crater; by the end of August the lava flows had reached the NW side of the crater. Images with “Natural Color” (bands 4, 3, 2) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. The symmetrical Ol Doinyo Lengai is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent stratovolcano, known to the Maasai as "The Mountain of God," rises abruptly above the broad plain south of Lake Natron in the Gregory Rift Valley. The cone-building stage ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatitic and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra ejections and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater and occasionally down the upper flanks. The depth and morphology of the northern crater have changed dramatically during the course of historical eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater. Long-term lava effusion in the summit crater beginning in 1983 had by the turn of the century mostly filled the northern crater; by late 1998 lava had begun overflowing the crater rim.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Yasur (Vanuatu) — September 2020 Citation iconCite this Report

Yasur

Vanuatu

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

All times are local (unless otherwise noted)


Ash and gas explosions continue through August 2020

Recent activity at Yasur, which has been erupting since July 1774, includes frequent Strombolian explosions, along with ash and gas plumes from several vents in the summit crater (BGVN 44:02, 45:03). This report summarizes activity during March through August 2020, using information from monthly bulletins of the Vanuatu Meteorology and Geo-Hazards Department (VMGD) and various satellite data. The volcano has remained on Alert Level 2 (major unrest state, on a scale of 0-5), where it has been since 18 October 2016, according to VMGD.

During the current reporting period, VMGD reported that explosive activity continued at an elevated level, with ongoing ash and gas emissions (figure 71). Some of the more intense explosions ejected bombs outside the summit crater. During 2-3, 13, and 17 March, 2-3 April, and 19 July, the Wellington Volcanic Ash Advisory Center (VAAC) identified low-level ash plumes that reached an altitude of 1.5 km and drifted in multiple directions; the ash plume during 2-3 April resulted in ashfall on the SSW part of the island. On 19 May an ash plume rose to a maximum altitude of 2.1 km and drifted SE.

Figure (see Caption) Figure 71. Webcam photos of ash emissions from Yasur on 18 March (left)and gas-and-steam emissions on 2 April (right) 2020. Courtesy of VMGD.

During the reporting period, the MODVOLC thermal algorithm using MODIS satellite data detected a total of 55 thermal hotspots during three days in April, nine days in May, six days in June and August, and four days in July. A maximum of four pixels were recorded on a single day during 26 May, 6 June, and 20 July. The MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data detected numerous hotspots from 16 September 2019 through August 2020, with a slight increase in power and frequency during May (figure 72). Satellite images from Sentinel-2 detected a strong thermal anomaly within the summit crater on 10 May, accompanied by ash and gas emissions (figure 73).

Figure (see Caption) Figure 72. Persistent low to moderate thermal activity at Yasur occurred from the summit area from 16 September 2019 through August 2020, as shown in this MIROVA graph (Log Radiative Power). Courtesy of MIROVA.
Figure (see Caption) Figure 73. Sentinel-2 images of Yasur on 10 May 2020 showing a strong thermal anomaly from the summit crater (left) and a gas emission that appears to contain some ash (right). The thermal anomaly in the S vent area was stronger than in the N vent, an observation also noted in March and April 2019 (BGVN 44:06). The volcano was usually obscured by clouds during March through August. The left image is in false color (bands 12, 11, 4) rendering, the right image is in natural color (bands 4, 3, 2) rendering; courtesy of Sentinel Hub Playground.

High-resolution satellite sensors commonly recorded moderate sulfur dioxide levels drifting in multiple directions from the volcano. High sulfur dioxide levels were also occasionally observed, especially during March (figure 74).

Figure (see Caption) Figure 74. High-density SO2 emissions streaming from Yasur during 8 (left) and 13 (middle) March and 21 April (right) 2020, were observed using the TROPOMI imaging spectrometer on the Sentinel-5P satellite. The plume drifted W on 8 March and E on both 13 March and 21 April. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

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

Information Contacts: Geo-Hazards Division, Vanuatu Meteorology and Geo-Hazards Department (VMGD), Ministry of Climate Change Adaptation, Meteorology, Geo-Hazards, Energy, Environment and Disaster Management, Private Mail Bag 9054, Lini Highway, Port Vila, Vanuatu (URL: http://www.vmgd.gov.vu/, https://www.facebook.com/VanuatuGeohazardsObservatory/); Wellington Volcanic Ash Advisory Centre (VAAC), Meteorological Service of New Zealand Ltd (MetService), PO Box 722, Wellington, New Zealand (URL: http://vaac.metservice.com/index.html); Hawai'i Institute of Geophysics and Planetology (HIGP) MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Villarrica (Chile) — September 2020 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Continued summit incandescence February-August 2020 with larger explosions in July and August

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

Intermittent incandescence was observed at the summit throughout February-August 2020, which was reflected in the MIROVA thermal anomaly data for the period (figure 92). Continuous steam and gas emissions with occasional ash plumes rose 100-520 m above the summit. Every clear satellite image of Villarrica from February -August 2020 showed either a strong thermal anomaly within the summit crater or a dense cloud within the crater that prevented the heat signal from being measured. Sentinel-2 captured on average twelve images of Villarrica each month (figure 93). Larger explosions on 25 July and 7 August produced ejecta and ash emissions.

Figure (see Caption) Figure 92. Thermal anomaly data for Villarrica from 13 October 2019 through August 2020 showed intermittent periods of activity. Incandescence was intermittently reported from the summit and satellite imagery showed a persistent hot spot inside the summit crater throughout the period. Courtesy of MIROVA.
Figure (see Caption) Figure 93. Examples of strong thermal anomalies inside the summit crater of Villarrica each month from March-August 2020 are shown with dates on the image. Sentinel-2 satellite imagery with Atmospheric penetration rendering (bands 12, 11, 8A) showed thermal anomalies at the summit in all clear satellite images during the period. Courtesy of Sentinel Hub Playground.

Primarily white gas emissions rose up to 400 m above the summit during the first half of February 2020 and to 320 m during the second half. Incandescence was observed on clear nights. Incandescent ejecta was captured in the POVI webcam on 7 February (figure 94). Sentinel-2 satellite imagery showed bright thermal anomalies at the summit on 5, 8, 10, 13, 18, 20, 23, 25, and 28 February, nine of the eleven days that images were taken; the other days were cloudy.

Figure (see Caption) Figure 94. Incandescent ejecta at the summit of Villarrica was captured in the POVI webcam late on 7 February 2020. Time sequence runs from top to bottom, then left to right. Courtesy of POVI.

Villarrica remained at Alert Level Yellow (on a four-level Green-Yellow-Orange-Red scale) in March 2020. Plumes of gas rose 350 m above the crater during the first half of March. The POVI webcam captured incandescent ejecta on 1 March (figure 95). SERNAGEOMIN reported continuous white emissions and incandescence at night when the weather permitted. During the second half of March emissions rose 300 m above the crater; they were mostly white but occasionally gray and drifted N, S, and SE. Nighttime incandescence could be observed from communities that were tens of kilometers away on multiple occasions (figure 96). Sentinel-2 satellite imagery showed bright thermal anomalies at the summit on 1, 3, 4, 6, 9, 11, 14, 16, 19, 26, 29, and 31 March, twelve of the fourteen days images were taken. The other days were cloudy.

Figure (see Caption) Figure 95. Incandescent ejecta rose from the summit of Villarrica in the early morning of 1 March 2020. Courtesy of POVI.
Figure (see Caption) Figure 96. Nighttime incandescence was observed on 24 March 2020 tens of kilometers away from Villarrica. Courtesy of Luis Orlando.

During the first half of April 2020 plumes of gas rose 300 m above the crater, mostly as continuous degassing of steam. Incandescence continued to be seen on clear nights throughout the month. Steam plumes rose 150 m high during the second half of the month. A series of Strombolian explosions on 28-29 April ejected material up to 30 m above the crater rim (figure 97). Sentinel-2 satellite imagery showed bright thermal anomalies at the summit on 3, 8, 10, 13, 20, and 30 April, six of the twelve days images were taken; other days were cloudy.

Figure (see Caption) Figure 97. A series of Strombolian explosions on 28-29 April 2020 at Villarrica ejected material up to 30 m above the crater rim. Courtesy of POVI.

Daily plumes of steam rose 160 m above the summit crater during the first half of May 2020; incandescence was visible on clear nights throughout the month. During 5-7 May webcams captured episodes of dark gray emissions with minor ash that, according to SERNAGEOMIN, was related to collapses of the interior crater walls. Plumes rose as high as 360 m above the crater during the second half of May. The continuous degassing was gray and white with periodic ash emissions. Pyroclastic deposits were noted in a radius of 50 m around the crater rim associated with minor explosive activity from the lava lake. The POVI infrared camera captured a strong thermal signal rising from the summit on 29 May (figure 98), although no visual incandescence was reported. Residents of Coñaripe (17 km SSW) could see steam plumes at the snow-covered summit on 31 May (figure 99). Sentinel-2 satellite imagery showed bright thermal anomalies at the summit on 5, 13, 20, 23, 25 and 30 May, six of the twelve days images were taken. The other days were cloudy.

Figure (see Caption) Figure 98. The POVI infrared camera captured a strong thermal signal rising from the summit of Villarrica on 29 May 2020; no visual incandescence was noted. Courtesy of POVI.
Figure (see Caption) Figure 99. Residents of Coñaripe (17 km SSW) could see steam plumes at the snow-covered summit of Villarrica on 31 May 2020. Courtesy of Laura Angarita.

For most of the first half of June, white steam emissions rose as high as 480 m above the crater rim. A few times, emissions were gray, attributed to ash emissions from collapses of the inner wall of the crater by SERNAGEOMIN. Incandescence was visible on clear nights throughout the month. Vertical inflation of 1.5 cm was noted during the first half of June. Skies were cloudy for much of the second half of June; webcams only captured images of the summit on 21 and 27 June with 100-m-high steam plumes. Sentinel-2 satellite imagery showed bright thermal anomalies at the summit on 4, 7, and 14 June, three of the twelve days images were taken. The other days were cloudy.

Atmospheric clouds prevented most observations of the summit during the first half of July (figure 100); during brief periods it was possible to detect incandescence and emissions rising to 320 m above the crater. Continuous degassing was observed during the second half of July; the highest plume rose to 360 m above the crater on 23 July. On 25 July, monitoring stations in the vicinity of Villarrica registered a large-period (LP) seismic event associated with a moderate explosion at the crater. It was accompanied by a 14.7 Pa infrasound signal measured 1 km away. Meteorological conditions did not permit views of any surface activity that day, but a clear view of the summit on 28 July showed dark tephra on the snow around the summit crater (figure 101). Sentinel-2 satellite imagery showed bright thermal anomalies at the summit on 2 and 29 July, two of the twelve days images were taken. The other days were either cloudy or had steam obscuring the summit crater.

Figure (see Caption) Figure 100. Although a multi-layer cap cloud formed over the summit of Villarrica on 15 July 2020, steam emissions could be seen close to the summit drifting down the slope. Cap clouds form when a stable airstream rises to pass over a peak and cools, condensing moisture into clouds. Photograph by Sebastián Campos, courtesy of Geography Fans.
Figure (see Caption) Figure 101. Dark tephra appeared near the summit of Villarrica on 28 July 2020; an explosion had been measured seismically on 25 July but clouds obscured visual observations. Image taken from Coñaripe, courtesy of Laura Angarita.

An explosion on 7 August at 1522 local time (1922 UTC) produced an LP seismic signal and a 10 Pa infrasound signal. Webcams were able to capture an image of the explosion which produced a dense plume of steam and ash that rose 370 m above the summit and drifted SE (figure 102). The highest plumes in the first half of August reached 520 m above the summit on 7 August. Sporadic emissions near the summit level were reported by the Buenos Aires VAAC the following day but were not observed in satellite imagery. When weather permitted during the second half of the month, continuous degassing to 200 m above the crater was visible on the webcams. SERNAGEOMIN participated in a webinar on 20 August 2020 discussing safety at Villarrica and showed an image of the summit crater taken during an overflight on 19 August (figure 103). Sentinel-2 satellite imagery showed bright thermal anomalies at the summit on 6, 21, and 31 August, three of the thirteen days images were taken. The other days were cloudy.

Figure (see Caption) Figure 102. An explosion at Villarrica on 7 August 2020 at 1522 local time (1922 UTC) produced an LP seismic signal and 10 Pa infrasound signal. Webcams were able to capture an image of the explosion which produced a dense plume of steam and ash that rose 370 m above the summit and drifted SE Courtesy of SERNAGEOMIN (Reporte Especial de Actividad Volcanica (REAV), Region De La Araucania y Los Rios, volcan Villarrica, 7 de Agosto de 2020, 16:15 Hora local).
Figure (see Caption) Figure 103. SERNAGEOMIN participated in a webinar on 20 August 2020 discussing safety at Villarrica and showed an image of the summit crater taken during an overflight on 19 August. Courtesy of Turismo Integral.

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

Information Contacts: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); 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); Proyecto Observación Villarrica Internet (POVI), (URL: http://www.povi.cl/, https://twitter.com/povi_cl/status/1237541250825248768); Luis Orlando (URL: https://twitter.com/valepizzas/status/1242657625495539712); Laura Angarita (URL: https://twitter.com/AngaritaV/status/1267275374947377152, https://twitter.com/AngaritaV/status/1288086614422573057); Geography Fans (URL: https://twitter.com/Geografia_Afic/status/1284520850499092480); Turismo Integral (URL: https://turismointegral.net/expertos-entregan-recomendaciones-por-actividad-registrada-en-volcan-villarrica/).


Stromboli (Italy) — September 2020 Citation iconCite this Report

Stromboli

Italy

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

All times are local (unless otherwise noted)


Strombolian activity continues at both summit craters during May-August 2020

Stromboli, located in northeastern-most part of the Aeolian Islands, is composed of two active summit vents: the Northern (N) Crater and the Central-South (CS) Crater that are situated at the head of the Sciara del Fuoco, a large scarp that runs from the summit down the NW side of the volcano. The current eruption period began in 1934, continuing to the present with volcanism characterized by consistent Strombolian explosions in both summit craters, ash plumes, pyroclastic flows, and occasional lava flows (BGVN 45:08). This report updates activity consisting of dominantly Strombolian explosions and ash plumes from May to August 2020 with information primarily from daily and weekly reports by Italy's Istituto Nazionale di Geofisica e Vulcanologia (INGV) and various satellite data.

Activity was consistent during this reporting period. Explosion rates ranged from 1-23 events per hour and were of variable intensity, producing material that typically rose from less than 80 to over 300 m above the crater. One ash plume on 19 July rose 1 km above the crater and high energy ballistics were ejected 500 m above the crater during the week of 20-26 July (table 9). Strombolian explosions were often accompanied by gas-and-steam emissions and spattering that has occasionally resulted in material deposited on the slopes of the Sciara del Fuoco. According to INGV, the average SO2 emissions measured 250-300 tons/day.

Table 9. Summary of activity at Stromboli during May-August 2020. Low-intensity activity indicates ejecta rising less than 80 m, medium-intensity is ejecta rising less than 150 m, and high-intensity is ejecta rising over 200 m above the vent. Data courtesy of INGV.

Month Activity
May 2020 Strombolian activity and degassing continued with some spattering. Explosion rates varied from 1-17 per hour. Ejected material rose 80-150 m above the N crater and 150-250 m above the CS crater. The average SO2 emissions measured 300 tons/day.
Jun 2020 Strombolian activity and degassing continued with spattering. Explosion rates varied from 2-14 per hour. Ejected material rose 80-200 m above the N crater and 150 m above the CS crater. Spattering was primarily focused in the CS crater. The average SO2 emissions measured 300 tons/day.
Jul 2020 Strombolian activity and degassing continued with some spattering. Explosion rates varied from 1-12 per hour. Ejected material rose 80-1,000 m above the N crater. Spattering was primarily focused in the CS crater. The average SO2 emissions measured 300 tons/day.
Aug 2020 Strombolian activity continued with discontinuous spattering. Explosion rates varied from 1-23 per hour. Ejected material rose at least 200 m above the N crater and at least 250 m above the CS crater.

Explosive activity was relatively consistent during May 2020 and was mainly produced in 3-4 eruptive vents in the N crater and at least two eruptive vents in the CS crater. As a result of some explosions fallout covered the slopes of the Sciara del Fuoco. Explosion rates varied from 1-17 per hour in the N crater and 1-8 per hour in the CS crater; ejected material rose 80-250 m above the craters.

During June, explosions originated from 2-3 eruptive vents in the N crater and at least 2-3 localized vents in the CS crater. The Strombolian explosions ejected material 80-200 m above the craters, some of which fell back onto the Sciara (figure 182). Explosion rates varied from 5-14 per hour in the N crater and 2-9 per hour in the CS crater. Spattering was typically observed in the CS crater.

Figure (see Caption) Figure 182. An explosion at Stromboli produced gas-and-steam and ash emissions on 18 June 2020 was observed in the CS crater in the Sciara del Fuoco. Courtesy of INGV (Rep. No. 26/2020, Stromboli, Bollettino Settimanale, 15/06/2020 - 21/06/2020, data emissione 23/06/2020).

Ongoing explosive activity continued into July, originating from 2-3 eruptive vents in the N crater and 3-4 eruptive vents in the CS crater. Explosions varied from 3-12 per hour in the N crater and 1-11 per hour in the CS crater; ejected lapilli and bombs rose 80-1,000 m above the craters (figure 183). On 19 July a high-energy explosion between 0500 and 0504 produced an ash plume containing ejecta more than 50 cm that rose to a maximum of 1 km above the crater, with fallout reaching the Pizzo sopra la Fossa and resulting in ashfall on the Sciara and the towns of Liscione and Roccette. During the week of 20-26 July explosions in the E portion of the volcano ejected ballistics 500 m above the crater; the size and shape of these varied between slag bombs to clasts greater than 50 cm.

Figure (see Caption) Figure 183. Webcam (left column) and thermal (right column) images of explosive activity at Stromboli on 29 July (top row) and 2 August (bottom row) 2020 originated from the N and CS craters, producing spatter and ash plumes. Courtesy of INGV (Rep. No. 32/2020, Stromboli, Bollettino Settimanale, 27/07/2020 - 02/08/2020, data emissione 04/08/2020).

Strombolian activity accompanied by discontinuous spattering continued during August. Total daily explosions varied from 3-23 per hour ejecting material that up to 200-250 m above the craters. During the first half of the month the explosions were low-intensity and consisted of fine material. On 13 August the intensity of the explosions increased, producing an ash plume that rose 300 m above the crater drifting SE and resulting in a significant amount of ashfall on the Sciara. During the week of 17-23, explosions in the N1 crater ejected material 200 m above the crater while explosions in the CS crater ejected material 250 m above the crater, predominantly during 22 August in the S2 crater (figure 184).

Figure (see Caption) Figure 184. Images of gas-and-steam and ash plumes rising from the N2 (left), S2 (middle), and CS craters (right) at Stromboli on 22 August 2020. Courtesy of INGV (Rep. No. 35/2020, Stromboli, Bollettino Settimanale, 17/08/2020 - 23/08/2020, data emissione 25/08/2020).

Moderate thermal activity was relatively consistent from October 2019 through mid-April 2020; during May-August thermal activity became less frequent and anomalies were lower in power based on the MIROVA Log Radiative Power graph using MODIS infrared satellite information (figure 185). Though there were no detected MODVOLC thermal alerts during this reporting period, many thermal hotspots were observed in Sentinel-2 thermal satellite imagery in both summit craters (figure 186).

Figure (see Caption) Figure 185. Low to moderate thermal activity at Stromboli occurred frequently from 16 September to mid-April 2020 as shown in the MIROVA graph (Log Radiative Power). During May-August thermal activity decreased and was less frequent compared to the previous months. Courtesy of MIROVA.
Figure (see Caption) Figure 186. Weak thermal anomalies (bright yellow-orange) at Stromboli were observed in thermal satellite imagery from both of the summit vents throughout May-August 2020. Images with atmospheric penetration (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

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

Information Contacts: Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy, (URL: http://www.ct.ingv.it/en/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Search Bulletin Archive by Publication Date

Select a month and year from the drop-downs and click "Show Issue" to have that issue displayed in this tab.

   

The default month and year is the latest issue available.

Bulletin of the Global Volcanism Network - Volume 42, Number 12 (December 2017)

Managing Editor: Edward Venzke

Bogoslof (United States)

Explosions in July and August 2017; new lava dome visible 20-22 August destroyed by explosions that end on 30 August

Cleveland (United States)

Dome growth and destruction multiple times during January-November 2017

Dempo (Indonesia)

Phreatic explosion from the crater lake generates a dense ash plume in November 2017

Pacaya (Guatemala)

Pyroclastic cone in MacKenney crater grows above crater rim, January-September 2017

Sabancaya (Peru)

Continuous pulses of ash emissions for ten months, February-November 2017

Santa Maria (Guatemala)

Slow growth of new lava dome, persistent ash plumes, and nearby ashfall, January-October 2017

Sinabung (Indonesia)

Constant activity through September 2017, with ash plumes, block avalanches, and pyroclastic flows

Tungurahua (Ecuador)

Nearly constant ash emissions and frequent lahars during July-December 2015

Ulawun (Papua New Guinea)

Intermittent ash plumes during June-November 2017

Villarrica (Chile)

Lava lake level fluctuates and Strombolian activity persists during October 2016-November 2017



Bogoslof (United States) — December 2017 Citation iconCite this Report

Bogoslof

United States

53.93°N, 168.03°W; summit elev. 150 m

All times are local (unless otherwise noted)


Explosions in July and August 2017; new lava dome visible 20-22 August destroyed by explosions that end on 30 August

Intermittent eruptions from Bogoslof, 40 km N of the main Aleutian arc (BGVN 42:09, figure 2), have created and destroyed several distinct islands at the summit of this submarine volcano. Previous eruptions in 1927 and 1992 created lava domes that were subsequently heavily eroded, before the most recent eruption began in December 2016 (figure 16). Numerous explosions with ash plumes significantly changed the morphology of the island between December 2016 and March 2017. Ash plumes rose to over 10 km altitude during May-July 2017 multiple times. A lava dome briefly emerged in early June before it was destroyed by subsequent explosions. This report continues with an account of activity between July and December 2017. Eruptive activity ended on 30 August. Information comes primarily from the Alaska Volcano Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC).

Figure (see Caption) Figure 16. Worldview satellite image of Bogoslof collected at 2313 UTC on 12 June 2017, two days after a lava dome that appeared in the lagoon was destroyed. The circular embayments were formed by a series of more than 40 explosions that began in mid-December 2016. These explosions greatly reshaped the island as material was removed and redeposited as air fall. Vigorous steaming was visible from a region S of the most active vent areas in the lagoon. Lava extrusion produced a circular dome that first rose above the water on 5 June and grew to a diameter of ~160 m before being destroyed by an explosion early in the day on 10 June. Courtesy of AVO.

New explosions during 2, 4, 8, and 9-10 July 2017 produced ash plumes that rose from 6.1 to 11 km altitude. Although significant ash clouds were produced, there were no reports of ashfall in nearby communities. After almost a month of quiet, an eruption on 7 August created new tephra deposits, and extended the N shore of the island. This eruption created a significant SO2 plume that was recorded by satellite instruments. Intermittent pulses of tremor were recorded during mid-August. A new lava dome grew between 20 and 22 August to 160 m in diameter before it was destroyed in a series of explosions during 26-30 August. Thermal anomalies were observed in satellite data several times during September, and they tapered off into early October. Steam emissions were still visible in early November when the last weak thermal anomaly was reported. By early December, significant erosion had begun to change the island's shape, and only minor steam emissions were visible in clear satellite images.

Beginning at 1248 local time (AKDT) on 2 July 2017, a significant explosive event was detected in seismic and infrasound data, and observed in satellite imagery. The event lasted about 16 minutes, and produced an ash plume that rose to 11 km altitude and drifted E, passing N of Dutch Harbor. No explosions were reported the following day, but two events were detected in seismic, infrasound, and satellite data on 4 July. The first, at 1651, lasted 13 minutes and produced an eruption cloud that rose to 8.5 km altitude and drifted SE; the second 11-minute-long eruption began at 1907, and produced a small cloud that rose to 9.8 km altitude and drifted SE.

On the morning of 8 July 2017, an eruption with a total duration of 19 minutes began at 1015 AKDT and produced a volcanic cloud reaching an altitude of 9.1 km that drifted N. Overnight during 9-10 July Bogoslof erupted several times; the first two explosions during the 3-hour-long eruption produced a small ash cloud that rose to 6.1 km altitude and drifted SE, dissipating rapidly. Later on 10 July, an 8-minute-long eruption began at 1000 AKDT and a 15-minute-long eruption began at 1706 AKDT; neither produced a significant plume. None of the eruptions on 8, 9, or 10 July caused ashfall in local communities. Weakly elevated surface temperatures were observed in clear satellite images on 12 and 16 July.

Following almost a month of quiet, Bogoslof erupted again on 7 August 2017. The eruption was detected in seismic, infrasound, satellite, and lightning data. The eruption began at 1000 AKDT and lasted for about three hours, producing an ash plume that rose to 9.7 km altitude according to AVO, and drifted S over Umnak Island, then out over the Pacific Ocean. The Anchorage VAAC initially reported the plume at 10.4 km altitude moving S. A later pilot report noted an altitude of 12.2 km. Satellite measurements of sulfur dioxide (SO2) in the eruption cloud indicated the second highest mass of SO2 erupted since the onset of activity in December 2016 (figure 17). Satellite images of the island taken on 8 August showed new tephra deposits had surrounded the vent area, forming a new crater lake, and extending the N shore of the island by 250 m (figure 18).

Figure (see Caption) Figure 17. Although the data is coarsely pixelated, it is clear that a substantial SO2 plume emerged from Bogoslof during the 7 August eruption, as recorded by the OMPS instrument on the Suomio NPP satellite. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 18. Worldview true-color satellite image of Bogoslof acquired on 8 August 2017, one day after a 3-hour-long explosive eruption. Ashfall deposits have expanded the island towards the N as the result of the eruption and formed an enclosed crater lake. At the time of this satellite overpass, the level of the crater lake was below sea level. Previous events such as these (that formed a shallow crater lake) formed a deep crater that was subsequently filled by an influx of ocean water. Vigorous steaming was apparent from the likely site of the initial explosive event in mid-December 2016. Sediment coming from erosion of the island is seen offshore surrounding most of the island. A comparison with figure 16, above, shows the extent of new material added on 7 August. Data provided under the Digital Globe NextView License. Courtesy of AVO.

Several short-duration seismic and infrasound signals were detected at the stations on nearby islands on 9 August 2017. Weakly elevated surface temperatures and a minor steam plume were observed in satellite images. Two short pulses of tremor were seen in seismic data on 14 August, one lasting five minutes and the other lasting three minutes. Seismicity returned to background levels following the pulses and remained quiet until a series of small earthquakes the next morning. Seismicity again returned to background levels by the following afternoon, 16 August, and remained quiet through the rest of that week. Photographs taken during an overflight on 15 August indicated that the vent region, which had dried out during the 7 August eruption, had refilled with water (figure 19).

Figure (see Caption) Figure 19. An overflight of Bogoslof on 15 August 2017 showed the increase in area of the crater lake after the eruption of 7 August (see figure 18). View is to the SE. Courtesy of AVO.

Unrest continued during mid-August 2017, and available data suggested that a lava dome had formed within the intra-island lake just W of the 1992 lava dome. The new dome was first observed on 18 August, and during 20-22 August grew to about 160 m in diameter. Two small explosions were detected in infrasound data at 0410 AKDT on 22 August. These explosions did not produce any volcanic plumes recognizable in satellite data. Elevated surface temperatures were observed on 24 August along with a steam plume extending S about 17 km from the island. Satellite images showed elevated surface temperatures and a robust steam plume the next day drifting 70 km SE. A photo from a nearby low-altitude airplane on 26 August, taken shortly before the next explosion, confirmed the intense steam plume (figure 20) likely caused by the interaction of the new dome with seawater. Two MODVOLC thermal alerts were issued on 25 August, the first two since January 2017, and the last two for the year.

Figure (see Caption) Figure 20. Bogoslof volcano with a vigorous steam plume likely caused by interaction of the new, hot lava dome with seawater. Photo by Dave Withrow (NOAA/Fisheries), taken at about 1300 AKDT on 26 August aboard a NOAA twin otter (N56RF) aircraft while surveying harbor seals west of Dutch Harbor. They were 13 nautical miles (24 km) from Bogoslof when photo was taken looking E with a 400 mm lens. Courtesy of AVO.

An explosive eruption at 1629 AKDT on 26 August 2017 lasted for about four minutes and produced a cloud that was observed in satellite images drifting SE over southern Unalaska Island. Cloud-top temperatures seen in satellite data indicated that it rose as high as 7.3 km altitude. The Anchorage VAAC reported the plume at 8.2 km altitude several hours later. The eruption was observed in seismic, infrasound, and satellite data, and one lightning stroke was detected. Elevated surface temperatures persisted, suggesting to AVO scientists that the lava dome was possibly still present within the crater lake. Three short-duration eruptive events occurred during 27-28 August. On 27 August at 1508 AKDT a brief explosive event lasting about two minutes produced a volcanic cloud that reached about 7.9 km altitude and drifted SE. Another explosive eruption occurred at 0323 AKDT on 28 August and lasted about 25 minutes. Satellite imagery showed only a very small eruption cloud drifting ESE that dissipated quickly. The third event occurred at 1117 AKDT that morning and produced a small ash cloud that likely reached 9 km altitude before dissipating over the North Pacific Ocean. Modeling of ash fallout from the cloud indicated trace to minor ash fall over the Southern Bering Sea in the area just S of the volcano.

Elevated surface temperatures were noted in satellite data on 29 August, along with a steam plume drifting SSE, suggesting to AVO the presence of lava at the surface. An explosive eruption began the next morning at 0405 AKDT and continued intermittently for almost two hours. It produced an ash cloud that reached to about 6 km altitude and drifted SSE, dissipating over the southern Bering Sea and North Pacific Ocean area. A vapor plume extended about 65 km SSE later that day.

AVO reported on 8 September 2017 that available data suggested that the most recent lava dome, first observed on 18 August, was removed by the explosive eruptions of 27-30 August. In addition, a narrow isthmus of new land extended across the crater, bisecting it and creating two lakes. Elevated surface temperatures were recorded in a satellite images on 11, 14, 17, 19, and 23 September. Discolored water was visible in satellite images on 17 September and may have represented outflow from the crater. Elevated surface temperatures continued to be observed in satellite data during periods of clear weather into the first two weeks of October, and again briefly at the beginning of November. Several areas of steam emissions were visible in satellite imagery on 9 October (figure 21).

Figure (see Caption) Figure 21. Worldview-3 satellite image of Bogoslof Island acquired on 9 October 2017. The areas that exhibited active steam emission are highlighted with yellow and black dashed lines. Image data acquired with the Digital Globe NextView License. Courtesy of AVO.

A clear, high-resolution satellite image taken on 2 November showed continued steaming of the ground on the S side of the smaller crater lake. Weakly elevated surface temperatures consistent with a hot crater lake were last observed in clear nighttime satellite images on 10 November 2017. Imagery from 20 November showed warm regions in the crater lagoon and at the site of the steaming that had persisted for several months (see figure 21). AVO scientists noted that this was consistent with a slowly cooling, post-eruptive system, and was likely responsible for the occasional observation of slightly elevated surface temperatures in satellite data. The MIROVA graph of thermal anomalies supported the slow cooling trend observed by AVO after the last explosions on 30 August 2017 (figure 22).

Figure (see Caption) Figure 22. The last series of explosive events recorded at Bogoslof during 26-30 August 2017 coincided with the last significant thermal anomalies on the MIROVA graph (infrared MODIS data) that covers the year ending on 19 January 2018. Gradual tapering of thermal anomalies is consistent with AVO satellite observations of a cooling trend during September through early November. Courtesy of MIROVA.

More than sixty explosive events occurred between 20 December 2016 and 30 August 2017. The most energetic of these sent water-rich, volcanic ash clouds to altitudes exceeding 10.7 km. The resulting dispersed volcanic clouds impacted local and international aviation operations over portions of the North Pacific and Alaska. Although most of the volcanic ash fell into the ocean, trace amounts were twice deposited on the community of Unalaska and the Port of Dutch Harbor. The 2016-17 eruption greatly changed the morphology of Bogoslof Island. At its greatest extent, the area of the island increased to about three times its pre-eruption size. Nearly all of the new material on the island is unconsolidated pyroclastic fall and flow (surge) deposits. The deposits are highly susceptible to wave erosion and additional changes in the configuration of the island are likely. A satellite image from 3 December 2017 shows significant erosion of the island with the vent lagoon opened to the ocean on the north shore of the island (figure 23).

Figure (see Caption) Figure 23. Worldview-3 satellite image of Bogoslof Island on 3 December 2017. Erosion of the island by waves had removed substantial material, and no new eruptive material had been added to the island since the end of August 2017. The approximate area of the island in this image was 1.3 square kilometers. Image data acquired with the Digital Globe NextView License. Courtesy of AVO.

Geologic Background. Bogoslof is the emergent summit of a submarine volcano that lies 40 km north of the main Aleutian arc. It rises 1500 m above the Bering Sea floor. Repeated construction and destruction of lava domes at different locations during historical time has greatly modified the appearance of this "Jack-in-the-Box" volcano and has introduced a confusing nomenclature applied during frequent visits of exploring expeditions. The present triangular-shaped, 0.75 x 2 km island consists of remnants of lava domes emplaced from 1796 to 1992. Castle Rock (Old Bogoslof) is a steep-sided pinnacle that is a remnant of a spine from the 1796 eruption. Fire Island (New Bogoslof), a small island located about 600 m NW of Bogoslof Island, is a remnant of a lava dome that was formed in 1883.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: http://www.avo.alaska.edu/ ), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.dggs.alaska.gov/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845(URL: http://vaac.arh.noaa.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/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Cleveland (United States) — December 2017 Citation iconCite this Report

Cleveland

United States

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

All times are local (unless otherwise noted)


Dome growth and destruction multiple times during January-November 2017

Dome growth and destruction accompanied by small ash explosions has been typical behavior at Alaska's Cleveland volcano in recent years (figures 20, 21, and 22). Located on Chuginadak Island in the Aleutians, slightly over 1,500 km SW of Anchorage, it has historical activity, including three large (VEI 3) eruptions, recorded back to 1893. The Alaska Volcano Observatory (AVO) and the Anchorage Volcanic Ash Advisory Center (VAAC) are responsible for monitoring activity and notifying air traffic of aviation hazards associated with Cleveland. This report provides a summary table of dome growth and destruction since 2013 (table 8), and details of continued activity from January through November 2017.

Figure (see Caption) Figure 20. A lava dome was growing at the summit of Cleveland on 4 August 2015. Concentric rings and radial fractures in the dome surface surrounded an elevated hot dome. Photo taken during the 2015 field season of the Islands of Four Mountains multidisciplinary project, work funded by the National Science Foundation, the USGS/AVO, and the Keck Geology Consortium. Courtesy of AVO.
Figure (see Caption) Figure 21. A 60-m-diameter lava dome was seen in this WorldView-1 satellite image from 25 May 2016 of Cleveland's summit crater. Image created by Rick Wessels, USGS. Image data copyright 2016 Digital Globe, NextView License. Courtesy of AVO.
Figure (see Caption) Figure 22. Thermal and photographic images of the lava dome that was growing in the summit crater of Cleveland on 26 July 2016. Top image is from a FLIR (Forward Looking InfraRed) camera, where warmer colors indicate hotter temperatures (scale is in Celsius); bottom image is a photograph of the summit crater, lava dome, and active fumaroles. AVO crew observed incandescence from the summit crater vent during this overflight. Courtesy of AVO.

Table 8. Observations of dome growth and other crater activity at Cleveland, 2013-2017. Data extracted from AVO reports.

Date Dome Observations
Jan-Feb 2013 New lava flow observed multiple times, 100 m across
4-6 May 2013 Explosions, ash cloud
 
Jun-Jul 2013 Elevated temperatures, satellite imagery
2-5 Oct 2013 Explosions
 
13 Nov 2013 Elevated surface temperatures near summit
25 Nov 2013 Explosion
 
28 Dec 2013 Strongly elevated surface temperature near summit
30 Dec 2013, 2 Jan 2014 Small ash cloud visible; explosion with ash plume
 
Jan-25 Feb 2014 Elevated surface temperatures near summit multiple times
25 Feb 2014 Two small explosions and ash clouds
 
7 Mar-4 Jun 2014 No detected activity
5 Jun 2014 Explosion
 
7 Jul 2014-Aug 2014 Intermittent weakly elevated surface temperatures at summit, vigorous steam plume, incandescence at summit during field visit
Late Aug-early Sep 2014 Elevated surface temperatures in satellite data
14, 24 Nov 2014 Vigorous steaming observed in webcam; Satellite image shows small lava dome in summit crater
5 Dec 2014-9 Jan 2015 Minor steaming and weakly elevated surface temperatures at summit
25, 28 Feb 2015 Weakly elevated surface temperatures at summit, low level steam plume observed
26 Mar 2015 Small steam plume, no further activity until 14 June
14 Jun 2015 Ash cover on upper flanks
 
17 Jun-21 Jul 2015 Elevated surface temperatures at summit
21 Jul 2015 Explosion
 
31 Jul, 4 Aug 2015 Strongly elevated surface temperatures at summit, photograph (figure 20) of lava dome in summit crater
6 Aug 2015 Small explosion
 
Aug-Oct 2015 Intermittent elevated surface temperatures at summit
29 Aug 2015 Seismic swarm
Sep-Nov 2015 No Reported Activity
Dec 2015 Elevated surface temperatures at summit
22-23 Dec 2015 Increased frequency of small VT events
 
Jan 2016 Elevated surface temperatures at summit
28 Feb 2016 Brief burst of small local earthquakes
 
Mar-1 April 2016 Elevated surface temperatures at summit
16 April 2016 Explosion
 
6 and 10 May 2016 Explosions
 
17-25 May 2016 Small lava dome observed (figure 21)
Jun-Jul 2016 Elevated surface temperatures at summit
26 Jul 2016 Lava dome observed (figure 22)
Aug-21 Oct 2016 Intermittent degassing, steam plumes, and elevated surface temperatures at summit
24, 28 Oct 2016 Explosion, ashfall observed
 
5 Nov 2016-23 Mar 2017 Elevated surface temperatures and intermittent steam emissions at summit. 3 Feb 2017 Satellite observation of lava dome
24 Mar 2017 Small explosion
 
Late Mar -15 May 2017 Elevated surface temperatures at summit crater; Dome observed 15 April
16 May 2017 Explosion
 
6-29 Jun 2017 Small, low-frequency earthquakes on 6 Jun, elevated surface temperatures at summit crater several times during June
4 Jul 2017 Explosion
 
7 Jul-21 Aug 2017 Elevated surface temperatures at summit crater; satellite (July 14-21) and photographic (July 25-26) observations of lava dome at summit (figure 23)
22 Aug 2017 Explosion
 
Late Aug-24 Sep 2017 Sporadic observations of elevated surface temperatures at summit crater
26, 28 Sep 2017 Explosions
 
28 Sep-Oct 2017 Elevated surface temperature at crater; lava effusion observed throughout October
28, 30 Oct 2017 Explosions
 
Early Nov 2017 Elevated surface temperatures at crater
14, 16 Nov 2017 Explosions

Lava dome extrusion may have been ongoing since early December 2016, when weakly elevated surface temperatures reappeared after the 24 October 2016 explosion. The lava dome was first observed in satellite imagery on 3 February 2017. Elevated surface temperatures were recorded throughout February and March 2017, and there was a small explosion on 24 March. Growth of a new dome was first observed on 15 April; it continued until being destroyed by an explosion on 16 May. Seismic data on 6 June and elevated temperatures on 7 June indicated growth of another dome, which continued until an explosion on 4 July 2017. There were multiple satellite and photographic observations of the growing dome during July and August; it was destroyed in an explosion on 22 August. Elevated surface temperatures were sporadically observed in early September. The next explosion took place on 26 September followed by two weaker ones on 28 September. Lava effusion was observed in satellite imagery throughout October. Small explosions on 28 and 30 October partly destroyed the lava dome. Elevated surface temperatures were recorded in early November along with small explosions on 14 and 16 November.

Activity during January-April 2017. While no activity was detected in infrasound or seismic data during January 2017, weakly elevated surface temperatures continued to be observed in infrequent clear satellite views (8 and 9 January), just as they were during 8-10 December and in infrared thermal data at the end of December (BGVN 42:04, figure 19). Low-level steam plumes were seen in clear views of the summit from the webcam during 15-19 and 21 January. Moderately elevated surface temperatures were observed in satellite data on 31 January 2017.

Satellite observations on 3 February 2017 confirmed the presence of a new lava dome at the bottom of the summit crater. The dome was about 70 m in diameter at that time, similar in size to previous domes. Observations in satellite imagery of weakly elevated surface temperatures at the summit continued during 7-9 February and during the last few days of the month. Minor steaming was seen in clear webcam images on 8 February. AVO noted that these observations were consistent with the presence of an active lava dome.

Minor steaming from the summit visible in clear webcam views, and slightly elevated surface temperatures in nighttime infrared satellite images, were present on several days during the first half of March. By the third week, surface temperatures were weakly to moderately elevated. At 0815 AKST (1615 UTC) on 24 March, a small explosion was detected in both seismic and infrasound (pressure sensor) data. This event was short-lived and similar to, if not smaller than, recent explosions. Cloud cover obscured observations by satellite. Slightly elevated surface temperatures were observed at the summit again during the last week of March.

No significant activity was detected in seismic, infrasound, or satellite data during the first two weeks of April 2017. A satellite image on 15 April, however, showed the presence of a small (less than 10-m-diameter) mound deep in the crater; the previous 75-m-diameter lava dome had been destroyed by the 24 March explosion. Satellite observations over the next several days indicated continued dome growth. Slightly elevated surface temperatures again appeared in a satellite view on 18 April. A satellite image on 23 April showed the dome partially filling the crater.

Activity during May-August 2017. Satellite images on 2 May showed that the lava dome was still active and had grown from about 15 m to more than 20 m in diameter. No further surface changes were evident on 8 May, indicating a pause or termination to the lava effusion. A short explosive eruption on 16 May at 1917 AKDT (17 May at 0317 UTC) was detected by local seismic instruments and lasted about 11 minutes. The resulting ash cloud rose to around 3.7-4.6 km altitude and was seen in satellite images to drift SW for about 5 hours. Satellite observations in the following days showed that the lava dome, built after the 24 March explosion, had been completely destroyed. Occasional clear webcam views showed steam emissions in the week following the 16 May explosion. Satellite imagery from 25 May suggested possible elevated surface temperatures at the summit while images from 26 May showed no change in the crater morphology since 16 May. No significant activity was detected in seismic or infrasound data for the remainder of May.

Evidence of possible lava effusion within the summit crater next appeared during the first week of June 2017. Small low-frequency earthquakes were detected on 6 June and elevated surface temperatures were observed in night-time satellite images on 7 June. Weakly elevated surface temperatures were observed in satellite images on 13, 19-23, and 29 June, and occasional clear webcam views of the summit showed light steaming. No activity was observed in seismic or infrasound data during the remainder of June.

A moderate explosive eruption lasting about ten minutes occurred early on the morning of 4 July at 0319 AKDT (1119 UTC). Elevated surface temperatures at the summit were visible after that on 7 and 14 July in satellite images, and occasional clear webcam views of the summit showed minor steaming. Satellite observations during 14-21 July revealed that a new dome, about 30 m in diameter and 10 m in height, had appeared at the bottom of the summit crater. Elevated surface temperatures were again observed on 22-24 July. New satellite observations between 21 and 28 July showed that the lava dome had reached about 42 m in diameter, with a slight inflation of its approximate height of 10 m. Minor steaming from the crater was seen in the webcam on 25 and 29-30 July; elevated surface temperatures were identified in satellite data on 30 July and 1 August. No activity was observed in seismic or infrasound data after the 4 July explosion for the remainder of the month.

Slow growth of the lava dome in the summit crater continued during the first few days of August 2017. Satellite observations showed that the dome surface area increased by about 75%, and covered an area of approximately 2,100 m2 (45 x 50 m) by 4 August. The height of the dome also increased due to intrusion of new lava. Elevated surface temperatures were observed in satellite data along with steam emissions from the summit crater seen in webcam images during periods of clear weather for the first few days of August, and again during 7-8 August. The small lava dome was observed during an overflight on 17 August (figure 23).

Figure (see Caption) Figure 23. A small lava dome grew inside the summit crater of Cleveland on 17 August 2017. Photo by Janet Schaefer, courtesy of AVO/ADGGS (Alaska Volcano Observatory/Alaska Division of Geological & Geophysical Surveys).

Minor degassing from the summit was seen in satellite and webcam images during 20-21 August. No explosive (ash-producing) activity was detected in seismic, infrasound, or webcam data in August until a 1-minute-long explosion on 22 August 2017 at 1043 AKDT (1843 UTC). Satellite data from 24 August indicated that the explosion destroyed the lava flow on the crater floor that had effused during July-August 2017. Explosion debris was evident on the crater floor, but no other changes to the summit area or flanks were noted. The 22 August explosion was detected by seismic and infrasound (air pressure) sensors, but no ash clouds were seen in satellite data. Nothing unusual was detected in seismic, infrasound, or satellite data for the remainder of August, except that elevated surface temperatures were observed sporadically in satellite data, suggesting that lava was present within the crater. A weak vapor plume was also sometimes visible at the summit in webcam images.

Activity during September-November 2017. Weakly elevated surface temperatures were observed in satellite data on 5 and 14 September 2017, along with minor steaming reported on 11, 17-19, and 22-24 September. These observations suggested to AVO the continued presence of lava in the crater. A small, short (three-minute-long) explosion was detected on local seismic and infrasound sensors at 1747 AKDT on 25 September (0147 on 26 September UTC) that produced a small volcanic cloud visible in satellite data about 30 minutes later with a height estimated at below 4.6 km altitude. Two weaker explosions were subsequently detected in infrasound and seismic data on 28 September (0516 and 0558 AKDT, 1319 and 1358 UTC), although no visible ash clouds were associated with these events. Weakly elevated surface temperatures during 28-30 September suggested that lava was present in the summit crater; a weak plume emanating from the crater could be seen when the summit was cloud-free.

Lava effusion in the crater was again noted in satellite data beginning on 30 September, forming a low dome that covered an area of about 4,200 m2 by 1 October 2017. Low-resolution satellite data from 6 October showed highly elevated surface temperatures, suggesting that slow growth of the dome continued. The dome doubled in size between 1 and 11 October when it appeared to cover an area of about 8,300 m2 and had approximate dimensions of 95 x 115 m. The number and intensity of elevated surface temperatures seen in satellite imagery declined during 7-13 October.

Satellite data from 15 October showed that the lava dome covered an area of about 9,500 m2 with dimensions of 100 x 125 m. There was no significant change in the size of the lava dome between 15 and 19 October based on satellite image analysis. On 16 October, satellite imagery revealed moderately elevated surface temperatures, and the webcam provided views of a small steam plume. Satellite data showed that the lava dome had grown further to about 110 x 140 m by 23 October and that surface temperatures were moderately elevated on 22 and 24 October. Small steam plumes were seen in webcam views during 22- 24 October. Small explosions on 28 and 30 October partly destroyed the dome within the summit crater. This was followed by slightly to moderately elevated surface temperatures occasionally observed in satellite imagery through the end of the month.

Moderately elevated surface temperatures were consistently observed in satellite imagery throughout the first half of November, suggesting new lava at or near the surface. Seismic and infrasound sensors detected a signal associated with low-level emissions shortly after midnight on 12 November. Two small explosions were also detected by the sensors on 14 and 16 November. These events were less energetic than those seen previously, and no volcanic cloud was observed following either explosion. A number of small earthquakes were detected on 14 November. Satellite observations of the summit indicated that a dome remained in the crater, and that the explosions were sourced from a vent in the middle of the dome. The satellite data showed no significant changes for the second half of November; although the volcano was obscured by cloud cover much of the time.

The infrared MIROVA thermal data for 2017 provided evidence that generally coincided with the satellite thermal observations of persistent heat production from dome growth throughout the year (figure 24).

Figure (see Caption) Figure 24. Infrared MODIS satellite data plotted with the MIROVA system shows intermittent thermal pulses from Cleveland for the year ending on 18 January 2018. Many of the spikes in thermal energy correspond to periods of satellite and photographic observation of dome growth. Courtesy of MIROVA.

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

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.dggs.alaska.gov/); Anchorage Volcanic Ash Advisory Center (VAAC), Alaska Aviation Weather Unit, NWS NOAA US Dept of Commerce, 6930 Sand Lake Road, Anchorage, AK 99502-1845 USA (URL: http://vaac.arh.noaa.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/).


Dempo (Indonesia) — December 2017 Citation iconCite this Report

Dempo

Indonesia

4.016°S, 103.121°E; summit elev. 3142 m

All times are local (unless otherwise noted)


Phreatic explosion from the crater lake generates a dense ash plume in November 2017

Activity at Dempo on Sumatra in recent years has consisted of brief phreatic eruptions, most recently single-day events on 25 September 2006 (BGVN 34:03) and 1 January 2009 (BGVN 34:01). There were no additional reports from the Center of Volcanology and Geological Hazard Mitigation (CVGHM), also known as Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), until a brief episode of unrest in late April 2015, Another typically short phreatic explosion took place on 9 November 2017.

Activity during 2015. On 29 April the Alert Level was raised to 2 (on a scale of 1-4) by PVMBG following observations of diffuse white-gray plumes on 27 April rising to 50 m above the crater. Seismicity had increased during April compared to the previous month (figure 5). A Detik news report on 30 April quoted the PVMBG Head of the Western Volcano Field of Observation and Investigation, Hendra Gunawan, as saying that there had been tremor recorded over the previous four days. No ashfall was reported by PVMBG, and a phreatic eruption was only mentioned in the 29 April notice as a potential danger.

Figure (see Caption) Figure 5. Seismicity recorded at Dempo from 1 January to 29 April 2015. The types of earthquakes reported are HBS (Hembusan, puff or emission events), Trm (tremor), VB (shallow volcanic type B), VA (volcanic type A), TL (local tectonic), and TJ (distant tectonic). Courtesy of PVMBG.

Observers reported that during 1 June-9 September 2015 no plumes were seen and seismicity was low. On 10 September PVMBG lowered the Alert Level to 1.

Activity during 2017. Staff at the PVMBG Dempo observation post reported that no plumes rose from the crater during January and February 2017, but some diffuse white plumes during 1 March-4 April rose no higher than 50 m. Seismicity increased significantly above background levels from 21 March to 4 April (figure 5). On 5 April PVMBG raised the Alert Level to 2 based on visual and seismic data, but did not report any phreatic eruptions.

Figure (see Caption) Figure 6. Seismicity recorded at Dempo from 31 December 2016 to 6 April 2017. The types of earthquakes reported are HBS (Hembusan, puff or emission events), TRE (tremor), VB (shallow volcanic type B), VA (volcanic type A), TL (local tectonic), and TJ (distant tectonic). Courtesy of PVMBG.

According to PVMBG a three-minute-long phreatic eruption began at 1651 on 9 November 2017 and generated a dense ash plume that rose to 4.2 km altitude, about 1 km above the crater rim, and drifted S. Ashfall and sulfur gases were reported in villages on the S flanks, but there was no damage to property or injuries. The Alert Level remained at 2, with a 3-km-diameter exclusion zone; the Aviation Color Code was at Yellow.

Geologic Background. Dempo is a prominent stratovolcano that rises above the Pasumah Plain of SE Sumatra. The andesitic volcanic complex has two main peaks, Gunung Dempo and Gunung Marapi, constructed near the SE rim of a 3 x 5 km caldera breached to the north. The Dempo peak is slightly lower, and lies at the SE end of the summit complex. The taller Marapi cone was constructed within a crater cutting the older Gunung Dempo edifice. Remnants of seven craters are found at or near the summit, with volcanism migrating WNW over time. The large, 800 x 1100 m wide historically active crater cuts the NW side of the Marapi cone and contains a 400-m-wide lake located at the far NW end of the crater complex. Historical eruptions have been restricted to small-to-moderate explosive activity that produced ashfall near the volcano.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Detiknews (URL: https://news.detik.com/).


Pacaya (Guatemala) — December 2017 Citation iconCite this Report

Pacaya

Guatemala

14.382°N, 90.601°W; summit elev. 2569 m

All times are local (unless otherwise noted)


Pyroclastic cone in MacKenney crater grows above crater rim, January-September 2017

Activity since 1961 at Pacaya has been characterized by extensive lava flows, bomb-laden Strombolian explosions, and ash plumes emerging from MacKenney crater and several vent fissures, impacting communities in the vicinity; several million people live within 50 km. After a few months of quiet, intermittent ash plumes and incandescence in early June 2015 marked the beginning of the latest eruptive episode, which has been ongoing since that time. Observations of incandescence increased during the second half of 2015, and the presence of a new pyroclastic cone, about 15 m in diameter at the center of MacKenney crater, was confirmed in mid-December 2015.

Strombolian activity from the cone continued throughout 2016. It was most active during June and July, depositing new ejecta onto the flanks. Although it had quieted down by the end of the year, persistent degassing, steam plumes, and occasional incandescence were still observed from the new cone. It had filled much of the crater by December 2016. This report describes the continued growth of the pyroclastic cone during January-September 2017, as well as new lava flows that emerged during February and March. Information was provided primarily by the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH) and satellite thermal data.

The pyroclastic cone inside MacKenney crater continued to grow sporadically during January-September 2017. Weak explosions in January produced ejecta 15 m above the top of the cone as steam and gas emissions rose about 400 m above the crater rim. By early February the top of the cone had risen to 10 m above the crater rim. Ejecta ranging in size from millimeters to 50 cm rose up to 25 m above the cone. Three small lava flows emerged from the crater in early February and flowed down the NW flank a few hundred meters before cooling. Growth of the cone continued more slowly during March-August, but incandescence was still observed, and weak explosions deposited tephra around the sides of the cone. Increased explosive activity during August reduced the height of the cone to slightly below the crater rim, but renewed explosions during September built it back up again to 10 m above the rim a few weeks later.

During January 2017, activity increased slightly compared with December 2016, and included degassing, tremors, incandescence, and weak explosions from MacKenney crater. Steam-and-gas plumes rose to around 400 m above the crater rim and generally drifted about 5 km before dissipating. Incandescence in the crater grew more visible towards the end of the month; ejecta from the pyroclastic cone within crater rose as much as 15 m above the crater rim. Seismic RSAM values also increased from a maximum of 2,500 to 3,500 units. The first MODVOLC thermal alert since 10 April 2016 appeared on 10 January 2017. Eight more alerts appeared during January, every few days for the rest of the month.

Degassing during February 2017 sent plumes slightly higher to 500 m above the crater . The top of the pyroclastic cone had risen to about 10 m above the crater rim by early February, as compared to about 10 m below the crater rim a year earlier in February 2016 (figure 78). Ejecta from the cone ranged in size from millimeters to 50 cm, and rose to heights of 10-25 m above the top of the cone with constant activity (figure 79).

Figure (see Caption) Figure 78. The pyroclastic cone inside MacKenney Crater at Pacaya grew substantially between February 2016 (upper photo) and 2 February 2017 (lower photo). View is to the NW with the 2010 fissure at the back, right side of the crater. Courtesy of INSIVUMEH (Reporte mensual, febrero 2017; Informe mensual de la actividad del Volcán Pacaya, junio 2017).
Figure (see Caption) Figure 79. Ejecta from the top of the pyroclastic cone inside MacKenney crater at Pacaya ranged in size from millimeters to approximately 50 cm, and was thrown tens of meters from the summit on 2 February 2017. Courtesy of INSIVUMEH (Reporte mensual, febrero 2017).

Three small lava flows were reported during February 2017, first emerging from the NW side of the crater from the fissure created during 2010 on 9 February 2017 and flowing NW towards Cerro Chino. Incandescent material was ejected 30-50 m above the crater rim and filled much of the crater. Lava travelled as far as 300 m down the NW flank. The dimensions of the flows were variable, but by the end of the month they were about 50 m long and 20 m wide. Ten MODVOLC thermal alerts were issued during February, indicating that activity was high inside and around the summit crater.

Steam plumes during March and April 2017 rose as high as 600 m above the crater rim. Lava flowed tens of meters outside the crater rim a few times at the end of March. The growth of the pyroclastic cone continued with Strombolian explosions of 10-25 m above the top of the cone during this time, and incandescence visible on clear nights. It was possible to see the new cone above the crater rim from the NW and W flanks (figure 80). Rumblings from the explosive activity were reported within 5 km of the cone. Although the three MODVOLC thermal alerts issued during the first week of March were the last through at least September 2017, weak explosions and nighttime incandescence continued during May as the pyroclastic cone continued to grow.

Figure (see Caption) Figure 80. The top of the new pyroclastic cone inside MacKenney crater at Pacaya was visible from the edge of nearby Cerro Chino crater, about 1 km NW, beginning in February 2017. Courtesy of INSIVUMEH (Reporte mensual, febrero 2017).

By June 2017, the steam plumes were rising about 800 m above the crater rim. The height of the pyroclastic cone remained at about 10 m above the crater rim, but continued to grow in volume and produce abundant steam and gas (figure 81). Similar emissions were reported during July, however, incandescence was only occasionally observed at night.

Figure (see Caption) Figure 81. Abundant steam and gas emerged from the upper part of the pyroclastic cone inside MacKenney crater at Pacaya on 17 June 2017. The dome rose height remained at about 10 m above the crater rim, shown in the lower left foreground. Courtesy of INSIVUMEH (Informe mensual de la actividad del Volcán Pacaya, junio 2017).

INSIVUMEH reported increased activity during August 2017 with the frequency of Strombolian explosions increasing to 5-7 per hour, and higher RSAM units recorded to 4,000; some material was ejected as high as 75 m above the crater rim, generating block avalanches as far as 100 m down the W flank. Explosions during 11 August reduced the height of the pyroclastic cone inside the crater such that it was no longer visible from the flank. Moderate to strong explosions were recorded a number of times during the month (figure 82).

Figure (see Caption) Figure 82. A thermal image of MacKenney crater at Pacaya on 18 August 2017 shows Strombolian activity at the summit. Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Pacaya, Semana del 19-25 de Agosto de 2017).

Seismic and explosive activity remained high during September 2017. Two significant events were recorded. On 5 September RSAM values peaked at 5,000 units and remained elevated for about six hours before dropping back to average values around 2,000. This corresponded with a period of rebuilding of the pyroclastic cone within the crater. INSIVUMEH reported Strombolian explosions ejecting material as high as 100 m above the crater rim during 21-22 September. The second event lasted for about three days during 23 and 26 September when there was an increase in the rate of explosions, registering up to 40 per hour. After destruction of part of the cone during August, it was rebuilt to a level about 10 m above the crater rim again during this time.

Infrared thermal data generally agrees well with observations of increased activity and lava flows during January-March 2017 (figure 83). However, reports from INSIVUMEH indicate that explosive activity continued at the pyroclastic cone during April-September, although only the largest events during August and September created thermal signals that were captured in the MIROVA data.

Figure (see Caption) Figure 83. MIROVA graph of infrared MODIS data for the year ending on 15 October 2017 at Pacaya shows the thermal signature associated with lava flows and explosive activity during January through March 2017. Although increased explosive activity was reported in August and September, the thermal signal was much smaller. Courtesy of MIROVA.

Geologic Background. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

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/); 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/).


Sabancaya (Peru) — December 2017 Citation iconCite this Report

Sabancaya

Peru

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

All times are local (unless otherwise noted)


Continuous pulses of ash emissions for ten months, February-November 2017

Activity that began in 1986 at Sabancaya was the first recorded in over 200 years. During the last period of substantial ash eruptions between 1990 and 1998 ashfall deposits up to 4 cm thick were reported 8 km E of the volcano. Intermittent seismic unrest and fumarolic emissions characterized activity from late 2012 through October 2016, with a few possible minor ash emissions unconfirmed during this period, and probable SO2 plumes.

Hybrid seismic events, related to the movement of magma, and SO2 emissions increased noticeably during September and October 2016. An explosive eruption period with numerous ash plumes began on 6 November 2016 and has continued throughout 2017. Continuous ash emissions with plume heights exceeding 10 km altitude were often recorded through February 2017. Thermal anomalies were first measured in satellite data in early November 2016, along with numerous significant SO2 plumes (BGVN 42:05). Details of the continuing eruptive activity at Sabancaya from February-November 2017 are discussed in this report with information from the two Peruvian observatories that monitor the volcano: Instituto Geofisico del Peru - Observatoria Vulcanologico del Sur (IGP-OVS), and Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico) (OVI-INGEMMET). Aviation reports and notices come from the Buenos Aires Volcanic Ash Advisory Center (VAAC), and satellite data is reported from several sources.

Images from December 2016. An expedition to Sabancaya during 9-18 December 2016 by photographer Martin Rietze recorded numerous ash emissions and the impacts of the ongoing eruption on the region (figures 31-36). Similar activity continued throughout 2017.

Figure (see Caption) Figure 31. Gas and a dense ash plume rose above Sabancaya during 12-15 December 2016 in this view taken 6.5 km NNE of the volcano. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 32. A column of ash drifted E from Sabancaya during 12-15 December 2016 while a cloud cap condensed on top of the plume. Image taken from 6.5 km NNE of the summit. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 33. An ash plume fanned out to the E from Sabancaya during 12-15 December 2016. Image taken from 15 km E. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 34. Sabancaya lies in the saddle between the older volcanic complexes of Ampato to the S (left) and Hualca Hualca to the N (right) in this view taken from 15 km E. It is the only one of the three to have erupted during the Holocene. An ash plume rose from Sabancaya during 12-15 December 2016, while ash from an earlier pulse is visible drifting S over Ampato. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 35. Trace amounts of ashfall from Sabancaya covered the region 10 km W of the volcano during 12-15 December 2016. Photo copyright by Martin Rietze, used with permission.
Figure (see Caption) Figure 36. An ash-and-steam plume rose vertically from Sabancaya during 12-15 December 2016 while a meteor streaked across the nighttime sky in this image taken 6.5 km NNE of the summit. Photo copyright by Martin Rietze, used with permission.

Summary of activity, February-November 2017. The persistent eruptive activity during February-November 2017 can be visualized by the continuous MIROVA plot of Log Radiative Power during this time (figure 37). The Buenos Aires VAAC issued 1,174 VAAC reports for Sabancaya during February-November 2017, with over 100 recorded each month (table 1). Tens of explosions were reported daily by OVI-INGEMMET and IGP-OVS throughout the period. Ash plumes usually rose to the 9-11 km altitude range (3,000-5,000 m above the summit), and drifted 30-50 km in many directions before dissipating. MODVOLC thermal alerts were reported between 2 and 16 times every month, and satellite data registered SO2 plumes with values greater than two Dobson Units multiple days each month (figure 38).

Figure (see Caption) Figure 37. MODIS infrared satellite data plotted by MIROVA for the 12 months ending 19 January 2018 show the continuous signature of thermal activity from Sabancaya during that time. Courtesy of MIROVA.

Table 1. Eruptive activity at Sabancaya, February-November 2017. Compiled using data from IGP-OVS/OVI-INGEMMET reports, the Buenos Aires VAAC, HIGP, and NASA GSFC.

Month VAAC Reports Avg Daily Explosions by week Max Plume Heights (m above crater) Plume Drift MODVOLC Alerts Days with SO2 over 2 DU
Feb 2017 108 58, 23, 19, 42 3,000-4,300 40 km, NW, N, S, SE, SW 6 12
Mar 2017 122 44, 36, 36, 37, 41 2,500-4,800 30-40 km, S, NW, SW, N 4 8
Apr 2017 113 27, 37, 36, 33 3,000-3,200 40 km NW, NE, SE, W, N 16 11
May 2017 117 41, 38, 39, 41 2,800-4,200 30-40 km NE, E, SE 4 3
Jun 2017 104 47, 31, 26, 15, 5 1,500-3,700 30-40 km E, SE, SW, S 4 5
Jul 2017 127 10, 19, 24, 40 3,500-5,500 40-50 km NW, S, E, N, SE 2 13
Aug 2017 124 65, 41, 46, 44 3,200-4,200 30-50 km N, SE, NW, S 12 10
Sep 2017 118 38, 29, 45, 45 2,500-3,500 30-40 km SE, E, NE 6 5
Oct 2017 120 42, 41, 47, 43 3,100-3,900 35-60 N, NW, W, S, SE, NE, E 9 8
Nov 2017 121 57, 66, 82, 78, 69 3,300-4,200 40-50 km N, NE, E, SE, NW, SW 11 10
Figure (see Caption) Figure 38. Numerous significant SO2 plumes were captured by the OMI instrument on the Aura satellite for Sabancaya during February-November 2017. Plumes drifted SSE on 4 March, 22 March, 30 July, and 6 August 2017 (top four images), and SW and W on 9 October and 10 November 2017 (bottom two images). The red pixels indicate values of Dobson Units (DU) greater than 2. Courtesy of NASA Goddard Space Flight Center.

Activity during February-November 2017. IGP-OVS and OVI-INGEMMET monitor seismicity, inflation and deflation, SO2 emissions, and visual activity with webcams from several locations around Sabancaya (figure 39). Ash plumes during February 2017 rose to heights of 3,000-4,300 m above the summit (figure 40). The average number of daily explosions decreased from 53 the first week to 19 the third week, and then increased to 42 during the last week. Ash plumes drifted up to 40 km in numerous directions.

Figure (see Caption) Figure 39. Stations where IGP-OVS and OVI-INGEMMET monitor seismicity (red), inflation and deflation (green), SO2 emissions (orange), and their webcam locations (yellow) for Sabancaya. Courtesy of IGP-OVS and OVI-INGEMMET weekly reports.
Figure (see Caption) Figure 40. Ash emission from Sabancaya, 12 February 2017. View from the OVI-INGEMMET webcam located near Coporaque, about 30 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 06 al 12 de febrero de 2017).

During March 2017 the number of daily explosions was very consistent averaging each week between 36 and 44 events. Maximum ash plume heights ranged from 2,500 to 4,800 m and drifted 30-40 km to either the NW or SW (figure 41). Ash fell in Pinchollo (20 km N) and Cabanaconde (22 km NW) during the last few days of the month.

Figure (see Caption) Figure 41. Ash emission from Sabancaya, 12 March 2017. Taken from OVI-INGEMMET webcam located about 4 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 06 al 12 de marzo de 2017).

Ash fell during the first week of April in Pinchollo, Maca (20 km NE) and Chivay (32 km NE). Plume heights during the month were slightly lower, ranging from 3,000-3,200 m and drifted 40 km in several directions. The frequency of daily explosions decreased slightly from March to an average each week ranging from 27 to37. The Buenos Aires VAAC reported that diffuse ash plumes drifted 100 km E on 9 April.

The frequency of daily explosions increased slightly during May; weekly averages ranged from 38 to 41. Plume heights were somewhat higher, at 2,800-4,200 m, and drifted 30-40 km in many directions (figure 42). There was a notable decrease during June 2017 in the number of daily explosions from an average during the first week of 47 to an average of only five at the end of the month. Deflation was observed in the GPS data after 21 June. Plume heights ranged from 1,500 to 3,700 m.

Figure (see Caption) Figure 42. On 20 May 2017 the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured this image of repeated puffs of ash rising from Sabancaya and drifting E. Courtesy of NASA Earth Observatory.

Activity increased steadily during July 2017. Daily explosions rose from an average of 10 during the first week to 40 the last week; ash plume heights were up to 5,000 m during those weeks (figures 43, 44) and drifted 50 km or more generally NW and SE. Ash plumes during the third week affected communities N of the volcano, including the villages of Cabanaconde, Pinchollo, Lari (20 km NE), Madrigal (20 km NE), Ichupampa (23 km NE), Maca and Achoma (21 km NE). Winds changed to the S on 22 July, so ashfall then affected Lluta (30 km SW), Huanca (75 km SSE), and some parts of Arequipa (80 km SSE).

Figure (see Caption) Figure 43. Ash and gas emission from Sabancaya rose several kilometers above the summit on 9 July 2017 in this OVI-INGEMMET image from their webcam located near Coporaque, about 30 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 03 al 09 de julio de 2017).
Figure (see Caption) Figure 44. On 26 July 2017, the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured this natural-color image of an ash plume drifting E from Sabancaya. The rising ash cast a shadow on the ground below. Courtesy of NASA Earth Observatory.

After averaging 65 explosions per day during the first week of August 2017, activity declined slightly to weekly averages of 41-46 explosions per day for the rest of the month. Plume heights ranged from 3,200 to 4,200 m and drifted generally 30-50 km NW or SE. During September 2017 activity was much the same. Plume heights ranged from 2,500-3,500 m, and drifted 30-40 km SE or NE. The weekly averages of daily explosion frequency varied between 29 and 45 events.

A noteworthy difference in activity occurred during October 2017, when there were tremors with ash emissions lasting for more than three hours per day during the last two weeks of the month. Daily explosion frequency averaged from 41 to 47 each week, and plume heights ranged from 3,100 to 3,900 m (figure 45). A few plumes drifted as far as 60 km during the third week of the month.

Figure (see Caption) Figure 45. A large ash and gas plume rose from Sabancaya on 21 October 2017 in this view from the OVI-INGEMMET webcam located near Coporaque, about 30 km NE. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitoreo de la Actividad del Volcan Sabancaya, Semana del 16 al 22 de octubre de 2017).

During November 2017 the number of daily explosions increased from an average of 57 the first week to 82 by the third week, decreasing to 69 at the end of the month. Plume heights remained at 3,300-4,200 m, drifting 40-50 km in several directions. Tremors with ash emissions lasted 1-2 hours most days.

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 (URL: http://ovi.ingemmet.gob.pe); Instituto Geofisico del Peru, Observatoria Vulcanologico del Sur (IGP-OVS), Arequipa Regional Office, Urb La Marina B-19, Cayma, Arequipa, Peru (URL: http://ovs.igp.gob.pe/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP), MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Martin Rietze (URL: http://www.mrietze.com/).


Santa Maria (Guatemala) — December 2017 Citation iconCite this Report

Santa Maria

Guatemala

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

All times are local (unless otherwise noted)


Slow growth of new lava dome, persistent ash plumes, and nearby ashfall, January-October 2017

The dacitic Santiaguito lava-dome complex on the W flank of Guatemala's Santa María volcano has been growing since 1922. The youngest of the four vents in the complex, Caliente, has been actively erupting with ash explosions, pyroclastic, and lava flows for more than 40 years. During July-September 2016, daily weak ash emissions were punctuated weekly by stronger emissions that sent ash plumes to altitudes of 3.3-6 km, and numerous pyroclastic flows were reported (BGVN 42:07). A new lava dome appeared in October and had filled half of the crater by years end; the frequency of explosions increased to 25-35 per day by December 2016. Guatemala's INSIVUMEH (Instituto Nacional de Sismologia, Vulcanologia, Meterologia e Hidrologia) and the Washington VAAC (Volcanic Ash Advisory Center) provided regular updates on the continuing activity during the time period of this report from January-October 2017.

Activity at the Caliente dome was very consistent from January through October 2017. A lava dome that began growing during October 2016 continued to slowly increase in size. Its growth generated constant steam and gas emissions that rose 100-500 m above the dome, and daily explosions with ash that generally rose to 2.8-3.3 km altitude (200-800 m above the dome). Ashfall was reported almost daily in villages and farms within 5-12 km S and SW, including San Marcos Palajunoj, Loma Linda, Monte Bello, El Patrocinio, La Florida, El Faro, Patzulin, and others. There were 15-35 explosions per day throughout this time. As the lava dome within the Caliente summit crater increased in size, more block avalanches were observed traveling tens of meters down the flanks of Caliente, outside the crater rim. Several lahars affected the major drainages during May-October.

Fifteen to twenty small to moderate daily explosions with ash emissions were typical for the Caliente dome complex during most of January 2017, in addition to constant blue and white gas emissions from the top of the lava dome. This same pattern continued throughout February, when the new dome inside the summit crater continued to grow (figure 63). By March, the dome was large enough that occasional block avalanches of fresh lava reached outside the summit crater, and descended a few tens of meters onto the flanks; the lava dome, growing since October 2016, had not quite filled the crater (figure 64).

Figure (see Caption) Figure 63. The lava dome inside the summit crater of Caliente grew noticeably between 17 January and 28 February 2017 at Santa María in this view to the S. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA FEBRERO 2017).
Figure (see Caption) Figure 64. Ash and steam rises during an explosion from the new lava dome inside the summit crater of the Caliente dome of Santa María. Recently ejected blocks are steaming on the flanks close to the webcam on 19 March 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA MARZO 2017).

By April 2017 the number of daily explosions had increased to 25-30, with similar energy levels and ash plume heights as earlier in the year. The Cabello de Ángel River continued downcutting through the 2014-2015 lava flows (figure 42, BGVN 41:09) creating a new channel that was 15-50 m deep (figure 65). During May, the number of daily explosions ranged from 9 to 26 (figure 66), and block avalanches from the new lava dome traveled short distances down the flanks. Two lahars were reported in May; on 6 May a lahar 30 m wide and 2.5 m deep descended the Cabello de Ángel drainage (a tributary of the Nimá I river on the S flank) carrying branches, tree trunks, and blocks up to 2 m in diameter. A smaller lahar on 31 May traveled down the Nimá I drainage and dragged smaller blocks and tree trunks down the channel.

Figure (see Caption) Figure 65. The Cabello de Ángel river cuts new channels through the 2014-2015 lava flows on the SE flank of Caliente dome at Santa María during April 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA ABRIL 2017).
Figure (see Caption) Figure 66. A moderate explosion on 30 May 2017 from Santiaguito at Santa María sends an ash plume to 2.6 km altitude that then drifted SW. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA Mayo 2017).

Explosions during June 2017 continued at the rate of 14-36 per day, with ash plumes rising to 2.7-3.3 km altitude (figure 67). Juvenile material continued to fill and overtop the crater rim, creating weak block avalanches down the flanks. Increased precipitation during June resulted in five lahars descending the Cabello de Ángel, Nimá I, and San Isidro drainages on 1, 5, 7, 9, and 16 June. They ranged in size from 15 to 25 m wide and 1 to 1.5 m high, and transported blocks 1-2 m in diameter. A larger lahar on 1 June that traveled down the Cabello de Ángel drainage was 30 m wide and 2 m high.

Figure (see Caption) Figure 67. An ash plume at Santa María's Santiaguito complex on 21 June 2017 rises to 2.9 km. Courtesy of INSIVUMEH (INFORME MENSUAL DE ACTIVIDAD VOLCÁNICA Junio 2017).

Similar explosive activity continued during July. On 5 July, a moderately-sized lahar descended the Cabello de Ángel drainage, a tributary of the Nimá I river. Near the El Faro estate, the lahar was 30 m wide and 1 m deep, and carried blocks 50 cm in diameter. On 14 July, another lahar traveled down the Nimá I drainage, which is a tributary of the Samalá. By August the summit crater of Caliente was nearly filled with the new lava dome, and overflows of block avalanches were more frequent, mostly traveling down the E flank (figure 68). A moderately-sized lahar descended the Nimá I drainage on 9 August.

Figure (see Caption) Figure 68. Fresh block avalanches were visible covering an area about 126 m wide and 246 m long near the summit of Caliente at Santa María when images from 31 July (left) and 2 August 2017 (right) were compared. Most of the block avalanches traveled down the east flank (A), but smaller avalanches traveled shorter distances down the NE flank (B). Courtesy of INSIVUMEH (Reporte Semanal de Monitoreo: Volcán Santiaguito (1402-03), Semana del 29 de julio al 04 de agosto de 2017).

Explosions with ash plumes rising hundreds of meters above the crater rim continued daily during September and October, and sent block avalanches down the NE and SE flanks of the dome. INSIVUMEH reported that on 11 October 2017 a 12-m-wide and 1.5-m-high lahar descended the Cabello de Ángel and the Nimá I drainages, carrying blocks up to 1 m in diameter. On 13 October, the seismic network detected moderate-to-strong lahars in the Cabello de Ángel and the Nimá I drainages triggered by heavy rain.

Relatively few VAAC reports were issued for Santa María during 2017 compared with the previous two years. The Washington VAAC observed an ash plume in satellite imagery drifting 15 km W at 4.6 km altitude on 14 January. Morning visible imagery on 1 February showed an ash plume 25 km SW at 3.8 km altitude. An ash emission was observed on 27 February a few kilometers WSW at or slightly above the summit. Multiple small puffs of ash extended 55 km WSW of the summit on 9 March, at 4.6 km altitude. An ash plume was centered 15 km NW of the summit at 3.8 km altitude and rapidly dissipating on 4 April. The next VAAC observation, on 2 June, was a small puff of ash located 30 km S of the summit. On 6 September, possible volcanic ash was drifting SW of the summit at 4.3 km altitude.

Infrared MODIS satellite data suggest low-level, persistent activity at Santa María throughout January-October 2017 (figure 69). This is consistent with photographs of a slowly growing lava dome at the summit, and persistent low-energy explosions with ash emissions and block avalanches during the year. There were no MODVOLC thermal anomalies during this time.

Figure (see Caption) Figure 69. Infrared MODIS thermal data graphed through the MIROVA system indicates a low but persistent level of thermal activity at Santa María for the year ending on 8 June 2017. This is consistent with the observations of a slowly growing lava dome inside the summit crater. Courtesy of MIROVA.

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/ ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); 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/).


Sinabung (Indonesia) — December 2017 Citation iconCite this Report

Sinabung

Indonesia

3.17°N, 98.392°E; summit elev. 2460 m

All times are local (unless otherwise noted)


Constant activity through September 2017, with ash plumes, block avalanches, and pyroclastic flows

Indonesia's Sinabung volcano, located on North Sumatra, had its first confirmed Holocene eruption between 27 August and 18 September 2010; ash plumes rose up to 2 km above the summit, and falling ash and tephra caused fatalities and thousands of evacuations (BGVN 35:07). It remained quiet after the initial eruption until 15 September 2013, when a new eruption began that has continued for over three years. Details of events during October 2016-September 2017 are covered in this report. Information is provided by, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), referred to by some agencies as CVGHM, the Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Centre (VAAC), and the Badan Nacional Penanggulangan Bencana (National Disaster Management Authority, BNPB).

Summary of activity during November 2013-September 2016. Thousands of evacuations took place during November and December 2013 when ash plumes reached heights between 6 and 11 km altitude multiple times. Ashfall from hundreds of pyroclastic flows in January 2014 covered communities in the region. Lava flows emerged from the summit in mid-January 2014 and traveled down the S flank. Pyroclastic flows on 1 February 2014 killed 17 people in the village of Sukameriah, located 3 km S of the summit (BGVN 39:01). The lava flow had advanced 2.5 km from the summit by 6 April 2014. Lava flows, ash plumes, and pyroclastic flows persisted throughout 2014 and 2015. Ash plumes generally rose up to about 5 km altitude, and pyroclastic flows traveled up to 4.5 km from the summit throughout this period (BGVN 39:10). Repeated lava dome growth and destruction was also reported by PVMBG during this time (BGVN 40:10).

Increases in lava dome volume and instability during June 2015 again led to evacuations of thousands living within 7 km of the volcano. Ash deposits were common in the communities up to 10-15 km away. Similar activity continued into 2016, with tens of pyroclastic flows affecting nearby communities during many months. In April 2016, over 9,000 people remained in evacuation centers. Ash plumes were reported 3-8 times each month by the Darwin VAAC between April and October 2016, with plume altitudes ranging generally from 3-5.5 km. Several fatalities were reported during May 2016 (BGVN 42:02). A lahar passed through Kutambaru village, 20 km NW of Sinabung, on 9 May and killed one and injured four people. A pyroclastic flow on 21 May 2016 killed 7 people in the village of Gamber, 4 km SE from the summit. Ashfall was reported during July 2016 more than 50 km NE, and incandescent lava was visible up to a kilometer from the summit. Continuous pyroclastic flows were reported on 25 August 2016, with an ash plume observed at 6.1 km altitude the following day.

Summary of activity during October 2016-September 2017. Ash plumes, block avalanches, and pyroclastic flows were all nearly constant at Sinabung throughout this period (table 7). The number of explosions recorded every month ranged from 37 (March 2017) to 105 (June 2017). The number of Volcanic Observatory Notices to Airmen (VONAs) each month ranged from 34 (September 2017) to 93 (June 2017). The Darwin VAAC reported ash plumes on 17 or more days every month of 2017 through September. Thermal anomaly signals also persisted throughout, likely caused primarily by dome growth and incandescent block avalanches.

Table 7. Ash plumes and explosions reported for Sinabung, October 2016-September 2017. Data from Darwin VAAC and PVMBG reports.

Month Days with Ash Plume Reports Ash Plume Altitudes (km) Ash Plume Drift Explosions reported (PVMBG) Number of VONA's issued (MAGMA) Comments
Oct 2016 5, 12, 26, 28-29, 31 3.4-4.6 km SE, E, SSE, NE -- -- --
Nov 2016 1, 2, 6, 11, 13, 14, 20, 29, 30 3.4-5.8 km E, W, E, NE, SE -- -- Multiple brief explosions; pyroclastic flows observed 1, 2 Nov
Dec 2016 15, 17, 19-21, 26, 27, 29-31 3.0-6.1 km SSE, E, S, SE, NW, S, SW -- -- Hotspot visible in satellite images on 30 Dec
Jan 2017 1, 8-15, 17-20, 22, 24, 26-31 3.4-5.5 km WSW, W, E, ESE, SW 101 58 Ash 50 km E and 75 km NE on 8 Jan; hot spot in satellite imagery 10 Jan
Feb 2017 1-14, 16-22, 24-26, 28 3.0-5.5, 6.7, 7.4 km SSE, S, NE, E, SE, SW, WSW, W 88 70 4 Feb explosion caused ash plume to 7.4 km altitude
Mar 2017 1, 2, 5, 7-18, 21, 22, 24, 25, 27, 29 3.0-5.5 km WNW, NW, SSE, NNW, W, S, SW, NE, N, E, ESE 37 34 Highest plumes, on 17 and 18 March, rose to 5.5 km altitude and drifted W and WSW
Apr 2017 5, 7, 9-20, 22, 24-30 3.0-5.5, 8.4 km ESE, E, SE, WNW, SSE, SSW, W, SW, WSW, NNE, S 104 58 Large explosion on 9 April, ash plume reported by a ground observer to 8.4 km altitude, drifting SE
May 2017 2-12, 14-17, 19-20, 23-31 3.4-8.8 km WSW, WNW, NW, SW, S, E, SE, NE, ESE, W, ENE 87 58 Series of large explosions during 17-20 May, several plumes rose to altitudes between 6.1 and 8.8 km
Jun 2017 1-27, 29, 30 2.7-5.5, 6.4 km NE, N, WNW, ENE, ESE, SE, SW, W, S, E, NW, NE, SSW, SSE 105 93 --
Jul 2017 2-3, 6, 8-11, 14, 15, 17-31 2.7-6.1 km ESE, NW, ENE, E, SE, W, WSW, SSW, ENE, NE 91 64 --
Aug 2017 1, 2, 6-10, 12, 16, 23-29, 31 2.7-5.5, 6.4 km ENE, SE, E, S, W, ESE, WNW, NNW, WSW 61 76 Large explosion on 2 Aug with ashfall in many places; Hotspots reported 6, 7 Aug
Sep 2017 1, 3, 7, 8, 12-16, 18, 22, 23, 25-29 3.0-5.5, 6.1-6.4 km ENE, WSW, E, W, NW, SE, ESE, SW 55 34 --

Activity during October 2016-September 2017. The visiting head of PVMGB observed an ash plume from an explosion on 28 September 2016. Ash emissions continued at Sinabung, with multiple aviation advisories issued by the Darwin VAAC through the end of 2016. Explosions generated ash plumes that rose to altitudes of 3.0-6.1 km, and drifted in multiple directions during the last quarter of 2016 (table 7). Pyroclastic flows were observed several times during November (figure 28), and a hotspot was visible in satellite imagery on 30 December.

Figure (see Caption) Figure 28. A large pyroclastic flow descended the E flank of Sinabung on 29 November 2016 in this view taken a few kilometers SE of the volcano. . Courtesy of Sadrah Peranginangin.

Activity during January 2017 was dominated by incandescent block avalanches (figure 29). PVMBG reported 101 ash-bearing explosions with plumes rising up to 1 km above the summit, and pyroclastic flows that traveled up to 3 km ESE and 500 m S. A You Tube video captured a pyroclastic flow and ash plume on 17 January 2017. Ash plumes were reported by the Darwin VAAC on 21 days during the month with plume heights ranging from 3.4-5.5 km altitude.

Figure (see Caption) Figure 29. Block avalanches descended the E flank of Sinabung many times during January 2017, including at 0134 local time on 17 January, as seen looking to the WSW. Courtesy of Endro Lewa.

Near-daily ash plumes from 88 explosive events during February 2017 rose to heights of 500-5,000 m above the summit (3.0-7.5 km altitude), and pyroclastic flows traveled 3.5 km E and 1 km S. The Darwin VAAC reported ash emissions on all but three days of the month. A large explosion on 4 February sent an ash plume to 7.4 km altitude that then drifted SE (figure 30), and on 9 February a large ash plume drifted WSW at 6.7 km altitude.

Figure (see Caption) Figure 30. Photo of an ash plume at Sinabung on 4 February 2017 that rose more than 5 km above the summit and slowly drifted SE. Photo taken from Kabanjahe, about 13 km SE. Courtesy of Sadrah Peranginangin.

Block avalanches continued to travel 500-2,000 m down the ESE flank during March 2017. Ash plume heights ranged from 500 to 3,000 m above the summit (3.0-5.5 km altitude) during the 37 explosion events reported by PVMBG (figure 31). Pyroclastic flows traveled 2.5 km down the S flank. The highest plumes of the month were recorded on 17 and 18 March; they rose to 5.5 km altitude and drifted W and WSW. The Darwin VAAC reported ash plumes during 21 days of the month.

Figure (see Caption) Figure 31. Photo of an ash plume at Sinabung on 29 March 2017 at 1548 local time, in this view looking W. Courtesy of Igan S. Sutawijaya.

During April 2017, block avalanches were observed traveling between 800 and 3,500 m down the SSE flank (figure 32), and 104 explosions were recorded by PVMBG. Ash plumes from these explosions rose to heights of 800 to 3,500 m above the summit. Pyroclastic flows descended 2.8 km down the S flank. A large explosion on 9 April reported in a VONA by a ground observer sent an ash plume to 8.4 km altitude, drifting SE. Pyroclastic flows were also observed on the SE flank. The Darwin VAAC reported ash plumes on 22 days of the month.

Figure (see Caption) Figure 32. Pyroclastic flows descended the S flank (left) and block avalanches descended the E flank of Sinabung near midnight on 4 April 2017, while a small explosion took place at the summit. Image taken from a small village a few kilometers from the base of the SE flank. Courtesy of Sadrah Peranginangin.

Ash plumes rose between 500 and 6,000 m above the summit during May 2017. Eighty-seven explosive events were recorded (figure 33), and block avalanches were observed traveling 500-1,500 m down the S and SE flanks. The Darwin VAAC reported ash plumes on 26 days during the month. A series of large explosions during 17-20 May resulted in several plumes that rose to altitudes between 6.1 and 8.8 km, in addition to numerous others at lower altitudes between 3.7 and 5.8 km. As of late May, over 9,000 people were still displaced from the volcano, living in either shelters or evacuation camps, according to BNPB.

Figure (see Caption) Figure 33. Strombolian activity at the summit of Sinabung on 1 May 2017. Courtesy of Sadrah Peranginangin.

Incandescent block avalanches and pyroclastic flows were persistent during June 2017. They moved down the SE and S flanks up to 2,500 m. PVMBG reported 105 explosive events with plume heights ranging from 500-4,000 m above the summit (figure 34). The largest explosions of the month, on 17 June, generated ash plumes that rose to 6.4 km altitude and drifted 15 km SW. The Darwin VAAC reported ash emissions every day except for 28 June.

Figure (see Caption) Figure 34. Ash plume rose from Sinabung on 26 June 2017. The view is from a small village about 7 kilometers ENE of the summit. Courtesy of Endro Lewa.

PVMBG reported 91 explosive events during July 2017 that produced ash plumes that rose 500-3,500 m above the summit. They also noted four pyroclastic flows that traveled 1-3 km down the S and SE flanks. Block avalanches continued on the S and E flanks, traveling as far as 3 km. The Darwin VAAC issued reports on 24 days during July. The largest explosions occurred on 20 and 23 July when ash plumes rose to 5.8 and 6.1 km altitude and drifted WSW, ENE, and SE (figure 35).

Figure (see Caption) Figure 35. A large ash plume from Sinabung rose more than 5 km above the summit on 20 July 2017. The view is from a small village about 7 kilometers ENE of the summit. Courtesy of Endro Lewa.

Although fewer explosive events (61) were reported during August, block avalanches continued to travel 500-2,300 m down the SE flank. Ash plumes rose 500-2,000 m above the summit; 22 pyroclastic flows traveled up to 4.5 km down the SE flank. The Darwin VAAC issued reports of ash emissions on 17 days of the month.

A large explosion on 2 August sent ash emissions to 5.5-6.4 km altitude (figure 36). The S-drifting plume brought ashfall to the communities of the Ndokum Siroga District (SE), Simpang (7 km SE), Gajah (8 kmE), Kabanjahe (13 km SE), and Naman Teran (5 km NE) (figures 37 and 38). PVMBG reported that the explosions of 2 August destroyed the lava dome at the summit, which had grown since April 2017 to about 2.3 million m3 in size before the explosion (figure 39). The volume of the lava dome was an estimated 23,700 m3 on 6 August, after the explosions.

Figure (see Caption) Figure 36. Photo showing the large eruption from Sinabung on 2 August 2017, with a dark ash plume and pyroclastic flows. Image taken 5 kilometers E of the summit, looking W. Courtesy of Endro Lewa.
Figure (see Caption) Figure 37. Many communities were affected by ashfall and pyroclastic flows from the large explosion at Sinabung on 2 August 2017. This village is located near the base of the E flank. Courtesy of Endro Lewa.
Figure (see Caption) Figure 38. A village on the SE flank of Sinabung, was covered with ash on 3 August 2017 after a large eruption the previous day that sent a column of ash to 4.2 km altitude and a pyroclastic flow down the adjacent slope, destroying vegetation in its path. Courtesy of Xinhuanet (Xinhua/YT Haryono).
Figure (see Caption) Figure 39. The dome at Sinabung on 3 August 2017 one day after its destruction in a large explosion. The volume according to PVMBG was 2.3 million cubic meters in early July and measured only 23,700 cubic meters after the explosion. Courtesy of Endro Lewa.

The explosions also produced pyroclastic flows that traveled SE and E 2.5-4.5 km and reached the Laborus river, increasing the size of a natural dam on the river that had been evolving from previous deposits. Ashfall was also reported to the E and NE at Berastagi (12 km E). Hot spots were recorded in satellite imagery on 6 and 7 August. Additional ash plumes to similar altitudes (5.5-6.4 km) were reported several other times during August (figure 40 and 41).

Figure (see Caption) Figure 40. An explosion at Sinabung on 8 August 2017. The ash plume rises 2,000 m and a pyroclastic flow descends the E flank in this view from a small village about 7 km ENE of the summit. Courtesy of Endro Lewa.
Figure (see Caption) Figure 41. Ash and steam plumes and block avalanches at Sinabung on 25 August 2017 in this view from a small village about 7 km ENE of the summit. Courtesy of Endro Lewa.

The impact of numerous pyroclastic flows on the SE and E flanks during 2016-2017 caused a natural dam to form on the Laborus River near Desa Sukanalu and Kutanonggal Village (figure 42). The estimate of the area covered by water behind the dam was over 100,000 m2 prior to the early August explosions, about one-tenth the size of Lake Laukawar, located further upstream.

Figure (see Caption) Figure 42. A natural dam on the Laborus River (right, 'Bendungan Laborus') was created by numerous pyroclastic flows; the lake area was 123,000 square meters prior to the 2-3 August explosions. Courtesy of PVMBG (Kegiatan Gunungapi Sinabung Pasca Letusan 2-3 Agustus 2017, 22 August 2017).

Activity diminished only slightly during September 2017. PVMGB reported 55 explosive events with ash plumes that rose 500-4,000 m above the summit (figure 43). Block avalanches fell 500-1,500 m down the SE flank, and five pyroclastic flows were observed in the same area which traveled 1.5 – 2.0 km. Reports of ash emissions were issued by the Washington VAAC on 17 days of the month. The highest ash plume during the month rose to 6.4 km altitude on 25 September.

Figure (see Caption) Figure 43. A lava dome and ash plume at the summit of Sinabung on 17 September 2017. Courtesy of Sadrah Peranginangin.

Thermal anomalies. Thermal anomalies persisted throughout October 2016-September 2017. MODVOLC thermal alerts were reported 1-10 times every month except for June 2017. The MIROVA system recorded persistent low to moderate radiative power (figure 44) consistent with the dome growth, explosions, and block avalanches reported by PVMBG.

Figure (see Caption) Figure 44. Thermal anomaly data shown on a MIROVA graph of log Radiative Power at Sinabung for the year ending 18 December 2017. Persistent intermittent pulses of thermal energy are consistent with dome growth and block avalanches reported by PVMBG. Courtesy of MIROVA.

References: Associated Press, 2017, Raw: Indonesia's Sinabung Volcano Spews Hot Ash (URL: https://www.youtube.com/watch?v=R3KhjpHVeaw), posted to YouTube 17 January 2017.

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 (URLs: http://www.vsi.esdm.go.id/, https://magma.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral, (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Xinhua News (URL: http://news.xinhuanet.com/english/2017-08/03/c_136497362.htm); Igan S. Sutawijaya (URL: https://www.facebook.com/igansutawijaya/); Endro Lewa (URL: https://www.instagram.com/endro_lewa/); Sadrah Peranginangin (URL: https://www.facebook.com/sadrah.peranginangin).


Tungurahua (Ecuador) — December 2017 Citation iconCite this Report

Tungurahua

Ecuador

1.467°S, 78.442°W; summit elev. 5023 m

All times are local (unless otherwise noted)


Nearly constant ash emissions and frequent lahars during July-December 2015

Eight distinct episodes of activity occurred at Ecuador's Tungurahua from November 2011 through December 2014 that included 10-km-high ash plumes, Strombolian activity, pyroclastic flows, lahars and a lava flow (BGVN 42:05). Another distinct eruptive episode, during April and May 2015, consisted primarily of persistent ash emissions (BGVN 42:08). Abundant rainfall during the first half of 2015 led to numerous lahars, some of which disrupted travel on local roads. Continuing activity from July through December 2015 is described below based on information provided by the Observatorio del Volcán Tungurahua (OVT) of the Instituto Geofísico (IG-EPN) of Ecuador, and aviation alerts from the Washington Volcanic Ash Advisory Center (VAAC).

After the last ash emissions reported in mid-May 2015, only minor emissions of steam with no ash rising to 500 m above the crater were reported during June. However, activity increased again during July, when ashfall was reported nearly every day at the lookout stations around Tungurahua, and several larger explosions produced ash plumes that rose as high as 7.5 km altitude, about 2.5 km above the summit. Frequent rains during July resulted in lahars in six different drainages. Multiple explosions during August caused ash plumes and ashfall in communities within 20 km several times every week with the highest plume rising to 8.5 km altitude. A similar pattern continued during September 2015, with longer periods of seismic tremor, persistent ash emissions, and Strombolian activity that sent block avalanches down the flanks. The number and intensity of explosions increased in October; multiple explosions every week resulted in ashfall in communities within 25 km, mostly to the NW, and low-energy Strombolian activity persisted throughout the month. The strongest explosions of the period began with a series of seismic tremors on 10 November that persisted for nine days; daily ash plumes rose to between 7 and 8 km altitude, with the highest plume reported rising to at least 9.1 km altitude. Several millimeters of ashfall were reported in the nearby communities and at lookout stations, and the ash plume was recognized in satellite data more than 250 km from the summit before dissipating. Activity tapered off by the end of November, and only weak steam emissions were reported during December 2015.

Activity during July-September 2015. Persistent steam plumes in July rose up to 500 m above the summit crater and drifted generally W, often carrying small quantities of ash. Several lookout stations in communities located within 20 km NW and SW reported ashfall almost every day, including Choglontús (13 km WSW), Bilbao, and El Manzano (8 km SW). Other stations that reported ashfall during the month included Palitahua, Mocha, Chacauco, and Pillate. IG-EPN reported explosions with larger ash plumes on 3, 12, and 14 July that rose as high as 7.5 km (figure 86). Increased seismicity on 21 and 22 July was associated with emissions that caused ashfall in most of the reporting locations.

Figure (see Caption) Figure 86. An ash plume rises 1 km above the summit crater at Tungurahua on 3 July 2015. Courtesy of OVT, IG-EPN, photo by P. Espin (Informe No. 802, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 30 de junio al 07 de julio de 2015).

The Washington VAAC reported the ash plume on 3 July extending 25 km WSW from the summit at 5.2 km altitude (200 m above the crater); they also detected a faint hotspot in satellite imagery. They reported an ash plume extending 35 km WSW late in the day at 6.4 km on 14 July visible in satellite imagery (figure 87). An ash plume reported by the Washington VAAC on 31 July was moving SW at 6.7 km altitude.

Figure (see Caption) Figure 87. One of several explosions on 14 July 2015 at Tungurahua created an ash plume that rose at least 2 km above the summit and drifted W. Courtesy of OVT, IG-EPN, photo by F. Vasconez (Informe No. 803, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 07 de julio al 14 de julio de 2015).

Lahars were reported during 5-7, 18-19, 22-23, and 29-30 July in the Chontapamba, Rea, Achupashal, Juive, Pondoa and Puela river drainages. Heavy rain on 18 and 19 July generated mudflows in the Juive, Pondoa and La Pampa ravines. Blocks 40 cm in diameter were reported in the Puela River on 22 July, and blocks 1 meter in diameter were reported in the Chontapamba river on 29 July.

There were fewer events with ash emissions during August compared to July. A lahar sent 40-cm-diameter blocks down the Mapayacu ravine on 14 August. Two explosions on 15-16 August caused ashfall in Choglontus, Manzano, and Chontapamba. Small lahars from the Rea and Romero drainages blocked the Baños-Penipe road on 16 August. An explosion on 18 August sent an ash plume WSW and caused ashfall in Choglontus; the next day reddish ash and steam emissions around 1000 local time caused ashfall again in Choglontus. Black ashfall was reported there on 22 August. Increased seismic activity with several explosions on 25 August was accompanied by ash plumes that caused ashfall in Chontapamba, Pillate, Bilbao, and Juive Grande. Gray ash was reported in Chinchicoto and Yanayacu, and thick black ash was reported in Rumipamba, Pingili and Mocha. Fine-grained gray ash was reported in Mocha on 27 August.

The Washington VAAC reported occasional emissions of gas and minor volcanic ash on 1 August 2015. A pilot report of an ash plume rising to 7 km altitude and drifting W on 15 August was not detected in satellite imagery due to weather clouds, although ashfall was reported within 15 km of the summit. Another pilot report on 20 August noted an ash plume to 8.5 km altitude. The altitude of an ash plume spotted drifting W on 25 August was estimated to be between 7.6 and 9 km. Ongoing emission of gas and possible minor ash was reported on 30 August at 6.7 km altitude moving W; the faint plume later detected in satellite imagery was moving WNW and extended about 50 km from the summit.

Mudflows from substantial rain on 1 and 7 September 2015 affected the Achupashal ravine and again disrupted travel on the Baños-Penipe road (figure 88). An ash plume on 2 September reached 3 km above the crater and drifted NW, causing ashfall in Pillate, Quero, Santuario, La Galera and El Rosario. Asfall was reported the next day in El Manzano and Choglontus. The Washington VAAC reported the ash plume at 8 km altitude on 2 September; the satellite imagery showed it extending 15 km WNW.

Figure (see Caption) Figure 88. The Baños-Penipe road is frequently damaged by lahars in the Quebrada de Achupashal at Tungurahua, making travel difficult. The muddy water on 7 September 2015 washed out the road again. Courtesy of OVT, IG-EPN, photo by B. Bernard at 1359 local time (Informe No. 811, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 01 de septiembre de 2015 al 08 de septiembre).

Moderate to high amounts of ash characterized the emissions on 11 September 2015 (figure 89). The plumes rose 2 km above the crater, drifted W and caused slight ashfall in Chonglontus and El Manzano. Only Chonglontus reported additional ashfall the next day. The Washington VAAC initially reported the ash plume at 7.3 km altitude extending 40 km SW on 11 September. About 6 hours later, the leading edge of the plume was dissipating about 170 km SW. This was followed by a new ash plume late in the day that rose to 5.8 km altitude and drifted 15 km WSW from the summit. Slight incandescence was reported on 13 September along with minor ash and steam emissions that were moving W at 7.6 km altitude.

Figure (see Caption) Figure 89. An ash plume drifts W from Tungurahua on 11 September 2015. Courtesy of OVT, IG-EPN, photo by S. Santamaria (Informe No. 811, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 08 de septiembre de 2015 al 15 de septiembre).

Constant emission of moderate amounts of ash on 19 September 2015 created an ash plume that rose to 2 km above the crater and drifted NW. Ashfall was reported in El Manzano and Pillate. An explosion late in the day rattled structures in Pondoa, and was followed by observations of incandescence at the crater shortly after midnight. Ashfall was reported to the W in Pillate, El Manzano, Bilbao, Motilones, Chontapamba, and Choglontus the following day. Ongoing emissions were not visible in satellite imagery due to weather clouds. A sudden deflation in the deformation data was recorded on 19 September. Similar deflation events preceded major explosions in July 2013 and February 2014.

Several hours of seismic tremor on 27 September produced an ash-rich plume and incandescent blocks which descended the W flank. This was followed by additional explosions and periods of tremor, some lasting for more than an hour (figure 90), that produced ash plumes drifting SW. Ashfall was reported in the towns of Manzano, Choglontus, Cahuají, and Palictahua. Additional ashfall was reported the next day in Choglontus and Manzano. The Washington VAAC spotted a faint ash plume moving W in multispectral imagery on 27 September, and another plume at 6.7 km altitude moving slowly NW the next day around noon. New fumaroles not previously observed below the W flank of the crater were observed on 29 September for the first time.

Figure (see Caption) Figure 90. Lengthy tremors that registered at the seismic station RETU coincided with ash-rich plumes and incandescent blocks at Tungurahua between midnight and noon local time on 27 September 2015. Courtesy of OVT, IG-EPN (Informe No. 814, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 22 al 29 de septiembre de 2015).

Activity during October-December 2015. Tremors were followed by a significant explosion on 4 October 2015 that produced ash emissions and block avalanches that traveled down the W flank. Ashfall reports were issued from the communities of Manzano, Choglontus, and Cahuají, all located to the SW. The Washington VAAC reported the ash plume 35 km WSW of the summit at 9.1 km altitude. Seismic activity increased beginning on 8 October. On 11 October, four explosions produced Strombolian-style activity with incandescent blocks traveling down the Chomtapamba and Achupashal ravines, an ash plume rising 2 km above the crater, and ashfall in regions to the NW and SW including Manzano, Choglontus, Puela and Mocha. The Washington VAAC reported the ash plume extending W from the summit at 7.9 km altitude. Around 2000 local time, the ash plume resembled a large mushroom cloud, and loud noises were reported from Cusua. There were numerous reports of incandescent blocks and explosions heard on the N and E flanks during the evening and overnight into the next morning (figure 91). Ashfall was again reported in Choglontus on 13 October.

Figure (see Caption) Figure 91. Incandescent blocks descend the upper flank of Tungurahua at 1909 local time on 11 October 2015. Courtesy of OVT, IG-EPN, photo by E. Telenchana (Informe No. 816, Síntesis seminal del estado del Volcán Tungurahua, Semana: Del 06 al 13 de octubre de 2015).

An explosion in the early morning hours of 14 October was heard at all of the stations around the volcano. It was followed by ashfall in Choglontus. An ash emission on 19 October rose 1 km above the crater and drifted W and SW, producing ashfall in Choglontus, Bilbao, Pillate, and Cotaló. The Washington VAAC reported the plume extending 55 km NW of the summit at 6.7 km altitude. The next day, ongoing seismic data suggested frequent diffuse ash emissions. A plume was detected in multispectral data at 7.6 km altitude radiating E and rapidly dissipating. That afternoon (20 October), ashfall was reported in the Punzupala area. Ashfall continued from daily emissions for the next week with the most ashfall reported from Manzano, Choglontus, Bilbao, and Chacauco. Communities with trace amounts of ashfall included Ambato, Quero, Cevallos, Huachi, Chiquicha, Huambaló, Cotaló, and Pillate.

Incandescent material was observed traveling more than 1,000 m down the W flank from an explosion on 25 October. Local television reported ashfall in Ambato, Cevallos, Quero, and parts of Mocha and Tisaleo later that day. Swarms of LP earthquakes followed by episodes of ash emissions and low-energy Strombolian activity continued for the remainder of the month and into early November, causing sporadic ashfall in nearby villages. A small lahar was reported in the La Pampa ravine on 30 October.

An emission on 2 November 2015 created an ash plume that rose about 1.5 km above the crater and drifted E and NE; small quantities of ash were reported in the upper Runtun area. Incandescence at the summit crater from Strombolian activity was observed that night and for several days following. Heavy rains on 7 November caused mudflows in the Romero, Pingullo, and Achupashal ravines, and a larger lahar with meter-size blocks in the Chontapamba ravine. The Washington VAAC noted a dark emission from the volcano drifting W on 8 November at 5.5 km altitude.

A new series of tremors beginning on 10 November, coincided with more than a week of continuous ash emissions which reached 3.5 km above the crater and drifted in several directions. Incandescence was observed at night, and incandescent blocks descended generally up to 500 m down the NW, N, and E flanks during this period (figure 92).The Washington VAAC first reported an ash plume at 7.6 km altitude late in the evening on 10 November and continued with a constant series of reports for the next nine days. Most of the plumes were reported between 7 and 8 km altitude, drifting generally W (figure 93). The ash plumes produced heavy black ashfall in Manzano, Choglontus, Bilbao, Mocha, Quero, Cotaló, Tisaleo, Penipe and Cevallos. An ash plume was visible about 130 km W by midday on 11 November, and the plume had reached 8.2 km altitude. Loud noises were reported numerous times from the nearby communities for several days. On 12 November the Washington VAAC reported volcanic ash observed in satellite data extending 200 km WNW at 9.1 km altitude. Ashfall was heavy enough on 14 November to cause tree branches near Choglontus to bend under the weight of the ash.

Figure (see Caption) Figure 92. Strombolian activity from the summit of Tungurahua causes incandescent blocks to fall 500 m down the flanks of on 14 November 2015. Courtesy of OVT, IG-EPN, photo by V. Valverde (Informe No. 821, Síntesis seminal del estado del Volcán Tungurahua, Semana: 10 al 17 de noviembre de 2015).
Figure (see Caption) Figure 93. A dense ash plume rises from the summit of Tungurahua and drifts W on 17 November 2015. A small pyroclastic flow is visible on the NW flank (right side of image). Courtesy of OVT, IG-EPN, photo by S. Santamaria (Informe No. 822, Síntesis seminal del estado del Volcán Tungurahua, Semana: 17 al 24 de noviembre de 2015).

A plume on 15 November 2015 rose more than 5 km above the crater (10 km altitude), according to IG-EPN, and sent blocks about 1,000 m down the flanks. On 18 November, the Washington VAAC reported a narrowing plume extending 270 km W from the summit. The largest ashfalls occurred during the night of 18-19 November. Strombolian activity sent blocks 800 m down the flanks during the night, and a strong "jet" was observed in the eastern part of the crater. Incandescent material was observed from two eruptive vents late on 18 November. Five millimeters of ash were reported from the solar panels at the Tablor station on 19 November, deposited in less than 24 hours (figure 94). IG-EPN reported this event as one of the most significant ashfall events since 2010; many crops and livestock animals were affected. Dense ash emissions tapered off after 19 November, and smaller, less dense plumes rose 2 km above the crater on 22-23 November. The University of Hawaii's MODVOLC system issued thermal alerts for Tungurahua on 15 (2) and 19 (3) November, the only time during 2015. Significant sulfur dioxide (SO2) emissions were captured by the OMI instrument on the Aura Satellite during the mid-November episode from 11-19 November (figure 95).

Figure (see Caption) Figure 94. A 5-mm thick layer of ash was deposited on the solar panels of the Tablon station at Tungurahua in less that 24 hours on 19 November 2015. Courtesy of OVT, IG-EPN, photo by S. Santamaria (Informe No. 822, Síntesis seminal del estado del Volcán Tungurahua, Semana: 17 al 24 de noviembre de 2015).
Figure (see Caption) Figure 95. Substantial SO2 plumes originating from Tungurahua were recorded by the OMI instrument on the Aura satellite during 10-19 November 2015. Top left: the plume from Tungurahua drifts WSW while a smaller plume from Cotopaxi is visible about 90 km N on 10 November. Top right: the plume from Tungurahua drifts WNW on 12 November at the bottom of the image, a much smaller plume drifts W from Cotopaxi immediately above it, and a third SO2 plume is visible drifting WSW from Nevado del Ruiz in Colombia 750 km NNE. Lower left: a larger plume on 14 November drifts WSW from Tungurahua and probably includes some gas from Cotopaxi. Lower right: a large plume from Tungurahua disperses W on 17 November for well over 500 km. Courtesy of NASA Goddard Space Flight Center.

A seismic swarm with 33-35 events per hour began on 25 November, and tapered off to 3-5 events per hour by 30 November 2015. There was no increase in surface activity during the swarm, but rather a gradual decrease, with no significant ashfall reported during the last week of November. Activity diminished significantly during December 2015. Weak steam emissions that reached no higher than 500 m above the crater were typical. Seismicity remained low, and there were no reports of ash emissions or ashfall in the area.

Geologic Background. Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.

Information Contacts: Instituto Geofísico (IG), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec ); 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); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Ulawun (Papua New Guinea) — December 2017 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Intermittent ash plumes during June-November 2017

Activity at Ulawun has been characterized by intermittent seismic activity and weak ash emissions. The last significant episode was during October-November 2016 (BGVN 41:12). This report summarizes the next eruption, which began on 11 June 2017 and continued sporadically at least through October 2017. Data were provided by the Rabaul Volcano Observatory (RVO) and Darwin Volcanic Ash Advisory Centre (VAAC).

RVO reported that during 1 May-23 June 2017, white plumes rose from Ulawun. Seismicity was low and dominated by small low-frequency earthquakes, although RSAM values slowly increased and then spiked on 13 June. Ash emissions began on 11 June and then became dense during 21-23 June. Volcanic ash advisories from the Darwin VAAC warned of ash plumes from between 24 June and 3 November 2017 (table 5); no further volcanic ash warnings were issued after 3 November. Plumes generally rose to altitudes of 2.4-3 km, or a maximum of 700 m above the summit.

Table 5. Ash plumes from Ulawun during January-November 2017, based upon analyses of satellite imagery. Courtesy of Darwin VAAC.

Dates Plume altitude (km) Plume drift
24-26 Jun 2017 3 W
28 Jun 2017 2.7 W
04-08 Aug 2017 2.4-2.7 NW, W, and SW
09-10 Aug 2017 2.4 NW, W
17-18 Aug 2017 2.7 W
31 Aug-01 Sep 2017 2.7 SW, W, NW, and N
05 Sep 2017 2.7 SW
25 Sep 2017 3 WSW
26-27 Oct 2017 2.4 130 km S and SE
03 Nov 2017 3 NNE

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the N coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1,000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: 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/); 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.


Villarrica (Chile) — December 2017 Citation iconCite this Report

Villarrica

Chile

39.42°S, 71.93°W; summit elev. 2847 m

All times are local (unless otherwise noted)


Lava lake level fluctuates and Strombolian activity persists during October 2016-November 2017

Historical eruptions at Chile's Villarrica (figure 34), documented since 1558, have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Lava flows emerging from the glacier-covered summit created deadly lahars in 1964 and 1971 (CSLP 95-71); a similar event in late 1984 led to evacuations and no fatalities occurred. Since then, an intermittently active lava lake has been the source of explosive activity, incandescence, and thermal anomalies. Renewed activity in early December 2014 was followed by a large explosion on 3 March 2015 that included a 9-km-altitude ash plume. Significant thermal anomalies from continued Strombolian activity at the lava lake and small ash emissions persisted through October 2016 (BGVN 41:11). Activity has continued during October 2016-November 2017, with information provided primarily by the Southern Andes Volcano Observatory, (Observatorio Volcanológico de Los Andes del Sur, OVDAS) part of Chile's National Service of Geology and Mining (Servicio Nacional de Geología y Minería, SERNAGEOMIN), and Projecto Observación Villarrica Internet (POVI), part of the Fundacion Volcanes de Chile, a research group that studies volcanoes across Chile.

Figure (see Caption) Figure 34. View of Villarrica from the town of Villarrica located 30 km NW on 10 November 2016. The active lava vent was also photographed the same day (see figure 40). Courtesy of Cristian Gonzalez G.

Steam-and-gas emissions rising 200-1,000 m above the summit were observed throughout the period. The lava lake level inside the summit crater changed elevation by as much as 15 m during October 2016. Fluctuations of several meters up and down each month were reported through February 2017, and again in October 2017. Persistent minor gas-and-ash emissions, with small blocks and lapilli ejected onto the crater rim, were captured by the webcams and observed by visitors near the summit every month. Strombolian explosions and a "lava jet" sent ejecta more than 100 m above the crater rim during February 2017, and incandescent material rose 60 m above the crater rim on 1 July. Increased seismicity was detected during November 2017.

Activity during October-December 2016. Weak emissions of steam, gases, and volcanic ash near the summit were visible in the webcam during October 2016. The Buenos Aires Volcanic Ash Advisory Center (VAAC) noted a pilot report of an ash plume moving NNW on 20 October 2016 at 3.7 km altitude, slightly less than a kilometer above the summit. OVDAS reported that during the month, steam plumes rose less than 700 m and incandescence was visible at night when weather conditions permitted viewing of the summit. The MODVOLC thermal anomaly system issued 11 alerts during October. During several visits to the summit that month, POVI scientists observed that the lava lake had risen 15 m (figure 35) to a level that had been previously observed on 18 December 2015, 29 January, 28 March, and 18 September 2016. A small pyroclastic cone was visible inside the summit crater on 28 October (figure 36); by 30 October, most of it had collapsed and molten lava was again visible at the center (figure 37).

Figure (see Caption) Figure 35. Between 17 and 27 October 2016, the lava lake rose about 15 meters inside the summit crater of Villarrica, reaching a similar level observed on 18 December 2015, 29 January, 28 March, and 18 September 2016. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 36. A small pyroclastic cone is visible at the bottom of the summit crater at Villarrica on 28 October 2016 (red arrows). On the left slope sub-parallel annular fissures are visible (yellow arrows), indicating the imminent collapse of the nested structure. The white arrows point to residue precipitated from gas emissions. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 37. The nested cone visible on 28 October had collapsed by 30 October 2016 at Villarrica, and incandescent lava was visible inside the vent. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).

During November and December 2016, steam emissions rose only 400 m above the crater and incandescence was only occasionally visible in the webcams at night. Thermal activity detected by satellite, however, was relatively high; MODVOLC issued twelve thermal alerts during November and nine during December. The repeated growth and destruction of small pyroclastic cones within the summit crater was well documented by several visits of POVI scientists to the summit (figures 38 and 40). They also collected bombs ejected near the crater rim (figure 39), and observed persistent minor ash-and-gas emissions (figure 41).

Figure (see Caption) Figure 38. A new pyroclastic cone grows inside the summit crater of Villarrica on 7 November 2016, days after the collapse of the previous cone on 28 October. Black spatter from lava splashes stand out on the exposed slope. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 39. A piece of ejecta collected at the edges of the summit crater at Villarrica on 9 November 2016. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 40. The pyroclastic cone at the summit crater of Villarrica photographed on 7 November had partially collapsed by 10 November 2016, the same day of the photograph showing a quiet, clear summit (figure 34). The splashes of lava rose no more than 10 m above the crater floor. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).
Figure (see Caption) Figure 41. A small ash emission of rose from the summit of Villarrica on 17 November 2016 around 1050 local time. The larger image was taken by climbers, and the inset images are from the webcam. Courtesy of POVI (Volcán Villarrica, 27 de Octubre al 30 de Noviembre 2016).

Observations by POVI scientists during December 2016 included continued evidence of cone creation and destruction in the vent (figure 42), and small lava fountains (figure 43). Strombolian explosions with bombs were recorded by the webcam on 1, 2, and 3 December. Bombs were ejected more than 50 m above the crater rim, some as large as 1.5 m in diameter. Between 2 and 3 December they observed an 8-10 m drop of the lava in the vent, leaving behind a circular depression with a small incandescent chimney on the NNW side. The webcam captured ash emissions on 2, 14, 15, 18, and 19 December.

Figure (see Caption) Figure 42. The partial collapse of the nested semicircular cone, reported by POVI on 30 November, was evident by 2 December 2016 inside the summit crater of Villarrica. The active vent is about 10-15 m in diameter. On the left wall of the crater the debris of a small recent landslide is visible above the lava. Courtesy of POVI (Informe Preliminar, Comportamiento del Volcán Villarrica, 01 al 31 de Diciembre 2016).
Figure (see Caption) Figure 43. A small Strombolian explosion created a lava fountain inside the summit crater of Villarrica on 8 December 2016. Courtesy of POVI (Informe Preliminar, Comportamiento del Volcán Villarrica, 01 al 31 de Diciembre 2016).

Activity during January-May 2017. OVDAS reported nighttime incandescence and steam emissions less than 250 m high during January 2017. They were higher in February, rising 700 m above the crater rim. Six MODVOLC thermal alerts were issued in January and one in February.

Volcanologists from POVI reported an increase in activity during February (figure 44), including a sudden collapse of about 10 m of much of the material in the lava pit on 9 February, after which a new rise began almost immediately (figure 45). During 10-15 February, explosions from a narrow vent sent lava fountains and ejecta more than 100 m high (figures 46). On 13 February, they witnessed powerful "lava jets" that rose 150 m (figure 47); bombs up to a meter in diameter were ejected 50 m from the vent and spatter covered much of the inner walls of the crater. Between 5 and 26 February, pyroclastic debris raised the level of the bottom of the crater by 10-12 m (figure 48).

Figure (see Caption) Figure 44. An increase in thermal and explosive activity was apparent between 1 and 5 February 2017 at the summit crater of Villarrica. Recently deposited lapilli (L) between 2-64 mm were scattered around the funnel shaped crater on 5 February (right). Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 45. Fresh lava spattered on the inner wall of the summit crater at Villarrica on 11 February 2017, during a new rise in the magma level after a collapse two days earlier. The diameter of the active vent had increased significantly during the previous 24 hours. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 46. Lava fountains exceeded 100 meters above the crater rim at Villarrica on 13 February 2017. Images captured just after midnight show the first explosion (lower right) at 0023 local time, followed two minutes later by the upper image, and another explosion (lower left) about 20 minutes later. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 47. The active vent in the summit crater of Villarrica was about 7 m in diameter on 13 February 2017, and sporadically emitted powerful and noisy "lava jets" more than 150 m high. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).
Figure (see Caption) Figure 48. Between 5 and 26 February 2017, the level of the bottom of the summit crater at Villarrica rose by about 10-12 m. Courtesy of POVI (Volcán Villarrica, Seguimiento Científico de Actividad Volcanánica, 01 al 28 de Febrero 2017).

During March 2017, OVDAS reported steam-and-gas emissions rising 1,000 m. They issued a special report on 23 March indicating an increase in the gas plume height and the occurrence of sporadic explosions of ballistic material that remained within the summit crater. Single MODVOLC thermal alerts were issued on 7 and 14 March 2017.

Nighttime incandescence and steam plumes rising to 550 m characterized activity reported by OVDAS during April 2017. Only a single MODVOLC thermal alert was issued on 4 April. Steam plumes were reported to only 250 m above the crater rim during May along with incandescence at night, but there were seven MODVOLC thermal alerts on four different days; 1 (2), 19 (3), 20, and 29 May.

Activity during June-November 2017. OVDAS reported low levels of activity during June 2017, with incandescence at night and steam plumes rising no higher than 170 m. Only a single MODVOLC thermal alert was issued on 20 June. On a visit to the summit crater on 5 June, POVI scientists observed a 10-m-diameter vent at the bottom of the crater, and lapilli fragments 2-64 mm in diameter distributed around the crater rim. A second visit on 19 June revealed increased explosive activity at the bottom of the crater, ash deposits on the inner walls of the crater, and more lapilli around the mouth of the crater (figure 49). POVI webcams recorded a significant increase in the intensity of incandescence from the summit crater on 24 June 2017 (figure 50).

Figure (see Caption) Figure 49. An increase in explosive activity with respect to that observed on 5 June was noted by POVI scientists on a visit to the summit crater of Villarrica on 19 June 2017. Fresh ash deposits and lapilli appeared on the snow around the crater rim (yellow arrows). Courtesy of POVI (Volcán Villarrica, Resumen del Comportamiento, Observado en Junio 2017).
Figure (see Caption) Figure 50. A significant increase in the intensity of the incandescence emitted from the summit crater at Villarrica was observed in the webcams during the night of 23-24 June 2017. The upper images show the incandescence in the early evening of 23 June, and the lower images were taken just after midnight on 24 June 2017 from the POVI webcam. Courtesy of POVI (Volcán Villarrica, Resumen del Comportamiento, Observado en Junio 2017).

On 1 July 2017, POVI captured a webcam image of Strombolian explosions that sent incandescent material 60 m high from the summit crater. OVDAS reported steam plumes rising no more than 550 m and incandescence at night during July; there were no reported MODVOLC thermal alerts that month, and only a single alert on 30 August. OVDAS reported steam plumes during August rising to 150 m, sporadic ash and larger pyroclastic emissions around the crater rim, and nighttime incandescence.

Activity decreased during September and October 2017, with continued steam emissions rising 300-500 m, minor ash emissions around the crater rim, and nighttime incandescence. Two MODVOLC thermal alerts were issued, on 4 and 16 September, and none during October. POVI scientists visited the summit during October 2017 and noted that the vent remained active, especially after 22 October. They observed that at least half of the inner walls of the crater were covered with fresh ash and lapilli, concentrated on the W, S, and NE sides. They estimated that the active vent was about 8 m in diameter, approximately 100 m down inside the crater (figure 51). The bottom of the crater appeared about 4 m higher than it was on 26 September 2017, and the vent diameter had expanded by 2 m. Ash and lapilli fragments were found around the edge of the crater on 15, 22, and 25 October. Ejections of small fragments of lava were captured by the webcam on 22 and 23 October.

Figure (see Caption) Figure 51. A panoramic image of the summit crater at Villarrica, looking S on 15 October 2017, showed pyroclastic material covering much of the inner surface of the crater wall. The vent was estimated to be about 8 m in diameter, at a depth of 100 m. Courtesy of POVI (Seguimiento y Estudio del Comportamiento, Volcán Villarrica, Octubre 2017).

OVDAS reported that during November 2017, the webcams near the summit showed evidence of low intensity, predominantly white degassing to low altitudes (100 m above the summit). Nighttime incandescence associated with occasional explosions around the crater were typical. They also noted that long-period (LP) seismicity increased in both energy amplitude and frequency during the last few days of the month. A gradual increase in RSAM values began on 15 November with a continuous tremor signal. A 4.1 magnitude event was reported on 24 November located 2.6 km ESE of the summit at a depth of 1.8 km. A single MODVOLC thermal alert was reported on 28 November.

Seismicity and thermal anomalies. Seismicity at Villarrica during October 2016-November 2017 was relatively stable (figure 52), although it varied between about 2,500 and 6,500 events per month, with over 90% recorded as LP events, and only a few VT (volcano-tectonic) events. The highest frequency values occurred in May (5,749) and November 2017 (6,484).

Figure (see Caption) Figure 52. Chart of the frequency of seismic events at Villarrica, October 2016-November 2017. LP are Long-Period events, and VT are Volcano-Tectonic events. Data courtesy of OVDAS, SERNAGEOMIN monthly reports.

Infrared data graphed by the MIROVA system (figure 53) indicated the continuous but decreasing frequency and intensity of thermal anomalies at Villarrica between November 2016 and November 2017.

Figure (see Caption) Figure 53. Infrared data graphed by the MIROVA system indicated the continuous but decreasing frequency and intensity of thermal anomalies at Villarrica between November 2016 and November 2017. Courtesy of MIROVA.

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

Information Contacts: Servicio Nacional de Geología y Minería, (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Proyecto Observación Villarrica Internet (POVI) (URL: http://www.povi.cl/); 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://hotspot.higp.hawaii.edu/; http://modis.higp.hawaii.edu/); 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?lang=es); 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/); Cristian Gonzalez G., flickr (URL:https://www.flickr.com/photos/cg_fotografia/), photo used under Creative Commons license (https://creativecommons.org/licenses/by-nd/2.0/).

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