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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

Merapi (Indonesia) Eruptions in April and June 2020 produced ash plumes and ashfall

Semeru (Indonesia) Ash plumes, lava flows, avalanches, and pyroclastic flows during March-August 2020

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



Merapi (Indonesia) — October 2020 Citation iconCite this Report

Merapi

Indonesia

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

All times are local (unless otherwise noted)


Eruptions in April and June 2020 produced ash plumes and ashfall

Merapi, located just north of the city of Yogyakarta, Indonesia, is a highly active stratovolcano; the current eruption began in May 2018. Volcanism has recently been characterized by lava dome growth and collapse, small block-and-ash flows, explosions, ash plumes, ashfall, and pyroclastic flows (BGVN 44:10 and 45:04). Activity has recently consisted of three large eruptions in April and June, producing dense gray ash plumes and ashfall in June. Dominantly, white gas-and-steam emissions have been reported during April-September 2020. The primary reporting source of activity comes from Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG, the Center for Research and Development of Geological Disaster Technology, a branch of PVMBG), the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), and the Darwin Volcanic Ash Advisory Centre (VAAC).

Activity at Merapi dominantly consisted of frequent white gas-and-steam emissions that generally rose 20-600 m above the crater (figure 95). On 2 April an eruption occurred at 1510, producing a gray ash plume that rose 3 km above the crater, and accompanied by white gas-and-steam emissions up to 600 m above the crater. A second explosion on 10 April at 0910 generated a gray ash plume rising 3 km above the crater and drifting NW, accompanied by white gas-and-steam emissions rising 300 m above the crater (figure 96). Activity over the next six weeks consisted primarily of gas-and-steam emissions.

Figure (see Caption) Figure 95. Gas-and-steam emissions were frequently observed rising from Merapi as seen on 3 April (left) and 4 August (right) 2020. Courtesy of BPPTKG.
Figure (see Caption) Figure 96. Webcam image showed an ash plume rising 3 km above the crater of Merapi at 0917 on 10 April 2020. Courtesy of BPPTKG and MAGMA Indonesia.

On 8 June PVMBG reported an increase in seismicity. Aerial photos from 13 June taken using drones were used to measure the lava dome, which had decreased in volume to 200,000 m3, compared to measurements from 19 February 2020 (291,000 m3). On 21 June two explosions were recorded at 0913 and 0927; the first explosion lasted less than six minutes while the second was less than two minutes. A dense, gray ash plume reached 6 km above the crater drifting S, W, and SW according to the Darwin VAAC notice and CCTV station (figure 97), which resulted in ashfall in the districts of Magelang, Kulonprogo, and as far as the Girimulyo District (45 km). During 21-22 June the gas-and-steam emissions rose to a maximum height of 6 km above the crater. The morphology of the summit crater had slightly changed by 22 June. Based on photos from the Ngepos Post, about 19,000 m3 of material had been removed from the SW part of the summit, likely near or as part of the crater rim. On 11 and 26 July new measurements of the lava dome were taken, measuring 200,000 m3 on both days, based on aerial photos using drones. Gas-and-steam emissions continued through September.

Figure (see Caption) Figure 97. Webcam image showed an ash plume rising 6 km above the crater of Merapi at 0915 on 21 June 2020. Courtesy of BPPTKG.

Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2,000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequent growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities.

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


Semeru (Indonesia) — October 2020 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Ash plumes, lava flows, avalanches, and pyroclastic flows during March-August 2020

Semeru in eastern Java, Indonesia, has been erupting almost continuously since 1967 and is characterized by ash plumes, pyroclastic flows, lava flows and lava avalanches down drainages on the SE flanks. The Alert Level has remained at 2 (on a scale of 1-4) since May 2012, and the public reminded to stay outside of the general 1-km radius from the summit and 4 km on the SSE flank. This report updates volcanic activity from March to August 2020, using primary information from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), the Darwin Volcanic Ash Advisory Centre (VAAC), and satellite data.

Activity at Semeru consisted of dominantly dense white-gray ash plumes rising 100-600 m above the crater, incandescent material that was ejected 10-50 m high and descended 300-2,000 from the summit crater, and lava flows measuring 500-1,000 m long. Two pyroclastic flows were also observed, extending 2.3 km from the summit crater in March and 2 km on 17 April.

During 1-2 March gray ash plumes rose 200-500 m above the crater, accompanied by incandescent material that was ejected 10-50 m above the Jonggring-Seloko Crater. Lava flows reaching 500-1,000 m long traveled down the Kembar, Bang, and Kobokan drainages on the S flank. During 4-10 March ash plumes up to 200 m high were interspersed with 100-m-high white gas-and-steam plumes. At the end of a 750-m-long lava flow on the S flank, a pyroclastic flow that lasted 9 minutes traveled as far as 2.3 km. During 25-31 March incandescent material found at the end of the lava flow descended 700-950 m from the summit crater (figure 42).

Figure (see Caption) Figure 42. Sentinel-2 thermal satellite imagery showed lava avalanches descending the SSE flank on 26 March 2020. Images using short-wave infrared (SWIR, bands 12, 8A, 4) rendering; courtesy of Sentinel Hub Playground.

Incandescent material continued to be observed in April, rising 10-50 m above the Jonggring-Seloko Crater. Some incandescent material descended from the ends of lava flows as far as 700-2,000 m from the summit crater. Dense white-gray ash plumes rose 100-600 m above the crater drifting N, SE, and SW. During 15-21 April incandescent lava flows traveled 500-1,000 m down the Kembar, Bang, and Kobokan drainages on the S flank. On 17 April at 0608 a pyroclastic flow was observed on the S flank in the Bang drainage measuring 2 km (figure 43). During 22-28 April lava blocks traveled 300 m from the end of lava flows in the Kembar drainage.

Figure (see Caption) Figure 43. A pyroclastic flow at Semeru on 17 April 2020 moving down the S flank toward Besuk Bang. Photo has been color corrected. Courtesy of PVMBG.

Similar activity continued in May, with incandescent material from lava flows in the Kembar and Kobokan drainages descending a maximum distance of 2 km during 29 April-12 May, and 200-1,200 m in the Kembar drainage during 13-27 May, accompanied by dense white-gray ash plumes rising 100-500 m above the crater drifting in different directions. White gas-and-steam plumes rose 300 m above the crater on 26-27 May. Dense white-to-gray ash plumes were visible most days during June, rising 100-500 m above the crater and drifting in various directions. During 3-9 June incandescent material from lava flows descended 200-1,600 m in the Kembar drainage.

Activity in July had decreased slightly and consisted of primarily dense white-gray ash plumes that ranged from 200-500 m above the crater and drifted W, SW, N, and S. Weather conditions often prevented visual observations. On 7 July an ash plume at 0633 rose 400 m drifting W. Similar ash activity was observed in August rising 200-500 m above the crater. On 14 and 16 August a Darwin VAAC advisory stated that white-gray ash plumes rose 300-400 m above the crater, drifting W and WSW; on 16 August a thermal anomaly was observed in satellite imagery. MAGMA Indonesia reported ash plumes were visible during 19-31 August and rose 200-400 m above the crater, drifting S and SW.

Hotspots were recorded by MODVOLC on 11, 6, and 7 days during March, April, and May, respectively, with as many as four pixels in March. Thermal activity decreased to a single hotspot in July and none in August. The MIROVA (Middle InfraRed Observation of Volcanic Activity) system recorded numerous thermal anomalies at the volcano during March-July; a lower number was recorded during August (figure 44). The NASA Global Sulfur Dioxide page showed high levels of sulfur dioxide above or near Semeru on 18, 24-25, and 29-31 March, and 9 April.

Figure (see Caption) Figure 44. Thermal anomalies at Semeru detected during March-June 2020. Courtesy of MIROVA.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia (Multiplatform Application for Geohazard Mitigation and Assessment in Indonesia), PVMBG, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


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/).

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Bulletin of the Global Volcanism Network - Volume 43, Number 09 (September 2018)

Managing Editor: Edward Venzke

Alaid (Russia)

Small ash plume reported on 21 August 2018

Fournaise, Piton de la (France)

One-day eruptive events in April and July; 5-week eruption 27 April-1 June 2018

Great Sitkin (United States)

Small phreatic explosions in June and August 2018; ash deposit on snow near summit

Negra, Sierra (Ecuador)

Fissure opens on NNE caldera rim 26 June 2018, NW-flank lava flows reach the sea

Nishinoshima (Japan)

Quiescence interrupted by brief lava flow emission and small explosions in July 2018

Rincon de la Vieja (Costa Rica)

Intermittent weak phreatic explosions during January-March and July-August 2018

Semeru (Indonesia)

Small ash plumes in February, April, July, and August 2018; persistent thermal hotspot in the crater

Sinabung (Indonesia)

No significant ash plumes seen after 22 June 2018; minor ash in early July

Telica (Nicaragua)

Explosions on 21 June and 15 August 2018; local ashfall from June event

Turrialba (Costa Rica)

Ongoing variable ash emissions and crater incandescence through August 2018



Alaid (Russia) — September 2018 Citation iconCite this Report

Alaid

Russia

50.861°N, 155.565°E; summit elev. 2285 m

All times are local (unless otherwise noted)


Small ash plume reported on 21 August 2018

Sporadic ash and gas-and-ash plumes and strong thermal anomalies were reported from Alaid, in Russia's Kurile Islands, between 29 September 2015 and 30 September 2016 (figure 8). The Kamchatka Volcanic Eruptions Response Team (KVERT), which monitors the volcano, interpreted the thermal anomalies as Strombolian activity and a lava flow (BGVN 42:04). The current report summarizes activity during October 2016 through August 2018.

Figure (see Caption) Figure 8. Aerial photo of the Alaid summit area on 28 April 2016, with fresh lava filling the crater, a cinder cone in the southern part of the crater, and a lava flow on the SW flank. Photo by L. Fugura; courtesy of IVS FEB RAS, KVERT.

According to KVERT weekly reports, the Aviation Color Code for Alaid was Green (Volcano is in normal, non-eruptive state) throughout the reporting period. The only reported activity was from the Tokyo Volcanic Ash Advisory Center, which reported that on 21 August 2018, an ash plume identified in Himawari-8 satellite images rose to an altitude of 2.7 km (about 500 m above the summit) and drifted SE. The plume was clearly visible on imagery starting at 0830 Japan Standard Time (UTC + 9 hours), and remained noticeable for at least 4 hours. There were no other satellite or ground-based observations of this activity.

Figure (see Caption) Figure 9. Himawari-8 satellite image from 21 August 2018 at 1030 JST (UTC + 9 hours) showing a small ash plume drifting SE from Alaid towards Paramushir Island. Alaid is the small island NW of the larger Paramushi Island and directly W of the southern tip of the Kamchatka Peninsula. Courtesy of Himawari-8 Real-time Web.

Geologic Background. The highest and northernmost volcano of the Kuril Islands, 2285-m-high Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached widely to the south. Alaid is the northernmost of a chain of volcanoes constructed west of the main Kuril archipelago. Numerous pyroclastic cones dot the lower flanks of this basaltic to basaltic-andesite volcano, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest in the Kuril Islands during historical time.

Information Contacts: Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Himawari-8 Real-time Web, developed by the NICT Science Cloud project in NICT (National Institute of Information and Communications Technology), Japan, in collaboration with JMA (Japan Meteorological Agency) and CEReS (Center of Environmental Remote Sensing, Chiba University) (URL: https://himawari8.nict.go.jp/).


Piton de la Fournaise (France) — September 2018 Citation iconCite this Report

Piton de la Fournaise

France

21.244°S, 55.708°E; summit elev. 2632 m

All times are local (unless otherwise noted)


One-day eruptive events in April and July; 5-week eruption 27 April-1 June 2018

Short pulses of intermittent eruptive activity have characterized Piton de la Fournaise, the large basaltic shield volcano on Reunion Island in the western Indian Ocean, for several thousand years. The most recent episode occurred during 14 July-28 August 2017 with a 450-m-long fissure on the S flank inside the Enclos Fouqué caldera about 850 m W of Château Fort. Three eruptive episodes occurred during March-August 2018, the period covered in this report; two lasted for one day each on the N flank in April and July, and one lasting from late April through May located on the S flank. Information is provided primarily by the Observatoire Volcanologique du Piton de la Fournaise (OVPF) as well as satellite instruments.

The first of three eruptive events during March-August 2018 occurred during 3-4 April and was a 1-km-long fissure that opened in seven segments with two eruptive vents. It was located on the N flank of the central cone, just S of the Nez Coupé de Sainte Rose on the rim of the caldera. A longer lasting eruptive event began on 27 April and was located in the cratère Rivals area on the S flank of the central cone. The main fissure had three eruptive vents initially, only one of which produced lava that flowed in tunnels away from the site toward the S rim of the Enclos Fouqué caldera. The longest flow reached 3 km in length and set fires at the base of the rampart rim of the caldera. Flow activity gradually decreased throughout May, and seismic tremor ceased, indicating the end of the event, on 1 June 2018. A third, brief event on 13 July 2018 produced four fissures with 20-m-high incandescent lava and aa flows that traveled several hundred meters across the NNW flank of the central cone, covering a large section of the most popular hiking trail to the summit. The event only lasted for about 18 hours but caused significant geomorphologic change as the first flow activity in that area in several hundred years.

The MIROVA plot of thermal energy from 6 February-1 September 2018 clearly shows two of the three eruptive events that took place during that period. The 27 April to 1 June event produced an initial very strong thermal signature that decreased throughout May. Cooling after the flow ceased continued for most of June. The one-day eruptive event on 13 July was also recorded, but the similarly brief event on 3-4 April was not captured in the thermal data (figure 126).

Figure (see Caption) Figure 126. The MIROVA plot of thermal energy from Piton de La Fournaise from 6 February-1 September 2018 clearly shows two of the three eruptive events that took place during that period. The longest event, from 27 April to 1 June produced an initial very strong thermal signature that decreased throughout May. Cooling after the flow ceased continued for most of June. A brief one-day eruptive event on 13 July was also recorded. A similarly brief event on 3-4 April was not recorded. Courtesy of MIROVA.

Eruptive event of 3-4 April 2018. Minor inflation and seismicity were intermittent from the end of August 2017 when the last eruptive episode ended. Significant seismic activity around the summit resumed on 23 March 2018 and accelerated through the end of the month. Inflation continued throughout March as well. A change of composition was detected in the summit fumaroles on 23 March 2018; the fluids were enriched in CO2 and SO2. Beginning on 3 April around 0550 local time, OVPF reported a seismic swarm and deformation consistent with magma rising towards the surface. Seismic tremor began around 1040 in an area on the N flank near the Nez Coupé de Sainte Rose. The tremor intensity continued to increase throughout the day; OVPF visually confirmed the eruption around 1150 in the morning on the upper part of the N flank (figure 127).

Figure (see Caption) Figure 127. The eruptive site at Piton de la Fournaise on 3 April 2018 on the N flank near the Nez Coupé de Sainte Rose. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du 03 avril 2018 à 16h30 heure locale).

A helicopter overflight in mid-afternoon revealed a 1-km-long fissure that had opened in seven distinct segments; lava fountains emerged from two of the segments. The last active segment was just below the rampart of the Nez Coupé de Sainte Rose (figure 128). Both seismic and surface eruptive activity stopped abruptly the following day at 0400.

Figure (see Caption) Figure 128. The brief eruption of 3-4 April 2018 was located on the N flank of the central crater near the Nez Coupé de Sainte Rose, a point on the rampart rim of the Enclos. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du 03 avril 2018 à 16h30 heure locale).

Eruptive event of 27 April-1 June 2018. OVPF reported 2.5 cm of inflation in the 15 days after the 3-4 April eruption. Seismic activity resumed at the base of the summit area on 21 April, and a new seismic swarm began at 2015 local time on 27 April. This was followed three hours later by tremor activity indicating the beginning of a new eruptive event from fissures that opened on the S flank in the area of cratère Rivals (figure 129). Four fissures opened; one on each side of the crater and one cutting across it were initially active, but activity moved the next morning to a fourth fissure just downstream from Rivals crater and extended for less than 300 m. Fountains of lava rose to 30 m during a morning overflight on 28 April. Several streams of lava quickly coalesced into a single flow heading S towards the rampart at the rim of the Enclos Fouqué (figure 130). By 0830 on 28 April the flow was less than 300 m from the rim and had destroyed an OVPF seismic station and a GPS station. The OMI instrument on the Aura satellite recorded a significant SO2 plume from the event on 28 April (figure 131).

Figure (see Caption) Figure 129. A fissure extended about 300 m S from the Rivals crater on the S flank of the cone at Piton de la Fournaise on 28 April 2018 where a new eruptive event began the previous evening. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du samedi 28 avril 2018 à 10h00 heure locale).
Figure (see Caption) Figure 130. The flow from the new fissure near Rival crater at Piton de la Fournaise had flowed to within 300 m of the Enclos Fouqué caldera rim by 0830 on 28 April 2018. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du samedi 28 avril 2018 à 10h00 heure locale).
Figure (see Caption) Figure 131. An SO2 plume of 9.51 Dobson Units (DU) drifted NW from Reunion Island on 28 April 2018 where Piton de la Fournaise began a new eruptive episode the previous evening. Courtesy of NASA Goddard Space Flight Center.

Tremor activity decreased throughout the day on 28 April while the flow continued. The surface flow rate was measured initially at 8-15 m3 per second; it had slowed to 3-7 m3 per second by late that afternoon. Three active vents were observed on the morning of 29 April that continued the next day with fountains rising about 15 m (figure 132). A small cone (less than 5 m high) had grown around the southernmost vent and the larger middle vent contained a small lava lake. Visible lava was flowing only from the middle vent. The flow consisted of three branches; the two spreading to the E were less than 150 m long while the third flow traveled W past the E Cassian crater and had reached 1.2 km in length by 1020 on 30 April. On 30 April OVPF observed a flow from the previous day that had traveled 2.6 km, reaching the foot of the S edge of the l'Enclos Fouqué rampart.

Figure (see Caption) Figure 132. Lava flowed from three active vents near the Rival crater at Piton de la Fournaise on 30 April 2018. A small cone (less than 5 m high) had grown around the southernmost vent (bottom center) and the larger middle vent contained a small lava lake. Lava was actively flowing from only the middle vent. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du lundi 30 avril 2018 à 16h00 heure locale).

OVPF noted on 2 May 2018 that the intensity of volcanic tremor remained stable, slight deflation was measured, and the surface flow rate was estimated from satellite data at 1-3 m3 per second. Field observations during the afternoon of 3 May indicated that most activity was occurring from the central vent which had grown into a small pyroclastic cone with incandescent ejecta and gas emissions (figure 133). A well-developed lava tunnel had a number of roof breakouts.

Figure (see Caption) Figure 133. The eruptive site at Piton de la Fournaise on 3 May 2018 had two main vents, the larger pyroclastic cone produced incandescent ejecta and dense gas plumes. Courtesy of OVPF (©IPGP/OVPF) (Bulletin d'activité du vendredi 4 mai 2018 à 15h00 heure locale).

Field reconnaissance during 6-7 May confirmed that most of the activity was concentrated at the central cone with incandescent ejecta rising less than 10 m from the top, and the only source of lava was enclosed in a tunnel. The front of the flow was still active with numerous fires reported at the base of the rampart at the rim of the Enclos Fouqué. The farthest upstream cone was still active, but weak with only occasional bursts of incandescent ejecta. By 10 May the intensity of the volcanic tremor had stabilized at a low level. Two cones remained active, the upstream cone had incandescent ejections rising 10-20 m high. Lava was contained in tunnels near the cones but was exposed below the Piton de Bert (figure 134). The frontal lobe of the flow was located 3 km from the eruptive site, downstream of Piton de Bert (figure 135) at the base of the rampart rim of the Enclos. Numerous fires continued at the base of the rampart due to fresh flows (figure 136).

Figure (see Caption) Figure 134. Lava flows were visible on the slope break below Piton de Bert at Piton de la Fournaise on 10 May 2018. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du jeudi 10 mai 2018 à 18h30 heure locale).
Figure (see Caption) Figure 135. By 10 May 2018, the front of the flow from the 27 April eruptive event at Piton de la Fournaise was located 3 km from the eruptive site downstream from Piton de Bert. Courtesy of OVPF and Google Earth (© OVPF/IPGP) (Bulletin d'activité du jeudi 10 mai 2018 à 18h30 heure locale).
Figure (see Caption) Figure 136. Fires started by active lava flows affected the base of the rampart rim of the Enclos at Piton de la Fournaise on 10 May 2018. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du jeudi 10 mai 2018 à 18h30 heure locale).

A minor spike in seismicity was recorded on 15 May 2018; at the same time inflation resumed underneath the caldera. The smaller, farthest upstream cone was the most active on 16 May, with 20-30 m high ejecta. A webcam view on 24 May showed that the vent on the larger pyroclastic cone was nearly closed, and that flow activity was largely contained in tunnels. Field observations that day also confirmed the overall decrease in activity; only a single incandescent zone in the lava field near the vent was observed at nightfall, although persistent degassing continued (figure 137).

Figure (see Caption) Figure 137. By 24 May 2018, activity at Piton de la Fournaise from the eruptive episode that began on 27 April had diminished significantly as seen in this view of the eruptive site near the Rival crater. Photo courtesy of Cité du Volcan and OVPF (Bulletin d'activité du vendredi 25 mai 2018 à 15h00 heure locale).

An overflight on 29 May confirmed the decreasing flow activity and continued inflation. Only rare tongues of lava could be observed in the flow field. The flow front had not progressed eastward for the previous 15 days. The main cone remained open at the top with a small eruptive vent less than 5 m in diameter. Small collapses and slumps were visible on the outer flanks of the cone (figure 138). The height of the main cone was estimated at 22-25 m on 31 May and the second vent was observed to be completely closed off. OVPF reported the end of the eruption at 1430 on 1 June 2018 based on the cessation of seismic tremor (figure 139). The MODVOLC thermal alert system recorded multiple thermal alerts from 27 April through 29 May.

Figure (see Caption) Figure 138. The main cone of the eruptive event at Piton de la Fournaise remained open at the top with a small eruptive vent less than 5 m in diameter on 29 May 2018 that produced abundant steam and gas. Small collapses and slumps were visible on the outer flanks of the cone. N is to the upper left of image. Courtesy of OVPF (© OVPF/IPGP ) (Bulletin d'activité du mercredi 30 mai 2018 à 15h30 heure locale).
Figure (see Caption) Figure 139. The evolution of the RSAM signal (indicator of the volcanic tremor and the intensity of the eruption) at Piton de l aFournaise between 27 April 2018 at 2000 and 1430 on 1 June at the seismic station of BOR, located at the summit of the central cone. Courtesy of OVPF (© OVPF/IPGP) (Bulletin exceptionnel du vendredi 1 juin 2018 à 15h00 heure locale).

Eruptive event of 13 July 2018. Throughout June 2018, very little activity was reported; only 23 shallow seismic events were recorded during the month and no significant deformation was measured by the OVPF deformation network. OVPF reported that inflation resumed around 1 July. A sharp increase in seismicity was observed beginning at 2340 local time on 12 July followed by a seismic swarm and rapid deformation around midnight. Tremor activity was recorded beginning about 0330 on 13 July and located on the N flank. The first images of the eruption were visible in a webcam at around 0430. Four eruptive fissures were observed in an overflight that morning around 0800 that opened over a 500-m-long zone, spreading from upstream of la Chapelle de Rosemont towards Formica Leo. Incandescent ejecta rose less than 20 m and the aa lava had flowed about 200 m from the fissures (figures 140 and 142). The lava flow propagation rate was estimated at about 6 m per minute during the first hour of activity. Thereafter, the rate continued to decrease to less than 1 m per minute at the end of the eruption. After a progressive decrease of tremor, and about 3 hours of "gas flushes" that are typically observed at the end of Piton de la Fournaise eruptions (according to OVPF), the eruption stopped on 13 July at 2200 local time. Both MIROVA and MODVOLC recorded thermal anomalies from the brief one-day event (figure 126).

Figure (see Caption) Figure 140. A new eruption at Piton de la Fournaise on 13 July 2018 lasted only a single day and produced a 500-m-long zone with four fissure vents located on the N flank of the cone near la Chapelle de Rosemont and flowing towards Formica Leo. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du vendredi 13 juillet 2018 à 10h30 heure locale).
Figure (see Caption) Figure 141. Four fissure vents on the N flank of the central cone near la Chapelle de Rosemont produced ejecta and lava flows for about 18 hours on 13 July 2018 at Piton de la Fournaise. Courtesy of OVPF (© OVPF/IPGP) (Bulletin d'activité du vendredi 13 juillet 2018 à 10h30 heure locale).

The 13 July 2018 eruption lasted about 18 hours and produced about 0.3 million m3 of lava. Lava flows covered more than 400 m of the popular hiking trail leading to the summit (figure 142 and 143) and almost completely filled the Chapelle de Rosemont (figure 144), an old vent and a characteristic feature within the Enclos Fouqué landscape that was first described in reports of the early volcano expeditions at the end of the 18th century. This area of the volcano on the NNW flank had not experienced active eruptive events for at least the past 400 years. Despite the low volume of lava emitted and its short duration, this event significantly changed the geomorphology of the area, which was quite well known and popular with visitors. Inflation resumed after the eruptive event of 13 July and a brief pulse of seismic activity was reported by OVPF on 26 July. They noted on 13 August that after about a month of inflation, seismicity and inflation both ceased.

Figure (see Caption) Figure 142. The brief 13 July 2018 eruptive event covered an area on the NNW flank of the central cone that had not had active flow activity for at least 400 years. Photo taken midday on 13 July 2018. Courtesy of OVPF (© OVPF/IPGP) (July 2018 Monthly bulletin of the Piton de la Fournaise).
Figure (see Caption) Figure 143. The area of the lava flows covered during the 13 July 2018 eruption are shown in white, the fissures are shown in red, and the popular hiking trail to the summit is shown in yellow. Over 400 m of the trail was covered with fresh flows. The fissures were located on the NNW flank in the area of the Chapelle de Rosemont, an old vent. The base map was produced by OVPF using aerial and ground-based photographs that were processed by means of stereophotogrammetry. Courtesy of OVPF (July 2018 Monthly bulletin of the Piton de la Fournaise).
Figure (see Caption) Figure 144. Fresh, dark lava covers the Chapelle de Rosemont on 14 July 2018 after a one-day eruption at Piton de la Fournaise the previous day. The area was first described by explorers in the 18th century and had not seen recent flow activity. Courtesy of OVPF (© OVPF/IPGP) (July 2018 Monthly bulletin of the Piton de la Fournaise).

Geologic Background. The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise (OVPF), Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).


Great Sitkin (United States) — September 2018 Citation iconCite this Report

Great Sitkin

United States

52.076°N, 176.13°W; summit elev. 1740 m

All times are local (unless otherwise noted)


Small phreatic explosions in June and August 2018; ash deposit on snow near summit

Episodic recent and historic volcanic activity has been reported at Great Sitkin, located about 40 km NE of the community of Adak in the Aleutian Islands. Prior to the recent 2018 activity, the last confirmed eruption in 1974 produced at least one ash cloud that likely exceeded an altitude of 3 km (figures 1 and 2). This eruption extruded a lava dome that partially destroyed an existing dome from a 1945 eruption. Most recently, a small steam explosion was reported on 10 June 2018. In response, the Alaska Volcano Observatory (AVO) raised the Aviation Color Code (ACC) to Yellow (Advisory) from the previous Green (Normal).

Figure (see Caption) Figure 1. Eruption of Great Sitkin volcano in 1974. Photo taken from Adak Island, Alaska, located 40 km SW of the volcano. Photographer/Creator: Paul W. Roberts; courtesy of AVO/USGS (color corrected).
Figure (see Caption) Figure 2. Worldview-3 satellite image of Great Sitkin on 21 November 2017 showing the crater, areas of 1974 and 1945 lava flows, and steam (indicated by the red arrow) from the reported seismic swarm and steam event ending in 2017. Photographer/Creator: Chris Waytomas; image courtesy of AVO/USGS.

AVO had previously reported that a seismic swarm had been detected beginning in late July 2016 and continuing through December 2017. Steam from the crater was also observed during this time period, in late November 2017 (figure 2). The seismicity was characterized by earthquakes typically less than magnitude 1.0 and at depths from near the summit to 30 km below sea level. Most earthquakes were in one of two clusters, beneath the volcano's summit or just offshore the NW coast of the island. Possible explosion signals were observed in seismic data on 10 January and 21 July 2017, but no confirmed emissions were observed locally or detected in infrasound data or satellite imagery.

The most recent eruption at Great Sitkin produced a small steam explosion which was detected in seismic data at 1139 local time on 10 June 2018 (figure 3). The explosion was followed by seismic activity which began diminishing after 24 hours, and by 15-16 June had returned to background levels.

Figure (see Caption) Figure 3. View of Great Sitkin steaming on 10 July 2018. Photographed from Adak Island, Alaska, approximately 40 km SW. Photo by Alain Beauparlant; image courtesy of AVO/USGS (color corrected).

Due to heavy cloud cover on 10 June 2018, satellite views were obscured. Subsequent satellite data collected on 11 June showed an ash deposit on the surface of the snow extending to about 2 km SW from a vent in the summit crater (figure 4). Minor changes in the vicinity of the summit crater were observed from satellite data, including possible fumaroles north of the main crater. On 17 June an aerial photograph showed minor steaming at the vent (figure 5).

Figure (see Caption) Figure 4. Satellite view of the Great Sitkin crater at 2300 UTC on 11 June 2018 showing an ash deposit extending for about 2 km to the SW. Ash was likely deposited during the brief explosion on 10 June 2018. Minor steaming from a vent through the 1974 lava flow is also visible in this image. View is from the southwest. Photographer/Creator: David Schneider; image courtesy of AVO/USGS.
Figure (see Caption) Figure 5. Aerial photo showing minor steaming at the summit of Great Sitkin, 17 June 2018. A small ash deposit extends SW from the vent. Photographer: Alaska Airlines Captain Dave Clum; image courtesy of AVO/USGS.

Another small phreatic explosion was observed in seismic data at 1105 local time on 11 August. Small local earthquakes preceded the event but were not recorded following the explosion. The event is similar to three other phreatic explosions that have occurred over the past 2 years.

Geologic Background. The Great Sitkin volcano forms much of the northern side of Great Sitkin Island. A younger parasitic volcano capped by a small, 0.8 x 1.2 km ice-filled summit caldera was constructed within a large late-Pleistocene or early Holocene scarp formed by massive edifice failure that truncated an ancestral volcano and produced a submarine debris avalanche. Deposits from this and an older debris avalanche from a source to the south cover a broad area of the ocean floor north of the volcano. The summit lies along the eastern rim of the younger collapse scarp. Deposits from an earlier caldera-forming eruption of unknown age cover the flanks of the island to a depth up to 6 m. The small younger caldera was partially filled by lava domes emplaced in 1945 and 1974, and five small older flank lava domes, two of which lie on the coastline, were constructed along northwest- and NNW-trending lines. Hot springs, mud pots, and fumaroles occur near the head of Big Fox Creek, south of the volcano. Historical eruptions have been recorded since the late-19th century.

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


Sierra Negra (Ecuador) — September 2018 Citation iconCite this Report

Sierra Negra

Ecuador

0.83°S, 91.17°W; summit elev. 1124 m

All times are local (unless otherwise noted)


Fissure opens on NNE caldera rim 26 June 2018, NW-flank lava flows reach the sea

Sierra Negra shield volcano on the Galápagos Island of Isabela has erupted six times since 1948, most recently in 2005. The eruptions of 2005, 1979, 1963, and 1953 were located in the area known as 'Volcán Chico' near the NNE rim of the summit caldera, which extends about 9 km E-W and 7 km N-S (figure 12). The lava flows generated in these eruptions were directed mainly towards the N and NE flanks of Sierra Negra, in some cases reaching Elizabeth Bay to the N and in others filling the interior of the caldera (figure 13). A new effusive eruption that occurred from 26 June through August 2018 is covered in this report with information provided primarily by Instituto Geofísico, Escuela Politécnica Nacional (IG-EPN). Additional information comes from the Washington Volcanic Ash Advisory Center (VAAC), and several sources of satellite information.

Figure (see Caption) Figure 12. Sierra Negra is located on the southern part of Isabela Island in the Galápagos National Park, Ecuador. Courtesy of IG (Informe Especial Nº 2, Volcán Sierra Negra- Islas Galápagos: Descripción del estado de agitación interna y posibles escenarios eruptivos, 12 January 2018).
Figure (see Caption) Figure 13. The Sierra Negra caldera with the locations of GPS stations and the fissures, vents, and flows from the 2005 eruption. From Geist et al. (2005), courtesy of IG (Informe Especial Nº 2, Volcán Sierra Negra- Islas Galápagos: Descripción del estado de agitación interna y posibles escenarios eruptivos, 12 January 2018).

Beginning in 2017, the Geophysical Institute of the National Polytechnic School (IGEPN) installed a surveillance network of six broadband seismic stations for the Galápagos volcanoes. One station is located on the NE edge of the Sierra Negra caldera and another on the SE flank. After 12 years of little activity, an increase in seismicity beneath and around the caldera became evident by July 2017 (figure 14). On 19 October 2017 (local time) the seismic monitors detected a 16-km-deep M 3.8 earthquake with an epicenter on the NE border of the caldera in the vicinity of Volcán Chico. Four additional similar earthquakes occurred within the next hour. Another earthquake of similar size occurred on 22 October; between 15 and 16 November, three earthquakes with M 3.0 or greater were recorded. The frequency of seismic activity increased significantly in December 2017, with over 550 events recorded during the first three weeks of December 2017; at least three had magnitudes greater than 3. GPS receivers showed uplift of the caldera floor of 80 cm between 2013 and 2017. InSAR interferometry data indicated substantial inflation of the caldera floor of about 70 cm between December 2016 and late November 2017, reaching a level higher than that which preceded the eruption of 2005 (figure 15).

Figure (see Caption) Figure 14. The number of daily seismic events at Sierra Negra between 13 May 2015 and 23 November 2017 show a distinct increase in activity by July 2017. The colors represent different types of earthquakes; red is VT or volcanotectonic, orange is LP or Long Period, and blue is HB or Hybrid. Courtesy of IG (Informe Especial Sierra Negra N.- 2, Actividad reciente del volcán Sierra Negra – Isla Isabela, 23 November 2017).
Figure (see Caption) Figure 15. Inflation of the caldera floor at Sierra Negra between December 2016 and November 2017 exceeded 70 cm. The left graph shows the displacement plotted in centimeters versus time, and the right image is the spatial deformation from the InSAR data showing inflation at the caldera (center) and on the SW coast of Isla Isabela. Figures courtesy of Falk Amelung (RSMAS) and IG (Informe Especial Sierra Negra N.- 2, Actividad reciente del volcán Sierra Negra – Isla Isabela, 23 November 2017).

By early January 2018, inflation over the preceding 12 months was close to 1 m, with a total inflation exceeding that prior to the 2005 eruption. Seismic activity, focused on two fracture zones trending NE-SW across the summit caldera, continued to increase until 26 June 2018 when a fissure opened near Volcán Chico on the NNE caldera rim. Over the next 24 hours four fissures opened on the N rim and the NW flank. Three of the fissures were active only for this period, but the fourth, on the NW flank about 7 km below the caldera rim, continued to effuse lava for all of July and most of August 2018. Lava flows reached the sea in early July. Several pulses of increased effusive activity corresponded with increased seismic, thermal, and gas-emission activity recorded by both ground-based and satellite instrumentation. By the last week of August active flows were no longer observed, although the cooling flows continued to emit thermal signals for several weeks.

Activity during January-early June 2018. Elevated seismicity continued into 2018 with a M 3.8 event recorded on 6 January 2018 that was felt by tourists, guides, and Galápagos National Park officials. Tens of additional smaller events continued throughout the month, reaching more than 100 seismic events per day a few times; the earthquakes were located below the caldera at a depth of less than 8 km. A M 4.1 event on 10 January was located at a depth of 7 km. By 12 January, the total inflation of the caldera since the beginning of 2017 was 98 cm (figure 16).

Figure (see Caption) Figure 16. Seismicity and deformation at Sierra Negra between 13 May 2015 and 28 December 2017. The orange line represents the cumulative VT earthquakes, and the blue points record the inflation in cm of the floor accumulated since the beginning of 2015. A change in slope of both curves is evident at the end of 2017 indicating the rate of increase of inflation and seismicity. Courtesy of IG (Informe Especial Nº 2, Volcán Sierra Negra- Islas Galápagos: Descripción del estado de agitación interna y posibles escenarios eruptivos, 12 January 2018).

IG reported 14 seismic events with magnitudes ranging from 3.0-4.6 between 1 January and 19 March 2018. A M 4.4 event on 18 January was located less than 1 km below the surface with an epicenter on the S rim of the caldera. A M 4.1 event on 27 February was also located less than 1 km below the surface. A M 4.6 event on 14 March was the largest to date at Sierra Negra and was located only 0.3 km below the surface. Measurements of CO2, SO2, and H2S made at the Azufral fumarole field (figure 17) on the W rim of the caldera in early February did not have values significantly different compared to May 2014 and September 2017. With the continued increase in frequency and magnitude of shallow seismic activity, IG noted the increased risk of renewed eruptive activity, and noted that most of the active flows of the last 1,000 years were located on the N flank (figure 18).

Figure (see Caption) Figure 17. A fumarole field near Azufral on the W rim of the Sierra Negra caldera on 6 February 2018 remained unchanged after several months of increased seismicity in the area. Photo by M. Almeida, courtesy of IG-EPN (Informe Especial del Volcán Sierra Negra (Islas Galápagos) -2018 - Nº 3, Actualizado del estado de agitación interna y posibles escenarios eruptivos, 19 March 2018).
Figure (see Caption) Figure 18. Simplified geologic map of Sierra Negra with lava flows colored as a function of relative age (modified from Reynolds et al., 1995), courtesy of IG (Informe Especial del Volcán Sierra Negra (Islas Galápagos) -2018 - Nº 3, Actualizado del estado de agitación interna y posibles escenarios eruptivos, 19 March 2018).

Increases in seismicity continued into early June. IG noted that on 25 May 2018, 104 seismic events were recorded, the largest number in a single day since 2015. A M 4.8 event on 8 June was accompanied by over 40 other smaller earthquakes. The earthquake epicenters were mainly located on the edges of the crater in two NE-SW trending lineaments; the first covered the N and W edges of the crater and the second trended from the NE edge to the S edge. Deformation data indicated the largest displacements were at the caldera's center, compared with lower levels of deformation outside of the caldera.

Eruption of 26 June-late August 2018. IG reported an increase in seismicity and a M 4.2 earthquake on 22 June 2018. A larger M 5.3 earthquake was detected at 0315 on 26 June, 5.3 km below the caldera. The event was felt strongly on the upper flanks and in Puerto Villamil (23 km SE). About 8 hours later, at 1117, an earthquake swarm characterized by events located at 3-5 km depth was recorded. A M 4.2 earthquake took place at 1338 and was followed by increasing amplitudes of seismic and infrasound signals. Parque Nacional Galápagos staff then reported noises described as bellows coming from the Volcán Chico fissure vent, which, coupled with the seismicity and infrasound data, suggested the start of an eruption. About 20 minutes later IG described a thermal anomaly identified in satellite images in the N area of the caldera near Volcán Chico and Park staff observed lava flowing towards the crater's interior as well as towards the N flank in the direction of Elizabeth Bay (figure 19).

Figure (see Caption) Figure 19. Lava flows descended from the N flank of Sierra Negra to Elizabeth Bay on 26 June 2018 from four distinct fissure vents (numbered). Fissure 1 was located near Volcan Chico on the caldera rim, and fissures 2, 3, and 4 were located on the N flank. Details of the fissures are discussed later in the report. Video of the flow was captured by Nature Galápagos. Photo courtesy of AFP and BBC News, annotated and reprinted by IG (Informe Especial N° 16 – 2018, Volcán Sierra Negra, Islas Galápagos, Actualización de la Actividad Eruptiva, Quito, 23 de Julio del 2018).

The Washington VAAC reported an ash plume visible in satellite imagery late on 26 June at 10.6 km altitude drifting SW. By the following morning, a plume of ash mixed with SO2 was drifting W at 8.2 km altitude. IG reported a new ash emission late on 27 June drifting NW at 6.1 km altitude. A substantial SO2 plume emerged on 27 June and was recorded by the OMI and OMPS satellite-based instruments drifting SW that day and the next (figure 20). The MODVOLC thermal alert system confirmed the beginning of the eruption with over 100 alert pixels recorded on 27 June and over 50 the following day. The MIROVA system recorded an abrupt, very high thermal signal beginning on 26 June (figure 21). Seismic and acoustic data indicated a gradual decrease of activity after the initial outburst, but effusive lava flows continued on 27 June.

Figure (see Caption) Figure 20. A large plume of SO2 was emitted from Sierra Negra on 27 June 2018 at the beginning of the latest eruptive episode. It drifted SW the following day, as seen in these images captured by the OMPS instrument on the Suomi NPP satellite. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 21. The MIROVA project graph of thermal energy at Sierra Negra from 31 January 2018 through September 2108 shows the start of the lava flows on 27 June 2018 (UTC). Pulses of high thermal energy continued through late August when flow activity ceased; cooling of the flows continued into September 2018. Courtesy of MIROVA.

During 27 and 28 June, IG scientists were able to make a site visit to capture thermal, photographic, and physical evidence of the new lava flows (figure 22). A composite thermal image showed the extent of flows that traveled down the N flank as well as into the caldera (figure 23). A temperature of 580°C was measured near the eruptive fissure, and the surface temperatures averaged about 60°C, although some flows were measured as high as 200°C. The temperature inside a fracture on a lava flow was measured at 975°C (figure 24). Pelée hair and "spatter" bombs were visible around the eruptive fissures.

Figure (see Caption) Figure 22. The lava flows of 26 June 2018 at Sierra Negra emerged from a fissure on the N flank of the caldera rim and other fissures on the N flank and flowed N. N is to the right. Photo by Benjamin Bernard, courtesy of IG (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).
Figure (see Caption) Figure 23. Composite thermal images of the new lava flows at Sierra Negra taken on 27 June 2018 reveal the flows that emerged from the Volcán Chico fissure zone; most flows traveled N down the flank, a few (on the left) traveled down into the caldera. Images by Silvia Vallejo, courtesy of IGEPN (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).
Figure (see Caption) Figure 24. The temperature of incandescent lava within a fresh flow at Sierra Negra was measured at 975°C on 27 June 2018. Left image by Francisco Vásconez; thermal image by Silvia Vallejo, courtesy of IGEPN (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).

Pahoehoe and aa flows along with lava tunnels were visible in drone images. The visible fissures were slightly arcuate and aligned in a general ENE direction, similar to the fissures of 1979 and 2005 in the vicinity of Volcán Chico. The largest flow was more than 150 m long; they reached up to 130 m wide in the flat areas, but only between 25 and 35 m wide where they were channeled on the steeper slope. In the flatter areas they had characteristics of pahoehoe with a smooth surface, a sometimes rounded texture and lava tunnels (figure 25), while in the channelized areas with a steeper slope they had a rougher surface and were characterized as aa (figure 26). The flows averaged 0.5-1 m thick and in several places the lava filled fissures or previous depressions. The samples of pahoehoe that were collected were all aphanitic with no crystals, strongly iridescent, and vesiculated with fluid textures that indicated a high gas content and low viscosity.

Figure (see Caption) Figure 25. Pahoehoe flows, spatter, and a collapsing lava tunnel were visible near fissure 1 (above 'Spatter') at Sierra Negra when imaged by a drone during a field visit on 27-28 June 2018 shortly after the new eruptive episode began. This image covers the area near the top center of the image in figure 22 close to the fissure. Photos were taken by a drone flying 60 m above the flows by Benjamin Bernard, courtesy IGEPN (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).
Figure (see Caption) Figure 26. Aa flows formed as lava traveled down the steeper parts of the N flank of Sierra Negra on 26 June 2018, seen in this drone image taken during a field visit on 27-28 June. This image general location can be seen in the bottom right area in figure 22. Photos were taken by a drone flying 60 m above the flows by Benjamin Bernard, courtesy IGEPN (Volcán Sierra Negra, Informe de campo 27-28 junio2018, Termografía, Cartografía, y muestreo de los nuevos flujos de lava, sector de Volcán Chico).

A small seismic event followed by several hours of tremor was recorded at 1552 on 1 July; a short while later National Park staff observed active lava flows on the NW flank. On 4 July, IG reported a M 5.2 earthquake that was 5 km deep; it was followed by 68 smaller seismic events. On 7 July seismic tremor activity indicating another pulse of magmatic activity was recorded by a station on the NE edge of the caldera at 1700. At the same time, satellite data showed an increase in the intensity of the thermal anomaly on the NW flank; Parque Nacional Galápagos staff confirmed strong visible incandescence in an area near the beach. Tremor activity continued on 8 July, although the amplitude gradually decreased.

The Washington VAAC reported an ash plume visible in satellite imagery on 2 July at 6.1 km altitude drifting SW. Later in the day a concentrated plume interpreted to be primarily steam and gas extended about 260 km SW. On 8 July ash could be seen moving both W and SW in satellite imagery at 2.7-3.0 km altitude. Later that day ash was visible extending about 115 km SW from the summit and other gases extended 370 km W. That evening the ash plume extended about 190 km SW at 3.7 km altitude. Gas-and-ash plumes were observed continuously drifting SW for the next three days (9-11 July) at 3.7 km altitude to a distance of about 80 km. On 13 July, two areas of ash and gas were seen in satellite imagery moving 25 km NW from the summit and up to 45 km SW at altitudes of 3.9 and 2.4 km respectively. A low-level ash plume on 16 July extended 30 km SW from the summit at 2.4 km altitude; incandescence was also visible in the webcam. The next day ash and gas emissions extended about 120 km SW at a similar altitude. Ongoing steam, gas, and ash emissions were seen in satellite imagery and in the webcam extending 110 km NW from the summit on 19 July at 3.4 km altitude. The Washington VAAC reported an ash plume on 30 July that rose to 3.4 km altitude and drifted SW. Strong SO2 emissions were recorded by both the OMPS and OMI satellite instruments throughout July 2018 (figure 27).

Figure (see Caption) Figure 27. SO2 plumes from Sierra Negra exceeded 2 Dobson Units (DU) nearly every day during July 2018. Data gathered by the OMPS satellite instrument showed a large plume drifting SW on 2 July (top left), and a more narrow stream of SO2 drifting SW on 3 July (top right). The OMI satellite instrument captured large W-drifting plumes on 12 (bottom left) and 14 (bottom right) July. Courtesy of NASA Goddard Space Flight Center.

In a report issued by IGEPN covering activity through 23 July 2018, they noted that at least four fissures had initially opened on 26 June at the start of the eruption (see numbers in figure 19 at the beginning of this report, and figure 31 at the end). Fissure 1, the longest at 4 km, was located at the edge of the caldera in the area of Volcán Chico; lava flows from this fissure traveled 7 km down the flanks, and over 1 km within the interior of the caldera. NW-flank fissures 2, 3, and 4 were much smaller (about 250 m long). Fissures 1-3 were active only until 27 June; fissure 4 continued to be active throughout July. Lava from this fissure reached the ocean on 6 July.

Gas and possible volcanic ash extended 35 km SW of the summit on 4 August at 1.5 km altitude; this was the last report of an ash plume by the Washington VAAC for the eruption. Daily reports from IGEPN indicated that nightly incandescence from advancing flows continued into August. Occasional low-level steam and gas plumes were also visible. Pulses of lava effusion on 4 and 9 August were accompanied by major episodes of seismic tremor activity and substantial SO2 plumes (figure 28). On 15 August satellite images showed lava from fissure 4 continuing to enter the ocean. The area where the lavas entered the sea were far from any human population or agricultural activities and only accessible by boats.

Figure (see Caption) Figure 28. At Sierra Negra, large SO2 plumes were recorded by the OMPS instrument on the Suomi NPP satellite at the same time that an increase in seismic activity and effusion were noted on both 4 (left) and 9 (right) August 2018. Courtesy of NASA Goddard Space Flight Center.

Throughout the ongoing eruption, pulses of thermal activity detected by MODIS infrared satellite sensors correlated with increases in seismic activity and observed flow activity. The MIROVA plot showed a high level of heat flow from the onset of the eruption on 26 June gradually decreasing in intensity through mid-August (figure 21). This was followed by a significant drop in heat flow and gradual cooling thereafter. After the initial fissure activity near the crater rim on 26-27 June, all subsequent activity was concentrated farther down the N flank at fissure 4 and is reflected in the number of pixels concentrated in that area of the MODVOLC plot of thermal alerts from June-September 2018 (figure 29).

Figure (see Caption) Figure 29. MODVOLC thermal alert locations corresponded to the locations of the observed flow activity at Sierra Negra, showing the sustained thermal activity from the mid-flank fissure 4 that lasted from late June through mid-September 2018. Courtesy of HIGP - MODVOLC Thermal Alerts System .

The number of seismic events recorded during the eruptive episode had increased between 26 June and 30 July 2018 to an average of 265 per day. The peak was recorded on 29 June with 940 earthquakes. Between 31 July and 23 August, the average number was 121 per day, still higher than the level of 38 per day prior to the beginning of the eruption on 26 June. IG reported a continuous decline in activity during the last two weeks of August 2018. After the initial burst of effusive activity during 26-27 June, five additional pulses of increased thermal, seismic, and gas-emission activity were observed in multiple sources of data on 1-2, 7-8, and 31 July, and 4 and 9 August (figure 30).

Figure (see Caption) Figure 30. Multiple parameters of data from the eruption of Sierra Negra from 21 June to 30 August 2018. The dashed green line marks the start of the eruption, while the pale green vertical bars indicate the different eruptive pulses recorded throughout the eruption. a) Seismic energy data (RSAM) recorded by station VCH1, in a window between 1-8 Hz (location shown in figure 31); b) Time series of degassing of SO2 recorded by the OMI and OMPS satellites instruments; c) thermal anomalies recorded by MODVOLC. Courtesy of IGEPN (Informe Especial N°18 – 2018, Volcán Sierra Negra, Islas Galápagos, "Terminación de episodio ruptive actual", Quito, 31 de Agosto del 2018), also published in Vasconez et al (2018).

In a summary report on 31 August 2018, IG reported that the eruption was divided into two main phases. The first and most energetic phase lasted one day (26 June) and was characterized by the opening of five fissures (table 2) located on the rim and N and NW flanks, and creation of lava flows that traveled as far as 7 km from the vents (figure 31). Lava was only active from all five fissures during the first day of the eruption, covering an area greater than 17 km2. During the rest of the eruption from 27 June-23 August, about 13 km2 of lava was produced from fissure 4, with lava reaching the sea on 6 July and expanding the coastline by 1.5 km2. Detailed descriptions of the fissures provided by IGEPN are given in the following section. By 25 August the lava flows covered an area of 30.6 square kilometers. Activity continued to decline the last week of August with decreased seismicity, gas emission, and no surficial activity visible.

Figure (see Caption) Figure 31. Map of the 26 June-August 2018 eruption of Sierra Negra volcano. The eruptive fissures are numbers and shown in yellow and described in detail in the next section. The coastline with Elizabeth Bay is shown in blue, and the lava flows appear in red. The green points include GPS and seismic stations, the epicenter of the earthquake of 5.3 MLV on 26 June, El Cura (control station of the Galápagos National Park) and the panoramic vista visited by tourists. Courtesy of IGEPN (Informe Especial N°18 – 2018, Volcán Sierra Negra, Islas Galápagos, "Terminación de episodio ruptive actual", Quito, 31 de Agosto del 2018), also published in Vasconez et al (2018).

Table 2. Descriptions of the five fissures active during the June-August 2018 eruption of Sierra Negra (see figure 31 for locations). Courtesy of IGEPN (Informe Especial N°18 – 2018, Volcán Sierra Negra, Islas Galápagos, "Terminación de episodio ruptive actual", Quito, 31 de Agosto del 2018)

Feature Location Description
Fissure 1 Edge of the caldera in the Volcán Chico area, trending WNW, tangential to the edge of the caldera. Four kilometers in length with lava flows that moved toward both the interior of the caldera and down the flank from the beginning of the eruption until 27 June, covering an area of 14.6 km2. The flows deposited outside the crater traveled 7 km downhill, without reaching the sea, while those inside it reached a maximum distance of 1.1 km.
Fissure 2 NW of the caldera about 3 km below its edge of the caldera at an elevation of 700 m. Approximately 250 m long and produced 4-km-long lava flows from the beginning of the eruption until 27 June, covering an area of 2.2 km2; its lava did not reach the sea.
Fissure 3 WNW of the caldera about 4 km below its edge at an elevation of 550 m. Approximately 250 m long and active from the beginning of the eruption until 27 June, emitting lava flows that covered an area of about 0.4 km2. The lava flows had a length of about 2 km and did not reach the sea.
Fissure 4 NW flank at an elevation of 100 m between 7 and 8 km below the rim of the caldera. Continuously emitting lava flows throughout the eruption. It was located on the On 6 July the lava flows from this fissure reached the ocean and modified the coastline of Isla Isabela by 1.5 km2. By 25 August when active flow ceased, its lavas had covered an area of approximately 13.3 km2.
Fissure 5 Western flank at an elevation of 840 m, 1.5 km downhill from the inner edge of the caldera. Length of 170 m and covered 0.026 km2.

References: Davidge L, Ebinger C, Ruiz M, Tepp G, Amelung F, Geist D, Cote D, Anzieta J, 2017, Seismicity patterns during a period of inflation at Sierra Negra volcano, Galápagos Ocean Island Chain. Earth and Planetary Science Letters. 462. DOI: 10.1016/j.epsl.2016.12.021.

Geist D, Naumann T R, Standish J J, Kurz M D, Harpp K S, White W M , Fornari D, 2005, Wolf Volcano, Galapagos Archipelago: Melting and magmatic evolution at the margins of a mantle plume. Journal of Petrology 46:2197-2224.

Vasconez F, Ramón P, Hernandez S, Hidalgo S, Bernard B, Ruiz M, Alvarado A., La Femina P, Ruiz G, 2018, The different characteristics of the recent eruptions of Fernandina and Sierra Negra volcanoes (Galápagos, Ecuador), Volcanica 1(2): 127-133. DOI: 10.30909/vol.01.02.127133.

Geologic Background. The broad shield volcano of Sierra Negra at the southern end of Isabela Island contains a shallow 7 x 10.5 km caldera that is the largest in the Galápagos Islands. Flank vents abound, including cinder cones and spatter cones concentrated along an ENE-trending rift system and tuff cones along the coast and forming offshore islands. The 1124-m-high volcano is elongated in a NE direction. Although it is the largest of the five major Isabela volcanoes, it has the flattest slopes, averaging less than 5 degrees and diminishing to 2 degrees near the coast. A sinuous 14-km-long, N-S-trending ridge occupies the west part of the caldera floor, which lies only about 100 m below its rim. Volcán de Azufre, the largest fumarolic area in the Galápagos Islands, lies within a graben between this ridge and the west caldera wall. Lava flows from a major eruption in 1979 extend all the way to the north coast from circumferential fissure vents on the upper northern flank. Sierra Negra, along with Cerro Azul and Volcán Wolf, is one of the most active of Isabela Island volcanoes.

Information Contacts: Instituto Geofísico (IG), Escuela Politécnica Nacional, Casilla 17-01-2759, Quito, Ecuador (URL: http://www.igepn.edu.ec ); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Nature Galápagos (Twitter: @natureGalápagos, https://twitter.com/natureGalápagos).


Nishinoshima (Japan) — September 2018 Citation iconCite this Report

Nishinoshima

Japan

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

All times are local (unless otherwise noted)


Quiescence interrupted by brief lava flow emission and small explosions in July 2018

Nishinoshima is an active volcano in the Ogasawara Arc, about 1,000 km S of Tokyo, Japan. After 40 years of dormancy, activity increased in November 2013 and has since formed an island. The eruption has continued with subaerial activity that largely consists of lava flows and small gas-and-ash plumes. This report covers November 2017 through July 2018, and summarizes activity noted in reports issued by the Japan Meteorological Agency, and images and footage taken by the Japan Coast Guard (JCG).

No eruptive activity at Nishinoshima had been noted since mid-August 2017, when lava was last entering the ocean. Activity recommenced on 12 July and a 200-m-long lava flow was confirmed on 13 July. The lava flow was accompanied by explosive activity that ejected blocks and bombs out to 500 m from the vent, plumes and water discoloration (figures 60, 61, and 62). An aerial survey by the JCG on 30 July showed that activity had ceased and the lava flow had reached 700 m in length, terminating 100 m from the ocean.

Figure (see Caption) Figure 60. Aerial photo of Nishinoshima taken on 18 July 2018. The photo shows the active lava flow emanating from the vent along with a gas plume, and water discoloration. A closer view of the lava flow is given in figure 61. The island is approximately 1.9 x 1.9 km in size. Courtesy of the Japan Coast Guard.
Figure (see Caption) Figure 61. A view of the active Nishinoshima vent and 200-m-long lava flow on 13 July 2018. The vent is also producing a dilute ash plume from the eastern side of the cone. Courtesy of the Japan Coast Guard.
Figure (see Caption) Figure 62. Screenshot from a thermal infrared video of the active Nishinoshima vent taken on 13 July 2018. The video shows explosions ejecting incandescent material onto the flanks of the cone and the active lava flow. Courtesy of the Japan Coast Guard.

After the July activity, Nishinoshima again entered a phase of quiescence with activity limited to fumaroles around the vent. Himawari-8 satellite observations noted no increased thermal output following the July 2018 eruption. Thermal anomalies detected by satellite-based MODIS instruments were identified by the MODVOLC system from during 12-21 July 2018.

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

Information Contacts: Japan Coast Guard (JCG) Volcano Database, Hydrographic and Oceanographic Department, 3-1-1, Kasumigaseki, Chiyoda-ku, Tokyo 100-8932, Japan (URL: http://www.kaiho.mlit.go.jp/info/kouhou/h29/index.html, http://www1.kaiho.mlit.go.jp/GIJUTSUKOKUSAI/kaiikiDB/kaiyo18-e1.htm); Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.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/).


Rincon de la Vieja (Costa Rica) — September 2018 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

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

All times are local (unless otherwise noted)


Intermittent weak phreatic explosions during January-March and July-August 2018

The Rincón de la Vieja volcano complex has generated intermittent phreatic explosions since 2011; during 2017, weak phreatic explosions occurred during May, June, July, September, and October (BGVN 42:08 and 43:03). This activity continued through August 2018. The volcano is monitored by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA).

According to OVSICORI-UNA, at 1758 on 9 January 2018, an explosion produced a plume that rose 1 km above the crater rim. On 12 January, OVSICORI-UNA reported some small phreatic explosions. The webcam detected weak explosions again in mid-February. Another weak explosion on 22 February confirmed the presence of a crater lake.

During the first week of March OVSICORI-UNA reported weak phreatic explosions of low amplitude that were only be detected by the webcam (figure 28), and not by seismic instruments. During the week of 5-11 March there were 2-4 weak phreatic explosions occurred per day, along with strong tremor on the 10th. Small eruptions were seen on unspecified days the week of 12-18 March.

Figure (see Caption) Figure 28. Webcam image of a phreatic explosion at Rincon de la Vieja on 3 March 2018. Courtesy of OVSICORI-UNA.

No phreatic activity was reported during the second half of March through June, though on 20 May a seismic swarm of about 30 earthquakes was recorded. After a tremor on 3 July, a possible weak phreatic explosion occurred on 4 July at 0044, followed by a pulse of tremor. On 28 July, at 1828, a small explosion followed by tremor was recorded.

On 3 August OVSICORI-UNA reported that two weak explosions occurred at dawn. On 14 August, another weak explosion began at 1828 and lasted three minutes. Foggy conditions prevented webcam views and an estimate of a plume height. Other weak explosions were recorded on 17 August at 1407 and 2015.

Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A Plinian eruption producing the 0.25 km3 Río Blanca tephra about 3,500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/).


Semeru (Indonesia) — September 2018 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Small ash plumes in February, April, July, and August 2018; persistent thermal hotspot in the crater

Semeru volcano is the tallest volcano in Java (figure 33) and one of the most active in Indonesia. The Mahameru summit area contains the active Jonggring-Seloko vent where activity consists of dome growth and regular ash plumes, along with pyroclastic flows, avalanches, and lava flows that travel down the SE-flank ravine. The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM) Volcano Alert level for Semeru throughout the report period is II (on a scale of I-IV). The last Volcano Observatory Notice for Aviation (VONA) was issued on 9 January 2017, and the status has not changed during the reporting period. This report summarizes the activity from January to 24 August 2018 and is based on Volcano Ash Advisory Center (VAAC) ash advisories and satellite data.

Figure (see Caption) Figure 32. View looking NW at the quiet Mahameru summit area of Semeru on 24 August 2018 taken by a webcam courtesy of MAGMA Indonesia via Ø.L. Andersen's Twitter feed.

While there were no observatory activity reports issued, the Darwin VAAC issued reports for five events that produced ash plumes to altitudes ranging 3.4 to 4.9 km (table 22). MIROVA (Middle InfraRed Observation of Volcanic Activity) thermal data indicate near-consistent low-level thermal activity at Semeru after a period of no detected thermal anomalies in late January through early February. This supports the elevated thermal energy detected by Sentinel-2 satellite data at the Jonggring-Seloko vent and along the SE-flank ravine (figure 34). The MODVOLC algorithm detected 16 high-temperature hotspots through the reporting period, six in January, two in March, three in April, one in July, and two in August through to the 24th.

Table 22. Summary of ash plumes (altitude and drift direction) and pyroclastic flows at Semeru, January to 24 August 2018. The summit is at 3,657 m elevation. Data courtesy of Darwin VAAC report.

Date Altitude (km) Drift direction Other notes
24 Feb 2018 4.6 20 km ESE and WSW --
29 Apr 2018 3.4 NW Short-lived discrete eruption
20 Jul 2018 4.9 SW Minor discrete eruption
30-31 Jul 2018 4.3 W --
23-24 Aug 2018 4.3 W and SW --
Figure (see Caption) Figure 33. MIROVA plot of Log Radiative Power showing the relative thermal energy at Semeru ending September 2018. The detected thermal activity is more intense before mid-January 2018 when there was a gap in detected data before regular low-level activity resumed. Courtesy of MIROVA.
Figure (see Caption) Figure 34. Sentinel-2 false color thermal satellite images showing the persistent elevated thermal anomaly in the Jonggring-Seloko crater of Semeru from January through to 24 August 2018. Hot material can sometimes be identified in the SE-flank ravine. The larger central image is annotated with the major morphological features. False color (urban) images (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Øystein Lund Andersen? (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: http://www.oysteinlundandersen.com).


Sinabung (Indonesia) — September 2018 Citation iconCite this Report

Sinabung

Indonesia

3.17°N, 98.392°E; summit elev. 2460 m

All times are local (unless otherwise noted)


No significant ash plumes seen after 22 June 2018; minor ash in early July

Sinabung volcano is located in the Karo regency of North Sumatra, Indonesia. The current eruptive episode commenced in late 2013, after phreatic activity in 2010, producing ash plumes, lava domes and flows, and pyroclastic flows that caused evacuation and relocation of nearby communities. This report covers activity from April through early July, and is based on information provided by MAGMA Indonesia, the Darwin Volcanic Ash Advisory Center (VAAC), the Center for Volcanology and Geological Hazard Mitigation (CVGHM, also known as PVMBG), satellite data, and field photographs. Sinabung has been on Alert Level IV, the highest hazard status, since 2 June 2015.

The eruption has built a pyroclastic flow and lava fan to the SE (figure 60). This activity continued into 2018, with the last significant ash plume reported on 22 June (table 8). However, minor ash emissions continued at least through 5 July 2018.

Figure (see Caption) Figure 60. Satellite images showing Sinabung before and after the eruption with the newly-developed fan of pyroclastic flow, volcanic ash, and lava flow deposits. Top: Landsat-8 true color satellite image (pan-sharpened) acquired on 7 June 2013 before the eruption began. Bottom: Sentinel-2 natural color satellite image acquired on 16 July 2018, after the eruption ended. Courtesy of Sentinel Hub Playground.

Table 8. Summary of ash plumes (altitude and drift direction) and pyroclastic flows at Sinabung, April-June 2018. The summit is at 2,460 m elevation. Data courtesy of Darwin VAAC reports, MAGMA Indonesia VAAC reports, and CVGHM volcanic activity reports.

Date Ash plume altitude (km) Ash plume drift direction Pyroclastic flows
06 Apr 2018 7.5 W, S 3.5 km
12 Apr 2018 2.7 WNW Yes
19 Apr 2018 5.5 ESE 1 km
19 May 2018 3.2 NW --
20 May 2018 5.0 WNW --
15 Jun 2018 3.0 ESE --
22 Jun 2018 3.5 SE --

An eruption on 6 April 2018 at 1607 local time produced an ash plume that reached about 7.5 km above the summit. The eruption also produced pyroclastic flows that traveled about 3.5 km from the summit down the SE slope (figure 61). The eruption resulted in the closure of a nearby airport and ashfall affected hundreds of hectares of agricultural land. Two more notable ash plumes were reported on 12 and 19 April, to altitudes of about 2.7 and 5.5 km, respectively. A pyroclastic flow was reported during the 12 April eruption. Smaller ash and gas emissions occurred through the month.

Figure (see Caption) Figure 61. Eruption of Sinabung on 6 April 2018 at 1600 local time that produced an ash plume that reached over 5 km above the summit, and pyroclastic flows that reached about 3.5 km down the SE flank. Courtesy of Agence France-Presse via Straits Times.

Two ash plumes were recorded on 19 and 20 May, rising to about 3.2 and 5 km altitude, respectively. Throughout June small diffuse gas-and-ash plumes continued (figures 62 and 63). The last activity reported by the agencies was on the 15 and 22 June, when ash plumes reached 3 and 3.5 km altitude (figure 64). Activity after 22 June was limited to seismicity and ash, gas, and steam plumes to several hundred meters above the summit (figure 65). Although an elevated thermal signature was detected in Sentinel-2 satellite data on 30 August 2018, there were no reports of renewed activity.

Figure (see Caption) Figure 62. View of the Sinabung summit vent area during ash venting on 20 June 2018. This view from the SW shows the perched remains of the lava dome and collapse scar. Photo courtesy of Brett Carr, Lamont-Doherty Earth Observatory.
Figure (see Caption) Figure 63. Relatively consistent ash venting at Sinabung on 20 June 2018. This view shows the pyroclastic flow fan and the 2014 lava flow in the lower center of the photo. Drone photo courtesy of Brett Carr, Lamont-Doherty Earth Observatory.
Figure (see Caption) Figure 64. Small ash plume rising from Sinabung at 2106 on 22 June 2018. The ash plume reached about 1 km above the crater. Courtesy of BNPB (color adjusted).
Figure (see Caption) Figure 65. Minor ash venting at Sinabung on 5 July 2018. Photo courtesy of Brett Carr, Lamont-Doherty Earth Observatory.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/, Twitter: https://twitter.com/BNPB_Indonesia ); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/, Twitter: https://twitter.com/id_magma); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Brett Carr, Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY (URL: https://www.ldeo.columbia.edu/user/bcarr); Agence France-Presse (URL: http://www.afp.com/); Straits Times (URL: https://www.straitstimes.com).


Telica (Nicaragua) — September 2018 Citation iconCite this Report

Telica

Nicaragua

12.606°N, 86.84°W; summit elev. 1036 m

All times are local (unless otherwise noted)


Explosions on 21 June and 15 August 2018; local ashfall from June event

The Telica volcano complex, which consists of several cones and craters, has had intermittent eruptions since the Spanish conquest, with emissions of gas and ash. According to The Instituto Nicaragüense de Estudios Territoriales (INETER), the volcano is monitored in real time by a permanent seismic station near the crater. It is also visited several times per year for visual observations, to measure sulfur dioxide emissions, and measure temperatures in the crater and fumaroles near the seismic station. A gas-and-ash explosion occurred in early May 2016 (BGVN 42:01). This report covers activity from September 2016 through June 2018.

INETER reported that local residents heard a small gas explosion on 10 September 2017, and warned the public to stay at least 2 km away from the crater. No ash emissions were reported related to this event.

According to INETER and the Sistema Nacional para la Prevención, Mitigación y Atención de Desastres (SINAPRED), an eruption began at 0708 on 21 June 2018. Explosions produced an ash plume that rose 500 m above the crater and drifted E, S, and SW. Ejected tephra was deposited within a 1-km-radius of the volcano, and ashfall was reported in nearby areas, including La Joya, Las Marías (7 km NNW), Pozo Viejo (10 km NNW), Ojo de Agua, San Lucas (11 km NNW), Las Higueras, Las Grietas (12 km NNW), and Posoltega (16 km WSW).

Another explosion on 15 August 2018 was reported by SINAPRED that generated an ash plume to 200 m above the crater rim.

Seismicity. INETER monthly reports indicated that during September through December 2016, between 3,500 and 3,900 monthly seismic events took place, with the majority having hybrid signatures. During 2017, the monthly number of seismic events ranged from 40,584 (September) to 105,555 (November), of which 50-90% were hybrid events, 9-10% long-period events (but 23 percent in January), and 0-35% multiple events. A few scattered volcanic-tectonic events occurred, and tremor was usually low. Seismic data for January and March consisted of percentages of different earthquake types similar to those during 2017.

About 5% of the monthly seismic signals between April 2017 and January 2018 were doublets, or paired earthquakes with two predominant frequencies. INETER did not mention doublets in their March 2018 report, and did not include seismic data in their February or April 2018 reports.

Sulfur dioxide measurements. According to INETER, during fieldwork on 8 and 11 May 2017 the sulfur dioxide level was measured at 368 ± 194 metric tons/day. This value was lower than those in November 2015 with an average of 765 ± 94 tons/day. On 28 February and 1 March 2018, measurements using the Mobile-DOAS technique found levels greater than 426 tons/day and a minimum value of 152 tons/day, with an average of 260 tons/day, higher than the value measured in September 2017 with 183 tons/day. On 16 and 19 April 2018, the minimum and maximum values were 229 and 567 tons/day, with an average of 353 tons/day.

Geologic Background. Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately E, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Information Contacts: Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado Postal 2110, Managua, Nicaragua (URL: http://webserver2.ineter.gob.ni/vol/dep-vol.html); Sistema Nacional para la Prevencion, Mitigacion y Atencion de Desastres (SINAPRED), Edificio SINAPRED, Rotonda Comandante Hugo Chávez 50 metros al Norte, frente a la Avenida Bolívar, Managua, Nicaragua (URL: http://www.sinapred.gob.ni/).


Turrialba (Costa Rica) — September 2018 Citation iconCite this Report

Turrialba

Costa Rica

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

All times are local (unless otherwise noted)


Ongoing variable ash emissions and crater incandescence through August 2018

This report summarizes activity at Turrialba during January-August 2018. Activity became more constant after September 2014, with cycles of explosions with numerous, sometimes persistent, weak and passive ash plumes and emissions usually rising no more than 500 m above the active crater. This activity continued during this reporting period (table 7). Most of the data were provided by monthly bulletins of the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA) and alerts from the Washington Volcanic Ash Advisory Center (VAAC).

Table 7. Ash emissions at Turrialba, January-August 2018. Information was provided by OVSICORI-UNA, Washington VAAC, and RSN: UCR-ICE.

Date Time Max. Plume height above crater rim Drift Remarks
08 Jan 2018 0600 400-500 m NW --
08 Jan 2018 1319 400-500 m NE --
08 Jan 2018 2005 800 m SW --
09 Jan 2018 0630 300 m SW --
09 Jan 2018 1412 -- -- --
15 Jan 2018 0400 -- -- Ashfall in areas N of Pacayas (Pinos, Buenos Aires, and Santa Rosa de Oreamuno); sulfur odor noted in Santa Rosa de Oreamuno.
22 Jan 2018 0000 500 m NW --
26 Jan 2018 1101 100-200 m SW --
26 Jan 2018 1427 100-200 m SW --
30 Jan 2018 0920 100-200 m SW --
05 Feb 2018 0830 200 m SW --
06 Feb 2018 0730 1 km SW According to The Costa Rica Star, the activity continued for almost one hour; smaller explosion at 0832. Ashfall in several W-flank communities in San Jose (Goicoechea, Curridabat, Coronado) and Heredia.
27 Feb 2018 0800 100 m SW --
06 Mar 2018 2240 500 m NW Activity intensified around midnight with dense ash emissions and ejection of incandescent blocks, and remained elevated almost until 0300 on 7 March. At 1740 activity again intensified; emissions with increased ash volume occurred 1801-1820 drifting W.
08 Mar 2018 1515 300 m SW --
13 Mar 2018 0920 300 m NW --
23 Mar 2018 0605 100 m SW --
31 Mar 2018 1802 400 m SW --
01 Apr 2018 0838 500 m NW --
03 Apr 2018 0700 500 m NW --
05 Apr 2018 1230 500 m S --
09 Apr 2018 0609 300 m W --
11 Apr 2018 -- -- -- --
26 Apr 2018 0700 300 m W --
10 May 2018 -- -- -- Ashfall in La Pastora de Santa Cruz de Turrialba and Pacayas. No specific date: strong emissions of SO2, accompanied by vigorous fumarolic activity and jetting noises.
13 May 2018 0920 300-500 m -- Weak steam and gas, apparently no ash. Seismicity low, with low-amplitude long-period earthquakes and tremor. Continuous low-amplitude tremor.
21 May 2018 0900 -- -- --
28 May 2018 0930 300 m SE --
23 Jul-04 Aug 2018 -- 300 m NW, W, SW Series of weak, sporadic, and almost daily gas-and-ash emissions. On 24 July, ashfall in Coronado, Tibás (35 km WSW), Goicoechea (28 km WSW), Moravia (31 km WSW), and other areas in the Valle Central. On 31 July, ashfall in Tres Ríos (27 km SW). Sulfur odor occasionally reported.
02 Aug 2018 0023 1 km W --
02 Aug 2018 0700 300 m W --
04 Aug 2018 1600 300 m -- --
10 Aug 2018 -- -- W Pulsating, passive ash emissions. Strong sulfur odor in parts of Heredia (38 km W) and San José (36 km WSW) on 11 Aug.
27-28 Aug 2018 -- 200 m SW Continuous emissions.
30 Aug 2018 1340 200 m SW --
31 Aug-01 Sep 2018 -- 200 m SW, W Continuous gas-and-ash emissions.

According to an online news report (Q Costa Rica), a group of volcanologists called Volcanes sin Fronteras (Volcanos Without Borders) flew a drone over the volcano several times in December 2017 and first the two weeks of January 2018. On their Facebook page, they indicated that activity was dominated by intense degassing from the active crater, with sporadic explosions every 30-60 minutes, releasing gas and ash that rose to more than 300 m above the crater. They also observed phreato-magmatic explosions.

OVSICORI reported that pulses of ash emissions were common in January (figure 49), and incandescence was occasionally observed at night. Activity decreased after the middle of February, but strong incandescence was observed during early March.

Figure (see Caption) Figure 49. Webcam photo of an ash emission at Turrialba on 22 January 2018. Courtesy of Red Sismologica Nacional (RSN: UCR-ICE); published by the Costa Rica Star.

Eruptive activity resumed during the middle of May, but faded toward the end of the month to weak passive emissions, and finally ended. The volcano continued with a stable permanent Strombolian activity at the bottom of the crater. During June, the volcano was stable, with strong incandescence at night reflecting the presence of minor Strombolian activity that continued through at least early July.

On 3 July a weak explosion occurred and a thin layer of ash fell on the park ranger house and the Pica seismic station (2.5 km NW). A jet-like sound was heard on 4 July from a lookout. On 16 July incandescence continued at a low level. OVSICORI reported frequent weak ash emissions from 18 July through 2 August; the ash had a very low proportion of juvenile material and a high proportion of altered material. According to a news account (The Costa Rica Star) citing the RSN, persistent tremor accompanied these emissions, and a lahar descended the Toro Amarillo River on the W flank. Weak short-lived ash emissions resumed during the last half of August, and weak to moderate incandescence could still be observed.

Seismicity and deformation. During the first week of January, weak long-period (LP) earthquakes were recorded, but no volcanic-tectonic (VT) earthquakes or tremor. In February-April, weak VT earthquakes, a few LP earthquakes, and harmonic tremor were recorded. By May, seismic activity was almost non-existent, with VT signals below the crater and sporadic tremor. The latter disappeared by the end of May.

On 16 July, seismicity increased, particularly low-frequency earthquakes, to reach about 200 events the next day, but then decreased to normal on 18 July, with sporadic short tremor. During the last week of July, seismicity again increased until an internal explosion on 27 July, after which seismicity decreased. Tremor activity increased on 4 August, and by the middle of August, about 50 LP earthquakes per day were recorded, along with spasmodic tremor of low amplitude. This heightened activity continued during the following week.

Since June 2017, the volcano tended toward deflation, but then in early 2018 became stable until the middle of February, when inflation was recorded. By June, deformation was longer measured. No significant deformation was found in July or August.

Thermal anomalies. MODIS satellite instruments processed using the MODVOLC algorithm only recorded thermal anomalies on 22 March, 2 April, and 27 April (2 pixels). The MIROVA (Middle InfraRed Observation of Volcanic Activity) system recorded one hotspot during February, numerous hotspots between mid-March and mid-May, and only several hotspots after mid-May through the end of August. All recorded MIROVA anomalies were within 2.5 km of the volcano and of low radiative power.

Sulfur dioxide measurements. Significant sulfur dioxide levels near the volcano were recorded by NASA's satellite-borne ozone instruments between 30 March and 3 June, especially between 6-15 April.

According to OVSICORI, the CO2/SO2 ratio increased to a peak of 8 during the night of 21-22 January, then remained stable until the first week of February, when it decreased. By 20 February, the ratio was stable at about 4. The ratio was low during the middle of March, but rose on 29 March. On 10 April, the SO2 flow was normal (below 1000 t/d) and remained low until the middle of May, when CO2 levels increased. High CO2/SO2 levels were measured at the end of May, but decreased in early June. On 12 and 25 June, SO2 levels were about 400 and 500 tons/day, respectively. During early July, the ratio remained low at 4, with short periods of high measurements (about 10 on 5 July). The ratio remained stable throughout the rest of July. The ratio increased on 6 August during the last phase of eruptive activity, but then decreased to normal and stable levels for the rest of the month. Near the end of August, the two gas monitoring stations were vandalized.

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/); Red Sismologica Nacional (RSN: UCR-ICE), Universidad de Costa Rica and Instituto Costarricense de Electricidad (URL: http://rsn.ucr.ac.cr/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://hotspot.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/); Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (URL: https://sO2.gsfc.nasa.gov/); Costa Rica Star (URL: https://news.co.cr); Q Costa Rica (URL: https://qcostarica.com).

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements  Obituaries

Misc Reports

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

Additional Reports  False Reports