The ongoing eruption at Sheveluch continued during May-October 2020, characterized by lava dome growth, strong fumarolic activity, and several explosions that generated plumes of resuspended ash. Activity waned between November 2019 and April 2020 (BGVN 45:05), and this less intense level of activity continued during the reporting period (table 15). The volcano is monitored by the Kamchatka Volcanic Eruptions Response Team (KVERT). The Aviation Color Code remained at Orange (the second highest level on a four-color scale) throughout.

Notable explosions took place on 13 June, 28 June, 2 August, 24 August, and 7-9 October 2020 (table 15), sending ash plumes more than 1 km above the summit that drifted to distances of between 75 and 310 km. Some of the plumes were described by KVERT as being composed of re-suspended ash. On 28 September a large dacitic block of lava, a “whaleback” dome, was first seen being extruded from the eastern part of the larger lava dome in the summit crater (figure 55); it was given the name “Dolphin” by KVERT.

Table 15. Explosions, ash plumes, and extrusive activity at Sheveluch during May-October 2020. Dates and times are UTC, not local. VONA is Volcano Observatory Notice for Aviation. Data courtesy of KVERT and the Tokyo Volcanic Ash Advisory Center (VAAC).

Figure 55. Photo of the Sheveluch summit showing the new lava block (referred to as “Dolphin”) being extruded in eastern part the lava dome on 28 September 2020. Photo by Yu. Demyanchuk; courtesy of IVS FEB RAS, KVERT.

According to KVERT, a thermal anomaly was identified from the lava dome in the summit crater (figure 56) in satellite images every day during the reporting period, except for several days in August and September when weather clouds obscured the view. During the reporting period, thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, recorded hotspots from 2-13 days per month; after June, the number of days with hotspots gradually diminished every month. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected frequent anomalies. NASA recorded high levels of sulfur dioxide above or near Sheveluch during several scattered days in May and June by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite, but very little drift was observed.

Figure 56. Photo showing typical fumarolic activity from the lava dome at Sheveluch on 18 September 2020. Photo by Yu. Demyanchuk; courtesy of IVS FEB RAS, KVERT.

Geologic Background. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 km3 volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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/).

Erta Ale is an active basaltic volcano in Ethiopia, containing multiple active pit craters in the summit and southeastern caldera. Volcanism has been characterized by lava flows and large lava flow fields since 2017. This report describes continued thermal activity in the summit caldera during May through September 2020 using information from various satellite data.

Volcanism at Erta Ale was relatively low from May to early August 2020. Across all satellite data, thermal anomalies were identified for a total of 2 days in May, 7 days in June, 4 days in July, 11 days in August, and 15 days in September. Beginning in early June and into September 2020 the Sentinel-2 MODIS Thermal Volcanic Activity graph provided by the MIROVA system identified a small cluster of thermal anomalies in the summit area after a brief hiatus from early January 2020 (figure 99). By mid-August, a small pulse of thermal activity was detected by the MIROVA (Middle Infrared Observation of Volcanic Activity) system. Many of these thermal anomalies were seen in Sentinel-2 thermal satellite imagery on clear weather days from June to September.

Figure 99. A small cluster of thermal anomalies were detected in the summit area of Erta Ale (red dots) during June-September 2020 as recorded by the Sentinel-2 MODIS Thermal Volcanic Activity data (bands 12, 11, 8A). Courtesy of MIROVA.

On 12 June a minor thermal anomaly was observed in the S pit crater; a larger anomaly was detected on 17 June in the summit caldera where there had been a previous lava lake (figure 100). In mid-August, satellite data showed thermal anomalies in both the N and S pit craters, but by 5 September only the N crater showed elevated temperatures (figure 101). The thermal activity in the N summit caldera persisted through September, based on satellite data from NASA VIIRS and Sentinel Hub Playground.

Figure 100. Sentinel-2 thermal satellite imagery of Erta Ale on 17 June 2020 showing a strong thermal anomaly in the summit caldera. Sentinel-2 satellite image with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Figure 101. Sentinel-2 thermal satellite imagery of Erta Ale showing thermal anomalies in the N and S pit craters on 21 (top left), 26 (top right), and 31 (bottom left) August 2020. On 5 September (bottom right) only the anomaly in the N crater remained. Sentinel-2 satellite image with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. Erta Ale is an isolated basaltic shield that is the most active volcano in Ethiopia. The broad, 50-km-wide edifice rises more than 600 m from below sea level in the barren Danakil depression. Erta Ale is the namesake and most prominent feature of the Erta Ale Range. The volcano contains a 0.7 x 1.6 km, elliptical summit crater housing steep-sided pit craters. Another larger 1.8 x 3.1 km wide depression elongated parallel to the trend of the Erta Ale range is located SE of the summit and is bounded by curvilinear fault scarps on the SE side. Fresh-looking basaltic lava flows from these fissures have poured into the caldera and locally overflowed its rim. The summit caldera is renowned for one, or sometimes two long-term lava lakes that have been active since at least 1967, or possibly since 1906. Recent fissure eruptions have occurred on the N flank.

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

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 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 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 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 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 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 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 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 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 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, 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 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 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/).

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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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, 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.

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 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 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 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).

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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 104. A strong thermal anomaly was still present inside the newly enlarged summit crater at Nishinoshima on 19 August 2020. Courtesy of JCG.

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 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 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 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 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, 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 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 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 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 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 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 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 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 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 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 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 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 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.

Guatemala's Volcán de Fuego was continuously active throughout 2016, and has been erupting since 2002. Historical observations of eruptions date back to 1531, and radiocarbon dates are confirmed back to 1580 BCE. These eruptions have resulted in major ashfalls, pyroclastic flows, lava flows, and damaging lahars. Daily explosions that generated ash plumes to within 1 km above the summit (less than 5 km altitude) were typical. In addition, there were 16 eruptive episodes that included Strombolian activity, lava flows, pyroclastic flows, and ash plumes rising above 5 km altitude (BGVN 42:10). Lahars flowed down several drainages during January-June, August, and September. Similar activity continued during January-June 2017 and included five eruptive episodes and numerous lahars. In addition to regular reports from the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH), the Washington Volcanic Ash Advisory Center (VAAC) provides aviation alerts. Locations of many towns and drainages are listed in table 12 (BGVN 42:05).

Explosions with ash emissions continued daily at Fuego during January-June 2017; five episodes of increased activity generated higher ash plumes, lava flows, and pyroclastic flows (table 14). The first eruptive episode of the year occurred on 25-26 January, consisting of two lava flows and an 8.6-km-long pyroclastic flow. The next eruptive episode, during 24-25 February, also generated two lava flows and a 7-km-long pyroclastic flow. Numerous ash plumes during March rose to within 1 km of the summit, and incandescent blocks traveled more than 200 m from the crater, but no lava or pyroclastic flows were reported. Eruptive episode 3 began on 1 April and included three lava flows up to 2 km long, and an ash plume reported at 9.1 km altitude. Significant lahars affected four ravines near the end of the month. Pyroclastic flows affected five ravines during eruptive episode 4 during 4-5 May, along with two lava flows, 1.5 and 1.2 km long. The Washington VAAC reported an ash plume from this event at 12.2 km altitude. Major lahars occurred eight times during May, transporting blocks up to a meter in diameter down the major drainages. There were seven periods of increased activity during June. The period of activity during 5-6 June, designated Episode 5, generated two lava flows (2 and 3 km long) and a pyroclastic flow.

Table 14. Eruptive episodes at Fuego during January-June 2017. Data courtesy of INSIVUMEH and the Washington VAAC.

Activity during January 2017. The last eruptive episode (16) of 2016, during 20-21 December, included Strombolian activity that produced three lava flows, a large pyroclastic flow, and ashfall in villages 10-12 km SW (BGVN 42:10). VAAC reports indicated ash emissions visible as far as 230 km SW during the episode. Intermittent ash emissions and thermal alerts were reported during the rest of December as well. Activity increased during January 2017, with ash falling mostly on the S and SW flanks. INSIVUMEH reported Vulcanian explosions on 3 and 4 January which contained abundant ash and sent plumes to 5 km above sea level that drifted NW, W, SW, and S (figure 60). Ashfall was reported in Sangre de Cristo, San Pedro Yepocapa, Santa Sofia, Morelia, Palo Verde Farm, Panimache I and II, La Rochelle, San Andrés Osuna, Siquinalá and Escuintla. Sounds and shockwaves were heard and felt 8 km from the volcano.

Figure 60. Ash emission at Fuego on 4 January 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, ENERO 2017).

The Washington VAAC reported ash emissions at 4.3 km altitude (500 m above the summit) on 1 January extending about 35 km W of the summit early in the day. A second plume rose to 5.5 km and drifted a similar distance SE. A third ash plume a few hours later was spotted at 4.6 km altitude drifting W. By late in the day on 3 January, a broken plume of gas and ash was visible in satellite imagery 300 km SW. A well-defined plume on 4 January extended 90 km SW at 4.9 km altitude. Emissions rose to 5.8 km altitude on 5 January. Daily ash plumes during 2-8 January rose to 4.3-5.8 km and generally drifted W or SW up to 50 km. They also reported intermittent ash emissions in satellite imagery on 11 January, and visible in the webcam on 22 January.

The first eruptive episode of the year began on 25 January 2017 with constant explosions generating an ash plume that rose to 4.5 km altitude and drifted W and SW. Incandescence was visible 200 m above the crater, a lava flow traveled 1,000 m down the Ceniza canyon, and block avalanches descended the Ceniza and Trinidad ravines. Ash emissions later reached 5.5 km altitude and drifted W and SW more than 30 km. Strombolian activity ejected material 300 m above the crater and sent bombs more than 300 m from the crater. A second lava flow traveled down the Trinidad ravine later in the day. The Washington VAAC reported ash emissions during 25-28 January 2017 that rose to 4.6-5.5 km altitude extending over 200 km W. During the early morning of 26 January, a pyroclastic flow descended 8.6 km down the Ceniza canyon. INSIVUMEH estimated the volume of the flow to be over 11,000,000 m³ (figure 61). Extensive new pyroclastic flow deposits were observed filling parts of the ravine. A light layer of ash covered the vegetation in La Rochela as a result of the pyroclastic flow. INSIVUMEH reported ashfall in San Pedro on 26 January.

Figure 61. A pyroclastic flow at Fuego traveled 8.6 km down the Ceniza canyon during the early hours of 26 January 2017, part of the first eruptive episode of the year. The volume of the flow was measured by INSIVUMEH scientists as over 11,000,000 m3. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, ENERO 2017).

Activity during February 2017. An increase in activity on 2 February resulted in weak and moderate explosions that lasted 5-10 minutes and generated ash plumes that rose to 4.5 km altitude. The plumes drifted 15 km W and ashfall was reported in San Pedro Yepocapa and Sangre de Cristo. During 31 January-4 February the Washington VAAC noted several ash emissions (figure 62). They rose to altitudes ranging from 3.7-4.9 km and drifted S and W. Ash was visible 180 km SW on 2 February.

Figure 62. Ash emission at Fuego on 3 February 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, FEBRERO 2017).

On the morning of 24 February, eruptive episode 2 began with explosions and ash plumes rising to 4.6 km altitude and drifting W and SW. Explosions were heard by nearby residents every few minutes, and by the evening two lava flows were observed in the Santa Teresa and Las Lajas ravines. Incandescence reached 300 m above the crater and fell more than 300 m from the crater on the flanks, generating block avalanches. By the next morning ash plumes were observed at 5 km altitude drifting more than 25 km NW, N, NE and E. A pyroclastic flow descended the Trinidad ravine on the morning of 25 February, and traveled about 7 km. Ash on the SE flank was reported in El Rodeo, El Zapote, La Réunion, Alotenango, and San Vicente Pacaya (figure 63). On 25 February, the Washington VAAC reported large areas of dissipating ash moving in multiple directions. Ash emissions at 5-5.2 km altitude were drifting 65 km NE, at 5.8 km altitude they were drifting 130 km NE and also SE, at 6.4 km they were moving S, and another simultaneous plume was observed at 7.6 km drifting 30 km SW.

Figure 63. Ash dispersion map of the 24-25 February 2015 eruption episode 2 at Fuego. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, FEBRERO 2017).

Activity during March 2017. Daily weak and moderate explosions characterized activity during March 2017. Incandescence rose to 250 m above the crater and generated bombs and block avalanches that traveled more than 200 m from the crater (figure 64), but no new lava or pyroclastic flows were reported. INSIVUMEH reported an average of 17 explosions per day during the month, which generated ash plumes that rose to 4.4-4.9 km. Block avalanches were observed in the lower part of the Las Lajas ravine. Ashfall was reported in San Pedro Yepocapa, Sangre de Cristo, Palo Verde, Santa Sofía, Morelia, and Panimaché I and II. Three to six explosions per hour were recorded on 9, 10, 27, 29, and 31 March. The Washington VAAC reported ash emissions during 8-10, and 13 March. Plumes were observed rising to 4.6 km and moving W, 4.9 km moving S and SE, and 5.8 km drifting 80 km SE during these days. Lahars were reported on 17 and 21 March in the Las Lajas, Santa Teresa, and Ceniza ravines. The road to the village of La Rochela was cut off for a few days by the lahar in the Ceniza ravine.

Figure 64. Explosions generated ash plumes and block avalanches often during March 2017 at Fuego, including on 26 March in the early morning when this webcam image was taken. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, MARZO 2017).

Activity during April 2017. Persistent degassing during April sent steam emissions to 4.1-4.5 km altitude that dispersed in almost every direction, due to numerous changes in wind direction throughout the month. Weak to moderate Strombolian explosions created ash plumes that rose to 4.2-5.0 km and drifted primarily W and SW. Incandescence from the explosions was visible primarily at night and in the early morning around 100-300 m above the crater. The explosions also generated block avalanches that traveled more than 300 km from the summit. There were two spikes in explosive activity during April. The first, on 1 April, led to eruptive episode 3. The second, on 21 April, was less intense. These periods averaged 5-7 explosions per hour with ash plumes rising to 4.6-4.9 km and drifting in various directions.

Eruptive episode 3 began around midday on 1 April 2017, with Strombolian explosions that produced ash plumes up to 5 km that drifted more than 30 km NW, W, and SW; it lasted for about 16 hours. Ash fell in Sangre de Cristo, San Pedro Yepocapa, Santiago Atitlán, Chicacao, Mazatenango, and Retalhuleu. Lava flows traveled down the Las Lajas, Santa Teresa and Trinidad ravines as far as 2 km. The eruption was categorized by INSIVUMEH as a VEI 2 event with moderate to strong Strombolian explosions. The Washington VAAC reported an ash plume on 1 April that rose to 6.4 km altitude. The densest part of the plume was moving NW with some material fanning out to the NNE. They later revised their report with information that a new emission had risen to 9.1 km altitude and drifted NE. Ash emissions continued the next day with plumes moving NNW at 5.5 km and NNE at 8.2 km; bright incandescence appeared at the summit along with elevated seismicity. By the end of 2 April, the higher plume was diffuse as it dissipated over the far western Caribbean of the coast of Belize and Yucatan.

The Washington VAAC reported an ash emission to 4.5 km altitude on 21 April that extended 30 km NE of the summit. Occasional puffs of ash continued throughout the day and rose to 4.9 km altitude later in the day. By the next day, a plume was visible at 4.6 km extending 80 km E; it was later reported at 4.9 km altitude. By 23 April a faint plume extended 90 km S before dissipating. INSIVUMEH also reported ashfall in Palo Verde Farm, Santa Sofía, Morelia, and Panimaché I and II other times during the month.

Significant lahars affected several ravines on 20, 23, and 24 April 2017. Rain, hail and snowfall caused a lahar in Ceniza Canyon on 20 April (figure 65). On 23 April, lahars flowed down the Santa Teresa, Trinidad, Ceniza and Las Lajas ravines after 160 mm of rainfall in three days. These ravines are tributaries of the larger Pantaleón, Achíguate, and Guacalate rivers. Another lahar on 24 April in Ceniza Canyon was audible more than 1 km from the ravine.

Figure 65. View of Fuego after an intense rain and hailstorm on 20 April 2017 that caused a lahar in Ceniza Canyon. Photo by Francisco Juarea, courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, Abril 2017).

Activity during May 2017. Eruptive episode 4 began on 4 May 2017. A lava flow on the NE flank descended the Seca ravine for 1,500 m (figure 66). Explosions increased to 5-7 per hour, and were visible 200 m above the summit. Another lava flow descended 1.2 km down the Las Lajas ravine. Pyroclastic flows descended Barranca Seca, filling the channel and overflowing to the SE into Rio Mineral. They also affected Ceniza, Trinidad, El Jute, and Las Lajas canyons (figure 67) raising the imminent threat of lahars in these drainages. INSIVUMEH estimated that 14 million cubic meters of material was emplaced from the pyroclastic flows.

Figure 66. A lava flow descends the Barranca Seca at Fuego on 4 May 2017 during eruptive episode 4. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, Mayo 2017).

Figure 67. Pyroclastic flows descend several drainages on the SE slope of Fuego on 5 May 2017 during eruptive episode 4, as viewed from la Finca la Reunión. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, Mayo 2017).

INSIVUMEH reported ash emissions during this episode as high as 6 km altitude. The ash dispersed S, SW, W and NW, and ashfall was reported in communities more than 25 km from the crater (figure 68). Energy levels decreased after about 24 hours. INSIVUMEH characterized the event as a VEI 3 eruption. The Washington VAAC was unable to observe the activity in satellite imagery due to cloud cover until the morning of 5 May, when they reported ash plumes moving SW at about 4.6 km altitude and also ENE at 5.5 km altitude. They reported a new, much higher ash plume midday on 5 May at 12.2 km altitude that was drifting E at about 50 km per hour, in addition to the lower level emissions around 4.6 km that drifted SW which generated ashfall in the immediate vicinity of the volcano. The Washington VAAC reported another ash emission on 7 May that rose to 4.9 km altitude and drifted SW about 10 km from the summit. Another plume appeared in satellite imagery the next day moving SW at 4.6 km about 15 km from the summit. The Washington VAAC reported no additional plumes until 31 May when satellite imagery showed a plume with possible ash extending about 25 km NE from the summit at 4.9 km altitude. Ashfall was reported during the month in Morelia, La Rochela, Santa Sofia, Sangre de Cristo, Palo Verde farm, Panimache I and II, San Pedro Yepocapa and Escuintla.

Figure 68. Ashfall from eruptive episode 4 at Fuego during 4-5 May 2017 was reported in communities more than 25 km from the volcano, and dispersed S, SW, W, and NW. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, Mayo 2017).

Moderate and strong lahars were recorded on six days in May (figure 69). Five took place in Seca barranca (13, 14, 19, 23, and 27 May), one in the Ceniza ravine (14 May), and two in Las Lajas canyon (both on 29 May). They transported very fine-grained material that had the consistency of wet concrete, and included blocks up to one meter in diameter.

Figure 69. A vehicle trapped in a lahar at Fuego in May 2017 surrounded by blocks as large as one meter in diameter. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, Mayo 2017).

Activity during June 2017. Weak and moderate daily explosions continued at Fuego during June 2017. They generated ash plumes that drifted more than 12 km, incandescence and block avalanches, and ashfall more than 30 km NW, W, and SW. Numerous lahars were also reported. The 20-25 daily explosions generally sent ash plumes to 4.2-4.5 km altitude that drifted mostly W and SW. The incandescence from Strombolian explosions generally extended 150-200 m above the crater (figure 70). Ashfall from these events was reported in in Morelia, Santa Sofia, Sangre de Cristo, La Rochela, and Panimache I and II.

Figure 70. A Strombolian explosion on 30 June 2017 at Fuego reached 150-200 m above the crater and sent avalanche blocks down the flanks. This was typical behavior for the month of June. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, Junio 2017).

There were seven periods of increased explosive activity during June 2017 (table 15), including eruptive episode 5. Many of the increases in energy levels were observed in the seismic record (figure 71) and reported by OVFGO (the Fuego Volcano Observatory). They noted an average of 5-8 explosions per hour during these events, and ash emissions rising to 4.6-4.9 km altitude, drifting W, SW, and S. None of the ash plumes reported by INSIVUMEH were observed by the Washington VAAC in satellite imagery due to weather clouds. The Washington VAAC did observe bright hotspots in shortwave imagery on 6 June.

Table 15. Periods of increased eruptive activity at Fuego during June 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, Junio 2017).

Figure 71. RSAM graph for Fuego during June 2017 shows spikes in seismic energy caused by eruptive episode 5 (red arrow), increases in explosive activity (yellow arrows), and several lahars (blue arrows). Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, Junio 2017).

Eruptive episode 5 for 2017 began during the late afternoon of 5 June. Moderate and strong Strombolian explosions generated an ash plume that rose to 6 km altitude and drifted more than 20 km W, SE, and NW from the crater. Sounds as loud as a freight train were reported nearby, and vibrations were felt in communities around the volcano. Lava flowed 3 km down the Santa Teresa ravine and 2 km down Ceniza canyon. Volcanic bombs rose 200 m high, and fell more than 300 m from the summit crater. Pyroclastic flows descended the Santa Teresa canyon on the W flank.

Thirteen lahars were reported during June (table 16). They descended the Santa Teresa, Mineral, Trinidad, Ceniza, Las Lajas, and El Jute ravines, tributaries of the Pantaleón, Achíguate and Guacalate rivers. Overflows from the drainages damaged several roads and river crossings in the region.

Table 16. Lahars at Fuego during June 2017. Courtesy of INSIVUMEH (INFORME MENSUAL DE LA ACTIVIDAD DEL VOLCÁN DE FUEGO, Junio 2017).

Satellite thermal data. The eruptive episodes reported by INSIVUMEH at Fuego during 2016 and the first half of 2017 are readily apparent in the MIROVA Log Radiative Power thermal data, and are also present going back at least to mid-2015 (figure 72). INSIVUMEH reported new lava flows and Strombolian activity each time (except for 2016 episode 8), which were the likely sources of the pulses of thermal activity. Details of the eruptive episodes for 2016 are discussed in BGVN 42:10 and 42:06.

Figure 72. MIROVA thermal anomaly graphs of MODIS infrared satellite data spanning 5 February 2015-19 September 2017 illustrating the recurring nature of eruptive episodes at Fuego. INSIVUMEH described 16 episodes during 2016, and five episodes during January-June 2017, shown as numbers over the red arrows. Episode 8 for 2016 is not shown; it was primarily a pyroclastic flow which did not generate the same thermal signal caused by lava flows during the other episodes. Courtesy of MIROVA.

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/).

Recent activity at Karymsky has consisted of ash explosions and thermal anomalies, often separated by several months of quiet (BGVN 40:09 and 42:08). No ash explosions occurred between the middle of October 2016 and the end of May 2017 (BGVN 42:08). This report covers activity from June through November 2017 using information compiled from the Kamchatka Volcanic Eruptions Response Team (KVERT), the Tokyo Volcanic Ash Advisory Center (VAAC), and several sources of satellite data.

After months of quiet, KVERT reported that, based on Tokyo VAAC data, an ash explosion began at 0040 (local time) on 4 June 2017 (table 10). The Aviation Color Code (ACC) was raised from Green (lowest level on a four-color scale) to Orange (the second highest level). Subsequent ash explosions occurred on 8 June, 26 June and 18 July (figure 1).

Table 10. Summary by month of ash plumes and thermal anomalies reported for Karymsky during 2016. Details include UTC dates of thermal anomalies and ash plumes; and maximum plume altitude, and maximum distance of ash plume drift. Sources are KVERT and Tokyo VAAC for ash plume data, and KVERT for thermal data.

Figure 37. Aerial photo of an ash explosion at Karymsky on 18 July 2017. Courtesy of A. Belousov (IVS FEB RAS).

Toward the end of August, KVERT noted only gas-and-steam emissions, and the ACC was lowered to Yellow (the second lowest level on a four-color scale) on 30 August. This diminished activity continued until 20 September, when ash explosions at 0420 (local) prompted KVERT to raise the ACC back to Orange.

After 20 September, the volcano was either obscured by clouds or relatively quiet. After 11 October the moderate activity was associated with gas-steam emissions. On 19 October, the ACC was lowered to Yellow and then to Green (lowest level) on 26 October. Gas-and-steam activity continued through the end of November.

Thermal anomalies. Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were not observed at Karymsky during the reporting period, except for a possible hotspot on 8 June 2017 that was slightly E of the craters. The MIROVA system detected at least nine days with low to moderate power hotspots in June, two in July, and one in August, all of which were within 3 km of the volcano. No hotspots were recorded September through November 2017.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/).

A submarine volcano located about 8 km off the N coast of Grenada, Kick 'em Jenny most recently had erupted during 23-24 July 2015 (BVGN 40:08), when two submarine explosions had been detected. This report covers a short-lived eruption on 29 April 2017 as reported by the Seismic Research Centre (SRC) at the University of the West Indies (UWI).

An advisory notice issued on 29 April 2017 by the Grenada National Disaster Management Agency (NaDMA) in collaboration with UWI-SRC reported increased seismicity associated with the volcano, including a high-amplitude signal lasting 25 seconds. The notice advised marine operators to strictly observe a 5-km maritime exclusion zone (figure 10). Another NaDMA notice on 3 May set the alert level at Yellow, indicating that all vessels should observe the 1.5 km exclusion zone, though as a precaution remaining outside the 5-km zone was recommended.

Figure 10. Map showing the two maritime exclusion zones defined at Kick 'em Jenny, north of the island of Grenada. Courtesy of NaDMA.

As described by Latchman et al. (2017) in an SRC Open File report on 11 July 2017, subsequent eruptive activity on 29 April 2017 consisted of one event which lasted 14 minutes, followed by about an hour of tremor. The period of unrest began on 8 April with one earthquake. On the days following that first event, and prior to the eruption, there were 0-2 daily volcano-tectonic earthquakes, with 16 in all leading up to the eruption. The eruption was felt in northern Grenada and Martinique as an extended period of shaking, and very high-amplitude T-phases were recorded in Montserrat. There was no surface activity observed. After the eruption there was a sharp increase in the number of hybrid seismic events, with an additional 84 events up to 2 May, after which the activity ceased (figure 11).

Figure 11. Seismicity associated with the 2017 period of unrest at Kick 'em Jenny plotted as a daily count during 1 April through 15 May (top) and as an hourly count during 24 April-1 May 2017 (bottom). From Latchman et al. (2017); courtesy of University of the West Indies, Seismic Research Centre.

According to UWI-SRC, the 2017 precursory seismicity was low level, the eruption occurred without intensification of the seismicity, and the post-eruption seismicity was relatively abundant, but short-lived. This volcanic episode came just 21 months after an episode consisting of two weeks of precursory seismicity, two hour-long eruptions on 23 and 24 July, and rapid decay of post-eruption seismicity.

Reference: Latchman J, Robertson R, Lynch L, Dondin F, Ramsingh C, Stewart R, Smith P, Stinton A, Edwards S, Ash C, Juman A, Joseph E, Nath N, Juman I, Ramsingh H, Madoo F, 2017, 2017/04/29 Eruption of Kick-'em Jenny Submarine Volcano: SRC Open File Report Kick-'em-Jenny, Grenada 201706_VOLC1, Seismic Research Centre, The University of the West Indies, St. Augustine, Trinidad, West Indies.

Geologic Background. Kick 'em Jenny, a historically active submarine volcano 8 km off the N shore of Grenada, rises 1300 m from the sea floor. Recent bathymetric surveys have shown evidence for a major arcuate collapse structure, which was the source of a submarine debris avalanche that traveled more than 15 km W. Bathymetry also revealed another submarine cone to the SE, Kick 'em Jack, and submarine lava domes to its S. These and subaerial tuff rings and lava flows at Ile de Caille and other nearby islands may represent a single large volcanic complex. Numerous historical eruptions, mostly documented by acoustic signals, have occurred since 1939, when an eruption cloud rose 275 m above the sea. Prior to the 1939 eruption, which was witnessed by a large number of people in northern Grenada, there had been no written mention of the volcano. Eruptions have involved both explosive activity and the quiet extrusion of lava flows and lava domes in the summit crater; deep rumbling noises have sometimes been heard onshore. Historical eruptions have modified the morphology of the summit crater.

Information Contacts: Seismic Research Centre (SRC), The University of the West Indies (UWI), St. Augustine, Trinidad and Tobago, West Indies (URL: http://www.uwiseismic.com/); National Disaster Management Agency (NaDMA), Fort Frederick, Richmond Hill, St. George's, Grenada, West Indies (URL: http://nadma.gd/).

Hawaii's Kilauea volcano continues the long-term eruptive activity that began in 1983 with lava flows from the East Rift Zone (ERZ) and a convecting lava lake inside Halema'uma'u crater. The US Geological Survey's (USGS) Hawaii Volcano Observatory (HVO) has been monitoring and researching the volcano for over a century, since 1912. HVO quarterly reports of activity for January-June 2017, by HVO scientists Lil DeSmither, Tim Orr, and Matt Patrick, form the basis of this report. MODVOLC, MIROVA, and NASA Goddard Space Flight Center (GSFC) provided additional satellite information of thermal anomalies and SO₂ plumes.

The lava lake level inside Halema'uma'u crater continued to rise and fall periodically during January-June 2017. The lava continued to circulate, and periodic rockfalls and veneer collapses caused small explosions within the lake. A few pieces of lapilli and minor ash landed at the Jagger Overlook. There were no major changes at the Pu'u 'O'o crater during the period; only minor fluctuations occurred in the lava pond lake level, and periodic rockfalls briefly disturbed the pond surface. There were, however, many surface breakouts along almost the entire length of the episode 61g lava flow from near the base of Pu'u 'O'o all the way to the Kamokuna ocean entry, about 12 km S. After the collapse of a large part of the delta at the Kamokuna ocean entry on 31 December 2016, lava continued to pour into the sea, and a new submarine delta began to grow. Instability of the sea cliff led to fractures and additional collapses during January and February. By the end of March, a small new delta was again visible above sea-level. It collapsed into the sea on 3 May, but another new delta quickly began to grow and reappeared by the end of the month. The "firehose" solidified and formed a ramp to the delta; surface flows caused thickening of the delta through the end of June.

Activity at Halema'uma'u. The lava lake inside 1-km-wide Halema'uma'u crater at Kilauea's summit was relatively quiet during the first half of 2017. It is located within the 200-m-wide "Overlook crater" at the SE edge of Halema'uma'u. The lava lake level rose and fell in reaction to typical summit pressure changes, as reflected in numerous deflation-inflation (DI) events. The rise and fall of the lake level generally took place over the course of several hours to days. At its highest level, the lake was 9 m below the floor of Halema?uma?u crater on 4 January 2017. Two weeks later, the lake dropped to its lowest level measured, 52.5 m, on 17 January. It was at a very similar height again, 52 m below the rim, on 23 June. There were two unusually large, fast drops in the lava lake level during June. The first, from 13 to 14 June, was a drop of 24 m in 24 hours. The second was a drop of 30 m over two days (21 to 23 June), which was the greatest single drop in lava level since mid-January.

The circulation pattern of the lava lake surface remained consistent, upwelling from the north end of the lake and migrating to the southern edge (and the southeast sink) where the crust descended. Short-lived spatter sources around the lake, generally caused by a disruption of the lake surface (e.g., rock falls), would temporarily (and sometimes only locally) redirect the lake surface towards the spatter source. Seismic tremor levels fluctuated along with spattering intensity. During much of the second quarter of 2017, spattering in the southeast sink was located inside of a large grotto with stalactites hanging from the roof.

The rockfalls and veneer collapses from January through June were not large enough to trigger any significant explosions, but there were several smaller events. The first, observed on 9 January at approximately 1320, occurred during Kona winds (stormy, rain-bearing winds that blow over the islands from the SW or SSW, in the opposite direction of the normal trade winds). It did not produce an explosive deposit or excessive amounts of tephra in the collection buckets near the Halema?uma?u Overlook and parking lot (500 m S of active lava lake), but did send ash and at least one 2-3 mm lapillus to the Jaggar Overlook and parking lot (about 1.8 km NW of the lava lake), and generated a composite seismic event. Composite events were also triggered on 14 January (2250) when a large piece of veneer collapsed off the northern crater wall, and on 16 January (1524) after a small rockfall from the southern inner edge of the Overlook crater (the smaller crater inside Halema?uma?u that contains the lava lake). On 23 March at 0036, a slice of the Overlook crater's southern ledge collapsed into the lake, triggering brief spattering and another composite event. On 26 May at 1114 HST, a piece of the northern Overlook crater wall collapsed into the lake (figure 281). This triggered a composite seismic event, lake surface agitation and spattering, and produced a dusting of ash on the cars in the HVO parking lot (at the Jaggar Overlook). Other veneer, grotto, and ledge failures often triggered brief spattering, localized subsidence of the crust, and composite seismic events.

Figure 281. Webcam image from the HMcam on the rim of the Overlook crater at Kilauea on 26 May 2017 at 1116 HST, less than two minutes after a collapse, showing the agitated lava lake surface. A large chunk from the northern crater wall, directly above the active spattering, fell into the lake, which triggered spattering and a composite seismic event. The area of the wall that collapsed is discernible above the spatter by the newly exposed wall rock that is lighter in color. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for April - June 2017).

Activity at Pu'u 'O'o. There were no major changes in Pu'u 'O'o crater during the first half of 2017, and there was still an active lava pond in the West pit at the end of June (see figure 258, BGVN 41:08 for detailed crater map). The pond level appeared to be relatively steady, ranging from 19 to 21 m below the pit rim (849-851 m elevation), and the pond diameter ranged from 43 m in March to 47 m at the end of May. A time-lapse camera looking into the West pit lava pond, which was installed on 16 March, revealed a few rockfalls and collapses. The pond surface was completely disturbed on 18 April at 0809 HST and again on 20 May at 2304; overnight on 4-5 May a talus deposit appeared on the pit floor, suggesting rockfalls. On 31 May a ledge just above the West pit lava pond surface, representing the pond level from a few months prior, had a pile of rubble from a portion of the east wall collapsing.

Summary of episode 61g breakouts. Throughout the first half of 2017, there were many active surface breakouts along almost the entire length of the episode 61g flow field (figure 282). Near the 61g vent, a new breakout started on 22 January, which traveled along the southern margin of the flow field before it stopped on the morning of 9 February. The breakout that had started on 21 November 2016, also ended on 9 February, possibly because the system was starved of supply after a week and a half of deflation. A new breakout began on the upper part of Pulama Pali on 10 February that lasted through early April. Two breakouts appeared in the Royal Gardens subdivision on 15 February and 1 March, each lasting a few weeks. During the day of 5 March, a breakout began approximately 1.3 km downslope of the vent that remained weakly active on the upper flow field through the end of June. Two new breakouts started in mid-June that were also active through the end of the month.

Figure 282. Map of the episode 61g flow field at Kilauea produced on 10 July 2017, showing the flow margin expansion (red) since 30 March 2017. During this time, the flow field expanded an additional 183 hectares from the previous 846 hectares (as of March 30), to a total of 1,029 hectares, increasing the flow field area by 22 percent. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for April - June 2017).

Details of episode 61g breakouts. On 10 February 2017 around 0710 a new breakout was reported on the steep part of Pulama Pali on the western flow field; by the next day pahoehoe surface flows were advancing across the coastal plain. Incandescence from the surface breakouts on the pali was only visible for the first few days, but the breakout continued to feed the surface flows on the coastal plain. By 14 February the flows had advanced approximately 2.3 km from the base of the pali (about 1.2 km from the coast), and by 25 February the flow was approximately 660 m from the ocean. These sluggish pahoehoe flows were largely outside the National Park boundary as they widened the eastern edge of the 61g flow margin. The flow advanced to within approximately 300 m of the road (500 m from the ocean) by 2 March. Breakouts then opened on the upper half of the coastal plain around 7 March, remaining weakly active through the end of March. On 8 April, tiny remnant surface flows from the breakout were found on the coastal plain. The spiny pahoehoe was 500 m out from the base of the pali and 2.8 km from the ocean, but the breakout was confirmed by thermal images to have ended by 10 April.

There were two breakouts that began near the top of Royal Gardens subdivision, on 15 February and 1 March 2017. The first started during the day, with glow visible in the R3cam at sundown. By 18 February the breakout was visible from the HPcam on the steep part of Pulama Pali, and remained active on the pali until the evening of 12 March. The 1 March breakout began higher upslope, with incandescence visible at sundown. This breakout slowly advanced and after a few days could not be seen from the webcam. Thermal images from 16 March indicated that the flow was no longer active.

During the day of 5 March 2017, a breakout began approximately 1.3 km downslope of the episode 61g vent (visible in the R3cam). By the middle of March, this was the most active breakout on the flow field, with surface activity expanding both sides of the flow field, and ranging between approximately 2 and 3.5 km from the vent. It was visible from the FEMA emergency road on 28 April on the upper pali. There was very little advancement over the next few weeks, until it reached the top of the steep part of the pali on 17 May. By 23 May, the sluggish pahoehoe flow front was approximately 400 m out from the base of the pali, and there were many small pahoehoe and aa channels on the steep pali face. Four days later (27 May), there were still breakouts on the pali, and the flow front had advanced another 100 m along the western margin of the 61g flow field. Satellite imagery from 2 June showed the breakout was still active, but by 13 June no activity was found on the coastal plain, and thermal imagery showed no active breakouts on 21 June. The 5 March breakout remained weakly active on the upper flow field (above the pali) through the end of June.

Two new breakouts started in June 2017, and remained active through the end of the month. The first started around 0600 HST on 13 June (figure 283), approximately 1.1 km from the episode 61g vent, located just upslope of the 5 March breakout point. These surface flows quickly became the most active along the 61g flow field. The second breakout originated from the upper pali (near the top of Royal Gardens subdivision) during the day of 26 June, and advanced down the pali east of the main flow field, reaching the base during the night of 4 July.

Figure 283. The 13 June breakout point approximately 1.1 km from the 61g vent, along the tube system at Kilauea. The breakout uplifted (about 2 m) and cracked the older flow (center) as it pushed its way to the surface and oozed through the cracks in multiple locations around the central uplifted area. Photo by L. DeSmither on 21 June 2017. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for April - June 2017).

Activity at Kamokuna ocean entry. After the ten hectare (25 acre) delta and sea cliff collapse on 31 December 2016, the ocean entry consisted of a single vigorous lava stream (informally called "the firehose") entering directly into the ocean from the episode 61g lava tube; it was located 21 m above the water (figure 284). Interactions between the lava and sea water produced a single robust plume and sporadic littoral explosions that threw spatter up to roughly 30 m above the top of the sea cliff. Spatter from these explosions fell on the cliff adjacent to the ocean entry, and began to build a littoral cone that was first noticed on 28 January on the cliff's edge. The sea cliff in the immediate area and downwind of the ocean entry was blanketed in a layer of Pele's hair and Limu o Pele (Pele's seaweed) which fell from the plume and added to the ground cover as the firehose continued.

Figure 284. Lava pours into the ocean at the Kamokuna ocean entry at Kilauea. Left: "The firehose" on 28 January 2017 exits the tube as a wide, thin sheet in this photo taken from the nearby observation point. Right: By 1 February, the lava stream changed to a cylindrical hose shape. Photos by M. Patrick, courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for January – March 2017).

A discolored water plume was visible at the ocean entry flanking an area of darker water directly out from the entry point, on either side. Thermal images taken in mid-March 2017 indicated that the discolored area was also heated, with the anomalous area extending out about one kilometer (figure 285).

Figure 285. Photo and thermal images taken of the Kamokuna ocean entry at Kilauea during a 30 March 2017 overflight. Left: Photo of the ocean entry and distinct plumes of steam and discolored water (photo by L. DeSmither). Right: A thermal image showing the heated water plume with the small area of cool water directly in front of the ocean entry. The hot material spread horizontally along the base of the sea cliff directly in front of the ocean entry, is the newly forming delta. On the 61g flow field (upper right), two small breakouts are visible on the coastal plain near the base of Pulama Pali, and the 5 March breakout (top-center), is discernable on the upper flow field near Pu'u 'O'o. Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for January - March 2017).

Many large ground cracks were noticed in the sea cliff inland from the entry after the 31 December 2016 Kamokuna delta collapse, including a set of en echelon cracks at the edge of the old sea cliff where over 1.6 hectares (about 4 acres) had collapsed. On a 25 January 2017 overflight, thermal images revealed a hot crack parallel to the sea cliff and a corresponding collapse pit on the trace of the lava tube, suggesting major instability. A few days later (28 January) the crack was measured at 30 cm wide, up to 220°C, was visibly very deep, and the seaward side of the crack was sloping slightly towards the ocean (figure 286). HVO scientists could also occasionally feel slow ground shaking at an observation point 240 m east of the ocean entry. When measured again (in the same spot) on 1 February, the crack was 75 cm wide. Upon further examination, grinding noises were coming from the crack and the seaward side of the crack was visibly swaying about 1 cm.

Figure 286. Photos of the large ground crack near the Kamokuna ocean entry at Kilauea, with yellow arrows pointing out two distinctive flow edges for comparison. Left: A photo taken on 28 January 2017 (by M. Patrick), when the crack was measured at 30 cm wide (just above the lower arrow). Right: Photo taken on 2 February, after a large portion of the sea cliff collapsed into the ocean, the crack measured 100 cm (photo by T. Orr). Courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for January - March 2017).

On the morning of 1 February around 0735, a small collapse of the sea cliff was reported near the firehose. The next day, the firehose was no longer visible from the observation point (possibly due to erosion of the sea cliff), but sporadic littoral explosions were still occurring. HVO personnel returned to the crack (which had begun steaming) for observations and to record video of the cliff oscillating. At 1255, about 30 seconds after the camera began to record, the seaward slab of the crack began to fall away. After the collapse only a small piece of the slab remained, and the crack measured 100 cm in width, 25 cm more than the previous day, most of which occurred during the collapse and in the few minutes following (figure 286). By 8 February, the remaining slab of cliff was gone, one piece collapsed at 1507 on 2 February, and the rest collapsed sometime between 6 and 8 February. The littoral cone that had been building on the edge of the cliff fell in with the collapse, but by 8 February, another had formed on the new sea cliff edge above the ocean entry.

During January, the firehose exited the tube as a thin broad sheet, but by the end of the month had changed into a cylindrical stream (figure 284). The output amount slowly began to wane, and on 8 March the ocean entry plume shut off for about 30 minutes between 1616 and 1646 with only a little puff of steam visible in between. The plume shut off briefly again several times on 18, 19, and 20 March for periods up to about 90 minutes in length.

From January through March 2017, the firehose continued with no sign of a delta forming, which suggested steep bathymetry below the ocean entry. By 22 March, the firehose was no longer visible from the public viewing area but incandescence was visible near the water surface, suggesting that the firehose was becoming encased in lava and a small delta was finally beginning to form. On 24 March, there were few, if any, littoral explosions, and the thick plume at the ocean entry made it impossible to see any signs of a delta, but time-lapse images verified the formation of one. There were many floating, steaming blocks in the water offshore of the entry. An overflight on 30 March showed a thick haze that was obscuring the small delta at the base of the cliff, where only brief tiny spots of incandescence could be seen near the water's surface. Images from a thermal camera indicated hot material from the delta extending approximately 60 m east along the cliffs base at the ocean entry.

By the end of March 2017, the firehose flow activity was no longer visible and a tiny new delta began to form. On 8 April, the delta was estimated to be extending roughly 25 m out from the base of the sea cliff (using cliff height for scale). A sparse field of dense angular blocks were deposited on 25 March between 0803 and 0808 HST on the sea cliff near the ocean entry, which covered an area of approximately 70 x 70 m (the largest block observed was 50 cm across).

During the first half of April the small delta was mostly obscured by the ocean entry plume. By the end of the month, the delta size was estimated to be 1.2 hectares (roughly 3 acres, using time-lapse images). On 3 May, nearly the entire delta collapsed between 0955 and 1000 HST, following a large steam plume and weak spattering from one of the cracks on the delta, along with delta subsidence in the preceding 20 minutes before the collapse. Many small pieces of the remnant delta fell off over the next few hours.

The delta quickly began to rebuild after the collapse, and on 23 May coast-parallel cracks were apparent on the new delta. The tubed-over firehose created a ramp-like feature near the cliff face where the 61g tube exited the older sea cliff (figure 287). This ramp was narrow at the point where the tube exits the cliff, and flared out as it reached the surface of the delta, insulating the 61g lava on its way to the delta. Near the top of the ramp there was an area of concentrated degassing, and evident cracks in the ramp revealed incandescence. On 16 June, surface flows on the delta covered a large portion of the surface, including the coast-parallel cracks so they were no longer visible.

Figure 287. A view of the crusted over firehose ramp on 29 June 2017 at the Kamokuna ocean entry of Kilauea where the 61g lava tube exits the sea cliff and feeds the ocean entry from an established tube on the delta. On the west (left) side of the ramp, there are cracks in the crusted surface where delta surface flows likely originated that show incandescence beneath. Photo by L. DeSmither, courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for April - June 2017).

Time-lapse images from 25 June revealed that firehose activity returned briefly between 1139 and 1149 HST, and produced channelized surface flows that continued into the following day (when a skylight was visible on the delta). The delta had grown to approximately 2.4 hectares (6 acres) by 29 June (figure 288), and had also thickened significantly from the recent surface flows on the delta. Much of the delta surface was covered by the repeated surface flows, but there was still a coast-parallel crack visible on the western side.

Figure 288. The lava delta at Kamokuna ocean entry at Kilauea on 23 May 2017 (left) and 13 July 2017 (right) showing the thickening of the delta near the cliff face caused by repeated small surface flows. These flows appear to have doubled the thickness of the delta and created a distinctly sloped surface from the base of the cliff to the sea. Photos by L. DeSmither, courtesy of HVO (Hawaiian Volcano Observatory Quarterly Report for April - June 2017).

Satellite thermal anomaly and SO₂ data. Satellite thermal anomaly data for Kilauea can be closely correlated with ground-based observations by HVO scientists, thus providing validation of remote-sensing data. The MODVOLC thermal alert system captured distinct anomalies during January-June 2017 from Halema?uma?u Crater, Pu'u 'O'o Cone, the episode 61g flow, and the Kamokuna ocean entry (figure 289). The changes from month to month in the locations of the hotspots, especially the locations of the breakouts of episode 61g flow, are readily apparent in the MODVOLC images, and match the descriptions of these events provided by HVO scientists.

Figure 289. Thermal alerts identified by the MODVOLC system by month at Kilauea, January-June 2017. The thermal anomaly signatures of the lava lakes at Halema'uma'u crater and Pu'u 'O'o crater persist throughout the period; while the changes in the locations of the thermal anomalies of the episode 61g flow and the Kamokuna ocean entry closely match ground observations by HVO staff, described in the text. Courtesy of HIGP - MODVOLC Thermal Alerts System .

The MIROVA thermal anomaly information, which plots Middle InfraRed Radiation from the MODIS data, also shows the locations and movements of the sources of heat at Kilauea over time (figure 290), and this information correlates closely with ground observations by HVO staff. Note that the MIROVA center point for relative distances described here is about 10.5 km (0.1°) E of the summit on the western Halema'uma'u crater rim. The anomaly locations at about 10 km distance correspond to both the lava pond at Pu'u 'O'o crater and the Halema'uma'u crater lava lake. Those about 20 km away correspond to the Kamokuna ocean entry. Anomalies that migrate over time between 10 and 20 km distance trace the movement of the episode 61g flow breakouts between Pu'u 'O'o and the Kamokuna ocean entry.

Figure 290. The MIROVA thermal anomaly data for Kilauea tracks both radiative power and the distance of the radiative power from the assigned "summit" location (about 10.5 km E of the high point on the western Halema'uma'u crater rim). In this chart of the distance to the thermal anomalies during the year ending 17 August 2017, the variations in distance (y-axis) correspond closely to changes in the locations of the active lava flow sites. The Halema'uma'u and Pu'u 'O'o craters are located about 10 km away; the episode 61g flow field has anomalies that track between 10 and 20 km away; and the Kamokuna ocean entry is represented by the anomalies about 20 km distant. See additional discussion in the text. Courtesy of MIROVA.

Plumes of SO₂ emissions visible in satellite data are common at Kilauea (figure 291). The normal trade winds send most emissions to the SW, but occasional "Kona" winds blow in the opposite direction and disperse SO₂ to the NE from the summit. Large lava breakouts and activity at the summit crater can produce substantial SO₂ plumes.

Figure 291. Sulfur dioxide emissions data from the OMI instrument on the Aura satellite for selected days at Kilauea during January and March 2017. Top Left: uncommon "Kona winds" blowing from SW to NE over the island, opposite to the normal trade winds dispersed the SO2 plume to the NE on 5 January 2017. Top Right: The more common trade wind direction, to the SW, carried a typical size SO2 plume on 10 January 2017. Bottom: The significant breakout from episode 61g that began on 5 March likely produced the larger than normal SO2 plumes captured on 5 and 6 March 2017. Courtesy of NASA GSFC.

Geologic Background. Kilauea, which overlaps the E flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 km2, destroying nearly 200 houses and adding new coastline to the island.

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawai'i National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); 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/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: http://so2.gsfc.nasa.gov/index.html).

The eruption of Klyuchevskoy that began in late August 2015 continued with fluctuating activity through March 2017 (BGVN 42:04) (figure 20). Although lava effusion ended in early November 2016, explosive activity was observed through March 2017 (BGVN 42:04). Similar eruptive activity continued through October 2017 as reported here, exhibiting moderate to strong ash explosions. The Kamchatkan Volcanic Eruption Response Team (KVERT) is responsible for monitoring this volcano, and is the primary source of information. Times are in UTC (local time is UTC + 12 hours).

Figure 20. Ash plume rising from the summit crater of Klyuchevskoy on 30 March 2017. Courtesy of Yu. Demyanchuk (IVS FEB RAS, KVERT).

KVERT reported that weak to moderate ash explosions and thermal anomalies occurred throughout March-October 2017 (table 17). The last time ash was reported during the period of this report was on 7 September 2017. The volcano is often obscured by clouds that prevent plumes from being detected in satellite imagery. However, excellent clear views from space were obtained on 10 June (figure 21) and 17 August 2017 (figures 22 and 23) that showed typical ash plumes. Ground-based observers also noted erupting ash plumes, some not identified in satellite imagery, including one on 8 October 2017 (figure 24).

Table 17. Summary of ash plumes and Aviation Color Codes at Klyuchevskoi from March through mid-October 2017. Data courtesy of KVERT.

Figure 21. A brown ash plume can be seen rising from Klyuchevskoy on 10 June 2017 in this image taken from space looking NE. The tall peak adjacent to Klyuchevskoy and to the S is Kamen; adjacent and just S of that is Bezymianny. The snow-covered mass to the NW contains Ushkovsky volcano. South of the Klyuchevskoy-Kamen pair is the snow-covered active volcano Tolbachik, east of which are the snow-free Zimina (to the north) and Udina volcanos. Courtesy of NASA Johnson Space Center (photo ISS052-E-896).

Figure 22. The Operational Land Imager (OLI) on Landsat 8 satellite captured this image of a volcanic ash plume streaming W from Klyuchevskoy on 19 August 2017. The plume is brown; clouds are white. Note that there is also a smaller white plume extending SW from Bezymianny, about 10 km S. An enlarged image of the "Detail" area is shown in the next figure. Courtesy of NASA Earth Observatory; image by J. Stevens, using Landsat data from the U.S. Geological Survey.

Figure 23. Detail from an Operational Land Imager (OLI) on Landsat 8 image of Klyuchevskoy erupting on 19 August 2017. The ash plume is rising about 6 km above the summit. Courtesy of NASA Earth Observatory; image by J. Stevens, using Landsat data from the U.S. Geological Survey.

Figure 24. Ash plume rising from the summit crater of Klyuchevskoy on 8 October 2017. Courtesy of I. Borisov (IVS FEB RAS).

Thermal alerts in the MODVOLC system ended on 2 November 2016, corresponding to the end of lava effusion reported by KVERT (BGVN 42:04). The number of MIROVA thermal anomalies decreased significantly in early November 2016 as well (figure 25), then gradually declined further over the next few months.

Figure 25. MODIS thermal anomalies identified in the MIROVA system, plotted as log radiative power for the year ending 24 October 2017. 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/); 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/); 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 Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/).

Japan's Nishinoshima volcano erupted above sea level in November 2013 for the first time in 40 years. Between then and November 2015 the island grew from 0.29 to 2.63 km² as a result of numerous lava flows erupting from vents around a central pyroclastic cone (BGVN 41:09). Eruptive activity ended in November 2015, and no additional activity was observed during 2016. A new eruption that included ash emissions and lava flows began in April 2017, and continued until mid-August 2017. Two major lobes of lava emerged from the central crater of the pyroclastic cone and flowed SW and W, expanding the size of the island to about 2.2 km in the E-W dimension and 1.9 km in the N-S dimension, a total area of about 3 km².

Information comes primarily from monthly reports provided by the Japan Meteorological Agency (JMA) and reports and photographs taken by the Japan Coast Guard (JCG), which monitors the volcano due to its remote location in the Pacific Ocean, approximately 940 km S of Tokyo along the Izu-Bonin arc. Satellite thermal data (MODIS) also provides valuable information about the active heat flow at the volcano.

Changes during November 2013-October 2015. Nishinoshima grew about twelve times in area between 6 November 2013 and 11 October 2015, after nearly two years of constant eruptive activity (figure 39). JCG presented a map in November 2015 showing the areas added to Nishinoshima between November 2013 and November 2015 (figure 40). The Ocean Information Division of JMA conducted a seabed topographic survey in a 4-km radius around the island between 22 June and 9 July 2015 that revealed the new submarine topography (figure 41).

Figure 39. Nishinoshima grew about twelve times in area between 6 November 2013 and 11 October 2015. The Operational Land Imager (OLI) on Landsat 8 captured these images of the old and new island on those two dates. The top image shows the area on 6 November 2013, two weeks before the eruption started. The second image was acquired on 11 October 2015, after nearly two years of constant eruptive activity. In both images, pale areas just offshore likely reveal volcanic gases bubbling up from submerged vents or sediments disturbed by the eruption. Courtesy of NASA Earth Observatory.

Figure 40. Changes in the shape and size of Nishinoshima between 21 November 2013 and 17 November 2015. Black dots outline areas above sea level prior to 21 November 2013. The sets of three numbers in the legend represent dates as follows '25' is 2013, '26' is 2014 and '27' is 2015. These numbers are followed by month and day. For example 26..12..25 is 25 December 2014. The total area of the island is shown after each date. The red outline shows the outer edge of land as of 17 November 2015. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 20 November 2015).

Figure 41. The Ocean Information Division of JMA conducted a seabed bathymetric survey in a 4-km radius around Nishinoshima between 22 June and 9 July 2015 that revealed the new submarine topography after almost two years of eruption. The dashed blue line shows the area above sea level prior to November 2013. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 20 October 2015).

Activity during October-December 2015. The JCG visited Nishinoshima on 13 October, 17 November, and 22 December 2015 (BGVN 41:09). Explosions with ash plumes (figures 42 and 43) and active lava flows from a hornito on the flank (figures 44 and 45) were observed on 13 October. On 17 November they observed crater-like depressions on the N flank of the pyroclastic cone (figure 46).

Figure 42. Ash explosion from the pyroclastic cone at Nishinoshima on 13 October 2015. Japanese text means "crater". Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 16 October 2015).

Figure 43. Plumes of discolored water surround Nishinoshima while an explosion emits ash from the pyroclastic cone on 13 October 2015. Japanese text means "discolored water area". Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 16 October 2015).

Figure 44. Lava flowed from a hornito on the NE flank of the pyroclastic cone (arrow at left, "lava flow outlet") at Nishinoshima on 13 October 2015. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 16 October 2015).

Figure 45. Thermal imagery revealed lava flowing N and W from the hornito on the NE side of the pyroclastic cone at Nishinoshima on 13 October 2015. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 16 October 2015).

Figure 46. Crater depressions appeared on the N side of the pyroclastic cone at Nishinoshima on 17 November 2015. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 20 November 2015).

By the time of their visit on 22 December, there were no further signs of activity from the pyroclastic cone (figure 47), and a comparison of thermal imagery between 17 November and 22 December (figure 48) showed a dramatic decline in heat flow. Aerial photography of the island that day revealed the extent of the new island compared with the pre-November 2013 landmass (figure 49).

Figure 47. The pyroclastic cone and summit crater at Nishinoshima were quiet when observed by the JCG on 22 December 2015. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 25 December 2015).

Figure 48. A comparison of thermal imagery from 22 December 2015 (left) and 17 November 2015 (right) reveals a decrease in heat flow at Nishinoshima from both the summit crater and the hornito on the SW flank. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 25 December 2015).

Figure 49. Composite of aerial photographs of Nishinoshima on 22 December 2015. Green and yellow outlines show areas that were above sea level on 21 November 2013 for comparison. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 25 December 2015).

Activity during 2016. The Japan Coast Guard continued with monthly observations during 2016, with visits on 19 January, 3 February, 5 March, 14 April, 20 May, 7 June, 19 July, 18 August, 15 September, and 6 October 2016. Only weak fumarolic activity was observed during the February visit (figure 50). Thermal measurements consistently remained at or below 100°C during the year; plumes of light brown to yellowish-green discolored water generally extended 200-400 m away from the coastline, suggesting continued submarine hydrothermal activity. The discolored water extended 1,000 m off the N coast during the 5 March visit. Dense steam filled the summit crater of the pyroclastic cone on 14 April (figure 51). During their 20 May visit, JCG noted a slight increase in size of the beach areas around the shoreline; this increase continued for several months, likely a result of fresh lava flows breaking down into sand from the wave action. During May and June, small amounts of magmatic gas were visible rising a few tens of meters above the summit crater.

Figure 50. Weak fumarolic activity from the S side of the crater rim was the only notable activity observed at Nishinoshima during a visit by JCG on 3 February 2016. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 5 February 2016).

Figure 51. Steam emanated from the summit crater of the pyroclastic cone at Nishinoshima during a visit by the Japan Coast Guard on 14 April 2016. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 19 April 2016).

On 17 August, JMA cancelled the maritime volcano warning (preventing vessels from approaching within 1.5 km), as a result of the decreased activity. Professor Kenji Nogami of the Tokyo Institute of Volcanic Fluid Research Center noted an increase in the discolored water area, extending about 1,000 m on the S side of the island during the JCG overflight on 15 September. JCG conducted a new submarine survey of the area during 22 October-10 November 2016 to provide data for new maritime charts. No additional reports were issued until a new eruptive episode was observed on 20 April 2017.

While the Japan Coast Guard did not observe volcanic activity during 2016, the MIROVA data suggests that low levels of heat flow were intermittent throughout the year, with slight increases during May-June, July-August, and September-October 2016 (figure 52). The heat flow recorded by MIROVA during 2016 was about an order of magnitude less that that during the period with active lava flows in September-November 2015.

Figure 52. MIROVA Radiative Power thermal anomaly graph for Nishinoshima from 16 August 2015 through 15 November 2017. Data is from the MODIS satellite instrument. Active lava flows were observed by the JCG through mid-November 2015 (top graph). Only minor fumarolic activity was intermittently observed during 2016. Renewed lava flows and Strombolian activity were again observed beginning on 21 April 2017 (bottom graph). Courtesy of MIROVA.

Activity during April-October 2017. The JCG observed renewed eruptive activity when they visited Nishinoshima on 20 April 2017. They confirmed the existence of a new lava flow from the summit crater of the pyroclastic cone on 21 April. They also observed a gray ash plume 500 m wide rising 1,000 m above the crater, Strombolian explosions at intervals of tens of seconds, and molten lava within the crater. A new lava flow appeared on the N side of the cone, although it had not yet reached the ocean. By the time of the next overflight on 27 April, JCG confirmed that the lava flow had reach the ocean on the W and SW coast of the island (figure 53), and a new pyroclastic cone had formed within the summit crater. Strong MODVOLC multi-pixel thermal alerts first appeared on 18 April, and persisted with no more than a few day's break until early August 2017. The Tokyo VAAC reported an ash plume on 20 April at 2.4 km altitude drifting W, but it was not identifiable in satellite data.

Figure 53. New lava flows (outlined in white) reach the ocean on the W and SW coast of Nishinoshima on 27 April 2017. Ash emissions rose from the summit crater, and steam plumes emerged from the numerous places where the lava entered the sea. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 28 April 2017).

Strombolian explosions were observed every 40-60 seconds during an overflight on 2 May 2017. They emerged from the new pyroclastic cone at the center of the summit crater. Ash plumes rose 500 m and drifted SW. Two vents on the N side of the crater produced lava that flowed to the ocean on the SW coast of the island (figure 54). Areas of new lava extended about 170 m W and 180 m SW into the ocean. Continued ash emissions were drifting N from the island on 24 May, and lava continued flowing into the sea along the SW shore.

Figure 54. A thermal image of Nishinoshima taken on 2 May 2017 reveals an active lava flow emerging from the N flank of the crater and flowing SW into the ocean. Two vents are identified with the white arrows. The red arrow identifies the pyroclastic cone within the summit crater. The new areas of lava extended about 170 m W and 180 m SW into the ocean. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 10 May 2017).

During the next overflight on 6 June, JCG confirmed a new lava flow emerging from the W flank of the pyroclastic cone and flowing to the sea (figure 55). In late June 2017, JMA published a new bathymetric map of Nishinoshima and surrounding waters as of October 2016. JCG noted that explosions continued at 30-second intervals during their 29 June overflight. Ash plumes rose to about 200 m above the crater rim, and lava was entering the sea on the W side of the island (figure 56). The new lava flows now extended into the sea about 330 m to the W and 310 m to the SW (figure 57).

Figure 55. A thermal image of lava flowing into the ocean on the W side of Nishinoshima captured during a JCG overflight on 6 June 2017. A new lava flow (red arrow) flows W from the crater to the sea while the lobes of the existing flow continue to extend into the ocean. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 9 June 2017).

Figure 56. A thermal image of Nishinoshima taken on 29 June 2017 reveals lava entering the sea on the W side of the island, and a new vent with fresh lava on the S side of the pyroclastic cone (white circle). Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 5 July 2017).

Figure 57. Two lobes of fresh lava flows extend S and SW from Nishinoshima on 29 June 2017 as ash emissions rise from the central crater. Lava is actively flowing into the sea on the W side of the W lobe, but is no longer active on the SW lobe. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 5 July 2017).

The Tokyo VAAC reported multiple ash emissions during June. An eruption generated an ash plume on 8 June that rose to 1.2 km altitude and drifted SW. Emissions were observed in satellite imagery for the next 24 hours before dissipating. Another ash plume on 26 June was reported drifting NE at 3 km altitude. Ash seen on 30 June was reported drifting W at 2.1 km altitude for most of the day before dissipating. The Tokyo VAAC reported a possible eruption on 2 July that sent an E-drifting ash plume to 1.5 km altitude. It was later reported at 3 km altitude before dissipating. Ash and bombs were observed exploding from the central crater during the 11 July 2017 JCG overflight. Lava was also still entering the sea on the W side of the island (figure 58).

Figure 58. Strombolian explosions and lava entering the sea were captured in this thermal image taken from the W side of Nishinoshima on 11 July 2017. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 14 July 2017).

The JCG visited the island on 11 and 24 August 2017. They did not witness any eruptive activity, but diffuse steam plumes were seen rising from the crater rim. They also noted steam plumes from lava that was still entering the sea on the W side of the island on 11 August, but not during the 24 August flyover. Aerial photos taken that day showed the extent of new land formed since late April (figure 59). Additional flyovers by JCG on 15 September and 7 October confirmed a lack of active lava flows, and only minor steam plumes were reported rising from the crater rim. The last MODVOLC thermal alert appeared on 5 August. The MIROVA thermal anomaly signals that had abruptly reappeared in late April gradually tapered off throughout August, confirming a decrease in the heat flow as the lava flows cooled (figure 52).

Figure 59. Composite of aerial photos taken on 24 August 2017 showing the increased landmass at Nishinoshima from the new lava flows that erupted between 18 April and 11 August. The green outline shows the area of the old (pre-Nov 2013) Nishinoshima still visible on 24 August. The blue outline represents the shoreline prior to the eruption of 18 April. The yellow outline shows the shoreline as of 29 June 2017, and the red outline shows the area outline as of 24 August 2017. Courtesy of Japan Coast Guard (Status of volcanic activity at Nishinoshima, 29 August 2017).

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), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Japan Coast Guard (JCG), Policy Evaluation and Public Relations Office, 100-8918, 2-1-3 Kasumigaseki, Chiyoda-ku, Tokyo, Telephone, 03-3591-6361 (URL: http://www.kaiho.mlit.go.jp/info/kouhou/h29/index.html); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); 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/).

The Virunga Volcanic Province (VVP) in the Democratic Republic of the Congo is part of the western branch of the East African Rift System. Nyamuragira (or Nyamulagira), a high-potassium basaltic shield volcano on the W edge of VVP, includes a lava field that covers over 1,100 km² and contains more than 100 flank cones in addition to a large central crater (see figure 54, BGVN 40:01). A large lava lake that had been active for many years emptied from the central crater in 1938. Numerous flank eruptions have been observed since that time, the most recent during November 2011-March 2012 on the NE flank. This was followed by a period of degassing with SO₂-rich plumes, but no observed thermal activity, from April 2012 through April 2014. Lava fountains at the central crater in July 2014 signaled the return of a lava lake, which was confirmed in November 2014. The lake lasted through April 2016 when its thermal signal abruptly disappeared (see figure 62, BGVN 42:06).

Thermal activity suggesting reappearance of the lava lake began again in early November 2016, and strengthened in both frequency and magnitude into early January 2017, continuing with a strong signal through April 2017 before tapering off during May 2017. No further activity was reported through November 2017. Ground-based observations are scarce due to the unstable political climate, but occasional information is available from the Observatoire Volcanologique de Goma (OVG), MONUSCO (the United Nations Organization working in the area), geoscientists who study Nyamuragira, and travelers who visit the site. The most consistent data comes from satellite: thermal data from the MODIS instrument processed by the MODVOLC and MIROVA systems, SO₂ data from the AURA instrument on NASA's OMI satellite, and NASA Earth Observatory images from a variety of satellites.

Thermal MODIS data indicated that a renewed period of activity began in late November 2016 after a period of quiescence since mid-May 2016. The first MODVOLC alert pixels appeared on 27 November. They were intermittent during December, but increased significantly during January-April 2017, with 30-50 alert pixels each month. They stopped abruptly on 2 May 2017. The MIROVA thermal anomaly graph shows a similar pattern of increasing thermal values from January through April 2017, with both the frequency and intensity tapering off during May 2017 (figure 69). No thermal anomalies were reported within 5 km of the summit from June through November 2017.

Figure 69. Thermal anomalies at Nyamuragira for the year ending on 27 November 2017 show a pattern of increasing frequency and intensity from January through April, with values tapering off during May, and no further heat flow activity within 5 km of the summit after the last week of May 2017. Courtesy of MIROVA.

During the period from December 2016 to April 2017 thermal anomalies were relatively high, but there were no reported SO₂ anomalies from the OMI satellite instrument. This is in contrast with the period from April 2014-April 2016 when both SO₂ values and thermal anomaly values were high. Very little ground-based data is available to confirm the eruptive activity of 2017. A photograph from an Instagram user of an image reported as Nyamuragira on 26 January 2017 shows the lava lake at the bottom of the summit crater (figure 70). Bubbling lava from the crater was photographed by Charley Kasereka on 11 March 2017 (see figure 66, BGVN 42:06). An image captured in May 2017 shows steam at the summit crater and lava flows around the caldera, with Nyiragongo in the background (figure 71). A photograph posted 16 September 2017 shows volcanologist Dario Tedesco on the crater rim surrounded by plumes of steam (figure 72).

Figure 70. Photo of the active lava lake in the summit crater of Nyamuragira on 26 January 2017. Courtesy of Tim Best Direct (posted on Instagram).

Figure 71. Sunset at Nyamuragira on 21 May 2017 appeared to show fresh steaming lava in the area between the pit crater and the caldera rim, with a possible new overflow of the rim in the foreground. The image is looking SE and shows the larger Nyiragongo with a steam plume rising from the summit crater in the background. Courtesy of Tropic Air Kenya (posted on Instagram).

Figure 72. Thick steam plumes rise from the crater of Nyamuragira as volcanologist Dario Tedesco collects samples in this photo posted on 18 September 2017. Courtesy of Vincent Tremeau (posted on Instagram).

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

Information Contacts: 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/); Observatoire Volcanologique de Goma (OVG), Goma, North Kivu, DR Congo (URL: https://www.facebook.com/Observatoire-Volcanologique-de-Goma-OVG-180016145663568/); Virunga Volcanoes, managed by a Belgian-Luxembourgian (BeLux) scientific consortium mainly coordinated by the Royal Museum for Central Africa, the European Center for Geodynamics and Seismology and the National Museum of Natural History of Luxembourg (URL: http://www.virunga-volcanoes.org/); Vincent Tremeau, Instagram user vtremeau (URL: https://www.instagram.com/p/BZMGqX5Bhwl/); Charly Kasereka, Instagram user charlykasereka (URL: https://www.instagram.com/charlykasereka/); Tropic Air Kenya, Instagram user tropicairkenya (URL: https://www.instagram.com/p/BUXbNzjlh4Q/); Tim Best Direct, Instagram user timbestdirect (URL: https://www.instagram.com/p/BPvUgL9BfaX/).

The lava lake in Nyiragongo's main crater has been observed since 1971, and might have been present even before then. There is no regular ground monitoring of the volcano, but occasional field visits by scientific teams and tourist expeditions provide some information about its activity. Two teams of scientists that visited the volcano during March 2016 provided observations of a new vent (BGVN 42:01). This report describes activity during January-October 2017.

Volcano Discovery reported that on 6 June 2017 a team visited the summit (figure 62) and stayed for three days. They noted that the surface of the lava lake (about 220 m across was continuously in motion as exploding gas bubbles created small degassing fountains that recycled the cold black crust back into the incandescent liquid lava. Strong degassing also occurred from the edges of the lava lake, the 2016 hornito, and along the southern fracture zone.

Figure 62. Photo of the summit caldera at Nyiragongo showing its terraces and lava lake in early June 2016. Courtesy of Ingrid Smet.

Figure 63. Photo of the lava lake surface at Nyiragongo, early June 2017. The thin black crust is continuously broken apart by heat and degassing from the underlying liquid lava, creating the fractured surface. Courtesy of Ingrid Smet.

According to a news account (Metro) that cited a statement issued by the Goma Volcanic Observatory, Nyiragongo and nearby Nyamulagira volcanoes experienced intense seismic activity in their respective craters around 17-18 October 2017, before decreasing. Consistent with the presence of the active lava lake, thermal anomalies in satellite-based MODIS data identified by the MODVOLC and MIROVA systems were recorded almost daily during the reporting period.

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

Information Contacts: Tom Pfeiffer, Volcano Discovery (URL: http://www.volcanodiscovery.com/); Observatoire Volcanologique de Goma (OVG), Goma, North Kivu, DR Congo (URL: https://www.facebook.com/Observatoire-Volcanologique-de-Goma-OVG-180016145663568/); 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/); Metro, Mass Transit Media, Gallery Ravenstein 4, 1000 Brussels, Belgium (URL: https://fr.metrotime.be/).

The andesitic Volcán El Reventador lies well east of the main volcanic axis of the Cordillera Real in Ecuador and has historical observations of eruptions with numerous lava flows and explosive events going back to the 16th century. The largest historical eruption took place in November 2002 and generated a 17-km-high eruption cloud, pyroclastic flows that traveled 8 km, and several lava flows. Eruptive activity has been continuous since 2008. From January-April 2016, monthly eruptive activity included ash plumes, pyroclastic flows, and ejected incandescent blocks (BGVN 42:07), along with a lava flow observed in January. Similar ongoing activity during May-December 2016 is described below with information provided by the Instituto Geofisico-Escuela Politecnicia Nacional (IG-EPN) of Ecuador, and the Washington Volcanic Ash Advisory Center (VAAC).

Ash emissions and incandescent blocks traveling down all the flanks of Reventador persisted throughout May-December 2016 (table 8, figure 56). Ash emissions averaged 12 or 13 per month, although they were only observed during clear days. Emission heights were generally less than 1,000 m above the 3,210-m-high summit, but they were reported at 2 km above the summit once in May, several times in November, and once in December. Incandescent blocks were mostly reported traveling 800-1,500 m down the flanks, although larger events during September sent them as far as 2.2 km. Pyroclastic flows were much less common, reported three times in May, twice in September, and twice in December. A single lava flow was noted in November 2016.

Table 8. Number of eruptive events at Reventador during May-December 2016. Reported events include ash emissions, observations of incandescent blocks traveling down the flanks, and pyroclastic flows. The number of clear days per month during which these observations were made is shown in the right hand column. Information from IG daily reports.

Figure 56. Chart showing numbers of emission events per month at Reventador, May-December 2016. Reported events include ash emissions (blue), incandescent blocks rolling down the flanks (orange) and pyroclastic flows (gray). Data from IG daily reports. Numbers include observations on clear days only, not every day of the month. Number of clear days per month are shown in table 8.

Thermal anomalies recorded by the MIROVA system at Reventador showed that the nature of the ongoing eruptive activity during May-December 2016 included significant sources of heat (figure 57). Moderate to high heat levels of thermal anomalies were recorded numerous times every month during the period.

Figure 57. Thermal anomalies were persistent at Reventador for the year ending 29 March 2017. Activity was variable, but power output remained largely in the moderate to high value range with anomalies reported every week. Courtesy of MIROVA.

Incandescent blocks descended the flanks on 12 days during May 2016, typically to distances between 1-1.5 km; the NE, S, and SE flanks were most affected. IG reported ash emissions during ten days of the month, rising 300-1,500 m above the summit crater, except for a 2,000-m-high plume reported on 25 May. The prevailing winds sent the plumes to the NW or SW. The Washington VAAC observed ash emissions in satellite imagery at 4.6 km altitude (1 km above the summit) on 27 May extending 10 km WNW from the summit. On 30 May, they observed ash emissions extending both N and S at 7 km altitude. Pyroclastic flows descended the flanks three times; 1.5 km down the SE flank on 18 May, 1 km down the SE flank on 24 May, and 2 km down the SW flank on 25 May.

During fieldwork from 8 to 10 June 2016, IG staff working near the base of Reventador witnessed persistent activity, noting a 2-km-high ash plume on 9 June (figure 58) and audible sounds. They also reported evidence of recent pyroclastic flows visible primarily on the N and S flanks, and fine gray ash covering vegetation within the E and NE sides of the summit caldera (figure 59).

Figure 58. Photo showing Reventador erupting on 9 June 2016, along with the coincident seismic and spectral signals from the eruption. The 2-km-high plume was dense with ash. View from the SW flank. Photo by G. Viracucha, courtesy of IG (Actividad superficial del Volcan el Reventador, 24 Junio 2016).

Figure 59. Vegetation covered with fine gray ash inside the summit caldera at Reventador during 8-10 June 2016. Photo by G. Viracucha, courtesy of IG-EPN (Actividad superficial del Volcan el Reventador, 24 Junio 2016).

The weather during June 2016 prevented visual observations of activity during 17 days of the month. Even so, IG reported nine observations of incandescent blocks travelling 800-1,500 m down most of the flanks, and five observations of ash emissions, most of them rising only a few hundred meters above the summit. The Washington VAAC reported an ash emission at 6.7 km altitude (3.5 km above the summit) visible in clear satellite imagery on 5 June. It was drifting W about 75 km from the summit. They also noted a small emission of possible ash at 4.9 km altitude drifting W the next day. IG reported a plume on 10 June at 1,500 m above the summit drifting NW.

Persistent activity during July and August 2016 included 14 and 13 reports of ash emissions, respectively, and 6 and 7 reports of incandescent blocks from the summit. The ash emissions ranged from 300-800 m above the summit in July and 100-1,000 m above the summit during August. The incandescent blocks traveled down all the flanks at various times to distances up to 1,000 m from the summit. The Washington VAAC reported that satellite imagery on 16 July showed a possible ash cloud centered 30 km W of the summit at 4.6 km altitude. On 8 August they observed an ash emission in multi-spectral imagery moving WNW extending about 35 km from the summit at 6.1 km altitude. Another plume the next day was picked up in multi-spectral imagery at 5.2 km altitude the same distance from the summit.

Activity generating incandescent blocks down the flanks increased during September 2016, and was reported on 19 days. Most reports indicated blocks travelling 1,000 m down several different flanks. Larger events during 19-20 September sent blocks 2,000-2,200 m down the SW and SE flanks. Ash emissions were reported ten times by IG during the month, with plume heights ranging from 200 to 1,200 m above the summit. The Washington VAAC only reported a single ash emission rising to 4.3 km altitude and drifting SE on 8 September. Two pyroclastic flows traveled down the SE flank; on 14 September one traveled 1,800 m, and on 19 September one traveled 1,500 m.

During October 2016, there were 10 ash emission events and 14 incandescent block events; during November, there were 18 ash events and 11 incandescent block events. Ash plume heights above the crater during October were all under 1,000 m, but several rose as high as 2 km during 12-17 November. The Washington VAAC reported an ash emission at 3.9 km altitude on 20 October moving WNW about 25 km from the summit. They also observed a hotpot in satellite imagery the same day. On 31 October, they observed two diffuse ash emissions extending 30 km NW from the summit at 5.8 km altitude. A lava flow extended 300 m down the SE flank on 26 November.

Ash emissions were reported by IG on 20 days during December, the most for this reporting period. Plume heights ranged from 400 to 2,000 m above the summit crater, usually drifting W or NW. Incandescent blocks were only reported four times. Except for 13 December when they traveled 1,500 m down the SSW flank, they traveled 800 m down various flanks. The ash emission reported by the Washington VAAC on 9 December was moving SW near 6.1 km altitude. Other VAAC reports during December indicated only puffs of gas with minor volcanic ash noted in the webcam. Pyroclastic flows were reported on 9 and 26 December.

Geologic Background. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.

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/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: http://so2.gsfc.nasa.gov/index.html).

Suwanosejima, an andesitic stratovolcano in Japan's northern Ryukyu Islands, was intermittently active for much of the 20th century, producing ash plumes, Strombolian eruptions, and ash deposits. Continuous activity since October 2004 has consisted generally of multiple ash plumes most months rising a few hundred meters above the summit to altitudes between 1 and 2 km, and tens of reported explosions. Activity between January and September 2015 included small eruptions in July and August that produced ash plumes rising to 3-4 km altitude. Increased activity beginning in August 2015 included incandescence at the crater and increased explosive activity with incandescence in September; 89 explosions occurred that month, and ash fell in the village 4 km SSW (BGVN 42:01). Eruptive activity for the period of September 2015-December 2016 included intermittent explosions, ash plumes up to 4.3 km altitude, ashfall within a 5-km radius, and Strombolian activity. Information is provided primarily by the Japan Meteorological Agency (JMA), and the Tokyo Volcanic Ash Advisory Center (VAAC).

Activity during September-December 2015. Numerous explosions were reported by the JMA during 24-30 September. The Tokyo VAAC reported a plume at 2.1 km altitude extending SE on 24 September; subsequent reports noted there were no observations of ash emissions or plumes in satellite data during that time, and no further VAAC reports were issued after 30 September (until January 2016).

JMA reported that explosions at the Otake crater on 2, 13, and 31 October 2015 produced gray-and-white emissions and rose a maximum of 800 m above the summit (at ~800 m elevation). Explosions occurred on 1 and 20 November as well; the plume rose 1 km above the crater rim on 1 November. Ashfall was confirmed in the small village 4 km SSW after both events. There were no explosions reported during December 2015; only steam emissions rose 600 m above the summit crater, and rumbling was heard on 12 December from the nearby settlement. Incandescence was visible with a thermal camera at night during September-December 2015.

Activity during 2016. According to JMA, explosions and intermittent emissions occurred during most months of 2016 (table 12). Ashfall in the village 4 km SSW of the summit was reported during January-April, July-August, and October-November. Steam-and-ash plume heights ranged from 800 to 2,700 m above the crater rim. The number of monthly seismic events was low in January (25), increasing to a maximum of 1,195 in April. It dropped below 200 by July, and below 100 during November and December. Incandescence at night was reported often every month. An overflight on 31 May 2016 revealed a steam plume rising 400 m above Otake crater (figure 20). Strombolian activity on 15 September and 23 November 2016 ejected incandescent blocks onto the crater rim (figure 21). An ash emission on 25 November sent gray and white ash and steam 1,800 m above the crater rim (figure 22). Incandescent blocks from an explosion were also observed on 17 December.

Table 12. Activity at Suwanosejima during 2016 reported by JMA. Times are local.

Figure 20. Aerial photos of Otake crater at Suwanosejima on 31 May 2016. Upper image is the close-up view outlined in red below. Courtesy of JMA (Volcanic activity commentary on Suwanosejima, May 2016).

Figure 21. Strombolian activity and explosion at Suwanosejima on 15 September 2016 sent a large incandescent block outside the crater rim (center left). Courtesy of JMA "Paris tree" webcam (Volcanic activity commentary on Suwanosejima, September 2016).

Figure 22. Explosive activity at Suwanosejima during November 2016 produced Strombolian activity and ash emissions. A Strombolian explosion on 23 November (top photo) sent incandescent blocks around the crater rim (left center, viewed by the JMA "Nogi" webcam). An ash emission on 25 November (bottom photo) sent ash and steam 1,800 m above the crater rim (viewed by the JMA "Campsite" webcam). Courtesy of JMA (Volcanic activity commentary on Suwanosejima, November 2016).

The Tokyo VAAC also reported information about ash plumes and explosions during 2016 (table 13). Explosions were reported during every month of 2016 except February, and ranged from two in January to 19 in August. Most plume heights were lower than 2.7 km altitude. Exceptions included: an explosion on 1 August produced an ash plume that rose to 3.4 km altitude and drifted S; a plume rose to 3 km on 29 November and also drifted S; and the largest of the year, an ash plume that rose to 4.3 km altitude and drifted E, on 13 December (figure 23).

MODVOLC thermal alerts were reported on 20 April, 4 May (3), and 17 May 2016.

Table 13. Summary of activity reported at Suwanosejima during 2016 by the Tokyo VAAC. Time in UTC.

Figure 23. The largest ash explosion of 2016 at Suwanosejima (viewed from the JMA "Parquet" webcam) occurred on 13 December 2016 and sent a plume to 4.3 km altitude (3,500 m above the crater rim). Courtesy of JMA (Volcanic activity commentary on Suwanosejima, December 2016).

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/).