Bagana volcano is found in a remote portion of central Bougainville Island in Papua New Guinea. The most recent eruptive phase that began in early 2000 has produced ash plumes and thermal anomalies (BGVN 44:06, 50:01). Activity has remained low between January-July 2019 with rare thermal anomalies and occasional steam plumes. This reporting period updates information for June-November 2019 and includes thermal anomalies and intermittent gas-and-steam emissions. Thermal data and satellite imagery are the primary sources of information for this report.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed an increased number of thermal anomalies within 5 km from the summit beginning in late July-early August (figure 38). Two Sentinel-2 thermal satellite images showed faint, roughly linear thermal anomalies, indicative of lava flows trending EW and NS on 7 July 2019 and 6 August, respectively (figure 39). Weak thermal hotspots were briefly detected in late September-early October after a short hiatus in September. No thermal anomalies were recorded in Sentinel-2 past August due to cloud cover; however, gas-and-steam emissions were visible on 7 July and in September (figures 39, 40, and 41).

Figure 38. Thermal anomalies near the crater summit at Bagana during February-November 2019 as recorded by the MIROVA system (Log Radiative Power) increased in frequency and power in early August. A small cluster was detected in early October after a brief pause in activity in early September. Courtesy of MIROVA.

Figure 39. Sentinel-2 thermal satellite imagery showing small thermal anomalies at Bagana between July-August 2019. Left: A very faint thermal anomaly and a gas-and-steam plume is seen on 7 July 2019. Right: Two small thermal anomalies are faintly seen on 6 August 2019. Both Sentinel-2 satellite images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Figure 40. A gas-and-steam plume rising from the summit of Bagana on 18 September 2019. Courtesy of Brendan McCormick Kilbride (University of Manchester).

The Deep Carbon Observatory (DCO) scientific team partnered with the Rabaul Volcano Observatory and the Bougainville Disaster Office to observe activity at Bagana and collect gas data using drone technology during two weeks of field work in mid-September 2019. For this field work, the major focus was to understand the composition of the volcanic gas emitted at Bagana and measure the concentration of these gases. Since Bagana is remote and difficult to climb, research about its gas emissions has been limited. The recent advancements in drone technology has allowed for new data collection at the summit of Bagana (figure 41). Most of the emissions consisted of water vapor, according to Brendan McCormick Kilbride, one of the volcanologists on this trip. During 14-19 September there was consistently a strong gas-and-steam plume from Bagana (figure 42).

Figure 41. Degassing plumes seen from drone footage 100 m above the summit of Bagana. Top: Zoomed out view of the summit of Bagana degassing. Bottom: Closer perspective of the gases emitted from Bagana. Courtesy of Kieran Wood (University of Bristol) and the Bristol Flight Laboratory.

Figure 42. Photos of gas-and-steam plumes rising from Bagana between 14-19 September 2019. Courtesy of Brendan McCormick Kilbride (University of Manchester).

Geologic Background. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Brendan McCormick Kilbride, University of Manchester, Manchester M13 9PL, United Kingdom (URL: https://www.research.manchester.ac.uk/portal/brendan.mccormickkilbride.html, Twitter: https://twitter.com/BrendanVolc); Kieran Wood, University of Bristol, Bristol BS8 1QU, United Kingdom (URL: http://www.bristol.ac.uk/engineering/people/kieran-t-wood/index.html, Twitter: https://twitter.com/DrKieranWood, video posted at https://www.youtube.com/watch?v=A7Hx645v0eU); University of Bristol Flight Laboratory, Bristol BS8 1QU, United Kingdom (Twitter: https://twitter.com/UOBFlightLab).

Kerinci, located in Sumatra, Indonesia, is a highly active volcano characterized by explosive eruptions with ash plumes and gas-and-steam emissions. The most recent eruptive episode began in April 2018 and included intermittent explosions with ash plumes. Volcanism continued from June-November 2019 with ongoing intermittent gas-and-steam and ash plumes. The primary source of information for this report comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), the Darwin Volcanic Ash Advisory Centre (VAAC), and MAGMA Indonesia.

Brown- to gray-colored ash clouds drifting in different directions were reported by PVMBG, the Darwin VAAC, and MAGMA Indonesia between June and early November 2019. Ground observations, satellite imagery, and weather models were used to monitor the plume, which ranged from 4.3 to 4.9 km altitude, or about 500-1,100 m above the summit. On 7 June 2019 at 0604 a gray ash emission rose 800 m above the summit, drifting E, according to a ground observer. An ash plume on 12 July rose to 4 km altitude and drifted SW, as determined by satellite imagery and weather models. An eruption produced a gray ash cloud on 31 July that rose to 4.6 km altitude and drifted NE and E, according to PVMBG and the Darwin VAAC (figure 17). Another ash cloud rose up to 4.3 km altitude on 3 August. On 2 September a possible ash plume rose to a maximum altitude of 4.9 km and drifted WSW, according to the Darwin VAAC advisory.

Figure 17. A gray ash plume at Kerinci rose roughly 800 m above the summit on 31 July 2019 and drifted NE and E. Courtesy of MAGMA Indonesia.

Brown ash emissions rose to 4.4 km altitude at 1253 on 6 October, drifting WSW. Similar plumes reached 4.6 km altitude twice on 30 October and moved NE, SE, and E at 0614 and WSW at 1721, based on ground observations. On 1-2 November, ground observers saw brown ash emissions rising up to 4.3 km drifting ESE. Between 3 and 5 November the brown ash plumes rose 100-500 m above the summit, according to PVMBG.

Gas emissions continued to be observed through November, as reported by PVMBG and identified in satellite imagery (figure 18). Seismicity that included volcanic earthquakes also continued between June and early November, when the frequency decreased.

Figure 18. Sentinel-2 thermal satellite imagery showing a typical white gas-and-steam plume at Kerinci on 9 August 2019. Sentinel-2 satellite image with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Geologic Background. Gunung Kerinci in central Sumatra forms Indonesia's highest volcano and is one of the most active in Sumatra. It is capped by an unvegetated young summit cone that was constructed NE of an older crater remnant. There is a deep 600-m-wide summit crater often partially filled by a small crater lake that lies on the NE crater floor, opposite the SW-rim summit. The massive 13 x 25 km wide volcano towers 2400-3300 m above surrounding plains and is elongated in a N-S direction. Frequently active, Kerinci has been the source of numerous moderate explosive eruptions since its first recorded eruption in 1838.

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/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

The long-term activity at Bezymianny has been dominated by almost continuous thermal anomalies, moderate gas-steam emissions, dome growth, lava flows, and an occasional ash explosion (BGVN 44:06). The volcano is monitored by the Kamchatka Volcanic Eruptions Response Team (KVERT. Throughout the reporting period of June to November 2019, the Aviation Colour Code remained Yellow (second lowest of four levels).

According to KVERT weekly reports, lava dome growth continued in June through mid-July 2019. Thereafter the reports did not mention dome growth, but indicated that moderate gas-and-steam emissions (figure 32) continued through November. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, based on analysis of MODIS data, detected hotspots within 5 km of the summit almost every day. KVERT also reported a thermal anomaly over the volcano almost daily, except when it was obscured by clouds. Infrared satellite imagery often showed thermal anomalies generated by lava flows or dome growth (figure 33).

Figure 32. Photo of Bezymianny showing fumarolic activity on 4 July 2019. Photo by O. Girina (IVS FEB RAS, KVERT); courtesy of KVERT.

Figure 33. Typical infrared satellite images of Bezymianny showing thermal anomalies in the summit crater, including a lava flow to the WNW. Top: 21 August 2019 with SWIR filter (bands 12, 8A, 4). Bottom: 17 September 2019 with Atmospheric Penetration filter (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Geologic Background. Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); 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).

Mayon, located in the Philippines, is a highly active stratovolcano with recorded historical eruptions dating back to 1616. The most recent eruptive episode began in early January 2018 that consisted of phreatic explosions, steam-and-ash plumes, lava fountaining, and pyroclastic flows (BGVN 43:04). The previous report noted small but distinct thermal anomalies, gas-and-steam plumes, and slight inflation (BGVN 44:05) that continued to occur from May into mid-October 2019. This report includes information based on daily bulletins from the Philippine Institute of Volcanology and Seismology (PHIVOLCS) and Sentinel-2 satellite imagery.

Between May and October 2019, white gas-and-steam plumes rose to a maximum altitude of 800 m on 17 May. PHIVOLCS reported that faint summit incandescence was frequently observed at night from May-July and Sentinel-2 thermal satellite imagery showed weaker thermal anomalies in September and October (figure 49); the last anomaly was identified on 12 October. Average SO₂ emissions as measured by PHIVOLCS generally varied between 469-774 tons/day; the high value of the period was on 25 July, with 1,171 tons/day. Small SO₂ plumes were detected by the TROPOMI satellite instrument a few times during May-September 2019 (figure 50).

Figure 49. Sentinel-2 thermal satellite imagery of Mayon between May-October 2019. Small thermal anomalies were recorded in satellite imagery from the summit and some white gas-and-steam plumes are visible. Top left: 30 May 2019. Top right: 9 June 2019. Bottom left: 22 September 2019. Bottom right: 12 October 2019. Sentinel-2 satellite images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

Figure 50. Small SO2 plumes rising from Mayon during May-September 2019 recorded in DU (Dobson Units). Top left: 28 May 2019. Top right: 26 July 2019. Bottom left: 16 August 2019. Bottom right: 23 September 2019. Courtesy of NASA Goddard Space Flight Center.

Continuous GPS data has shown slight inflation since June 2018, corroborated by precise leveling data taken on 9-17 April, 16-25 July, and 23-30 October 2019. Elevated seismicity and occasional rockfall events were detected by the seismic monitoring network from PHIVOLCS from May to July; recorded activity decreased in August. Activity reported by PHIVOLCS in September-October 2019 consisted of frequent gas-and-steam emissions, two volcanic earthquakes, and no summit incandescence.

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), Department of Science and Technology, University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); 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/).

Merapi is an active volcano north of the city of Yogyakarta (figure 79) that has a recent history of dome growth and collapse, resulting in block-and-ash flows that killed over 400 in 2010, while an estimated 10,000-20,000 lives were saved by evacuations. The edifice contains an active dome at the summit, above the Gendol drainage down the SE flank (figure 80). The current eruption episode began in May 2018 and dome growth was observed from 11 August 2018-onwards. This Bulletin summarizes activity during April through September 2019 and is based on information from Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG, the Center for Research and Development of Geological Disaster Technology, a branch of PVMBG), Sutopo of Badan Nasional Penanggulangan Bencana (BNPB), MAGMA Indonesia, along with observations by Øystein Lund Andersen and Brett Carr of the Lamont-Doherty Earth Observatory.

Figure 79. Merapi volcano is located north of Yogyakarta in Central Java. Photo courtesy of Øystein Lund Andersen.

Figure 80. A view of the Gendol drainage where avalanches and block-and-ash flows are channeled from the active Merapi lava dome. The Gendol drainage is approximately 400 m wide at the summit. Courtesy of Brett Carr, Lamont-Doherty Earth Observatory.

At the beginning of April the rate of dome growth was relatively low, with little morphological change since January, but the overall activity of Merapi was considered high. Magma extrusion above the upper Gendol drainage resulted in rockfalls and block-and-ash flows out to 1.5 km from the dome, which were incandescent and visible at night. Five block-and-ash flows were recorded on 24 April, reaching as far as 1.2 km down the Gendol drainage. The volume of the dome was calculated to be 466,000 m3 on 9 April, a slight decrease from the previous week. Weak gas plumes reached a maximum of 500 m above the dome throughout April.

Six block-and-ash flows were generated on 5 May, lasting up to 77 seconds. Throughout May there were no significant changes to the dome morphology but the volume had decreased to 458,000 by 4 May according to drome imagery analysis. Lava extrusion continued above the Gendol drainage, producing rockfalls and small block-and-ash flows out to 1.2 km (figure 81). Gas plumes were observed to reach 400 m above the top of the crater.

Figure 81. An avalanche from the Merapi summit dome on 17 May 2019. The incandescent blocks traveled down to 850 m away from the dome. Courtesy of Sutopo, BNPB.

There were a total of 72 avalanches and block-and-ash flows from 29 January to 1 June, with an average distance of 1 km and a maximum of 2 km down the Gendol drainage. Photographs taken by Øystein Lund Andersen show the morphological change to the lava dome due to the collapse of rock and extruding lava down the Gendol drainage (figures 82 and 83). Block-and-ash flows were recorded on 17 and 20 June to a distance of 1.2 km, and a webcam image showed an incandescent flow on 26 June (figure 84). Throughout June gas plumes reached a maximum of 250 m above the top of the crater

Figure 82. The development of the Merapi summit dome from 2 June 2018 to 17 June 2019. Courtesy of Øystein Lund Andersen.

Figure 83. Photos taken of the Merapi summit lava dome in June 2019. Top: This nighttime time-lapse photograph shows incandescence at the south-facing side of the dome on the 16 June. Middle: A closeup of a small rockfall from the dome on 17 June. Bottom: A gas plume accompanying a small rockfall on 17 June. Courtesy of Øystein Lund Andersen.

Figure 84. Blocks from an incandescent rockfall off the Merapi dome reached out to 1 km down the Gendol drainage on 26 June 2019. Courtesy of MAGMA Indonesia.

Analysis of drone images taken on 4 July gave an updated dome volume of 475,000 m3, a slight increase but with little change in the morphology (figure 85). Block-and-ash flows traveled 1.1 km down the Gendol drainage on 1 July, 1 km on the 13th, and 1.1 km on the 14th, some of which were seen at night as incandescent blocks fell from the dome (figure 86). During the week of 19-25 July there were four recorded block-and-ash flows reaching 1.1 km, and flows traveled out to around 1 km on the 24th, 27th, and 31st. The morphology of the dome continued to be relatively stable due to the extruding lava falling into the Gendol drainage. Gas plumes reached 300 m above the top of the crater during July.

Figure 85. The Merapi dome on 30 July 2019 producing a weak plume. Courtesy of MAGMA Indonesia.

Figure 86. Incandescent rocks from the hot lava dome at the summit of Merapi form rockfalls down the Gendol drainage on 14 July 2019. Courtesy of Øystein Lund Andersen.

During the week of 5-11 August the dome volume was calculated to be 461,000 m3, a slight decrease from the week before with little morphological changes due to the continued lava extrusion collapsing into the Gendol drainage. There were five block-and-ash flows reaching a maximum of 1.2 km during 2-8 August. Two flows were observed on the 13th and 14th reaching 950 m, out to 1.9 km on the 20th and 22nd, and to 550 m on the 24th. There were 16 observed flows that reached 500-1,000 m on 25-27 August, with an additional flow out to 2 km at 1807 on the 27th (figure 87). Gas plumes reached a maximum of 350 m through the month.

Figure 87. An incandescent rockfall from the Merapi dome that reached 2 km down the Gendol drainage on 27 August 2019. Courtesy of BPPTKG.

Brett Carr was conducting field work at Merapi during 12-26 September. During this time the lava extrusion was low (below 1 m3 per second). He observed small rockfalls with blocks a couple of meters in size, traveling about 50-200 m down the drainage every hour or so, producing small plumes as they descended and resulting in incandescence on the dome at night. Small dome collapse events produced block-and-ash flows down the drainage once or twice per day (figure 88) and slightly larger flows just over 1 km long a couple of times per week.

Figure 88. A rockfall on the Merapi dome, towards the Gendol drainage at 0551 on 20 September 2019. Courtesy of Brett Carr, Lamont-Doherty Earth Observatory.

The dome volume was 468,000 m3 by 19 September, a slight increase from the previous calculation but again with little morphological change. Two block-and-ash flows were observed out to 600 m on 9 September and seven occurred on the 9th out to 500-1,100 m. Two occurred on the 14th down to 750-900 m, three occurred on 17, 20, and 21 September to a maximum distance of 1.2 km, and three more out to 1.5 km through the 26th. A VONA (Volcano Observatory Notice for Aviation) was issued on the 22nd due to a small explosion producing an ash plume up to approximately 3.8 km altitude (about 800 m above the summit) and minor ashfall to 15 km SW. This was followed by a block-and-ash flow reaching as far as 1.2 km and lasting for 125 seconds (figure 89). Preceding the explosion there was an increase in temperature at several locations on the dome. Weak gas plumes were observed up to 100 m above the crater throughout the month.

Figure 89. An explosion at Merapi on 22 September 2019 was followed by a block-and-ash flow that reached 1.2 km down the Gendol drainage. Courtesy of BPPTKG.

Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 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/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.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); Øystein Lund Andersen? (Twitter: @OysteinLAnderse, URL: http://www.oysteinlundandersen.com); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN); Brett Carr, Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY, USA (URL: https://www.ldeo.columbia.edu/user/bcarr).

Manam is a frequently active volcano forming an island approximately 10 km wide, located 13 km north of the main island of Papua New Guinea. At the summit are the Main Crater and South Crater, with four valleys down the NE, SE, SW, and NW flanks (figure 57). Recent activity has occurred at both summit craters and has included gas and ash plumes, lava flows, and pyroclastic flows. Activity in December 2018 prompted the evacuation of nearby villages and the last reported activity for 2018 was ashfall on 8 December. Activity from January through September 2019 summarized below is based on information from the Rabaul Volcano Observatory (RVO), the Darwin Volcanic Ash Advisory Center (VAAC), the University of Hawai'i's MODVOLC thermal alert system, Sentinel-5P/TROPOMI and NASA Aqua/AIRS SO₂ data, MIROVA thermal data, Sentinel-2 satellite images, and observations by visiting scientists. A significant eruption in June resulted in evacuations, airport closure, and damage to local crops and infrastructure.

Figure 57. A PlanetScope image of Manam showing the two active craters with a plume emanating from the South Crater and the four valleys at the summit on 29 August 2019. Image copyright 2019 Planet Labs, Inc.

Activity during January-May 2019. Several explosive eruptions occurred during January 2019 according to Darwin VAAC reports, including an ash plume that rose to around 15 km and dispersed to the W on the 7th. RVO reported that an increase in seismic activity triggered the warning system shortly before the eruption commenced (figure 58). Small explosions were observed through to the next day with ongoing activity from the Main Crater and a lava flow in the NE valley observed from around 0400. Intermittent explosions ejected scoria after 0600, depositing ejecta up to 2 cm in diameter in two villages on the SE side of the island. Incandescence at both summit craters and hot deposits at the terminus of the NE valley are visible in Sentinel-2 TIR data acquired on the 10th (figure 59).

Figure 58. Real-Time Seismic-Amplitude Measurement graph representing seismicity at Manam over 7-9 January 2019, showing the increase during the 7-8 January event. Courtesy of RVO.

Figure 59. Sentinel-2 thermal infrared (TIR) imagery shows incandescence in the two Manam summit craters and at the terminus of the NE valley near the shoreline on 10 January 2019. Courtesy of Sentinel-Hub Playground.

Another explosion generated an ash plume to around 15 km on the 11th that dispersed to the SW. An explosive eruption occurred around 4 pm on the 23rd with the Darwin VAAC reporting an ash plume to around 16.5 km altitude, dispersing to the E. Activity continued into the following day, with satellites detecting SO₂ plumes on both 23 and 24 January (figure 60). Activity declined by February with one ash plume reported up to 4.9 km altitude on 15 February.

Figure 60. SO2 plumes originating from Manam detected by NASA Aqua/AIRS (top) on 23 January 2019 and by Sentinel-5P/TROPOMI on 24 January (bottom). Images courtesy of Simon Carn, Michigan Technological University.

Ash plumes rose up to 3 km between 1 and 5 March, and dispersed to the SE, ESE, and E. During 5-6 March the plumes moved E, and the events were accompanied by elevated seismicity and significant thermal anomalies detected in satellite data. During 19-22 March explosions produced ash plumes up to 4.6 km altitude, which dispersed to the E and SE. Simon Carn of the Michigan Technological University noted a plume in Aqua/AIRS data at around 15 km altitude at 0400 UTC on 23 January with approximately 13 kt measured, similar to other recent eruptions. Additional ash plumes were detected on 29 March, reaching 2.4-3 km and drifting to the E, NE, and N. Multiple SO₂ plumes were detected throughout April (figure 61).

Figure 61. Examples of elevated SO2 (sulfur dioxide) emissions from Manam during April 2019, on 9 April (top left), 21 April (top right), 22 April (bottom left), 28 April (bottom right). Courtesy of the NASA Space Goddard Flight Center.

During 19-28 May the Deep Carbon Observatory ABOVE (Aerial-based Observations of Volcanic Emissions) scientific team observed activity at Manam and collected gas data using drone technology. They recorded degassing from the South Crater and Main Crater (figure 63 and 64), which was also detected in Sentinel-5P/TROPOMI data (figure 65). Later in the day the plumes rose vertically up to 3-4 km above sea level and appeared stronger due to condensation. Incandescence was observed each night at the South Crater (figure 66). The Darwin VAAC reported an ash plume on 10 May, reaching 5.5 km altitude and drifting to the NE. Smaller plumes up to 2.4 km were noted on the 11th.

Figure 62. Degassing plumes from the South Crater of Manam, seen from Baliau village on the northern coast on 24 May 2019. Courtesy of Emma Liu, University College London.

Figure 63. A strong gas-and-steam plume from Manam was observed moving tens of kilometers downwind on 19 May 2019, viewed here form the SSW at dusk. Photo courtesy of Julian Rüdiger, Johannes Gutenberg University Mainz.

Figure 64. Sentinel-5P/TROPOMI SO2 data acquired on 22 May 2019 during the field observations of the Deep Carbon Observatory ABOVE team. Image courtesy of Simon Carn, Michigan Technological University.

Figure 65. Incandescence at the South Crater of Manam was visible during 19-21 May 2019 from the Baliau village on the northern coast of the island. Photos courtesy of Tobias Fischer, University of New Mexico (top) and Matthew Wordell (bottom).

Activity during June 2019. Ash plumes rose to 4.3 km and drifted SW on 7-8 June, and up to 3-3.7 km and towards the E and NE on 18 June. Sentinel-2 thermal satellite data show hot material around the Main Crater on 24 June (figure 66). On 27 June RVO reported that RSAM (Real-time Seismic Amplitude Measurement, a measure of seismic activity through time) increased from 540 to over 1,400 in 30 minutes. "Thundering noise" was noted by locals at around 0100 on the 28th. An ash plume drifting SW was visible in satellite images acquired after 0620, coinciding with reported sightings by nearby residents (figure 67). The Darwin VAAC noted that by 0910 the ash plume had reached 15.2 km altitude and was drifting SW. When seen in satellite imagery at 1700 that day the large ash plume had detached and remained visible extending SW. There were 267 lightning strokes detected within 75 km during the event (figure 68) and pyroclastic flows were generated down the NE and W flanks. At 0745 on 29 June an ash plume reached up to 4.8 km.

Villages including Dugulava, Yassa, Budua, Madauri, Waia, Dangale, and Bokure were impacted by ashfall and approximately 3,775 people had evacuated to care centers. Homes and crops were reportedly damaged due to falling ash and scoria. Flights through Madang airport were also disrupted due to the ash until they resumed on the 30th. The Office of the Resident Coordinator in Papua New Guinea reported that as many as 455 homes and gardens were destroyed. Humanitarian resources were strained due to another significant eruption at nearby Ulawun that began on 26 June.

Figure 66. Sentinel-2 thermal satellite data show hot material around the Main Crater and a plume dispersing SE through light cloud cover on 24 June 2019. Courtesy of Sentinel Hub Playground.

Figure 67. Himawari-8 satellite image showing the ash plume rising above Manam and drifting SW at 0840 on 28 June. Satellite image courtesy of NCIT ScienceCloud.

Figure 68. There were 267 lightning strokes detected within 75 km of Manam between 0729 on 27 June and 0100 on 29 June 2019. Sixty of these occurred within the final two hours of this observation period, reflecting increased activity. Red dots are cloud to ground lightning strokes and black dots are in-cloud strokes. Courtesy of Chris Vagasky, Vaisala Inc.

Activity during July-September 2019. Activity was reduced through July and September. The Darwin VAAC reported an ash plume to approximately 6 km altitude on 6 July that drifted W and NW, another plume that day to 3.7 km that drifted N, and a plume on the 21st that rose to 4.3 km and drifted SW and W. Diffuse plumes rose to 2.4-2.7 km and drifted towards the W on 29 September. Thermal anomalies in the South Crater persisted through September.

Fresh deposits from recent events are visible in satellite deposits, notably in the NE after the January activity (figure 69). Satellite TIR data reflected elevated activity with increased energy detected in March and June-July in MODVOLC and MIROVA data (figure 70).

Figure 69. Sentinel-2 thermal infrared images acquired on 12 October 2018, 20 May 2019, and 12 September 2019 show the eruption deposits that accumulated during this time. A thermal anomaly is visible in the South Crater in the May and September images. Courtesy of Sentinel Hub Playground.

Figure 70. MIROVA log radiative power plot of MODIS thermal infrared at Manam during February through September 2019. Increases in activity were detected in March and June-July. Courtesy of MIROVA.

Geologic Background. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; 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); 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/); Office of the Resident Coordinator, United Nations, Port Moresby, National Capital District, Papua New Guinea (URL: https://papuanewguinea.un.org/en/about/about-the-resident-coordinator-office, https://reliefweb.int/report/papua-new-guinea/papua-new-guinea-volcanic-activity-office-resident-coordinator-flash-2); Himawari-8 Real-time Web, developed by the NICT Science Cloud project in NICT (National Institute of Information and Communications Technology), Japan, in collaboration with JMA (Japan Meteorological Agency) and CEReS (Center of Environmental Remote Sensing, Chiba University) (URL: https://himawari8.nict.go.jp/); Simon Carn, Geological and Mining Engineering and Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, USA (URL: http://www.volcarno.com/, Twitter: @simoncarn); Chris Vagasky, Vaisala Inc., Louisville, Colorado, USA (URL: https://www.vaisala.com/en?type=1, Twitter: @COweatherman, URL: https://twitter.com/COweatherman); Emma Liu, University College London Earth Sciences, London WC1E 6BS (URL: https://www.ucl.ac.uk/earth-sciences/people/academic/dr-emma-liu); Matthew Wordell, Boise, ID, USA (URL: https://www.matthhew.com/biocontact); Julian Rüdiger, Johannes Gutenberg University Mainz, Saarstr. 21, 55122 Mainz, Germany (URL: https://www.uni-mainz.de/).

Tangkuban is located in the West Bandung and Subang Regencies in the West Java Province and has two main summit craters, Ratu and Upas (figure 3). Recent activity has largely consisted of phreatic explosions and gas-and-steam plumes at the Ratu crater. Prior to July 2019, the most recent activity occurred in 2012-2013, ending with a phreatic eruption on 5 October 2013 (BGVN 40:04). Background activity includes geothermal activity in the Ratu crater consisting of gas and steam emission (figure 4). This area is a tourist destination with infrastructure, and often people, overlooking the active crater. This report summarizes activity during 2014 through September 2019 and is based on official agency reports. Monitoring is the responsibility of Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM).

Figure 3. Map of Tangkuban Parahu showing the Sunda Caldera rim and the Ratu, Upas, and Domas craters. Basemap is the August 2019 mosaic, copyright 2019 Planet Labs, Inc.

Figure 4. Background activity at the Ratu crater of Tangkuban Parahu is shown in these images from 1 May 2012. The top image is an overview of the crater and the bottom four images show typical geothermal activity. Copyrighted photos by Øystein Lund Andersen, used with permission.

The first reported activity in 2014 consisted of gas-and-steam plumes during October-December, prompting PVMBG to increase the alert level from I to II on 31 December 2014. These white plumes reached a maximum of 50 m above the Ratu crater (figure 5) and were accompanied by elevated seismicity and deformation. This prompted the implementation of an exclusion zone with a radius of 1.5 km around the crater. The activity decreased and the alert level was lowered back to I on 8 January 2015. There was no further reported activity from January 2015 through mid-2019.

Figure 5. Changes at the Ratu crater of Tangkuban Parahu during 25 December 2014 to 8 January 2015. Rain water accumulated in the crater in December and intermittent gas-and-steam plumes were observed. Courtesy of PVMBG (8 January 2015 report).

From 27 June 2019 an increase in activity was recorded in seismicity, deformation, gas chemistry, and visual observations. By 24 July the responsible government agencies had communicated that the volcano could erupt at any time. At 1548 on 26 July a phreatic (steam-driven) explosion ejected an ash plume that reached 200 m; a steam-rich plume rose to 600 m above the Ratu crater (figures 6, and 7). People were on the crater rim at the time and videos show a white plume rising from the crater followed by rapid jets of ash and sediment erupting through the first plume. Deposition of eruption material was 5-7 cm thick and concentrated within a 500 m radius from the point between the Rata and Upas craters, and wider deposition occurred within 2 km of the crater (figures 8 and 9). According to seismic data, the eruption lasted around 5 minutes and 30 seconds (figure 10). Videos show several pulses of ash that fell back into the crater, followed by an ash plume moving laterally towards the viewers.

Figure 6. These screenshots are from a video taken from the Ratu crater rim at Tangkuban Parahu on 26 July 2019. Initially there is a white gas-and-steam plume rising from the crater, then a high-velocity black jet of ash and sediment rises through the plume. This video was widely shared across multiple social media platforms, but the original source could not be identified.

Figure 7. The ash plume at Tangkuban Parahu on 26 July 2019. Courtesy of BNPB.

Figure 8. Volcanic ash and lapilli was deposited around the Ratu crater of Tangkuban Parahu during a phreatic eruption on 26 July 2019. Note that the deposits have slumped down the window and are thicker than the actual ashfall. Courtesy of BNPB.

Figure 9. Ash was deposited on buildings that line the Ratu crater at Tangkuban Parahu during a phreatic eruption on 26 July 2019. Photo courtesy of Novrian Arbi/via Reuters.

Figure 10. A seismogram showing the onset of the 26 July 2019 eruption of Tangkuban Parahu and the elevated seismicity following the event. Courtesy of PVMBG via Øystein Lund Andersen.

On 27 July, the day after the eruption, Øystein Lund Andersen observed the volcano using a drone camera, operated from outside the restricted zone. Over a period of two hours the crater produced a small steam plume; ashfall and small blocks from the initial eruption are visible in and around the crater (figure 11). The ashfall is also visible in satellite imagery, which shows that deposition was restricted to the immediate vicinity to the SW of the crater (figure 12).

Figure 11. Photos of the Ratu crater of Tangkuban Parahu on 27 July 2019, the day after a phreatic eruption. A small steam plume continued through the day. Courtesy of Øystein Lund Andersen.

Figure 12. PlanetScope satellite images showing the Ratu crater of Tangkuban Parahu before (17 July 2019) and after (28 July 2019) the explosion that took place on 26 July 2019. Natural color PlanetScope Imagery, copyright 2019 Planet Labs, Inc.

Another eruption occurred at 2046 on 1 August 2019 and lasted around 11 minutes, producing a plume up to 180 m above the vent. Additional explosions occurred at 0043 on 2 August, lasting around 3 minutes according to seismic data, but were not observed. Explosions continued to be recorded at 0145, 0357, and 0406 at the time of the PVMBG report when the last explosion was ongoing, and a photo shows an explosion at 0608 (figure 13). The explosions produced plumes that reached between 20 and 200 m above the vent. Due to elevated activity the Alert Level was increased to II on 2 August. Ash emission continued through the 4th. During 5-11 August events ejecting ash continued to produce plumes up to 80 m, and gas-and-steam plumes up to 200 m above the vent. Ashfall was localized around Ratu crater. The following week, 12-18 August, activity continued with ash and gas-and-steam plumes reaching 100-200 m above the vent. During 19-25 August, similar activity sent ash to 50-180 m, and gas-and-steam plumes to 200 m. A larger phreatic explosion occurred at 0930 on 31 August with an ash plume reaching 300 m, and a gas-and-steam plume reaching 600 m above the vent, depositing ash and sediment around the crater.

Figure 13. A small ash plume below a white gas-and-steam plume erupting from the Ratu crater of Tangkuban Parahu on 2 August 2019 at 0608. Courtesy of PVBMG (2 August 2019 report).

In early September activity consisted of gas-and-steam plumes up to 100-180 m above the vent with some ash plumes observed (figure 14). Two larger explosions occurred at 1657 and 1709 on 7 September with ash reaching 180 m, and gas-and-steam up to 200 m above the vent. Ash and sediment deposited around the crater. Due to strong winds to the SSW, the smell of sulfur was reported around Cimahi City in West Bandung, although there was no detected increase in sulfur emissions. A phreatic explosion on 17 September produced an ash plume to 40 m and a steam plume to 200 m above the crater. Weak gas-and-steam emissions reaching 200 m above the vent continued through to the end of September.

Figure 14. A phreatic explosion at Tangkuban Parahu in the Ratu crater at 0724 on 4 September 2019, lasting nearly one minute. The darker ash plume reached around 100 m above the vent. Courtesy of PVGHM (4 September 2019 report).

Geologic Background. Gunung Tangkuban Parahu is a broad shield-like stratovolcano overlooking Indonesia's former capital city of Bandung. The volcano was constructed within the 6 x 8 km Pleistocene Sunda caldera, which formed about 190,000 years ago. The volcano's low profile is the subject of legends referring to the mountain of the "upturned boat." The Sunda caldera rim forms a prominent ridge on the western side; elsewhere the rim is largely buried by deposits of the current volcano. The dominantly small phreatic eruptions recorded since the 19th century have originated from several nested craters within an elliptical 1 x 1.5 km summit depression.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); Øystein Lund Andersen (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: https://www.oysteinlundandersen.com/tangkuban-prahu/tangkuban-prahu-volcano-west-java-one-day-after-the-26th-july-phreatic-eruption/); Reuters (URL: https://www.reuters.com/news/picture/editors-choice-pictures-idUSRTX71F3E).

After a lull in activity at Sheveluch, levels intensified again in mid-December 2018 and remained high through April 2019, with lava dome growth, strong explosions that produced ash plumes, incandescent lava flows, hot avalanches, numerous thermal anomalies, and strong fumarolic activity (BGVN 44:05). This report summarizes activity between May and October 2019. The volcano is monitored by the Kamchatka Volcanic Eruptions Response Team (KVERT).

According to KVERT, explosive activity continued to generate ash plumes during May-October 2019 (table 13). Strong fumarolic activity, incandescence and growth of the lava dome, and hot avalanches accompanied this process. There were also reports of plumes caused by re-suspended ash rather than new explosions. Plumes frequently extended a few hundred kilometers downwind, with the longest ones remaining visible in imagery as much as 1,000-1,400 km away. One of the larger explosions, on 1 October (figure 52), also generated a pyroclastic flow. Some of the stronger explosions sent the plume to an altitude of 10-11 km, or more than 7 km above the summit. The Aviation Color Code remained at Orange (the second highest level on a four-color scale) throughout the reporting period, except for several hours on 6 October when it was raised to Red (the highest level).

Table 13. Explosions and ash plumes at Sheveluch during May-October 2019. Dates and times are UTC, not local. Data courtesy of KVERT.

Figure 52. An explosion of Sheveluch on 1 October 2019. A pyroclastic flow was also reported by KVERT this day. Courtesy of Yu. Demyanchuk, IVS FEB RAS, KVERT.

Numerous thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were observed every month. Consistent with this, the MIROVA (Middle InfraRed Observation of Volcanic Activity) system recorded thermal anomalies almost daily. According to KVERT, a thermal anomaly over Sheveluch was identified in satellite images during the entire reporting period, although cloudy weather sometimes obscured observations.

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/); 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/).

Short pulses of intermittent eruptive activity have been common at Piton de la Fournaise, the large basaltic shield volcano on La Réunion Island in the western Indian Ocean, for several thousand years. Over the last 20 years effusive basaltic eruptions have occurred on average twice per year. The activity is characterized by lava fountains and lava flows, and occasional explosive eruptions that shower blocks over the summit area and produce ash plumes. Almost all of the recent activity has occurred within the Enclos Fouqué caldera around the flanks of the central cone which has the Dolomieu Crater at its summit, although past eruptions in 1977, 1986, and 1998 have occurred at vents outside the caldera. Two eruptive episodes were reported during January-June 2019; from 18 February to 10 March, and from 11 to 13 June (BGVN 44:07). Three episodes during July-October 2019 are covered in this report, with information provided primarily by the Observatoire Volcanologique du Piton de la Fournaise (OVPF) as well as satellite instruments.

Three brief eruptive episodes took place during July-October 2019. In each case, slow ground inflation in the weeks leading up to the eruption was followed by sudden inflation at the time of the fissure opening and lava flow event. This was followed by a resumption of inflation days or weeks later. The first event took place during 29-30 July and consisted of three fissures opening on the N flank of the Dolomieu cone. It lasted for less than 24 hours, and the maximum flow length was about 730 m. The second event began on 11 August with two fissures opening on the S flank of the Dolomieu cone. The flows traveled downhill almost 3 km; activity ended on 15 August. Two new fissures opened during 25-27 October on the SSE flank of the cone; one was active only briefly while the second created a 3.6-km-long flow that stopped a few hundred meters before the major highway. The sudden surges of thermal energy from the eruptions are clearly visible in the MIROVA thermal data (figure 182). Each of the eruptive episodes was also accompanied by SO₂ emissions that were detected by satellite instruments (figure 183).

Figure 182. Three eruptive events took place at Piton de la Fournaise during July-October 2019 and appear as spikes in thermal activity during 29-30 July, 11-15 August, and 25-27 October. Additional events in late February-early March and mid-June are also visible in this MIROVA graph of thermal energy from 12 December 2018 through October 2019. Courtesy of MIROVA.

Figure 183. Sulfur dioxide emissions were measured from Piton de la Fournaise during each of the eruptive events that occurred in July (top left), August (top right and bottom left), and October (bottom right) 2019. Courtesy of NASA Goddard Space Flight Center.

Activity during July 2019. The last eruption, a series of flows from several fissures on the SSE flank of Dolomieu Crater near the crater rim (at the center of the Enclos Fouqué caldera), lasted from 11 to 13 June 2019 (figure 184). Ground deformation after the eruption indicated renewed inflation of the edifice which had been ongoing since May. OVPF reported an increase in seismicity beginning on 21 June which continued throughout July; the earthquakes were located near the NW rim of the Dolomieu Crater and on its NW flank. Four centimeters of elongation were recorded between two GNSS stations within the Enclos during late June and July prior to the next eruption. The next short-lived eruption took place during 29-30 July, near the location of the seismicity on the NW flank of the Dolomieu cone about 600 m E of the Formica Leo cone. The onset of the eruption was accompanied by rapid ground deformation of about 12-13 cm, recorded at a station that is located west of the Dolomieu Crater (figure 185).

Figure 184. Location maps of lava flows formed during the 11-13 June 2019 (left) and 29-30 July 2019 (right) eruptions at Piton de la Fournaise. Information derived from satellite data via the OI2 platform and aerial photos. Lava flows from June are shown as red polygons and eruptive fissures are shown as white lines. For the July event, the flows are shown in white. Courtesy of OVPF, OI2 and Université Clermont Auvergne (Monthly bulletins of the Piton de la Fournaise Volcanological Observatory, June and July 2019).

Figure 185. Horizontal surface displacements indicating inflation of Piton de la Fournaise of about four centimeters were gradual between 14 June and 28 July 2019 (left). Just prior to and at the onset of the eruption on 29 July, a much greater displacement of about 12 cm occurred, associated with the subsurface ascent of magma (right). Courtesy of OVPF-IPGP (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, July 2019).

The late July eruption began around 1200 local time on 29 July 2019 with the opening of three fissures over a distance of about 450 m on the N flank of Dolomieu cone, close to the tourist trail to the summit (figure 186). Lava fountains 20-30 m high were reported. Thermal measurements indicated flow temperatures of about 1,100°C at the base of the lava fountains; samples were collected for analysis (figure 187). Average discharge rates of 11.6 m³s were estimated for the eruption which ended less than 24 hours later, around 0430 on 30 July. The maximum flow length was about 730 m.

Figure 186. Three fissures opened at Piton de la Fournaise on 29 July 2019 and flows traveled 730 m downslope before stopping the next day. The fissures were located on the N flank of Dolomieu cone. Courtesy of OVPF-IPGP, Imaz PressRéunion, and Réunion La 1ère (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, July 2019).

Figure 187. Samples were collected for analysis by OVPF from the 29 July 2019 flow at Piton de la Fournaise. Courtesy of OVPF-IPGP (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, July 2019).

Eruption of 11-15 August 2019. During 1-10 August there were 33 shallow volcano-tectonic (VT) earthquakes located under the SE flank of Dolomieu cone; a new eruption began over this area on 11 August (figure 188). Two centimeters of inflation were recorded between the 29-30 July eruption and the 11-15 August event; this was followed by a rapid burst of inflation (tens of centimeters) at the onset of the eruption. Inflation resumed shortly after the eruption ended. The eruption began around 1620 local time on 11 August. Two fissures opened, one at 1,700 m elevation, and one at 1,500 m elevation on the SE flank, about 1,400 m apart (figure 189). Due to the steep slopes in the area, the lava flow quickly reached the "Grande Pentes" area before slowing down at the flatter "Piton Tremblet" area. The farthest traveled flow was cooling at an elevation of about 560 m, about 2 km from the National Road (RN2) on 14 August. The maximum effusion rate was measured at 9 m³/s. The eruption stopped on 15 August 2019 at 2200 local time after more than 6 hours of "piston gas" activity, and a brief pause in flow activity earlier in the day. About 3 million m³of lava were emitted, according to OVPF-IPGP. The flows from the 1,700 m and 1500 m altitude fissures reached maximum lengths of 2.9 and 2.7 km, respectively.

Figure 188. Locations of eruptive fissures that opened on 11 August 2019 on the SE flank of Dolomieu cone at Piton de la Fournaise, and the approximate locations of the associated flows. Courtesy of IVPF-IPGP / OPGC-LMV (Bulletin d'activité du mercredi 14 août 2019 à 15h30, Heure locale).

Figure 189. Lava flows from the Piton de la Fournaise eruption of 11-15 August 2019 emerged from two fissures on the SE flank of Dolomieu cone. The flows were both active on 13 August (left) at around 0930 local time. Visual and thermal images of the lava flows on 14 August at around 2100 local time (center and right) showed them continuing down the steep slope of the cone and spreading out over the shallower area below. Courtesy of OVPF-IPGP, LMV-OPGC (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, August 2019).

Activity during September-October 2019. Very little activity was reported during September 2019. Seismicity remained low with only 32 earthquakes reported during the month, and inflation, which had continued after the 11-15 August eruption, stopped at the beginning of September. Inflation resumed on 11 October. Two seismic swarms were recorded during October 2019. The first, on 21 October (207 events), lasted for about 40 minutes, and did not result in an eruption. The second began on 25 October and consisted of 827 events. It was followed by an eruption during 25-27 October located on the SSE flank of the Dolomieu cone. Deformation followed a similar pattern as it had during and prior to the eruptive events of July and August. Inflation of a few centimeters between 11 and 24 October was followed by rapid inflation of about 10 cm at the onset of the new eruption. Inflation resumed again after this eruption as well.

Two fissures opened during the 25-27 October eruption, one at 1,060 m elevation and one at 990 m. The first fissure was no longer active when viewed during an overflight 2.5 hours after it had opened. The flows moved rapidly until reaching the lower slope areas of the Grand Brule about 1.5-2 km downstream of the "Piton Tremblet" area. On 26 October only one vent was active with fountains 10-20 m high (figure 190). The lava discharge rates during the eruption averaged about 14 m³/s. The eruption ended at 1630 local time on 27 October after one hour of "gas piston" activity (figure 191). A total of about 1.8 million m³ of lava was emitted. The flows from the 990 m elevation site reached a maximum length of 3.6 km, and the lava flow front stopped about 230 m before reaching the RN2 National road (figure 192).

Figure 190. On 25 October 2019 the front of the active flow at Piton de la Fournaise had reached the level of the Piton Tremblet by 1700 local time (left). Image by PGHM (Bulletin d'activité du 25 octobre 2019 à 18h00, Heure locale). The following day, the active vent had lava fountains 10-20 m high (right) (Bulletin d'activité du samedi 26 octobre 2019 à 11h00, Heure locale). Courtesy of OVPF/IPGP.

Figure 191. The eruptive site of the 25-27 October 2019 eruption at Piton de la Fournaise had one flow still active on 27 October with 10-20 m high lava fountains (left). The flow front stopped that day a few hundred meters before the National Road (right). Courtesy of OVPF/IPGP (Bulletin d'activité du dimanche 27 octobre 2019 à 12h00, Heure locale).

Figure 192. The location of the 25-27 October 2019 lava flow at Piton de la Fournaise started at the very base of the SSE flank of Dolomieu cone and traveled 3.6 km E towards the Highway and the coast. Basemap from Google Earth, fissures (red) and flows (in white) derived from aerial photos. Courtesy of OVPF-IPGP (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, October 2019).

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 (OVPF-IPGP), 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/); 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/).

After a large, deadly explosive and effusive eruption during 1963-64, Indonesia's Mount Agung on Bali remained quiet until a new eruption began in November 2017 (BGVN 43:01). Activity continued throughout 2018 with explosions that produced ash plumes rising multiple kilometers above the summit, and the slow effusion of the lava within the summit crater. Increasingly frequent and intense explosions with ash emissions and incandescent ejecta characterized activity during February through May 2019 (BGVN 44:06). Two more explosions in June 2019 produced significant ash plumes; no further explosive activity occurred through October 2019. Information about Agung comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), the Darwin Volcanic Ash Advisory Center (VAAC), and multiple sources of satellite data. This report covers the end of the eruption in June and observations through October 2019.

After a large explosion on 31 May 2019, a smaller event occurred on 10 June. Another large explosion with an ash plume that rose to 9.1 km altitude was recorded on 13 June (local time). It drifted hundreds of kilometers before dissipating. No further explosive activity was reported through October 2019, only diffuse white steam plumes rising at most a few hundred meters above the summit. The Alert Level remained at III (of four levels) throughout the period. The record of thermal activity showed an increase during the explosive events of late May and June, but then decreased significantly (figure 57). There was no obvious thermal signature in satellite images that explained the small increase in thermal energy recorded by the MIROVA data at the end of August 2019.

Figure 57. The thermal energy at Agung increased significantly during the explosive events of late May and early June 2019, and then decreased substantially as seen in this MIROVA graph from 23 January through October 2019. There was no obvious satellite thermal signature to explain the brief increase in thermal energy in late August. Courtesy of MIROVA.

On 31 May 2019 a large explosion produced an ash plume that rose more than 2 km above the summit (BGVN 44:06, figure 56). The Darwin VAAC reported that it split into two plumes, one drifted E at 8.2 km and the other ESE at 6.1 km altitude, dissipating after about 20 hours early on 1 June. A small eruption with an ash plume that rose to 3.9 km altitude was reported the next day by the Darwin VAAC. It was detected in the webcam and pilot reports confirmed that it drifted E for a few hours before dissipating. PVMBG reported gray emissions to 300 m above the peak on 1 June and 100 m above the summit on 2 June. By 6 June the emissions were white, rising only 50 m above the summit. For several subsequent days, the summit was covered in fog with no observations of emissions.

On 10 June 2019 an explosion lasting 90 seconds was reported at 1212 local time; PVMBG noted a gray ash plume 1,000 m above the summit (figure 58). The Darwin VAAC confirmed the emission in satellite imagery and by pilot report; it was moving SW at 4.3 km altitude and then drifted S before dissipating by the end of the day. Early on 13 June local time (12 June UTC) a new explosion that was clearly visible in the webcam produced a large ash plume that drifted W and SW (figure 59). The explosion was recorded on the seismogram for almost four minutes and sent incandescent ejecta in all directions up to 700 m from the summit. The first satellite imagery of the plume reported by the Darwin VAAC suggested the altitude to be 9.1 km. A secondary plume was drifting W from the summit at 5.5 km altitude a few hours later. By six hours after the eruption, the 9.1 km altitude plume was about 90 km SSW of the Denpassar airport and the 5.5 km altitude plume was about 110 km W of the airport. By the time the higher altitude plume dissipated after about 14 hours, it had reached 300 km S of the airport. For the remainder of June, only diffuse white steam plumes were reported, rising generally 30-50 m above the summit, with brief pulses to 150-200 m during 27-29 June.

Figure 58. An ash plume rose 1,000 m above the summit of Agung on 10 June 2019. Top image courtesy of Rita Bauer (Volcano Verse), bottom image courtesy of PVMBG (Information on G. Agung Eruption, 10 June 2019).

Figure 59. A large eruption at Agung at 0138 local time on 13 June 2019 sent an ash plume to 9.1 km altitude and incandescent ejecta 700 m in all directions. Courtesy of Jaime S. Sincioco, screenshot from volcano YT webcam.

Although no further surface activity was reported at Agung during July through October 2019, PVMBG kept the Alert Level at III throughout the period. Only steam plumes were reported from the summit usually rising 50 m before dissipating. Steam emissions rose to 150 m a few times each month. Plumes were reported at 300 m above the summit on 6 July and 15 August. No thermal anomalies were visible in Sentinel 2 satellite images during the period.

Geologic Background. Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Rita Bauer, Volcano Verse (Twitter @wischweg, URL: https://twitter.com/wischweg/status/1137956367258570752); Jamie S. Sincioco, Philippines (Twitter @jaimessincioco, URL: https://twitter.com/jaimessincioco/status/1139109685796020224).

Most of the large edifice of Copahue lies high in the central Chilean Andes, but the active, acidic-lake filled El Agrio crater lies on the Argentinian side of the border at the W edge of the Pliocene Caviahue caldera. Infrequent mild-to-moderate explosive eruptions have been recorded since the 18th century. The most recent eruptive episode with ash plumes lasted from early June 2017 to early December 2018. After 8 months of quiet, renewed phreatic explosions and ash emissions began in August 2019 and were ongoing through October 2019. This report summarizes activity from January through October 2019 and is based on reports issued by Servicio Nacional de Geología y Minería (SERNAGEOMIN) Observatorio Volcanológico de Los Andes del Sur (OVDAS), Buenos Aires Volcanic Ash Advisory Center (VAAC), satellite data, and photographs from nearby residents.

Intermittent steam plumes were reported from the El Agrio crater at the summit during January-July 2019, but no ash emissions were seen. An increase in seismicity and changes in the crater lake level during March led SERNAGEOMIN to increase the Alert Level from Green to Yellow at the beginning of April. Fluctuating tremor signals in the first week of August coincided with satellite imagery that showed the appearance of dark material, possibly ash, on the snow around the summit crater. The first thermal anomaly appeared on 3 September and the first clear ash explosions were recorded on 11 September. Eruptive activity was intermittent through the end of the month; a series of larger explosions beginning on 30 September caused SERNAGEOMIN to raise the Alert Level from Yellow to Orange. A period of more intense explosive activity lasted through the first week of October. The larger explosions then ceased, but during the rest of October there were continuing observations of seismicity, ash emissions, and incandescent ejecta, along with multiple thermal anomalies in the summit area.

Observations during January-April 2019. Copahue remained at Alert Level Yellow with a 1-km exclusion radius during January 2019 after ash emission in December 2018. Ongoing degassing was reported with white plumes from El Agrio crater rising to 355 m (figure 25). The Alert Level was lowered to Green at the end of the month, and the exclusion radius was reduced to 500 m, although intermittent low-level seismicity in the region continued. SERNAGEOMIN reported a M 3.2 earthquake about 10 km NE of the summit, 2 km deep, on 29 January 2019. The acidic lake inside El Agrio crater was quiet at the end of the month (figure 26).

Figure 25. Degassing of steam from Copahue on 10 and 17 (inset) January 2019. Courtesy of OPTIC Neuquén (10 January) and SERNAGEOMIN (17 January).

Figure 26. El Agrio crater at Copahue on 31 January 2019. Courtesy of Valentina Sepulveda, Hotel Caviahue.

Steam plumes occasionally rose to 180 m above the crater during February 2019. A swarm of 117 volcano-tectonic (VT) seismic events on 22-23 February 2019 was located about 14 km NE of the volcano, with the largest events around a M 3.5. Steam plumes rose to about 280 m above the crater during March. SERNAGEOMIN noted an increase in seismicity during the month, and a decrease in the lake level within El Agrio crater. This led them to increase the Alert Level to Yellow (second on a four-level scale) at the beginning of April. Emissions remained minimal during April (figure 27); an 80 m high steam plume was reported on 4 April. The lake level continued to fall, based on satellite imagery, and a M 3.1 earthquake was reported on 29 April located about 10 km NE of the summit about 10 km deep.

Figure 27. Clear skies revealed no activity from the summit of Copahue on 7 or April 2019. The volcano was quiet throughout the month, although the Alert Level remained at Yellow. Image taken near Caviahue, 10 km E in Argentina. Courtesy of Valentina Sepulveda, Hotel Caviahue.

Observations during May-July 2019. Sporadic episodes of low-altitude steam plume degassing were noted during May 2019, but otherwise very little surface activity was reported (figure 28). On 13 May, a steam plume reached 160 m above the crater rim, and on 28 May, the tallest plume rose 200 m above the crater. Hybrid-type earthquakes were recorded early in the month, followed by a slow increase in the amplitude of the tremor signal. Seismicity increased slightly during the second half of the month with activity concentrated closer to the summit crater. A weak SO₂ plume was recorded by satellite instruments on 23 May. The level of the lake began increasing during the second half of the month.

Figure 28. No surface activity was visible at Copahue on 5 May 2019, but seismicity increased slowly during the month. Image taken near Caviahue. Courtesy of Valentina Sepulveda, Hotel Caviahue.

SERNAGEOMIN reported tremor signals with fluctuating amplitude throughout June 2019. Repeated episodes of low-altitude white degassing occurred around the El Agrio crater. On 7 June, a 300 m plume was observed above the crater; the level of the crater lake was variable. On 17 June a 400-m-tall white plume was observed above the crater. Seismicity, although low, increased during the second half of the month. Multiple episodes of low-altitude white degassing occurred around the active crater all during July 2019 (figure 29). On 9 July a plume rose about 450 m above the crater. On 16 July a white plume rose 250 m above the crater. SENAGEOMIN noted a rise in the rate of seismicity during the first half of the month; the tremor signal continued with fluctuating amplitude. Satellite instruments detected small SO₂ plumes on 4 and 9 July (figure 30).

Figure 29. A steam plume rose a few hundred meters above the summit of Copahue on 23 July 2019. Courtesy of Valentina Sepulveda, Hotel Caviahue.

Figure 30. The TROPOMI instrument on the Sentinel-5P satellite detected small SO2 plumes at Copahue on 4 and 9 July 2019. Courtesy of NASA Goddard Space Flight Center.

Activity during August-October 2019. Sentinel-2 satellite imagery from 2, 4, 7, and 9 August suggested the ejection of particulate material (figure 31), with dark streaks in the snow extending a few hundred meters E and SE from the crater. Images from the community of Caviahue on 3 and 4 August show distinct discoloration of the snow around the E side of the summit crater (figures 32 and 33). Small but discernible SO₂ plumes were detected by satellite instruments on 2, 3, 16, 19, 30, and 31 August. Fluctuating tremor signals continued during August with several episodes of low-altitude white degassing from the El Agrio crater; a white plume on 5 August rose 380 m above the crater. The lake level continued to drop and the Alert Level remained at Yellow.

Figure 31. Sentinel 2 satellite imagery of Copahue from late July and early August 2019 show fresh dark material deposited over the fresh winter snow, suggesting recent ejecta from the El Agrio crater. Top left: The summit was covered with fresh snow on 25 July 2019. Top right: A dark streak extends E then N from the El Agrio crater on 2 August. Bottom left: A streak of dark material trends SE from the crater over the snow on 4 August. Bottom Right: On 7 August a different streak extends E from the crater while fresh snow has covered the earlier streak. Courtesy of Sentinel Hub Playground.

Figure 32. At sunset on 3 August 2019, darker material was visible on the snow on the E side of the summit of Copahue; a dense steam plume rose from El Agrio crater. Courtesy of Valentina Sepulveda, Hotel Caviahue.

Figure 33. Particulates covered the fresh snow near the summit of Copahue on 4 August 2019, as seen from the community of Caviahue, about 10 km E. A steam plume rose from El Agrio crater. Courtesy of Valentina Sepulveda, Hotel Caviahue.

Distinct SO₂ plumes were again captured by satellite instruments on 1, 3, and 5-7 September 2019 (figure 34). The first thermal signature in nine months also appeared in Sentinel-2 satellite imagery on 3 September (figure 35). Midday on 9 September, seismometers recorded an increase in the amplitude of a continuous tremor. High clouds prevented clear views of the crater and no ash emissions were observed. Beginning on 11 September, low-energy long-period (LP) events were associated with infrasound signals and low-energy explosions that produced small ash plumes. The largest explosion produced a plume 250 m above the crater. Incandescence and high-temperature ejecta were observed around the emission point. The ash drifted ESE about 3 km. Ten explosions were reported between 11 and 12 September, associated with low-intensity acoustic signals and ash emissions. Plumes reached 430 m above the crater rim on 12 September. Ash deposits on the snow were visible in in Sentinel-2 images on 11 and 13 September, extending about 6 km E from El Agrio crater (figure 35). Images from the ground on 12 September indicated fresh ash on the E flank (figure 36).

Figure 34. Small but distinct SO2 plumes from Copahue were measured by the TROPOMI instrument on the Sentinel 5P satellite on 1 and 3 September 2019, and additionally on 5-7 September. Courtesy of NASA Goddard Space Center.

Figure 35. Sentinel-2 satellite images indicated thermal activity and ash emissions at Copahue on 3, 11, and 13 September 2019. Left: The first thermal anomaly in nine months appeared on 3 September. Middle: An ash streak trended E across the snow from El Agrio crater on 11 September. On 13 September, the streak was a wider cone that extended ESE for about 6 km. Courtesy of Sentinel Hub Playground.

Figure 36. Ash deposits coated snow on the E flank of Copahue on 12 September 2019, while a steam plume drifted SE from the crater, as seen from the community of Caviahue about 10 km E in Argentina. Courtesy of Valentina Sepulveda, Hotel Caviahue.

Although fresh snow had covered any ash deposits by 16 September 2019 (figure 37), small thermal anomalies appeared in Sentinel-2 imagery on 16 and 21 September. SO₂ plumes were measured by satellite instruments on 21 and 25 September. Photos from Caviahue on 25 September showed ash on the E flank and a steam-and-ash plume drifting NE (figure 38). Ashfall on the snow was visible in satellite imagery on 26 September, and covered a larger area on 28 September; there was also a substantial thermal anomaly that day (figure 39).

Figure 37. Fresh snow had covered over recent ash emissions at Copahue by 16 September 2019; thermal anomalies were detected in satellite data from the summit crater the same day. Courtesy of Valentina Sepulveda, Hotel Caviahue.

Figure 38. On a clear 25 September 2019 fresh ash covered snow on the E flank of Copahue, and an ash and steam plume was drifting NE from the El Agrio crater. The mountains are reflected in Lago Caviahue located about 12 km E in Argentina. Courtesy of Valentina Sepulveda, Hotel Caviahue.

Figure 39. Sentinel-2 imagery of Copahue on 28 September showed ashfall in a large area around the summit and a small ash plume (left); a substantial thermal anomaly was also visible within the El Agrio crater (right). Courtesy of Sentinel Hub Playground.

During the late afternoon of 30 September, three high-energy LP earthquakes were reported located 5.8 km NE of the El Agrio crater. They were accompanied by abundant lower energy earthquakes in the same area. The VT earthquakes were equivalent to a M 3.5. Inhabitants of Caviahue (12 km E) reported feeling several of the events; atmospheric conditions prevented observation of the summit. This sudden increase in seismicity prompted SERNGEOMIN to raise the Alert Level to Orange and increase the radius of the area of potential impact to 5 km. Seismicity (VT, LP and tremor earthquakes) continued at a high rate into 1 October. Argentina's geologic hazards and mining agency, Servicio Geologico Minero Argentino (SEGEMAR) also issued a notice of the increased warning level on 30 September (figure 40).

Figure 40. A dense steam plume rises from the active crater at Copahue in this image looking due E towards Caviahue and Lago Caviahue, 12 km E. The rim of the Caviahue caldera is in the distance. Argentina's SEGEMAR posted this photograph (undated) with their notice of the increase in warning level on 30 September 2019. Courtesy of SEGEMAR.

Cameras near the volcano detected ash plumes associated with explosions around the crater at 0945 on 1 October 2019 which continued throughout the first week of the month. Satellite imagery showed streaks of dark ash over snow trending SE and E and from the summit on 1 and 8 October (figure 41). Five separate explosions were recorded during 1-2 October. Persistent degassing was accompanied by episodes of ash emissions and incandescence at night. Seismicity continued during 2-3 October, but poor weather mostly obscured visual evidence of activity; a few pulses of white and gray emissions were observed. Seismic events were located 5-7 km NE at a depths of 0.7-1.7 km, and continued for several days. Clearer skies on 4 October revealed steam plumes and pulses of ash rising from El Agrio crater. Incandescence was visible at night. A ground-based image showed ash covering the E flank and an ash plume drifting NE down the flank (figure 42). The Buenos Aires VAAC reported weak ash emissions on 4 October moving NE at 3.4 km altitude. The webcam showed continuous ash emission from the summit during 4-5 October.

Figure 41. Sentinel-2 satellite imagery of Copahue showed dark streaks trending SE and E from the summit in early October. On 1 October 2019 (left) there was a narrow streak of ash to the SE and a steam plume drifting the same direction. On 8 Octobe0r (right), a wide cone of ashfall covered the E flank, and a plume of gray ash drifted NE over the edge of the deposit. Courtesy of Sentinel Hub Playground.

Figure 42. Gray ash covered areas of Copahue's E flank on 4 October 2019 and an ash plume drifted NE down the flank. Image from Caviahue, about 10 km E. Courtesy of Valentina Sepulveda, Hotel Caviahue.

White steam plumes with pulses of ash and incandescence at night were observed on 5 and 6 October. Seismic activity decreased on 6 October. The following day, SERNAGEOMIN lowered the Alert Level to Yellow and reduced the restricted zone to 1,000 m around the summit crater. While seismicity had decreased, ash emissions continued from low-level pulsating explosions which produced ash plumes that drifted E (figure 43). They observed that the total area to that date affected by ashfall was about 24.5 km², extending up to 5 km W and 6 km E from the summit. They also noted that a pyroclastic cone about 130 m across had appeared inside the crater. Ash emissions and explosions with incandescent ejecta continued during the second week of October (figure 44). A change in wind direction created a several-kilometer-long streak of ash trending SW from the summit by 13 October; a strong thermal anomaly that day indicated continued activity (figure 45). SO₂ plumes were recorded by satellite instruments on 1, 3, 4, and 13 October.

Figure 43. Ash and steam drifted E from the summit of Copahue on 7 October 2019, the day that SERNAGEOMIN lowered the Alert Level from Orange to Yellow. Courtesy of SEGEMAR.

Figure 44. Incandescent ejecta was visible at the summit of Copahue overnight on 11 October 2019 in the image from a local webcam. Courtesy of Culture Volcan.

Figure 45. A new dark streak of ash on snow trended SW from the El Agrio crater at Cophahue on 13 October 2019. The strong thermal anomaly the same day indicated the level of eruptive activity was still high. Natural color image based on bands 4,3, and 2; Atmospheric penetration rendering based on bands 12, 11, and 8a. Courtesy of Sentinel Hub Playground.

Seismicity continued for the rest of October, but no explosions were recorded. Sulfur dioxide emissions were recorded by satellite instruments on 18, 22, 23, and 30 October (figure 46). When weather permitted, constant degassing with episodes of ash emissions from the crater were visible during the day and incandescence appeared at night. Satellite imagery on 18, 23, and 28 October showed substantial ash plumes drifting in different directions from the summit. A large area around the summit crater was covered with dark ash on 18 and 23 October. Fresh snowfall had covered most of the area by 28 October, and the narrow dark streak trending SE underneath the ongoing ash plume was the only surface covered with material (figure 47). Distinct thermal anomalies appeared in satellite images on 16, 18, 23, and 31 October. A number of thermal alerts were recorded by the MIROVA system as well during the second half of the month.

Figure 46. The TROPOMI instrument on the Sentinel-5P satellite recorded SO2 emissions from Copahue on 18, 22, 23, and 30 October 2019. Satellite imagery on also showed ash plumes on 18 and 23 October. Courtesy of NASA Goddard Space Flight Center.

Figure 47. Distinct ash plumes and dark ashfall over snow on 18, 23, and 28 October 2019 at Copahue indicated ongoing eruptive activity (top row) through the end of the month. The large area of ash-covered snow visible on 18 and 23 October was covered with fresh snowfall by 28 October when the dense ash plume drifting SE left only a narrow dark trail of ashfall in the fresh snow underneath (right). Strong thermal anomalies were apparent on 18 and 23 October but obscured by dense ash on 28 October (bottom row). Natural color image based on bands 4, 3, and 2; atmospheric penetration rendering based on bands 12, 11, and 8a. Courtesy of Sentinel Hub Playground.

The highest plume noted by SERNAGEOMIN during the second half of the month rose 1,200 m above the crater on 22 October 2019 (figure 48). The Buenos Aires VAAC reported ash emissions from the summit visible in webcams almost every day in October. On 16 October, an ash plume was seen in satellite imagery moving SE at 3.4 km altitude under mostly clear skies; the webcam showed continuous ash emission. A faint plume was barely seen moving S in satellite imagery at 3.4 km altitude on 18 October; the webcam revealed continuous emission of gases and possible dilute volcanic ash. The VAAC reported ash emissions daily from 18-25 October. Drift directions varied from SE, moving to NE on 21-23 October, and back to E and SE the following days. The altitudes ranged from 3.0 to 4.3 km. On 20 October, the plume extended about 80 km SE. The ash appeared as pulses moving NE on 22 and 23 October at 4.3 km altitude. Emissions reappeared in satellite imagery on 28 and 30-31 October, drifting SE and NE at 3.4-3.7 km altitude; incandescence was visible overnight on 30-31 October from the webcam.

Figure 48. A plume of ash and steam from Copahue rose 1,200 m above the summit on 22 October 2019 and drifted NE. It was clearly visible from 25 km SW of the volcano in the El Barco Indigenous community of Alto Biobío, Chile, along with ash-covered snow on the SW flank. Courtesy of EveLyN.

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: Servicio Nacional de Geología y Minería (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); OPTIC Neuquén, Oficina Provincial de Tecnologías de la Información y la Comunicación- Gobierno de la Provincia del Neuquén, Neuquén, Argentina (URL: https://www.neuqueninforma.gob.ar/tag/optic/, Twitter: @OPTIC_Nqn, https://twitter.com/OPTIC_Nqn); 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); Valentina Sepulveda, Hotel Caviahue, Caviahue, Argentina (URL: https://twitter.com/valecaviahue, Twitter:@valecaviahue); Cultur Volcan, Journal d'un volcanophile, (URL: https://laculturevolcan.blogspot.com, Twitter: @CulturVolcan); EveLyn, Twitter: @EveCaCid (URL: https://twitter.com/EveCaCid/status/1186663015271321601).

This report summarizes activity at Turrialba during March-October 2019. Typical activity similar to that reported in late 2018 and early 2019 (BGVN 44:04) included periodic weak ash explosions and numerous emissions containing some ash. However, during this period activity appeared to diminish with time. Data were provided by weekly reports by the Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA).

According to OVSICORI-UNA, only highly diluted ash emissions were recorded from 22 April to 27 May (note that no reports were available online from the last week of March until 22 April). Weak ash explosions were again noted on 28 July, 4 August, and possibly on 20 October. OVSICORI-UNA reported more explosions or emissions containing ash on 25 and 28 October (table 9).

Table 9. Summary of reported activity at Turrialba, March-October 2019. Cloudy weather sometimes obscured observations. Maximum plume height is above the crater rim. Information courtesy of OVSICORI-UNA.

A report from Red Sismologica Nacional (RSN) about the 28 October ash explosion noted that it occurred at 1501 local time and lasted about 5 minutes. There were no reports of ashfall, but the crater webcam captured the small plume rising from the active vent. Incandescence in the active crater continued to be seen on the monitoring cameras.

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

Information Contacts: Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Red Sismologica Nacional (RSN) a collaboration between a) the Sección de Sismología, Vulcanología y Exploración Geofísica de la Escuela Centroamericana de Geología de la Universidad de Costa Rica (UCR), and b) the Área de Amenazas y Auscultación Sismológica y Volcánica del Instituto Costarricense de Electricidad (ICE), Costa Rica (URL: https://rsn.ucr.ac.cr/).

A large explosive and effusive eruption lasting about 11 months during 1963-64 at Indonesia's Mount Agung on Bali produced voluminous ashfall, devastating pyroclastic flows that caused extensive damage, and over 1,000 fatalities. The volcano remained largely quiet until renewed seismicity began in August 2017, the prelude to a new eruptive episode, which started in late November 2017 and is ongoing. Self and Rampino (2012) and Fontijn et al. (2015) published detailed summaries of historical activity at Agung prior to this new episode; a brief summary of their work is provided.

Information about the new eruptive episode comes from Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG), also known as the Indonesian Center for Volcanology and Geological Hazard Mitigation (CVGHM), Badan Nasional Penanggulangan Bencana (BNPB) which is the National Board for Disaster Management, the Darwin Volcanic Ash Advisory Center (VAAC), and various sources of satellite data. The first two months of this new episode, through December 2017, are discussed in this report.

Summary of 1963-64 eruption. The February 1963 to January 1964 eruption, Indonesia's largest and most devastating eruption of the twentieth century, was a multi-phase explosive and effusive event that produced both basaltic andesite tephra and andesite lava (Self and Rampino, 2012). After a few days of felt earthquakes on 16 and 17 February 1963, explosive activity began at the summit on 18 February. This was followed the next day by the effusion of about 0.1 km³ of andesite lava which was extruded until 17 March 1963, when a large explosive eruption generated pyroclastic density currents (PDCs) and lahars that devastated wide areas N, SW, and SE of the volcano (figure 1) (Fontijn et al, 2015).

Figure 1. Map of Gunung Agung and vicinity, eastern Bali, showing the extent of the 1963 lava flow (cross-hatched), pyroclastic flow deposits (stippled), and lahar deposits (dark shading) of the 1963–1964 eruption (after unpublished map courtesy of Indonesian Volcanological Survey). Sg is Siligading village, where many fatalities occurred. Reproduced from Self and Rampino (2012, figure 3).

Explosive activity continued intermittently until a second explosive phase of similar intensity occurred two months later, beginning on 16 May 1963 with reported ash plumes reaching 10 km above the 3-km-high summit (figure 2). This phase produced the greatest proportion of the pyroclastic flow material from the eruption and led to additional death and destruction in villages at the foot of the volcano (Self and Rampino, 2012). Explosive outbursts continued intermittently until 17 January 1964. The total death toll of the eruption was estimated between 1,100 and 1,900 (see references in Fontijn et al., 2015). A total estimated volume of erupted magma was ca 0.4 km³ (Self and Rampino, 2012).

Figure 2. Photograph reported to be of the 16 May 1963 eruption column at Agung; the view is from the SW, perhaps near Rendang (shown on figure 1). Photo courtesy of the family of Denis Mathews, reproduced from Self and Rampino (2012, figure 2b).

Activity between 1964 and 2017. Almost no activity was reported from Agung during 1964-2017. Weak solfataric activity from within the summit crater was reported in 1989 (SEAN 14:07). MODVOLC thermal alerts were reported intermittently on one or two days during a few years (2001, 2002, 2004, 2006, 2008, 2012, 2013), but all of the alerts were located on the middle or lower flanks, suggesting their source was agriculture or forest fires, unrelated to volcanic activity. Chaussard et al. (2013) reported inflation centered on the summit at a rate of 7.8 cm/year between mid-2007 and early 2009, followed by slow deflation at a rate of 1.9 cm/year until mid-2011 (the last acquired data).

Summary of September-December 2017 Activity. Increases in seismic activity were first noted at Agung during mid-August 2017. Exponential increases in the rate of events during the middle of September led PVMBG to incrementally raise the Alert Level from I to IV (lowest to highest) between 14 and 22 September. Steam-and-gas emissions were intermittently observed 50-500 m above the summit crater from the end of September through October, with occasional bursts as high as 1,500 m. Seismicity dropped off almost as quickly as it rose, beginning on 20 October, and then continued a more gradual decrease through the end of the month and into November. The number and intensity of hot spots observed within the summit crater increased during September, then leveled off during October.

Ash emissions first appeared on 21 November, rising to 700 m above the summit. Ash density and heights of plumes increased several times during the rest of November to about 3,000 m. Ashfall as deep as 5 mm affected neighboring communities, and was reported several hundred kilometers from the summit; the international airport about 60 km SW was forced to close for a few days at the end of the month. Thermal data indicated effusion of lava into the summit crater at the end of November. After 30 November, emissions continued, primarily comprised of steam and gas, with intermittent plumes of dense ash, rising up to 2.5 km above the summit throughout December.

Activity during August-September 2017. In their monthly report of volcanic activity for August 2017, PVMBG noted that 49 volcanoes, including Agung, were listed at Alert Level 1, meaning "Normal", with no apparent increases in visual or seismic activity. The first signs of renewed unrest at Agung appeared as an increase in the rate of deep volcanic earthquakes (VA or Vulkanik Dalam) beginning on 10 August 2017. Shallow volcanic earthquakes (VB or Vulkanik Dangkal) began to increase two weeks later on 24 August, followed by an increase in the number of local tectonic earthquakes on 26 August (figure 3). Based on this increased seismicity, and an observation on 13 September of new solfataric activity at the bottom of the summit crater, PVMBG raised the Alert Level the following day from Level I (Normal) to Level II (Beware); the Aviation Color Code was raised to Yellow on a four-color scale (Green, Yellow, Orange, Red). The deeper earthquakes (VA) had a seismic amplitude range from 3-10 mm. The shallow earthquakes (VB) had an amplitude range of 2-7 mm. Otherwise, there was no surface expression of activity during September.

Figure 3. Seismic activity at Agung between 1 July and 13 September 2017. The Y-axis is the number of daily earthquakes. The increase in deep volcanic seismicity (VA, or Vulkanik Dalam) that began on 10 August 2017 was followed two weeks later by an increase in shallow volcanic seismicity (Vulkanik Dangkal or VB). Courtesy of PVMBG (Peningkatan Tingkat Aktivitas Gunung Agung, 14 September 2017).

The Agung Volcano Observatory (AVO) is located in Rendang village about 8 km SW. Webcams are located in Rendang and in Bukit Asah, about 8 km W. On 15 September 2017 a steam emission was observed rising 50 m above the crater rim. The AVO issued a VONA on 18 September noting a rapid increase in volcanic earthquake activity with a small hot spot detected in satellite data. This contributed to them raising the Alert Level again to Level III (Standby), resulting in a 6-km-radius exclusion zone activated around the summit, extending to 7.5 km on the N, SE, and SSW flanks where the pyroclastic flows of 1963 had caused the most damage. Many of the 50,000 village residents within the 6 km exclusion zone began voluntary evacuations. The communities affected included Jungutan (7 km S) and Buana Giri (12 km SE) villages in the Bebandem District, Sebudi Village (6 km SW) in the Selat Subdistrict, Besakih Village (12 km SW) in the Rendang Subdistrict, and Dukuh (4 km NE) and Ban (7.5 km NW) villages in the Kubu Subdistrict. About 9,500 people had voluntarily evacuated from the villages by 22 September 2017.

The observatory issued another VONA on 19 September 2017, reporting an 'ash cloud' at 0255 UTC (1055 Central Indonesia Time, or WITA). It was described as a dense, white plume moving to the W. Around the same time (0240 UTC) MODVOLC recorded ten thermal alerts on the N and E flanks. Bali's Regional Disaster Management Agency (BPBD) reported in Antara News on 19 September that the source of the smoke and ash were forest fires caused by excessively dry conditions.

A VONA issued by AVO in the morning of 22 September stated that a steam emission about 50 m above the summit drifted NW. During the evening of 22 September, PVMBG raised the Alert Level to Level IV (Caution), the highest of the four-level scale, based primarily on continuing increases in seismicity. They expanded the exclusion zone to 9 km around the summit, and to 12 km in the areas S, SE, and NNE. The number of evacuees had risen to nearly 35,000 people by 24 September. Steam-and-gas plumes were intermittently observed rising to 200 m above the crater rim during the rest of September. By 26 September, PVMBG reported increasing seismic activity with 579 deep volcanic (VA) quakes, 373 shallow quakes (VB), and 50 local tectonic events that day. Seismicity continued to escalate through the end of the month. By the end of September, the government was assisting with the logistics of evacuating tens of thousands of livestock, primarily cattle, as well as over 90,000 people from within and around the 9 km exclusion zone. MAGMA Indonesia reported that new steaming and thermal areas within the summit crater expanded during the last week of the month.

Activity during October 2017. Narrow steam plumes rose 50-200 m above the summit crater during the first half of October. The rate of earthquakes during the last week of September and the first week of October continued to fluctuate at high levels, averaging 1-3 per minute, and more than 600 per day. By the first week of October, shallow earthquakes alone had increased to more than 200 per day, suggesting the possibility of magmatic activity at shallow depth. Satellite data showed increasing steam emissions along the NE edge of the crater rim. Tiltmeter data showed sudden deflation on 1 October, followed by continued inflation through 5 October. AVO released a VONA on 7 October noting a steam plume rising 1,500 m above the summit crater at 1245 UTC and drifting E (figure 4).

Figure 4. A steam plume rose 1,500 m above the summit of Agung on 7 October 2017. Courtesy of PVMBG (Penurunan Status Gunungapi Agung, Bali Dari Level IV (awas) Ke Level III (siaga) Tanggal 29 Oktober 2017 Pukul 16.00 WITA).

During the second half of the month, steam plumes were denser and rose more frequently to 200-500 m above the summit crater. BNPB flew drones over the summit on 20 and 29 October 2017 and captured 400 aerial photographs (figures 5 and 6). The images revealed a widening of the fracture zone on the E side of the summit crater, and a new fracture on the SE side.

Figure 5. A view into the summit crater of Agung on 20 October 2017, taken by a BNPB drone. Steam fumaroles rose from the NNE flank. N is to the left. Courtesy of PVMBG (Penurunan Status Gunungapi Agung, Bali Dari Level IV (awas) Ke Level III (siaga) Tanggal 29 Oktober 2017 Pukul 16.00 WITA).

Figure 6. A view into the summit crater of Agung on 29 October 2017, taken by a BNPB drone. The steam plumes rose from the NE corner of the summit crater. The NE rim of the crater slopes away to the upper left. Courtesy of PVMBG (Penurunan Status Gunungapi Agung, Bali Dari Level IV (awas) Ke Level III (siaga) Tanggal 29 Oktober 2017 Pukul 16.00 WITA).

PVMBG noted a decline in seismicity beginning on 20 October 2017 which continued through the end of the month (figure 7), leading them to lower the Alert Level from IV to III on 29 October, and reduce the exclusion zone to a 6 km radius, plus a 7.5 km area in the NNE, SE and SSW sectors. In their late October report, they observed that remote sensing thermal infrared data had detected an increase in the thermal energy beginning on 10 July 2017, in the form of an increased number of hot spots within the summit crater. During August and September, the number of hot spots had increased significantly and correlated with the increases in seismicity (figure 8). The intensity of the thermal anomalies then decreased during October. Inflation resumed in mid-August and peaked in mid-September. After that, the GPS data indicated deflation at lower levels, but uplift of 6 cm occurred near the summit. The deformation rate slowed after 20 October.

Figure 7. Daily seismic activity at Agung from 27 July-29 October 2017. Seismicity decreased noticeably on 20 October 2017, leading PVMBG to lower the Alert Level from IV to III on 29 October. Note that the vertical axis counting the number of daily seismic events ranges from 0 to 1,200, while in figure 3 the same axis ranges from 0 to 14. Courtesy of MAGMA Indonesia (Penurunan Status Gunungapi Agung, Bali dari Level IV (AWAS) ke Level III (SIAGA) Tanggal 29 Oktober 2017 pukul 16.00 WITA).

Figure 8. Satellite thermal imagery from Citra-Sentinel 2 revealed an increase in the number and intensity of hotspots within the summit caldera of Agung during September 2017, followed by a decrease in early October. Courtesy of PVMBG (Penurunan Status Gunungapi Agung, Bali Dari Level IV (awas) Ke Level III (siaga) Tanggal 29 Oktober 2017 Pukul 16.00 WITA).

Activity during November 2017. For the first three weeks of November, dense white steam plumes rose 50-500 m above the summit crater. A VONA issued late on 11 November reported a 500-m-high steam plume. Seismicity continued at a much lower rate than during late September-October, with tens of daily events as opposed to hundreds.

The first ash emission of the current eruption occurred on 21 November at 1705 local time; the plume rose to 700 m and drifted ESE (figure 9). Trace amounts of ashfall were reported in the Pidpid-Nawehkerti area about 9 km SE. At the time of the first ash emission, BNPB reported the number of evacuees living in temporary housing at about 25,000. The emission was preceded by a low-frequency tremor. Multiple volcanic ash advisories were issued by the Darwin VAAC on 21 November, although the ash was not visible in satellite imagery due to weather clouds. Continuous tremor with 2-5 mm amplitude was recorded the following three days, and ash-and-steam emissions rose 300-800 m above the summit crater.

Figure 9. The first reported ash emission from Agung in 53 years rose 700 m and drifted SE on 21 November 2017. Courtesy of PVMBG (Letusan Gunung Agung Selasa, 21 November 2017 Pukul 17.05 WITA).

A larger emission on 25 November sent black-gray ash plumes 2,000 m above the crater rim (figure 10) which then drifted W. The Darwin VAAC reported an ash plume visible in satellite imagery at 7.6 km altitude drifting WSW. Emissions continued later in the day, rising 4.6-6.7 km altitude and extending SE. Bright incandescence at the summit crater was observed that night. Ashfall was reported to the WSW in the villages of Menanga and Rendang (12 km SW) at the AVO Post, and also in Besakih Village, located in the upper part of Pempatan (8 km W). A number of international flights were cancelled from the I Gusti Ngurah Rai International Airport in Denpasar (60 km SW), affecting about 2,000 passengers, although the airport remained open.

Figure 10. An ash emission rose at least 1,500 m above the summit of Agung on 25 November 2017 and drifted W. Courtesy of PVMBG (Letusan Gunung Agung 25 November 2017 Pukul 17:30 Wita).

Around 0545 local time the following day (26 November), the intensity of the ash emissions increased; the top of the plume reached 3,300 m above the summit at 1100 local time, and was drifting SE and E (figure 11). Ashfall was reported in many areas downwind including North Duda (9 km S), Duda Timur (12 km S), Pempetan, Besakih, Sideman (15 km SSW), Tirta Abang, Sebudi (6 km SW), Amerta Bhuana (10 km SSW), and some villages in Gianyar (20 km WSW) (figure 12). The largest amount, deposits 5 mm thick, was reported in Sibetan (11 km SSE). Trace amounts of ash were also reported much farther away, in Nusa Penida (an island 40 km S), Lombok (100 km ESE), and Sumbawa, 250 km E on the island of West Nusa Tenggara. Explosions from the crater were audible 12.5 km away that evening. Incandescence at the summit was observed from Bukit Asah and Batulompeh. The Darwin VAAC reported continuous ash emissions to 7.9 km altitude drifting SE throughout most the day, increasing to 9.1 km later in the day; ashfall was also reported at the international airport.

Figure 11. A dense plume of ash rose 3,000 m above the summit of Agung and drifted ESE on 26 November 2017. Courtesy of PVMBG (Peningkatan Status Gunungapi Agung, Bali Dari Level III (siaga) Ke Level IV (awas), 27 November 2017).

Figure 12. Ash from an eruption of Agung on 26 November 2017 covered garden plants in Jungutan Village, 7 km SE. Courtesy of Reuters.

The airport in Denpasar was forced to close during 27-29 November 2017. On those days ash drifted in multiple directions at different altitudes; it was observed drifting E at 9.1 km altitude, SW at 7.6 km altitude, and was moving S below 6.1 km. This increase in emissions led PVMBG to raise the Alert Level from III to IV on 27 November. Pictures and video showed a white steam plume adjacent to a gray ash plume rising from the crater, suggesting two distinct sources (figure 13).

Figure 13. A white steam plume and dense gray ash both rose from the summit of Agung on 27 November 2017. Photo by K. Parwata, courtesy of Sutopo Purwo Nugroho, Twitter.

A single MODVOLC thermal alert appeared at the summit that day, along with a strong thermal anomaly in the MIROVA system data (figure 14) consistent with the appearance of new lava in the summit crater. The tiltmeter installed at the Yehkori station 4 km S of the summit showed continued inflation of up to 6 microradians between 22 and 27 November (figure 15). PVMBG also increased the exclusion zone to a radius of 8 km from the summit crater plus areas 10 km from the summit to the NNE, SE, S, and SW.

Figure 14. A MIROVA plot of satellite infrared data for the year ending 23 February 2018 showed the first thermal anomaly from Agung in late November 2017, consistent with the emergence of lava in the summit crater. Courtesy of MIROVA.

Figure 15. A steady inflation was measured by the tiltmeter located at the Yehkori station 4 km S of the summit of Agung between 22 November and 27 November. Courtesy of PVMBG (Peningkatan Status Gunungapi Agung, Bali Dari Level III (siaga) Ke Level IV (awas), 27 November 2017).

MAGMA Indonesia reported that beginning with the ash eruption on 21 November, lahars appeared in the Tukad Yehsa, Tukad Sabuh, and Tukad Beliaung drainages on the S flank, as well as Tukad Bara on the N flank. As of the end of November 2017, these lahars had impacted houses, roads, and agricultural areas. Although ash emissions increased, and lava was confirmed within the summit crater during the last week of November, the number of seismic events remained well below the values recorded during September and October (figure 16).

Figure 16. Seismicity at Agung decreased significantly beginning on 20 October 2017 and remained well below 200 daily events throughout November, even though ash emissions began on 21 November. Courtesy of PVMBG (Peningkatan Status Gunungapi Agung, Bali Dari Level III (siaga) Ke Level IV (awas), 27 November 2017).

Ash emissions were reported by PVMBG rising to 3,000 m above the summit and drifting S on 27 November (figure 17). Continuing ash emission during 28-29 November rose to 2,000-4,000 m above the summit and drifted WSW (figure 18). Continuous seismic tremors were recorded during 28 November-1 December.

Figure 17. Ash plumes from Agung rose to altitudes of around 6,000 m (3,000 m above the summit crater) and drifted S on 27 November 2017. Image courtesy of MAGMA Indonesia (Peningkatan Status Gunungapi Agung, Bali Dari Level Ill (SIAGA) ke Level IV (AWAS), 27 November 2017 10:07 WIB, Ir. Kasbani, M.Sc.).

Figure 18. A dense plume of steam and ash rose from Agung and drifted away from this villager and his livestock on 28 November 2017. Courtesy of CNN.

With the increase in ash emissions during the last days of November 2017, satellite instruments also recorded significant releases of SO₂ (figure 19). MAGMA Indonesia reported on 1 December that satellite data also recorded high temperatures consistent with new lava within the crater on 27, 28, and 29 November 2017. They estimated the volume of lava in the crater to be about 20 million cubic meters, equivalent to about a third of the total crater volume. The base of the ash-and-steam plumes was often reddish during 29 November-5 December reflecting incandescence from the lava in the crater (figure 20).

Figure 19. The concentrations of SO2 emitting from Agung increased to levels that were easily detected by the Ozone Mapper Profiler Suite (OMPS) on the Suomi National Polar-orbiting Partnership (Suomi-NPP) satellite on 27 (top) and 28 (bottom) November 2017. The concentration of SO2 is measured in Dobson Units, a measure of the molecular density of the SO2 in the atmosphere. These NASA Earth Observatory images were created by Joshua Stevens, using OMPS data from the Goddard Earth Sciences Data and Information Services Center (GES DISC).

Figure 20. Incandescence appeared at the base of the ash-and-steam plume at Agung on 29 November 2017, consistent with lava effusion in the summit crater. Courtesy of MAGMA Indonesia (Perkembangan Terkini Aktivitas Gunung Agung (1 Desember 2017 21:00 WITA), 2 December 2017 07:55 WIB, Ir. Kasbani, M.Sc.).

By 29 November, continuous ash emissions were rising to 6.4 km altitude and drifting from the SW towards the S, becoming diffuse over the Denpasar region (figure 21). The plume was observed moving E at the same elevation on 30 November, lowering to 5.5 km later in the day. Although emissions were primarily steam and gas beginning on 30 November, pilot reports on 1 December indicated ash was still visible SE of Agung, and steam-and-ash emissions were continuing. Steam-only emissions were reported on 2 December rising less than 1,000 m above the summit.

Figure 21. Gas-and-ash emissions from Agung on 29 November 2017 were drifting both W and S in this false-color image generated by the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite. The image uses a combination of shortwave infrared light and natural color, making it easier to differentiate between ash, clouds, and forest. The plumes appear to rise from two vents in the volcano's summit crater. Courtesy of NASA Earth Observatory.

Activity during December 2017. Steam, gas, and ash emissions continued throughout December 2017. During the first two weeks, emissions were primarily steam and gas, rising up to 2,000 m (figure 22), and incandescence was often observed at the summit. Dense gray ash emissions were observed, however, during 1-2 December. BNPB noted on 5 December that 63,885 evacuees were distributed in 225 evacuation shelters. On 8 December at 0759 a brief event generated a dense ash plume that rose 2.1 km above the crater rim and drifted W (figure 23). Minor amounts of ash were deposited on the flanks, and lapilli were reported in Temakung. A second ash plume rose 3 km at 1457 later that day.

Figure 22. A burst of dense steam rose as high as 1,500 m from the crater of Agung on 5 December 2017 at 0848 local time (WITA) and drifted E, after which only a narrow diffuse plume remained. View is from the S. Courtesy of Sutopo Purwo Nugroho, Twitter.

Figure 23. An eruption at Agung on 8 December 2017 at 0759 WITA sent a dense gray ash plume 2,100 m above peak to the W. View is from the S. Courtesy of Sutopo Purwo Nugroho, Twitter.

The Darwin VAAC reported multiple daily explosions during 8-15 December, creating ash plumes that drifted NW, W, and WSW at altitudes between 4.3 and 5.5 km. The explosions were visible in the webcams and from ground-based observers, and occasionally in satellite imagery when not blocked by weather clouds. VONA's were issued for events on 8 and 12 December. Multiple events during 11-12 December sent plumes rising up to 2.5 km above the crater rim and drifting NW and W (figure 24).

Figure 24. A small ash emission rose from the crater of Agung during the early morning of 11 December 2017. Courtesy of Sutopo Purwo Nugroho, Twitter.

The Darwin VAAC reported larger ash emissions to 7.6 km altitude on 15 and 16 December interspersed with lower altitude (5.5-6.1 km) plumes. Continuing, regular discrete emissions during 16-17 December rose to 6.1 km and drifted WNW. An overhead image of the summit crater of 16 December revealed that, since a similar photo was taken on 20 October, new lava had filled about 1/3 of the crater with an estimated 30 million cubic meters of material (figure 25).

Figure 25. Repeated overhead images of the Agung summit crater taken on 20 October and 16 December 2017 showed new lava filling about 1/3 of the crater with an estimated 30 million cubic meters of material. Posted on Twitter by Sutopo Purwo Nugroho for BNBP.

Discrete emissions to 5.5 km moving N and NNE were common during 18-21 December. Ash and steam drifted both E and W from the summit on 22 December. An ash emission on 23 December rose to 5.8 km and drifted NE, after which repeated emissions continued, rising to 4.6 km (figure 26). Ash fell on the flanks and in Tulamben, Kubu (9 km NE). In the morning of 24 December, a much larger plume drifting W at 10.7 km altitude was visible in satellite imagery. It dissipated after a few hours, and a separate plume was observed drifting NE at 5.5-5.8 km (figure 27); emissions continued throughout the day and into the next. PVMBG reported that the ash deposits from the NE-drifting plume were up to 3 mm thick (figure 28).

Figure 26. An event at Agung on 23 December 2017 sent a dense, gray plume to 2,500 m above the crater rim at 1157 WITA. View is from a village on the W flank, likely about 7 km from the summit. Courtesy of Sutopo Purwo Nugroho, Twitter.

Figure 27. Agung erupted steam and ash with a plume height of 2,000-2,500 m on 24 December 2017 at 1005 WITA. Courtesy of Sutopo Purwo Nugroho, Twitter.

Figure 28. Map showing distribution and thickness of volcanic ash and lapilli from the ash emissions at Agung that began on 24 December 2017 at 1005 WITA. A thin layer of ash was deposited in a narrow NE trending band on the NE side of Agung. Courtesy of Sutopo Purwo Nugroho, Twitter.

As of 25 December, BNPB reported just over 70,000 evacuees spread out in 239 shelters. Discrete ash emissions continued through the end of the month rising as high as 2 km above the crater rim and drifting in several different directions. The last VAAC report of 2017 indicated an ash plume drifting W at 4.3 km altitude on 31 December.

References: Chaussard E, Amelung F, Aoki Y, 2013, Characterization of open and closed volcanic systems in Indonesia and Mexico using InSAR time series. J Geophys Res Solid Earth, 118:3957–3969. DOI: 10.1002/jgrb.50288.

Fontijn K, Costa F, Sutawidjaja I, Newhall C G, Herrin J S, 2015, A 5000-year record of multiple highly explosive mafic eruptions from Gunung Agung (Bali, Indonesia): implications for eruption frequency and volcanic hazards. Bull Volcanol, 77: 59. DOI: 10.1007/s00445-015-0943-x.

Self S, Rampino M, 2012, The 1963–1964 eruption of Agung volcano (Bali, Indonesia). Bull Volcanol 74:1521–1536. DOI: 10.1007/s00445-012-0615-z.

Geologic Background. Symmetrical Agung stratovolcano, Bali's highest and most sacred mountain, towers over the eastern end of the island. The volcano, whose name means "Paramount," rises above the SE caldera rim of neighboring Batur volcano, and the northern and southern flanks extend to the coast. The summit area extends 1.5 km E-W, with the high point on the W and a steep-walled 800-m-wide crater on the E. The Pawon cone is located low on the SE flank. Only a few eruptions dating back to the early 19th century have been recorded in historical time. The 1963-64 eruption, one of the largest in the 20th century, produced voluminous ashfall along with devastating pyroclastic flows and lahars that caused extensive damage and many fatalities.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); NASA Earth Observatory, EOS Project Science Office, NASA Goddard Space Flight Center, Goddard, Maryland, USA (URL: http://earthobservatory.nasa.gov/); NASA Goddard Space Flight Center (NASA/GSFC), Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); 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/); Antara News (URL: https://bali.antaranews.com); Sutopo Purwo Nugroho, Head of Information Data and Public Relations Center of BNPB via Twitter (URL: https://twitter.com/Sutopo_PN); Cable News Network (CNN), Turner Broadcasting System, Inc. (URL: http://www.cnn.com/); Reuters (URL: http://www.reuters.com/).

An eruption at Bezymianny continued into April 2017 with ash plumes and lava flows (BGVN 42:06). Similar activity was reported from May through December 2017. Observations came from reports from the Kamchatka Volcanic Eruptions Response Team (KVERT) and Tokyo Volcanic Ash Advisory Center (VAAC) advisories.

KVERT reported on 26 May that activity had decreased after an explosion on 9 March and the effusion of several lava flows onto the dome flanks. Though gas-and-steam emissions continued, along with thermal anomalies identified in satellite images. The Aviation Color Code (ACC) was lowered to Yellow (the second lowest level on a four-color scale). Moderate gas-and-steam emissions continued throughout the reporting period.

On 15 June KVERT reported that the temperature of a thermal anomaly identified in satellite images had increased, and that the webcam recorded a gas-and-steam plume rising to an altitude of 4 km and drifting SSE. Hot avalanches of material originated from the lava dome. The next day, 16 June, a powerful explosion began at 1653 (local) that produced an ash cloud that rose to an altitude as high as 12 km and drifted 700 km E and SE. Nighttime incandescence from the lava dome was observed afterwards, and a lava flow emerged from the W flank of the dome. The ACC was raised to Red (the highest level on a four-color scale), but lowered back to Orange (the second highest level) about 5 hours later. At 2110 (local) the ash cloud was 212 x 115 km in size and drifting E; the leading edge of the cloud was about 245 km E. Strong gas-and-steam emissions and incandescence above the lava dome could be seen on 18 June (figure 23).

Figure 23. Photo of Bezymianny on 18 June 2017 showing the plume from a strong gas-and-steam emission, along with incandescence over the lava dome. Courtesy of A. Belousov, IVS FEB RAS.

During 20 June-29 September a daily thermal anomaly over Bezymianny was identified by KVERT in satellite images, when not obscured by clouds. A lava flow continued down the W flank of the dome, and incandescence from the dome was usually visible at night. Moderate gas-and-steam activity continued.

According to KVERT, by the first week of October the volcano had quieted somewhat, although moderate gas-steam activity continued. KVERT reported that a lava flow continued down the W flank of the lava dome through 4 October, but no mention was made of a lava flow in their reports after 4 October. Weak daily thermal anomalies were recorded when the volcano was not obscured by clouds. On 5 October, the ACC was lowered to Yellow.

On 18 December hot avalanches on the SE flank of the lava dome were recorded by a webcam, prompting KVERT to raise the ACC to Orange. A strong explosion that started at 1555 (local) on 20 December generated ash plumes that rose to an altitude of 10-15 km, prompting KVERT to raise the ACC to Red. Ash plumes identified in satellite data drifted at least 320 km NE. Later that day satellite images indicated decreased activity; the ACC was lowered back to Orange. Moderate gas-and-steam emissions continued on 29 December, and a lava flow likely effused onto the N flank of the lava dome. Thermal anomalies continued to be identified in satellite images. The ACC was lowered to Yellow.

Thermal anomalies. During May-December 2017 thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were only observed during a small portion of June and July 2017 (most days between 19-26 June, most days during the first week of July, 17-18 July, and 28 July). In contrast, the MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected numerous hotspots every month, with the most intense cluster during the middle of June through the middle of September. Virtually all MIROVA hotspots were within 5 km of the summit.

Geologic Background. Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences (KB GS RAS) (URL: http://www.emsd.ru/); 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/).

Recent activity at Copahue through December 2016 consisted of gas and steam plumes with minor amounts of ash. Eruptive activity ended in late December 2016, but ash emissions began again in early June 2017. Distinct ash emissions decreased after July, and crater incandescence was no longer reported. However, persistent tremor and degassing with sporadic ash continued through 2017.

This report through December 2017 is based on information obtained from the Buenos Aires Volcanic Ash Advisory Center (VAAC), the Southern Andes Volcanological Observatory (OVDAS), and the Servicio Nacional de Geología y Minería (National Geology and Mining Service) (SERNAGEOMIN). Volcano Alert Levels are set by SERNAGEOMIN (on a four-color scale) and by the Chilean Oficina Nacional de Emergencia del Ministerio del Interior (National Office of Emergency of the Interior Ministry) (ONEMI), on a three-color scale), for alerts to individual communities in the region.

OVDAS-SERNAGEOMIN reported that webcams recorded an increase in ash emissions on 4 June 2017. There were no significant changes in the magnitude or number of earthquakes recorded by the seismic network. The report noted that due to inclement weather making visual observations difficult, the observatory did not know if the ash emission began in the early hours of 4 June, or the day before. On the same day, OVDAS-SERNAGEOMIN raised the Alert Level to Yellow; ONEMI set a Yellow Alert for the communities of Villarrica, Pucón, and Curarrehue in La Araucanía, and for Panguipulli in Los Ríos.

During 5-15 June 2017 the seismic network detected long-period earthquakes. Gas plumes constantly rose from El Agrio crater and on several days contained ash. The highest plume, detected on 5 June, rose 300 m and drifted E.

The Buenos Aires VAAC reported that on 1 July the webcam recorded a steam-and-gas plume with minor ash near the summit. Webcam and satellite images analyzed by the Buenos Aires VAAC showed that during 7-8 July steam plumes with minor amounts of ash rose to altitudes of 4-4.3 km altitude and drifted ESE. During 16-17 July similar plumes rose to altitudes of 3-3.4 km and drifted N and NW. According to ONEMI, OVDAS-SERNAGEOMIN reported that during 16-31 July surficial activity had decreased. The webcam recorded constant gas emissions with sporadic ash rising no more than 280 m from El Agrio crater. Crater incandescence was visible during clear weather. The Alert Level remained at Yellow, and SERNAGEOMIN recommended no entry closer than 1 km of the crater. ONEMI continued an Alert Level of Yellow for the municipality of Alto Biobío.

In August, activity continued to decrease. Degassing was constant and sometimes contained ash. Plumes did not exceed 500 m in height and incandescence was absent. During the first half of the month, 23 seismic events occurred, 20 of which were volcanic-tectonic; tremor associated with the degassing was constant. During the latter half of August, SERNAGEOMIN lowered the Alert Level to Green. Because gas emissions continued, SERNAGEOMIN suggested that the public stay beyond a radius of 500 m of the active crater.

SERNAGEOMIN reports for November and December indicated that some seismic activity continued. In November, 337 earthquakes occurred, 261 of which were volcanic-tectonic. Tremor associated with degassing continued, and incandescence was reported on some days. Based on satellite and webcam views, the Buenos Aires VAAC reported that during 21 and 24-27 November diffuse steam plumes containing minor amounts of ash rose and drifted E and NE. Plumes rose to altitudes of 3.3-3.6 km during 25-26 November.

On 2 December, one volcanic-tectonic earthquake occurred at 1758 local time. More than 20 volcanic-tectonic earthquakes occurred about 2245 on 5 December. The SERNAGEOMIN report for December noted persistent tremor associated with gas and ash emissions, and that constant gas plumes with sporadic ash rising to a maximum height of 1,300 m above the summit was recorded by the web camera. The Alert Level remained Green through December 2017.

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: Servicio Nacional de Geología y Minería, (SERNAGEOMIN), Observatorio Volcanológico de Los Andes del Sur (OVDAS), Avda Sta María No. 0104, Santiago, Chile (URL: http://www.sernageomin.cl/); Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI), Beaucheff 1637/1671, Santiago, Chile (URL: http://www.onemi.cl/); 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/).

A central cone slightly lower than the summit caldera rim has been the site of numerous small-to-moderate historical eruptions recorded since the time of the Spanish conquistadors at Columbia's Galeras volcano. Persistent steam and gas, and occasional ash emissions from multiple vents around the summit have characterized activity for many years. Steam plumes are generally visible from two sites at the summit of the pyroclastic cone. Two small craters, known as Chavas and El Paisita, are located on the N and W rim of the larger central summit crater. Information for this report was gathered primarily from monthly technical reports provided by the Observatorio Vulcanológico y Sismológico de Pasto (OVSP) of the Sevicio Geologico Colombiano (SGC). Four webcams document the activity from the Observatorio Vulcanológico y Sismológico de Pasto (OVSP) located in Pasto (8 km ESE), from Consacá (11 km W), from the top of Galeras in the area called Barranco Alto (2.6 km NW), and from the SW flank at an area called Bruma.

The last time an Alert Level 1 (Red: imminent eruption or in progress) was issued was on 25 August 2010 when a plume of gas and ash rose 300 m above the summit and dispersed ash over numerous communities up to 30 km away. Seismicity decreased the following day, and steam and gas-only emissions returned. Fumarolic activity persisted throughout 2011, with only a single mention of possible low ash content in the plumes observed on 31 March and 1 April. Steam plumes rose a few hundred meters from the summit crater during January-May 2012. Seismic swarms were recorded in April and May.

An eruption with ash emissions began on 13 May 2012 and persisted until 30 January 2014 (BGVN 37:04, 38:03, 39:01). A summary of activity during that eruptive episode is provided below, along with additional information not previously reported. Activity after the end of that eruption, from February 2014 through December 2017, included only steam and gas emissions from the summit crater, and low levels of seismicity.

Activity during 2012. During January and February 2012, steam plumes rose 900-1,000 m above the summit, emerging from the El Paisita and Chavas vents at the N and W rims of the summit crater (figure 130). Plumes rose higher during March, reaching 1,900 m. VT seismic swarms were reported between 11 and 16 April 2012, and deformation sensors recorded inflation towards the W flank beginning in April. Most of the seismicity was located within the vicinity of the summit crater at depths less than 5 km. Steam plumes rose to 2,300 m above summit in April (figure 131).

Figure 130. Volcán Galeras, viewed at 1828 local time from Barranco Alto (2.6 km NW) on 16 February 2012, showed typical low-level steam plumes rising from vents on the N and W rims of the summit crater. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, febrero de 2012).

Figure 131. A substantial steam plume rose from Galeras in this image taken from OVSP (Observatorio Vulcanológico y Sismológico de Pasto) headquarters (8 km SE) on 20 April 2012 at 0738 local. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, abril de 2012).

Steam plumes rose less than 200 m above the summit at the beginning of May; a second swarm of VT seismic events on 9 and 10 May 2012 preceded a new sequence of ash emissions that began on 13 May. Pulsating plumes of ash rose less than 800 m and deposited material primarily on the upper NW flank. Inflation continued to be measured in the inclinometers on the W flank, coinciding with the area of the epicenters of the 9-10 May seismic swarm. Ash-bearing emissions were reported on 13, 14, 17, 26 (figure 132), 27, and 30 May.

Figure 132. An ash emission rose from Galeras at 0802 local time on 26 May 2012 and was recorded by the Barranco Alta webcam on the NW flank. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, mayo de 2012).

Ash emissions continued during June-August 2012. Plume heights during the period ranged from 1,300-2,500 m above the summit. Plumes recorded on 12 and 17 June (figure 133) resulted in ashfall in Sandoná (14 km NW) and Samaniego (32 km NW), Mapachico (9 km NE), and Genoy (7 km NNE). Additional days with reports of ash emissions included 5, 6, 8, 19, 22, 27 and 29 June. Ash-bearing emissions were reported on at least 16 days during July with reports of ashfall in Maragato, Chorillo (18 km W) and Genoy. Ash plumes rose to 2,500 m above the summit during at least nine different days of August, and ashfall was reported again in the Genoy area.

Figure 133. Seismogram and spectrogram of a tremor (TRE) event recorded at 1605 local time on 17 June 2012 that was associated with an ash emission from Galeras as viewed from the Barranca (upper left), OVSP (upper and lower right), and Consacá (lower left) webcams (11 km W). Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, junio de 2012).

Tremor associated with gas and ash emissions persisted throughout September 2012; another VT seismic swarm was reported on 28 September. Ash-bearing emissions were reported during at least seven days of the month, and reached 2,000 m above the crater (figure 134). During at least 16 days of October, tremors were associated with ash emissions that rose as high as 1,800 m. On 19 October, fine-grained ashfall was reported by personnel of the Observatory who were working on the upper NE flank.

Figure 134. Gas and ash emissions at Galeras on 12 September 2012 were recorded photographically from the El Vergel Shelter in Pasto around 1805 local time, at most of the digital seismograph stations around the volcano, and also at the analog recorder at the Anganoy station (upper right) in Pasto (Provided by Architect Darío Gómez of the Municipal Council for Risk and Disaster Management (DMGRD) of the municipality of Pasto). Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, septiembre de 2012).

Gas and ash plumes rose 1,000-1,300 m during November and December 2012 and were also associated with tremor signals. The most significant emissions were observed on 1, 7, 14, 22, 23, 29 and 30 November, and 17 (figure 135), 19, 21, 26, 27 and 29 December.

Figure 135. Ash emissions rose from Galeras on the morning of 17 December 2012 as seen in this series of images from the OVSP webcam while seismographs recorded tremor-type events. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, diciembre de 2012).

Activity during 2013. Continuous inflation towards the western flank was measured beginning in April 2012. Similar deformation processes continued at Galeras during much of 2013. The 'Crater' inclinometer located about 0.8 km E of the summit crater showed the most significant amount of westward inflation (figure 136).

Figure 136. Resultant vectors for the electronic inclinometers at Galeras for the period between 25 October 2012 and 31 January 2013 show 2,962.1 microradians (µrad) of movement to the W at the 'Crater' inclinometer as well as movement to the N and SW at several other instruments. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, enero de 2013).

Eruptive activity continued in a similar manner to 2012 throughout 2013. During January, ash-bearing emissions rose up to 1,000 m at least nine times and drifted in various directions. The emission event of 22 January caused ashfall in Sandoná (13 km NW). During February, the most notable seismic activity was several tremor events associated with ash emissions. Plume heights remained below 1,500 m and were observed on at least 11 days of the month. There were reports of ashfall in San Isidro, the upper part of the municipality of Sandoná, NW of the volcano, during the morning of 24 February. Most of the ash emissions during March 2013 were deposited on the upper NW flank. The Crater, Cobanegra, and Calabozo inclinometers continued to show movement associated with inflation towards the W flank during March and April. Gas and ash plumes reached 1,000 m above the summit on 6, 7, 11, 22 and 25 March. Activity was similar during April, with plumes rising to 1,200 m and seismic tremors associated with ash and gas emissions reported on at least 13 days (figures 137 and 138).

Figure 137. Seismograms registered a tremor-type event (TRE) on 5 April 2013 at Galeras that was associated with ash emissions captured in the Barranca webcam. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, abril de 2013).

Figure 138. Gas and steam emissions rose from the crater at the summit of the pyroclastic cone at Galeras on 24 April 2013. Image taken from the caldera rim at the summit. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, abril de 2013).

Seismic activity decreased somewhat during May 2013, although tremor signals associated with ash and gas emissions were noted on at least eight occasions. The pulsating ash plumes were small, and deposited material mostly on the NW flank. The deformation network recorded stability at the Crater inclinometer for the first time in many months. SGC noted a seismic swarm during the evening of 22 May that included a tremor event that lasted for 11 minutes and possibly included ash emissions.

Emissions during June 2013 were mostly steam that rose to 1,300 m, but ash plumes were reported on seven days. The frequency of seismic activity remained steady during July, but the amount of energy released increased significantly. The Crater inclinometer showed deflation. Ash and gas plumes were noted on 6, 12, 13, 17 and 22 July rising as high as 1,500 m. Seismic frequency and energy both decreased during August and September 2013, and inclinometers showed little change in deformation. Plume heights, mostly gas and steam, remained below 500 m. Tremors associated with ash emissions were reported on five days of August and on 3, 11 and 14 September.

Seismicity increased in both amplitude and frequency during October and November 2013. The majority of the VT seismicity was located on the NE flank at 5-10 km depth. Steam plume heights remained below 600 m; emissions reported on 8 and 11 October included ash (figure 139). In addition to steam plumes observed throughout November, ash plumes were reported rising to 1,000 m on 17, 23, and 30 November. Seismicity decreased during December 2013 while deformation remained stable. Ash plumes were reported on 4, 13, 26, 27, and 31 December associated with tremor events (figure 140).

Figure 139. Ash emissions rose from the summit crater at Galeras on 11 October 2013. They were photographed by Mr. Mario Alberto Caicedo, Radio and TV Analyst, from the RTVC Galeras station, at the caldera rim near the summit. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, octubre de 2013).

Figure 140. Seismograms recorded frequencies associated with tremor (TRE) events on 4 December 2013 while the Barranca webcam recorded ash emissions. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, diciembre de 2013).

Activity during 2014. Tremor events during 11-14, 21, 23, and 27-30 January 2014 were associated with ash and gas emissions (figure 141) that reached 850 m above the summit. During the early hours of 11, 13, and 23 January, incandescence was observed at the crater. The last confirmed ash emission of the year occurred on 30 January 2014.

Figure 141. Emissions of steam and ash on 29 January 2014 were captured by the Bruma webcam (SW of the cone) while seismograms registered tremor events. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, enero de 2014).

A decrease in both frequency and energy levels of seismicity were reported during March 2014. SGC noted several tremor-type seismic events associated with gas emissions; steam plumes rose up to 1,000 m above the summit. Although they reference "gas and ash" emissions in a few photographs, only steam is visible in the photographs from March. Reports of activity by SGC for April and May 2014 refer to only steam plumes rising 1,000 m from the summit from the vents on the N and W sides of the crater rim. No further reports are available for Galeras for 2014.

Activity during 2015-2017. Throughout 2015, SGC reported only steam plumes rising from the two vents at the summit of the Galeras pyroclastic cone, known as the Chaldean fumarole fields (Las Chavas) on the W rim, and the El Paisita on the N rim (figure 142). Plume heights were as high as 700 m in January, but dropped below 200 m by May, where they remained for the rest of the year. Inflation to the W began again in September 2014 and continued through May 2015.

Figure 142. Steam plumes rose a few hundred meters above the summit of the pyroclastic cone at Galeras on 9 April 2015. This type of activity was typical for all of 2015. Photo from the Barranco webcam NW of the summit. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, abril de 2015).

Minor variations in seismic frequency and energy levels fluctuated throughout 2016 and 2017, but there were no reported particulate emissions. Steam emissions from the two primary vents at the summit crater (Las Chavas and El Paisita) rarely rose more than 200 m above the summit, often drifting NW.

An inspection of the summit crater by SGC on 25 August 2016 revealed a deep vent with several points of gas emissions (figure 143), including areas on the N wall (El Paisita) and the E wall (Las Alterada). The W wall (Las Chavas) had a cave-like entrance of 50 m diameter with fumarolic activity on the back wall and the ceiling that condensed into a sulfur-rich water on the floor of the opening. The El Pinta vent had no observed emissions. A rare 200-m-high steam plume rose from the crater in October 2016, but otherwise activity remained very low at Galeras throughout 2017 (figure 144).

Figure 143. An inspection of the summit crater at Galeras by SGC on 25 August 2016 revealed a deep vent with several points of gas emissions including areas on the N wall (El Paisita) and the E wall (Las Alterada). The W wall (Las Chavas) had a cave-like entrance of 50 m diameter with fumarolic activity on the back wall and the ceiling that condensed into a sulfur-rich fluid on the floor of the opening. The El Pinta vent had no emissions. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, agosto de 2016).

Figure 144. Low-level steam emissions seen from the Bruma webcam SW of the summit of Galeras on 3 August 2017 were typical activity for the entire year. Courtesy of SGC (Informe mensual de actividad de Los Volcanes Galeras, Cumbal, Doña Juana, Azufral, Las Ánimas, Chiles Y Cerro Negro, agosto de 2017).

Geologic Background. Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Long-term extensive hydrothermal alteration has contributed to large-scale edifice collapse on at least three occasions, producing debris avalanches that swept to the west and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid-Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html).

The most recent eruptive period at Heard began in September 2012 (BGVN 38:01). Direct observations are rare at this remote volcano, but the presence of lava flows can frequently be discerned using infrared satellite data. Thermal anomalies were intermittent, with some episodes of clearly stronger activity, during 2016 and through September 2017 (BGVN 42:10).

During all of 2017, MODIS infrared satellite data analyzed using the MODVOLC algorithm showed anomalies near the summit only on 2, 16, and 26 September, and on 1 and 22 October. The MIROVA system also detected numerous hotspots within 5 km of the volcano through late October. One additional significant anomaly was identified on approximately 12 November 2017 (figure 31). No further significant anomalies were noted through February 2018.

Figure 31. Low to moderate power thermal anomalies in MODIS data were identified by the MIROVA system in September and October, with another on approximately 12 November 2017. Courtesy of MIROVA.

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/).

A series of three explosions at Kanlaon on 18 June 2016 sent ash plumes as high as 3 km above the crater and caused minor ashfall in neighborhoods W, SW, and NW of the volcano (BGVN 42:01). This was followed by steam plumes through 25 July 2016. The active Lugud crater (figure 4) has been the source of 21 reported eruptions since 1969; the latest eruption took place in December 2017. Information summarized here for activity from September 2016 through December 2017 was provided by the Philippine Institute of Volcanology and Seismology (PHIVOLCS).

Figure 4. Photo looking down from the rim into the historically active Lugud crater at Kanlaon on 7 March 2010. Courtesy of Billy Lopue, used under Creative Common BY-NC-ND 2.0 (https://creativecommons.org/licenses/by-nc-nd/2.0/).

PHIVOLCS reported on 5 May 2017 that since the last phreatic eruption in June 2016 there had been a general decline in activity: seismicity was at baseline levels, no significant deformation had been detected since August 2016, sulfur dioxide emissions were low, and no steaming had been observed since 29 September 2016. The Alert Level was lowered to 0 (on a scale of 0-5), though the public was warned to not enter the 4-km-radius Permanent Danger Zone (PDZ).

Between 24 June and 18 August 2017 the seismic network detected 244 volcanic earthquakes. The PHIVOLCS report noted that the increased seismic activity could be followed by phreatic explosions at the summit crater, despite the absence of visible degassing or steaming from the active vent. The Alert Level was raised to 1. The number of daily volcanic earthquakes increased after 18 August. In their 15 November report, PHIVOLCS indicated that during the previous 24 hours there had been 279 deep volcanic earthquakes recorded (compared to five the day before). This prompted them to raise the Alert Level to 2 (moderate level of unrest), where it remained for the rest of the year. The next day, the number recorded was 217. After that the daily number of volcanic events dropped considerably, especially after 21 November. Based on PHIVOLCS reports, the number of daily volcanic earthquakes during the first eight days of December 2017 varied from one to seven.

On 9 December an approximately 10-minute-long, low-energy phreatic explosion began at 0947 that was heard as far away as La Castellana, Negros Occidental (15 km SW). A plume of voluminous steam and dark ash rose 3-4 km above the summit vent (figure 5), and minor amounts of ash fell in Sitio Guintubdan (23 km W), and barangays W of the volcano (Ara-al, Sag-ang, and Ilihan). The eruption was preceded by the resumption of degassing at the summit crater at 0634, detectable as continuous low-energy tremor during periods when the summit was not visible; degassing was last observed September 2016.

Figure 5. Photo of the 9 December 2017 plume rising from Kanlaon as seen from Barangay Manghanoy, La Castellana, Negros Occidental, about 15 km SW. Photo by Ms. Ritchel Demerin Villanueva; posted by PHIVOLCS on Facebook.

Only three volcanic earthquakes were detected on 10 December, but then the number increased to 155 the next day. The number of daily events earthquakes increased again to 578 on 13 December, rose to 1,007 the next day, and peaked at 1,217 on the 15 December. The earthquake count dropped to 149 on 16 December before returning to six or fewer through 19 December. White steam plumes rose 800 and 300 m above the crater on 13 and 14 December, respectively. White plumes were diffuse on 15 December; weather clouds prevented views of the summit area during 16-18 December. Sulfur dioxide emissions were 603-687 tons per day during 13-14 December.

PHIVOLCS reported that during 19-20 December there were 412 volcanic earthquakes. A low-energy, explosion-type earthquake was detected at 0233 on 21 December associated with gas emissions from the summit area. Later in the day steam plumes rose 400 m and drifted NE. The number of daily volcanic earthquakes increased to 957 the next day and then decreased to less than 20 per day during 22-23 December. The daily earthquake count increased to 382 and 776 events on 24 and 25 December, respectively, decreased to 82 on 26 December, and the dropped to three or fewer over the last days of the year. Weather clouds often prevented observations , but white plumes rose 300 m and drifted NE, NW, and SW on 21 December, and 700 m on 26 December. A steam plume on 30 December was seen rising 500 m above the crater rim and drifting SW. On 30 December 2017, sulfur dioxide levels were measured at an average of 1,946 tonnes/day.

Geologic Background. Kanlaon volcano (also spelled Canlaon), the most active of the central Philippines, forms the highest point on the island of Negros. The massive andesitic stratovolcano is dotted with fissure-controlled pyroclastic cones and craters, many of which are filled by lakes. The largest debris avalanche known in the Philippines traveled 33 km SW from Kanlaon. The summit contains a 2-km-wide, elongated northern caldera with a crater lake and a smaller, but higher, historically active vent, Lugud crater, to the south. Historical eruptions, recorded since 1866, have typically consisted of phreatic explosions of small-to-moderate size that produce minor ashfalls near the volcano.

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); Billy Lopue, flickr (URL: https://www.flickr.com/photos/21905294@N03/).

After an explosive eruption during January-September 2011, Shinmoe-dake (Shinmoedake), a stratovolcano of the Kirishimayama volcano group, was quiet except for gas-and-steam plumes and slowly decreasing seismicity that returned to baseline levels by May 2012 (BGVN 37:07). The following report summarizes events through December 2017, and relies primarily on reports from the Japan Meteorological Agency (JMA).

On 22 October 2013, JMA reported that no eruptions had been detected at the volcano since the eruption on 7 September 2011. Earthquake activity and sulfur dioxide emissions were both below the detection limit. The Alert Level was lowered from 3 to 2 (on a scale of 1-5).

According to JMA, an eruption began at 0534 on 11 October 2017, prompting the agency to raise the Alert Level to 3 (figure 21). Ash plumes rose 300 m above the crater rim (2 km altitude) and drifted NE. Volcanic tremor amplitude increased and inflation was detected. Ashfall was noted in at least four towns in the Miyazaki (to the E) and Kagoshima (to the SW) prefectures. Based on JMA notices, pilot observations, and satellite data, the Tokyo Volcanic Ash Advisory Center (VAAC) reported that ash plumes rose to an altitude of 1.8-2.1 km on 11 October and 3.4 km on 12 October.

Figure 21. An ash plume rises from the Shinmoedake crater at Kirishimayama after its eruption on 11 October 2017. Courtesy of Tomoaki Ito / Kyodo News.

Gas measurements taken during field surveys on 12 and 13 October showed that the sulfur dioxide flux was 1,400 tonnes/day, an increase from 800 tonnes/day measured on 11 October. Volcanic tremor fluctuated but the amplitude was slightly lower. During 0823-1420 on 14 October, an event produced a tall plume which rose 2.3 km above the crater rim. Another event, at 1505, generated a grayish-white plume that rose 1 km and then blended into the weather clouds. Ashfall was reported in Kirishima (22 km SW) in the Kagoshima prefecture, in Kobayashi (14 km NE) in the Miyazaki prefecture, and reaching as far as Hyuga city (92 km NE). An increase in low-frequency earthquakes was recorded on 16 October.

The eruption lasted almost continuously until the morning of 17 October. The eruption plume usually rose several hundred meters about the crater rim, though on 14 October the plume rose as high as 2.3 km. Sulfur dioxide flux exceeded 10,000 tonnes/day. Cloudy weather conditions prevented webcam views during 19-20 October. Plumes rose 200-600 m on 21, 23, and 24 October. During an overflight on 24 October, scientists observed a white plume rising from the active vent on the E side of the crater, and puddles in multiple low areas of the crater.

Activity during 25 October-20 November 2017 activity continued to be slightly elevated. White plumes rose 100-500 m above the crater rim, though weather clouds sometimes prevented visual observations. Almost daily field surveys by JMA revealed no particular changes in the fumarolic and fissure areas near the cracks on the W flank, or to the thermally anomalous zone below the crack. Sulfur dioxide fluxes were as high as 200 tonnes/day. The Alert Level remained at 3.

Geologic Background. Kirishimayama is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene dominantly andesitic group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located Karakunidake being the highest. Onamiike and Miike, the two largest maars, are located SW of Karakunidake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Miike to Ohachi, and at Shinmoedake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Associated Press (URL: https://www.ap.org/en-us); Kyodo News (URL: https://english.kyodonews.net).

Since an eruptive episode in May 2007, Loopevi has been quiet except for a thick gray plume on 24 February 2008 and a short-lived increase in activity in December 2014 (BGVN 32:05, 34:08, 40:05). This report covers activity during January 2015-December 2017. Data were primarily drawn from reports issued by the Vanuatu Geohazards Observatory (VGO) and the Wellington Volcanic Ash Advisory Center (VAAC).

Based on a pilot observation and webcam views, the Wellington VAAC reported that a short-lived steam-and-gas plume beginning at 0500 on 13 January 2017 produced a that rose no higher than 3 km in altitude and drifted SE. That same day VGO reported that the Volcanic Alert Level (VAL) was raised to 3 (on a scale of 0-5); it was lowered to Level 2 on 17 January and then to Level 1 on 20 February.

Steam plumes were again observed on 23 September by the web camera, prompting VGO to raise the VAL to 2, indicating major unrest (danger around the crater rim and specific area, considerable possibility of eruption, chance of flank eruption). Observation flights on 30 September and the first week of October showed that the activity was occurring only in the active craters below the summit crater (figure 24). Photographs and thermal infrared images taken during the flights confirmed that activity consisted of hot volcanic gas and steam. VGO reported that photos and satellite images acquired at the end of November confirmed that gas-and-steam emissions were continuing.

Figure 24.Aerial view of the active cone at Lopevi on 3 October 2017. Courtesy of VGO.

The unrest continued through at least December 2017, and the VAL remained at 2. The Wellington VAAC noted that on 20 December a low-level plume was visible in satellite and webcam images drifting NW at an altitude of 1.5 km.

Geologic Background. The small 7-km-wide conical island of Lopevi, known locally as Vanei Vollohulu, is one of Vanuatu's most active volcanoes. A small summit crater containing a cinder cone is breached to the NW and tops an older cone that is rimmed by the remnant of a larger crater. The basaltic-to-andesitic volcano has been active during historical time at both summit and flank vents, primarily along a NW-SE-trending fissure that cuts across the island, producing moderate explosive eruptions and lava flows that reached the coast. Historical eruptions at the 1413-m-high volcano date back to the mid-19th century. The island was evacuated following major eruptions in 1939 and 1960. The latter eruption, from a NW-flank fissure vent, produced a pyroclastic flow that swept to the sea and a lava flow that formed a new peninsula on the western coast.

Information Contacts: Vanuatu Geohazards Observatory (VGO), Department of Geology, Mines and Water Resources of Vanuatu (URL: http://www.geohazards.gov.vu/, http://www.vmgd.gov.vu/vmgd/index.php/geohazards/volcano); Wellington Volcanic Ash Advisory Centre (VAAC), Meteorological Service of New Zealand Ltd (MetService), PO Box 722, Wellington, New Zealand (URL: http://www.metservice.com/vaac/, http://www.ssd.noaa.gov/VAAC/OTH/NZ/messages.html).

Reventador has exhibited historical eruptions with numerous lava flows and explosive events since the 16th century. Eruptive activity has been continuous since 2008. Persistent ash emissions and incandescent block avalanches characterized activity during 2016; occasional pyroclastic and lava flows were also reported (BGVN 42:11). Similar activity continued during January-September 2017; information for this period is provided primarily by the Instituto Geofisico-Escuela Politecnicia Nacional (IG-EPN) of Ecuador and also from satellite-based MODIS infrared data.

Summary of activity, January-September 2017. Activity remained high at Reventador during January-September 2017. The strongest (4 km long) pyroclastic flow since 2002 occurred in late June along with a large lava flow that traveled over 2.5 km, the longest since 2008. Visual observations of ash emissions and block avalanches were often difficult due to weather conditions that obscured views of the summit certain times of the year (figure 60, table 9). Thermal alerts and anomalies recorded by satellite instruments complemented the visual information reported by IG-EPN (figure 61) and showed near-continuous activity as well. Variation in the frequency of the different types of seismic events fluctuated throughout the period (figure 62) and generally corresponded to variations in the surface activity.

Figure 60. Activity at Reventador during January-September 2017 included MODVOLC alerts (red), ash emissions (gray) and block avalanches (blue) reported many times each month. The number of cloudy days (yellow) affected the number of observed events during most months. Data courtesy of IG-EPN, compiled from daily reports.

Table 9. High levels of activity at Reventador during January-September 2017 were evident from the numbers of MODVOLC thermal alerts, and days with reported ash emissions and block avalanches. Cloudy weather impacted observations of activity during most months. Compiled from IG-EPN daily reports, VAAC reports, and MODVOLC data.

Figure 61. MIROVA thermal anomalies for Reventador for the year ending 29 September 2017 show a persistent record of heat flow from the volcano. Significant cloudiness during certain times of the year affected the completeness of the MODIS infrared satellite data on which this is based. Courtesy of MIROVA.

Figure 62. Frequency of daily seismic events at Reventador between 6 January and 14 September 2017. LP: Long Period, EXPL: Explosions, TRESP: Tremors. A significant tremor event took place during the lava flow event of late June, and LP seismic events peaked during the eruptive activity of late August. Courtesy of IG-EPN (Informe Especial del Volcán El Reventador, 2017, N° 4, Continúa la erupción, alternancia de actividad efusiva y explosive, 14 de septiembre del 2017).

Ash emissions occurred many times each month, with the highest plumes exceeding 3,000 m above the summit of the pyroclastic cone inside the caldera. The number of block avalanches reported each month increased steadily throughout the period, with blocks falling hundreds of meters from the summit on all flanks numerous times. Pyroclastic flows were reported a few times most months; the largest event in June sent flows nearly 4 km. Four lava flow events were recorded during the period; on 3 April, a flow traveled 1,600 m down the SW flank, a small flow in early June travelled 200 m down the NE flank, the large flow of 23 June-1 July traveled over 2.5 km down the NE flank, and multiple flows overflowed the summit crater and traveled in five different directions on 24 August 2017.

Activity during January-May 2017. Steam, gas, and ash emissions were reported during 10 of the 12 clear days of January 2017 when observations could be made. The plume heights varied up to 3,000 m above the 3,600-m-altitude summit. Ashfall was reported in El Chaco (30 km SW) on 18 January; nine MODVOLC thermal alerts were reported during the month.

Clearer skies during February 2017 resulted in observations of gas, steam, and ash emissions during 18 days of the month. The plume heights ranged from 900-2,000 m above the summit crater. On 7-8 February, in addition to steam and ash emissions rising 1,500 m and drifting W, block avalanches were observed traveling 1,000-1,500 m down all the flanks. A pyroclastic flow also traveled 800 m down the S flank. On 13 February at 0806 local time, the pilot of a plane from Aerogal observed a vertical plume that reached 2,000 m above the summit; nearby lookouts reported explosion sounds, and slight ashfall was observed in Gonzalo Pizarro in the Sucumbíos province (about 40 km NE). Incandescence appeared at the summit six times in February, triggering 13 MODVOLC thermal alerts.

Ash plume heights in March 2017 ranged from 500-2,000 m during the 18 days they were observed. Although incandescence was seen at the summit seven times, block avalanches were observed on the flanks only twice, on 11 and 23 March, traveling 1,000 m down the flanks each time. A pyroclastic flow traveled 500 m from the summit on 16 March.

Activity increased significantly during April 2017; ash emissions, ranging from 200-2,000 m high were recorded on 21 days, and block avalanches were observed 12 days, traveling 600-1,500 m down the SE flank most of the time. The largest event, on 20 April, sent large blocks 1,800 m down all the flanks. A lava flow moved 1,600 m down the SW flank on 3 April. On 10 April, multiple emissions of steam and gas with moderate ash content reached 2,000 m above the summit crater. On 24 April, a 1,300-m-high ash plume was witnessed during a flyover.

Block avalanches continued at a high rate during May 2017, traveling 500-800 m down all the flanks on at least 10 days of the month. Ash emissions persisted and were observed on 18 of the 25 clear days, rising from 300 to over 800 m. In the early hours of 26 May, a cloud of material was observed on the S flank, likely from a pyroclastic flow.

Activity during June 2017. The technical staff of IG-EPN visited the NE flank of Reventador to monitor activity during 29 May-1 June 2017. They observed a small lava flow on the NE flank, several explosions and emissions associated with both the N and S vents at the summit, pyroclastic flows, 'chugging' (audible, closely spaced intermittent gas emissions), and the projection of ballistic material.

The new lava flow was located on the upper NE flank; the only movement they detected was collapsing of the front of the flow, which sent blocks down to the base of the cone. Explosions with ash emissions from the two vents generally occurred every 15-30 minutes. Gas and ash emissions generally rose 1-2 km high, and the larger explosions produced pyroclastic flows. The sounds of the explosions were audible 5-8 km from the volcano. The researchers used a thermal camera to record a small pyroclastic flow that lasted for about 1 minute and 16 seconds and reached 800 m in length. They also observed avalanche blocks from the S vent that rolled 1,200 m down the flank. The thermal camera measured temperatures as high as 521°C.

During a flyover on 7 June 2017, scientists observed recent pyroclastic flows around all the flanks, the largest ones, on the N and S flanks, reached 1.2 km. Volcanic bombs were visible around the periphery of the crater rim. The lava flow observed a few days earlier by the ground crew extended 200 m down the NNE flank, and did not appear to be associated with either of the summit vents. Several explosions were witnessed from the two vents at the summit crater (figure 63).

Figure 63. Two active vents were visible at the summit crater of the central cone at Reventador on 7 June 2017. Top: Steam and ash emerged from the N vent at the summit crater, and fumarolic activity rose from the NE flank in this view to the NE. Bottom: A lava flow created a pale scar on the NE flank (foreground), while ash and steam emissions rose from the summit crater in this view looking SW. Photos by P Ramón, courtesy of IG-EPN (Informe Especial No. 2-Volcan El Reventador, Observaciones entre 29 de mayo -01 junio y 7 de junio 2017, 26 junio 2017).

Thermal imagery taken during the 7 June overflight revealed three emission centers at the summit; the two vents inside the crater that produced explosions with ash, larger bombs, and pyroclastic flows, and a fissure on the NE flank about 70 m below the summit that produced the lava flow (figure 64). The highest temperatures were measured in the N vent (Vento Norte).

Figure 64. Thermal imagery taken during the overflight of Reventador on 7 June 2017 revealed three emission centers at the summit; the two vents inside the crater (Vento Sur, Vento Norte) produced explosions with ash, larger bombs and pyroclastic flows, and a fissure on the NE flank (fisurales) that produced a small lava flow (flujo de lava). Inset photos show visible image (top right) and thermal image (bottom right) of summit. Courtesy of IG-EPN (Informe Especial No. 2-Volcan El Reventador, Observaciones entre 29 de mayo -01 junio y 7 de junio 2017, 26 junio 2017).

In a special report on 23 June 2017, IG-EPN noted that Reventador had averaged about 50 daily explosions in recent months, as well as a similar number of LP earthquakes. During 22-24 June, a continuous seismic tremor was recorded (figure 62), along with more episodic tremors that included small explosions. Surface activity included pyroclastic flows down all the flanks, and ash plumes that rose about 2.5 km and drifted W. The pyroclastic flows sent material as far as 4 km to the E of the cone, into the headwaters of the El Reventador River (figure 65). IG-EPN reported that the pyroclastic flows generated during this event were the strongest since 2002.

Figure 65. A large pyroclastic flow on 23 June 2017 traveled down the NE flank of Reventador at 0757 local time, as viewed from the Copete webcam on the SE edge of the caldera. Courtesy of IG-EPN (Informe Especial No. 1-Volcan El Reventador, Cambio en la actividad eruptive, 23 junio 2017).

The tremors were associated with a new emission of lava that advanced rapidly down the NE flank of the cone and was active until 1 July. It traveled about 2.65 km before stopping, and was nearly 250 m wide near the base (figure 66). IG-EPN reported that the lava flow was the longest since 2008 and covered and area of just under 0.5 km². In addition to pyroclastic flows and a lava flow, a significant SO₂ plume was released on 24 June 2017 (figure 67). Ash emissions were reported on 22 days during June. Plume heights ranged substantially from less than 200 m to over 2,000 m. Block avalanches traveling up to 800 m down the flanks were reported on ten days, and 20 MODVOLC thermal alerts were issued.

Figure 66. The lava flow and pyroclastic flows of 23 June-1 July 2017 at Reventador were measured in an overflight on 21 July by IG-EPN. dC is the diameter of the summit crater (168 m). The width of the flow was about 120 m partway down the flank, and 246 m at its widest point. It traveled a distance of 2.65 km (F1) from the summit. The pyroclastic flow was measured at 3.95 km (Pf) from the summit. Inset thermal image shows lava flow during the same overflight. Photo by St. Almeida, courtesy of IG-EPN (Erupción de junio de 2017 del volcán El Reventador, Reporte de erupción, volcán El Reventador, 2017-01, Publicado el 19 de septiembre de 2017).

Figure 67. An SO2 plume captured by the OMI instrument on the Aura satellite on 24 June 2017 drifted WNW from Reventador. It coincided in time with an eruptive episode that also produced several pyroclastic flows and a 2.65-km-long lava flow. Courtesy of NASA Goddard Space Flight Center.

Activity during July-September 2017. There were fewer observations of ash emissions during July, on only 17 days, with plume heights ranging from 200-1,500 m (figure 68). Twelve MODVOLC thermal alerts were issued and block avalanches were reported on nine different days moving 200-800 m down all the flanks. A pyroclastic flow reported on 6 July traveled 800 m down the E flank. By the time of the 21 July overflight by IG-EPN, the two summit vents had merged, block avalanches surrounded the rim, and the still-warm flow was visible on the NE flank (figure 69). A visit by IG-EPN scientists on 1 August confirmed the continuing audible explosions, as well as the cooling of the late June lava flow (figure 70).

Figure 68. A dense ash plume rose 1.5 km above the summit crater and drifted N at Reventador during a flyover by IG-EPN on 21 July 2017. Glacier-covered Volcán Cayambe appears in the distance to the NW (right of the ash plume). Courtesy of IG-EPN (Erupción de junio de 2017 del volcán El Reventador, Reporte de erupción, volcán El Reventador, 2017-01, Publicado el 19 de septiembre de 2017).

Figure 69. Thermal and visible images of Reventador on 21 July 2017 reveal a single strong thermal anomaly at the summit, block avalanches and bombs around the rim, and a still warm lava flow on the NE flank, dark brown in the visible image on the right. Photo by Almeida, courtesy of IG-EPN (Erupción de junio de 2017 del volcán El Reventador, 2017-01, Publicado el 19 de septiembre de 2017).

Figure 70. Ash emissions and the cooling lava flow on the NE flank of Reventador on 1 August 2017. Top: An ash-laden emission rose from the summit of the cone; the fresh dark brown lava flow is visible on the lower flank. Bottom: The same image from the thermal camera showed the residual heat from the lava flow (lower right), active heat from the ash emission, and a warm area on the upper flank (upper left), likely from block avalanches or a smaller flow. Photo and Image by M. Almeida, courtesy of IG-EPN (Erupción de junio de 2017 del volcán El Reventador, Reporte de erupción, volcán El Reventador, 2017-01, Publicado el 19 de septiembre de 2017).

The frequency of eruptive activity increased substantially during August 2017. Ash emissions were reported on 29 days of the month most rising over 500 m; block avalanches occurred on at least 25 days sending debris as far as 1,000 m down all the flanks. Pyroclastic flows were reported twice, during 11-12 and 23-24 August (figure 71). Lava flows descended multiple flanks simultaneously on 23 August (figure 72).

Figure 71. A pyroclastic flow descended the SE flank of Reventador during the early morning of 24 August 2017 in this image taken by the IG Copete webcam. Courtesy IG-EPN (Informe del estado del Volcan Reventador No. 236, Jueves, 24 de agosto de 2017).

Figure 72. Lava flows descended multiple flanks of Reventador simultaneously on 23 August 2017 in this infrared image. Five lava flows emerged from both the N and S vents at the summit of the central cone. Ln-1 flowed NE from the N vent and Ln-2 flowed ENE from the N vent. Three flows emerged from the S vent, Ls-1 flowed WSW, Ls-2 flowed ESE, and Ls-3 flowed S. Image by M. Almeida, processing by M.-F. Naranjo, courtesy of IG-EPN (Informe Especial del Volcán El Reventador, 2017, N° 4, Continúa la erupción, alternancia de actividad efusiva y explosive, 14 de septiembre del 2017).

The Washington VAAC issued 114 aviation alerts during August 2017 and 123 during September, indicating a continued level of high eruptive activity; plume heights were reported as high as 3,500 m above the summit, and block avalanches covered most of the upper cone down to 900 m a number of times during both months (figure 73).

Figure 73. Explosions with rolling incandescent blocks descend 900 m on all sides of Reventador on 11 September 2017 in this image from the Copete webcam. Courtesy of IG-EPN (Informe Especial del Volcán El Reventador, 2017, N° 4, Continúa la erupción, alternancia de actividad efusiva y explosive, 14 de septiembre del 2017).

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

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

In 2016 and the first quarter of 2017, activity at Semeru was characterized by numerous ash explosions and thermal anomalies (BGVN 42:05). Thermal anomalies became consistent after mid-May 2017, increasing over the next few months and continuing through December 2017. The information below comes from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as the Center for Volcanology and Geological Hazard Mitigation, or CVGHM), the Darwin Volcanic Ash Advisor Center (VAAC), and MODIS thermal sensors aboard satellites. The Alert Level since February 2012 has remained at Yellow (Waspada, or Alert).

According to PVMBG monthly reports, Semeru did not show any change of activity during the reporting period. Presumably, this included numerous ash explosions and thermal anomalies indicating the presence of lava flows or dome growth. A Darwin VAAC ash advisory stated that an ash explosion on 7 June at 0020 UTC generated a plume that rose 4 km in altitude and drifted 13 km SW a day later.

Thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm, were not observed between 19 November 2016 and 6 June 2017. On 6 June, a single hotspot was recorded, coincident with the ash explosion. The next hotspot occurred on 2 August, followed by anomalous pixels on three additional days through 13 August, but none during the rest of August. The number rose to 7-12 days per month during September-December, many of which were multi-pixel events.

The MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected only two distinct MODIS hotspots during April through the middle of May 2017. After mid-May, the number rose dramatically and every month through December numerous hotspots were detected, almost all within 5 km of the volcano.

Figure 31. MODIS satellite thermal anomaly data at Semeru analyzed by the MIROVA system for the year ending 8 January 2018. Courtesy of MIROVA.

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

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

In discussing the week ending on 12 September, "Earthweek" (Newman, 1997) incorrectly claimed that a volcano named "Mount Pinukis" had erupted. Widely read in the US, the dramatic Earthweek report described terrified farmers and a black mushroom cloud that resembled a nuclear explosion. The mountain's location was given as "200 km E of Zamboanga City," a spot well into the sea. The purported eruption had received mention in a Manila Bulletin newspaper report nine days earlier, on 4 September. Their comparatively understated report said that a local police director had disclosed that residents had seen a dormant volcano showing signs of activity.

In response to these news reports Emmanuel Ramos of the Philippine Institute of Volcanology and Seismology (PHIVOLCS) sent a reply on 17 September. PHIVOLCS staff had initially heard that there were some 12 alleged families who fled the mountain and sought shelter in the lowlands. A PHIVOLCS investigation team later found that the reported "families" were actually individuals seeking respite from some politically motivated harassment. The story seems to have stemmed from a local gold rush and an influential politician who wanted to use volcanism as a ploy to exclude residents. PHIVOLCS concluded that no volcanic activity had occurred. They also added that this finding disappointed local politicians but was much welcomed by the residents.

PHIVOLCS spelled the mountain's name as "Pinokis" and from their report it seems that it might be an inactive volcano. There is no known Holocene volcano with a similar name (Simkin and Siebert, 1994). No similar names (Pinokis, Pinukis, Pinakis, etc.) were found listed in the National Imagery and Mapping Agency GEOnet Names Server (http://geonames.nga.mil/gns/html/index.html), a searchable database of 3.3 million non-US geographic-feature names.

The Manila Bulletin report suggested that Pinokis resides on the Zamboanga Peninsula. The Peninsula lies on Mindanao Island's extreme W side where it bounds the Moro Gulf, an arm of the Celebes Sea. The mountainous Peninsula trends NNE-SSW and contains peaks with summit elevations near 1,300 m. Zamboanga City sits at the extreme end of the Peninsula and operates both a major seaport and an international airport.

[Later investigation found that Mt. Pinokis is located in the Lison Valley on the Zamboanga Peninsula, about 170 km NE of Zamboanga City and 30 km NW of Pagadian City. It is adjacent to the two peaks of the Susong Dalaga (Maiden's Breast) and near Mt. Sugarloaf.]

References. Newman, S., 1997, Earthweek, a diary of the planet (week ending 12 September): syndicated newspaper column (URL: http://www.earthweek.com/).

Manila Bulletin, 4 Sept. 1997, Dante's Peak (URL: http://www.mb.com.ph/).

Simkin, T., and Siebert, L., 1994, Volcanoes of the world, 2nd edition: Geoscience Press in association with the Smithsonian Institution Global Volcanism Program, Tucson AZ, 368 p.

Information Contacts: Emmanuel G. Ramos, Deputy Director, Philippine Institute of Volcanology and Seismology, Department of Science and Technology, PHIVOLCS Building, C. P. Garcia Ave., University of the Philippines, Diliman campus, Quezon City, Philippines.

Xinhua News Agency filed a news report on 27 February under the headline "Volcano erupts in Somalia" but the veracity of the story now appears doubtful. The report disclosed the volcano's location as on the W side of the Gedo region, an area along the Ethiopian border just NE of Kenya. The report had relied on the commissioner of the town of Bohol Garas (a settlement described as 40 km NE of the main Al-Itihad headquarters of Luq town) and some or all of the information was relayed by journalists through VHF radio. The report claimed the disaster "wounded six herdsmen" and "claimed the lives of 290 goats grazing near the mountain when the incident took place." Further descriptions included such statements as "the volcano which erupted two days ago [25 February] has melted down the rocks and sand and spread . . . ."

Giday WoldeGabriel returned from three weeks of geological fieldwork in SW Ethiopia, near the Kenyan border, on 25 August. During his time there he inquired of many people, including geologists, if they had heard of a Somalian eruption in the Gedo area; no one had heard of the event. WoldeGabriel stated that he felt the news report could have described an old mine or bomb exploding. Heavy fighting took place in the Gedo region during the Ethio-Somalian war of 1977. Somalia lacks an embassy in Washington DC; when asked during late August, Ayalaw Yiman, an Ethiopian embassy staff member in Washington DC also lacked any knowledge of a Somalian eruption.

A Somalian eruption would be significant since the closest known Holocene volcanoes occur in the central Ethiopian segment of the East African rift system S of Addis Ababa, ~500 km NW of the Gedo area. These Ethiopian rift volcanoes include volcanic fields, shield volcanoes, cinder cones, and stratovolcanoes.

Information Contacts: Xinhua News Agency, 5 Sharp Street West, Wanchai, Hong Kong; Giday WoldeGabriel, EES-1/MS D462, Geology-Geochemistry Group, Los Alamos National Laboratory, Los Alamos, NM 87545; Ayalaw Yiman, Ethiopian Embassy, 2134 Kalorama Rd. NW, Washington DC 20008.

Following the Ms 7.8 earthquake in Turkey on 17 August (BGVN 24:08) an Email message originating in Turkey was circulated, claiming that volcanic activity was observed coincident with the earthquake and suggesting a new (magmatic) volcano in the Sea of Marmara. For reasons outlined below, and in the absence of further evidence, editors of the Bulletin consider this a false report.

The report stated that fishermen near the village of Cinarcik, at the E end of the Sea of Marmara "saw the sea turned red with fireballs" shortly after the onset of the earthquake. They later found dead fish that appeared "fried." Their nets were "burned" while under water and contained samples of rocks alleged to look "magmatic."

No samples of the fish were preserved. A tectonic scientist in Istanbul speculated that hot water released by the earthquake from the many hot springs along the coast in that area may have killed some fish (although they would be boiled rather than fried).

The phenomenon called earthquake lights could explain the "fireballs" reportedly seen by the fishermen. Such effects have been reasonably established associated with large earthquakes, although their origin remains poorly understood. In addition to deformation-triggered piezoelectric effects, earthquake lights have sometimes been explained as due to the release of methane gas in areas of mass wasting (even under water). Omlin and others (1999), for example, found gas hydrate and methane releases associated with mud volcanoes in coastal submarine environments.

The astronomer and author Thomas Gold (Gold, 1998) has a website (Gold, 2000) where he presents a series of alleged quotes from witnesses of earthquakes. We include three such quotes here (along with Gold's dates, attributions, and other comments):

(A) Lima, 30 March 1828. "Water in the bay 'hissed as if hot iron was immersed in it,' bubbles and dead fish rose to the surface, and the anchor chain of HMS Volage was partially fused while lying in the mud on the bottom." (Attributed to Bagnold, 1829; the anchor chain is reported to be on display in the London Navy Museum.)

(B) Romania, 10 November 1940. ". . . a thick layer like a translucid gas above the surface of the soil . . . irregular gas fires . . . flames in rhythm with the movements of the soil . . . flashes like lightning from the floor to the summit of Mt Tampa . . . flames issuing from rocks, which crumbled, with flashes also issuing from non-wooded mountainsides." (Phrases used in eyewitness accounts collected by Demetrescu and Petrescu, 1941).

(C) Sungpan-Pingwu (China), 16, 22, and 23 August 1976. "From March of 1976, various large anomalies were observed over a broad region. . . . At the Wanchia commune of Chungching County, outbursts of natural gas from rock fissures ignited and were difficult to extinguish even by dumping dirt over the fissures. . . . Chu Chieh Cho, of the Provincial Seismological Bureau, related personally seeing a fireball 75 km from the epicenter on the night of 21 July while in the company of three professional seismologists."

Yalciner and others (1999) made a study of coastal areas along the Sea of Marmara after the Izmet earthquake. They found evidence for one or more tsunamis with maximum runups of 2.0-2.5 m. Preliminary modeling of the earthquake's response failed to reproduce the observed runups; the areas of maximum runup instead appeared to correspond most closely with several local mass-failure events. This observation together with the magnitude of the earthquake, and bottom soundings from marine geophysical teams, suggested mass wasting may have been fairly common on the floor of the Sea of Marmara.

Despite a wide range of poorly understood, dramatic processes associated with earthquakes (Izmet 1999 apparently included), there remains little evidence for volcanism around the time of the earthquake. The nearest Holocene volcano lies ~200 km SW of the report location. Neither Turkish geologists nor scientists from other countries in Turkey to study the 17 August earthquake reported any volcanism. The report said the fisherman found "magmatic" rocks; it is unlikely they would be familiar with this term.

The motivation and credibility of the report's originator, Erol Erkmen, are unknown. Certainly, the difficulty in translating from Turkish to English may have caused some problems in understanding. Erkmen is associated with a website devoted to reporting UFO activity in Turkey. Photographs of a "magmatic rock" sample were sent to the Bulletin, but they only showed dark rocks photographed devoid of a scale on a featureless background. The rocks shown did not appear to be vesicular or glassy. What was most significant to Bulletin editors was the report author's progressive reluctance to provide samples or encourage follow-up investigation with local scientists. Without the collaboration of trained scientists on the scene this report cannot be validated.

References. Omlin, A, Damm, E., Mienert, J., and Lukas, D., 1999, In-situ detection of methane releases adjacent to gas hydrate fields on the Norwegian margin: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Yalciner, A.C., Borrero, J., Kukano, U., Watts, P., Synolakis, C. E., and Imamura, F., 1999, Field survey of 1999 Izmit tsunami and modeling effort of new tsunami generation mechanism: (Abstract) Fall AGU meeting 1999, Eos, American Geophysical Union.

Gold, T., 1998, The deep hot biosphere: Springer Verlag, 256 p., ISBN: 0387985468.

Gold, T., 2000, Eye-witness accounts of several major earthquakes (URL: http://www.people.cornell.edu/ pages/tg21/eyewit.html).

Information Contacts: Erol Erkmen, Tuvpo Project Alp.

In December 2002 information appeared in Mongolian and Russian newspapers and on national TV that a volcano in Central Mongolia, the Har-Togoo volcano, was producing white vapors and constant acoustic noise. Because of the potential hazard posed to two nearby settlements, mainly with regard to potential blocking of rivers, the Director of the Research Center of Astronomy and Geophysics of the Mongolian Academy of Sciences, Dr. Bekhtur, organized a scientific expedition to the volcano on 19-20 March 2003. The scientific team also included M. Ulziibat, seismologist from the same Research Center, M. Ganzorig, the Director of the Institute of Informatics, and A. Ivanov from the Institute of the Earth's Crust, Siberian Branch of the Russian Academy of Sciences.

Geological setting. The Miocene Har-Togoo shield volcano is situated on top of a vast volcanic plateau (figure 1). The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Pliocene and Quaternary volcanic rocks are also abundant in the vicinity of the Holocene volcanoes (Devyatkin and Smelov, 1979; Logatchev and others, 1982). Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Figure 1. Photograph of the Har-Togoo volcano viewed from west, March 2003. Courtesy of Alexei Ivanov.

Observations during March 2003. The name of the volcano in the Mongolian language means "black-pot" and through questioning of the local inhabitants, it was learned that there is a local myth that a dragon lived in the volcano. The local inhabitants also mentioned that marmots, previously abundant in the area, began to migrate westwards five years ago; they are now practically absent from the area.

Acoustic noise and venting of colorless warm gas from a small hole near the summit were noticed in October 2002 by local residents. In December 2002, while snow lay on the ground, the hole was clearly visible to local visitors, and a second hole could be seen a few meters away; it is unclear whether or not white vapors were noticed on this occasion. During the inspection in March 2003 a third hole was seen. The second hole is located within a 3 x 3 m outcrop of cinder and pumice (figure 2) whereas the first and the third holes are located within massive basalts. When close to the holes, constant noise resembled a rapid river heard from afar. The second hole was covered with plastic sheeting fixed at the margins, but the plastic was blown off within 2-3 seconds. Gas from the second hole was sampled in a mechanically pumped glass sampler. Analysis by gas chromatography, performed a week later at the Institute of the Earth's Crust, showed that nitrogen and atmospheric air were the major constituents.

Figure 2. Photograph of the second hole sampled at Har-Togoo, with hammer for scale, March 2003. Courtesy of Alexei Ivanov.

The temperature of the gas at the first, second, and third holes was +1.1, +1.4, and +2.7°C, respectively, while air temperature was -4.6 to -4.7°C (measured on 19 March 2003). Repeated measurements of the temperatures on the next day gave values of +1.1, +0.8, and -6.0°C at the first, second, and third holes, respectively. Air temperature was -9.4°C. To avoid bias due to direct heating from sunlight the measurements were performed under shadow. All measurements were done with Chechtemp2 digital thermometer with precision of ± 0.1°C and accuracy ± 0.3°C.

Inside the mouth of the first hole was 4-10-cm-thick ice with suspended gas bubbles (figure 5). The ice and snow were sampled in plastic bottles, melted, and tested for pH and Eh with digital meters. The pH-meter was calibrated by Horiba Ltd (Kyoto, Japan) standard solutions 4 and 7. Water from melted ice appeared to be slightly acidic (pH 6.52) in comparison to water of melted snow (pH 7.04). Both pH values were within neutral solution values. No prominent difference in Eh (108 and 117 for ice and snow, respectively) was revealed.

Two digital short-period three-component stations were installed on top of Har-Togoo, one 50 m from the degassing holes and one in a remote area on basement rocks, for monitoring during 19-20 March 2003. Every hour 1-3 microseismic events with magnitude <2 were recorded. All seismic events were virtually identical and resembled A-type volcano-tectonic earthquakes (figure 6). Arrival difference between S and P waves were around 0.06-0.3 seconds for the Har-Togoo station and 0.1-1.5 seconds for the remote station. Assuming that the Har-Togoo station was located in the epicentral zone, the events were located at ~1-3 km depth. Seismic episodes similar to volcanic tremors were also recorded (figure 3).

Figure 3. Examples of an A-type volcano-tectonic earthquake and volcanic tremor episodes recorded at the Har-Togoo station on 19 March 2003. Courtesy of Alexei Ivanov.

Conclusions. The abnormal thermal and seismic activities could be the result of either hydrothermal or volcanic processes. This activity could have started in the fall of 2002 when they were directly observed for the first time, or possibly up to five years earlier when marmots started migrating from the area. Further studies are planned to investigate the cause of the fumarolic and seismic activities.

At the end of a second visit in early July, gas venting had stopped, but seismicity was continuing. In August there will be a workshop on Russian-Mongolian cooperation between Institutions of the Russian and Mongolian Academies of Sciences (held in Ulan-Bator, Mongolia), where the work being done on this volcano will be presented.

References. Devyatkin, E.V. and Smelov, S.B., 1979, Position of basalts in sequence of Cenozoic sediments of Mongolia: Izvestiya USSR Academy of Sciences, geological series, no. 1, p. 16-29. (In Russian).

Logatchev, N.A., Devyatkin, E.V., Malaeva, E.M., and others, 1982, Cenozoic deposits of Taryat basin and Chulutu river valley (Central Hangai): Izvestiya USSR Academy of Sciences, geological series, no. 8, p. 76-86. (In Russian).

Geologic Background. The Miocene Har-Togoo shield volcano, also known as Togoo Tologoy, is situated on top of a vast volcanic plateau. The 5,000-year-old Khorog (Horog) cone in the Taryatu-Chulutu volcanic field is located 135 km SW and the Quaternary Urun-Dush cone in the Khanuy Gol (Hanuy Gol) volcanic field is 95 km ENE. Analysis of seismic activity recorded by a network of seismic stations across Mongolia shows that earthquakes of magnitude 2-3.5 are scattered around the Har-Togoo volcano at a distance of 10-15 km.

Information Contacts: Alexei V. Ivanov, Institute of the Earth Crust SB, Russian Academy of Sciences, Irkutsk, Russia; Bekhtur andM. Ulziibat, Research Center of Astronomy and Geophysics, Mongolian Academy of Sciences, Ulan-Bator, Mongolia; M. Ganzorig, Institute of Informatics MAS, Ulan-Bator, Mongolia.

An eruption at Mount Elgon was mistakenly inferred when fumes escaped from this otherwise quiet volcano. The fumes were eventually traced to dung burning in a lava-tube cave. The cave is home to, or visited by, wildlife ranging from bats to elephants. Mt. Elgon (Ol Doinyo Ilgoon) is a stratovolcano on the SW margin of a 13 x 16 km caldera that straddles the Uganda-Kenya border 140 km NE of the N shore of Lake Victoria. No eruptions are known in the historical record or in the Holocene.

On 7 September 2004 the web site of the Kenyan newspaper The Daily Nation reported that villagers sighted and smelled noxious fumes from a cave on the flank of Mt. Elgon during August 2005. The villagers' concerns were taken quite seriously by both nations, to the extent that evacuation of nearby villages was considered.

The Daily Nation article added that shortly after the villagers' reports, Moses Masibo, Kenya's Western Province geology officer visited the cave, confirmed the villagers observations, and added that the temperature in the cave was 170°C. He recommended that nearby villagers move to safer locations. Masibo and Silas Simiyu of KenGens geothermal department collected ashes from the cave for testing.

Gerald Ernst reported on 19 September 2004 that he spoke with two local geologists involved with the Elgon crisis from the Geology Department of the University of Nairobi (Jiromo campus): Professor Nyambok and Zacharia Kuria (the former is a senior scientist who was unable to go in the field; the latter is a junior scientist who visited the site). According to Ernst their interpretation is that somebody set fire to bat guano in one of the caves. The fire was intense and probably explains the vigorous fuming, high temperatures, and suffocated animals. The event was also accompanied by emissions of gases with an ammonia odor. Ernst noted that this was not surprising considering the high nitrogen content of guano—ammonia is highly toxic and can also explain the animal deaths. The intense fumes initially caused substantial panic in the area.

It was Ernst's understanding that the authorities ordered evacuations while awaiting a report from local scientists, but that people returned before the report reached the authorities. The fire presumably prompted the response of local authorities who then urged the University geologists to analyze the situation. By the time geologists arrived, the fuming had ceased, or nearly so. The residue left by the fire and other observations led them to conclude that nothing remotely related to a volcanic eruption had occurred.

However, the incident emphasized the problem due to lack of a seismic station to monitor tectonic activity related to a local triple junction associated with the rift valley or volcanic seismicity. In response, one seismic station was moved from S Kenya to the area of Mt. Elgon so that local seismicity can be monitored in the future.

Information Contacts: Gerald Ernst, Univ. of Ghent, Krijgslaan 281/S8, B-9000, Belgium; Chris Newhall, USGS, Univ. of Washington, Dept. of Earth & Space Sciences, Box 351310, Seattle, WA 98195-1310, USA; The Daily Nation (URL: http://www.nationmedia.com/dailynation/); Uganda Tourist Board (URL: http://www.visituganda.com/).