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Bulletin of the Global Volcanism Network

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

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

Recently Published Bulletin Reports

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).

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Bulletin of the Global Volcanism Network - Volume 32, Number 08 (August 2007)

Managing Editor: Richard Wunderman

Etna (Italy)

Explosive activity and lava fountains during 4-5 September 2007

Karangetang (Indonesia)

Eruptions during mid-2007; evacuations; pyroclastic flows; lava avalanches

Manam (Papua New Guinea)

Mild eruptions and subdued seismicity during August 2006-May 2007

Nyiragongo (DR Congo)

During 2007 the lava lake persists; one death; daily SO2 data stream begins

Pavlof (United States)

Thermal and seismic data presage August 2007 eruption

St. Helens (United States)

Dome growth continues, seismicity remains low

Tungurahua (Ecuador)

During March-July 2007, many lahars; variable eruptive behavior

Turrialba (Costa Rica)

Increased degassing and opening of fissures



Etna (Italy) — August 2007 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Explosive activity and lava fountains during 4-5 September 2007

A report by members of the Istituto Nazionale di Geofisica e Volcanologia di Sezione Catania (INGV-CT), Behncke and Neri (2007), discussed Etna's 4-5 September eruption. On 6 September field work on the eastern zone of the Southeast Crater (SEC) revealed profound morphologic changes. The SEC's eastern pit crater was the source of lava flows.

The erupted material was distributed mostly to the E, covering the plateau between the base of the SEC and the western rim of the Valle del Bove with a thickness ranging from a few meters to more than 25 m (figure 124). The accumulation of welded scoria formed a mound more than 700 m long.

Figure (see Caption) Figure 124. The Southeast Crater cone at Etna seen from the SSE. The white dotted line shows the eruption topography before the 4-5 September 2007 eruption. The photo highlights significant new material over the old topography. From Behncke and Neri (2007).

The scoria mound, which formed by falling material, was composed primarily of extremely light and vesicular scoria, of varying size, from less than a centimeter to meters, oxidized and reddish in color. The thickness of the scoria deposits varied from over 25 m at the base of the SEC to about 8 m in the area around the western rim of the Valle del Bove, behind hornitos at ~ 2,800 m elevation, which formed during the 2006 eruption.

The scoria appeared to have moved after landing. In addition, localized movement also occurred along some wide-opening fracturing.

During the formation of the scoria mound, lava descended as three principal streams. The streams emerged from the SE sector of the eruptive crater (venting at the Eastern pit crater) (figure 125).

Figure (see Caption) Figure 125. Lava flows and pyroclastic materials on the E flank of Etna's Southeast Crater from the 4-5 September 2007 eruption. Labels indicate lithologies. The observer (right) is on the mound of larger scoria, about 150 m from the crater. Photo from Behncke and Neri (2007).

The field observers saw the southern rim of the eruptive crater and the zone beneath it. To an elevation of about 2,800 m, these rocks emitted fumarolic vapors and contained hot fractures. The position of this fissure field appeared to coincide, at least in part, with what had already been identified by thermal telecamera during the helicopter survey carried out by the governmental Regional Civil Protection. Inside the 4-5 September eruptive vent (Eastern pit crater seen in figures 125 and 126), the team also saw a point of continuous and pulsating gas emissions.

Figure (see Caption) Figure 126. At Etna's SEC, this photo shows the degassing vent inside the active crater. Courtesy of INGV.

Reference. Behncke, B. and Neri, M., 2007, L'eruzione del 4-5 settembre 2007 al Cratere di Sud-Est (Etna): osservazioni di terreno in prossimit? della bocca eruttiva; copyrighted report of the INGV-CT (posted on their website and accessed October 2007).

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: Sonia Calvari, Boris Behncke, and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy.


Karangetang (Indonesia) — August 2007 Citation iconCite this Report

Karangetang

Indonesia

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

All times are local (unless otherwise noted)


Eruptions during mid-2007; evacuations; pyroclastic flows; lava avalanches

The previous Bulletin report (BGVN 32:05) discussed periodic activity at Karangetang from January 2004 through April 2007. This report updates activity through August 2007. The island (Ulau Siau, or Siau) has a tear-drop-shape, widest at the N end with the tail bent E. The island's maximum E-W extent is about 10 km.

During April through mid August 2007, the Center of Volcanology and Geological Hazard Mitigation (CVGHM) recorded mild activity with periodic tremor activity registering at 0.5-2 mm and "thick-white-ash" periodically being ejected 25-750 m above the Main crater.

On 25 June 2007, an incandescent explosion 750 m high was observed and a lava avalanche traveled 1,000 m down the to Nawitu river and 400 m down the Bahambang river. Some materials descended into the Batuawang Valley.

Beginning 5 August 2007, the CVGHM recorded tremors with amplitude 4 mm in the vicinity of Karangetang. On 8 August, tremor amplitude increased to 23 mm and a lava fountain rose up to 25-75 m above the summit. Additional lava and pyroclastic flows observed on 10 August prompted authorities to evacuate more than 500 people from villages on the flanks.

On 11 August, because observers witnessed increased eruptive activity, and seismicity included tremors increasing to 46 mm in amplitude, the CVGHM raised the alert status from 2 to 3 (on a scale of 1-4). The alert status was again raised on 18 August from 3 to 4 as the CVGHM reported tremor (45-47 mm amplitude), lava emission, and a debris-flow about 2 km down the S flank. "Booming" noises were also heard and thick ashfall covered villages, farms, and trees on the flanks. Based on these advisories the Darwin Volcanic Ash Advisory Center notified aviation interests of the potential for a major eruption.

On 19 August, Karangetang erupted again several times. An avalanche of lava and hot ash poured down the flanks. Avalanches reportedly reached the coastal villages of Karalung (several kilometers SE of the summit) and Hiung (several kilometers NW of the summit). After 19 August eruptive activity decreased and on 30 August the hazard status was dropped to 3.

Thermal anomalies were detected by MODIS beginning 6-8 August with major activity occurring on 10 August and nearly continuous activity from 13 August through 2 September.

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

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Saut Simatupang, 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Hawai'i Institute of Geophysics and Planetology (HIGP) Hot Spots System, University 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, Northern Territory 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Jakarta Post, Indonesia (URL: http://www.thejakartapost.com/).


Manam (Papua New Guinea) — August 2007 Citation iconCite this Report

Manam

Papua New Guinea

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

All times are local (unless otherwise noted)


Mild eruptions and subdued seismicity during August 2006-May 2007

Our previous Manam report (BGVN 37:04) discussed activity from August 2006 into May 2007. Throughout May and into September 2007, Manam continued to show activity, but the emissions were mild and the seismicity, ever present, was very subdued. The Main Crater continued to release occasional pale gray ash clouds (table 4).

Table 4. Manam activity mid-May into September; the only data source for 17 September is the Darwin VAAC.

Month Vapor Emissions Ash Emissions Thermal Anomalies Incandescence Seismicity (events)
May 2007 25 May (diffuse) 10-16 May (pale gray) 16-23 May 8, 10, 12-13, 29 May 500-1000
Jun 2007 23 Jun -- -- -- 600-1050
Jul 2007 1-4 Jul, 12 Jul (white) 16-17, 22-23, 26-27 Jul (pale gray) -- 4, 7, 12-13, 16-20, 23, 26-27 Jul 600-1050
Aug 2007 8-9 Aug (blue), 10 Aug 21 Aug -- 2-3, 21 Aug 800-1000
Sep 2007 -- 17 Sep -- -- --

Thermal anomalies were detected at Manam by the Moderate Resolution Imaging Spectroradiometer (MODIS) on 16 and 23 May 2007. These anomalies were located down the NE Valley.

On 25 May the Rabaul Volcano Observatory (RVO) reported diffuse plumes from Manam. Based on satellite imagery and information from the Darwin VAAC, these plumes rose to an altitude of 3 km and drifted SW and W.

On those occasions in May where incandescence was visible, area residents heard no noises. The Southern Crater continued releasing diffuse white vapor; however, area residents noted the absence of any noise or glow.

Seismicity throughout May and into early June was low-to-moderate. Through 19 June 2007, low-frequency earthquakes occurred, but no noises were heard. On 23 June, based on satellite observations, the Darwin VAAC reported a low-level eruption that emitted a narrow plume of gas and vapor. It extended 40 km WNW and ascended to an altitude of ~ 3.4 km. The presence of ash was not discernable from the satellite data.

During 1-4 and 12 July 2007, the RVO reported that mild eruptions continued to release occasional diffuse white vapor from Main Crater. Occasional pale gray ash clouds emerged during 16-17, 22-23, and 26-27 July 2007. The ash clouds rose to less than a kilometer above the summit before being blown NW, resulting in fine ashfall. Incandescence was occasionally visible during July. The Southern Crater continued to release diffuse white vapor throughout July with an absence of glow or noise.

Throughout August, Manam continued low level activity. Visual observation of the summit was hampered by clouds most of the time; however, when clear, both craters were releasing primarily thin white vapor. Blue vapor accompanied the white vapor emission from Main Crater on 8-9 August. Based on satellite image observations and information from the RVO, the Darwin VAAC reported that an eruption plume from Manam rose to an altitude of 3 km a.s.l. on 10 August and drifted W. Seismic activity in August remained low and dominated by low-frequency earthquakes. Manam generally lacked significant activity continuing through the end of August and into September 2007. On 17 September, the Darwin VAAC reported that ash plumes from Manam rose to an altitude of 3.7 km a.s.l.

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

Information Contacts: Herman Patia and Steve Saunders, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, Northern Territory 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Hawai'i Institute of Geophysics and Planetology (HIGP) Hot Spots System, University of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/).


Nyiragongo (DR Congo) — August 2007 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


During 2007 the lava lake persists; one death; daily SO2 data stream begins

As has been the case since July 2002, nearly daily thermal anomalies detected by satellite instruments continued through August 2007, confirming the presence of a lava lake in the summit crater. These anomalies were acquired from MODIS satellites and are available on the University of Hawai'i Institute of Geophysics and Planetology (HIGP) MODIS Hotspot Alert website.

The Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Terra satellite recorded a light-colored plume on 19 June 2007 that extended SE over Lake Kivu. NASA suggested that it consisted primarily of water vapor.

Almost daily SO2 concentration-pathlengths for Nyiragongo (figure 37) have been reported online starting in May 2007 by the OMI Sulfur Dioxide Group. The SO2 concentrations are spectroscopically determined primarily by the Ozone Monitoring Instrument (OMI) aboard NASA's Earth Observing System AURA spacecraft. The highest measured amounts were ~ 2.0 Dobson Units or greater on about 20 days during June-September 2007. A Dobson Unit, DU, the product of concentration and pathlength, is a function of the number of SO2 molecules in a unit area of the atmospheric column.

Figure (see Caption) Figure 37. A profile of SO2 concentration-pathlength seen on 23 September 2007 in the Nyiragongo-Nyamuragira area. In this case the plume covered an area of 12,164 km2. Darker (or redder) areas represent greater SO2, as indicated by the legend on the right. The total atmospheric SO2 detected was 465 x 103 kg. Courtesy OMI Sulfur Dioxide Group.

A photo of the summit taken from a fixed-wing aircraft in early July 2007 disclosed that a substantial portion of the outer crater wall on the W flank had collapsed, forming a large slump with an arcuate headwall (figure 38). The implication in the pilot report was that this was a recent event.

Figure (see Caption) Figure 38. A photo taken in early July 2007 by pilot Sean O'Conner as he flew past the W slope of Nyiragongo. The scarp mentioned in the text apparently lies in the center of the field of view. A steam-and-gas plume rises vertically above the crater opening. One of the aircraft's wings juts across the right margin of the photo. Courtesy of Sean O'Conner (ECHO Flight).

According to news media accounts, on 6 July 2007 a female Chinese tourist climbed over the crater rim of Nyiragongo for a photograph of the crater's interior. She slipped and fell more than 100 m down the steep wall of the crater to her death.

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

Information Contacts: NASA Earth Observatory (URL: http://earthobservatory.nasa.gov); OMI Sulfur Dioxide Group, based in the Joint Center for Earth Systems Technology at the University of Maryland Baltimore County (UMBC), and atNASA Goddard Space Flight Center (URL: https://so2.gsfc.nasa.gov/); Hawai'i Institute of Geophysics and Planetology, MODIS Thermal Alert System, School of Ocean and Earth Sciences and Technology (SOEST), University of Hawai'i, 2525 Correa Road, Honolulu, HI, USA (URL: http://modis.higp.hawaii.edu/); Reuters (URL: http://www.reuters.com/); Agence France-Presse (URL: http://www.afp.com/); Sean O'Conner, ECHO (European Commission's Humanitarian Aid Office) Flight, Goma, Democratic Republic of Congo; Tom Pfeiffer, Volcano Discovery (URL: http://www.decadevolcano.net/).


Pavlof (United States) — August 2007 Citation iconCite this Report

Pavlof

United States

55.417°N, 161.894°W; summit elev. 2493 m

All times are local (unless otherwise noted)


Thermal and seismic data presage August 2007 eruption

The Alaska Volcano Observatory (AVO) reported that Pavlof (figure 1) erupted on 15 August 2007 for the first time since 15 September 1996 (BGVN 22:09 and Waythomas, Miller, and Mangan, 2006) . Thermal anomalies and seismic activity just prior to the eruption prompted scientists at AVO to issue a warning. This report covers events reported through 3 October 2007.

Figure (see Caption) Figure 1. Index map showing the location of Pavlof and other Alaska Peninsula volcanoes. Courtesy of AVO and Alaska Division of Geological & Geophysical Surveys.

According to AVO, an abrupt increase in earthquake activity began at Pavlof early on the morning of 14 August 2007. Based on patterns of unrest leading to past eruptions at Pavlof, AVO elevated the alert level and color code to 'Advisory/Yellow.' Observers from the National Oceanic and Atmospheric Administration's (NOAA) National Weather Service (NWS) in Cold Bay, Alaska, were able to see the volcano on the morning of 14 August and reported no anomalous steaming or other activity; satellite imagery from this morning also showed no obvious signs of surface activity or ash emission.

[AVO detected a strong thermal anomaly at the volcano overnight 14-15 September, and seismic activity continued to increase in both the number of events per hour and duration of individual events. Eyewitnesses aboard a ship reported incandescent blocks tumbling down the ESE flank of the volcano beginning at midnight 14 September (the night of 14-15 September). Satellite data confirmed the presence of lava. Pilot reports indicated that a weak ash plume extended 8 km SW of the summit at a height of ~ 2.6 km. Seismic activity continued at a high level. On 15 August AVO raised the aviation color code from Yellow to Orange and the Alert Level from Advisory to Watch.]

Earthquake intensity continued to increase slowly from 15 to 16 August. Strong signals at a single station SE of the summit suggested local flow activity, probably lahars (or mudflows) on that flank. Satellite images of the volcano overnight and during the morning of 16 August continued to show a strong thermal feature (figure 2). Residents of both Cold Bay and Sand Point, Alaska (105 km and 70 km, respectively, from Pavlof), observed incandescence at the summit during the night.

Figure (see Caption) Figure 2. NOAA Advanced Very High Resolution Radiometer (AVHRR) satellite image showing a strong thermal anomaly at the summit of Pavlof on 16 August 2007 at 0750 local time (1550 UTC). In this image, white represents hot temperatures. Courtesy of the AVO/U.S. Geological Survey (USGS).

Persistent earthquake activity and flow events, probably lahars (mudflows), continued on 17 August 2007. Several discrete explosion earthquakes were also recorded. Though clouds obscured the volcano in most satellite images, one GOES (Geostationary Observational Environmental Satellite) image documented a large thermal feature at the summit, interpreted to be lava at the surface.

Activity at Pavlof continued to increase during 17-24 August 2007, with reports that the steam-and-ash plume sometimes exceeded 3 km altitude. For example, a pilot reported the top of the plume to be 5.5 km in the late afternoon of 23 August, and a plume height of 4 km was estimated using satellite data from 1410 that day. Seismic activity remained elevated, with moderate levels of tremor occurring almost continuously and with occasional bursts of higher amplitude. The average seismic amplitude increased slowly throughout the week of 17-24 August. Many small-to-moderate explosions were recorded in the seismic record, as were events from lahars flowing down the SE flank. [Note: Pilot Jeff Linscott of JL Aviation filmed a lahar front on Pavlof's lower flanks before it hit the ocean on 18 August 2007; the film is available on the AVO website, which is listed in under Information Contacts below.] Satellite data showed strong thermal anomalies at the summit, as well as occasional ash clouds, throughout this week.

An AVO field crew visited Pavlof on 18-19 August to make FLIR (forward looking infrared) thermal observations of the ongoing eruption. These observations confirmed the existence of a new vent ~ 200 m below the summit on the SE flank. The vent, ~ 50 m across, fed a lava flow that, on 18 August, was more than 0.5 km long and ~ 25 m across. The crew also observed a lahar reaching the Pacific coast, incandescent lava, and explosions at the vent that sent 5-m-long blocks flying 50 m through the air. Figure 3 shows the plume from Pavlof on 23 August, and figure 4 shows the plume on 30 August 2007.

Figure (see Caption) Figure 3. An Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite image on 23 August 2007 at 2210 UTC showing Pavlof with a small steam-and-ash plume emitting from the crater on the SE side of the summit. The plume in this image (having a resolution of 15 m/pixel) reached an altitude of ~ 4.0 km based on the plume's temperature. Courtesy of the AVO/USGS.
Figure (see Caption) Figure 4. Pavlof volcano and eruption plume on evening of 30 August at 2120 local time. View is to the S, out of the right side of a PenAir Metro Airline plane en route to Anchorage from Cold Bay; plume height was approximately 5.2-5.5 km. Courtesy of Chris Waythomas and AVO/USGS.

At about 2130 local time on 31 August, NOAA/NWS observers in Cold Bay reported a substantial plume emanating from Pavlof, along with associated lightning. The plume, which rose to an altitude of ~ 6 km, was also visible in images from the Pavlof web camera located in Cold Bay. However, there were no indications in satellite data or ground reports of an ash plume. Seismic activity remained elevated through 31 August.

During 1-19 September 2007 the eruption continued; however, seismicity after 10 September declined markedly from levels recorded earlier. AVO pointed out that typical eruptions at Pavlof were characterized by periods of diminished activity interspersed with periods of renewed eruptive activity. Satellite observations continued to show thermal anomalies even through the clouds, as well as steam plumes up to as high as 6.1 km altitude. Table 6 shows thermal anomalies from the beginning of 2007 through 3 October measured by MODIS satellite infrared detectors and processed by the Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System called MODVOLC. Anomalies measured during 2007 began on 15 August and continued through 11 September, after which none have been reported to present (3 October). Satellite thermal anomalies are frequently masked by cloud cover.

Table 6. MODIS/MODVOLC thermal anomalies measured at Pavlof for 15 August-11 September 2007; no anomalies were during 1 January-14 August or 12 September through 3 October. Courtesy of the HIGP Thermal Alerts System.

Date Time (UTC) Number of Pixels Satellite
15 Aug 2007 0750 2 Terra
15 Aug 2007 1330 2 Aqua
16 Aug 2007 0839 3 Terra
16 Aug 2007 1235 1 Aqua
18 Aug 2007 2150 1 Terra
19 Aug 2007 0725 1 Terra
19 Aug 2007 1350 2 Aqua
20 Aug 2007 0810 2 Terra
20 Aug 2007 1210 3 Aqua
20 Aug 2007 1350 1 Aqua
23 Aug 2007 2210 1 Terra
23 Aug 2007 2220 1 Aqua
24 Aug 2007 0745 7 Terra
24 Aug 2007 1325 5 Aqua
25 Aug 2007 1230 7 Aqua
28 Aug 2007 1300 4 Aqua
29 Aug 2007 0800 4 Terra
30 Aug 2007 0705 2 Terra
30 Aug 2007 0845 4 Terra
30 Aug 2007 1250 3 Aqua
31 Aug 2007 0750 3 Terra
31 Aug 2007 1155 2 Aqua
31 Aug 2007 1330 3 Aqua
01 Sep 2007 0830 3 Terra
01 Sep 2007 1235 1 Aqua
02 Sep 2007 0735 1 Terra
02 Sep 2007 0915 4 Terra
02 Sep 2007 1320 4 Aqua
04 Sep 2007 2230 2 Terra
05 Sep 2007 1210 4 Aqua
05 Sep 2007 2135 2 Terra
06 Sep 2007 0715 1 or 2 Terra
06 Sep 2007 0850 8 Terra
06 Sep 2007 1255 5 Aqua
07 Sep 2007 0755 4 Terra
07 Sep 2007 1200 6 Aqua
07 Sep 2007 1335 4 Aqua
08 Sep 2007 0840 1 Terra
09 Sep 2007 0745 2 Terra
09 Sep 2007 2115 1 Terra
09 Sep 2007 2250 1 Terra
09 Sep 2007 2300 2 Aqua
10 Sep 2007 0825 8 Terra
10 Sep 2007 1230 2 Aqua
11 Sep 2007 0910 2 Terra
11 Sep 2007 1315 2 Aqua
11 Sep 2007 2100 2 Terra

A status report on 3 October 2007 stated that "A pause in eruptive activity at Pavlof continues. Seismicity remains at low levels and has been relatively unchanged since about September 13. No sign of renewed volcanic activity was noted in clear satellite and web camera views today." [By 5 October the alert levels were returned to Green and Normal for aviation after more than three weeks without eruptive activity; the eruption was determined to have ended on 13 September 2007.]

References. Waythomas, C.F., Miller, T.P., and Mangan, M.T., 2006, Preliminary Volcano Hazard Assessment for the Emmons Lake Volcanic Center, Alaska: Anchorage, Alaska, U.S. Geological Survey, Scientific Investigations Report 2006-5248, 33 p., 1 sheet (available online at http://www.avo.alaska.edu/pdfs/SIR2006-5248.pdf ).

Linscott, J., 2007, Film of Pavlof lahar front, 18 August 2007 [on AVO website, URL: http://www.avo.alaska.edu/volcanoes/volcimage.php?volcname=Pavlof ).

Geologic Background. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA; Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA; and Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://www.avo.alaska.edu/); Hawai'i Institute of Geophysics and Planetology (HIGP) 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/); Jeff Linscott, JL Aviation Helicopter Service, 8015 NE Airport Way, Portland, OR 97218 USA.


St. Helens (United States) — August 2007 Citation iconCite this Report

St. Helens

United States

46.2°N, 122.18°W; summit elev. 2549 m

All times are local (unless otherwise noted)


Dome growth continues, seismicity remains low

Lava dome growth at St. Helens (as previously reported in BGVN 31:12) continued through at least September 2007. Seismicity remained at low levels punctuated by M 1.5-2.5, and occasionally larger, earthquakes. Inclement weather inhibited field work and created poor visibility for much of the January-September reporting period.

In general, gas-and-steam plumes from the active lava dome, as well as dust plumes resulting from rockfalls, occasionally rose above the crater rim. A gas plume may have been seen on 3 June, and a weak gas-and-steam plume was visible rising from the lava dome on 12 June.

On 3 April, a GPS unit on an active spine showed W-ward movement at a rate of approximately 30 cm/day. Points on the active part of the dome moved away from the vent at an average rate of approximately 0.45m/day July 2007. That rate is similar to but slightly less than it was a year ago.

Growth of the lava dome and changes in crater morphology over the course of this eruption have been well documented (figures 69 and 70).

Figure (see Caption) Figure 69. A panoramic wide-angle view from St. Helens' crater rim looking N on 27 July 2006. The accompanying sketch describes key features in the photo. For example, the dark rim wrapping around the lower margin of the photo represents rock debris on the snow cornice. Courtesy of Willie Scott, USGS Cascades Volcano Observatory.
Figure (see Caption) Figure 70. Comparison photo taken of Mount St. Helens as seen from Harrys Ridge, 8 km N. These photos were taken 25 years apart in 19 May 1982 and 20 April 2007. Courtesy of Gene Iwatsubo, USGS CVO.

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

Information Contacts: Cascades Volcano Observatory (CVO), U.S. Geological Survey, 1300 SE Cardinal Court, Building 10, Suite 100, Vancouver, WA 98683-9589, USA (URL: https://volcanoes.usgs.gov/observatories/cvo/).


Tungurahua (Ecuador) — August 2007 Citation iconCite this Report

Tungurahua

Ecuador

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

All times are local (unless otherwise noted)


During March-July 2007, many lahars; variable eruptive behavior

Ecuador's Instituto Geofisico (IG) wrote that significant though variable eruptions and lahars occurred at Tungurahua during mid-2007. Our previous report (BGVN 32:04) focused on early January to 2 March 2007, noting some variations in the pace of eruptive activity then. This report summarizes IG reports for March-July 2007. The substantial eruptions of July and August 2006 left abundant pyroclastic-flow deposits on the mountains slopes, potential source materials for new lahars (mudflows). The abundant seismicity during that interval punctuated a longer-term variable pattern (table 13 and figure 38).

Table 13. Summary of Tungurahua seismicity recorded during July 2006 through Mar 2007. Courtesy of IG.

Time interval Total earthquakes Long-period Volcano-tectonic Hybrid Emission signals Explosion signals
Total for Jul 2006 3482 3475 5 2 1185 6442
Daily avg Jul 2006 112 112 0.16 0.06 38 208
Total for Aug 2006 2546 2518 19 9 467 1643
Daily avg Aug 2006 82.1 81.2 0.61 0.29 15.1 53.0
Total for Sep 2006 2189 2149 35 5 111 0
Daily avg Sep 2006 73.0 71.6 1.16 0.16 3.7 0
Total for Oct 2006 3159 3131 20 8 1023 4
Daily avg Oct 2006 102 101 0.64 0.25 33.0 0.12
Total for Nov 2006 1849 1846 3 0 1049 1
Daily avg Nov 2006 61.6 61.5 0.1 0 35.0 0.03
Total for Dec 2006 2172 2168 5 0 648 0
Daily avg Dec 2006 70.1 69.9 0.16 0 22.8 0
Total for Jan 2007 829 817 12 0 10 0
Daily avg Jan 2007 26.7 26.4 0.38 0 0.32 0
Total for Feb 2007 983 966 15 2 312 54
Daily avg Feb 2007 35.1 34.5 0.53 0.07 11.1 1.9
Total for Mar 2007 1126 1125 1 0 1215 334
Daily avg Mar 2007 36.3 36.3 0.03 0 39.2 10.7
 
26 Feb-04 Mar 2007 427 427 0 0 364 51
05 Mar-11 Mar 2007 235 235 0 0 269 87
12 Mar-18 Mar 2007 134 133 1 0 203 112
19 Mar-25 Mar 2007 241 241 0 0 356 86
26 Mar-01 Apr 2007 465 465 0 0 300 47
Figure (see Caption) Figure 38. Tungurahua seismicity during September 1999 to March 2007 plotting the number of both explosion (EXP) and long-period (LP) earthquakes. Other kinds of earthquakes also took place but after 2001 were rarely seen. Courtesy of IG.

The IG report for March stated that a relatively energetic eruptive phase began on 24 February 2007 and continued throughout the month. That phase included abundant, ash emissions, sometimes discharging incandescent material, numerous, sometimes large explosions, and frequent noteworthy ashfall. The ash emissions and ashfalls were sometimes sustained. Blocks ejected in Strombolian outbursts fell up to 1 km below the crater rim.

During March, there were rises in both tremor amplitude and the number of long-period (LP) earthquakes (the later during March averaging 36 per day). SO2 gas fluxes averaged ~ 1,050 metric tons/day (t/d). Flank deformation was minimal. March ash falls came from frequent sustained ash plumes 2-6 km over the summit (figure 39). Seismically detected eruptions took place 29 times per day, including some of large size. Tremor nominally took place around 1 Hz, but its frequency remained irregular, non-harmonic, and pulsating. Intervals of pulsing emissions in mid-March had cycle times of ~ 10 minutes.

Figure (see Caption) Figure 39. Tungurahua emitting an ash plume on 9 March 2007. Sustained plumes were seen during much of the month. Photo taken from Pondoa, on the N flank by Patty Mothes (IG).

An explosion on 27 March caused an "overflow" of incandescent material that traveled 800 m down from the head of the Mandur drainage. Other similar eruptions may have occurred but cloudy conditions forestalled clear observations. Hot lahars, however, traveled down the Mandur and Chontapampa drainages. Ash falls were common on the cone's N and NW sectors, and in addition, observers noted a small pyroclastic flow.

During the first weeks of April 2007 the IG noted continuous, strong emissions with a very high ash content. These emissions accompanied conspicuous lava fountains, visible at night, and strong roars that made windows vibrate. Ash columns reached 6 km above the crater (~ 11 km altitude). Activity decreased notably during the last 10 days of April (but were even lower in late May). Seismometers recorded an average of ~ 10 daily low-amplitude LP earthquakes. A differential optical absorption spectroscopy (DOAS) instrument measured SO2 fluxes of 3,600 and 3,700 t/d during the last 10 days of April.

During May, seismicity was low (table 13), with the average number of registered earthquakes each day averaging about 20. The Seismic Activity Index at the beginning of the month indicated a level 5 (moderate-high activity), which later on fell to a level 3 (moderate-low activity). This was the lowest Seismic Activity Index registered since February 2007. Ash emissions were low to moderate with a westerly direction. The SO2 levels were approximately 800 t/d. With the exception of the frequent formation of lahars, the level of volcanic activity was low in May.

The vigor of June 2007 eruptions from Tungurahua remained at moderate to low levels. Seismicity at the start of the month was low, chiefly LP earthquakes. Eruptions columns were modest and charged with moderate to low amounts of ash. June SO2 fluxes were comparatively high, ~ 2,900 t/d; observers heard light roaring noises similar to a turbine engine. Seismicity increased slightly towards the end of the month.

June brought prolonged intervals of low intensity rain, but heavy rains also occurred. The result was lahars (mud flows) that were numerous and in some cases large (table 14). The 21st of June was particularly noteworthy (table 14). Figure 40 shows one such lahar, which was partly eroded resulting in extension of lahars farther downslope. The lahars sometimes closed the route along the N side of the volcano between Baños and Pelileo and also the route from Baños around the volcano's W flank to Penipe (~ 15 km SW of the summit). No fatalities were reported.

Table 14. List of Tungurahua's main lahars during June 2007. A map and table of Tungurahua drainages (quebradas) appeared previously (BGVN 29:01). Courtesy of IG.

Date Drainage Relative size and comments
01 Jun 2007 Bilbao Small
 
06 Jun 2007 Bilbao Small
 
07 Jun 2007 Vazcun Small
07 Jun 2007 La Pampa Small; caused road closure
07 Jun 2007 Bilbao Small
07 Jun 2007 Motilones Small
07 Jun 2007 Pingullo Small
07 Jun 2007 Rea Small
07 Jun 2007 Viejo Minero Muddy water
 
11 Jun 2007 Mandur Muddy water
11 Jun 2007 La Pampa Small
 
12 Jun 2007 La Pampa Muddy water
12 Jun 2007 Viejo Minero Muddy water
 
13 Jun 2007 La Pampa (2) Large and medium; a truck remained stuck
13 Jun 2007 Viejo Minero Muddy water
 
14 Jun 2007 Mandur Small
14 Jun 2007 La Pampa Small
14 Jun 2007 Bilbao Small
14 Jun 2007 Pingullo Small
14 Jun 2007 Motilones Small
 
15 Jun 2007 Mandur Small
15 Jun 2007 Mapayacu Small
15 Jun 2007 Motilones Small
15 Jun 2007 Pingullo Small
15 Jun 2007 La Pampa Small
15 Jun 2007 Rea Small
15 Jun 2007 Choglontus Small
15 Jun 2007 Cusua Small
15 Jun 2007 Vazcun Small
15 Jun 2007 Viejo Minero Muddy water
 
16 Jun 2007 La Pampa Muddy water
 
20 Jun 2007 La Pampa Medium; closing the road
20 Jun 2007 Mandur Small
20 Jun 2007 Viejo Minero Small
20 Jun 2007 Achupashal Small
20 Jun 2007 Bilbao Small
20 Jun 2007 Motilones Small
 
21 Jun 2007 La Pampa Large, closing the road
21 Jun 2007 Viejo Minero Large
21 Jun 2007 Mandur Large
21 Jun 2007 Vazcun Large
21 Jun 2007 Nueva Cusua Large
21 Jun 2007 Achupashal Large
21 Jun 2007 Motilones Large
21 Jun 2007 Pingullo Large
21 Jun 2007 Bilbao Large
21 Jun 2007 Rea Large
21 Jun 2007 Confesionario Large
21 Jun 2007 Ulba Growing
 
22 Jun 2007 Vazcun Growing
22 Jun 2007 Ulba Growing
22 Jun 2007 La Pampa Muddy water
22 Jun 2007 Viejo Minero Small
22 Jun 2007 Mandur Small
 
24 Jun 2007 La Pampa Muddy water
Figure (see Caption) Figure 40. A lahar in the La Pampa sector of Tungurahua showing an active, steep sided erosional channel down the axis of the deposit. Photographed 13 June 2007 by P. Ramón (IG). Courtesy IG.

There was a minor increase in seismicity during the month of July. Distribution of events was variable: 240-330 events per week the first and last week of the month; 50-70 events during each of the other two weeks. They were primarily LPs ~ 2 km below the summit.

The rate of SO2 emission averaged 1,071 t/d with a high of 2,050 t/d. Ashfall was semi-continuous, reaching areas W and SW of the summit, near communities like Bilbao (8 km W of the summit), Chogluntus (SSW of the summit), and El Manzano (7 km WSW). The plume headed toward Manta once the column reached 4 km above the summit.

During July, the road to Baños-Las Juntas was temporarily closed six times due to small-to-moderate lahars.

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: Geophysical Institute (IG), Escuela Politécnica Nacional, Apartado 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec/).


Turrialba (Costa Rica) — August 2007 Citation iconCite this Report

Turrialba

Costa Rica

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

All times are local (unless otherwise noted)


Increased degassing and opening of fissures

Non-eruptive fumarolic activity was reported at Turrialba through August 2001 (BGVN 26:11). This report covers the time interval January 2002 to mid-2007. Central and W craters were both scenes of fumarolic activity, and reports mentioned generally modest seismicity.

No eruption occurred, although fumarolic and seismic activity remained elevated and some other noteworthy changes also took place. Figure 6 presents a summary of seismicity measured during 1990-2006. Seismicity increased beginning in 1996, reached a peak in 2001 and although it remained elevated, it decreased somewhat from the peak through 2006. In general seismic activity was modest and of short duration with numerous micro-earthquakes of amplitude smaller than 15 mm, and frequencies between 2.1 and 3.0 Hertz (Hz).

Figure (see Caption) Figure 6. The numbers of earthquakes recorded at Turrialba during 1990 through 2006. Courtesy of Vilma Barboza (OVSICORI-UNA ).

Fumarolic activity of 2002-2006. A summary of fumarolic activity at the central crater during the period 2002 through 2006 indicated the S, SW, NW, and N walls were collecting sulfur as a product of gas emissions. Monthly vapor temperatures at the central crater ranged from 87 to 91°C. In March 2006, a pair of cracks continued to be visible in the central crater's S, SE, and SW walls. By August 2006, a pair of cracks in the central crater were particularly significant. Visiting scientists noted that during August 2006, localized vegetation in and around the summit area had been heavily impacted by gases. Areas not affected by increased fumarolic activity in June 2005 had been burned, including a tree belt on the NW outer flank. Below the tree belt, farmers reported an intensification of gas odors. The shapes of the burned areas reflected prevailing wind directions.

From 2002 through 2006, Turrialba's W crater displayed fumarolic activity in the N, NE, W, NW, and SW sides with low levels of emission and gas temperatures remaining consistent from 88 to 93°C . New points of sulfur deposition were noted throughout the period.

An interval of increased seismicity (a pulse) recorded by station VTU located 0.5 km NE of the active crater occurred during 9 July to 14 September 2003. Through December 2003, the emissions continued to increase in the main crater, gradually generating gas columns that were carried W. Observers noted that the vegetation of the SW wall and W of the central crater continued to deteriorate, as well as effects such as heating of the ground, salt deposition at the surface, and escaping gases.

In June 2005, a significant increase in fumarolic gas emission was noted by OVISCORI-UNA and they also indicated changes in gases venting at the W crater. Chemical analysis indicated carbon dioxide gas had decreased and sulfur dioxide had increased, with the result that bushy species and minor plants that managed to survive in the open summit area (inner walls) became completely burned (figure 7). In the external walls to the N, NW, and W, the gases killed the vegetation.

Figure (see Caption) Figure 7. Increased degassing and resultant burned vegetation around Turrialba's W crater, as illustrated in this photograph from June 2005. Courtesy Eliécer Duarte, OVISCORI-UNA.

A 2006 report noted that bushy species and minor plants that had previously managed to survive in the open summit area (inner walls) had by August 2006 appeared completely burned (figure 8). The tree belt on the NW outer flanks (reported in 2005 as partially burned) contained a significant percentage of dead birch (Alnus acuminata). The belt, ~ 200 x 900 m in area, included species taller than 25 m, and was visible from the lower inhabited farms where residents reported increasingly potent gas odors. The shape and location of the belt correlated with the seasonal prevailing wind directions.

Figure (see Caption) Figure 8. Aerial photograph depicting vegetation impacts at Turrialba and to its W, emphasizing zones affected by increased gas emissions from June 2005 through August 2006. Spanish labels translate as follows: 1) Coyote habitat, 2) Inhabited farms, 3) Area of partial deforestation, 4) Area of totally killed vegetation, 5) W crater, and 6) Central crater. Courtesy E. Duarte, OVISCORI-UNA.

Behavior during January-August 2007. At the end of February 2007, a flight over Turrialba's summit revealed significant growth in the area of burned vegetation. On that day, dwarf and tall trees looked yellowish due to sustained degassing from the W crater.

On 21 April, observers measured the temperatures of fumaroles emitting steam at ~ 40°C as far as 1.5 km SW of the summit, a spot coinciding with the well known, ENE-trending Ariete fault. Two larger fumaroles were reported on 2 May located 200 m SW from the first one along the same fault. This site released significant vapor plumes (~ 90°C) that rose above the thick forest.

During June and July 2007, enhanced fumarolic activity was accompanied by new fractures at the summit. The fumaroles spread over a larger area and their temperatures increased to ~ 90°C. Micro-seismicity also grew.

The main fumarole at the bottom of W crater reached 138°C producing a distinctive sound similar to a high pressure valve; this sound could be heard up to ~ 500 m away. These fumaroles had melted sulfur, a phenomenon previously not seen in OVISCORI's more than 25 years continuous monitoring. Sulfur condensate colored most of the inner crater walls with a fine yellowish film.

Besides the multiple cracks associated with the expansion of the fumarolic areas around the W crater, two new ones appeared. Such cracks (longer than 100 m) oriented radially from the volcano's W and NW borders suggested a significant degree of summit instability. A wide fumarolic field between these two fractures along with the large number of vapor and gas spots on the outer walls also reflected considerable permeability in that area (figure 9).

Figure (see Caption) Figure 9. The three fumarolic fields and their associated cracks on Turrialba's NW outer wall, as seen 10 August 2007. Fumaroles are indicated by patten of white lines; cracks ("grietas") indicated by rows of dots. From left to right, the three fields are associated with cracks aligned approximately NW-SE, W-E, and S-N. The latter site contains two N-trending cracks adjacent new fumaroles. Courtesy OVISCORI-UNA.

The effect of gases on the surrounding vegetation (in a 4-km radius) expanded to areas previously protected from damage by prevailing winds (figures 10-11). Acute chemical burning of important patches of natural forest had occurred. Vegetation to the NW, W, and SW appeared yellowish to dark brown (figure 10). By mid-2007 some of the effects had reached potato fields and dairy pastures.

Figure (see Caption) Figure 10. Acute effects of gases on vegetation are easily visible on Turrialba's steep NW outer wall (25 July 2007). Burns on leaf tissue diminish with distance from the source. Zones of dead climbing vines are visible at closest range in the photo's lower right corner. Courtesy OVISCORI-UNA.
Figure (see Caption) Figure 11. Despite the rainy season at Turrialba, the impact of volcanic gases on both exotic and native vegetation increased during June and July 2007. This 27 July 2007 photo identifies three zones of chemical burning, efectos agudo (acute effects), efectos intermedios (intermediate effects), and efectos menores (minor effects). Courtesy E. Duarte, OVISCORI-UNA.

On 5 September 2007, OVSICORI-UNA visited Turrialba's outer NW wall to document the gas damage to vegetation in the area from the crater to the seismic station PICA, a distance of 2.5 km. The observers found three bands of severe damage: across an upslope area, a forested zone, and dairy-farm fields.

The upslope band contained a smaller, dense zone of sparse, dwarfed, woody bushes abutting the forest in a fine loose soil in steep terrain. Plants here were very dry and showed a surface layer of white-yellowish material. This effect was most intense within 100 m of the crater, but still partly visible up to 400 m away in patches. A second section with very dense growth was dead.

The mid-slope band through primary forest contained several tree species, including Jaúl and oak. Although all the trees in portions of this band had apparently died, they did so episodically with varying species seemingly more or less resistant to volcanic gases. The upper parts of the trees showed the greatest visible changes. Among the other plant species killed was a climbing vine that where killed turned an intense coffee color.

The topographically lowest band, consisting of pastures with occasional trees, had burned completely over a zone 400 m from the lower line of the forest, leaving grasses a straw-yellow color, and sufficiently brittle to be easily broken by contact. Gasses had also strongly corroded relatively new barbed wire in the ESE sector, and in lower parts of this zone they reacted with fixtures on buildings and damaged gardens.

The August 2007 OVSICORI-UNA report described ongoing fumarolic activity at Turrialba. At the Central and W craters, the respective maximum temperatures were 91°C and 176°C (up from 138°C during late July). Deposition at the fumaroles included sulfur and sulfurous sublimates, in some cases draping walls and forming minor flows up to 2 m from the point of emission. Small landslides were apparent on many sides of the W crater's walls, and these too were places where sulfur or sulfurous sublimates were seen. One of two major fracture directions trended SW; it was visible as a crack 100 m in length and underwent a maximum opening of 1 to 3 cm between 28 July and 16 August.

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: Eliécer Duarte, Erick Fernández, and Vilma Barboza, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apdo. 2346-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Francois Robichaud, Université de Sherbrooke, 2500 boul. de l'Université, Sherbrooke, Québec J1K 2R1, Canada.

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