Kuchinoerabujima encompasses a group of young stratovolcanoes located in the northern Ryukyu Islands. All historical eruptions have originated from the Shindake cone, with the exception of a lava flow that originated from the S flank of the Furudake cone. The most recent previous eruptive period took place during October 2018-February 2019 and primarily consisted of weak explosions, ash plumes, and ashfall. The current eruption began on 11 January 2020 after nearly a year of dominantly gas-and-steam emissions. Volcanism for this reporting period from March 2019 to April 2020 included explosions, ash plumes, SO₂ emissions, and ashfall. The primary source of information for this report comes from monthly and annual reports from the Japan Meteorological Agency (JMA) and advisories from the Tokyo Volcanic Ash Advisory Center (VAAC). Activity has been limited to Kuchinoerabujima's Shindake Crater.

Volcanism at Kuchinoerabujima was relatively low during March through December 2019, according to JMA. During this time, SO₂ emissions ranged from 100 to 1,000 tons/day. Gas-and-steam emissions were frequently observed throughout the entire reporting period, rising to a maximum height of 1.1 km above the crater on 13 December 2019. Satellite imagery from Sentinel-2 showed gas-and-steam and occasional ash emissions rising from the Shindake crater throughout the reporting period (figure 7). Though JMA reported thermal anomalies occurring on 29 January and continuing through late April 2020, Sentinel-2 imagery shows the first thermal signature appearing on 26 April.

Figure 7. Sentinel-2 thermal satellite images showed gas-and-steam and ash emissions rising from Kuchinoerabujima. Some ash deposits can be seen on 6 February 2020 (top right). A thermal anomaly appeared on 26 April 2020 (bottom right). Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

An eruption on 11 January 2020 at 1505 ejected material 300 m from the crater and produced ash plumes that rose 2 km above the crater rim, extending E, according to JMA. The eruption continued through 12 January until 0730. The resulting ash plumes rose 400 m above the crater, drifting SW while the SO₂ emissions measured 1,300 tons/day. Ashfall was reported on Yakushima Island (15 km E). Minor eruptive activity was reported during 17-20 January which produced gray-white plumes that rose 300-500 m above the crater. On 23 January, seismicity increased, and an eruption produced an ash plume that rose 1.2 km altitude, according to a Tokyo VAAC report, resulting in ashfall 2 km NE of the crater. A small explosion was detected on 24 January, followed by an increase in the number of earthquakes during 25-26 January (65-71 earthquakes per day were registered). Another small eruptive event detected on 27 January at 0148 was accompanied by a volcanic tremor and a change in tilt data. During the month of January, some inflation was detected at the base on the volcano and a total of 347 earthquakes were recorded. The SO₂ emissions ranged from 200-1,600 tons/day.

An eruption on 1 February 2020 produced an eruption column that rose less than 1 km altitude and extended SE and SW (figure 8), according to the Tokyo VAAC report. On 3 February, an eruption from the Shindake crater at 0521 produced an ash plume that rose 7 km above the crater and ejected material as far as 600 m away. As a result, a pyroclastic flow formed, traveling 900-1,500 m SW. The previous pyroclastic flow that was recorded occurred on 29 January 2019. Ashfall was confirmed in the N part of Yakushima Island with a large amount in Miyanoura (32 km ESE) and southern Tanegashima. The SO₂ emissions measured 1,700 tons/day during this event.

Figure 8. Webcam images from the Honmura west surveillance camera of an ash plume rising from Kuchinoerabujima on 1 February 2020. Courtesy of JMA (Weekly bulletin report 509, February 2020).

Intermittent small eruptive events occurred during 5-9 February; field observations showed a large amount of ashfall on the SE flank which included lapilli that measured up to 2 cm in diameter. Additionally, thermal images showed 5-km-long pyroclastic flow deposits on the SW flank. An eruption on 9 February produced an ash plume that rose 1.2 km altitude, drifting SE. On 13 February a small eruption was detected in the Shindake crater at 1211, producing gray-white plumes that rose 300 m above the crater, drifting NE. Small eruptive events also occurred during 20-21 February, resulting in gas-and-steam emissions that rose 200 m above the crater. During the month of February, some horizontal extension was observed since January 2020 using GNSS data. The total number of earthquakes during this month drastically increased to 1225 compared to January. The SO₂ emissions ranged from 300-1,700 tons/day.

By 2 March 2020, seismicity decreased, and activity declined. Gas-and-steam emissions continued infrequently for the duration of the reporting period. The SO₂ emissions during March ranged from 700-2,100 tons/day, the latter of which occurred on 15 March. Seismicity increased again on 27 March. During 5-8 April 2020, small eruptive events were detected, generating ash plumes that rose 900 m above the crater (figure 9). The SO₂ emissions on 6 April reached 3,200 tons/day, the maximum measurement for this reporting period. These small eruptive events continued from 13-20 and 23-25 April within the Shindake crater, producing gray-white plumes that rose 300-800 m above the crater.

Figure 9. Webcam images from the Honmura Nishi (top) and Honmura west (bottom) surveillance cameras of ash plumes rising from Kuchinoerabujima on 6 March and 5 April 2020. Courtesy of JMA (Weekly bulletin report 509, March and April 2020).

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

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

Soputan is a stratovolcano located in the northern arm of Sulawesi Island, Indonesia. Previous eruptive periods were characterized by ash explosions, lava flows, and Strombolian eruptions. The most recent eruption occurred during October-December 2018, which consisted mostly of ash plumes and some summit incandescence (BGVN 44:01). This report updates information for January 2019-April 2020 characterized by two ash plumes and gas-and-steam emissions. The primary source of information come from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and the Darwin Volcanic Ash Advisory Center (VAAC).

Activity during January 2019-April 2020 was relatively low; three faint thermal anomalies were observed at the summit at Soputan in satellite imagery for a total of three days on 2 and 4 January, and 1 October 2019 (figure 17). The MIROVA (Middle InfraRed Observation of Volcanic Activity) based on analysis of MODIS data detected 12 distal hotspots and six low-power hotspots within 5 km of the summit during August to early October 2019. A single distal thermal hotspot was detected in early March 2020. In March, activity primarily consisted of white to gray gas-and-steam plumes that rose 20-100 m above the crater, according to PVMBG. The Darwin VAAC issued a notice on 23 March 2020 that reported an ash plume rose to 4.3 km altitude; minor ash emissions had been visible in a webcam image the previous day (figure 18). A second notice was issued on 2 April, where an ash plume was observed rising 2.1 km altitude and drifting W.

Figure 17. Sentinel-2 thermal satellite imagery detected a total of three thermal hotspots (bright yellow-orange) at the summit of Soputan on 2 and 4 January and 1 October 2019. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

Figure 18. Minor ash emissions were seen rising from Soputan on 22 March 2020. Courtesy of MAGMA Indonesia.

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Heard Island is located on the Kerguelen Plateau in the southern Indian Ocean and contains Big Ben, a snow-covered stratovolcano with intermittent volcanism reported since 1910. Due to its remote location, visual observations are rare; therefore, thermal anomalies and hotspots detected by satellite-based instruments are the primary source of information. This report updates activity from October 2019 to April 2020.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed three prominent periods of strong thermal anomaly activity during this reporting period: late October 2019, December 2019, and the end of April 2020 (figure 41). These thermal anomalies were relatively strong and occurred within 5 km of the summit. Similarly, the MODVOLC algorithm reported a total of six thermal hotspots during 28 October, 1 November 2019, and 26 April 2020.

Figure 41. Thermal anomalies at Heard from 29 April 2019 through April 2020 as recorded by the MIROVA system (Log Radiative Power) were strong and frequent in late October, during December 2019, and at the end of April 2020. Courtesy of MIROVA.

Six thermal satellite images ranging from late October 2019 to late March showed evidence of active lava at the summit (figure 42). These images show hot material, possibly a lava flow, extending SW from the summit; a hotspot also remained at the summit. Cloud cover was pervasive during the majority of this reporting period, especially in April 2020, though gas-and-steam emissions were visible on 25 April through the clouds.

Figure 42. Thermal satellite images of Heard Island’s Big Ben showing strong thermal signatures representing a lava flow in the SW direction from 28 October to 17 December 2019. These thermal anomalies are located NE from Mawson Peak. A faint thermal anomaly is also captured on 26 March 2020. Satellite images with atmospheric penetration (bands 12, 11, and 8A), courtesy of Sentinel Hub Playground.

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

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

The Kikai caldera is located at the N end of Japan’s Ryukyu Islands and has been recently characterized by intermittent ash emissions and limited ashfall in nearby communities. On Satsuma Iwo Jima island, the larger subaerial fragment of the Kikai caldera, there was a single explosion with gas-and-steam and ash emissions on 2 November 2019, accompanied by nighttime incandescence (BGVN 45:02). This report covers volcanism from January 2020 through April 2020 with a single-day eruption occurring on 29 April based on reports from the Japan Meteorological Agency (JMA).

Since the last one-day eruption on 2 November 2019, volcanism at Kikai has been relatively low and primarily consisted of 107-170 earthquakes per month and intermittent white gas-and-steam emissions rising up to 1.3 km above the crater summit. Intermittent weak hotspots were observed at night in the summit in Sentinel-2 thermal satellite imagery and webcams, according to JMA (figures 14 and 15).

Figure 14. Weak thermal hotspots (bright yellow-orange) were observed on 7 January (top) and 6 April 2020 (bottom) at Satsuma Iwo Jima (Kikai). Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Figure 15. Incandescence at night on 10 January 2020 was observed at Satsuma Iwo Jima (Kikai) in the Iodake crater with the Iwanogami webcam. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, January 2nd year of Reiwa [2020]).

Weak incandescence continued in April 2020. JMA reported SO₂ measurements during April were 400-2000 tons/day. A brief eruption in the Iodake crater on 29 April 2020 at 0609 generated a gray-white ash plume that rose 1 km above the crater (figure 16). No ashfall or ejecta was observed after the eruption on 29 April.

Figure 16. The Iwanogami webcam captured a brief gray-white ash and steam plume rising above the Iodake crater rim on Satsuma Iwo Jima (Kikai) on 29 April 2020 at 0609 local time. The plume rose 1 km above the crater summit. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, April 2nd year of Reiwa [2020]).

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

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

Fuego is a stratovolcano in Guatemala that has been erupting since 2002 with historical eruptions that date back to 1531. Volcanism is characterized by major ashfalls, pyroclastic flows, lava flows, and lahars. The previous report (BGVN 44:10) detailed activity that included multiple ash explosions, ash plumes, ashfall, active lava flows, and block avalanches. This report covers this continuing activity from October 2019 through March 2020 and consists of ash plumes, ashfall, incandescent ejecta, block avalanches, and lava flows. 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 October 2019-March 2020. Daily activity persisted throughout October 2019-March 2020 (table 20) with multiple ash explosions recorded every hour, ash plumes that rose to a maximum of 4.8 km altitude each month drifting in multiple directions, incandescent ejecta reaching a 500 m above the crater resulting in block avalanches traveling down multiple drainages, and ashfall affecting communities in multiple directions. The highest rate of explosions occurred on 7 November with up to 25 per hour. Dominantly white fumaroles occurred frequently throughout this reporting period, rising to a maximum altitude of 4.5 km and drifting in multiple directions. Intermittent lava flows that reached a maximum length of 1.2 km were observed each month in the Seca (Santa Teresa) and Ceniza drainages (figure 128), but rarely in the Trinidad drainage. Thermal activity increased slightly in frequency and strength in late October and remained relatively consistent through mid-March as seen in the MIROVA analysis of MODIS satellite data (figure 129).

Table 20. Activity summary by month for Fuego with information compiled from INSIVUMEH daily reports.

Figure 128. Sentinel-2 thermal satellite images of Fuego between 21 November 2019 and 20 March 2020 showing lava flows (bright yellow-orange) traveling generally S and W from the crater summit. An ash plume can also be seen on 21 November 2019, accompanying the lava flow. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Figure 129. Thermal activity at Fuego increased in frequency and strength (log radiative power) in late October 2019 and remained relatively consistent through February 2020. In early March, there is a small decrease in thermal power, followed by a short pulse of activity and another decline. Courtesy of MIROVA.

Activity during October-December 2019. Activity in October 2019 consisted of 6-20 ash explosions per hour; ash plumes rose to 4.8 km altitude, drifting up to 25 km in multiple directions, resulting in ashfall in Panimaché I and II (8 km SW), Morelia (9 km SW), San Pedro Yepocapa (8 km NW), Sangre de Cristo (8 km WSW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), Finca Palo Verde, La Rochela and San Andrés Osuna. The Washington VAAC issued multiple aviation advisories for a total of nine days in October. Continuous white gas-and-steam plumes reached 4.1-4.4 km altitude drifting generally W. Weak SO₂ emissions were infrequently observed in satellite imagery during October and January 2020 (figure 130) Incandescent ejecta was frequently observed rising 200-400 m above the summit, which generated block avalanches that traveled down the Seca (W), Taniluyá (SW), Ceniza (SSW), Trinidad (S), El Jute, Honda, and Las Lajas (SE) drainages. During 3-7 October lahars descended the Ceniza, El Mineral, and Seca drainages, carrying tree branches, tree trunks, and blocks 1-3 m in diameter. During 6-8 and 13 October, active lava flows traveled up to 200 m down the Seca drainage.

Figure 130. Weak SO2 emissions were observed rising from Fuego using the TROPOMI instrument on the Sentinel-5P satellite. Top left: 17 October 2019. Top right: 17 November 2019. Bottom left: 20 January 2020. Bottom right: 22 January 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

During November 2019, the rate of explosions increased to 5-25 per hour, the latter of which occurred on 7 November. The explosions resulted in ash plumes that rose 4-4.8 km altitude, drifting 10-20 km in the W direction. Ashfall was observed in Panimaché I and II, Morelia, Santa Sofía, Porvenir, Sangre de Cristo, Finca Palo Verde, and San Pedro Yepocapa. Multiple Washington VAAC notices were issued for 11 days in November. Continuous white gas-and-steam plumes rose up to 4.5 km altitude drifting generally W. Incandescent ejecta rose 100-500 m above the crater, generating block avalanches in Seca, Taniluyá, Trinidad, Las Lajas, Honda, and Ceniza drainages. Lava flows were observed for a majority of the month into early December measuring 100-900 m long in the Seca and Ceniza drainages.

The number of explosions in December 2019 decreased compared to November, recording 8-19 per hour with incandescent ejecta rising 100-400 m above the crater. The explosions generated block avalanches that traveled in the Seca, Taniluya, Ceniza, Trinidad, and Las Lajas drainages throughout the month. Ash plumes continued to rise above the summit crater to 4.8 km drifting up to 25 km in multiple directions. The Washington VAAC issued multiple daily notices almost daily in December. A continuous lava flow observed during 6-15, 21-22, 24, and 26 November through 9 December measured 100-800 m long in the Seca and Ceniza drainages.

Activity during January-March 2020. Incandescent Strombolian explosions continued daily during January 2020, ejecting material up to 100-500 m above the crater. Ash plumes continued to rise to a maximum altitude of 4.8 km, resulting in ashfall in all directions affecting Morelia, Santa Sofía, Sangre de Cristo, San Pedro Yepocapa, Panimaché I and II, El Porvenir, Finca Palo Verde, Rodeo, La Rochela, Alotenango, El Zapote, Trinidad, La Reina, and Ceilán. The Washington VAAC issued multiple notices for a total of 12 days during January. Block avalanches resulting from the Strombolian explosions traveled down the Seca, Ceniza, Taniluyá, Trinidad, Honda, and Las Lajas drainages. An active lava flow in the Ceniza drainage measured 150-600 m long during 6-10 January.

During February 2020, INSIVUMEH reported a range of 4-16 explosions per hour, accompanied by incandescent material that rose 100-500 m above the crater (figure 131). Block avalanches traveled in the Santa Teresa, Seca, Ceniza, Taniluya, Trinidad, Las Lajas, Honda, La Rochela, El Zapote, and San Andrés Osuna drainages. Ash emissions from the explosions continued to rise 4.8 km altitude, drifting in multiple directions as far as 25 km and resulting in ashfall in the communities of Panimache I and II, Morelia, Santa Sofia, Sangre de Cristo, San Pedro Yepocapa, Rodeo, La Reina, Alotenango, Yucales, Siquinalá, Santa Lucia, El Porvenir, Finca Los Tarros, La Soledad, Buena Vista, La Cruz, Pajales, San Miguel Dueñas, Ciudad Vieja, San Miguel Escobar, San Pedro las Huertas, Antigua, La Rochela, and San Andrés Osuna. Washington VAAC notices were issued almost daily during the month. Lava flows were active in the Ceniza drainage during 13-20, 23-24, and 26-27 February measuring as long as 1.2 km.

Figure 131. Incandescent ejecta rose several hundred meters above the crater of Fuego on 6 February 2020, resulting in block avalanches down multiple drainages. Courtesy of Crelosa.

Daily explosions and incandescent ejecta continued through March 2020, with 8-17 explosions per hour that rose up to 500 m above the crater. Block avalanches from the explosions were observed in the Seca, Ceniza, Trinidad, Taniluyá, Las Lajas, Honda, Santa Teresa, La Rochela, El Zapote, San Andrés Osuna, Morelia, Panimache, and Santa Sofia drainages. Accompanying ash plumes rose 4.8 km altitude, drifting in multiple directions mostly to the W as far as 23 km and resulting in ashfall in San Andrés Osuna, La Rochela, El Rodeo, Chuchu, Panimache I and II, Santa Sofia, Morelia, Finca Palo Verde, El Porvenir, Sangre de Cristo, La Cruz, San Pedro Yepocapa, La Conchita, La Soledad, Alotenango, Aldea la Cruz, Acatenango, Ceilan, Taniluyá, Ceniza, Las Lajas, Trinidad, Seca, and Honda. Multiple Washington VAAC notices were issued for a total of 15 days during March. Active lava flows were observed from 16-21 March in the Trinidad and Ceniza drainages measuring 400-1,200 m long and were accompanied by weak to moderate explosions. By 23 March, active lava flows were no longer observed.

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); 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/); 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); Crelosa, 3ra. avenida. 8-66, Zona 14. Colonia El Campo, Guatemala Ciudad de Guatemala (URL: http://crelosa.com/, post at https://www.youtube.com/watch?v=1P4kWqxU2m0&feature=youtu.be).

The current moderate explosive eruption of Ebeko has been ongoing since October 2016, with frequent ash explosions that have reached altitudes of 1.3-6 km (BGVN 42:08, 43:03, 43:06, 43:12, 44:12). Ashfall is common in Severo-Kurilsk, a town of about 2,500 residents 7 km ESE, where the Kamchatka Volcanic Eruptions Response Team (KVERT) monitor the volcano. During the reporting period, December 2019-May 2020, the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

During December 2019-May 2020, frequent explosions generated ash plumes that reached altitudes of 1.5-4.6 km (table 9); reports of ashfall in Severo-Kurilsk were common. Ash explosions in late April caused ashfall in Severo-Kurilsk during 25-30 April (figure 24), and the plume drifted 180 km SE on the 29th. There was also a higher level of activity during the second half of May (figure 25), when plumes drifted up to 80 km downwind.

Table 9. Summary of activity at Ebeko, December 2019-May 2020. S-K is Severo-Kurilsk (7 km ESE of the volcano). TA is thermal anomaly in satellite images. In the plume distance column, only plumes that drifted more than 10 km are indicated. Dates based on UTC times. Data courtesy of KVERT.

Figure 24. Photo of ash explosion at Ebeko at 2110 UTC on 28 April 2020, as viewed from Severo-Kurilsk. Courtesy of KVERT (L. Kotenko).

Figure 25. Satellite image of Ebeko from Sentinel-2 on 27 May 2020, showing a plume drifting SE. Image using natural color rendering (bands 4, 3, 2) courtesy of Sentinel Hub Playground.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); 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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

Piton de la Fournaise is a massive basaltic shield volcano on the French island of Réunion in the western Indian Ocean. Recent volcanism is characterized by multiple fissure eruptions, lava fountains, and lava flows (BGVN 44:11). The activity during this reporting period of November 2019-April 2020 is consistent with the previous eruption, including lava fountaining and lava flows. Information for this report comes from the Observatoire Volcanologique du Piton de la Fournaise (OVPF) and various satellite data.

Activity during November 2019-January 2020 was relatively low; no eruptive events were detected, according to OVPF. Edifice deformation resumed during the last week in December and continued through January. Seismicity significantly increased in early January, registering 258 shallow earthquakes from 1-16 January. During 17-31 January, the seismicity declined, averaging one earthquake per day.

Two eruptive events took place during February-April 2020. OVPF reported that the first occurred from 10 to 16 February on the E and SE flanks of the Dolomieu Crater. The second took place during 2-6 April. Both eruptive events began with a sharp increase in seismicity accompanied by edifice inflation, followed by a fissure eruption that resulted in lava fountains and lava flows (figure 193). MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed the two eruptive events occurring during February-April 2020 (figure 194). Similarly, the MODVOLC algorithm reported 72 thermal signatures proximal to the summit crater from 12 February to 6 April. Both of these eruptive events were accompanied by SO2 emissions that were detected by the Sentinel-5P/TROPOMI instrument (figures 195 and 196).

Figure 193. Location maps of the lava flows on the E flank at Piton de la Fournaise on 10-16 February 2020 (left) and 2-6 April 2020 (right) as derived from SAR satellite data. Courtesy of OVPF-IPGP, OPGC, LMV (Monthly bulletins of the Piton de la Fournaise Volcanological Observatory, February and April 2020).

Figure 194. Two significant eruptive events at Piton de la Fournaise took place during February-April 2020 as recorded by the MIROVA system (Log Radiative Power). Courtesy of MIROVA.

Figure 195. Images of the SO2 emissions during the February 2020 eruptive event at Piton de la Fournaise detected by the Sentinel-5P/TROPOMI satellite. Top left: 10 February 2020. Top right: 11 February 2020. Bottom left: 13 February 2020. Bottom right: 14 February 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 196. Images of the SO2 emissions during the April 2020 eruptive event at Piton de la Fournaise detected by the Sentinel-5P/TROPOMI satellite. Left: 4 April 2020. Middle: 5 April 2020. Right: 6 April 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

On 10 February 2020 a seismic swarm was detected at 1027, followed by rapid deformation. At 1050, volcanic tremors were recorded, signaling the start of the eruption. Several fissures opened on the E flank of the Dolomieu Crater between the crater rim and at 2,000 m elevation, as observed by an overflight during 1300 and 1330. These fissures were at least 1 km long and produced lava fountains that rose up to 10 m high. Lava flows were also observed traveling E and S to 1,700 m elevation by 1315 (figures 197 and 198). The farthest flow traveled E to an elevation of 1,400 m. Satellite data from HOTVOLC platform (OPGC - University of Auvergne) was used to estimate the peak lava flow rate on 11 February at 10 m3/s. By 13 February only one lava flow that was traveling E below the Marco Crater remained active. OVPF also reported the formation of a cone, measuring 30 m tall, surrounded by three additional vents that produced lava fountains up to 15 m high. On 15 February the volcanic tremors began to decrease at 1400; by 16 February at 1412 the tremors stopped, indicating the end of the eruptive event.

Figure 197. Photo of a lava flow and degassing at Piton de la Fournaise on 10 February 2020. Courtesy of OVPF-IPGP.

Figure 198. Photos of the lava flows at Piton de la Fournaise taken during the February 2020 eruption by Richard Bouchet courtesy of AFP News Service.

Volcanism during the month of March 2020 consisted of low seismicity, including 21 shallow volcanic tremors and near the end of the month, edifice inflation was detected. A second eruptive event began on 2 April 2020, starting with an increase in seismicity during 0815-0851. Much of this seismicity was located on the SE part of the Dolomieu Crater. A fissure opened on the E flank, consistent with the fissures that were active during the February 2020 event. Seismicity continued to increase in intensity through 6 April located dominantly in the SE part of the Dolomieu Crater. An overflight on 5 April at 1030 showed lava fountains rising more than 50 m high accompanied by gas-and-steam plumes rising to 3-3.5 km altitude (figures 199 and 200). A lava flow advanced to an elevation of 360 m, roughly 2 km from the RN2 national road (figure 199). A significant amount of Pele’s hair and clusters of fine volcanic products were produced during the more intense phase of the eruption (5-6 April) and deposited at distances more than 10 km from the eruptive site (figure 201). It was also during this period that the SO2 emissions peaked (figure 196). The eruption stopped at 1330 after a sharp decrease in volcanic tremors.

Figure 199. Photos of a lava flow (left) and lava fountains (right) at Piton de la Fournaise during the April 2020 eruption. Left: photo taken on 2 April 2020 at 1500. Right: photo taken on 5 April 2020 at 1030. Courtesy of OVPF-IPGP (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, April 2020).

Figure 200. Photo of the lava fountains erupting from Piton de la Fournaise on 4 April 2020. Photo taken by Richard Bouchet courtesy of Geo Magazine via Jeannie Curtis.

Figure 201. Photos of Pele’s hair deposited due to the April 2020 eruption at Piton de la Fournaise. Samples collected near the Gîte du volcan on 7 April 2020 (left) and a cluster of Pele’s hair found near the Foc-Foc car park on 9 April 2020 (right). Courtesy of OVPF-IPGP (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, April 2020).

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

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); 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); GEO Magazine (AFP story at URL: https://www.geo.fr/environnement/la-reunion-fin-deruption-au-piton-de-la-fournaise-200397); AFP (URL: https://twitter.com/AFP/status/1227140765106622464, Twitter: @AFP, https://twitter.com/AFP); Jeannie Curtis (Twitter: @VolcanoJeannie, https://twitter.com/VolcanoJeannie).

Although tephrochronology has dated activity at Sabancaya back several thousand years, renewed activity that began in 1986 was the first recorded in over 200 years. Intermittent activity since then has produced significant ashfall deposits, seismic unrest, and fumarolic emissions. A new period of explosive activity that began in November 2016 has been characterized by pulses of ash emissions with some plumes exceeding 10 km altitude, thermal anomalies, and significant SO₂ plumes. Ash emissions and high levels of SO₂ continued each week during December 2019-May 2020. The Observatorio Vulcanologico INGEMMET (OVI) reports weekly on numbers of daily explosions, ash plume heights and directions of drift, seismicity, and other activity. The Buenos Aires Volcanic Ash Advisory Center (VAAC) issued three or four daily reports of ongoing ash emissions at Sabancaya throughout the period.

The dome inside the summit crater continued to grow throughout this period, along with nearly constant ash, gas, and steam emissions; the average number of daily explosions ranged from 4 to 29. Ash and gas plume heights rose 1,800-3,800 m above the summit crater, and multiple communities around the volcano reported ashfall every month (table 6). Sulfur dioxide emissions were notably high and recorded daily with the TROPOMI satellite instrument (figure 75). Thermal activity declined during December 2019 from levels earlier in the year but remained steady and increased in both frequency and intensity during April and May 2020 (figure 76). Infrared satellite images indicated that the primary heat source throughout the period was from the dome inside the summit crater (figure 77).

Table 6. Persistent activity at Sabancaya during December 2019-May 2020 included multiple daily explosions with ash plumes that rose several kilometers above the summit and drifted in many directions; this resulted in ashfall in communities within 30 km of the volcano. Satellite instruments recorded SO₂ emissions daily. Data courtesy of OVI-INGEMMET.

Figure 75. Sulfur dioxide anomalies were captured daily from Sabancaya during December 2019-May 2020 by the TROPOMI instrument on the Sentinel-5P satellite. Some of the largest SO2 plumes are shown here with dates listed in the information at the top of each image. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 76. Thermal activity at Sabancaya declined during December 2019 from levels earlier in the year but remained steady and increased slightly in frequency and intensity during April and May 2020, according to the MIROVA graph of Log Radiative Power from 23 June 2019 through May 2020. Courtesy of MIROVA.

Figure 77. Sentinel-2 satellite imagery of Sabancaya confirmed the frequent ash emissions and ongoing thermal activity from the dome inside the summit crater during December 2019-May 2020. Top row (left to right): On 6 December 2019 a large plume of steam and ash drifted N from the summit. On 16 December 2019 a thermal anomaly encircled the dome inside the summit caldera while gas and possible ash drifted NW. On 14 April 2020 a very similar pattern persisted inside the crater. Bottom row (left to right): On 19 April an ash plume was clearly visible above dense cloud cover. On 24 May the infrared glow around the dome remained strong; a diffuse plume drifted W. A large plume of ash and steam drifted SE from the summit on 29 May. Infrared images use Atmospheric penetration rendering (bands 12, 11, 8a), other images use Natural Color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

The average number of daily explosions during December 2019 decreased from a high of 16 the first week of the month to a low of five during the last week. Six pyroclastic flows occurred on 10 December (figure 78). Tremors were associated with gas-and-ash emissions for most of the month. Ashfall was reported in Pinchollo, Madrigal, Lari, Maca, Achoma, Coporaque, Yanque, and Chivay during the first week of the month, and in Huambo and Cabanaconde during the second week (figure 79). Inflation of the volcano was measured throughout the month. SO₂ flux was measured by OVI as ranging from 2,500 to 4,300 tons per day.

Figure 78. Multiple daily explosions at Sabancaya produced ash plumes that rose several kilometers above the summit. Left image is from 5 December and right image is from 11 December 2019. Note pyroclastic flows to the right of the crater on 11 December. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-49-2019/INGEMMET Semana del 2 al 8 de diciembre de 2019 and RSSAB-50-2019/INGEMMET Semana del 9 al 15 de diciembre de 2019).

Figure 79. Communities to the N and W of Sabancaya recorded ashfall from the volcano the first week of December and also every month during December 2019-May 2020. The red zone is the area where access is prohibited (about a 12-km radius from the crater). Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-22-2020/INGEMMET Semana del 25 al 31 de mayo del 2020).

During January and February 2020 the number of daily explosions averaged 4-20. Ash plumes rose as high as 3.4 km above the summit (figure 80) and drifted up to 30 km in multiple directions. Ashfall was reported in Chivay, Yanque, and Achoma on 8 January, and in Huambo on 25 February. Sulfur dioxide flux ranged from a low of 1,200 t/d on 29 February to a high of 8,200 t/d on 28 January. Inflation of the edifice was measured during January; deformation changed to deflation in early February but then returned to inflation by the end of the month.

Figure 80. Ash plumes rose from Sabancaya every day during January and February 2020. Left: 11 January. Right: 28 February. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-02-2020/INGEMMET Semana del 06 al 12 de enero del 2020 and RSSAB-09-2020/INGEMMET Semana del 24 de febrero al 01 de marzo del 2020).

Explosions continued during March and April 2020, averaging 8-29 per day. Explosions appeared to come from multiple vents on 11 March (figure 81). Ash plumes rose 3 km above the summit during the first week of March and again the first week of April; they were lower during the other weeks. Ashfall was reported in Madrigal, Lari, and Pinchollo on 27 March and 5 April. On 17 April ashfall was reported in Maca, Ichupampa, Yanque, Chivay, Coporaque, and Achoma. Sulfur dioxide flux ranged from 1,900 t/d on 5 March to 10,700 t/d on 30 March. Inflation at depth continued throughout March and April with 10 +/- 4 mm recorded between 21 and 26 April. Similar activity continued during May 2020; explosions averaged 6-16 per day (figure 82). Ashfall was reported on 6 May in Chivay, Achoma, Maca, Lari, Madrigal, and Pinchollo; heavy ashfall was reported in Achoma on 12 May. Additional ashfall was reported in Achoma, Maca, Madrigal, and Lari on 23 May.

Figure 81. Explosions at Sabancaya on 11 March 2020 appeared to originate simultaneously from two different vents (left). The plume on 12 April was measured at about 2,500 m above the summit. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-11-2020/INGEMMET Semana del 9 al 15 de marzo del 2020 and RSSAB-15-2020/INGEMMET Semana del 6 al 12 de abril del 2020).

Figure 82. Explosions dense with ash continued during May 2020 at Sabancaya. On 11 and 29 May 2020 ash plumes rose from the summit and drifted as far as 30 km before dissipating. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya , RSSAB-20-2020/INGEMMET Semana del 11 al 17 de mayo del 2020 and RSSAB-22-2020/INGEMMET Semana del 25 al 31 de mayo del 2020).

Geologic Background. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Information Contacts: Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa, Peru (URL: http://ovi.ingemmet.gob.pe); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

The eruption at Sheveluch has continued for more than 20 years, with strong explosions that have produced ash plumes, lava dome growth, hot avalanches, numerous thermal anomalies, and strong fumarolic activity (BGVN 44:05). During this time, there have been periods of greater or lesser activity. The most recent period of increased activity began in December 2018 and continued through October 2019 (BGVN 44:11). This report covers activity between November 2019 to April 2020, a period during which activity waned. The volcano is monitored by the Kamchatka Volcanic Eruptions Response Team (KVERT) and Tokyo Volcanic Ash Advisory Center (VAAC).

During the reporting period, KVERT noted that lava dome growth continued, accompanied by incandescence of the dome blocks and hot avalanches. Strong fumarolic activity was also present (figure 53). However, the overall eruption intensity waned. Ash plumes sometimes rose to 10 km altitude and drifted downwind over 600 km (table 14). The Aviation Color Code (ACC) remained at Orange (the second highest level on a four-color scale), except for 3 November when it was raised briefly to Red (the highest level).

Figure 53. Fumarolic activity of Sheveluch’s lava dome on 24 January 2020. Photo by Y. Demyanchuk; courtesy of KVERT.

Table 14. Explosions and ash plumes at Sheveluch during November 2019-April 2020. Dates and times are UTC, not local. Data courtesy of KVERT and the Tokyo VAAC.

KVERT reported thermal anomalies over the volcano every day, except for 25-26 January, when clouds obscured observations. During the reporting period, thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm recorded hotspots on 10 days in November, 13 days in December, nine days in January, eight days in both February and March, and five days in April. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected numerous hotspots every month, almost all of which were of moderate radiative power (figure 54).

Figure 54. Thermal anomalies at Sheveluch continued at elevated levels during November 2019-April 2020, as seen on this MIROVA Log Radiative Power graph for July 2019-April 2020. Courtesy of MIROVA.

High sulfur dioxide levels were occasionally recorded just above or in the close vicinity of Sheveluch by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite, but very little drift was observed.

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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/).

The ongoing eruption at Dukono is characterized by frequent explosions that send ash plumes to about 1.5-3 km altitude (0.3-1.8 km above the summit), although a few have risen higher. This type of typical activity (figure 13) continued through at least March 2020. The ash plume data below (table 21) were primarily provided by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and the Darwin Volcanic Ash Advisory Centre (VAAC). During the reporting period of October 2019-March 2020, the Alert Level remained at 2 (on a scale of 1-4) and the public was warned to remain outside of the 2-km exclusion zone.

Table 21. Monthly summary of reported ash plumes from Dukono for October 2019-March 2020. The direction of drift for the ash plume through each month was highly variable; notable plume drift each month was only indicated in the table if at least two weekly reports were consistent. Data courtesy of the Darwin VAAC and PVMBG.

Figure 13.Satellite image of Dukono from Sentinel-2 on 12 November 2019, showing an ash plume drifting E. Image uses natural color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

During the reporting period, high levels of sulfur dioxide were only recorded above or near the volcano during 30-31 October and 4 November 2019. High levels were recorded by the Ozone Mapping and Profiler Suite (OMPS) instrument aboard the Suomi National Polar-orbiting Partnership (NPP) satellite on 30 October 2019, in a plume drifting E. The next day high levels were also recorded by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite on 31 October (figure 14) and 4 November 2019, in plumes drifting SE and NE, respectively.

Figure 14. Sulfur dioxide emission on 31 October 2019 drifting E, probably from Dukono, as recorded by the TROPOMI instrument aboard the Sentinel-5P satellite. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Geologic Background. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

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/); 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/); 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).

Mount Etna is a stratovolcano located on the island of Sicily, Italy, with historical eruptions that date back 3,500 years. The most recent eruptive period began in September 2013 and has continued through March 2020. Activity is characterized by Strombolian explosions, lava flows, and ash plumes that commonly occur from the summit area, 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. This reporting period covers information from October 2019 through March 2020 and includes frequent explosions and ash plumes. The primary source of information comes from the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Summary of activity during October 2019-March 2020. Strombolian activity and gas-and-steam and ash emissions were frequently observed at Etna throughout the entire reporting period, according to INGV and Toulouse VAAC notices. Activity was largely located within the main cone (Voragine-Bocca Nuova complex), the Northeast Crater (NEC), and the New Southeast Crater (NSEC). On 1, 17, and 19 October, ash plumes rose to a maximum altitude of 5 km. Due to constant Strombolian explosions, ground observations showed that a scoria cone located on the floor of the VOR Crater had begun to grow in late November and again in late January 2020. A lava flow was first detected on 6 December at the base of the scoria cone in the VOR Crater, which traveled toward the adjacent BN Crater. Additional lava flows were observed intermittently throughout the reporting period in the same crater. On 13 March, another small scoria cone had formed in the main VOR-BN complex due to Strombolian explosions.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows multiple episodes of thermal activity varying in power from 22 June 2019 to March 2020 (figure 286). The power and frequency of these thermal anomalies significantly decreased between August to mid-September. The pulse of activity in mid-September reflected a lava flow from the VOR Crater (BGVN 44:10). By late October through November, thermal anomalies were relatively weaker and less frequent. The next pulse in thermal activity reflected in the MIROVA graph occurred in early December, followed by another shortly after in early January, both of which were due to new lava flows from the VOR Crater. After 9 January the thermal anomalies remained frequent and strong; active lava flows continued through March accompanied by Strombolian explosions, gas-and-steam, SO2, and ash emissions. The most recent distinct pulse in thermal activity was seen in mid-March; on 13 March, another lava flow formed, accompanied by an increase in seismicity. This lava flow, like the previous ones, also originated in the VOR Crater and traveled W toward the BN Crater.

Figure 286. Multiple episodes of varying activity at Etna from 22 June 2019 through March 2020 were reflected in the MIROVA thermal energy data (Log Radiative Power). Courtesy of MIROVA.

Activity during October-December 2019. During October 2019, VONA (Volcano Observatory Notice for Aviation) notices issued by INGV reported ash plumes rose to a maximum altitude of 5 km on 1, 17, and 19 October. Strombolian explosions occurred frequently. Explosions were detected primarily in the VOR-BN Craters, ejecting coarse pyroclastic material that fell back into the crater area and occasionally rising above the crater rim. Ash emissions rose from the VOR-BN and NEC while intense gas-and-steam emissions were observed in the NSEC (figure 287). Between 10-12 and 14-20 October fine ashfall was observed in Pedara, Mascalucia, Nicolosi, San Giovanni La Punta, and Catania. In addition to these ash emissions, the explosive Strombolian activity contributed to significant SO2 plumes that drifted in different directions (figure 288).

Figure 287. Webcam images of ash emissions from the NE Crater at Etna from the a) CUAD (Catania) webcam on 10 October 2019; b) Milo webcam on 11 October 2019; c) Milo webcam on 12 October 2019; d) M.te Cagliato webcam on 13 October 2019. Courtesy of INGV (Report 42/2019, ETNA, Bollettino Settimanale, 07/10/2019 - 13/10/2019, data emissione 15/10/2019).

Figure 288. Strombolian activity at Etna contributed to significant SO2 plumes that drifted in multiple directions during the intermittent explosions in October 2019. Top left: 1 October 2019. Top right: 2 October 2019. Middle left: 15 October 2019. Middle right: 18 October 2019. Bottom left: 13 November 2019. Bottom right: 1 December 2019. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

The INGV weekly bulletin covering activity between 25 October and 1 November 2019 reported that Strombolian explosions occurred at intervals of 5-10 minutes from within the VOR-BN and NEC, ejecting incandescent material above the crater rim, accompanied by modest ash emissions. In addition, gas-and-steam emissions were observed from all the summit craters. Field observations showed the cone in the crater floor of VOR that began to grow in mid-September 2019 had continued to grow throughout the month. During the week of 4-10 November, Strombolian activity within the Bocca Nuova Crater was accompanied by gas-and-steam emissions. The explosions in the VOR Crater occasionally ejected incandescent ejecta above the crater rim (figures 289 and 290). For the remainder of the month Strombolian explosions continued in the VOR-BN and NEC, producing sporadic ash emissions. Isolated and discontinuous explosions in the New Southeast Crater (NSEC) also produced fine ash, though gas-and-steam emissions still dominated the activity at this crater. Additionally, the explosions from these summit craters were frequently accompanied by strong SO2 emissions that drifted in different directions as discrete plumes.

Figure 289. Photo of Strombolian activity and crater incandescence in the Voragine Crater at Etna on 15 November 2019. Photo by B. Behncke, taken by Tremestieri Etneo. Courtesy of INGV (Report 47/2019, ETNA, Bollettino Settimanale, 11/11/2019 - 17/11/2019, data emissione 19/11/2019).

Figure 290. Webcam images of summit crater activity during 26-29 November and 1 December 2019 at Etna. a) image recorded by the high-resolution camera on Montagnola (EMOV); b) and c) webcam images taken from Tremestieri Etneo on the southern slope of Etna showing summit incandescence; d) image recorded by the thermal camera on Montagnola (EMOT) showing summit incandescence at the NSEC. Courtesy of INGV (Report 49/2019, ETNA, Bollettino Settimanale, 25/11/2019 - 01/12/2019, data emissione 03/12/2019).

Frequent Strombolian explosions continued through December 2019 within the VOR-BN, NEC, and NSEC Craters with sporadic ash emissions observed in the VOR-BN and NEC. On 6 December, Strombolian explosions increased in the NSEC; webcam images showed incandescent pyroclastic material ejected above the crater rim. On the morning of 6 December a lava flow was observed from the base of the scoria cone in the VOR Crater that traveled toward the adjacent Bocca Nuova Crater. INGV reported that a new vent opened on the side of the saddle cone (NSEC) on 11 December and produced explosions until 14 December.

Activity during January-March 2020. On 9 January 2020 an aerial flight organized by RAI Linea Bianca and the state police showed the VOR Crater continuing to produce lava that was flowing over the crater rim into the BN Crater with some explosive activity in the scoria cone. Explosive Strombolian activity produced strong and distinct SO2 plumes (figure 291) and ash emissions through March, according to the weekly INGV reports, VONA notices, and satellite imagery. Several ash emissions during 21-22 January rose from the vent that opened on 11 December. According to INGV’s weekly bulletin for 21-26 January, the scoria cone in the VOR crater produced Strombolian explosions that increased in frequency and contributed to rapid cone growth, particularly the N part of the cone. Lava traveled down the S flank of the cone and into the adjacent Bocca Nuova Crater, filling the E crater (BN-2) (figure 292). The NEC had discontinuous Strombolian activity and periodic, diffuse ash emissions.

Figure 291. Distinct SO2 plumes drifting in multiple directions from Etna were visible in satellite imagery as Strombolian activity continued through March 2020. Top left: 21 January 2020. Top right: 2 February 2020. Bottom left: 10 March 2020. Bottom right: 19 March 2020. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Figure 292. a) A map of the lava field at Etna showing cooled flows (yellow) and active flows (red). The base of the scoria cone is outlined in black while the crater rim is outlined in red. b) Thermal image of the Bocca Nuova and Voragine Craters. The bright orange is the warmest temperature measure in the flow. Courtesy of INGV, photos by Laboratorio di Cartografia FlyeEye Team (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

Strombolian explosions continued into February 2020, accompanied by ash emissions and lava flows from the previous months (figure 293). During 17-23 February, INGV reported that some subsidence was observed in the central portion of the Bocca Nuova Crater. During 24 February to 1 March, the Strombolian explosions ejected lava from the VOR Crater up to 150-200 m above the vent as bombs fell on the W edge of the VOR crater rim (figure 294). Lava flows continued to move into the W part of the Bocca Nuova Crater.

Figure 293. Webcam images of A) Strombolian activity and B) effusive activity fed by the scoria cone grown inside the VOR Crater at Etna taken on 1 February 2020. C) Thermal image of the lava field produced by the VOR Crater taken by L. Lodato on 3 February (bottom left). Image of BN-1 taken by F. Ciancitto on 3 February in the summit area (bottom right). Courtesy of INGV; Report 06/2020, ETNA, Bollettino Settimanale, 27/01/2020 - 02/02/2020, data emissione 04/02/2020 (top) and Report 07/2020, ETNA, Bollettino Settimanale, 03/02/2020 - 09/02/2020, data emissione 11/02/2020 (bottom).

Figure 294. Photos of the VOR intra-crater scoria cone at Etna: a) Strombolian activity resumed on 25 February 2020 from the SW edge of BN taken by B. Behncke; b) weak Strombolian activity from the vent at the base N of the cone on 29 February 2020 from the W edge of VOR taken by V. Greco; c) old vent present at the base N of the cone, taken on 17 February 2020 from the E edge of VOR taken by B. Behncke; d) view of the flank of the cone, taken on 24 February 2020 from the W edge of VOR taken by F. Ciancitto. Courtesy of INGV (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

During 9-15 March 2020 Strombolian activity was detected in the VOR Crater while discontinuous ash emissions rose from the NEC and NSEC. Bombs were found in the N saddle between the VOR and NSEC craters. On 9 March, a small scoria cone that had formed in the Bocca Nuova Crater and was ejecting bombs and lava tens of meters above the S crater rim. The lava flow from the VOR Crater was no longer advancing. A third scoria cone had formed on 13 March NE in the main VOR-BN complex due to the Strombolian explosions on 29 February. Another lava flow formed on 13 March, accompanied by an increase in seismicity. The weekly report for 16-22 March reported Strombolian activity detected in the VOR Crater and gas-and-steam and rare ash emissions observed in the NEC and NSEC (figure 295). Explosions in the Bocca Nuova Crater ejected spatter and bombs 100 m high.

Figure 295. Map of the summit crater area of Etna showing the active vents and lava flows during 16-22 March 2020. 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. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Courtesy of INGV (Report 13/2020, ETNA, Bollettino Settimanale, 16/03/2020 - 22/03/2020, data emissione 24/03/2020).

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/); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/aeroweb/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Boris Behncke, Sonia Calvari, and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: https://twitter.com/etnaboris, Image at https://twitter.com/etnaboris/status/1183640328760414209/photo/1).

Merapi is a highly active stratovolcano located in Indonesia, just north of the city of Yogyakarta. The current eruption episode began in May 2018 and was characterized by phreatic explosions, ash plumes, block avalanches, and a newly active lava dome at the summit. This reporting period updates information from October 2019-March 2020 that includes explosions, pyroclastic flows, ash plumes, and ashfall. 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) and Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM).

Some ongoing lava dome growth continued in October 2019 in the NE-SW direction measuring 100 m in length, 30 m in width, and 20 m in depth. Gas-and-steam emissions were frequent, reaching a maximum height of 700 m above the crater on 31 October. An explosion at 1631 on 14 October removed the NE-SW trending section of the lava dome and produced an ash plume that rose 3 km above the crater and extended SW for about 2 km (figures 90 and 91). The plume resulted in ashfall as far as 25 km to the SW. According to a Darwin VAAC notice, a thermal hotspot was detected in HIMAWARI-8 satellite imagery. A pyroclastic flow associated with the eruption traveled down the SW flank in the Gendol drainage. During 14-20 October lava flows from the crater generated block-and-ash flows that traveled 1 km SW, according to BPPTKG.

Figure 90. An ash plume rising 3 km above Merapi on 14 October 2019.

Figure 91. Webcam image of an ash plume rising above Merapi at 1733 on 14 October 2019. Courtesy of BPPTKG via Jaime S. Sincioco.

At 0621 on 9 November 2019, an eruption produced an ash plume that rose 1.5 km above the crater and drifted W. Ashfall was observed in the W region as far as 15 km from the summit in Wonolelo and Sawangan in Magelang Regency, as well as Tlogolele and Selo in Boyolali Regency. An associated pyroclastic flow traveled 2 km down the Gendol drainage on the SE flank. On 12 November aerial drone photographs were used to measure the volume of the lava dome, which was 407,000 m3. On 17 November, an eruption produced an ash plume that rose 1 km above the crater, resulting in ashfall as far as 15 km W from the summit in the Dukun District, Magelang Regency (figure 92). A pyroclastic flow accompanying the eruption traveled 1 km down the SE flank in the Gendol drainage. By 30 November low-frequency earthquakes and CO2 gas emissions had increased.

Figure 92. An ash plume rising 1 km above Merapi on 17 November 2019. Courtesy of BPPTKG.

Volcanism was relatively low from 18 November 2019 through 12 February 2020, characterized primarily by gas-and-steam emissions and intermittent volcanic earthquakes. On 4 January a pyroclastic flow was recorded by the seismic network at 2036, but it wasn’t observed due to weather conditions. On 13 February an explosion was detected at 0516, which ejected incandescent material within a 1-km radius from the summit (figure 93). Ash plumes rose 2 km above the crater and drifted NW, resulting in ashfall within 10 km, primarily S of the summit; lightning was also seen in the plume. Ash was observed in Hargobinangun, Glagaharjo, and Kepuharjo. On 19 February aerial drone photographs were used to measure the change in the lava dome after the eruption; the volume of the lava had decreased, measuring 291,000 m3.

Figure 93. Webcam image of an ash plume rising from Merapi at 0516 on 13 February 2020. Courtesy of MAGMA Indonesia and PVMBG.

An explosion on 3 March at 0522 produced an ash plume that rose 6 km above the crater (figure 94), resulting in ashfall within 10 km of the summit, primarily to the NE in the Musuk and Cepogo Boyolali sub-districts and Mriyan Village, Boyolali (3 km from the summit). A pyroclastic flow accompanied this eruption, traveling down the SSE flank less than 2 km. Explosions continued to be detected on 25 and 27-28 March, resulting in ash plumes. The eruption on 27 March at 0530 produced an ash plume that rose 5 km above the crater, causing ashfall as far as 20 km to the W in the Mungkid subdistrict, Magelang Regency, and Banyubiru Village, Dukun District, Magelang Regency. An associated pyroclastic flow descended the SSE flank, traveling as far as 2 km. The ash plume from the 28 March eruption rose 2 km above the crater, causing ashfall within 5 km from the summit in the Krinjing subdistrict primarily to the W (figure 94).

Figure 94. Images of ash plumes rising from Merapi during 3 March (left) and 28 March 2020 (right). Images courtesy of BPPTKG (left) and PVMBG (right).

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 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive 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 during historical time.

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/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/, Twitter: https://twitter.com/BNPB_Indonesia); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); 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/); Jamie S. Sincioco, Phillipines (Twitter: @jaimessincioco, Image at https://twitter.com/jaimessincioco/status/1227966075519635456/photo/1).

Our last report on Copahue volcano described the phreato-magmatic eruption of July 2000 (BGVN 25:06). Up until July 2012, activity at Copahue was characterized by passive degassing. In this report, we summarize the changes registered from Copahue which culminated in minor ash eruptions. According to Instituto Nacional de Prevención Sísmica (INPRES), a phreatic eruption occurred on 19 July 2012 and Servicio Nacional de Geologia y Mineria (SERNAGEOMIN) reported that ash emissions continued intermittently during December 2012-December 2013.

INPRES and Forte and others (2012) noted that seismicity increased in the region of Copahue after the Mw 8.8 earthquake that occurred 3 km W of the Chilean shoreline on 27 February 2010. This activity was coincident with a progressive increase in fumarolic activity from the crater lake, El Agrio. A dense plume of vapor and acidic gases were frequently observed between 200-300 meters above the crater rim (figure 7).

Figure 7. Vapor and acidic gases rose in a column from Copahue crater lake on 17 July 2012. Courtesy of Nicolas Sieburger, a local guide who frequented the area.

According to Vélez and others (2011), differential interferometry (DInSAR) studies performed with ENVISAT radar images of Copahue's flanks suggested changes in deformation trends dominated by deflation during 2003-2008 and inflation during November-December 2011. A deformation map constructed between November 2011 and Aril 2012 showed uplift with displacements up to 7 cm (Vélez, 2012).

During March 2012, acidic water from the crater lake and hot springs on the E flank of the volcano was analyzed by Caselli and others (2012) and Agusto and others (in progress). The acidity (pH2, Cl, and F) showed unusually high values. These investigators also highlighted a significant decrease in the level of Copahue's crater lake waterline.

In July 2012, several seismic events of high and low frequency spectral content were reported by INPRES. Simultaneously, intense bubbling was observed in the SW area of Copahue's crater at an interval of 1 to 3 minutes (figure 8). A small explosion was reported on 17 July 2012 and photographed by a local guide (figure 9); it consisted of phreatic manifestations up to 10 meters high.

Figure 8. The crater lake of Copahue volcano on 17 July 2012: (A) the main emission point of intense bubbling was associated with steam, gas, and patches of sulfur floating on the lake surface; (B) detail of the area of bubbling. Courtesy of NicolÁs Sieburger.

Figure 9. A phreatic explosion from the SW sector of Copahue's crater lake during 17 July 2012. Although this photo lacks a scale and includes local clouds and/or steam, it is clear that the eruption plume was nearly black in color. Courtesy of Nicolás Sieburger.

On 19 July 2012, another phreatomagmatic explosion occurred with emissions of pyroclastic material that, according to SERNAGEOMIN, producing a plume that extending for ~18 km ESE (figure 10). The resulting proximal tephra included ash and fine- and coarse-sized lapilli up to 20 cm in diameter. A sample of this event recovered from the crater mainly consisted of sulfur-rich clasts with a low percentage of pumice fragments, scoriae fragments, irregular argillaceous white material, and accidental fragments. The pyroclastic material sampled displayed variable sizes (3-4 mm in diameter), mostly including globular morphology, and contained vesicles. Other morphologies included perfect spheres and elongated forms and like deformed drops (figure 11, A and B). Regarding glassy particles, different classes were identified according presence, size and shape of the vesicles, as vitreous pumiceous shards, platy, cuspate and blocky glass shards (figure 11 C and D). Further details of the particle morphology were obtained with SEM analysis (figure 12). Vitreous fragments showed similar composition to those described in 2000 eruption.

Figure 10. In this false-color Landsat satellite image of Copahue, the region affected by the 19 July 2012 ash plume is within the 20 km long, ESE-trending ellipse. Courtesy of Laura Vélez (GESVA).

Figure 11. Low magnification photo micrographs looking at key components from Copahue's July 2012 tephra deposits. Fragments shown are less than 4 mm in diameter and were chosen to highlight morphologic differences between sulfur particles (A and B) and vitreous shards (C and D). Photograph by R. Daga, Laboratorio Análisis por Activación Neutrónica (CAB-CNEA).

Figure 12. Scanning Electron Microscope (SEM) images of particles deposited from Copahue's July 2012 eruption. Images as follows: (A) subspherical sulfur particle; (B) botryoidal sulfur particle; (C) blocky and glassy particle; (D) fibrous glassy particles. Note the scale bars represent 500 μm for images A, C, and D while the scale bar for B is 1000 μm. Photograph by R. Daga, Laboratorio Análisis por Activación Neutrónica (CAB-CNEA).

A seismic array from the Grupo de Estudio y Seguimiento de Volcanes Activos (GESVA) had been installed near the town of Caviahue and it registered a wide range of seismicity during July 2012. GESVA documented volcano-tectonic events, hybrid events, long period events, tremor at various frequency ranges including harmonic tremor, and explosions. Several seismic swarms were reported during the phreatomagmatic eruption on 19 July 2012. GESVA is an investigative program within the geological department of the University of Buenos Aires.

On 26 July 2012 GESVA researchers conducted a new survey of the crater lake. All physical and chemical parameters showed high values with temperatures of 60°C at the lake margin, high acidity (pH

Continued unrest December 2012-December 2013. The Observatorio Volcanológico de los Andes del Sur-Servicio Nacional de Geologia y Mineria (OVDAS-SERNAGEOMIN) reported on 22 December 2012 an alert change from Orange to Red Alert at Copahue. This report highlighted the onset of harmonic tremor which lasted for 5 minutes and was immediately followed by two explosions. A camera maintained by OVDAS (~18 km SE) captured images of incandescence up to 200 m above the crater that correlated with the timing of the explosions. The observed height of the plume was between 1-1.5 km and it drifted SE (Figure 13).

Figure 13. This photographer captured scenes of the rising ash plume from Copahue on 23 December 2012. The lighter cloud in the background is probably a non-volcanic, lenticular cloud, a feature often associated with mountains. Photograph from the Municipio Caviahue-Copahue courtesy of La Nación.

Local newspapers reported that, on 23 December, ashfall and sulfur odors were limited to the proximal towns of Zapala (~150 km SE) and Cutral Co (~210 km SE). There were some reports of local citizens self-evacuating from the area due to anticipated ashfall. People within 15 km of the volcano and along drainages were warned about a potential increase in activity potentially including lahars. The municipalities of Villa La Angostura and Bariloche, located ~340 km S within Argentina, were not at risk during this event. In contrast, they had experienced heavy ashfall in 2011 due to Puyehue-Córdon Caulle's eruption.

The Buenos Aires Volcanic Ash Advisory Center (VAAC) reported at 1400 on 22 December 2012 that satellite images revealed a 110 km ash plume extending SE of Copahue; the plume was white and gray (figure 14). The plume persisted in satellite images during the next day, although its aerial extent later became restricted near the summit. By 24 December, the 22 December ash was only detected in an isolated area over the Atlantic Ocean.

Figure 14. The Buenos Aires VAAC released maps for the observed (left) and forecasted (right) location of Copahue's ash plume from 22 December 2012. A 12 hour and 18 hour forecast was also released that extended the plume due E, reaching the Atlantic Ocean. Later images disclosed a detached plume out over the Atlantic Ocean (see text). Courtesy of Buenos Aires VAAC.

VAAC reports indicated minor and possible ash emissions at the volcano on the following dates: 27, 28, and 30 December 2012; 2, 5, 9, and 10 January 2013; on 4 February; 28 and 29 March; on 12 April; on 15 November (possible ash was reported on 21 and 22 November). VAAC reports were also released intermittently during January-November 2013 due to gas emissions.

SERNAGEOMIN reduced the Alert Level from Red to Orange on 23 December 2012. The level was reduced again, on 28 December to Yellow, and was maintained until 5 January 2013 when seismicity increased (including three spasmodic tremor events). The webcamera also documented an increase in degassing that appeared to be gray and drifting E on 5 January; the Buenos Aires VAAC was able to track this minor ash plume. Alert Level Orange status continued until 17 January when it was decreased to Yellow.

The Alert Level fluctuated later in January (to and from Orange Alert) based on changing conditions which frequently included seismic swarms. One significant swarm, for example, occurred on 22 January.

Periodic incandescence was observed during February-May and SERNAGEOMIN reported small explosions of gas with minor ash on 7 and 15 May. On 19 May, OMI (Ozone Monitoring Instrument) detected elevated SO₂ emissions within 300 m above the crater. During 20 and 22 May, satellite images detected gray-colored plume that drifted up to 100 km SE. On 23 May, incandescence was observed as well as an increase in SO₂ flux as measured by the OMI satellite measurements; that activity triggered an increase in Alert Level to Orange.

Red Alert was announced one time in 2013 when, on 27 May, a seismic swarm began at a time of high RSAM measurements. An evacuation order was declared by SERNAGEOMIN that day for an area surrounding the volcano with a 25 km radius; they stated that the intensity and type of seismicity observed in the last few days and the deformation of the volcanic edifice suggested the rise of a magmatic body. Army trucks and buses were made available for the ~2,240 residents within that area, primarily those living in Alto Bío Bío. The swarm continued for several days into June. The Alert Level was reduced to Orange by 3 June. Local news sources reported that residents were authorized to begin returning to their homes on 6 June. The Alert Level was reduced to Yellow on 12 June and was maintained through the rest of 2013.

On 4 June 2013, the Hyperion sensor onboard the satellite EO-1 observed Copahue at 1333 UTC and a thermal anomaly was detected from the summit area of the volcano (figure 15). The calculated temperatures ranged from ~377 to ~647°C (personal communication, Ashley Davies, NASA Jet Propulsion Laboratory).

Figure 15. This satellite image captured a small point of elevated temperatures with the Hyperion sensor onboard EO-1; it was acquired on 4 June 2013 and composed of bands 2,1,3 (RGB). The image was obtained at a spatial resolution of 30 m per pixel. The north arrow and scale are approximate. Courtesy of Ashley Davies, NASA Jet Propulsion Laboratory.

An overflight of Copahue's summit was conducted on 9 June by OVDAS-SERNAGEOMIN in order to make observations of the area as reconnaissance for future installations of three seismometers. A 200 m plume was visible rising from the crater although no lava or lava dome was visible within the crater. There were sulfurous gas odors and the observers also noted that there were no indications of lahar flows outside of the crater.

On 23 and 26 August SERNAGEOMIN reported that incandescence was observed by the local webcamera; a possible ash event occurred on 26 June. Elevated SO₂ emissions were also detected by the Ozone Monitoring Instrument (OMI) on 23 August and during 5 days in September. Incandescence was reported during the last week of September.

On 16, 23, and 28 October, ash was observed by the local webcameras; the most energetic event occurred on 28 October. Elevated SO₂ was detected by OMI on during 21, 26, and 27 October.

SERNAGEOMIN reported in their November report that INSAR data from NASA determined that deformation of the edifice continued at a rate of 3.9 cm/year which was considered less than values measured earlier in the year. Incandescence was notable on 13 November and minor ash was reported on 16, 17, 18, 21, and 30 November. Elevated SO₂was detected by OMI on 29 November.

Small explosions were recorded on 10 December but ash was not confirmed. The local webcamera captured a plume that reached ~1,100 m above the crater. This event was accompanied by low-frequency seismicity.

MODVOLC Alerts 2012-2013: Elevated temperatures were detected by the MODIS sensors onboard the Aqua and Terra satellites during 2012-2013 (table 1). The MODVOLC system generated alerts on 11 days during the two years of unrest. During 2013, the alerts occurred in January and May on two separate days. While the local, SERNAGEOMIN webcamera recorded incandescence (particularly at night), the satellite remote sensing capabilities contended with cloudcover that frequently masked the area. For example, in January 2013 alone, there were 4 notable cases of nighttime incandescence (on 5, 8, 9, and 11 January).

Table 1. The MODVOLC system generated several thermal alerts during January 2012-May 2013. No additional alerts were generated during June-December 2013. Courtesy of HIGP.

References. Agusto, M. 2011. Estudio Geoquímico de Fluidos Volcánicos-Hidrotermales del complejo volcánico Copahue-Caviahue, y su Aplicación a Tareas de Seguimiento. Tesis de Doctorado. 296 páginas. Facultad de Cs. Exactas y Naturales. Universidad de Buenos Aires.

Agusto, M., Tassi, F., Capaccioni, B., Rouwet, D., Caselli. A., Vaselli, O. (en preparación). Chemical and isotopic compositions of fumarolic discharges from magmatic-hydrothermal system of Copahue volcano (Argentina). A combined (inorganic and organic) geochemical approach to understanding the origin of the fluid discharges.

Agusto, M., Caselli, A., Tassi, F., dos Santos Afonso, M., Vaselli. O. 2012. (aceptado). Caracterización y seguimiento geoquímico de las aguas Ácidas del sistema volcÁn Copahue - río Agrio: posible aplicación para la identificación de precursores eruptivos. Revista de la Asociación Geológica Argentina. ISSN 0004-4822.

Agusto, M., Vélez, ML., Caselli, A., Euillades, P., Tassi, F., Capaccioni, B., Vaselli, O. 2012. Correlación entre anomalías térmicas, geoquímicas y procesos deflacionarios en el volcán Copahue. XIII Congreso Geológico Chileno. Antofagasta, 2012. Actas: 429-431.

Caselli, A.T., Agusto M.R. y Fazio A., 2005. Cambios térmicos y geoquímicos del lago cratérico del volcán Copahue (Neuquén): posibles variaciones cíclicas del sistema volcánico. XVI Congreso Geológico Argentino, La Plata. Actas I: 751-756.

Caselli, A., Vélez, M.L., Agusto, M.R., Bengoa, C.L. Euillades, P.A. Ibañez, J.M., 2009. Copahue volcano (Argentina): A relationship between ground deformation, seismic activity and geochemical changes. Ed. Bean, Braiden, Lockmer, Martini and O'Brien.The VOLUME project.VOLcanoes: Understanding subsurface mass movement. Printed by jaycee. ISBN: 978-1-905254-39-2, pp 309-318.

Caselli, A., M. Agusto, B. Capaccioni, F. Tassi, G. Chiodini y D. Tardani. 2012. Aumento térmico y composicional de las aguas cratéricas del VolcÁn Copahue registradas durante el año 2012 (Neuquen, Argentina). XIII Congreso Geológico Chileno. Antofagasta, 2012. Actas: 435-436.

Forte, P., C. Bengoa, A. Caselli. 2012. AnÁlisis preliminar de la actividad sísmica del complejo volcÁnico Copahue-Caviahue mediante técnicas de array. XIII Congreso Geológico Chileno. Antofagasta, 2012. Actas: 568-570.

Ibañez J. M., Del Pezzo E., Bengoa, C., Caselli, A.T., Badi, G.A y J. Almendros. 2008. Volcanic tremor associated with the geothermal activity of Copahue volcano, Southern Andes region, Argentina. Journal of Volcanology and Geothermal Research (Elsevier, ISSN:0377-0273) 174: 284-294.

Tassi, F., Caselli, A., Vaselli, O., Agusto, M., Capecchiacci. F., 2007.Downstream composition of acidic volcanic waters discharged from Copahue crater lake (Argentina): the chemical evolution of Rio Agrio watershed. Federazione Italiana della Scienze della Tierra- FIST. Italia.

Varekamp, J.C., Ouimette, A.; HermÁn, S., Bermúdez, A.; Delpino, D., 2001. Hydrothermal element fluxes from Copahue, Argentina: A "beehive" volcano in turmoil. Geology, 29 (11): 1059-1062.

Varekamp, J.C., Ouimette, A.P., Herman, S.W., Flynn, K.S., Bermudez, A., Delpino, D., 2009. Naturally acid waters from Copahue volcano, Argentina. Applied Geochemistry 24, 208-220.

Vélez, M.L., 2011. Análisis de la deformación asociada al comportamiento de sistemas volcÁnicos activos: Volcán Copahue. Tesis Doctoral. Facultad Ciencias Exactas y Naturales - Universidad de Buenos Aires, 154 p.

Velez, M. L., Euillades, P., Caselli, A., Blanco, M., Díaz, J.M., 2011, Deformation of Copahue volcano: Inversion of InSAR data using a genetic algorithm, Journal of Volcanology and Geothermal Research, 202: 117-126.

Geologic Background. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

Information Contacts: Observatorio Volcanológico de los Andes del Sur-Servicio Nacional de Geologia y Mineria (OVDAS-SERNAGEOMIN), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Alberto Caselli and Laura Vélez, Grupo de Estudio y Seguimiento de Volcanes Activos (GESVA), Departamento Ciencias Geológicas, FCE y N, Universidad de Buenos Aires, Buenos Aires , Argentina (URL: http://www.gesva.gl.fcen.uba.ar/); D. Pablo Groeber (UBA-CONICET), FCEyN - UBA (URL: http://www.ifibyne.fcen.uba.ar/new/); G. Badi, Departamento de Sismología e I. M., Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata (URL: http://www.fcaglp.unlp.edu.ar/ciencia-y-tecnica/); R. Daga, Laboratorio AnÁlisis por Activación Neutrónica (CAB-CNEA) - CONICET y C. Cotaro, y C. Ayala, Grupo de Caracterización de materiales (CAB-CNEA) (URL: http://www2.cab.cnea.gov.ar/); P. Euillades, L. Euillades, M. Blanco, and S. Balbarani, Instituto CEDIAC - Facultad de Ingeniería Universidad Nacional de Cuyo (URL: https://fing.uncu.edu.ar/); M. Araujo, Instituto Nacional de Prevención Sísmica (INPRES) (URL: http://www.inpres.gov.ar/); Buenos Aires Volcanic Ash Advisory Center (VAAC) (URL: http://www.smn.gov.ar/vaac/buenosaires/productos.php); 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/); Simon Carn, NASA Global Sulfur Dioxide Monitoring, Aura/OMI (URL: https://so2.gsfc.nasa.gov/); La Nación, Buenos Aires, Argentina (URL: http://www.lanacion.com.ar/1539643-entro-en-erupcion-el-volcan-copahue); Dia a Dia, Buenoes Aires, Argentina (URL: http://www.diaadia.com.ar).

Since our last report on Etna (BGVN 36:05), which covered activity through 29 December 2010, intervals of vigorous activity (paroxysms) have continued, with 18 paroxysms in 2011, 7 in 2012, and 21 in 2013. During this reporting interval, 30 December 2010-31 December 2013, the activity can be viewed as a series of paroxysms detailed in a chronology shown below. Activity at the Northeast Crater (NEC) remained minor during the reporting interval. The Bocca Nuova produced activity in July and December 2011, and then in January 2013 where two episodes of intense Strombolian activity occurred on the evenings of 16 and 18 January.

In addition, during this reporting interval, there emerged a "New" Southeast crater (NSEC). The "old" SEC was last active in May 2007. NSEC formed at a large pyroclastic cone that grew alongside the SEC's active crater. The cone's early growth took place during seven paroxysmal episodes between January and July 2011, and continued to grow though the end of 2013.

Paroxysms at Etna. The term paroxysm, and its use in the phrase 'paroxysmal episode,' has become common in describing Etna's eruptive outbursts, particularly in the past few decades. INGV's Boris Behncke has described the behavior associated with these terms, employing both photos and videos widely available online. Paroxysm is a short-hand for Etna's often intense Strombolian discharges that frequently include lava fountaining, lava flow emission, and tephra columns, which erupted at the summit craters.

Behncke notes that Etna's typical paroxysm consists of three main phases: (1) prelude and waxing, (2) climax, and (3) waning and cessation. The climactic phase 2 part of the behavior represents the true paroxysm. To describe a collective set of all three phases at Etna, Behncke prefers that they be called "paroxysmal episode," "paroxysmal eruptive episode" or "eruptive episode."

Summary and chronology. Table 10 contains a 2011-2013 chronology of Etna's paroxysmal episodes at the NSEC as reported by INGV. There were 46 such episodes during the interval shown in the table. There are clear cases where the description of a single paroxysm glosses over complexities of the eruptive process (see, for example, the 30 July discussion in the next section).

Table 10. A list of NSEC paroxysmal episodes from Etna's New Southeast Crater and their numbering for 2011- 2013. The column at far right contains occasional notations of interesting or extraordinary events taken from INGV reporting. In some cases there are minor variations in dates and numbering.

Figure 142. A photo of NSEC in eruption during a paroxysm on the evening of 30 July 2011. The photo shows lava fountaining activity, ash plume, and lava flow from the new and actively growing cone on the E flank of Etna's old Southeast Crater (barely discernible at extreme left). The photo was taken from a point about 1 km to the SE of SEC but the height of the lava fountains were undisclosed. Photo taken by Marco Neri, INGV-Catania.

Regarding paroxysm number 8 (30-31 July 2011), INGV featured photos (e.g., figure 142) and made comments such as the following.

"About 19.00 h local time (= UTC-1), the mean amplitude of the volcanic tremor started to increase again, and so did the Strombolian activity. At around 19.30, a dilute gas and ash plume was again blown eastward by the wind. The Strombolian activity progressively gained in intensity, quite more rapidly than during the morning's activity, and the incandescent jets became continuous around 21.30 local time. At the same time, renewed lava overflow toward east showed a rapid increase in effusion rate, forming a multilobate flow down the western slope of the Valle del Bove, which traveled approximately 3 km down reaching about 2,000 m elevation by 2300 local time. The ash plume became denser and was blown eastward by the wind, generating ash falls in the Ionian sector of the volcano.

"During the phase of maximum intensity, fragments of fluid lava were violently thrown to heights of about 450-500 m above the crater rim, causing heavy fallout onto the external flanks of the pyroclastic cone to a distance of 200-300 m. Lava fountains were jetting from at least two vents located within the crater and on its upper east flank, roughly aligned west-northwest - east-southeast."

2013. There were two main phases of activity during 2013. The first occurred during January-April; the second, after a 6-month quiescence, began on 26 October (table 10).

Figure 143 shows a view of the paroxysmal event of 23 February 2013. Of the events listed during the first phase of 2013 (table 10), this was a particularly active one.

Figure 143. View of the Pizzi Deneri area in the aftermath of incandescent bombs falling during the peak of the 23 February 2013 paroxysm at the NSEC. Photo taken from the Rifugio Citelli, on Etna's NE flank. Photo taken by Daniele Pennisi and taken from INGV report.

INGV reported that eight eruptive events occurred between 26 October and 31 December 2013. The largest of these events occurred on 23 November 2013 and stood out as a noteworthy event in terms of amplitude. Figure 144 shows a scene from the episode on 2 December 2013.

Figure 144. Strong explosions at the end of the lava fountaining during the paroxysm of 2 December 2013 at Etna's New Southeast Crater, and lava flow directed toward the SE (at left). Note also the beginning of the formation of a small lava flow toward the NW, more to the right, forming a more luminous point on the cone's flank. Ballistics rose hundreds of meters. Photo taken from Macchia di Giarre by Walter Contarino, and INGV report.

Paroxysmal activity at Etna caused significant disruptions regionally during the reporting period; the Catania airport cancelled flights in and out of the airport several times. On 9 July 2011, Strombolian explosions turned into a continuous lava fountain; a dense eruptive plume rose several kilometers and drifted S and SE. Ash and lapilli from the plume fell in populated areas including Trecastagni, Viagrande, and Acireale (SE), and between Nicolosi and Catania (S), forcing the closure of the Fontanarossa international airport in Catania. In 2013, according to a news article, a representative from Catania airport noted activity at Etna prompted the closure of nearby airspace from before dawn through the early morning of 26 October 2013. According to another news article, the ash emissions caused the cancellation of more than 20 flights in and out of the Catania airport on 15 December 2013.

The New SEC (NSEC). The old SEC cone was last active in May 2007. The NSEC cone grew substantially between 12 January and 25 July 2011 (episodes 1-7) (table 10) and thereafter. Figure 145 shows a photo of the NSEC taken on 29 July 2011.

Figure 145. A photo of Etna's Southeast Crater (SEC) taken on 29 July 2011 from 1 km S of the SEC. The photo shows the large pyroclastic cone that has grown around the active crater, located on the E flank of the old SEC cone, during the seven paroxysmal episodes between 12 January and 25 July 2011. Photo taken by Boris Behncke, INGV-Catania.

Since its emergence in 2011, the NSEC grew substantially, especially in 2013. The size of NSEC can be seen relative to the old SEC in figure 146. Smaller and farther left (E) is the low cone Sudestino ('little southeast'), which grew during several paroxysmal episodes during the spring of 2000 just beyond the SEC's S side (BGVN 25:03; 25:09). The right upper half of the image is dominated by the NSEC cone, which grew entirely during the previous 10 months. INGV noted that during 2013 the NSEC cone expanded both in height and width.

Figure 146. A view of the Southeast Crater (SEC) complex at Etna as seen from the S on 14 December 2011. The "old" SEC cone is in the center and contains the conspicuous light colored area with wisps of fumarolic vapor and yellow sulfur deposits. The right half of the image shows the New SEC cone, which grew entirely during the previous 10 months. The large bombs and blocks in the foreground, with some clasts 3-5 m in diameter, were deposited during the paroxysmal episode of 15 November 2011. Mosaic composed of 3 photos taken by Boris Behncke, INGV-Osservatorio Etneo (Catania).

The October -December phase of Etna's 2013 activity is summarized in an INGV report from 22 January 2014 (B. Behncke & E. De Beni). Figure 147 shows a map of lava flows emanating from the NSEC during this phase of activity (26 October - 31 December 2013).

Figure 147. Map of the lava flows emitted at the NSEC from 26 October to 31 December 2013 and morphology of the NSEC cone updated in January 2014 (base map, August 2007). BN=Bocca Nuova; SEC = Southeast Crater; NSEC = New South East Crater. Taken from UFGV Report of 22 January 2014, (INGV, by B. Behncke and E. De Beni).

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

Following the phreatic eruption on 7 May 2013 that killed 7 climbers (BGVN 38:04), there has been little increase in volcanic activity at Mayon volcano. Seismicity has mostly receded to baseline levels, aside from occasional volcanic earthquakes. These earthquakes occur about once every other day, with minimal earthquakes in June and September. The activity reported by the Philippine Institute of Volcanology and Seismology (PHIVOLCS) in table 12 below represents a continuation of table 11 from a previous Bulletin report (BGVN 34:12). Rockfalls and earthquakes are plotted in figure 22.

Table 12. Almost daily summaries of observations at Mayon, including seismicity and SO₂emission rates during 1 June -23 November 2013. Number of events represent counts from the seismic monitoring network over a 24-hour period prior to the stated reporting date/time (except as noted). For example RF: 1 means 1 rockfall; and VE: 2 means 2 volcanic earthquakes. Rockfall events are related to the detachment of lava fragments at the volcano's upper slopes. No ash explosions were recorded during this time period. SO2 emission rates, measured by FLYSPEC [a miniature, light-weight ultraviolet correlation spectrometer (Horton and others, 2006)], are for the day before the reporting date. Courtesy of PHIVOLCS.

Figure 22. Graph showing distribution of volcanic earthquakes and rockfalls from June 2013 to November 2013. Created by Bulletin editors from PHIVOLCS reports.

When cloud cover and heavy rain does not inhibit observations, PHIVOLCS had consistently recorded white steam plumes that drifted in various directions from June to November 2013. Bluish fumes, a sign of hydrogen sulfide, were witnessed on 5 and 7 June, 15 and 23 August, and 7 and 28 September. Ground deformation surveys in the second week of August showed that the inflationary trend was continuing. In May 2013, electronic tilt meters measured Mayon's edifice to be slightly inflated compared to January 2010.

Crater glow of Intensity 1 was observed numerous times from June to September. According PHIVOLCS, a crater glow of Intensity 1 is faint, Intensity 2 is more visible to the naked eye, Intensity 3 is bright, and Intensity 4 is intense. Crater glow likely results from incandescence of new lava, or newly exposed lava, reflecting off local crater walls, clouds, or steam.

PHIVOLCS interprets enhanced crater glow as a sign of SO₂ clouds, but there had been little SO₂ fluctuation from June to November. Mayon's Alert status remained at Level 1 following the increase from Level 0 on 31 May 2013. However, PHIVOLCS continues to advise residents and visitors to avoid the 6-kilometer radius Permanent Danger Zone (PDZ) due to hazards such as rockfalls, landslides, sudden ash emissions, and phreatic eruptions. Level 1 is the 2nd value on a scale from 0 to 5, with 5 signifying an ongoing hazardous eruption; level 1 indicates an abnormal condition, but no magmatic eruption is imminent.

On 6 November 2013, PHIVOLCS issued a warning for super-typhoon Haiyan, locally known as Yolanda, indicating that excessive rainfall might trigger landslides and lahars at Mayon. Peak winds during Haiyan were consistently 170 mph, making the storm a super-typhoon as classified by NOAA ("maximum sustained 1-minute surface winds of at least [150 miles per hour]"). With the potential of large-magnitude lahars, the province of Albay started an evacuation of about 103,200 people along areas downstream, as shown in figure 23. According to the news source, Inquirer, adjacent communities, including Guinobatan, Legaspi City, Sto. Domingo, Daraga and Ligao City, were at risk for inundation, burial and washout. PHIVOLCS also issued precautions concerning debris flows from landslides of Mt. Masaraga, an old volcanic edifice N of Mayon.

Figure 23. Super-typhoon Haiyan left destruction in its wake after hitting the Philippines in early November. In this photo from the Associated Press, residents downstream from Mayon were evacuated due to the possibility of lahars engulfing nearby communities (Daily Mail).

Geologic Background. Beautifully symmetrical Mayon, which rises above the Albay Gulf NW of Legazpi City, is the Philippines' most active volcano. The structurally simple edifice has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions date back to 1616 and range from Strombolian to basaltic Plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas. A violent eruption in 1814 killed more than 1,200 people and devastated several towns.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS); Associated Press (URL: http://www.ap.org/); Daily Mail (URL: http://www.dailymail.co.uk); NOAA (URL: http://www.aoml.noaa.gov); and Philippine Daily Inquirer (URL: http://www.inquirer.net/).

In an activity report on 31 August 2011, the Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) indicated that Poás had experienced intense phreatic activity between 2006 and mid-2011. In June 2011, however, the frequency of eruptions began to decrease dramatically. The report also indicated that Laguna Caliente, the hot, acid crater lake on the northern summit, had shrunk by about 94 percent between 2006 and mid-2011; during this same period, the lake's pH had decreased from 1.22 to minus 0.72 and its water temperature had increased from 32°C to 62°C. One explosion, on 25 December 2009, apparently opened a more permanent vent at the crater lake's bottom. On the S edge of the lake is a dome (that OVSICORI-UNA sometimes in their reports refers to as a "cryptodome"), where frequent, intense degassing has occurred. The lake exhibits vigorous convective activity, and acid rain is frequently observed.

Our previous report (BGVN 36:04) discussed activity through February 2011. This report presents activity between that date and 31 December 2013. Figure 100 indicates the location of the volcano in Costa Rica. A photo of the active crater and surrounding area is shown in figure 101.

Figure 100. A Google map of Costa Rica showing the location of Poás. Courtesy of Google Maps.

Figure 101. Aerial photo of the active crater with the hot acid lake and dome ("cryptodome"), taken on 27 February 2011. Also, Lake Botos, a cold lake that fills an inactive crater, can also be seen S of the active crater. Courtesy of OVSICORI-UNA (E. Duarte).

Activity in 2011. An OVSICORI-UNA activity report from November 2011 and an annual 2012 summary indicated that the temperature of the dome had increased dramatically during early 2011 as the result of super-heated gas released through the dome. The temperature, measured by thermocouple, peaked in August 2011 at 890°C, and then decreased steadily thereafter through at least the end of 2012, when the temperature was about 100°C. In early 2011, incandescence could be seen at night; however, during June-September, it could also be seen during the day. This phenomenon had not occurred since 1981. OVSICORI-UNA speculated that the changes could be either from a recent magma intrusion or a change in the hydrothermal plumbing system.

A news article (Inside Costa Rica) reported that a team of geologists and volcanologists from the Universidad de Costa Rica visited Poás on 25 May 2011 and observed 18 phreatic explosions from Laguna Caliente during a three-hour period. According to the article, the volcano normally produced 1-2 explosions per day.

On 23 July 2011, OVSICORI-UNA scientists visited Poás to document changes during the previous weeks. They observed fumaroles with vigorous bluish emissions in the fractured rock about 40 m above the lake surface. Those emissions produced incandescence observable during the daylight. The emission temperature was 670°C at the dome's mid-wall. A separate report noted that the temperatures at the dome were unusually high, in the range of 700-890°C between June and October 2011. Scientists noted that on the SE shore of Laguna Caliente, a subtle, semicircular scarp observed a few months earlier had rapidly progressed to a sharp scarp. The 60-m-wide, 2.5-m-high scarp was degassing and geyser activity was observed on the W end, next to the lake.

OVSICORI-UNA visited the volcano again on 8 September 2011, and observed that two newly formed cavities at the N base of the dome had merged into a crater that was 25 m long and 7-10 m wide. The scientists also found incandescence reflected in the gas plume about 80 m from the edge of the lake to near the top N edge of the dome (figure 102 and 103). OVSICORI-UNA reported that a new fumarole had appeared on the crater during August-September 2011.

Figure 102. Night view from the larger caldera's E side on 8 September 2011, showing degassing and incandescence reflecting in the gas plume. The lights in the upper right of the photo are from a community about 15 km W from the volcano. Courtesy of OVSICORI-UNA (E. Duarte).

Figure 103. Night view (at 1800) showing Poás' incandescence on the dome and fumarolic activity. Photo taken from the E on 8 September 2011. Courtesy of OVSICORI-UNA.

According to OVSICORI-UNA, fumarolic activity continued during October 2011, with bluish gas plumes rising more than 1 km from the dome. Toward the end of the month, the fumarolic activity as well as incandescence from the dome had decreased. Phreatic activity continued. The lake temperature was 55°C and the level had risen 22 cm between 14 September and 27 October 2011.

OVSICORI-UNA reported that during fieldwork on 16 December 2011 scientists observed new geyser activity from a vent that had formed earlier in 2011 on the dome's N flank. A water-and-mud fountain rose 5-6 m high and flowed into the lake, resulting in a terrace along the S shore. Gas-and-steam plumes rose from the dome.

Activity in 2012. According to OVSICORI-UNA, at least 44-47 phreatic explosions were observed in 2012, either by the rangers of the Parque Nacional Volcán Poás (Poás Volcano National Park) or in seismic recordings. The number per month for the year ranged from 0 (in September) to 10 (in October). Sometimes these explosions were characterized by large bubbles of gas and liquid, under 500 m high. For example, during May 2012, eruptions occurred on 6, 15, 20 and 26 May. The eruption on 15 May was preceded by about 6 hours of very low amplitude harmonic tremor. Administrators at the National Park witnessed the explosion and reported that sediment, water, rock fragments, and plumes were ejected ~500 m above the lake surface. The lake level dropped ~0.9 m between 8 and 29 May, while the water temperature was steady during this period at ~48°C. Dome fumarole temperatures decreased during 2012, from ~700°C to ~100°C.

OVSICORI reported that higher amplitude, more frequent phreatic eruptions occurred in October 2012, especially during 18-27 October. Two phreatic explosions occurred on 27 October 2012. One of them ejected water, sulfur-rich sediments, and rock fragments onto the S and SW edges of the crater floor. According to a news article (The Tico Times), local residents heard a loud rumble at about 0100 on 28 October; a phreatic explosion ejected sediment 500 m above the lake, and produced ashfall several hundred meters away.

Between January and October 2012, the lake level decreased about 4 m; in November and December, the lake level rose by the same amount due to the high precipitation common at this time of year. Strong rainfall in November eroded the N flank of the dome.

Seismicity remained stable in 2012, with less than 200 daily earthquakes, mostly shallow low-frequency events. During 2012, the number of volcano-tectonic earthquakes remained low. The only significant seismicity occurred during 5-7 September, following the 5 September Nicoya earthquake (Mw 7.4) in the NW part of Costa Rica.

Activity in 2013. According to OVSICORI-UNA's annual report for 2013, seismic activity remained stable, with 10-150 earthquakes daily. Isolated small magnitude, shallow, volcano-tectonic earthquakes also occurred. Tremors were recorded infrequently and were of short duration. Hybrid earthquakes with large amplitudes (up to 3 cm² reduced displacement) began in September, peaked in October, and fell in November.

In March 2013, OVSICORI-UNA began to measure the concentration of CO₂, SO₂, and H₂S, using a portable multi-gas station provided by Italy's Istituto Nazionale di Geofisica e Vulcanologia (National Institute of Geophysics and Volcanology, INGV). In April 2013 the SO₂ emission, as measured by a portable DOAS (Differential Optical Absorption Spectroscopy), was 120 /-30 metric tons per day.

In 2013, the dome temperature rose from 100°C in January to values above 500° C during the middle of the year, resulting in incandescence observed at night during May 2013. For example, maximum temperatures of 575°C and 450°C were recorded on 8 and 30 May, respectively. Later in the year, temperatures decreased to as low as 200°C in October, before rising somewhat again. Before 2013, a thermocouple was used to measure temperatures; thereafter, both a thermocouple and a remote infrared camera were used.

Lake activity in 2013 was very similar to that reported for 2012, again characterized by sporadic phreatic eruptions (figure 104). The number of eruptions per month ranged from 4 (March, April, July) to 9 (May, October). The water level remained relatively constant at 4 m until about June-August when it decreased to as low as about 1.5 m, before rising again. During 2013, no significant change in water temperature (about 45-50°C) or pH (0-0.3) was noted, similar to measurements in 2012. For example, the lake temperature was about 46°C on 8 May 2013 and 48°C on 8 May 2012. The pH was 0.03 on 8 May 2013, compared to 0.07 on 8 May 2012.

Figure 104. Photo of phreatic eruption from Poás' Laguna Caliente on 20 August 2013. Courtesy of OVSICORI-UNA (G. Durán).

During 2013, rainfall was substantially less acidic, reflecting a decrease in the release of gases and heat through the active crater. Fumarolic activity was variable.

During the early morning hours on 2 and 3 June, residents reported a gas plume rising 1 km above the crater floor. OVSICORI-UNA observed that recent plumes had been hot (450-575°C) and rich in sulfur dioxide, giving the plumes a bluish-white color.

Geologic Background. The broad, well-vegetated edifice of Poás, one of the most active volcanoes of Costa Rica, contains three craters along a N-S line. The frequently visited multi-hued summit crater lakes of the basaltic-to-dacitic volcano, which is one of Costa Rica's most prominent natural landmarks, are easily accessible by vehicle from the nearby capital city of San José. A N-S-trending fissure cutting the 2708-m-high complex stratovolcano extends to the lower northern flank, where it has produced the Congo stratovolcano and several lake-filled maars. The southernmost of the two summit crater lakes, Botos, is cold and clear and last erupted about 7500 years ago. The more prominent geothermally heated northern lake, Laguna Caliente, is one of the world's most acidic natural lakes, with a pH of near zero. It has been the site of frequent phreatic and phreatomagmatic eruptions since the first historical eruption was reported in 1828. Eruptions often include geyser-like ejections of crater-lake water.

Information Contacts: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Inside Costa Rica (URL: http://www.insidecostarica.com/); The Tico Times (URL: http://www.ticotimes.net/).

The rift zone eruption that began at Puyehue-Cordón Caulle on 4 June 2011 (BGVN 37:03) persisted through early 2012 and declined toward the end of 2012. Relative quiescence was observed through October 2013, which is the end of this reporting period. The Observatorio Volcanológico de Los Andes del Sur-Servicio Nacional de Geología y Minería (OVDAS-SERNAGEOMIN) maintained Red Alert (the highest level in a four-color scale) from 4 June 2011 to 23 March 2012; declining activity led to a downgrade in the Alert Level on 23 March 2012 to Orange, and then again on 24 April to Yellow. The status remained at Yellow until 16 August 2012, when it decreased to Green. Green Alert was maintained through the end of this reporting period of October 2013.

Early stages of the eruption captured by remote sensing. Based on polar-orbiting satellites, scientists at the Montreal Volcanic Ash Advisory Centre (VAAC) were able to detect the volcanic ash cloud as it circled the southern hemisphere. Using a combination of infrared channels, five satellites contributed to a mosaic of data showing the wide dispersion of volcanic ash over the period of 4-6 June 2011 (figure 8). A mosaic created on 14 June 2011 captured the 4 June 2011 ash as it approached the Chilean coast while, at the same time, a new ash eruption was occurring at Puyehue-Cordón Caulle (figure 9).

Figure 8. Composite image of volcanic ash from Puyehue-Cordón Caulle as detected by satellites between 1937 on 4 June and 1551 on 6 June 2011. The 4-km resolution data was collected during 30 passes (satellites NOAA 15, 16, 18, 19, and MetOp-A) using a combination of infrared channels. The colors correspond to values of brightness temperature differences (i.e. ch4 - ch5) ranging from -0.5° C to -12° C. The image was produced at Montreal VAAC with the Terascan software and the NOAA CLASS data. Courtesy of René Servranckx, Meteorological Service of Canada.

Figure 9. (A) Composite image from NOAA satellites NOAA-19 and NOAA-18 capturing two different stages of ash plumes from Puyehue-Cordón Caulle. The large plume over the Pacific Ocean was generated by explosive activity on 4 June 2011 and circled the southern hemisphere within 10 days. At 1938 on 14 June 2011, a new ash plume was erupting, contributing additional ash in the atmosphere. (B) Five satellites contributed to this image of Cordón Caulle's ash plume during 14-16 June 2011. With 4 km resolution, the image comprises 56 satellite passes using a combination of infrared channels. The color coding corresponds to values in the range of -1.5° C to -10.0° C. Both images were produced at Montreal VAAC with Terascan software and data retrieved from the NOAA CLASS website. Courtesy of René Servranckx, Meteorological Service of Canada.

Post-processing of satellite images from GOES-13 highlighted the strong thermal anomalies that occurred during the early stages of the eruption. Daniel Lindsey of NOAA prepared a video sequence of images during 12-14 June 2011 that provided a clear way to identify the ash plume extending across Chile and Argentina (figure 10). From those images, it was possible to infer that a significant amount of ash was released from this eruption based on the persistent cold infrared brightness temperatures.

Figure 10. Images of GOES-13 data show the extent of elevated cold infrared brightness temperatures and the ash plume from Puyehue-Cordón Caulle at four different times: 12 June 2011 at 1139, 12 June at 1309, 13 June 2011 at 0639, and 13 June at 1439; all times given in UTC. The purple color in these infrared layers corresponds to approximately -40 to -50°C. The location of Cordón Caulle is marked with a red triangle. Courtesy of Daniel Lindsey of NOAA/NESDIS/STAR/RAMM Branch.

Based on webcamera observations, OVDAS-SERNAGEOMIN reported that incandescence was visible during 23 February-30 April 2012 and, at times, the local webcam views captured incandescence reaching up to 600 m above the rim (table 2).

Table 2. Seismicity and observations of Cordón Caulle's eruption during 2012 were documented in regular reports from OVDAS- SERNAGEOMIN. This table highlights data from 23 February to 22 April. Note that incandescence and plume heights correspond to km above the crater. Courtesy of SERNAGEOMIN-OVDAS.

Based on seismicity and visual observations, declining activity was noted from late April 2012 through October 2013 (table 3). Incandescence and plumes from the crater were rarely documented, partly due to poor weather conditions. Seismicity was reported in terms of individual counts and, after the Alert Level was downgraded to Green, seismicity rarely exceeded 20 events per month.

Table 3. Activity at Puyehue-Cordón Caullefrom 24 April 2012 to 31 October 2013. Earthquake types, volcano-tectonic and long-period are abbreviated with VT and LP, respectively. MD refers to magnitudes calculated from signal duration; RD is the abbreviation for reduced duration. Courtesy of SERNAGEOMIN-OVDAS.

Although activity had diminished significantly by April 2012, field researchers determined that the rhyolitic dome material remained mobile. In an interview with Earthweek released on 15 November 2013, Hugh Tuffen of Lancaster University explained that, "the lava was still oozing after almost a year, and it advances between 1 and 3 meters a day." Fieldwork yielded results later published in 2013 that highlighted the heterogeneity of processes (brittle and ductile) that could have existed in order to allow rhyolitic magma to travel explosively and effusively to the surface. This investigation included video documentation of explosive phases of the eruption in 2012 (figure 11).

Figure 11. This series of images includes: (a) a location map for Puyehue-Cordón Caulle; (b) a NASA ALI image taken on 26 January 2012 including annotated locations of observation points (red star) and the red box corresponds to the area in "c"; (c) the overlapping vent structures and ash plumes were captured in this GeoEye-1 image from 3 July 2012; (d) and this panorama of the active lava flow observed on 10 January 2012 (note that the scale is approximate). Original images are from Schipper and others, 2013.

References. Earthweek: A diary of the planet, 15 Nov. 2013, http://www.earthweek.com/2013/ew131115/ew131115d.html.

Schipper, C.I., Castro, J.M., Tuffen, H., James, M.R., and How, P., 2013. Shallow vent architecture during hybrid explosive-effusive activity at Cordón Caulle (Chile, 2011-12): Evidence from direct observations and pyroclast textures, Journal of Volcanology and Geothermal Research, 262: 25-37.

Links for full animation of IR images from GOES-13 data provided by Daniel Lindsey of NOAA/NESDIS/STAR/RAMM Branch:

4-6 June 2011:

http://rammb.cira.colostate.edu/templates/loop_directory.asp?data_folder=dev/lindsey/loops/4jun11_chile_ir&image_width=1020&image_height=720&no_toggle=1

12-14 June 2011:

http://rammb.cira.colostate.edu/templates/loop_directory.asp?data_folder=dev/lindsey/loops/13jun11_chile_ir&image_width=1020&image_height=720&no_toggle=1

Geologic Background. The Puyehue-Cordón Caulle volcanic complex (PCCVC) is a large NW-SE-trending late-Pleistocene to Holocene basaltic-to-rhyolitic transverse volcanic chain SE of Lago Ranco. The 1799-m-high Pleistocene Cordillera Nevada caldera lies at the NW end, separated from Puyehue stratovolcano at the SE end by the Cordón Caulle fissure complex. The Pleistocene Mencheca volcano with Holocene flank cones lies NE of Puyehue. The basaltic-to-rhyolitic Puyehue volcano is the most geochemically diverse of the PCCVC. The flat-topped, 2236-m-high volcano was constructed above a 5-km-wide caldera and is capped by a 2.4-km-wide Holocene summit caldera. Lava flows and domes of mostly rhyolitic composition are found on the E flank. Historical eruptions originally attributed to Puyehue, including major eruptions in 1921-22 and 1960, are now known to be from the Cordón Caulle rift zone. The Cordón Caulle geothermal area, occupying a 6 x 13 km wide volcano-tectonic depression, is the largest active geothermal area of the southern Andes volcanic zone.

Information Contacts: Observatorio Volcanológico de Los Andes del Sur-Servicio Nacional de Geología y Minería (OVDAS-SERNAGEOMIN), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Daniel Lindsey, NOAA/NESDIS/STAR/RAMM Branch (URL: http://rammb.cira.colostate.edu/); René Servranckx, Meteorological Service of Canada (URL: http://www.ec.gc.ca/meteo-weather/default.asp?lang=En&n=FDF98F96-1); and Montreal Volcanic Ash Advisory Centre (VAAC) (URL: http://ec.gc.ca/meteo-weather/default.asp?lang=En&n=6B59FE0C-1).

In several issues of the Bulletin (BGVN 35:07, 36:03, and 38:04) we described the first confirmed eruption at Sinabung volcano (figure 1), which began 27 August 2010. This report notes ongoing eruptions along with more evacuations, more pyroclastic flows, and plumes as tall as 10 km.

Figure 5. A map centered on Indonesia, showing the location of Sinabung volcano on Sumatra Island near the NW end of the long line of active volcanoes (black triangles) in that country. Sinabung lies 35 km NNW from the nearest margin of the crater lake of Toba, the largest identified volcanic caldera on Earth. Courtesy of U.S. Geological Survey.

The Indonesian Center of Volcanology and Geological Hazard Mitigation (CVGHM) reported that seismicity at Sinabung fluctuated during 2012 and through September 2013. During early September 2013, dense white plumes rose 100-150 m above the crater, and, on 14 September, incandescence from the crater was observed. Although this and several other instances of incandescence from the volcano's crater were reported during this eruption period, no MODVOLC thermal alerts were measured.

An estimated 16,000 people live within 10 km of the Sinabung volcano. Many photos of the volcano during this eruption can be found in an article from The Atlantic (Taylor, 2013). Some of the photos disclosed plumes otherwise little documented.

According to news articles, an eruption at 0245 on 15 September produced an ash plume and ashfalls in the towns of Sukameriah (50 km NE), Kutarayat (location uncertain), Kutagugung (16 km SW), and Berastagi (14 km E). About 6,000 people were evacuated from areas within a 3-km radius of the volcano, and several flights at Medan's airport (55 km NW) were canceled. CVGHM raised the Alert Level to III.

An eruption at 1203 on 17 September 2013 ejected tephra and a dense ash plume that rose higher than the plume seen on 15 September. According to the Darwin VAAC, on 17 September, a pilot observed an ash plume that rose to an altitude of 6.1 km and drifted 55 km SE. On 18 September a low-level ash plume rose to an altitude of 3 km and drifted SE, dissipating later that day. The VAAC also noted that CVGHM had confirmed that Sinabung was degassing but not emitting any ash. The evacuees started to return home on 22 September.

Seismicity at Sinabung declined but continued to fluctuate through 22 October. White plumes were seen rising 100-300 m from the crater. On 29 September 2013, the Alert Level was lowered to II.

On 22 October grayish plumes rose 250 m. Vents appeared on the N flank and produced dense white plumes that rose 70 m. On 23 October landslides at two locations were observed, and explosions occurred at 1619 and 1651 hours. Plumes rose from the summit crater and from a fracture formed on 15 October near Lau Kawar, a lake at the foot of Sinabung. Fog prevented observations for a period after the explosions; once the fog cleared dense gray plumes were observed. A third explosion occurred at 2100 hours. On 24 October at 0550 and 0612 explosions s generated ash plumes, and at least one rose 3 km and deposited ashfall in areas S. Based on information from the Indonesian Meteorological Office, the Darwin VAAC reported that an eruption at 1737 on 26 October 2013 generated an ash plume that rose to an altitude of 4.9 km. At 0700 and 1200 hours on 27 October a webcam showed an ash plume rising to an altitude of 3.7 km and drifting over 35 km NE.

CVGHM reported elevated seismicity including continuous tremor ongoing since 29 October 2013. Relatively small ash explosions were also reported prior to the larger events on 3 November. During 29 October-2 November plumes rose to 200-2,000 m above the volcano's summit. Gas measurements conducted by CVGHM during 31 October and on 1-2 November showed a sulfur dioxide (SO₂) flux of 226-426 tons per day; this was a general decrease in emissions compared to those measured routinely during the year In addition, remote sensing data suggested the formation of a new vent sometime between 29 October and 2 November 2013 near the NE summit crater.

During 31 October ashfall was noted on the SE flank up to 1 km from the summit. CVGHM reported that explosions occurred on 3 November at 0126 and 1615, both generating ash plumes up to altitudes of 7 km that drifting W. These triggered evacuations from communities within 3 km of the volcano (~1,681 residents). Rumbling sounds that lasted up to 10 min were noted by staff at the Sinabung Observation Post (~8.5 km from the volcano). News agencies reported that this was the second largest eruption since the 24 October event that displaced more than 3,300 people. The Alert Level was increased from Level II (Watch) to Level III (Alert) at 0300 on the 31st.

Another eruption was reported by CVGHM at 1423 hours on 5 November 2013. This event lasted for 20 minutes and generated an ash plume up to 3,000 m above the crater that drifted SW. Pyroclastic flows were observed at 1431 hours on 5 November that extended 1 km down the SE flank. No casualties were reported.

Based on information from the Jakarta Meteorological Watch Office, webcam data, wind data, and satellite images, the Darwin VAAC reported that on 6 November 2013 an ash plume from Sinabung rose to an altitude of 3 km (figure 2). In addition, a glowing spot was seen near Sinabung's summit.

Figure 6. Sinabung erupts and emits a pyroclastic flow on 6 November 2013. Glowing material appears just below the summit. Hundreds of residents were evacuated to safer areas as the volcano erupted anew following the earlier September 2013 eruptions. Courtesy of Atar/AFP/Getty Images; appeared in Taylor (2013).

The next day an ash plume rose to the same altitude but was not observed in satellite images because of meteorological cloud cover. Webcam images showed an eruption on 8 November that produced a low-level ash plume. The Jakarta Meteorological Watch Office, the webcam, and satellite data detecting SO₂ indicated two explosions on 10 November. The first one, at 0720, generated an ash plume that rose to an altitude of 3.7 km. The altitude of the second plume, from an explosion at 1600, was unknown.

An ash plume on 11 November rose to an altitude of 3 km and drifted less than 20 km SW (figure 3). The next day an ash plume rose to an altitude of 3.7 km and drifted almost 40 km NW.

Figure 7. A press photo taken at Sinabung on 11 November 2013. A larger pyroclastic flow seems poised to descend from the summit area behind two smaller, adjacent pyroclastic flows. A narrow columnar cloud hangs over the summit. Courtesy of AP Photo/Dedy Zulkifli; appeared in Taylor (2013).

Based on webcam data and satellite images, the Darwin VAAC reported that during 13-14 November an ash plume from Sinabung rose to an altitude of 3.7 km and drifted almost 150 km NW and W. A pyroclastic flow traveled 1.2 km down the SE flank on 14 November, prompting more evacuations from villages near the base of the volcano.

An explosion observed with the webcam on 18 November 2013 produced an ash plume that rose to an altitude of 7.6 km. About 30 minutes later an ash plume also visible in satellite images rose to an altitude of 11.3 km and drifted 65 km W. Four hours later satellite images showed fresh ash plumes at an altitude of 9.1 km to the W of Sinabung and at an altitude of 4.6 km over the crater. On 19 November the webcam recorded an ash plume that rose to an altitude of 4.6 km over the crater. A news article stated that later that night that an ash plume rose to an altitude of 10 km.

A news article from 20 November noted that volcanologists updated the previous hazard map for Sinabung (see figure in BGVN 35:07). The second-tier disaster-prone area, previously defined as a radius of 2-3 km from Sinabung's crater, was expanded to 4-5 km.

CVGHM reported three explosions from Sinabung on 17 November 2013. The first explosion, at 2024, generated an ash plume that rose 500 m and drifted SW, and a pyroclastic flow that traveled 500 m down the SE flank.

At 2152 hours that day a dense ash plume from an explosion rose 500 m and drifted SW. Incandescent material was ejected 50 m away from the crater. At 2252 an ash plume rose 1 km and drifted SW. At 0704 on 18 November an explosion generated an ash plume that rose 8 km and drifted SW. A pyroclastic flow also traveled 800 m down the SE flank.

On 19 November at 2155 a dense ash plume rose 10 km, drifted SW, and exhibited lightning. Pyroclastic flows again traveled 500 m SE. Multiple explosions on 20 November (at 0240, 0405, 0529, 0619, and 0641) generated ash plumes that rose to heights between 1 and 3.5 km. An explosion at 1716 was detected by the seismic network but cloud cover prevented observations of possible plumes. White plumes rose 100 m on 21 and 23 November, but misty conditions prevented visual observations on 22 November. On 23 November scoria fell in the Sigarang-garang and Desa Kuta villages in the NNE. Two explosions on 24 November, at 0043 and 0232 hours, were detected but not visually observed. Ash plumes rose 8 km and drifted NNE at 0727, rose 1 km at 0812, and rose 3 km at 0855. Since Sinabung's activity continued to increase, CVGHM raised the Alert Level to IV on 24 November. CVGHM noted that residents and tourists were advised not to approach the crater within a 5-km radius. Remaining residents in 17 villages around the volcano were to be evacuated.

News reported that on the morning of 25 November 2013 six new eruptive events sent "lava and searing gas" up to 1.5 km down the slopes, causing villagers to evacuate; this description apparently refers to pyroclastic flows. Volcanic material erupted as high as 2 km above the crater. The Indonesian National Agency for Disaster Management (BNPB) reported that 17,713 people, out of the 20,270 residents had been evacuated to 31 shelters.

Based on webcam data and wind data, the Darwin VAAC reported that during 28-31 November and 2 December ash plumes from Sinabung rose to altitudes of 3-5.5 km. Ash plumes drifted 150 km W during 30-31 November and 55 km W on 2 December. On 3 December ash plumes rose to an altitude of 8.2 km and drifted W. According to a news report on 2 December, landslides triggered by torrential rain buried houses and killed nine people in Gundaling village, 12 km E. On 4 December an ash plume from Sinabung rose to an altitude of 8.2 km and drifted N. Later that day and during 5-6 December ash plumes rose to altitudes of 3-3.7 km and drifted NW. CVGHM reported that observers in Ndokum Siroga, about 8.5 km away from the volcano, noted gray plumes rising 1 km above Sinabung on 6 December. They also saw grayish-white and dense white plumes as high as 400 m on 7 and 8 December, respectively. Dense grayish-to-white plumes rose 70-200 m on 9 December. White plumes rose 100-150 m above the crater during 10-13 December. Tremor during 6-13 December was recorded continuously, with varying amplitude. The number of low-frequency earthquakes significantly increased on 7 December, and the number of hybrid earthquakes increased the next day. RSAM (real-time seismic amplitude measurement) values of energy steadily increased since 28 November. The Alert Level remained at IV.

In conclusion, seismicity and images of ash plumes and pyroclastic flows suggest that the current eruption of Sinabung volcano began around 14-15 September 2013 and has continued through at least 11 December 2013.

Reference: Taylor, A., 18 November 2013, In Focus: The Eruptions of Mount Sinabung, The Atlantic (URL: http://www.theatlantic.com/infocus/2013/11/the-eruptions-of-mount-sinabung/100630/).

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

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM) (also known as Pusat Vulkanologi dan Mitigasi Bencana Geologi-PVMBG), National Agency for Disaster Management (Badan Nacional Penanggulangan Bencana-BNPB), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://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/); CBC.CA News, Toronto, Canada (URL: http://www.cbc.ca/); The Atlantic (URL: http://www.theatlantic.com); ReliefWeb (a specialized digital service of the United Nations Office for the Coordination of Humanitarian Affairs-OCHA) (URL: reliefweb.int); and Volcano Discovery (URL: http://www.volcanodiscovery.com).

Based on analyses of satellite images as reported by the Global Disaster Alert and Coordination System (GDACS) and the Darwin Volcanic Ash Advisory Centre (VAAC), five volcano plume advisories were issued for Pago volcano in the Summer of 2012 (table 1).

Table 1.Five VAAC volcano ash advisories were issued for Pago volcano for the period May-July 2012. Darwin VAAC Aviation Alert Colors range in four steps from green to yellow to orange to red - lowest to highest alert. Courtesy of Darwin VAAC and GDACS.

According to the Papua New Guinea (PNG) National Disaster Centre (2013), PNG has 16 active and at least 28 potentially active or 'dormant' volcanoes which are a potential danger to the lives of about a quarter of a million people living in a total area of 16, 000 km2. Of the 16 active volcanoes, 6 of them are classified as high-risk volcanoes - high-risk in the sense that they have had explosive eruptions in the past and have the potential of repeating these eruptions in future. Of these 6 high-risk volcanoes, 3 are in New Britain - Rabaul in East New Britain, and Ulawun and Pago in West New Britain (for locations, see figure 3, BGVN 32:04, on Sulu Range volcano).

Figure 20 shows a satellite photo of approximately 8-km diameter Witori caldera from Google Earth. The walls of the caldera appear on the N and NW side of the caldera. A series of lava flows have formed the lobate character of the floor of the caldera. More detail on the lava flows appear in a previous report on Pago (figure 3, BGVN 27:08 - a vertical photo, with the old caldera rim delineated in white, distribution of new lava flows from August 2002 shown in red, compared with the previous lava flows from the 1911-18 eruption shown in light blue; a fault perpendicular to the 2002 lava flow is shown in dark blue).

Figure 20. Satellite photo of Witori caldera within which Pago volcano exists. Courtesy of Google Earth.

References. Volcano Research Center, 2002 (4 September), Pago volcano, New Britain, Papua, New Guinea: Brief report and Photographs Aug. 26-September 2, 2002; URL:http://hakone.eri.u-tokyo.ac.jp.

Papua New Guinea (PNG) National Disaster Centre (NDC), 2013 (28 July), Volcanic eruption, PGN NDC (URL:http://www.pngndc.gov.pg/).

Geologic Background. The 5.5 x 7.5 km Witori caldera on the northern coast of central New Britain contains the young historically active cone of Pago. The Buru caldera cuts the SW flank of Witori volcano. The gently sloping outer flanks of Witori volcano consist primarily of dacitic pyroclastic-flow and airfall deposits produced during a series of five major explosive eruptions from about 5600 to 1200 years ago, many of which may have been associated with caldera formation. The post-caldera Pago cone may have formed less than 350 years ago. Pago has grown to a height above that of the Witori caldera rim, and a series of ten dacitic lava flows from it covers much of the caldera floor. The youngest of these was erupted during 2002-2003 from vents extending from the summit nearly to the NW caldera wall.

Information Contacts: Ima Itikarai and Herman Patia, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Global Disaster Alert and Coordination System (GDACS), United Nations and the European Commission (URL: http://www.gdacs.org/Volcanoes); Volcano Research Center, Earthquake Research Institute, University of Tokyo, 113-0032 1-1-1, Yayoi, Bunkyo-ku, Tokyo (URL: http://hakone.eri.u-tokyo.ac.jp); and Papua New Guinea (PNG) National Disaster Centre (URL: http://www.pngndc.gov.pg/).