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/).

[Agua de Pau information only; extracted from a summary of significant seismic activity in the E Azores (figure 1) since May 1988.]

Figure 1. Sketch map showing islands in the eastern Azores. Approximate epicenters of the 3-5 October 1988 swarm at the submarine volcano Don Joao de Castro Bank (4) and the 21 November 1988 and 21 January 1989 earthquakes in the Hirondelle Basin (6 and 7) are shown. Courtesy of R. Moore.

"A swarm of microearthquakes, accompanied by weak harmonic tremor, occurred beneath the NE flank of Agua de Pau Volcano on Sao Miguel (figure 2, zone 1) 23-24 May 1988. Seismometers recorded 383 earthquakes; the largest had intensities of MM IV-V in villages along the N coast. A similar but smaller swarm occurred in the same area in 1983 and was recorded by USGS seismographs. Numerous, small, normal faults (including some that show scissor-type movement) displace basaltic, tristanitic, and trachytic vent deposits and flows in this area. However, the area has had no eruptions for about 3,000 years and is the least active of the five volcanic zones on Sao Miguel that have erupted during Holocene time.

Figure 2. Approximate epicenters for earthquakes on and near the island of Sao Miguel, May-October, 1988. Courtesy of R. Moore.

"A small swarm of microearthquakes occurred 24-26 June [1988] on the S flank of Agua de Pau Volcano (zone 2). Sixty-four earthquakes were recorded; the largest had intensities of MM III-IV in nearby villages. No tremor accompanied this episode.

"A small swarm of microearthquakes occurred 6 July [1988] near the S coast of Sao Miguel (zone 3). Fifty-one earthquakes were recorded; the largest was felt and had an intensity of MM III-IV. No tremor accompanied this episode.

Geologic Background. The Agua de Pau stratovolcano in central Sao Miguel Island contains an outer 4 x 7 km caldera formed about 30,000-45,000 years ago and an inner 2.5 x 3 km caldera that was created about 15,000 years ago. The younger caldera is partially filled by the Lagoa do Fogo caldera lake. Several post-caldera lava domes were emplaced on the northern and western flanks, but activity in the caldera did not resume until about 5000 years ago. The 3-km3 Fogo-A plinian pumice-fall deposit, the product of the largest-known Holocene eruption in the Azores, was emplaced at this time. Numerous flank cinder cones mark radial and concentric fissures, some of which have been active during historical time. The latest trachytic explosive eruption took place during 1563. Prominent hot springs are located on the NW flank.

Information Contacts: A. Rodrigues da Silva, Consorcio Geotermico de S. Miguel; R. Moore, USGS; National Institute of Meteorology and Geophysics, Portugal.

In March, activity remained weak, with a small amount of ash emission on the 1st. Only one explosion . . . was recorded, bringing the year's total to five. The explosion, at 2258 on 11 March, ejected a 1,500-m plume and was accompanied by an air shock and small explosion sound. No damage was reported. Monthly ash accumulation at KLMO was 116 g/m². An earthquake swarm was recorded 14-15 March by a seismometer 2.3 km NW of the crater.

Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Information Contacts: JMA.

About 3,000 volcanic tremor episodes were recorded during March, twice the number recorded in January and February (figure 9). A significant increase was recorded 22 March on a seismometer 0.8 km W of Crater 1. The amplitude of continuous tremor was generally unchanged.

Figure 9. Monthly number of isolated volcanic tremor episodes at Aso (top), earthquakes (bars, bottom), and maximum plume heights (curve, bottom), 1966-March 1989. Arrows mark periods of explosions. Courtesy of JMA.

Early 5 April, ash was ejected to ~50 m above a vent ~100 m below the crater rim. A field survey at 1140 the next day revealed that ash emission had stopped. A 1-km area (the smallest of three designated zones) around the crater was closed to tourists by the Aso Disaster Prevention Authority, at 0920 on 5 March. Such a restriction is necessary a few times a year when activity increases.

On 12 April, the restricted zone was reopened. Ash had not been ejected since 6 April although the frequency of tremor episodes remained high at 200/day. Glow at vents and cracks on the crater floor was regularly observed during night visits from October 1988 through April 1989.

Geologic Background. The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 CE. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

Information Contacts: JMA.

Lidar data has continued to show gradual declines in stratospheric aerosols (figure 65). Aerosol concentrations over Obninsk, USSR were more variable than from other sites during summer 1988, but generally declined from April-June values. No large explosive eruptions have been reported in recent months and no fresh aerosol layers have been observed.

Figure 65. Lidar data from various locations, showing altitudes of aerosol layers during July 1988-March 1989. Note that some layers have multiple peaks. Backscattering ratios from Obninsk are for the Nd-YAG wavelength of 0.53 µm; all others are for the ruby wavelength of 0.69 µm. Integrated values show total backscatter, expressed in steradians-1, integrated over 500-m intervals from 15-30 km at Obninsk; and 300-m intervals from 16-33 km at Mauna Loa and from the tropopause to 30 km at Hampton, Virginia.

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

Information Contacts: Sergei Khmelevtsov, Institute of Experimental Meteorology, Lenin St. 82, Obninsk, Kaluga Reg., USSR; Thomas DeFoor, Mauna Loa Observatory, P. O. Box 275, Hilo, HI 96720 USA; Horst Jäger, Fraunhofer-Institut für Atmosphärische Umweltforschung, Kreuzeckbahnstrasse 19, D-8100 Garmisch-Partenkirchen, West Germany; Mary Osborn, NASA Langley Research Center, Hampton, VA 23665 USA.

Spanish and Argentine scientists visited Deception Island in December 1988 and January-February 1989. Local and regional seismicity, thermal activity, gas emission, magnetic field, geodetic, and geological studies were carried out, and the Spanish oceanographic vessel Las Palmas operated in the area. Previous work at Deception by the Vulcantar project was during the austral summers of 1986-87 and 1987-88.

During the 1988-89 field season, an array of six seismic stations was installed on Deception Island, plus a single instrument at Spain's Juan Carlos I facility on Livingston Island (figure 1). More than 2,000 events were monitored, with more than 1,000 digitally recorded. The distribution of events showed a good correlation with tectonic features on and near the island. Seismic swarms and episodes of volcanic tremor with well-defined frequencies and durations of 5-360 minutes were also recorded. Small changes were observed in the distribution of fumarolic activity and thermal fields, with some impact on the local fauna.

Figure 1. Distribution of seismic events in the vicinity of Deception Island, austral summer 1988-89 (top). Best-located seismic events near Deception Island during the same period (middle); new land built by the 1970 eruption is shaded. The inset box indicates the area shown in the map below. Detail of the Fumarole Bay area (bottom) showing seismic events 1-31 January 1989 (circles), sites of fumarolic activity (asterisks), and seismic stations (triangles). Courtesy of Ramón Ortiz.

Geologic Background. Ring-shaped Deception Island, one of Antarctica's most well known volcanoes, contains a 7-km-wide caldera flooded by the sea. Deception Island is located at the SW end of the Shetland Islands, NE of Graham Land Peninsula, and was constructed along the axis of the Bransfield Rift spreading center. A narrow passageway named Neptunes Bellows provides entrance to a natural harbor that was utilized as an Antarctic whaling station. Numerous vents located along ring fractures circling the low, 14-km-wide island have been active during historical time. Maars line the shores of 190-m-deep Port Foster, the caldera bay. Among the largest of these maars is 1-km-wide Whalers Bay, at the entrance to the harbor. Eruptions from Deception Island during the past 8700 years have been dated from ash layers in lake sediments on the Antarctic Peninsula and neighboring islands.

Information Contacts: R. Ortiz, Museo Nacional de Ciencias Naturales, Spain; J. Sastre, Real Instituto y Observatorio de la Armada, Spain; C. Parica, Ciudad Universitaria, Buenos Aires, Argentina; J. Viramonte, Univ Nacional de Salta, Argentina.

[Don João de Castro Bank information only; extracted from a summary of significant seismic activity in the E Azores since May 1988.]

"A small swarm of earthquakes occurred within the volcano Don João de Castro Bank (figure 1, zone 4) 3-5 October. Sixty-two earthquakes were recorded; no harmonic tremor was detected. A felt earthquake occurred in the same area 23 October; it had intensities of MM IV-V on Terceira and MM III-IV on the N coast of Sao Miguel."

Figure 1. Sketch map showing islands in the eastern Azores. Approximate epicenters of the 3-5 October 1988 swarm at the submarine volcano Don Joao de Castro Bank (4) and the 21 November 1988 and 21 January 1989 earthquakes in the Hirondelle Basin (6 and 7) are shown. Courtesy of R. Moore.

Geologic Background. Don Joao de Castro Bank is a large submarine volcano that rises to within 13 m of the sea surface roughly halfway between Terceira and San Miguel Islands. Pillow lavas form the base of the volcano, which is capped by basaltic hyaloclastites. A submarine eruption during December 1720 produced an ephemeral island that attained a length of 1.5 km and an altitude of about 250 m before it was eroded beneath the sea surface two years later. The volcano (also spelled Dom Joao de Castro) was named after the Portuguese hydrographic survey vessel that surveyed the bank in 1941. Two youthful parasitic craters, one tephra covered and the other sediment free, are located on the NW flank. The submarine volcano has an impressive shallow fumarole field and remains seismically active.

Information Contacts: A. Rodrigues da Silva, Consorcio Geotermico de S. Miguel; R. Moore, USGS; National Institute of Meteorology and Geophysics, Portugal.

Most of the following is from a draft report by Hector Cepeda and others.

Eruptive activity. Increased fumarolic activity accompanied by minor ash emission and seismicity began in mid-February. A summit-area explosion was felt on 19 February before 1700. Weather over the cone cleared at 1700, and strong fumarolic activity from one of the secondary craters was visible from the army/police communications station on the edge of the caldera. The height of the column varied between 100 and 200 m. This information triggered the mobilization of the Comité Regional de Emergencia de Nariño (CREN) which requested help from higher authorities.

During a 25 February summit climb, a column of water vapor, sulfur compounds, and sulfuric acid was being vigorously emitted from a vent (named El Pinta) immediately E of the main crater. The area around the active crater was covered by recently ejected pyroclastic material, consisting of very fine, gray, wet ash and lithic fragments of centimeters (occasionally to tens of centimeters) in size. No fresh magma was found in the tephra.

Before 19 February, El Pinta crater had shown no fumarolic activity. After the onset of activity, the crater was elongate N-S, with horizontal dimensions of 40 x 25 m and a depth of >30 m. A chain of small fumaroles within the crater emitted gases at high pressure and had deposited sulfur. Resonance effects produced a sound like a jet aircraft. Fumarolic activity at other vents had also increased substantially.

As activity continued, ejecta from El Pinta were dispersed nearly 1 km to the WSW. Maximum tephra thicknesses were ~5 cm within 5 m of the crater rim (apparently by the 20 March report date). Impacts of the largest blocks left visible marks. The direction in which pyroclastics had been ejected by the phreatic activity and the behavior of the gas jet suggested that the conduit of El Pinta was inclined to the E.

On 12 March, the staff of the nearby police post reported that another old secondary crater (El Peladito) had reopened on the edge of the main crater, 50 m S of El Pinta. This crater did not show any fumarolic activity. A pre-1964 collapse of the wall that formerly separated it from the main crater left it perched on the main crater's inner wall. The bottom of El Peladito was not visible, but was more than 50 m below the main crater's rim.

Ash was emitted for 4 hours on 27 March, lightly dusting Pasto, at the E foot of the volcano. A tremor-like signal accompanied the ash emission, without a precursory swarm or eruption earthquakes. In response, INGEOMINAS elevated the alert level from "watchfulness" to "white." A strong swarm on 5 April at 1000 prompted an increase to "yellow" alert [see also 14:04], which had not changed as of 12 April. The Nariño seismograph, 5 km from the crater, was saturated by 6-7 of the earthquakes, but no ash was emitted.

Two small lakes were present in the summit complex, one (La Trucha) between the base of the active cone and the smaller caldera, the second (Rafa) in the bottom of the main crater. Levels of these lakes were higher than usual because of the recent unusually heavy rains, and geologists suggested that the additional water in the volcano's hydrothermal system may have influenced its activity.

Since 1988, INGEOMINAS and the Univ Nacional (Manizales campus) have monitored several fumaroles at Galeras, measuring H₂S, SO₂, HCl, CO₂, and total S. Only small temperature increases were noted, reaching roughly 10°C at one fumarole (Calvache) on the NNE flank of the active cone, which had a temperature of 100.6°C on 15 March. COSPEC measurements on 19 and 20 March yielded values of only 30 and 40 t/d.

Deformation. Baseline deformation data was limited to routine geodetic work by the Instituto Geográfico Agustín Codazzi. A series of proposed level lines and dry tilt stations have been identified, and initial measurements were made 2 March on the upper E flank. Remeasurements since then have identified no changes that exceeded instrumental error.

Seismicity. A WWSSN seismic station ~5 km SE of the crater has been collecting data for ~15 years. At the request of the CREN and the Oficina Nacional para la Atención de Desastres, personnel from the Observatorio Vulcanológico de Colombia installed three additional seismic stations on the volcano on 28 February. Early February seismicity had consisted of low-frequency, small magnitude (M < 0.5) events, at rates of no more than 10/day. The newly installed seismic net recorded a gradual increase in the number of events/day, mostly B-types (see figure 1). Energy release generally remained low, with most events of M<1, although high-frequency shocks on 17 and 20 March reached magnitudes of 1.5 and 2.2.

A small number of A-type events were recorded. Very shallow focal depths were indicated by the small separations between P- and S-wave arrivals at stations (Crater 1 and 2) 0.5 and 1 km from the active vent, and attenuation was strong (at Nariño 1) 5.5 km away. Many of the shallow high-frequency events were preceded by small bursts of signals characteristic of gas emission. A very few (4 or 5) high-frequency events from a different source were detected, with S-P of 1.5 seconds at Crater 1 station. These decreased after 8 March, and seismicity was dominated by low-frequency events. Long-period events were a little less numerous but of about the same magnitude as the high-frequency shocks. These were also believed to be very shallow and were greatly attenuated at Nariño 1. No felt shocks were reported until 20 March at 0033 when persons in the Telecom communications station 1 km from the crater noticed an A-type event.

A signal similar to spasmodic tremor began to be observed on 8 February, and the next day there were a series of events that looked like long-period seismicity. Tremor was clearer after 8 March, in brief pulses that had a more spasmodic than harmonic character. Energy was relatively low, although amplitudes occasionally reached moderate to high levels near the source of the seismicity (on stations Crater 1 and 2). The predominant frequency was 4-5 Hz, with some 2-Hz components. The most conspicuous pulse occurred on 11 March at 1803, possibly related to the reopening of El Peladito crater, reported 12 March (see above). Low-frequency events and the short pulses of tremor could be correlated with small changes in fumarolic activity.

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: H. Cepeda and B. Pulgarin, INGEOMINAS, Popayán; F. Muñoz, A. Acevedo, F. Gil, A. Nieto, M. Calvache, H. Mora, and C. Carvajal, INGEOMINAS, Manizales; A. Londoño, Univ Nacional, Manizales; I. Mejía, INGEOMINAS, Medellín; N. Banks, J. Ewert, and M. Doukas, USGS.

During a 14 January overflight, a group of highly active fumaroles was noted on the N slope of Pallas Peak's S cone, on the E margin of Ketoi caldera.

Geologic Background. The circular, 10-km-wide Ketoi island, which rises across the 19-km-wide Diana Strait from Simushir Island, hosts of one of the most complex volcanic structures of the Kuril Islands. The rim of a 5-km-wide Pleistocene caldera is exposed only on the NE side. A younger 1172-m-high stratovolcano forming the NW part of the island is cut by a horst-and-graben structure containing two solfatara fields. A 1.5-km-wide freshwater lake fills an explosion crater in the center of the island. Pallas Peak, a large andesitic cone in the NE part of the caldera, is truncated by a 550-m-wide crater containing a brilliantly colored turquoise crater lake. Lava flows from Pallas Peak overtop the caldera rim and descend nearly 5 km to the SE coast. The first historical eruption of Pallas Peak, during 1843-46, was its largest.

Information Contacts: G. Steinberg, Yuzhno-Sakhalinsk.

The level of the lava pond in Kupaianaha vent . . . varied from 21 to 25 m below the rim during March (figure 57). Lava breakouts from the tube system were relatively frequent near the major fault scarp at ~270-360 m elevation. Lava that emerged from the W tube system advanced to 150 m elevation, flowed ~120 m into forest, and passed near the Royal Gardens subdivision, causing no damage. Sporadic breakouts from the E tube produced sluggish pahoehoe flows. Lava advanced to the point where a December 1986 flow had . . . entered the Kalapana Gardens subdivision. Breakouts from the central tube had advanced down the E side of the flow field to 45 m elevation by the end of the month, but remained on top of older flows.

Figure 57. The lava pond at Kupaianaha vent on Kilauea's East rift zone. In this photograph by J. Griggs (USGS), the lava is mostly covered with crust and is about 15 m below the rim of the pond. The pond is ~100 m across at its widest point. The entrance to the main lava tube (below the surface) is located in the upper left (SE) wall of the pond.

Lava continued to enter the ocean, building a lava bench (figures 58 and 59), although at a diminished rate during strong surface activity. The active portion of the bench was 200 x 80 m in March, and older inactive portions remained susceptible to collapse. Minor collapses occurred 3 and 17 March, then a major collapse on the 23rd at 0335 destroyed 65% of the bench, including almost all of the active section. By the end of the month, the bench was rebuilding and the new active portion measured ~170 x 20 m. Explosivity during the collapses was minor.

Figure 58. View by J. Griggs (USGS) from the E side of Kilauea's 1986-89 flow field, looking W. The steam plume marks the point where lava has been continuously entering the ocean since May 1988.

Figure 59. Close-up aerial view by J. Griggs (USGS) of Kilauea's actively growing lava bench, 1-3 m below the older sea cliff. As the bench grows, it spreads laterally (parallel to the sea cliff) as well as seaward. In the photograph, the bench is 30-40 m wide. A smooth tephra deposit, extending onshore from the edge of the sea cliff, is visible to the right of the plume.

Low-level tremor continued near vents on the middle East rift zone and where lava entered the ocean. Bench collapse was registered as a series of rockfall and acoustic signals at the Wahaula seismic station, 3 km away. Intermediate-depth, long-period events and tremor were intermittent beneath the summit. Bursts of deep tremor were centered 40-60 km beneath the S part of Hawaii.

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

Information Contacts: C. Heliker and R. Koyanagi, HVO.

"There was a slight increase in March in the overall low level of inter-eruptive activity since the last significant eruption in March-May 1986 (SEAN 11:3-5). During the first week of March, 2-7 low-frequency explosion earthquakes were recorded daily, some of which were accompanied by detonations heard at the observation post . . . . Weak rumbling noises were occasionally heard and weak red glow was reported on the nights of 28 and 29 March. Vapour emission from Crater 2 was of moderate volume throughout the month with occasional grey ash clouds. Crater 3 was inactive."

Geologic Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: P. de Saint-Ours and C. McKee, RVO.

. . . Paul King climbed the volcano in February 1989 and saw what appeared to be an active lava dome in the summit crater. Gas emission was vigorous, but no glow was visible from Toconao, ~30 km from the volcano.

During observations by M. Gardeweg and Adrian Jones 23 March-1 April 1989, irregular, dominantly steam emissions were continuously released from the N part of the E cone of this composite of two andesitic cones. Columns rose 400-600 m above the cone and plumes extended SE, with occasional fine-grained fallout. Observation from the SE flank on 26 March showed the steam to include sulfurous gas and light ash, which was being deposited on the E flank. A 1-m bomb in a fresh crater 4 m in diameter, 3 km S of the active summit, must have been erupted within recent months, although there are no reports of an eruption. The regular activity was interrupted for one day (29 March) by a change from emission of voluminous dense steam to light, translucent gas visible only near the summit.

Geologic Background. Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km E, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away. The largest historical eruption took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Information Contacts: M. Gardeweg, SERNAGEOMIN, Santiago; A. Jones, Kingston Polytechnic, Surrey UK; P. King, Minsal Co., Toconao, Chile; P. Francis, Lunar & Planetary Institute, Houston.

Moderate ash emission and lava production were continuing in mid-April from Navidad cone. Increased seismicity had preceded the onset of more vigorous tephra emission on 24 February and activity remained strong into early March (figure 9). As of early April, ash clouds were rising to 3-4 km altitude. Most ash fell E of the volcano. The rate of lava production peaked 2-7 January at an estimated 75 m³/s, then declined, but was increasing slightly in late March (table 6). By 25 March, after 90 days of activity, the lava flow volume was estimated at 1.03 x 108 m³, and it had advanced 10 km down the Lolco river valley (figure 10).

Figure 9. Altitudes reached by tephra clouds from Navidad cone (curve) and number of seismic events in 4-hour periods (bars), 18 January-5 March 1989. Courtesy of O. González-Ferrán.

Table 6. Estimated dimensions, volume, extrusion rate, and flow front velocity of the andesitic block lava from Navidad crater, 25 December 1988-25 March 1989. Courtesy of O. González-Ferrán.

Figure 10. Sketch map showing the advance of the lava flow, 25 December 1988-26 March 1989. Courtesy of O. González-Ferrán, H. Moreno, and P. Riffo.

Navidad cone, an asymmetric pyroclastic cone composed of black scoria with a minor amount of spatter-like bombs, was 210 m high and 700 m in E-W basal diameter in early April. It remained horseshoe-shaped, breached to the N. The crater was funnel-shaped and elongated NNE, with a minimum diameter of 250 m NW-SE. At its eastern base were 3-4 vents, one of which was continuously active. As viewed from the S, the cone changed in shape from uniform slopes with a higher W rim, to an irregular E slope with a bulge close to the top and a higher E rim.

During early April, the eruption column varied between 500 and 1,500 m above the crater. Strong WNW winds dispersed the plume eastward to the Lonquimay District. Geologists estimated that the VEI has decreased to 1-2, from 2-3 in early January. Two conspicuous eruptive phases were observed in alternate periods of 10 to 90 minutes; a phreatic, strongly explosive one accompanied by a white to pale-brownish small ash/steam column, and a noiseless, voluminous, dark gray-brownish, tephra-rich column associated with deeper degassing and fragmentation.

Black scoria and dark gray ash have been deposited mainly E of the cone. Bombs of various shapes and sizes have been observed as far as 1 km NE of the vent, where they occasionally reached 2.5 m across. S and E of the cone the bombs fell closer, <200 m from its base. Ribbon, spindle, spatter, and minor cow-dung bombs were also observed.

By 5 April, the lava flow had two well-defined lobes. The longer was advancing along the Lolco river valley. The shorter, quite active, lobe was a new one moving NW on top of a flow from early in the eruption (Laguna Verde). The Lolco front reached 35 m height, and had a temperature of 1,040°C. It was advancing over a swampy area, causing soil deformation, squeezing the soft sediments, and contaminating the water of the Lolco river. Nearly 0.8 km² of wild Araucaria forest have been destroyed along this valley. By early April, the lava flow covered an area of ~9.5 km². Locally, the rough lava surface shows yellowish iron chlorides due to the high HCl content of the volcanic gases. SO₂ has also been detected.

Geologic Background. Lonquimay is a small, flat-topped, symmetrical stratovolcano of late-Pleistocene to dominantly Holocene age immediately SE of Tolguaca volcano. A glacier fills its summit crater and flows down the S flank. It is dominantly andesitic, but basalt and dacite are also found. The prominent NE-SW Cordón Fissural Oriental fissure zone cuts across the entire volcano. A series of NE-flank vents and scoria cones were built along an E-W fissure, some of which have been the source of voluminous lava flows, including those during 1887-90 and 1988-90, that extended out to 10 km.

Information Contacts: O. González-Ferrán, Univ de Chile; H. Moreno, Univ de Chile; M. Gardeweg and J. Naranjo, SERNAGEOMIN, Santiago.

"Activity . . . remained at a low inter-eruptive level throughout March. Both Southern and Main Craters released white vapours at weak to moderate rates. Wisps of blue vapour were also released by Crater 2 on 6-9 and 22-27 March. Weak rumbling noises were heard intermittently although no night glow, incandescent ejections, or Vulcanian explosions were reported. Seismicity remained at a normal inter-eruptive level with a daily average of 1,100-1,400 small low-frequency events superimposed on sub-continuous tremor. Tilt measurements showed no trends."

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: P. de Saint-Ours and C. McKee, RVO.

During a 14 January overflight, strong gas emission from Kudriavy's crater formed a cloud that reached 300-400 m above the summit. The inner part of the crater was not visible.

Geologic Background. The Moyorodake volcanic complex (also known as Medvezhia) occupies the NE end of Iturup (Etorofu) Island. Two overlapping calderas, 14 x 18 and 10 x 12 km in diameter, were formed during the Pleistocene. The caldera floor contains several lava domes, cinder cones and associated lava fields, and a small lake. Four small closely spaced stratovolcanoes were constructed along an E-W line on the eastern side of the complex. The easternmost and highest, Medvezhii, lies outside the western caldera, along the Pacific coast. Srednii, Tukap, and Kudriavy (Moyorodake) volcanoes lie immediately to the west. Historically active Moyorodake is younger than 2000 years; it and Tukap remain fumarolically active. The westernmost of the post-caldera cones, Menshoi Brat, is a large lava dome with flank scoria cones, one of which has produced a series of young lava flows up to 4.5 km long that reached Slavnoe Lake. Eruptions have been documented since the 18th century, although lava flows from cinder cones on the flanks of Menshoi Brat were also probably erupted within the past few centuries.

Information Contacts: G. Steinberg, Yuzhno-Sakhalinsk.

The level of the crater lake continued to descend, dropping another 2 m in March for a cumulative decline of about 32 m since early 1987 (figures 11 and 12). Phreatic (geyser-type) eruptions were sporadic and generally no more than 10 m high, although ejecta reached heights of 60 m on 12 February and 50 m on 2 April. Lake water was colored muddy gray by suspended sediment, and convective bubbling was continuous. At the beginning of March, movement of rafts of floating sediment illustrated convective trajectories within the lake. Rafts were not seen in the middle of the month, although there was some thick floating sediment. By the end of March, no floating material was evident. The temperature of the lake water averaged 82°C.

Figure 11. W-E diagrammatic cross-section of the crater at Poás illustrating March 1989 activity. Courtesy of Gerardo Soto.

Figure 12. Sketch map of the crater at Poás in March 1989. Courtesy of Gerardo Soto.

Small sulfur cones had formed on sedimentary terraces at the SE edge of the lake, constantly ejecting sprays of mud and pyroclastic sulfur that carpeted the surrounding area. Some had collapsed, forming craters that continuously emitted gas. The most active made a sound like a jet aircraft. Some of the cones were topped by chimney-like structures ~1 m high, made of sulfur. Two small sulfur cones had also developed on the lake's NE edge, venting gases with a mean temperature of 98°C.

Fumarolic activity on the 1953-55 [dome] was weak and located at the summit and N side, with temperatures varying between 59°C and 91°C. The temperature of fumaroles W of the [dome] was 95°C.

Prevailing winds carried volcanic gases W and SW of the crater, damaging vegetation and causing health problems for residents. Towns to 10 km SW of the crater (such as San Luis Cajón de Grecia) were impacted. Coffee has been the crop most affected, with preliminary calculations of losses reaching about $500,000. Trees (cypress, jaul, and eucalyptus) and grass were burned by acid rain. The inhabitants of towns as far as Trojas de Valverde Vega (11 km WSW of the crater) and San Pedro Poás (14 km SW) suffered health problems including eye and respiratory irritation and allergies. Consequently, local health facilities have had an increase in patients.

Since mid-January, a telemetering seismic station near the summit (POA2) has registered an average of 300 B-type events/day. Volcanic microseismicity declined in March compared to February, but remained higher than in 1988. Between 1 and 29 March, 6,726 events were recorded, an average of 232/day. The most active day was the 18th, when 346 shocks were detected (figure 13). Most were B-types, some with dispersive trains. Only three A-types were recorded during the month. Partial reoccupation of a level line indicated that 25 µrad of deflation had accumulated between October 1988 and March 1989. The horizontal distance across the crater did not show significant changes.

Figure 13. Number of local seismic events/day recorded by the Red Sismológica Nacional, March 1989. Courtesy of G. Soto.

Geologists from the Univ de Costa Rica noted that the thermal activity formerly concentrated at the 1953-55 [dome] (between 1980 and 1987) has moved to the lake. They suggested two possible causes: (1) the fracture zone that controls thermal energy release has changed position; or (2) magma is rising below the lake, causing greater heat flow, and could lead to an eruptive event.

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

Information Contacts: J. Barquero, OVSICORI; G. Soto, Mario Fernández, and Héctor Flores, UCR.

"Activity remained at background level in March. Seismicity totaled 183 small events (M_L 0.5-1.5). Only four could be located and these originated from Greet Harbour. The daily earthquake count fluctuated between 0 and 30. There was no significant change recorded in ground deformation."

Geologic Background. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor utilized by what was the island's largest city prior to a major eruption in 1994. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.

Information Contacts: P. de Saint-Ours and C. McKee, RVO.

Four groups of fumaroles were observed in a crater, breached to the SE, during a 14 January overflight.

Geologic Background. The elongated 6 x 13 km island of Rasshua in the central Kuriles contains three overlapping central cones within a 6 km caldera whose eastern margin is beyond the shoreline. An eroded central cone was constructed during the late Pleistocene, along with an isolated cone near the NW coast. Two Holocene cones were built within the crater of the central cone. The westernmost forms the 956 m high point of the island and is the source of lava flows that flooded the crater floor and descended to the coast. The easternmost cone, active during historical time, is truncated by a 500-m-wide crater that is breached to the SE. This crater may have formed during a violent eruption in 1846. The only other known historical eruption produced weak explosions in 1957. Fumarolic activity continues in the eastern crater and in the saddle between the two summit cones.

Information Contacts: G. Steinberg, Yuzhno-Sakhalinsk.

Minor phreatic eruptions were reported from late January through February, but only steam emission has been reported since then. Crater Lake's temperature dropped from 42.5°C on 26 February to 32° on 22 March, and 31.3° on 6 April, suggesting to geophysicists that heat flow through the lake had dropped by roughly an order of magnitude. A continuous temperature monitor was installed near the Crater Lake outlet on 21 March. Minor inflation that had accumulated across the N crater rim between 26 February and 22 March had nearly disappeared by 5 April. Seismic records in March and early April showed little or no tremor or volcanic earthquakes.

Geologic Background. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The 110 km3 dominantly andesitic volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake, is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys.

Information Contacts: P. Otway, NZGS Wairakei.

Seismic energy and the number of high-frequency events decreased during March continuing a general long-term decline. Short pulses (averaging 5 minutes) of low-energy tremor with periods of ~0.25-0.30 seconds were associated with small ash emissions. Dry and electronic tilt and short leveling vectors showed little change. SO₂ emissions measured by COSPEC varied from 900 to 4,500 t/d with a monthly average of 1,921 t/d (see figure 26). Emissions were blown SE.

Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Information Contacts: C. Carvajal, INGEOMINAS, Manizales.

An ash eruption was reported on 14 January at 1136. During an overflight between 1220 and 1250, clouds at 1,300-1,800 m altitude obscured the summit . . . . No eruption columns were observed above the weather clouds. Two narrow gray bands on the volcano's snow-covered N and NE slopes suggested ash emission had occurred the previous day. The activity was preceded by a series of felt earthquakes 5-12 January. Epicenters of some strong earthquakes (M<=6.2) were located in the Simushir Island region . . . .

Geologic Background. Sarychev Peak, one of the most active volcanoes of the Kuril Islands, occupies the NW end of Matua Island in the central Kuriles. The andesitic central cone was constructed within a 3-3.5-km-wide caldera, whose rim is exposed only on the SW side. A dramatic 250-m-wide, very steep-walled crater with a jagged rim caps the volcano. The substantially higher SE rim forms the 1496 m high point of the island. Fresh-looking lava flows, prior to activity in 2009, had descended in all directions, often forming capes along the coast. Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits. Eruptions have been recorded since the 1760s and include both quiet lava effusion and violent explosions. Large eruptions in 1946 and 2009 produced pyroclastic flows that reached the sea.

Information Contacts: G.S. Steinberg, Institute of Marine Geology & Geophysics, Yuzhno-Sakhalinsk.

A series of explosions occurred in Stromboli's summit craters [26] March at [0927]. The explosions lasted a few minutes and were significantly more intense than the volcano's regular intermittent activity. Ejecta consisted of fluid bombs, blocks, and ash that were scattered within a few hundred meters of the vents. Tourists observing the volcano nearby were hit by the shower of tephra. No one was directly injured by the fallout, but a girl fell and broke her arm when panic caused a rush towards the village.

According to numerous eyewitnesses, the explosions began without premonitory activity. Seismic records from the Ginostra station (1.8 km from the crater) recorded no significant variation before or after the event. However, a slight increase in volcanic tremor amplitude and energy of seismic shocks was observed a few days before the explosions by a portable seismograph operating on the N flank (1.5 km from the vents). The rate of gas emission and frequency of explosions gradually returned to a normal level in the following days.

Further Reference. Falsaperla, S., Montalto, A., and Spampinato, S., 1989, Analysis of seismic data concerning explosive sequences on Stromboli volcano in 1989: Bolletino del Gruppo Nazionale per la Vulcanologia, 1989-1, p. 249-258.

Geologic Background. Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Information Contacts: S. Falsaperla, G. Frazzetta, and E. Privitera, IIV; M. Rosi, Univ di Pisa.

On 1, 14, and 16 January, residents . . . heard explosions. Ash fell to the S on 21 and 24 January in the the only inhabited part of the small island. On 7 February at 1225, an explosion sound was heard, and on 28 February, a 1,000-m-high ash plume deposited large amounts of ash to the S. At 1640 on 3 March, the crew of a JAS aircraft observed a 2,000-m ash cloud. A summary of [1987-88] explosions and ashfall is shown in table 2.

Table 2. Eruptive episodes at Suwanose-jima, January 1987-October 1988. Courtesy of JMA.

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

Information Contacts: JMA.

Activity continued to decrease in March. Since the brief 5 March explosion (14:02) no explosions have been observed and seismicity has been low (figure 4). The steam plume reached a maximum height of 1,000 m above the rim of 62-2 Crater at 1300 on the 28th. An earthquake swarm that began 14 January . . . declined during March.

Figure 4. Monthly number of earthquakes at Tokachi-dake (top) and maximum monthly plume heights (bottom), January 1983-March 1989. Courtesy of JMA.

Geologic Background. Tokachidake volcano consists of a group of dominantly andesitic stratovolcanoes and lava domes arranged on a NE-SW line above a plateau of welded Pleistocene tuffs in central Hokkaido. Numerous explosion craters and cinder cones are located on the upper flanks of the small stratovolcanoes, with the youngest Holocene centers located at the NW end of the chain. Frequent historical eruptions, consisting mostly of mild-to-moderate phreatic explosions, have been recorded since the mid-19th century. Two larger eruptions occurred in 1926 and 1962. Partial cone collapse of the western flank during the 1926 eruption produced a disastrous debris avalanche and mudflow.

Information Contacts: JMA.

"Unrest appeared related to the amount of rainfall on the volcano. Heavy rainfall started 26 February and continued until 7 March. After ~6 weeks of very low-level activity (following phreatomagmatic eruptions in January; 14:01) volcanic seismicity strengthened on 28 February, with periods of irregular tremor that increased progressively in amplitude. Following the maximum daily rainfall of 142 mm on 3 March, a strong white vapour plume was observed above the summit crater the next day. On the 5th, the plume had become a large ash-laden column rising to 1,000 m, while seismicity reached 8 times 'normal' amplitude levels. A large grey plume with weak red glow was observed on the nights of 5, 6, and 9 March. Seismicity subsided 6-8 March but returned to a moderately high level during the following week, though with a change in pattern; the tremor periods being replaced with a succession of discrete, emergent events.

"Following another period of strong rainfall (63 mm on the 15th), the moderately strong vapour plume again became ash-laden (grey) until the 22nd. The seismicity showed a different response; it suddenly declined from medium intensity to virtually nothing on the 17th, after a period of strong tremor lasting ~10 minutes. Subsequently, seismicity re-intensified progressively until the 20th when it rapidly rose from medium to high, but dropped suddenly again to virtually nothing on the 22nd.

"At the end of the month, the summit crater was gently releasing a weak to moderate white vapour plume and seismicity was at a very low level. On the 30th, an Ms 5 regional earthquake, 75 km away, triggered continuous tremor lasting the following 2 1/2 days.

"The thick dark column and night glows at the beginning of the month caused some degree of alert amung the local population. An on-site inspection and survey on the 6th showed no significant ground deformation, allowing the release of an information bulletin forecasting phreatic or phreatomagmatic activity similar to early January."

Geologic Background. The symmetrical basaltic-to-andesitic Ulawun stratovolcano is the highest volcano of the Bismarck arc, and one of Papua New Guinea's most frequently active. The volcano, also known as the Father, rises above the N coast of the island of New Britain across a low saddle NE of Bamus volcano, the South Son. The upper 1,000 m is unvegetated. A prominent E-W escarpment on the south may be the result of large-scale slumping. Satellitic cones occupy the NW and E flanks. A steep-walled valley cuts the NW side, and a flank lava-flow complex lies to the south of this valley. Historical eruptions date back to the beginning of the 18th century. Twentieth-century eruptions were mildly explosive until 1967, but after 1970 several larger eruptions produced lava flows and basaltic pyroclastic flows, greatly modifying the summit crater.

Information Contacts: P. de Saint-Ours and C. McKee, RVO.

Two groups of highly active fumaroles were observed in the S part of the caldera during a 14 January aerial inspection. In autumn 1988, land observations showed solfataric activity, pressurized gas emission, and sulfur deposits within a 170 x 50 m area. Gas temperatures were 100-104°C.

Geologic Background. The subaerial portion of Ushishur volcano in the central Kuriles is exposed in two small islands, the southern containing the summit caldera and the northern a portion of the volcano's flanks. A small 1.6-km-wide caldera that formed about 9400 years ago is narrowly breached on the south, allowing sea water to fill the caldera. Two andesitic lava domes occupy part of the caldera bay; two other older domes are joined by a sand bar to the SE caldera wall. The two younger domes, erupted sometime after the 1769 visit of Captain Snow, form islands in the bay. A cluster of strong fumaroles and hot springs along the SE caldera shoreline was a sacred place to 18th- and 19th-century Kurile Ainu peoples, and vigorous submarine hydrothermal activity has modified the geochemistry of sea water within the caldera bay. Aside from growth of the two younger lava domes, only minor phreatic eruptions have occurred at Ushishur during historical time.

Information Contacts: G. Steinberg, Yuzhno-Sakhalinsk.

Activity from R.F. Crater declined to intermittent ash emission in February and March. When helicopter pilot Robert Fleming visited White Island on 14 February, R.F. Crater was emitting ash. Additional tephra was found in the Blue Duck-Donald Mound area (figure 11) about 200 m to the E. On 19 February, R.F. Crater was quiet. Fleming's subsequent visits on 25 and 27 February and 5 March revealed that the new Donald Duck vent, about 40 m N of Donald Mound and first seen 29 January, had grown and ejected tephra. R.F. Crater was no longer emitting much ash during those visits.

Figure 11. Sketch map, showing recently active features on White Island, early 1989. The area shown is indicated by the box on the index map. Courtesy NZGS.

Vigorous explosions occurred 26 February and 14 March, producing tephra columns visible from the mainland (>50 km away). Both were accompanied by E-type earthquakes. The 14 March explosion, the largest magmatic event since early April 1988 (SEAN 13:04), scattered scoria bombs over the S margin of the main crater floor.

During geological fieldwork two days later, R.F. Crater emitted a light-pink steam plume. The Donald Duck vent was surrounded by new lithic blocks and had enlarged to 20 m in diameter and 10 m in depth. Vents on its floor emitted brown gas and intermittent ash.

Donald Duck vent erupted between 16 and 20 March, probably during a 25-minute E-type earthquake sequence that started at 1624 on 16 March. The blast was directed SSE, depositing gray-white coarse gravel near the vent and blocks up to 300 m away. No fresh scoria was found. The eruption enlarged the vent to 15 m deep and 30 m in diameter. Between 9 February and 20 March, >10 cm of new ash and lapilli had accumulated at the 1978 Crater rim. Red glow, probably caused by incandescent gas emission, was seen during the night of 21 March from Whakatane (50 km SSW ). No unusual seismic activity was recorded.

Fumarole temperatures declined after 9 February, probably due to heavy rainfall. Magnetic and crater floor deformation surveys suggested no significant rise of magma. Two months of inflation in the vicinity of the Donald Duck vent had ended, with deflation occurring between surveys on 9 February and 16 and 20 March.

Seismicity 9 February-16 March consisted of medium-to-strong high-frequency microearthquakes and persistent small A- and B-type events. Harmonic tremor and rare E-types were also recorded. After 22 February, B-type events averaged ~9/day. Low-amplitude, 1.5- to 2-Hz tremor was recorded 19 and 20 February. E-type shocks were recorded 22, 24, and 26 February, and 14 and 16 March.

Geologic Background. The uninhabited White Island, also known as Whakaari in the Maori language, is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The summit crater appears to be breached to the SE, because the shoreline corresponds to the level of several notches in the SE crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of eruptions since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. Formation of many new vents during the 19th and 20th centuries has produced rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities.

Information Contacts: I. Nairn, NZGS Rotorua.

During a 14 January overflight, strong gas emission was observed near the 1957 dome, in the N part of the caldera. A lake occupied the caldera center.

Geologic Background. Zavaritzki volcano in central Simushir Island contains three nested calderas of 10-, 8-, and 3-km diameter. The steep-walled youngest caldera was formed during the Holocene and contains a lake whose surface is about 40 m elevation and whose bottom lies about 30 m below sea level. Several young cones and lava domes are located near the margins of Biryuzovoe caldera lake. Lacustrine sediments overlying pumice deposits indicate that an earlier caldera lake lay at 200 m above sea level, well above the present lake surface. Two eruptions have occurred at Zavaritzki during the 20th century. A lava dome that was emplaced sometime between 1916 and 1931 forms a small island in the northern part of the caldera lake. In 1957, a new 350-m-wide, 40-m-high dome was emplaced following explosive eruptions, decreasing the size of the caldera lake.

Information Contacts: G. Steinberg, Yuzhno-Sakhalinsk.

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/).