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Bulletin of the Global Volcanism Network

All reports of volcanic activity published by the Smithsonian since 1968 are available through a monthly table of contents or by searching for a specific volcano. Until 1975, reports were issued for individual volcanoes as information became available; these have been organized by month for convenience. Later publications were done in a monthly newsletter format. Links go to the profile page for each volcano with the Bulletin tab open.

Information is preliminary at time of publication and subject to change.


Recently Published Bulletin Reports

Sangeang Api (Indonesia) Ash emissions and lava flow extrusion continue during May 2019 through January 2020

Shishaldin (United States) Multiple lava flows, pyroclastic flows, lahars, and ashfall events during October 2019 through January 2020

Nevados de Chillan (Chile) Many explosions, ash plumes, lava and pyroclastic flows June-December 2019

Asosan (Japan) Intermittent ash plumes and elevated SO2 emissions continue during July-December 2019

Tinakula (Solomon Islands) Intermittent thermal activity suggests ongoing eruption, July-December 2019

Ibu (Indonesia) Frequent ash plumes and small lava flows in the crater through December 2019

Lateiki (Tonga) Eruption 13-22 October 2019 creates new island, which disappears by mid-January 2020

Aira (Japan) Ongoing explosions with ejecta and ash plumes, along with summit incandescence, during July-December 2019

Suwanosejima (Japan) Explosions, ash emissions, and summit incandescence in July-December 2019

Barren Island (India) Thermal anomalies and small ash plumes during February-April 2019 and September 2019-January 2020

Whakaari/White Island (New Zealand) Explosion producing an ash plume and pyroclastic surge resulted in fatalities and injuries on 9 December 2019

Kadovar (Papua New Guinea) Frequent gas and some ash emissions during May-December 2019 with some hot avalanches



Sangeang Api (Indonesia) — February 2020 Citation iconCite this Report

Sangeang Api

Indonesia

8.2°S, 119.07°E; summit elev. 1912 m

All times are local (unless otherwise noted)


Ash emissions and lava flow extrusion continue during May 2019 through January 2020

Sangeang Api is located in the eastern Sunda-Banda Arc in Indonesia, forming a small island in the Flores Strait, north of the eastern side of West Nusa Tenggara. It has been frequently active in recent times with documented eruptions spanning back to 1512. The edifice has two peaks – the active Doro Api cone and the inactive Doro Mantori within an older caldera (figure 37). The current activity is focused at the summit of the cone within a horseshoe-shaped crater at the summit of Doro Api. This bulletin summarizes activity during May 2019 through January 2020 and is based on Darwin Volcanic Ash Advisory Center (VAAC) reports, Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, or CVGHM) MAGMA Indonesia Volcano Observatory Notice for Aviation (VONA) reports, and various satellite data.

Figure (see Caption) Figure 37. A PlanetScope satellite image of Sangeang Api with the active Doro Api and the inactive Doro Mantori cones indicated, and the channel SE of the active area that contains recent lava flows and other deposits. December 2019 monthly mosaic copyright of Planet Labs 2019.

Thermal anomalies were visible in Sentinel-2 satellite thermal images on 4 and 5 May with some ash and gas emission visible; bright pixels from the summit of the active cone extended to the SE towards the end of the month, indicating an active lava flow (figure 38). Multiple small emissions with increasing ash content reached 1.2-2.1 km altitude on 17 June. The emissions drifted W and WNW, and a thermal anomaly was also visible. On the 27th ash plumes rose to 2.1 km and drifted NW and the thermal anomaly persisted. One ash plume reached 2.4 km and drifted NW on the 29th, and steam emissions were ongoing. Satellite images showed two active lava flows in June, an upper and a lower flow, with several lobes descending the same channel and with lateral levees visible in satellite imagery (figure 39). The lava extrusion appeared to have ceased by late June with lower temperatures detected in Sentinel-2 thermal data.

Figure (see Caption) Figure 38. Sentinel-2 satellite thermal images of Sangeang Api on 20 May and 9 June 2019 show an active lava flow from the summit, traveling to the SE. False color (urban) image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 39. PlanetScope satellite images of Sangeang Api show new lava flows during June and July, with white arrows indicating the flow fronts. Copyright Planet Labs 2019.

During 4-5 July the Darwin VAAC reported ash plumes reaching 2.1-2.3 km altitude and drifting SW and W. Activity continued during 6-9 July with plumes up to 4.6 km drifting N, NW, and SW. Thermal anomalies were noted on the 4th and 8th. Plumes rose to 2.1-3 km during 10-16th, and to a maximum altitude of 4.6 km during 17-18 and 20-22. Similar activity was reported during 24-30 July with plumes reaching 2.4-3 km and dispersing NW, W, and SW. The upper lava flow had increased in length since 15 June (see figure 39).

During 31 July through 3 September ash plumes continued to reach 2.4-3 km altitude and disperse in multiple directions. Similar activity was reported throughout September. Thermal anomalies also persisted through July-September, with evidence of hot avalanches in Sentinel-2 thermal satellite imagery on 23 August, and 9, 12, 22, and 27 September. Thermal anomalies suggested hot avalanches or lava flows during October (figure 40). During 26-28 October short-lived ash plumes were reported to 2.1-2.7 km above sea level and dissipated to the NW, WNW, and W. Short-lived explosions produced ash plumes up to 2.7-3.5 km altitude were noted during 30-31 October and 3-4 November 2019.

Figure (see Caption) Figure 40. Sentinel-2 satellite thermal images of Sangeang Api on 7 and 22 October 2019 show an area of elevated temperatures trending from the summit of the active cone down the SE flank. False color (urban) image rendering (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Discrete explosions produced ash plumes up to 2.7-3.5 km altitude during 3-4 November, and during the 6-12th the Darwin VAAC reported short-lived ash emissions reaching 3 km altitude. Thermal anomalies were visible in satellite images during 6-8 November. A VONA was released on 14 November for an ash plume that reached about 2 km altitude and dispersed to the west. During 14-19 November the Darwin VAAC reported short-lived ash plumes reaching 2.4 km that drifted NW and W. Additional ash plumes were observed reaching a maximum altitude of 2.4 km during 20-26 November. Thermal anomalies were detected during the 18-19th, and on the 27th.

Ash plumes were recorded reaching 2.4 km during 4-5, 7-9, 11-13, and 17-19 December, and up to 3 km during 25-28 December. There were no reports of activity in early to mid-January 2020 until the Darwin VAAC reported ash reaching 3 km on 23 January. A webcam image on 15 January showed a gas plume originating from the summit. Several fires were visible on the flanks during May 2019 through January 2020, and this is seen in the MIROVA log thermal plot with the thermal anomalies greater than 5 km away from the crater (figure 41).

Figure (see Caption) Figure 41. MIROVA log plot of radiative power indicates the persistent activity at Sangeang Api during April 2019 through March 2020. There was a slight decline in September-October 2019 and again in February 2020. Courtesy of MIROVA.

Geologic Background. Sangeang Api volcano, one of the most active in the Lesser Sunda Islands, forms a small 13-km-wide island off the NE coast of Sumbawa Island. Two large trachybasaltic-to-tranchyandesitic volcanic cones, Doro Api and Doro Mantoi, were constructed in the center and on the eastern rim, respectively, of an older, largely obscured caldera. Flank vents occur on the south side of Doro Mantoi and near the northern coast. Intermittent historical eruptions have been recorded since 1512, most of them during in the 20th century.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/).


Shishaldin (United States) — February 2020 Citation iconCite this Report

Shishaldin

United States

54.756°N, 163.97°W; summit elev. 2857 m

All times are local (unless otherwise noted)


Multiple lava flows, pyroclastic flows, lahars, and ashfall events during October 2019 through January 2020

Shishaldin is located near the center of Unimak Island in Alaska and has been frequently active in recent times. Activity includes steam plumes, ash plumes, lava flows, lava fountaining, pyroclastic flows, and lahars. The current eruption phase began on 23 July 2019 and through September included lava fountaining, explosions, and a lava lake in the summit crater. Continuing activity during October 2019 through January 2020 is described in this report based largely on Alaska Volcano Observatory (AVO) reports, photographs, and satellite data.

Minor steam emissions were observed on 30 September 2019, but no activity was observed through the following week. Activity at that time was slightly above background levels with the Volcano Alert Level at Advisory and the Aviation Color Code at Yellow (figure 17). In the first few days of October weak tremor continued but no eruptive activity was observed. Weakly elevated temperatures were noted in clear satellite images during 4-9 October and weak tremor continued. Elevated temperatures were recorded again on the 14th with low-level tremor.

Figure (see Caption) Figure 17. Alaska Volcano Observatory hazard status definitions for Aviation Color Codes and Volcanic Activity Alert Levels used for Shishaldin and other volcanoes in Alaska. Courtesy of AVO.

New lava extrusion was observed on 13 October, prompting AVO to raise the Aviation Color Code to Orange and the Volcano Alert Level to Watch. Elevated surface temperatures were detected by satellite during the 13th and 17-20th, and a steam plume was observed on the 19th. A change from small explosions to continuous tremor that morning suggested a change in eruptive behavior. Low-level Strombolian activity was observed during 21-22 October, accompanied by a persistent steam plume. Lava had filled the crater by the 23rd and began to overflow at two places. One lava flow to the north reached a distance of 200 m on the 24th and melted snow to form a 2.9-km-long lahar down the N flank. The second smaller lava flow resulted in a 1-km-long lahar down the NE flank. Additional snowmelt was produced by spatter accumulating around the crater rim. By 25 October the northern flow reached 800 m, there was minor explosive activity with periodic lava fountaining, and lahar deposits reached 3 km to the NW with shorter lahars to the N and E (figure 18). Trace amounts of ashfall extended at least 8.5 km SE. There was a pause in activity on the 29th, but beginning at 1839 on the 31st seismic and infrasound monitoring detected multiple small explosions.

Figure (see Caption) Figure 18. PlanetScope satellite images of Shishaldin on 3 and 29 October 2019 show the summit crater and N flank before and after emplacement of lava flows, lahars, and ashfall. Copyright PlanetLabs 2019.

Elevated activity continued through November with multiple lava flows on the northern flanks (figure 19). By 1 November the two lava flows had stalled after extending 1.8 km down the NW flank. Lahars had reached at least 4 km NW and trace amounts of ash were deposited on the north flank. Elevated seismicity on 2 November indicated that lava was likely flowing beyond the summit crater, supported by a local pilot observation. The next day an active lava flow moved 400 m down the NW flank while a smaller flow was active SE of the summit. Minor explosive activity and/or lava fountaining at the summit was indicated by incandescence during the night. Small explosions were recorded in seismic and infrasound data. On 5 November the longer lava flow had developed two lobes, reaching 1 km in length. The lahars had also increased in length, reaching 2 km on the N and S flanks. Incandescence continued and hot spatter was accumulating around the summit vent. Activity continued, other than a 10-hour pause on 4-5 November, and another pause on the 7th. The lava flow length had reached 1.3 km on the 8th and lahar deposits reached 5 km.

Figure (see Caption) Figure 19. Sentinel-2 thermal satellite images show multiple lava flows (orange) on the upper northern flanks of Shishaldin between 1 November and 1 December 2019. Blue is snow and ice in these images, and partial cloud cover is visible in all of them. Sentinel-2 Urban rendering (bands 21, 11, 4) courtesy of Sentinel Hub Playground.

After variable levels of activity for a few days, there was a significant increase on 10-11 November with lava fountaining through the evening and night. This was accompanied by minor to moderate ash emissions up to around 3.7 km altitude and drifting northwards, and a significant increase in seismicity. Activity decreased again during the 11-12th while minor steam and ash emissions continued. On 14 November minor ash plumes were visible on the flanks, likely caused by the collapse of accumulated spatter. By 15 November a large network of debris flows consisting of snowmelt and fresh deposits extended 5.5 km NE and the collapse of spatter mounds continued. Ashfall from ash plumes reaching as high as 3.7 km altitude produced thin deposits to the NE, S, and SE. Activity paused during the 17-18th and resumed again on the 19th; intermittent clear views showed either a lava flow or lahar descending the SE flank. Activity sharply declined at 0340 on the 20th.

Seismicity began increasing again on 24 November and small explosions were detected on the 23rd. A small collapse of spatter that had accumulated at the summit occurred at 2330 on the 24th, producing a pyroclastic flow that reached 3 km in length down the NW flank. A new lava flow had also reached several hundred meters down the same flank. Variable but elevated activity continued over 27 November into early December, with a 1.5-km-long lava flow observed in satellite imagery acquired on the 1st. On 5 December minor steam or ash emissions were observed at the summit and on the north flank, and Strombolian explosions were detected. Activity from that day produced fresh ash deposits on the northern side of the volcano and a new lava flow extended 1.4 km down the NW flank. Three small explosions were detected on the 11th.

At 0710 on 12 December a 3-minute-long explosion produced an ash plume up to 6-7.6 km altitude that dispersed predominantly towards the W to NW and three lightning strokes were detected. Ash samples were collected on the SE flank by AVO field crews on 20 December and analysis showed variable crystal contents in a glassy matrix (figure 20). A new ash deposit was emplaced out to 10 km SE, and a 3.5-km-long pyroclastic flow had been emplaced to the north, containing blocks as large as 3 m in diameter. The pyroclastic flow was likely a result from collapse of the summit spatter cone and lava flows. A new narrow lava flow had reached 3 km to the NW and lahars continued out to the northern coast of Unimak island (figure 21). The incandescent lava flow was visible from Cold Bay on the evening of the 12th and a thick steam plume continued through the next day.

Figure (see Caption) Figure 20. An example of a volcanic ash grain that was erupted at Shishaldin on 12 December 2019 and collected on the SE flank by the Alaska Volcano Observatory staff. This Scanning Electron Microscope images shows the different crystals represented by different colors: dark gray crystals are plagioclase, the light gray crystals are olivine, and the white ones are Fe-Ti oxides. The groundmass in this grain is nearly completely crystallized. Courtesy of AVO.
Figure (see Caption) Figure 21. A WorldView-2 satellite image of Shishaldin with the summit vent and eruption deposits on 12 December 2019. The tephra deposit extends around 10 km SE, a new lava flow reaching 3 km NW with lahars continuing to the N coast of Unimak island. Pyroclastic flow deposits reach 3.5 km to the N and contain blocks as large as 3 m. Courtesy of Hannah Dietterich, AVO.

A new lava flow was reported by a pilot on the night of 16 December. Thermal satellite data showed that this flow reached 2 km to the NW. High-resolution radar satellite images over the 15-17th showed that the lava flow had advanced out to 2.5 km and had developed levees along the margins (figure 22). The lava channel was 5-15 m wide and was originating from a crater at the base of the summit scoria cone, which had been rebuilt since the collapse the previous week. Minor ash emissions drifted to the south on the 19tt and 20th (figure 23).

Figure (see Caption) Figure 22. TerraSAR-X radar satellite images of Shishaldin on 15 and 17 December 2019 show the new lava flow on the NW flank and growth of a scoria cone at the summit. The lava flow had reached around 2.5 km at this point and was 5-15 m wide with levees visible along the flow margins. Pyroclastic flow deposits from a scoria cone collapse event on 12 December are on the N flank. Figure courtesy of Simon Plank (German Aerospace Center, DLR) and Hannah Dietterich (AVO).
Figure (see Caption) Figure 23. Geologist Janet Schaefer (AVO/DGGS) collects ash samples within ice and snow on the southern flanks of Shishaldin on 20 December 2019. A weak ash plume is rising from the summit crater. Photo courtesy of Wyatt Mayo, AVO.

On 21 December a new lava flow commenced, traveling down the northern slope and accompanied by minor ash emissions. Continued lava extrusion was indicated by thermal data on the 25th and two lava flows reaching 1.5 km and 100 m were observed in satellite data on the 26th, as well as ash deposits on the upper flanks (figure 24). Weak explosions were detected by the regional infrasound network the following day. A satellite image acquired on the 30th showed a thick steam plume obscuring the summit and snow cover on the flanks indicating a pause in ash emissions.

Figure (see Caption) Figure 24. This 26 December 2019 WorldView-2 satellite image with a close-up of the Shishaldin summit area to the right shows a lava flow extending nearly 1.5 km down the NW flank and a smaller 100-m-long lava flow to the NE. Volcanic ash was deposited around the summit, coating snow and ice. Courtesy of Matt Loewen, AVO.

In early January satellite data indicated slow lava extrusion or cooling lava flows (or both) near the summit. On the morning of the 3rd an ash plume rose to 6-7 km altitude and drifted 120 km E to SE, producing minor amounts of volcanic lightning. Elevated surface temperatures the previous week indicated continued lava extrusion. A satellite image acquired on 3 January showed lava flows extending to 1.6 km NW, pyroclastic flows moving 2.6 km down the western and southern flanks, and ashfall on the flanks (figure 25).

Figure (see Caption) Figure 25. This WorldView-2 multispectral satellite image of Shishaldin, acquired on 3 January 2019, shows the lava flows reaching 1.6 km down the NW flank and an ash plume erupting from the summit dispersing to the SE. Ash deposits cover snow on the flanks. Courtesy of Hannah Dietterich, AVO.

On 7 January the most sustained explosive episode for this eruption period occurred. An ash plume rose to 7 km altitude at 0500 and drifted east to northeast then intensified reaching 7.6 km altitude with increased ash content, prompting an increase of the Aviation Color Code to Red and Volcano Alert Level to Warning. The plume traveled over 200 km to the E to NE (figure 26). Lava flows were produced on the northern flanks and trace amounts of ashfall was reported in communities to the NE, resulting in several flight cancellations. Thermal satellite images showed active lava flows extruding from the summit vent (figure 27). Seismicity significantly decreased around 1200 and the alert levels were lowered to Orange and Watch that evening. Through the following week no notable eruptive activity occurred. An intermittent steam plume was observed in webcam views.

Figure (see Caption) Figure 26. This Landsat 8 satellite image shows a detached ash plume drifts to the NE from an explosive eruption at Shishaldin on 7 January 2020. Courtesy of Chris Waythomas, AVO.
Figure (see Caption) Figure 27. This 7 January 2019 Sentinel-2 thermal satellite image shows several lava flows on the NE and NW flanks of Shishaldin, as well as a steam plume from the summit dispersing to the NE. Blue is snow and ice in this false color image (bands 12, 11, 4). Courtesy of Sentinel-Hub playground.

Eruptive activity resumed on 18 January with lava flows traveling 2 km down the NE flank accompanied by a weak plume with possible ash content dispersing to the SW (figure 28). A steam plume was produced at the front of the lava flow and lahar deposits continued to the north (figures 29 to 32). Activity intensified from 0030 on the 19th, generating a more ash-rich plume that extended over 150 km E and SE and reached up to 6 km altitude; activity increased again at around 1500 with ash emissions reaching 9 km altitude. AVO increased the alert levels to Red/Warning. Lava flows traveled down the NE and N flanks producing meltwater lahars, accompanied by elevated seismicity (figures 33). Activity continued through the day and trace amounts of ashfall were reported in False Pass (figure 34). Activity declined to small explosions over the next few days and the alert levels were lowered to Orange/watch shortly after midnight. The next morning weak steam emissions were observed at the summit and there was a thin ash deposit across the entire area. Satellite data acquired on 23 January showed pyroclastic flow deposits and cooling lava flows on the northern flank, and meltwater reaching the northern coast (figure 35).

Figure (see Caption) Figure 28. This Worldview-3 multispectral near-infrared satellite image acquired on 18 January 2020 shows a lava flow down the NE flank of Shishaldin. A steam plume rises from the end of the flow and lahar deposits from snowmelt travel further north. Courtesy of Matt Loewen, AVO.
Figure (see Caption) Figure 29. Steam plumes from the summit of Shishaldin and from the lava flow down the NE flank on 18 January 2020. Lahar deposits extend from the lava flow front and towards the north. Photo courtesy of Matt Brekke, via AVO.
Figure (see Caption) Figure 30. A lava flow traveling down the NE flank of Shishaldin on 18 January 2020, seen from Cold Bay. Photo courtesy of Aaron Merculief, via AVO.
Figure (see Caption) Figure 31. Two plumes rise from Shishaldin on 18 January 2020, one from the summit crater and the other from the lava flow descending the NE Flank. Photos courtesy of Woodsen Saunders, via AVO.
Figure (see Caption) Figure 32. A low-altitude plume from Shishaldin on the evening of 18 January 2020, seen from King Cove. Photo courtesy of Savannah Yatchmeneff, via AVO.
Figure (see Caption) Figure 33. This WorldView-2 near-infrared satellite image shows a lava flow reaching 1.8 km down the N flank and lahar deposits filling drainages out to the Bering Sea coast (not shown here) on 19 January 2020. Ash deposits coat snow to the NE and E. Courtesy of Matt Loewen, AVO.
Figure (see Caption) Figure 34. An ash plume (top) and gas-and-steam plumes (bottom) at Shishaldin on 19 January 2020. Courtesy of Matt Brekke, via AVO.
Figure (see Caption) Figure 35. A Landsat 8 thermal satellite image (band 11) acquired on 23 January 2019 showing hot lava flows and pyroclastic flow deposits on the flanks of Shishaldin and the meltwater flow path to the Bering Sea. Figure courtesy of Christ Waythomas, AVO.

Activity remained low in late January with some ash resuspension (due to winds) near the summit and continued elevated temperatures. Seismicity remained above background levels. Infrasound data indicated minor explosive activity during 22-23 January and small steam plumes were visible on 22, 23, and 26 January. MIROVA thermal data showed the rapid reduction in activity following activity in late-January (figure 36).

Figure (see Caption) Figure 36. MIROVA thermal data showing increased activity at Shishaldin during August-September, and an even higher thermal output during late-October 2019 to late January 2020. Courtesy of MIROVA.

Geologic Background. The beautifully symmetrical Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steam plume often rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the W and NE sides at 1,500-1,800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of Strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667 USA (URL: https://avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA (URL: http://dggs.alaska.gov/); Simon Plank, German Aerospace Center (DLR) German Remote Sensing Data Center, Geo-Risks and Civil Security, Oberpfaffenhofen, 82234 Weßling (URL: https://www.dlr.de/eoc/en/desktopdefault.aspx/tabid-5242/8788_read-28554/sortby-lastname/); 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/); Planet Labs, Inc. (URL: https://www.planet.com/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Nevados de Chillan (Chile) — January 2020 Citation iconCite this Report

Nevados de Chillan

Chile

36.868°S, 71.378°W; summit elev. 3180 m

All times are local (unless otherwise noted)


Many explosions, ash plumes, lava and pyroclastic flows June-December 2019

Nevados de Chillán is a complex of late-Pleistocene to Holocene stratovolcanoes in the Chilean Central Andes. An eruption started with a phreatic explosion and ash emission on 8 January 2016 from a new crater (Nicanor) on the E flank of the Nuevo crater, which lies on the NW flank of the cone of the large stratovolcano referred to as Volcán Viejo. Strombolian explosions and ash emissions continued throughout 2016 and 2017; a lava dome within the Nicanor crater was confirmed in early January 2018. Explosions and pyroclastic flows continued during 2018 and the first half of 2019. This report covers continuing activity from June-December 2019 when ongoing explosive events produced ash plumes, lava, and pyroclastic flows. Information for this report is provided primarily by Chile's Servicio Nacional de Geología y Minería (SERNAGEOMIN)-Observatorio Volcanológico de Los Andes del Sur (OVDAS), and by the Buenos Aires Volcanic Ash Advisory Center (VAAC).

Nevados de Chillán was relatively quiet during June 2019, generating only a small number of explosions with ash plumes. This activity continued during July; some events produced incandescent ejecta around the crater. By August a distinct increase in activity was noticeable; ash plumes were larger and more frequent, and incandescent ejecta rose hundreds of meters above the summit a number of times. Frequent explosions were typical during September; the first of several blocky lava flows emerged from the crater mid-month. Inflation that began in mid-July continued with several centimeters of both horizontal and vertical displacement. By October, pyroclastic flows often accompanied the explosive events in addition to the ash plumes, and multiple vents opened within the crater. Three more lava flows had appeared by mid-November; explosions continued at a high rate. Activity remained high at the beginning of December but dropped abruptly mid-month. MODVOLC measured three thermal alerts in September, two in October, seven in November, and six in December. This period of increased thermal activity closely matches the thermal anomaly data reported by the MIROVA project (figure 37), which included an increase at the end of August 2019 that lasted through mid-December before stopping abruptly. Several lava flows and frequent explosions with incandescent ejecta and pyroclastic flows were reported throughout the period of increased thermal activity.

Figure (see Caption) Figure 37. MIROVA thermal anomaly data for Nevados de Chillán from 3 February through December 2019 show low activity during June-August and increasing activity from August through mid-December. This correlates with ground and satellite observations of lava flows, incandescent explosions, ash plumes, and pyroclastic flows during the period of increased thermal activity. Courtesy of MIROVA.

Activity during June-August 2019. Nevados de Chillán remained relatively quiet during June 2019 with a few explosions of ash. At the active Nicanor crater, located on the E flank of the Volcán Nuevo dome, predominantly white steam plumes were observed daily in the nearby webcams. The growth rate of the dome inside the crater was reported by SERNAGEOMIN as continuing at about 260 m3/day. They noted an explosion on 3 June; the Buenos Aires VAAC reported a puff of ash seen from the webcam drifting SE at 3.7 km altitude (figure 38). The webcam indicated sporadic weak emissions continuing that day and the next. Minor explosions were also reported on 7-8 June and included incandescence observed at night and ejecta deposited around the crater rim. The Buenos Aires VAAC reported a narrow ash plume drifting ENE in multispectral imagery under clear skies late on 7 June. The webcams showed sporadic emissions of ash at 3.4 km altitude on 19 June that dissipated rapidly.

Figure (see Caption) Figure 38. Explosions at Nevados de Chillán on 3 (left) and 20 (right) June 2019 produced ash plumes that quickly dissipated in the strong winds. Courtesy of the SERNAGEOMIN Portezuelo webcam, Pehuenia Online (left) and Eco Bio Bio La Red Informativa (right).

Minor pulsating explosive activity continued during July 2019 with multiple occurrences of ash emissions. Ash emissions rose to 3.7 km altitude on 4 July and were seen in the SERNAGEOMIN webcam; the VAAC reported an emission on 8 July that rose to 4.3 km altitude and drifted SE. Monitoring stations near the complex recorded an explosive event early on 9 July; incandescence with gases and ejecta were deposited around the crater and an ash plume rose to 3.9 km and drifted SE. Small ash plumes from sporadic puffs on 12 July rose to 4.6 km altitude. An explosive event on 14 July also produced incandescent ejecta around the crater along with weak sporadic ash emissions. Single ash emissions on 18 (figure 39) and 22 July at 3.7 km altitude drifted ESE from summit before dissipating; another emission on 26 July was reported at 4.3 km altitude.

Figure (see Caption) Figure 39. Local news sources reported ash emissions at Nevados de Chillán on 18 July 2019. Courtesy of INF0SCHILE (left) and Radio Ñuble (right).

A distinct increase in the intensity and frequency of explosive activity was recorded during August 2019. SERNAGEOMIN noted ash emissions and explosions during 3-4 August in addition to the persistent steam plumes above the Nicanor crater (figure 40). The Buenos Aires VAAC reported a single puff on 3 August that was seen in the webcam rising to 3.9 km altitude and dissipating quickly. The next day a pilot reported an ash plume estimated at 5.5 km altitude drifting E. It was later detected in satellite imagery; the webcam revealed continuous emission of steam and gas with intermittent puffs of ash. SERNAGEOMIN issued a special report (REAV) on 6 August noting the increase in size and frequency of explosions, some of which produced dense ash plumes that rose 1.6 km above the crater along with incandescent ejecta. They also reported that satellite imagery indicated a 1.5-km-long lahar that traveled down the NNE flank as a result of the interaction of the explosive ejecta with the snowfall near the summit.

Figure (see Caption) Figure 40. Climbers captured video of a significant explosion at Nevados de Chillán on 4 August 2019. Courtesy of CHV Noticias.

Beginning on 9-10 August 2019, and continuing throughout the month, SERNAGEOMIN observed explosive nighttime activity with incandescent ejecta scattered around the crater rim along with moderate levels of seismicity each day. A diffuse ash plume was detected in satellite imagery by the VAAC on 9 August drifting NW at 4.9 km altitude. SERNAGEOMIN issued a new warning on 12-13 August that the recent increase in activity since the end of July suggested the injection of a new magmatic body that could lead to larger explosive events with pyroclastic and lava flows. They reported pyroclastic ejecta from multiple explosions on 13 August rising 765 and 735 m above the crater. Drone images taken between 4 and 12 August showed the destruction of the summit dome from multiple explosions with the Nicanor Crater (figure 41). The VAAC reported sporadic pulses of volcanic ash drifting N during 12-14 August, visible in satellite imagery estimated at 4.3 km altitude. By 17-18 August, they noted constant steam emissions interspersed with gray plumes during explosive activity.

Figure (see Caption) Figure 41. Drone images taken at Nevados de Chillán between 4 and 12 August 2019 showed destruction of the dome caused by multiple explosions at the summit crater. Courtesy of Movisis.org Internacional.

An increase in seismicity, especially VT events, during 21-22 August 2019 resulted in multiple special REAV reports from SERNAGEOMIN. They noted on 21 August that an explosion produced gas emissions and pyroclastic material that rose 1,400 m above the crater; the next day material rose 450 m. That night, in addition to incandescent ejecta around the crater, they reported small high-temperature flows on the N flank which extended to the NNE flank a few days later. The VAAC reported pulses of ash plumes moving SE on 22 August at 4.3 km altitude. A faint ash cloud was visible in satellite imagery on 29 August drifting E at 3.7 km altitude (figure 42). The cloud was dissipating rapidly as it moved away from the summit. Sporadic ash emissions from intermittent explosions continued moving ESE then N and NE; they were reported daily through 5 September. They continued to rise in altitude to 3.9 km on 30 August, 4.3 km on 1 September, and 4.6 km on 3 September.

Figure (see Caption) Figure 42. Incandescence at the summit of Nevados de Chillán and ashfall covering snow to the E was captured in Sentinel-2 satellite imagery on 29 August 2019. Courtesy of Copernicus EMS.

Activity during September-October 2019. Frequent explosions from Nicanor crater continued during September 2019, producing numerous ash plumes and small high-temperature flows along the NNE flank. A webcam detected a small lateral vent on the NNE flank about 50 m from the crater rim emitting gas and particulates on 2-3 September. Multiple explosions during 3-5 September were associated with gas and ash emissions and incandescent ejecta deposited around the crater rim (figure 43). The network of GNSS stations recording deformation of the volcanic complex confirmed on 3-4 September that inflation, which had been recorded since mid-July 2019, was continuing at a rate of about 1 cm/month. Blocks of incandescent ejecta from numerous explosions were observed rolling down the N flank on 6-7 September and the E flank the following night.

Figure (see Caption) Figure 43. Activity at Nevados de Chillán on 3 September 2019 included ash and steam explosions (left) and incandescent ejecta at the summit (right). Courtesy of Carlos Bustos and SERNAGEOMIN webcams.

SERNAGEOMIN reported on 9-10 September that satellite imagery revealed a new surface deposit about 130 m long trending NNE from the center of crater. They reported an increase in the level of seismicity from moderate to high on 10-11 September and observed incandescent ejecta at the summit during several explosions (figure 44). During a flyover on 12 September scientists confirmed the presence of a new blocky lava flow emerging from Nicanor Crater and moving down the NNE flank of Nuevo volcano. The flow was about 600 m long, 100 m wide, and 5 m thick with a blocky surface and incandescent lava at the base within the active crater. Measurements with a thermal camera indicated a temperature around 800°C within the active crater, and greater than 100°C on the surface of the flow. Frequent high-energy explosions that day produced incandescent ejecta that could be seen from Las Trancas and Shangri-La (figure 45). Ashfall 0.5 cm thick was reported 2 km from the volcano to the SW. The flow was visible from the webcam located N of Nicanor on 16-17 September. Satellite imagery indicated the flow was about 550 m long and moving at a rate of about 21 m/day.

Figure (see Caption) Figure 44. A blocky lava flow moved down the NNE flank of Nevados de Chillán on 11 September (left); incandescent ejecta covered the summit area the next night (right). Courtesy of EarthQuakesTime (left), Red Geocientifica de Chile (right) and SERNAGEOMIN Webcams.
Figure (see Caption) Figure 45. The SERNAGEOMIN Portezuelo webcam revealed the blocky lava flow, incandescent ejecta and ash emissions at Nevados de Chillán on 12 September 2019. Courtesy of American Earthquakes (left), PatoArias (right), and SERNAGEOMIN.

During 18-22 September 2019 multiple special reports of seismicity were released each day with incandescent ejecta, gas, and particulate emissions often observed at the summit crater; the lava flow remained active. On 24 September ashfall was reported about 15 km NW in communities including Las Trancas; small pyroclastic flows were observed the following day. Horizontal inflation of 2.4 cm was reported on 25 September, and vertical inflation was measured at 3.4 cm since mid-July. SERNAGEOMIN noted that while the frequency of explosions had increased, the energy released had decreased. Morphological changes in Nicanor crater suggested that it was growing at its SW edge and eroding the adjacent Arrau crater; the NE edge of the crater was unstable.

Plumes of steam and ash continued along with the explosions for the remainder of the month. During the night, incandescent ejecta was observed, and the low-velocity lava flow continued to move. Multiple VAAC reports were issued virtually every day of September. Pulses of ash were moving SE at 4.3 km altitude on 7-8 September. For most of the rest of the month sporadic emissions with minor amounts of ash were observed in either the webcam or satellite images at an altitude of 3.7 km, occasionally rising to 4.3 km. They drifted generally SE but varied somewhat with the changing winds. Continuous ash emissions were observed during 24-25 September that rose as high as 4.9 km altitude and drifted E, clearly visible in satellite imagery. After that, the altitude dropped back to 3.7 km and the plume was only faintly and intermittently visible in satellite imagery.

Low-altitude gray ash plumes were observed rising from Nicanor crater almost every day that weather permitted during October 2019. Incandescent ejecta was frequently observed at night. Beginning on 6-7 October, SERNAGEOM reported pyroclastic flows traveling short distances from the crater most days. They traveled 1.13 km down the NNE flank, 0.42 km down the NNW flank and 0.88 km down the SW flank. The blocky lava flow on the NNE flank was no longer active (figure 46). During 9-12 October, multiple special reports of increased seismic activity (REAVs) were issued each day. Inflation continued throughout the month. On 10 October the total horizontal deformation (since mid-July) was 3 cm, with a rate of movement a little over 1 cm/month; the total vertical displacement was 4.5 cm, with a rate of 1.93 cm/month during the previous 30 days.

In a special report issued on 11 October, SERNAGEOMIN mentioned that analysis of satellite imagery indicated a new emission center within the Nicanor crater adjacent to the dome vent active since December 2017 and to the lava flow of September. The new center was oval shaped with an E-W dimension of 60 m and a N-S dimension of 55 m, located about 90 m SE of the old, still active center, and was the site of the explosive activity reported since 30 September.

Figure (see Caption) Figure 46. Drone footage posted 10 October 2019 from Nevados de Chillán shows steam emissions from the Nicanor crater and a blocky lava flow down NNE flank. The snow-covered cone in background is Volcan Baños. Courtesy of Volcanologia Chile and copyright by Nicolas Luengo V.

On 16 October a new blocky flow was observed on the NE flank of the Nicanor Crater; it was about 70 m long, moving about 30 m/day. By 21 October it had reached 130 m in length, and its rate of advance had slowed significantly. Beginning on 25 October seismicity decreased noticeably and much less surface activity was observed at the crater. Explosions at the end of the month produced steam plumes, gas emissions and minor pulsating ash emissions.

The Buenos Aires VAAC reported a puff of ash at 4.9 km altitude on 1 October moving SE. Continuous emission of steam and gas with sporadic puffs of ash that rose to around 3.7-4.3 km altitude were typical every day after that until 25 October usually drifting S or E; they were most often visible in the webcams, and occasionally visible in satellite imagery when weather conditions permitted. A diffuse plume of ash was detected on 16 October drifting SE at 4.6 km altitude. The VAAC reported incandescence visible at the summit in webcam images on 22 October; a significant daytime explosion on 24 October produced a large incandescent ash cloud (figure 47). The next day the VAAC detected weak pulses of ash plumes in satellite images extending E from the summit for 130 km. Intermittent ash emissions were reported drifting SE at 3.7-4.3 km each day from 29-31 October.

Figure (see Caption) Figure 47. A large incandescent ash plume at Nevados de Chillán on 24 October 2019 sent ejecta around the summit (left); a dense ash plume was produced during an explosion on 30 October 2019 (right). Courtesy of Cristian Farian (left) and SERNAGEOMIN (right); both images taken from the SERNAGEOMIN webcams.

Activity during November-December 2019. Moderate seismicity continued during November 2019 with recurrent episodes of pulsating gas and ash emissions. Incandescent ejecta was visible many nights that the weather conditions were favorable (figure 48). In the Daily Report (RAV) issued on 6 November, SERNAGEOMIN noted that the original 700-m-long blocky lava flow on the NNE flank active during September had been partly covered by another flow, about 350 m long. They also reported that pyroclastic density currents were observed in the area immediately around the crater extending in several directions. They extended 850 m down the SW flank, 670 m down the NW flank, 1,680 m down the N flank, and 440 m to the NNE.

Changes in the crater area indicated a growth of the SW edge of the Nicanor Crater, continuing to erode the Arrau crater, with the constant emission of gas, ash, and incandescent ejecta that produced plumes up to 1.8 km high. SERNAGEOMIN also observed activity from a vent at the NE edge of the crater that included gas emission and ejecta, but no lava flow. The fourth lava flow observed in recent months (L4) was identified on the NNE slope on 13 November adjacent to the earlier flows; it was about 70 m long and slowly advancing. By 19 November L4 consisted of two lobes and extended about 90 m from the edge of the Nicanor crater advancing at an average rate of 0.4 m/hour. The vent producing L4 was located about 60 m SSE of the vent that produced the earlier flows (L1, L2, and L3). By 28 November the flow had reached a length of 165 m and was no longer advancing. A series of explosions reported on 25-27 and 30 November produced ejecta that rose 800, 1,000, 1,300, and 700 m above the crater.

Figure (see Caption) Figure 48. Incandescent ejecta at Nevados de Chillán was clearly visible at night on 3 November 2019. Courtesy of Claudio Kanisius.

Ash emissions were reported by the Buenos Aires VAAC during most of November, usually visible from the webcams, but often also seen in satellite imagery. The plumes generally reached 3.7-4.6 km altitude and drifted SSE. They usually occurred as continuous emission of steam and gas accompanied by sporadic pulses of ash but were sometimes continuous ash for several hours. They were visible about 100 km E of the summit on 2 November, and over 200 km SE the following day. A narrow plume of ash was seen in visual satellite imagery extending 50 km E of the summit on 9 November. Intermittent incandescence at the summit was seen from the webcam on 18 November. Pulses of ash were detected in satellite imagery extending 125 km SE on 22 November. Strong puffs of ash briefly rose to 4.9 km altitude and drifted NE on 26 November (figure 49); incandescence during the nighttime was visible in the webcam on 28 November.

Figure (see Caption) Figure 49. An explosion on 26 November 2019 at Nevados de Chillán produced a dense ash plume and small pyroclastic flows down the flank. Courtesy of Volcanes de Chile and the SERNAGEOMIN Portezuelo webcam.

Pulsating emissions of gas and ejecta continued into December 2019. Five explosions were reported on 1 December that produced gas plumes which rose 300-800 m above the crater. Three more explosions occurred on 3 December sending gas plumes 500-1,000 m high. SERNAGEOMIN reported on 4 December that explosive activity was observed from four vents within the Nicanor crater. This activity triggered new pyroclastic flows that extended 1,100 m E and 400 m S. By 5 December the total vertical inflation reported since July was 8 cm. A large explosion on 5 December sent material 1.6 km above the summit and pyroclastic flows down the flanks (figure 50). The webcams at Andarivel and Portezuelo showed a pyroclastic flow moving 400 m W, a direction not previously observed; this was followed by additional pyroclastic flows to the N and E.

Figure (see Caption) Figure 50. A large explosion at Nevados de Chillán on 5 December 2019 produced an ash plume that rose 1.6 km above the summit and sent pyroclastic flows down the flanks. Courtesy of SERNAGEOMIN.

On 9 December SERNAGEOMIN noted that the increase to four active vents was causing erosion on the S and SE edges of the crater making the most affected areas to the SW, S, SE and E of the crater. Major explosions reported that day produced pyroclastic flows that descended down the E and ESE flanks and particulate emissions that rose 1 km. The SW flank near the crater was also affected by ejecta and pyroclastic debris carried by the wind. The most extensive pyroclastic flows travelled down the E flank for the next several days; explosions on 10 December sent material 1.2 km high. Three explosions were noted on 11 December; the first sent incandescence close to 200 m high, and the second produced a column of particulate material 1.2 km high. The first of two explosions on 12 December sent material 1.8 km above the crater and pyroclastic flows down the flanks (figure 51). Although explosions were reported on 13 and 14 December, cloudy skies prevented observations of the summit.

Figure (see Caption) Figure 51. A large explosion at Nevados de Chillán on 12 December 2019 produced an ash plume that rose 1.8 km above the summit and sent pyroclastic flows down the flanks. Courtesy of Volcanes de Chile and SERNAGEOMIN.

Intermittent ash emissions were reported by the Buenos Aires VAAC during 1-13 December 2019. They rose to 3.7-4.3 km and drifted generally E. Pulses of ash were detected at 4.9 km altitude moving S in satellite imagery on 9 December. The last reported ash emission for December was on the afternoon of 12 December; puffs of ash could be seen in satellite imagery moving E at 4.6 km altitude. A decrease in particulate emissions and explosions was reported beginning on 14 December, and no further explosions were recorded by infrasound devices after 15 December. The deposits from the earlier pyroclastic flows had reached 600 m E and 300 m W of the crater. Seismic activity was recorded as low instead of moderate beginning on 25 December. A total horizontal inflation of about 6 cm since July was measured at the end of December.

Geologic Background. The compound volcano of Nevados de Chillán is one of the most active of the Central Andes. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, Cerro Blanco (Volcán Nevado), is located at the NW end of the group. Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in elevation. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986 and eventually exceeded its height.

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/), Twitter: @Sernageomin; 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/); Cristian Farias Vega, Departamento de Obras Civiles y Geología, Universidad Católica de Temuco, Vilcún, Región de La Araucanía, Chile (URL: https://twitter.com/cfariasvega/status/1187471827255226370); Copernicus Emergency Management Service (Copernicus EMS), Joint Research Centre, European Union (URL: https://emergency.copernicus.eu/, https://twitter.com/CopernicusEMS/status/1168156474817818624); Volcanes de Chile, Proyectos de la Fundación Volcanes de Chile, Chile (URL: https://www.volcanesdechile.net/, https://twitter.com/volcanesdechile/status/1199496839491395585); Pehuenia Online, Pehuenia, Argentina (URL: http://pehueniaonline.com.ar/, https://twitter.com/PehueniaOnline/status/1135703309824745472); Eco Bio Bio La Red Informativa, Bio Bio Region, Chile (URL: http://emergenciasbiobio.blogspot.com/, https://twitter.com/Eco_BioBio_II/status/1141734238590574593); INF0SCHILE (URL: https://twitter.com/INF0SCHILE/status/1151849611482599425); Radio Ñuble AM y FM, Chillán, Chile (URL: http://radionuble.cl/linea/, lhttps://twitter.com/RadioNuble/status/1151858189299781632); CHV Noticias, Santiago, Chile (URL: https://www.chvnoticias.cl/, https://twitter.com/CHVNoticias/status/1159263718015819777); Movisis.org Internacional, Manabi, Ecuador (URL: https://movisis.org/, https://twitter.com/MOVISISEC/status/1160778823031558144); Carlos Bustos (URL: https://twitter.com/cbusca1970/status/1168932243873644548); EarthQuakesTime (URL: https://twitter.com/EarthQuakesTime/status/1171654504841908229); Red Geocientifica de Chile (URL: https://twitter.com/RedGeoChile/status/1171972482875703296); American Earthquakes (URL: https://twitter.com/earthquakevt/status/1172271139760091136); PatoArias, Talca, Chile (URL: https://twitter.com/patoarias/status/1172287142191665153); Volcanologia Chile, (URL: http://www.volcanochile.com/joomla30/, https://twitter.com/volcanologiachl/status/1182707451554078720); Claudio Kanisius (URL: https://twitter.com/ClaudioKanisius/status/1191182878346031104).


Asosan (Japan) — January 2020 Citation iconCite this Report

Asosan

Japan

32.884°N, 131.104°E; summit elev. 1592 m

All times are local (unless otherwise noted)


Intermittent ash plumes and elevated SO2 emissions continue during July-December 2019

The large Asosan caldera reaches around 23 km long in the N-S direction and contains a complex of 17 cones, of which Nakadake is the most active (figure 58). A recent increase in activity prompted an alert level increase from 1 to 2 on 14 April 2019. The Nakadake crater is the site of current activity (figure 59) and contains several smaller craters, with the No. 1 crater being the main source of activity during July-December 2019. The activity during this period is summarized here based on reports by the Japan Meteorological Agency and satellite data.

Figure (see Caption) Figure 58. Asosan is a group of cones and craters within a larger caldera system. January 2010 Monthly Mosaic images copyright Planet Labs 2019.
Figure (see Caption) Figure 59. Hot gas emissions from the Nakadake No. 1 crater on 25 June 2019 reached around 340°C. Courtesy of the Japan Meteorological Agency (July 2019 monthly report).

Small explosions were observed at the No. 1 vent on the 4, 5, 9, 13-16, and 26 July. There was an increase in thermal energy detected near the vent leading to a larger event on the 26th (figures 60 and 61), which produced an ash plume up to 1.6 km above the crater rim and continuing from 0757 to around 1300 with a lower plume height of 400 m after 0900. Light ashfall was reported downwind. Elevated activity was noted during 28-29 July, and an ash plume was seen in webcam footage on the 30th. Incandescence was visible in light-sensitive cameras during 4-17 and after the 26th. A field survey on 5 July measured 1,300 tons of sulfur dioxide (SO2) per day. This had increased to 2,300 tons per day by the 12th, 2,500 on the 24th, and 2,400 by the 25th. A sulfur dioxide plume was detected in Sentinel-5P/TROPOMI satellite data acquired on 28 July (figure 62).

Figure (see Caption) Figure 60. Thermal images taken at Asosan on 26 July 2019 show the increasing temperature of emissions leading to an explosion. Courtesy of the Japan Meteorological Agency (July 2019 monthly report).
Figure (see Caption) Figure 61. An eruption from the Nakadake crater at Asosan on 26 July 2019. Courtesy of the Japan Meteorological Agency (July 2019 monthly report).
Figure (see Caption) Figure 62. A sulfur dioxide plume was detected from Asosan (to the left) on 28 July 2019. The larger plume (red) to the right is not believed to be associated with volcanism in this area. NASA Sentinel-5P/TROPOMI satellite image courtesy of the NASA Goddard Space Flight Center.

The increased eruptive activity that began on 5 July continued to 16 August. There were 24 eruptions recorded throughout the month, with eruptions occurring on 18-23, 25, and 29-31 August. An ash plume at 2100 on 4 August reached 1.5 km above the crater rim. Detected SO2 increased to extremely high levels from late July to early August with 5,200 tons per day recorded on 9 August, but which then reduced to 2,000 tons per day. Ashfall occurred out to around 7 km NW on the 10th (figure 63). Activity continued to increase at the Nakadake No. 1 crater, producing incandescence. High-temperature gas plumes were detected at the No. 2 crater.

Figure (see Caption) Figure 63. Ashfall from Asosan on 10 August 2019 near Otohime, Aso city, which is about 7 km NW of the Nakadake No. 1 crater that produced the ash plume. The ashfall was thick enough that the white line in the parking lot was mostly obscured (lower photo). Courtesy of the Japan Meteorological Agency (August 2019 monthly report).

Thermal activity continued to increase, and incandescence was observed at the No. 1 crater throughout September. There were 24 eruptions recorded throughout August. Light ashfall occurred out to around 8 km NE on the 3rd and ash plumes reached 1.6 km above the crater rim during 10-13, and again during 25-30 (figures 64 and 65). During the later dates ashfall was reported to the NE and NW. The SO2 levels were back down to 1,600 tons per day by 11 September and increased to 2,600 tons per day by the 26th.

Figure (see Caption) Figure 64. Ash plumes at Asosan on 29 September 2019. Courtesy of Volcanoverse.
Figure (see Caption) Figure 65. Activity at Asosan in late September 2019. Left: incandescence and a gas plume at the Nakadake No. 1 crater on the 28th. Right: an eruption produced an ash plume at 0839 on the 30th. Aso Volcano Museum surveillance camera image (left) and Kusasenri surveillance camera image (right) courtesy of the Japan Meteorological Agency (September 2019 monthly report).

Similar elevated activity continued through October with ash plumes reaching 1.3 km above the crater and periodic ashfall reported at the Kumamoto Regional Meteorological Observatory, and out to 4 km S to SW on the 19th and 29th. Temperatures up to 580°C were recorded at the No. 1 crater on 23 October and incandescence was occasionally visible at night through the month (figure 66). Gas surveys detected 2,800 tons per day of SO2 on 7 October, which had increased to 4,000 tons per day by the 11th.

Figure (see Caption) Figure 66. Drone images of the Asosan Nakadake crater area on 23 October 2019. The colored boxes show the same vents and the photographs on the left correlate to the thermal images on the right. The yellow box is around the No. 1 crater, with temperature measurements reaching 580°C. The emissions in the red box reached 50°C, and up to 100°C on the southwest crater wall (blue box). Courtesy of the Japan Meteorological Agency (October 2019 monthly report).

Ash plume emission continued through November (figure 67 and 68). Plumes reached 1.5 to 2.4 km above sea level during 13-18 November and ashfall occurred downwind, with a maximum of 1.4 km above the crater rim for the month. Ashfall was reported near Aso City Hall on the 27th. Incandescence was observed until 6 November. During the first half of October sulfur dioxide emissions were slightly lower than the previous month, with measurements detecting under 3,000 tons per day. In the second half of the month emissions increased to 2,000 to 6,300 tons per day. This was accompanied by an increase in volcanic tremor.

Figure (see Caption) Figure 67. Examples of ash plumes at Asosan on 2, 8, 9, and 11 November 2019. The plume on 2 November reached 1.3 km above the crater rim. Kusasenri surveillance camera images courtesy of the Japan Meteorological Agency.
Figure (see Caption) Figure 68. Ash emissions from the Nakadake crater at Asosan on 15 and 17 November 2019. The continuous ash emission is weak and is being dispersed by the wind. Copyright Mizumoto, used with permission.

Throughout December activity remained elevated with ash plumes reaching 1.1 km above the Nakadake No. 1 crater and producing ashfall. The maximum gas plume height was 1.8 km above the crater. A total of 23 eruptions were recorded, and incandescence at the crater was observed through the month. Sulfur dioxide emissions continued to increase with 5,800 tons per day recorded on the 27th, and 7,400 tons per day recorded on the 31st.

Overall, eruptive activity has continued intermittently since 26 July and SO2 emissions have increased through the year. Incandescence was seen at the crater since 2 October and this is consistent with an increase in thermal energy detected by the MIROVA algorithm around that time (figure 69).

Figure (see Caption) Figure 69. Thermal anomalies were low through 2019 with a notable increase around October to November. Log radiative power plot courtesy of MIROVA.

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: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Planet Labs, Inc. (URL: https://www.planet.com/); Mizumoto, Kumamoto, Kyushu, Japan (Twitter: https://twitter.com/hepomodeler); Volcanoverse (URL: https://www.youtube.com/channel/UCi3T_esus8Sr9I-3W5teVQQ).


Tinakula (Solomon Islands) — January 2020 Citation iconCite this Report

Tinakula

Solomon Islands

10.386°S, 165.804°E; summit elev. 796 m

All times are local (unless otherwise noted)


Intermittent thermal activity suggests ongoing eruption, July-December 2019

Remote Tinakula lies 100 km NE of the Solomon Trench at the N end of the Santa Cruz Islands, which are part of the South Pacific country of the Solomon Islands located 400 km to the W. It has been uninhabited since an eruption with lava flows and ash explosions in 1971 when the small population was evacuated (CSLP 87-71). The nearest communities live on Te Motu (Trevanion) Island (about 30 km S), Nupani (40 km N), and the Reef Islands (60 km E); residents occasionally report noises from explosions at Tinakula. Ashfall from larger explosions has historically reached these islands. A large ash explosion during 21-26 October 2017 was a short-lived event; renewed thermal activity was detected beginning in December 2018 and intermittently throughout 2019. This report covers the ongoing activity from July-December 2019. Since ground-based observations are rarely available, satellite thermal and visual data are the primary sources of information.

MIROVA thermal anomaly data indicated intermittent but ongoing thermal activity at Tinakula during July-December 2019 (figure 35). It was characterized by pulses of multiple alerts of varying intensities for several days followed by no activity for a few weeks.

Figure (see Caption) Figure 35. The MIROVA project plot of Radiative Power at Tinakula from 2 March 2019 through the end of the year indicated repeated pulses of thermal energy each month except for August 2019. It was characterized by pulses of multiple alerts for several days followed by no activity for a few weeks. Courtesy of MIROVA.

Observations using Sentinel-2 satellite imagery were often prevented by clouds during July, but two MODVOLC thermal alerts on 2 July 2019 corresponded to MIROVA thermal activity on that date. No thermal anomalies were reported by MIROVA during August 2019, but Sentinel-2 satellite images showed dense steam plumes drifting away from the summit on four separate dates (figure 36). Two distinct thermal anomalies appeared in infrared imagery on 9 September, and a dense steam plume drifted about 10 km NW on 14 September (figure 37).

Figure (see Caption) Figure 36. Sentinel-2 satellite imagery for Tinakula recorded ongoing steam emissions on multiple days during August 2019 including 10 August (left) and 20 August (right). The island is about 3 km in diameter. Left image is natural color rendering with bands 4,3,2, right image is atmospheric penetration with bands 12, 11, and 8a. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 37. A bright thermal anomaly at the summit and a weaker one on the nearby upper W flank of Tinakula on 9 September 2019 (left) indicated ongoing eruptive activity in Sentinel-2 satellite imagery. While no thermal anomalies were visible on 14 September (right), a dense steam plume originating from the summit drifted more than 10 km NW. Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

During October 2019 steam emissions were captured in four clear satellite images; a weak thermal anomaly was present on the W flank on 9 October (figure 38). MODVOLC recorded a single thermal alert on 9 November. Stronger thermal anomalies appeared twice during November in satellite images. On 13 November a strong anomaly was present at the summit in Sentinel-2 imagery; it was accompanied by a dense steam plume drifting NE from the hotspot. On 28 November two thermal anomalies appeared part way down the upper NW flank (figure 39). Thermal imagery on 3 December suggested that a weak anomaly remained on the NW flank in a similar location; a dense steam plume rose above the summit, drifting slightly SW on 18 December (figure 40). A thermal anomaly at the summit on 28 December was accompanied by a dense steam plume and corresponded to multiple MIROVA thermal anomalies at the end of December.

Figure (see Caption) Figure 38. A weak thermal anomaly was recorded on the upper W flank of Tinakula on 9 October 2019 in Sentinel-2 satellite imagery (left). Dense steam drifted about 10 km NW from the summit on 29 October (right). Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 39. On 13 November 2019 a strong anomaly was present at the summit of Tinakula in Sentinel-2 imagery; it was accompanied by a dense steam plume drifting NE from the hotspot (left). On 28 November two thermal anomalies appeared part way down the upper NW flank (right). Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 40. Thermal imagery on 3 December 2019 from Tinakula suggested that a weak anomaly remained in a similar location to one of the earlier anomalies on the NW flank (left); a dense steam plume rose above the summit, drifting slightly SW on 18 December (center). A thermal anomaly at the summit on 28 December was accompanied by a dense steam plume (right) and corresponded to multiple MIROVA thermal anomalies at the end of December. Atmospheric penetration rendering (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

Geologic Background. The small 3.5-km-wide island of Tinakula is the exposed summit of a massive stratovolcano at the NW end of the Santa Cruz islands. Similar to Stromboli, it has a breached summit crater that extends from the summit to below sea level. Landslides enlarged this scarp in 1965, creating an embayment on the NW coast. The satellitic cone of Mendana is located on the SE side. The dominantly andesitic volcano has frequently been observed in eruption since the era of Spanish exploration began in 1595. In about 1840, an explosive eruption apparently produced pyroclastic flows that swept all sides of the island, killing its inhabitants. Frequent historical eruptions have originated from a cone constructed within the large breached crater. These have left the upper flanks and the steep apron of lava flows and volcaniclastic debris within the breach unvegetated.

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


Ibu (Indonesia) — January 2020 Citation iconCite this Report

Ibu

Indonesia

1.488°N, 127.63°E; summit elev. 1325 m

All times are local (unless otherwise noted)


Frequent ash plumes and small lava flows in the crater through December 2019

Heightened continuing activity at Ibu since March 2018 has been dominated by frequent ash explosions with weak ash plumes, and numerous thermal anomalies reflecting one or more weak lava flows (BGVN 43:05, 43:12, and 44:07). This report summarizes activity through December 2019, and is based on data from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Darwin Volcanic Ash Advisory Centre (VAAC), and various satellites.

Typical ash plumes during the reporting period of July-December 2019 rose 800 m above the crater, with the highest reported to 1.4 km in early October (table 5). They were usually noted a few times each month. According to MAGMA Indonesia, explosive activity caused the Aviation Color Code to be raised to ORANGE (second highest of four) on 14, 22, and 31 August, 4 and 30 September, and 15 and 20 October.

Table 5. Ash plumes and other volcanic activity reported at Ibu during December 2018-December 2019. Plume heights are reported above the crater rim. Data courtesy of PVMBG and Darwin VAAC.

Date Time Ash Plume Height Plume Drift Remarks
11 Dec 2018 -- 500 m -- Weather clouds prevented views in satellite data.
12 Jan 2019 1712 800 m S --
13 Jan 2019 0801 800 m S --
05-12 Feb 2019 -- 200-800 m E, S, W Weather conditions occasionally prevented observations.
25-26 Feb 2019 -- 1.1-1.7 km NE, ENE Thermal anomaly.
28 Feb 2019 -- 800 m N --
18 Mar 2019 -- 1.1 km E Plume drifted about 17 km NE.
23 Mar 2019 -- 1.1 km E --
28 Mar 2019 -- 800 m SE --
10 Apr 2019 -- 800 m N --
15-16 Apr 2019 -- 1.1 km N, NE --
18 Apr 2019 -- 800 m E --
07 May 2019 -- 1.1 km ESE --
08 May 2019 -- 1.1 km ESE --
09 May 2019 1821 600 m S Seismicity characterized by explosions, tremor, and rock avalanches.
10 May 2019 -- 500 m ESE --
14 May 2019 1846 800 m N --
14-16, 18-19 May 2019 -- 0.8-1.7 km NW, N, ENE --
23-24 May 2019 -- 1.1-1.4 km SE --
31 May 2019 -- 800 m W --
02 Jun 2019 -- 1.7 km W --
21 Jun 2019 -- 500 m N, NE --
24-25 Jun 2019 -- 0.2-1.1 km SE, ESE --
06 Jul 2019 -- 800 m N Intermittent thermal anomaly.
15 Jul 2019 -- 800 m NE --
07-12 Aug 2019 -- 200-800 m -- Plumes were white-to-gray.
14 Aug 2019 1107 800 m N Seismicity characterized by explosions and rock avalanches.
22 Aug 2019 0704 800 m W Seismicity characterized by explosions and rock avalanches.
31 Aug 2019 1847 800 m N Seismicity characterized by explosions and rock avalanches.
04 Sep 2019 0936 300 m S --
28 Sep 2019 -- 500-800 m WNW --
30 Sep 2019 1806 800 m N --
06-07 Oct 2019 -- 0.8-1.4 km S, N --
15 Oct 2019 0707 400 m S --
20 Oct 2019 0829 400 m W --
01-05 Nov 2019 -- 200-800 m E, N Plumes were white-and-gray.
20-21, 23-25 Nov 2019 -- 500-800 m Multiple Thermal anomaly on 21 Nov.
03 Dec 2019 -- 800 m NE Thermal anomaly.
26 Dec 2019 -- 800 m S Discrete ash puffs in satellite imagery.

Thermal anomalies were sometimes noted by PVMBG, and were also frequently obvious in infrared satellite imagery suggesting lava flows and multiple active vents, as seen on 22 November 2019 (figure 19). Thermal anomalies using MODIS satellite instruments processed by the MODVOLC algorithm were recorded 2-4 days every month from July to December 2019. In contrast, the MIROVA (Middle InfraRed Observation of Volcanic Activity) system detected numerous hotspots on most days (figure 20).

Figure (see Caption) Figure 19. Example of thermal activity in the Ibu crater on 22 November 2019, along with a plume drifting SE. One or more vents in the crater are producing small lava flows, an observation common throughout the reporting period. Sentinel-2 false color (urban) images (bands 12, 11, 4), courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 20. Thermal anomalies recorded at Ibu by the MIROVA system using MODIS infrared satellite data for the year 2019. Courtesy of MIROVA.

Geologic Background. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the W flank. A group of maars is located below the N and W flanks. Only a few eruptions have been recorded in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); 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/); 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/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Lateiki (Tonga) — February 2020 Citation iconCite this Report

Lateiki

Tonga

19.18°S, 174.87°W; summit elev. 43 m

All times are local (unless otherwise noted)


Eruption 13-22 October 2019 creates new island, which disappears by mid-January 2020

Lateiki (Metis Shoal) is one of several submarine and island volcanoes on the W side of the Tonga trench in the South Pacific. It has produced ephemeral islands multiple times since the first confirmed activity in the mid-19th century. Two eruptions, in 1967 and 1979, produced islands that survived for a few months before eroding beneath the surface. An eruption in 1995 produced a larger island that persisted, possibly until a new eruption in mid-October 2019 destroyed it and built a new short-lived island. Information was provided by the Ministry of Lands, Survey and Natural Resources of the Government of the Kingdom of Tonga, and from satellite information and news sources.

Review of eruptions during 1967-1995. The first reported 20th century eruption at this location was observed by sailors beginning on 12 December 1967 (CSLP 02-67); incandescent ejecta rose several hundred meters into the air and "steam and smoke" rose at least 1,000 m from the ocean surface. The eruption created a small island that was reported to be a few tens of meters high, and a few thousand meters in length and width. Eruptive activity appeared to end in early January 1968, and the island quickly eroded beneath the surface by the end of February (figure 6). When observed in April 1968 the island was gone, with only plumes of yellowish water in the area of the former island.

Figure (see Caption) Figure 6. Waves break over Lateiki on 19 February 1968, more than a month after the end of a submarine eruption that began in December 1967 and produced a short-lived island. Photo by Charles Lundquist, 1968 (Smithsonian Astrophysical Observatory).

A large steam plume and ejecta were observed on 19 June 1979, along with a "growing area of tephra" around the site with a diameter of 16 km by the end of June (SEAN 04:06). Geologists visited the site in mid-July and at that time the island was about 300 m long, 120 m wide, and 15 m high, composed of tephra ranging in size from ash to large bombs (SEAN 04:07); ash emissions were still occurring from the E side of the island. It was determined that the new island was located about 1 km E of the 1967-68 island. By early October 1979 the island had nearly disappeared beneath the ocean surface.

A new eruption was first observed on 6 June 1995. A new island appeared above the waves as a growing lava dome on 12 June (BGVN 20:06). Numerous ash plumes rose hundreds of meters and dissipated downwind. By late June an elliptical dome, about 300 x 250 m in size and 50 m high, had stopped growing. The new island it formed was composed of hardened lava and not the tuff cones of earlier islands (figure 7) according to visitors to the island; pumice was not observed. An overflight of the area in December 2006 showed that an island was still present (figure 8), possibly from the June 1995 eruption. Sentinel-2 satellite imagery confirming the presence of Lateiki Island and discolored water was clearly recorded multiple times between 2015 and 2019. This suggests that the island created in 1995 could have lasted for more than 20 years (figure 9).

Figure (see Caption) Figure 7. An aerial view during the 1995 eruption of Lateiki forming a lava dome. Courtesy of the Government of the Kingdom of Tonga.
Figure (see Caption) Figure 8. Lateiki Island as seen on 7 December 2006; possibly part of the island that formed in 1995. Courtesy of the Government of the Kingdom of Tonga and the Royal New Zealand Air Force.
Figure (see Caption) Figure 9. Sentinel-2 satellite imagery confirmed the existence of an island present from 2015 through 2019 with little changes to its shape. This suggests that the island created in 1995 could have lasted for more than 20 years. Courtesy of Sentinel Hub Playground.

New eruption in October 2019. The Kingdom of Tonga reported a new eruption at Lateiki on 13 October 2019, first noted by a ship at 0800 on 14 October. NASA satellite imagery confirmed the eruption taking place that day (figure 10). The following morning a pilot from Real Tonga Airlines photographed the steam plume and reported a plume height of 4.6-5.2 km altitude (figure 11). The Wellington VAAC issued an aviation advisory report noting the pilot's observation of steam, but no ash plume was visible in satellite imagery. They issued a second report on 22 October of a similar steam plume reported by a pilot at 3.7 km altitude. The MODVOLC thermal alert system recorded three thermal alerts from Lateiki, one each on 18, 20, and 22 October 2019.

Figure (see Caption) Figure 10. NASA's Worldview Aqua/MODIS satellite imagery taken on 14 October 2019 over the Ha'apai and Vava'u region of Tonga showing the new eruption at Lateiki. Neiafu, Vava'u, is at the top right and Tofua and Kao islands are at the bottom left. The inset shows a closeup of Late Island at the top right and a white steam plume rising from Lateiki. Courtesy of the Government of the Kingdom of Tonga and NASA Worldview.
Figure (see Caption) Figure 11. Real Tonga Airline's Captain Samuela Folaumoetu'I photographed a large steam plume rising from Lateiki on the morning of 15 October 2019. Courtesy of the Government of the Kingdom of Tonga.

The first satellite image of the eruption on 15 October 2019 showed activity over a large area, much bigger than the preexisting island that was visible on 10 October (figure 12). Although the eruption produced a steam plume that drifted several tens of kilometers SW and strong incandescent activity, no ash plume was visible, similar to reports of dense steam with little ash during the 1968 and 1979 eruptions (figure 13). Strong incandescence and a dense steam plume were still present on 20 October (figure 14).

Figure (see Caption) Figure 12. The first satellite image of the eruption of Lateiki on 15 October 2019 showed activity over a large area, much bigger than the preexisting island that was visible on 10 October (inset). The two images are the same scale; the island was about 100 m in diameter before the eruption. Image uses Natural Color Rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 13. The steam plume from Lateiki on 15 October 2019 drifted more than 20 km SE from the volcano. A strong thermal anomaly from incandescent activity was present in the atmospheric penetration rendering (bands 12, 11, 8a) closeup of the same image (inset). Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 14. A dense plume of steam drifted NW from Lateiki on 20 October 2019, and a strong thermal signal (inset) indicated ongoing explosive activity. Courtesy of Annamaria Luongo and Sentinel Hub Playground.

A clear satellite image on 30 October 2019 revealed an island estimated to be about 100 m wide and 400 m long, according to geologist Taaniela Kula of the Tonga Geological Service of the Ministry of Lands, Survey and Natural Resources as reported by a local news source (Matangitonga). There was no obvious fumarolic steam activity from the surface, but a plume of greenish brown seawater swirled away from the island towards the NE (figure 15). In a comparison of the location of the old Lateiki island with the new one in satellite images, it was clear that the new island was located as far as 250 m to the NW (figure 16) on 30 October. Over the course of the next few weeks, the island's size decreased significantly; by 19 November, it was perhaps one-quarter the size it had been at the end of October. Lateiki Island continued to diminish during December 2019 and January 2020, and by mid-month only traces of discolored sea water were visible beneath the waves over the eruption site (figure 17).

Figure (see Caption) Figure 15. The new Lateiki Island was clearly visible on 30 October 2019 (top left), as was greenish-blue discoloration in the surrounding waters. It was estimated to be about 100 m wide and 400 m long that day. Its size decreased significantly over subsequent weeks; ten days later (top right) it was about half the size and two weeks later, on 14 November 2019 (bottom left), it was about one-third its original size. By 19 November (bottom right) only a fraction of the island remained. Greenish discolored water continued to be visible around the volcano. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 16. The location of the new Lateiki Island (Metis Shoal), shown here on 30 October 2019 in red, was a few hundred meters to the NW of the old position recorded on 5 September 2019 (in white). Courtesy of Annamaria Luongo and Sentinel Hub Playground.
Figure (see Caption) Figure 17. Lateiki Island disappeared beneath the waves in early January 2020, though plumes of discolored water continued to be observed later in the month. Courtesy of Sentinel Hub Playground.

Geologic Background. Lateiki, previously known as Metis Shoal, is a submarine volcano midway between the islands of Kao and Late that has produced a series of ephemeral islands since the first confirmed activity in the mid-19th century. An island, perhaps not in eruption, was reported in 1781 and subsequently eroded away. During periods of inactivity following 20th-century eruptions, waves have been observed to break on rocky reefs or sandy banks with depths of 10 m or less. Dacitic tuff cones formed during the first 20th-century eruptions in 1967 and 1979 were soon eroded beneath the ocean surface. An eruption in 1995 produced an island with a diameter of 280 m and a height of 43 m following growth of a lava dome above the surface.

Information Contacts: Government of the Kingdom of Tonga, PO Box 5, Nuku'alofa, Tonga (URL: http://www.gov.to/ ); Royal New Zealand Air Force (URL: http://www.airforce.mil.nz/); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Annamaria Luongo, Brussels, Belgium (Twitter: @annamaria_84, URL: https://twitter.com/annamaria_84 ); Taaniela Kula, Tonga Geological Service, Ministry of Lands, Survey and Natural Resources; Matangi Tonga Online (URL: https://matangitonga.to/2019/11/06/eruption-lateiki).


Aira (Japan) — January 2020 Citation iconCite this Report

Aira

Japan

31.593°N, 130.657°E; summit elev. 1117 m

All times are local (unless otherwise noted)


Ongoing explosions with ejecta and ash plumes, along with summit incandescence, during July-December 2019

Sakurajima is a highly active stratovolcano situated in the Aira caldera in southern Kyushu, Japan. Common volcanism for this recent eruptive episode since March 2017 includes frequent explosions, ash plumes, and scattered ejecta. Much of this activity has been focused in the Minamidake crater since 1955; the Showa crater on the E flank has had intermittent activity since 2006. This report updates activity during July through December 2019 with the primary source information from monthly reports by the Japan Meteorological Agency (JMA) and various satellite data.

During July to December 2019, explosive eruptions and ash plumes were reported multiple times per week by JMA. November was the most active, with 137 eruptive events, seven of which were explosive while August was the least active with no eruptive events recorded (table 22). Ash plumes rose between 800 m to 5.5 km above the crater rim during this reporting period. Large blocks of incandescent ejecta traveled as far as 1.7 km from the Minamidake crater during explosions in September through December. The Kagoshima Regional Meteorological Observatory (11 km WSW) reported monthly amounts of ashfall during each month, with a high of 143 g/m2 during October. Occasionally at night throughout this reporting period, crater incandescence was observed with a highly sensitive surveillance camera. All explosive activity originated from the Minamidake crater; the adjacent Showa crater produced mild thermal anomalies and gas-and-steam plumes.

Table 22. Monthly summary of eruptive events recorded at Sakurajima's Minamidake crater in the Aira caldera, July through December 2019. The number of events that were explosive in nature are in parentheses. No events were recorded at the Showa crater during this time. Ashfall is measured at the Kagoshima Local Meteorological Observatory (KLMO), 10 km W of Showa crater. Data courtesy of JMA (July to December 2019 monthly reports).

Month Ash emissions (explosive) Max plume height above crater Max ejecta distance from crater Total amount of ashfall (g/m2)
Jul 2019 9 (5) 3.8 km 1.1 km --
Aug 2019 -- 800 m -- 2
Sep 2019 32 (11) 3.4 km 1.7 km 115
Oct 2019 62 (41) 3.0 km 1.7 km 143
Nov 2019 137 (77) 5.5 km 1.7 km 69
Dec 2019 71 (49) 3.3 km 1.7 km 54

An explosion that occurred at 1044 on 4 July 2019 produced an ash plume that rose up to 3.2 km above the Minamidake crater rim and ejected material 1.1 km from the vent. Field surveys conducted on 17 and 23 July measured SO2 emissions that were 1,200-1,800 tons/day. Additional explosions between 19-22 July generated smaller plumes that rose to 1.5 km above the crater and ejected material 1.1 km away. On 28 July explosions at 1725 and 1754 produced ash plumes 3.5-3.8 km above the crater rim, which resulted in ashfall in areas N and E of Sakurajima (figure 86), including Kirishima City (20 km NE), Kagoshima Prefecture (30 km SE), Yusui Town (40 km N), and parts of the Kumamoto Prefecture (140 km NE).

Figure (see Caption) Figure 86. Photo of the Sakurajima explosion at 1725 on 28 July 2019 resulting in an ash plume rising 3.8 km above the crater (left). An on-site field survey on 29 July observed ashfall on roads and vegetation on the N side of the island (right). Photo by Moto Higashi-gun (left), courtesy of JMA (July 2019 report).

The month of August 2019 showed the least activity and consisted of mainly small eruptive events occurring up to 800 m above the crater; summit incandescence was observed with a highly sensitive surveillance camera. SO2 emissions were measured on 8 and 13 August with 1,000-2,000 tons/day, which was slightly greater than the previous month. An extensometer at the Arimura Observation Tunnel and an inclinometer at the Amida River recorded slight inflation on 29 August, but continuous GNSS (Global Navigation Satellite System) observations showed no significant changes.

In September 2019 there were 32 eruptive events recorded, of which 11 were explosions, more than the previous two months. Seismicity also increased during this month. An extensometer and inclinometer recorded inflation at the Minamidake crater on 9 September, which stopped after the eruptive events. On 16 September, an eruption at 0746 produced an ash plume that rose 2.8 km above the crater rim and drifted SW; a series of eruptive events followed from 0830-1110 (figure 87). Explosions on 18 and 20 September produced ash plumes that rose 3.4 km above the crater rim and ejecting material as far as 1.7 km from the summit crater on the 18th and 700 m on the 20th. Field surveys measured an increased amount of SO2 emissions ranging from 1,100 to 2,300 tons/day during September.

Figure (see Caption) Figure 87. Webcam image of an ash plume rising 2.8 km from the Minamidake crater at Sakurajima on 16 September 2019. Courtesy of Weathernews Inc.

Seismicity, SO2 emissions, and the number of eruptions continued to increase in October 2019, 41 of which were explosive. Field surveys conducted on 1, 11, and 15 October reported that SO2 emissions were 2,000-2,800 tons/day. An explosion at 0050 on 12 October produced an ash plume that traveled 1.7 km from the Minamidake crater. Explosions between 16 and 19 October produced an ash plume that rose up to 3 km above the crater rim (figure 88). The Japan Maritime Self-Defense Force 1st Air group observed gas-and-steam plumes rising from both the Minamidake and Showa craters on 25 October. The inflation reported from 16 September began to slow in late October.

Figure (see Caption) Figure 88. Photos taken from the E side of Sakurajima showing gas-and-steam emissions with some amount of ash rising from the volcano on 16 October 2019 after an explosion around 1200 that day (top). At night, summit incandescence is observed (bottom). Courtesy of Bradley Pitcher, Vanderbilt University.

November 2019 was the most active month during this reporting period with increased seismicity, SO2 emissions, and 137 eruptive events, 77 of which were explosive. GNSS observations indicated that inflation began to slow during this month. On 8 November, an explosion at 1724 produced an ash plume up to a maximum of 5.5 km above the crater rim and drifted E. This explosion ejected large blocks as far as 500-800 m away from the crater (figure 89). The last time plumes rose above 5 km from the vents occurred on 26 July 2016 at the Showa crater and on 7 October 2000 at the Minamidake crater. Field surveys on 8, 21, and 29 November measured increased SO2 emissions ranging from 2,600 to 3,600 tons/day. Eruptions between 13-19 November produced ash plumes that rose up to 3.6 km above the crater and ejected large blocks up 1.7 km away. An onsite survey on 29 November used infrared thermal imaging equipment to observe incandescence and geothermal areas near the Showa crater and the SE flank of Minamidake (figure 90).

Figure (see Caption) Figure 89. Photos of an ash plume rising 5.5 km above Sakurajima on 8 November 2019 and drifting E. Photo by Moto Higashi-gun (top left), courtesy of JMA (November 2019 report) and the Geoscientific Network of Chile.
Figure (see Caption) Figure 90. Webcam image of nighttime incandescence and gas-and-steam emissions with some amount of ash at Sakurajima on 29 November 2019. Courtesy of JMA (November 2019 report).

Volcanism, which included seismicity, SO2 emissions, and eruptive events, decreased during December 2019. Explosions during 4-10 December produced ash plumes that rose up to 2.6 km above the crater rim and ejected material up to 1.7 km away. Field surveys conducted on 6, 16, and 23 December measured SO2 emissions around 1,000-3,000 tons/day. On 24 December, an explosion produced an ash plume that rose to 3.3 km above the crater rim, this high for this month.

Sentinel-2 natural color satellite imagery showed dense ash plumes in late August 2019, early November, and through December (figure 91). These plumes drifted in different directions and rose to a maximum 5.5 km above the crater rim on 8 November.

Figure (see Caption) Figure 91. Natural color Sentinel-2 satellite images of Sakurajima within the Aira caldera from late August through December 2019 showed dense ash plumes rising from the Minamidake crater. Courtesy of Sentinel Hub Playground.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed intermittent thermal anomalies beginning in mid-August to early September 2019 after a nearly two-month hiatus (figure 92). Activity increased by early November and continued through December. Three Sentinel-2 thermal satellite images between late July and early October showed distinct thermal hotspots within the Minamidake crater, in addition to faint gas-and-steam emissions in July and September (figure 93).

Figure (see Caption) Figure 92. Thermal anomalies at Sakurajima during January-December 2019 as recorded by the MIROVA system (Log Radiative Power) started up in mid-August to early September after a two-month break and continued through December. Courtesy of MIROVA.
Figure (see Caption) Figure 93. Sentinel-2 thermal satellite images showing small thermal anomalies and gas-and-steam emissions (left and middle) at Sakurajima within the Minamidake crater between late July and early October 2019. All images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

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: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Weathernews Inc. (Twitter: @wni_jp, https://twitter.com/wni_jp, URL: https://weathernews.jp/s/topics/201608/210085/, photo posted at https://twitter.com/wni_jp/status/1173382407216652289); Bradley Pitcher, Vanderbilt University, Nashville. TN, USA (URL: https://bradpitcher.weebly.com/, Twitter: @TieDyeSciGuy, photo posted at https://twitter.com/TieDyeSciGuy/status/1185191225101471744); Geoscientific Network of Chile (Twitter: @RedGeoChile, https://twitter.com/RedGeoChile, Facebook: https://www.facebook.com/RedGeoChile/, photo posted at https://twitter.com/RedGeoChile/status/1192921768186515456).


Suwanosejima (Japan) — January 2020 Citation iconCite this Report

Suwanosejima

Japan

29.638°N, 129.714°E; summit elev. 796 m

All times are local (unless otherwise noted)


Explosions, ash emissions, and summit incandescence in July-December 2019

Suwanosejima, located south of Japan in the northern Ryukyu Islands, is an active andesitic stratovolcano that has had continuous activity since October 2004, typically producing ash plumes and Strombolian explosions. Much of this activity is focused within the Otake crater. This report updates information during July through December 2019 using monthly reports from the Japan Meteorological Agency (JMA), the Tokyo Volcanic Ash Advisory Center (VAAC), and various satellite data.

White gas-and-steam plumes rose from Suwanosejima on 26 July 2019, 30-31 August, 1-6, 10, and 20-27 September, reaching a maximum altitude of 2.4 km on 10 September, according to Tokyo VAAC advisories. Intermittent gray-white plumes were observed rising from the summit during October through December (figure 40).

Figure (see Caption) Figure 40. Surveillance camera images of white gas-and-steam emissions rising from Suwanosejima on 10 December 2019 (left) and up to 1.8 km above the crater rim on 28 December (right). At night, summit incandescence was also observed on 10 December. Courtesy of JMA.

An explosion that occurred at 2331 on 1 August 2019 ejected material 400 m from the crater while other eruptions on 3-6 and 26 August produced ash plumes that rose up to a maximum altitude of 2.1 km and drifted generally NW according to the Tokyo VAAC report. JMA reported eruptions and summit incandescence in September accompanied by white gas-and-steam plumes, but no explosions were noted. Eruptions on 19 and 29 October produced ash plumes that rose 300 and 800 m above the crater rim, resulting in ashfall in Toshima (4 km SW), according to the Toshima Village Office, Suwanosejima Branch Office. Another eruption on 30 October produced a similar gray-white plume rising 800 m above the crater rim but did not result in ashfall. Similar activity continued in November with eruptions on 5-7 and 13-15 November producing grayish-white plumes rising 900 m and 1.5 km above the crater rim and frequent crater incandescence. Ashfall was reported in Toshima Village on 19 and 20 November; the 20 November eruption ejected material 200 m from the Otake crater.

Field surveys on 14 and 18 December using an infrared thermal imaging system to the E of Suwanose Island showed hotspots around the Otake crater, on the N slope of the crater, and on the upper part of the E coastline. GNSS (Global Navigation Satellite Systems) observations on 15 and 17 December showed a slight change in the baseline length. After 2122 on 25-26 and 31 December, 23 eruptions, nine of which were explosive were reported, producing gray-white plumes that rose 800-1,800 m above the crater rim and ejected material up to 600 m from the Otake crater. JMA reported volcanic tremors occurred intermittently throughout this reporting period.

Incandescence at the summit crater was occasionally visible at night during July through December 2019, as recorded by webcam images and reported by JMA (figure 41). MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed weak thermal anomalies that occurred dominantly in November with little to no activity recorded between July and October (figure 42). Two Sentinel-2 thermal satellite images in early November and late December showed thermal hotspots within the summit crater (figure 43).

Figure (see Caption) Figure 41. Surveillance camera image of summit incandescence at Suwanosejima on 31 October 2019. Courtesy of JMA.
Figure (see Caption) Figure 42. Weak thermal anomalies at Suwanosejima during January-December 2019 as recorded by the MIROVA system (Log Radiative Power) dominantly occurred in mid-March, late May to mid-June, and November, with two hotspots detected in late September and late December. Courtesy of MIROVA.
Figure (see Caption) Figure 43. Sentinel-2 thermal satellite images showing small thermal anomalies (bright yellow-orange) within the Otake crater at Suwanosejima on 8 November 2019 (left) and faintly on 23 December 2019 behind clouds (right). Both images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.

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: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Barren Island (India) — February 2020 Citation iconCite this Report

Barren Island

India

12.278°N, 93.858°E; summit elev. 354 m

All times are local (unless otherwise noted)


Thermal anomalies and small ash plumes during February-April 2019 and September 2019-January 2020

Barren Island is a remote stratovolcano located east of India in the Andaman Islands. Its most recent eruptive episode began in September 2018 and has included lava flows, explosions, ash plumes, and lava fountaining (BGVN 44:02). This report updates information from February 2019 through January 2020 using various satellite data as a primary source of information.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed intermittent thermal anomalies within 5 km of the summit from mid-February 2019 through January 2020 (figure 41). There was a period of relatively low to no discernible activity between May to September 2019. The MODVOLC algorithm for MODIS thermal anomalies in comparison with Sentinel-2 thermal satellite imagery and Suomi NPP/VIIRS sensor data, registered elevated temperatures during late February 2019, early March, sparsely in April, late October, sparsely in November, early December, and intermittently in January 2020 (figure 42). Sentinel-2 thermal satellite imagery shows these thermal hotspots differing in strength from late February to late January 2020 (figure 43). The thermal anomalies in these satellite images are occasionally accompanied by ash plumes (25 February 2019, 23 October 2019, and 21 January 2020) and gas-and-steam emissions (26 April 2019).

Figure (see Caption) Figure 41. Intermittent thermal anomalies at Barren Island for 20 February 2019 through January 2020 occurred dominantly between late March to late April 2019 and late September 2019 through January 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 42. Timeline summary of observed activity at Barren Island from February 2019 through January 2020. For Sentinel-2, MODVOLC, and VIIRS data, the dates indicated are when thermal anomalies were detected. White areas indicated no activity was observed, which may also be due to meteoric clouds. Data courtesy of Darwin VAAC, Sentinel Hub Playground, HIGP, and NASA Worldview using the "Fire and Thermal Anomalies" layer.
Figure (see Caption) Figure 43. Sentinel-2 thermal images show ash plumes, gas-and-steam emissions, and thermal anomalies (bright yellow-orange) at Barren Island during February 2019-January 2020. The strongest thermal signature was observed on 23 October while the weakest one is observed on 26 January. Sentinel-2 False color (bands 12, 11, 4) images courtesy of Sentinel Hub Playground.

The Darwin Volcanic Ash Advisory Center (VAAC) reported ash plumes rising from the summit on 7, 14, and 16 March 2019. The maximum altitude of the ash plume occurred on 7 March, rising 1.8 km altitude, drifting W and NW and 1.2 km altitude, drifting E and ESE, based on observations from Himawari-8. The VAAC reports for 14 and 16 March reported the ash plumes rising 0.9 km and 1.2 km altitude, respectively drifting W and W.

Geologic Background. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S volcanic arc extending between Sumatra and Burma (Myanmar). It is the emergent summit of a volcano that rises from a depth of about 2250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the west, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. Historical eruptions have changed the morphology of the pyroclastic cone in the center of the caldera, and lava flows that fill much of the caldera floor have reached the sea along the western coast.

Information Contacts: MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Worldview (URL: https://worldview.earthdata.nasa.gov/).


Whakaari/White Island (New Zealand) — February 2020 Citation iconCite this Report

Whakaari/White Island

New Zealand

37.52°S, 177.18°E; summit elev. 294 m

All times are local (unless otherwise noted)


Explosion producing an ash plume and pyroclastic surge resulted in fatalities and injuries on 9 December 2019

Whakaari/White Island has been New Zealand's most active volcano since 1976. Located 48 km offshore, the volcano is a popular tourism destination with tours leaving the town of Whakatane with approximately 17,500 people visiting the island in 2018. Ten lives were lost in 1914 when part of the crater wall collapsed, impacting sulfur miners. More recently, a brief explosion at 1411 on 9 December 2019 produced an ash plume and pyroclastic surge that impacted the entire crater area. With 47 people on the island at the time, the death toll stood at 21 on 3 February 2019. At that time more patients were still in hospitals within New Zealand or their home countries.

The island is the summit of a large underwater volcano, with around 70% of the edifice below the ocean and rising around 900 m above sea level (figure 70). A broad crater opens to the ocean to the SE, with steep crater walls and an active Main Crater area to the NW rear of the crater floor (figure 71). Although the island is privately owned, GeoNet continuously monitors activity both remotely and with visits to the volcano. This Bulletin covers activity from May 2017 through December 2019 and is based on reports by GeoNet, the New Zealand Civil Defence Bay of Plenty Emergency Management Group, satellite data, and footage taken by visitors to the island.

Figure (see Caption) Figure 70. The top of the Whakaari/White Island edifice forms the island in the Bay of Plenty area, New Zealand, while 70% of the volcano is below sea level. Courtesy of GeoNet.
Figure (see Caption) Figure 71. This photo from 2004 shows the Main Crater area of Whakaari/White Island with the vent area indicated. The crater is an amphitheater shape with the crater floor distance between the vent and the ocean entry being about 700 m. The sediment plume begins at the area where tour boats dock at the island. Photo by Karen Britten, graphic by Danielle Charlton at University of Auckland; courtesy of GeoNet (11 December 2019 report).

Nearly continuous activity occurred from December 1975 to September 2000, including the formation of collapse and explosion craters producing ash emissions and explosions that impacted all of the Main Crater area. More recently, it has been in a state of elevated unrest since 2011. Renewed activity commenced with an explosive eruption on 5 August 2012 that was followed by the extrusion of a lava dome and ongoing phreatic explosions and minor ash emissions through March 2013. An ash cone was seen on 4 March 2013, and over the next few months the crater lake reformed. Further significant explosions took place on 20 August and 4, 8, and 11 October 2013. A landslide occurred in November 2015 with material descending into the lake. More recent activity on 27 April 2016 produced a short-lived eruption that deposited material across the crater floor and walls. A short period of ash emission later that year, on 13 September 2016, originated from a vent on the recent lava dome. Explosive eruptions occur with little to no warning.

Since 19 September 2016 the Volcanic Alert Level (VAL) was set to 1 (minor volcanic unrest) (figure 72). During early 2017 background activity in the crater continued, including active fumaroles emitting volcanic gases and steam from the active geothermal system, boiling springs, volcanic tremor, and deformation. By April 2017 a new crater lake had begun to form, the first since the April 2016 explosion when the lake floor was excavated an additional 13 m. Before this, there were areas where water ponded in depressions within the Main Crater but no stable lake.

Figure (see Caption) Figure 72. The New Zealand Volcanic Alert Level system up to date in February 2020. Courtesy of GeoNet.

Activity from mid-2017 through 2018. In July-August 2017 GeoNet scientists carried out the first fieldwork at the crater area since late 2015 to sample the new crater lake and gas emissions. The crater lake was significantly cooler than the past lakes at 20°C, compared to 30-70°C that was typical previously. Chemical analysis of water samples collected in July showed the lowest concentrations of most "volcanic elements" in the lake for the past 10-15 years due to the reduced volcanic gases entering the lake. The acidity remained similar to that of battery acid. Gas emissions from the 2012 dome were 114°C, which were over 450°C in 2012 and 330°C in 2016. Fumarole 0 also had a reduced temperature of 152°C, reduced from over 190°C in late 2016 (figure 73). The observations and measurements indicated a decline in unrest. Further visits in December 2017 noted relatively low-level unrest including 149°C gas emissions from fumarole 0, a small crater lake, and loud gas vents nearby (figures 74 and 75). By 27 November the lake had risen to 10 m below overflow. Analysis of water samples led to an estimate of 75% of the lake water resulting from condensing steam vents below the lake and the rest from rainfall.

Figure (see Caption) Figure 73. A GeoNet scientists conducting field work near Fumarole 0, an accessible gas vent on Whakaari/White Island in August 2017. Courtesy of GeoNet (23 August 2017 report).
Figure (see Caption) Figure 74. GeoNet scientists sample gas emissions from vents on the 2012 Whakaari/White Island dome. The red circle in the left image indicates the location of the scientists. Courtesy of GeoNet (23 August 2017 report).
Figure (see Caption) Figure 75. Active fumaroles and vents in the Main Crater of Whakaari/White Island including Fumarole 0 (top left). The crater lake formed in mid-2017 and gas emissions rise from surrounding vents (right). Courtesy of GeoNet (22 December 2017 report).

Routine fieldwork by GeoNet monitoring teams in early March 2018 showed continued low-level unrest and no apparent changes after a recent nearby earthquake swarm. The most notable change was the increase in the crater lake size, likely a response from recent high rainfall (figure 76). The water remained a relatively cool 27°C. Temperatures continued to decline at the 2012 dome vent (128°C) and Fumarole 0 (138°C). Spring and stream flow had also declined. Deformation was observed towards the Active Crater of 2-5 mm per month and seismicity remained low. The increase in lake level drowned gas vents along the lake shore resulting in geyser-like activity (figure 77). GeoNet warned that a new eruption could occur at any time, often without any useful warning.

In mid-April 2018 visitors reported loud sounds from the crater area as a result of the rising lake level drowning vents on the 2012 dome (in the western side of the crater) and resulting in steam-driven activity. There was no notable change in volcanic activity. The sounds stopped by July 2018 as the geothermal system adjusted to the rising water, up to 17 m below overfill and filling at a rate of about 2,000 m3 per day, rising towards more active vents (figure 78). A gas monitoring flight taken on 12 September showed a steaming lake surrounded by active fumaroles along the crater wall (figure 79).

Figure (see Caption) Figure 76. The increase in the Whakaari/White Island crater lake size in early March 2018 with gas plumes rising from vents on the other side. Courtesy of GeoNet (19 March 2018 report).
Figure (see Caption) Figure 77. The increasing crater lake level at Whakaari/White Island produced geyser-like activity on the lake shore in March 2018. Courtesy of Brad Scott, GeoNet.
Figure (see Caption) Figure 78. Stills taken from a drone video of the Whakaari/White Island Main Crater lake and active vents producing gas emissions. Courtesy of GeoNet.
Figure (see Caption) Figure 79. Photos taken during a gas monitoring flight with GNS Science at Whakaari/White Island show gas and steam emissions, and a steaming crater lake on 12 September 2018. Note the people for scale on the lower-right crater rim in the bottom photograph. Copyright of Ben Clarke, University of Leicester, used with permission.

Activity during April to early December 2019. A GeoNet volcanic alert bulletin in April 2019 reported that steady low-level unrest continued. The level of the lake had been declining since late January and was back down to 13 m below overflow (figure 80). The water temperature had increased to over 60°C due to the fumarole activity below the lake. Fumarole 0 remained steady at around 120-130°C. During May-June a seismic swarm was reported offshore, unrelated to volcanic activity but increasing the risk of landslides within the crater due to the shallow locations.

Figure (see Caption) Figure 80. Planet Labs satellite images from March 2018 to April 2019 show fluctuations in the Whakaari/White Island crater lake level. Image copyright 2019 Planet Labs, Inc.

On 26 June the VAL was raised to level 2 (moderate to heightened volcanic unrest) due to increased SO2 flux rising to historically high levels. An overflight that day detected 1,886 tons/day, nearly three times the previous values of May 2019, the highest recorded value since 2013, and the second highest since measurements began in 2003. The VAL was subsequently lowered on 1 July due to a reduction in detected SO2 emissions of 880 tons/day on 28 June and 693 tons/day on 29 June.

GeoNet reported on 26 September that there was an increase in steam-driven activity within the active crater over the past three weeks. This included small geyser-like explosions of mud and steam with material reaching about 10 m above the lake. This was not attributed to an increase in volcanic activity, but to the crater lake level rising since early August.

On 30 October an increase in background activity was reported. An increasing trend in SO2 gas emissions and volcanic tremor had been ongoing for several months and had reached the highest levels since 2016. This indicated to GeoNet that Whakaari/White Island might be entering a period where eruptive activity was more likely. There were no significant changes in other monitoring parameters at this time and fumarole activity continued (figure 81).

Figure (see Caption) Figure 81. A webcam image taken at 1030 on 30 October 2019 from the crater rim shows the Whakaari/White Island crater lake to the right of the amphitheater-shaped crater and gas-and-steam plumes from active fumaroles. Courtesy of GeoNet.

On 18 November the VAL was raised to level 2 and the Aviation Colour Code was raised to Yellow due to further increase in SO2 emissions and volcanic tremor. Other monitoring parameters showed no significant changes. On 25 November GeoNet reported that moderate volcanic unrest continued but with no new changes. Gas emissions remained high and gas-driven ejecta regularly jetting material a few meters into the air above fumaroles in the crater lake (figure 82).

Figure (see Caption) Figure 82. A webcam image from the Whakaari/White Island crater rim shows gas-driven ejecta rising above a fumarole within the crater lake on 22 November 2019. Courtesy of GeoNet.

GeoNet reported on 3 December that moderate volcanic unrest continued, with increased but variable explosive gas and steam-driven jetting, with stronger events ejecting mud 20-30 m into the air and depositing mud around the vent area. Gas emissions and volcanic tremor remained elevated and occasional gas smells were reported on the North Island mainland depending on wind direction. The crater lake water level remained unchanged. Monitoring parameters were similar to those observed in 2011-2016 and remained within the expected range for moderate volcanic unrest.

Eruption on 9 December 2019. A short-lived eruption occurred at 1411 on 9 December 2019, generating a steam-and-ash plume to 3.6 km and covering the entire crater floor area with ash. Video taken by tourists on a nearby boat showed an eruption plume composed of a white steam-rich portion, and a black ash-rich ejecta (figure 83). A pyroclastic surge moved laterally across the crater floor and up the inner crater walls. Photos taken soon after the eruption showed sulfur-rich deposits across the crater floor and crater walls, and a helicopter that had been damaged and blown off the landing pad (figure 84). This activity caused the VAL to be raised to 4 (moderate volcanic eruption) and the Aviation Colour Code being raised to Orange.

Figure (see Caption) Figure 83. The beginning of the Whakaari/White Island 9 December 2019 eruption viewed from a boat that left the island about 20-30 minutes prior. Top: the steam-rich eruption plume rising above the volcano and a pyroclastic surge beginning to rise over the crater rim. Bottom: the expanded steam-and-ash plume of the pyroclastic surge that flowed over the crater floor to the ocean. Copyright of Michael Schade, used with permission.
Figure (see Caption) Figure 84. This photo of Whakaari/White Island taken after the 9 December 2019 eruption at around 1424 shows ash and sediment coating the crater floor and walls. The helicopter in this image was blown off the landing pad and damaged during the eruption. Copyright of Michael Schade, used with permission.

A steam plume was visible in a webcam image taken at 1430 from Whakatane, 21 minutes after the explosion (figure 85). Subsequent explosions occurred at 1630 and 1749. Search-and-Rescue teams reached the island after the eruption and noted a very strong sulfur smell that was experienced through respirators. They experienced severe stinging of any exposed skin that came in contact with the gas, and were left with sensitive skin and eyes, and sore throats. Later in the afternoon the gas-and-steam plume continued and a sediment plume was dispersing from the island (figure 86). The VAL was lowered to level 3 (minor volcanic eruption) at 1625 that day; the Aviation Colour Code remained at Orange.

Figure (see Caption) Figure 85. A view of Whakaari/White Island from Whakatane in the North Island of New Zealand. Left: there is no plume visible at 1410 on 9 December 2019, one minute before the eruption. Right: A gas-and-steam plume is visible 21 minutes after the eruption. Courtesy of GeoNet.
Figure (see Caption) Figure 86. A gas-and-steam plume rises from Whakaari/White Island on the afternoon of 9 December 2019 as rescue teams visit the island. A sediment plume in the ocean is dispersing from the island. Courtesy of Auckland Rescue Helicopter Trust.

During or immediately after the eruption an unstable portion of the SW inner crater wall, composed of 1914 landslide material, collapsed and was identified in satellite radar imagery acquired after the eruption. The material slid into the crater lake area and left a 12-m-high scarp. Movement in this area continued into early January.

Activity from late 2019 into early 2020. A significant increase in volcanic tremor began at around 0400 on 11 December (figure 87). The increase was accompanied by vigorous steaming and ejections of mud in several of the new vents. By the afternoon the tremor was at the highest level seen since the 2016 eruption, and monitoring data indicated that shallow magma was driving the increased unrest.

Figure (see Caption) Figure 87. This RSAM (Real-Time Seismic Amplitude) time series plot represents the energy produced at Whakaari/White Island from 11 November to 11 December 2019 with the Volcanic Activity Levels and the 9 December eruption indicated. The plot shows the sharp increase in seismic energy during 11 December. Courtesy of GeoNet (11 December 2019 report).

The VAL was lowered to 2 on the morning of 12 December to reflect moderate to heightened unrest as no further explosive activity had occurred since the event on the 9th. Volcanic tremor was occurring at very high levels by the time a bulletin was released at 1025 that day. Gas emissions increased since 10 January, steam and mud jetting continued, and the situation was interpreted to be highly volatile. The Aviation Colour Code remained at Orange. Risk assessment maps released that day show the high-risk areas as monitoring parameters continued to show an increased likelihood of another eruption (figure 88).

Figure (see Caption) Figure 88. Risk assessment maps of Whakaari/White Island show the increase in high-risk areas from 2 December to 12 December 2019. Courtesy of GeoNet (12 December 2019 report).

The volcanic activity bulletin for 13 December reported that volcanic tremor remained high, but had declined overnight. Vigorous steam and mud jetting continuing at the vent area. Brief ash emission was observed in the evening with ashfall restricted to the vent area. The 14 January bulletin reported that volcanic tremor had declined significantly over night, and nighttime webcam images showed a glow in the vent area due to high heat flow.

Aerial observations on 14 and 15 December revealed steam and gas emissions continuing from at least three open vents within a 100 m2 area (figure 89). One vent near the back of the crater area was emitting transparent, high-temperature gas that indicated that magma was near the surface, and produced a glow registered by low-light cameras (figure 90). The gas emissions had a blue tinge that indicated high SO2 content. The area that once contained the crater lake, 16 m below overflow before the eruption, was filled with debris and small isolated ponds mostly from rainfall, with different colors due to the water reacting with the eruption deposits. The gas-and-steam plume was white near the volcano but changed to a gray-brown color as it cooled and moved downwind due to the gas content (figure 91). On 15 December the tremor remained at low levels (figure 92).

Figure (see Caption) Figure 89. The Main Crater area of Whakaari/White Island showing the active vent area and gas-and-steam emissions on 15 December 2019. Gas emissions were high within the circled area. Before the eruption a few days earlier this area was partially filled by the crater lake. Courtesy of GeoNet (15 December 2019 report).
Figure (see Caption) Figure 90. A low-light nighttime camera at Whakaari/White Island imaged "a glow" at a vent within the active crater area on 13 December 2019. This glow is due to high-temperature gas emissions and light from external sources like the moon. Courtesy of GeoNet (15 December 2019 report).
Figure (see Caption) Figure 91. A gas-and-steam plume at Whakaari/White Island on 15 December 2019 is white near the crater and changes to a grey-brown color downwind due to the gas content. Courtesy of GeoNet (15 December 2019 report).
Figure (see Caption) Figure 92. The Whakaari/White Island seismic drum plot showing the difference in activity from 12 December (top) to 15 December (bottom). Courtesy of GeoNet (15 December 2019 report).

On 19 December tremor remained low (figure 93) and gas and steam emission continued. Overflight observations confirmed open vents with one producing temperatures over 650°C (figure 94). SO2 emissions remained high at around 15 kg/s, slightly lower than the 20 kg/s detected on 12 December. Small amounts of ash were produced on 23 and 26 December due to material entering the vents during erosion.

Figure (see Caption) Figure 93. This RSAM (Real-Time Seismic Amplitude) time series plot represents the energy produced at Whakaari/White Island from 1 November to mid-December 2019. The Volcanic Alert Levels and the 9 December eruption are indicated. Courtesy of GeoNet.
Figure (see Caption) Figure 94. A photograph and thermal infrared image of the Whakaari/White Island crater area on 19 December 2019. The thermal imaging registered temperatures up to 650°C at a vent emitting steam and gas. Courtesy of GeoNet.

The Aviation Colour Code was reduced to Yellow on 6 January 2020 and the VAL remained at 2. Strong gas and steam emissions continued from the vent area through early January and the glow persisted in nighttime webcam images. Short-lived episodes of volcanic tremor were recorded between 8-10 January and were accompanied by minor explosions. A 15 January bulletin reported that the temperature at the vent area remained very hot, up to 440°C, and SO2 emissions were within normal post-eruption levels.

High temperatures were detected within the vent area in Sentinel-2 thermal data on 6 and 16 January (figure 95). Lava extrusion was confirmed within the 9 December vents on 20 January. Airborne SO2 measurements on that day recorded continued high levels and the vent temperature was over 400°C. Observations on 4 February showed that no new lava extrusion had occurred, and gas fluxes were lower than two weeks ago, but still elevated. The temperatures measured in the crater were 550-570°C and no further changes to the area were observed.

Figure (see Caption) Figure 95. Sentinel-2 thermal infrared satellite images show elevated temperatures in the 9 December 2019 vent area on Whakaari/White Island. False color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

Geologic Background. The uninhabited Whakaari/White Island 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 SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused 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. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Information Contacts: New Zealand GeoNet Project, a collaboration between the Earthquake Commission and GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.geonet.org.nz/); GNS Science, Wairakei Research Centre, Private Bag 2000, Taupo 3352, New Zealand (URL: http://www.gns.cri.nz/); Bay of Plenty Emergency Management Group Civil Defense, New Zealand (URL: http://www.bopcivildefence.govt.nz/); Auckland Rescue Helicopter Trust, Auckland, New Zealand (URL: https://www.rescuehelicopter.org.nz/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/); Ben Clarke, The University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom (URL: https://le.ac.uk/geology, Twitter: https://twitter.com/PyroclasticBen); Michael Schade, San Francisco, USA (URL: https://twitter.com/sch).


Kadovar (Papua New Guinea) — January 2020 Citation iconCite this Report

Kadovar

Papua New Guinea

3.608°S, 144.588°E; summit elev. 365 m

All times are local (unless otherwise noted)


Frequent gas and some ash emissions during May-December 2019 with some hot avalanches

Kadovar is an island volcano north of Papua New Guinea and northwest of Manam. The first confirmed historical activity began in January 2018 and resulted in the evacuation of residents from the island. Eruptive activity through 2018 changed the morphology of the SE side of the island and activity continued through 2019 (figure 36). This report summarizes activity from May through December 2019 and is based largely on various satellite data, tourist reports, and Darwin Volcanic Ash Advisory Center (VAAC) reports.

Figure (see Caption) Figure 36. The morphological changes to Kadovar from 2017 to June 2019. Top: the vegetated island has a horseshoe-shaped crater that opens towards the SE; the population of the island was around 600 people at this time. Middle: by May 2018 the eruption was well underway with an active summit crater and an active dome off the east flank. Much of the vegetation has been killed and ashfall covers a lot of the island. Bottom: the bay below the SE flank has filled in with volcanic debris. The E-flank coastal dome is no longer active, but activity continues at the summit. PlanetScope satellite images copyright Planet Labs 2019.

Since this eruptive episode began a large part of the island has been deforested and has undergone erosion (figure 37). Activity in early 2019 included regular gas and steam emissions, ash plumes, and thermal anomalies at the summit (BGVN 44:05). On 15 May an ash plume originated from two vents at the summit area and dispersed to the east. A MODVOLC thermal alert was also issued on this day, and again on 17 May. Elevated temperatures were detected in Sentinel-2 thermal satellite data on 20, 21, and 30 May (figure 38), with accompanying gas-and-steam plumes dispersing to the NNW and NW. On 30 May the area of elevated temperature extended to the SE shoreline, indicating an avalanche of hot material reaching the water.

Figure (see Caption) Figure 37. The southern flank of Kadovar seen here on 13 November 2019 had been deforested by eruptive activity and erosion had produced gullies down the flanks. Copyrighted photo by Chrissie Goldrick, used with permission.
Figure (see Caption) Figure 38. Sentinel-2 thermal satellite images show elevated temperatures at the summit area, and down to the coast in the top image. Gas-and-steam plumes are visible dispersing towards the NW. Sentinel-2 false color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel-Hub Playground.

Throughout June cloud-free Sentinel-2 thermal satellite images showed elevated temperatures at the summit area and extending down the upper SE flank (figure 38). Gas-and-steam plumes were persistent in every Sentinel-2 and NASA Suomi NPP / VIIRS (Visible Infrared Imaging Radiometer Suite) image. MODVOLC thermal alerts were issued on 4 and 9 June. Similar activity continued through July with gas-and-steam emissions visible in every cloud-free satellite image. Thermal anomalies appeared weaker in late-July but remained at the summit area. An ash plume was imaged on 17 July by Landsat 8 with a gas-and-ash plume dispersing to the west (figure 39). Thermal anomalies continued through August with a MODVOLC thermal alert issued on the 14th. Gas emissions also continued and a Volcano Observatory Notice for Aviation (VONA) was issued on the 19th reporting an ash plume to an altitude of 1.5 km and drifting NW.

Figure (see Caption) Figure 39. An ash plume rising above Kadovar and a gas plume dispersing to the NW on 17 July 2019. Truecolor pansharpened Landsat 8 satellite image courtesy of Sentinel Hub Playground.

An elongate area extending from the summit area to the E-flank coastal dome appears lighter in color in a 7 September Sentinel-2 natural color satellite image, and as a higher temperature area in the correlating thermal bands, indicating a hot avalanche deposit. These observations along with the previous avalanche, persistent elevated summit temperatures, and persistent gas and steam emissions from varying vent locations (figure 40) suggests that the summit dome has remained active through 2019.

Figure (see Caption) Figure 40. Sentinel-2 visible and thermal satellite images acquired on 7 September 2019 show fresh deposits down the east flank of Kadovar. They appear as a lighter colored area in visible, and show as a hot area (orange) in thermal data. Sentinel-2 natural color (bands 4, 3, 2) and false color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel-Hub Playground.

Thermal anomalies and emissions continued through to the end of 2019 (figure 41). A tour group witnessed an explosion producing an ash plume at around 1800 on 13 November (figure 42). While the ash plume erupted near-vertically above the island, a more diffuse gas plume rose from multiple vents on the summit dome and dispersed at a lower altitude.

Figure (see Caption) Figure 41. The summit area of Kadovar emitting gas-and-steam plumes in August, September, and November 2019. The plumes are persistent in satellite images throughout May through December and there is variation in the number and locations of the source vents. PlanetScope satellite images copyright Planet Labs 2019.
Figure (see Caption) Figure 42. An ash plume and a lower gas plume rise during an eruption of Kadovar on 13 November 2019. The summit lava dome is visibly degassing to produce the white gas plume. Copyrighted photos by Chrissie Goldrick, used with permission.

While gas plumes were visible throughout May-December 2019 (figure 43), SO2 plumes were difficult to detect in NASA SO2 images due to the activity of nearby Manam volcano. The MIROVA thermal detection system shows continued elevated temperatures through to early December, with an increase during May-June (figure 44). Sentinel-2 thermal images showed elevated temperatures through to the end of December but at a lower intensity than previous months.

Figure (see Caption) Figure 43. This photo of the southeast side Kadovar on 13 November 2019 shows a persistent low-level gas plume blowing towards the left and a more vigorous plume is visible near the crater. This is an example of the persistent plume visible in satellite imagery throughout July-December 2019. Copyrighted photo by Chrissie Goldrick, used with permission.
Figure (see Caption) Figure 44. The MIROVA plot of radiative power at Kadovar shows thermal anomalies throughout 2019 with some variations in frequency. Note that while the black lines indicate that the thermal anomalies are greater than 5 km from the vent, the designated summit location is inaccurate so these are actually a the summit crater and on the E flank. Courtesy of MIROVA.

Geologic Background. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. It is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. Prior to an eruption that began in 2018, a lava dome formed the high point of the andesitic volcano, filling an arcuate landslide scarp open to the south; submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. A period of heightened thermal phenomena took place in 1976. An eruption began in January 2018 that included lava effusion from vents at the summit and at the E coast.

Information Contacts: 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/); Planet Labs, Inc. (URL: https://www.planet.com/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); NASA Worldview (URL: https://worldview.earthdata.nasa.gov); Chrissie Goldrick, Australian Geographic, Level 7, 54 Park Street, Sydney, NSW 2000, Australia (URL: https://www.australiangeographic.com.au/).

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Scientific Event Alert Network Bulletin - Volume 06, Number 03 (March 1981)

Managing Editor: Lindsay McClelland

Acatenango (Guatemala)

No visible fumarolic activity; strong sulfur odor near sumit craters

Aira (Japan)

Explosions; two incandescent columns

Arenal (Costa Rica)

Lava extrusion continues; more chlorine in gases

Bagana (Papua New Guinea)

Lava extrusion continues; small nuées ardentes

Bam (Papua New Guinea)

Discolored water

Etna (Italy)

Large lava flows cause severe damage

Fournaise, Piton de la (France)

Lava from new vents

Fuego (Guatemala)

Gas emission; no significant changes in the summit area

Kadovar (Papua New Guinea)

Discolored water

Karkar (Papua New Guinea)

Fumarolic activity continues; possible minor deflation

Kavachi (Solomon Islands)

Submarine activity continues

Kirishimayama (Japan)

New fumaroles in residential area

Krafla (Iceland)

Inflation reaches level at which previous eruptions were triggered

Langila (Papua New Guinea)

Activity declines to vapor emission

Manam (Papua New Guinea)

Ash emission, seismicity, and inflation increase

Masaya (Nicaragua)

Gas emission continues unabated; pit crater enlarges

Momotombo (Nicaragua)

Small continuous plume

Negro, Cerro (Nicaragua)

Minor fumarolic activity

Pacaya (Guatemala)

Lava flows and Strombolian activity

Poas (Costa Rica)

Explosions; incandescence on dome

San Cristobal (Nicaragua)

Emissions of SO2 increase by an order of magnitude; high seismicity; incandescence

Santa Maria (Guatemala)

Explosive activity continues

Semeru (Indonesia)

Nuées ardentes and lava avalanches; one killed, 272 evacuated

Shikotsu (Japan)

Seismicity declines without expected eruption

St. Helens (United States)

Lava extrusion and small explosion follow deformation and seismicity

Telica (Nicaragua)

Holes in crater wall emit vapor plume; occasional minor ash eruptions

Whakaari/White Island (New Zealand)

Explosions and seismicity; tephra and tilt measured



Acatenango (Guatemala) — March 1981 Citation iconCite this Report

Acatenango

Guatemala

14.501°N, 90.876°W; summit elev. 3976 m

All times are local (unless otherwise noted)


No visible fumarolic activity; strong sulfur odor near sumit craters

Geologists visited the summit 16, 17, and 18 February. There was no visible fumarolic activity around the summit, or in the explosion craters from the volcano's last eruption in 1972. The geologists smelled a strong sulfur odor in the immediate vicinity of the summit craters.

Geologic Background. Acatenango, along with its twin volcano to the south, Volcán Fuego, overlooks the historic former capital city of Antigua, Guatemala. The two principal summits were constructed during three eruptive periods post-dating the roughly 85,000-year-old Los Chocoyos tephra from Atitlán caldera. An ancestral Acatenango volcano collapsed to the south sometime prior to 43,000 years ago, forming La Democracia debris-avalanche deposit, which covers a wide area of the Pacific coastal plain. Construction of Yepocapa, the northern summit of Acatenango, was completed about 20,000 years ago, after which growth of the southern and highest cone, Pico Central (also known as Pico Mayor), began. The first well-documented eruptions took place from 1924 to 1927, although earlier historical eruptions may have occurred. Francisco Vasquez, writing in 1690, noted that in 1661 a volcano that lay aside of Fuego "opened a smoking mouth and still gives off smoke from another three, but without noise."

Information Contacts: T. Bornhorst and C. Chesner, Michigan Tech. Univ.


Aira (Japan) — March 1981 Citation iconCite this Report

Aira

Japan

31.593°N, 130.657°E; summit elev. 1117 m

All times are local (unless otherwise noted)


Explosions; two incandescent columns

Eleven explosions occurred in March. The highest ash cloud grew to 2 km on the 18th. Two incandescent columns rose simultaneously from vents in the summit crater of Minami-dake on the 20th. No damage was reported.

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, Tokyo.


Arenal (Costa Rica) — March 1981 Citation iconCite this Report

Arenal

Costa Rica

10.463°N, 84.703°W; summit elev. 1670 m

All times are local (unless otherwise noted)


Lava extrusion continues; more chlorine in gases

Lava flow 34 continued to descend the W flank. By mid-March, the flow had divided into five lobes. Geologists noted an increase in the chlorine content of gas emitted from the summit area.

Geologic Background. Conical Volcán Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1670-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. Arenal lies along a volcanic chain that has migrated to the NW from the late-Pleistocene Los Perdidos lava domes through the Pleistocene-to-Holocene Chato volcano, which contains a 500-m-wide, lake-filled summit crater. The earliest known eruptions of Arenal took place about 7000 years ago, and it was active concurrently with Cerro Chato until the activity of Chato ended about 3500 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. An eruptive period that began with a major explosive eruption in 1968 ended in December 2010; continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows characterized the eruption from vents at the summit and on the upper western flank.

Information Contacts: J. Barquero H., Univ. Nacional, Heredia.


Bagana (Papua New Guinea) — March 1981 Citation iconCite this Report

Bagana

Papua New Guinea

6.137°S, 155.196°E; summit elev. 1855 m

All times are local (unless otherwise noted)


Lava extrusion continues; small nuées ardentes

"Moderate to strong emission of white vapour continued throughout March. An active lava flow descending the [established lava channel on] the N slope had reached 2/3 of the way down the mountain. Small nuée ardente-type avalanches caused by collapse of the flow front were observed during an aerial inspection on 9 January."

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: C. McKee, RVO.


Bam (Papua New Guinea) — March 1981 Citation iconCite this Report

Bam

Papua New Guinea

3.613°S, 144.818°E; summit elev. 685 m

All times are local (unless otherwise noted)


Discolored water

During aerial inspections 6 and 19 March, a 1-km-long zone of orange sea discoloration was noted at the S shore of Bam Island.

Geologic Background. The small 2.4 x 1.6 km island of Bam is the summit of a mostly submerged volcano that is one of the more active in Papua New Guinea. Bam is the SE-most of the Schouten Islands, and lies off the coast of New Guinea, about 40 km NNE of the mouth of the Sepik River. A steep-walled summit crater that is 300 m wide and 180 m deep is the source of recent eruptions, which have kept the upper half of the cone sparsely vegetated. A NE-trending landslide scarp extends across the upper part of the andesitic volcano from the SW coast, and a large submarine debris-avalanche deposits lies to the S and SW. The younger summit cone partially buries the eastern side of the collapse scarp. A recent lava platform on the N flank supports the small island's only villages. Historical eruptions, recorded since 1872, have been restricted to small-to-moderate explosive activity from the summit crater.

Information Contacts: Acting Senior Volcanologist, RVO.


Etna (Italy) — March 1981 Citation iconCite this Report

Etna

Italy

37.748°N, 14.999°E; summit elev. 3295 m

All times are local (unless otherwise noted)


Large lava flows cause severe damage

An eruption 17-23 March extruded lava from several fissures on the NNW flank. Initial estimates indicate that the main flow reached 7.5 km in length, lava flows covered an area of 6 km2, and 30-35 x 106 m3 of lava were extruded [but later calculations from topographic measurements by Murray (1982) yield 18 x 106 m³] at a rate of 58-70 m3/s. Damage was estimated at about $10 million. Of the 90 historic eruptions of Etna for which location data are available, only three (1614, 1764, and 1918) occurred on the NW or NNW flanks.

Etna began to erupt on 17 March after a 2-day swarm of about 500 earthquakes, including a M 4-5 event during the morning of 16 March. On 17 March at 1337 an eruption fissure opened at about 2,550 m [corrected from 2,250 m] above sea level on the NW flank, trending approximately NW-SE. Lava fountains rose 100-200 m from this fissure and lava flowed rapidly westward. In the next 4 hours, three more fissures opened, the first and third also trending NW, the second WNW. All showed strong lava fountaining and were the source of lava flows. As fissures formed at lower altitudes, those higher on the volcano ceased to be active.

At 1855 on 17 March, another fissure opened at 1800 m elevation on the NNW flank, trending NW at its upper end, but after a short distance changed direction to more directly downslope. A large lava flow that originated from this fissure traveled 5 km within 4 hours, cut a railroad and highway (at 730 m altitude) during the night, and crossed another railway line and road (at 680 m altitude) early on 18 March. The lava destroyed orchards and farm buildings, and passed very close to the village of Montelaguardia, forcing the evacuation of its 250 residents. The fissure propagated downslope to 1,300 m altitude at 1130 on 18 March. The lower section extruded a small lava flow that briefly threatened Randazzo (population 15,000) but did not force its evacuation. By 1630, the center of the main flow was more than 1 km wide and its front had reached 650 m altitude, 100 m from the bed of the Alcantara River.

At 2200, another fissure opened between 1,235 and 1,140 m altitude extruding flows that moved toward Randazzo. By this time, the system of eruptive fissures had a total length of about 7.5 km. The main flow reached the Alcantara River bed (600 m above sea level) on 19 March at 1100, while the flows extruded from the fissure between 1,235 and 1,140 m altitude continued to advance slowly. By noon on 20 March, this fissure was characterized by mild spatter ejection that continued to feed slow-moving lava flows. However, the main flow had nearly halted. Sporadic activity between 1235 and 1140 m continued 21-22 March, finally ending during the evening of the 23rd. The longest flow from this fissure stopped at 900 m elevation, 2 km from Randazzo. More than 25 small earthquakes were recorded on 23 March, centered around the eruption fissures.

Throughout the period of lava extrusion, more or less intense emission of sand-size tephra occurred from Bocca Nuova, enlarging it to the W. Strong winds caused flank ashfalls on 22 March [as the Northeast Crater briefly ejected juvenile cinders; Tanguy and Patané, 1984].

Further References. Murray, J.B., 1982, Les Déformations de l'Etna à la suite de l'eruption de Mars 1981: Bull. PIRPSEV, no. 57.

Sanderson, T.J.O., Berrino, G., Corrado, G., and Grimaldi, M., 1983, Ground deformation and gravity accompanying the March 1981 eruption of Mount Etna: JVGR v. 16, p. 299-316.

Guest, J.E., Kilburn, C.R.J., Pinkerton, H., and Duncan, J.M., 1987, The evolution of lava flow-fields: Observations of the 1981 and 1983 eruptions of Mt. Etna, Sicily: BV v. 49, p. 527-540.

Geologic Background. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur, sometimes simultaneously. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more summit craters. Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by Strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.

Information Contacts: R. Romano, IIV; UPI; AP.


Piton de la Fournaise (France) — March 1981 Citation iconCite this Report

Piton de la Fournaise

France

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

All times are local (unless otherwise noted)


Lava from new vents

The activity SW of the summit that began 26 February continued until 25-26 March. A new eruption on 1 April was preceded by a swarm of local earthquakes, starting at 1923. The seismographs at Réunion's volcano observatory registered 72 discrete events in the next few hours, before the onset of harmonic tremor and the start of an eruption at 2141. Observatory personnel reported that lava extruded from a vent in the north-central area of the caldera, 3 km ENE of the summit, flowed toward the N caldera wall, reaching it during the night. By the early afternoon of 2 April, the flow front was 1 km W of the coast highway [but see 6:4], but the lava's rate of advance had slowed considerably.

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: J. LeMouel and J-L. Cheminée, IPG, Paris.


Fuego (Guatemala) — March 1981 Citation iconCite this Report

Fuego

Guatemala

14.473°N, 90.88°W; summit elev. 3763 m

All times are local (unless otherwise noted)


Gas emission; no significant changes in the summit area

On 16, 17, and 18 February geologists visited the summits of Fuego and Acatenango Volcanoes. Comparisons of photographs of Fuego taken on this expedition to ones taken by W.I. Rose, Jr., in February 1980 showed no striking physical changes in the summit region. The main areas of gas emission, on the N and the SE sides of the main crater, were the same as in 1980. The SE area is a spatter vent from Fuego's last eruption in 1977-79. During the group's visit, gas was being emitted at a moderate, steady rate, as in early 1980. On 21 February, however, the group observed that there was a clear pulsation in the rate of emission, with a period of about 2 minutes. A light wind on the 21st allowed the gas plume to rise nearly vertically about 400 m above the crater. Around the crater rim there were only a few fumaroles in contrast to many in early 1980. New fumaroles had appeared around and atop an older irregular domal protrusion on the W flank of the summit.

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

Information Contacts: T. Bornhorst and C. Chesner, Michigan Tech. Univ.


Kadovar (Papua New Guinea) — March 1981 Citation iconCite this Report

Kadovar

Papua New Guinea

3.608°S, 144.588°E; summit elev. 365 m

All times are local (unless otherwise noted)


Discolored water

"An area of orange discolouration of the sea at the NE shore was observed during aerial inspections on 6 and 19 March. Previously (1976-77) sea discolouration was present at the S shore and was related to the development of a new thermal area on the S flank of the island. This thermal area was now observed to have been reduced in size by regrowth of vegetation."

Geologic Background. The 2-km-wide island of Kadovar is the emergent summit of a Bismarck Sea stratovolcano of Holocene age. It is part of the Schouten Islands, and lies off the coast of New Guinea, about 25 km N of the mouth of the Sepik River. Prior to an eruption that began in 2018, a lava dome formed the high point of the andesitic volcano, filling an arcuate landslide scarp open to the south; submarine debris-avalanche deposits occur in that direction. Thick lava flows with columnar jointing forms low cliffs along the coast. The youthful island lacks fringing or offshore reefs. A period of heightened thermal phenomena took place in 1976. An eruption began in January 2018 that included lava effusion from vents at the summit and at the E coast.

Information Contacts: Acting Senior Volcanologist, RVO.


Karkar (Papua New Guinea) — March 1981 Citation iconCite this Report

Karkar

Papua New Guinea

4.649°S, 145.964°E; summit elev. 1839 m

All times are local (unless otherwise noted)


Fumarolic activity continues; possible minor deflation

"Aerial and ground inspections were made 6-8 March and other aerial inspections were carried out on 19 and 26 March. Conditions in the caldera appeared similar to those during inspections in November and December 1980. Hydrothermal activity was continuing at the base of the 1979 crater and maximum measured temperatures were 97.5°C. The other main source was on the W part of Bagiai Cone. During the 26 March aerial inspection the volume of emission was reportedly greater than previously observed.

"Gravity measurements and levelling were carried out 6-8 March. The gravity measurements were consistent with previous sets in 1980, and might indicate summit deflation. Levelling up to the end of 1980 showed possible small deflationary trends of several µrad at the 3 mid- and upper-flank tilt arrays. However the changes were very small and similar in size to the limits of error in making the measurements."

Geologic Background. Karkar is a 19 x 25 km wide, forest-covered island that is truncated by two nested summit calderas. The 5.5-km-wide outer caldera was formed during one or more eruptions, the last of which occurred 9000 years ago. The eccentric 3.2-km-wide inner caldera was formed sometime between 1500 and 800 years ago. Parasitic cones are present on the N and S flanks of this basaltic-to-andesitic volcano; a linear array of small cones extends from the northern rim of the outer caldera nearly to the coast. Most historical eruptions, which date back to 1643, have originated from Bagiai cone, a pyroclastic cone constructed within the steep-walled, 300-m-deep inner caldera. The floor of the caldera is covered by young, mostly unvegetated andesitic lava flows.

Information Contacts: C. McKee, RVO.


Kavachi (Solomon Islands) — March 1981 Citation iconCite this Report

Kavachi

Solomon Islands

8.991°S, 157.979°E; summit elev. -20 m

All times are local (unless otherwise noted)


Submarine activity continues

Solair Captain Peter Cox overflew Kavachi on 9 January at 1540. At 30- to 60- minute intervals steam fountains rose to a height he estimated at 150 m. The sea was stained light brown for as much as 15-20 km from the volcano, but Cox saw no floating pumice.

Ministry of Natural Resources geologist A. Smith observed minor eruptive activity on 25 February. Submarine explosions apparently originating at 5-10 m depth transmitted shock waves to the surface. Some gas bubbles could be seen but no ejecta were evident. The prevailing wind drove seas to the NE, carrying an expanding plume of yellow-brown to yellow-green water visible on the surface for at least 2 km from the volcano.

Geologic Background. Named for a sea-god of the Gatokae and Vangunu peoples, Kavachi is one of the most active submarine volcanoes in the SW Pacific, located in the Solomon Islands south of Vangunu Island about 30 km N of the site of subduction of the Indo-Australian plate beneath the Pacific plate. Sometimes referred to as Rejo te Kvachi ("Kavachi's Oven"), this shallow submarine basaltic-to-andesitic volcano has produced ephemeral islands up to 1 km long many times since its first recorded eruption during 1939. Residents of the nearby islands of Vanguna and Nggatokae (Gatokae) reported "fire on the water" prior to 1939, a possible reference to earlier eruptions. The roughly conical edifice rises from water depths of 1.1-1.2 km on the north and greater depths to the SE. Frequent shallow submarine and occasional subaerial eruptions produce phreatomagmatic explosions that eject steam, ash, and incandescent bombs. On a number of occasions lava flows were observed on the ephemeral islands.

Information Contacts: D. Tuni, Ministry of Natural Resources, Honiara.


Kirishimayama (Japan) — March 1981 Citation iconCite this Report

Kirishimayama

Japan

31.934°N, 130.862°E; summit elev. 1700 m

All times are local (unless otherwise noted)


New fumaroles in residential area

Fumarolic activity had increased since November 1980 in the Iodani ("Sulfur Valley") area at the W base of the volcano. Personnel from Kagoshima and Tokyo Universities, Tokyo Industrial College, and the JMA observatory monitored the temperatures and the chemical composition of the vapor. The highest temperature measured was 98°C in March, the same as during the past 2 years. The gas content varied from 90% CO2-10% H2S to 70% CO2-30% H2S. New fumaroles appeared in a residential area. Because of the dense gas, civil police closed a parking area and part of a road.

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

Information Contacts: JMA.


Krafla (Iceland) — March 1981 Citation iconCite this Report

Krafla

Iceland

65.715°N, 16.728°W; summit elev. 800 m

All times are local (unless otherwise noted)


Inflation reaches level at which previous eruptions were triggered

"As of 2 April, land elevation over the Krafla magma reservoirs, as indicated by tiltmeters, was about the same as at the time of the eruption that began 30 January. Inflation continued and from past experience an eruption can be expected to take place in the near future, possibly within the next few weeks."

Geologic Background. The Krafla central volcano, located NE of Myvatn lake, is a topographically indistinct 10-km-wide caldera that is cut by a N-S-trending fissure system. Eruption of a rhyolitic welded tuff about 100,000 years ago was associated with formation of the caldera. Krafla has been the source of many rifting and eruptive events during the Holocene, including two in historical time, during 1724-29 and 1975-84. The prominent Hverfjall and Ludent tuff rings east of Myvatn were erupted along the 100-km-long fissure system, which extends as far as the north coast of Iceland. Iceland's renowned Myvatn lake formed during the eruption of the older Laxarhraun lava flow from the Ketildyngja shield volcano of the Fremrinamur volcanic system about 3800 years before present (BP); its present shape is constrained by the roughly 2000 years BP younger Laxarhraun lava flow from the Krafla volcanic system. The abundant pseudocraters that form a prominent part of the Myvatn landscape were created when the younger Laxarhraun lava flow entered the lake.

Information Contacts: K. Grönvold, NVI.


Langila (Papua New Guinea) — March 1981 Citation iconCite this Report

Langila

Papua New Guinea

5.525°S, 148.42°E; summit elev. 1330 m

All times are local (unless otherwise noted)


Activity declines to vapor emission

"The first 3 months of 1981 have shown a steady decline of eruptive activity. Occasional brown ash-laden emissions from Crater 2 were observed in January, but in February and March emissions from Crater 2 were white and apparently of declining volume. Crater 3 released blue and white vapours in January and February; in March only small volumes of white vapour were emitted. The last time glow was observed was on 21 January from Crater 2. Seismic activity from Langila was at a low level January-March. Small tremor-like signals continued to be recorded."

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: C. McKee, RVO.


Manam (Papua New Guinea) — March 1981 Citation iconCite this Report

Manam

Papua New Guinea

4.08°S, 145.037°E; summit elev. 1807 m

All times are local (unless otherwise noted)


Ash emission, seismicity, and inflation increase

"During the first 2 months of 1981 a low level of activity prevailed. White and occasionally brown emissions were observed from both craters. In March, moderate to strong brown and light grey ash-laden emissions were common from Southern crater. Main crater emissions were also grey on several occasions. Explosive sounds from the summit were rarely heard in January and February but became noticeable in the second half of March. Night observations of the volcano in January and February indicated no lava fragment ejections above the craters, although weak glow above Southern crater was reported for 2 January. Sparse ejections of lava fragments from the crater were observed overnight on 14-15 March, and glow above Southern crater was observed on 30 March.

"Background volcano-seismic levels remained fairly steady January-March, but a significant change in seismic activity was the occurrence of strong local earthquakes, possibly of volcanic origin. Preliminary analysis of seismic records showed that five such events were recorded in February and 14 in March.

"The tiltmeters at Manam continued to show a trend of northerly uplift. After the last major eruptive period in 1974 a pattern of summit deflation prevailed until early 1978. Total deflation was about 14 µrad. A definite trend of inflation began in the second half of 1979. The accumulated tilt during the last 2 years was about 6 µrad.

"Aerial inspections were made on 6 and 19 March. Cloud cover prevented detailed observations of summit activity on 6 March but a distinct blue vapour haze was drifting down the N and NW flanks. On 19 March, brown ash-laden ejections from Southern crater were occurring at about half-minute intervals. Main crater continuously released white vapours. Again a blue vapour haze was present, extending about 1 km N of the summit."

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: C. McKee, RVO.


Masaya (Nicaragua) — March 1981 Citation iconCite this Report

Masaya

Nicaragua

11.985°N, 86.165°W; summit elev. 594 m

All times are local (unless otherwise noted)


Gas emission continues unabated; pit crater enlarges

"Scientists from Dartmouth College, IRENA, and the Instituto de Investigaciones Sísmicas report the following based on their continuing cooperative observation of Nicaraguan volcanoes.

"The fourth gas emission crisis of this century continued unabated. Extensive remote measurement of SO2 output (by COSPEC) has revealed a greater variability in emission rates than had previously been recognized (several hundred to several thousand t/d). The pit crater from which the gas is emitted continued to increase slowly in diameter and was strongly elongate in the NW-SE direction. Night observation of the activity was possible and confirmed the complete absence of any incandescence in the pit where lava was visible as recently as November 1978."

Geologic Background. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras caldera and is itself a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The Nindirí and Masaya cones, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic Plinian tephra erupted from Masaya about 6,500 years ago. Historical lava flows cover much of the caldera floor and there is a lake at the far eastern end. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals have caused health hazards and crop damage.

Information Contacts: S. Williams, R. Stoiber, Dartmouth College; D. de Jerez, IRENA; D. Fajardo B., Instituto de Investigaciones Sísmicas.


Momotombo (Nicaragua) — March 1981 Citation iconCite this Report

Momotombo

Nicaragua

12.423°N, 86.539°W; summit elev. 1270 m

All times are local (unless otherwise noted)


Small continuous plume

A small continuous plume continued to be released in early 1981. No new measurements were made. No significant seismicity has occurred recently.

Geologic Background. Momotombo is a young stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows extend down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms an island offshore in Lake Managua. Momotombo has a long record of Strombolian eruptions, punctuated by occasional stronger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after a 10 April 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the south flank.

Information Contacts: R. Stoiber and S. Williams, Dartmouth College; D. de Jerez, IRENA, Managua; D. Fajardo B., Instituto de Investigaciones Sísmicas.


Cerro Negro (Nicaragua) — March 1981 Citation iconCite this Report

Cerro Negro

Nicaragua

12.506°N, 86.702°W; summit elev. 728 m

All times are local (unless otherwise noted)


Minor fumarolic activity

"A flight over the crater in mid-March revealed 1 area of minor fumarolic activity in the SW center region of the crater. No significant seismicity has occurred recently.

Geologic Background. Nicaragua's youngest volcano, Cerro Negro, was created following an eruption that began in April 1850 about 2 km NW of the summit of Las Pilas volcano. It is the largest, southernmost, and most recent of a group of four youthful cinder cones constructed along a NNW-SSE-trending line in the central Marrabios Range. Strombolian-to-subplinian eruptions at intervals of a few years to several decades have constructed a roughly 250-m-high basaltic cone and an associated lava field constrained by topography to extend primarily NE and SW. Cone and crater morphology have varied significantly during its short eruptive history. Although it lies in a relatively unpopulated area, occasional heavy ashfalls have damaged crops and buildings.

Information Contacts: S. Williams, R. Stoiber, Dartmouth College; D. de Jerez, IRENA; D. Fajardo B., Instituto de Investigaciones Sísmicas.


Pacaya (Guatemala) — March 1981 Citation iconCite this Report

Pacaya

Guatemala

14.382°N, 90.601°W; summit elev. 2569 m

All times are local (unless otherwise noted)


Lava flows and Strombolian activity

Newspapers reported that vigorous magmatic activity had begun at Pacaya on 9 February. According to newspapers, activity peaked 18 February at 1730 as lava overflowed the N rim of the crater and began to move down Pacaya's N flank.

Michigan Tech. Univ. geologists climbed Pacaya again on 5 March. Since their last visit 14 February, the level of the lava lake in MacKenney Crater had risen considerably, the two coalesced spatter vents had grown, and an additional small spatter vent had formed in the S part of the crater on the lava lake surface. The new S vent continuously extruded two pahoehoe lava flows but was not the source of any Strombolian explosions. A few small pahoehoe flows were also moving across the E side of the crusted lava lake surface. Nearly continuous weak Strombolian activity occurred from the two older vents. The smaller N vent had many small Strombolian explosions at intervals of 10-20 seconds. From the larger vent, activity was cyclical, consisting of a 1-5-second explosion that ejected spatter to 200-300 m above the vent, followed almost instantly by a large increase in gas emission that peaked in about 1 minute, decreased slowly, then dropped sharply about 30 seconds before the next explosion. Gases above the vent had an intense blue color. The alignment of the three vents in MacKenney Crater indicated that the activity may have been from a fissure trending approximately N-S.

The geologists estimated that the lava flow descending the N flank had a volume of about 2 x 104 m3 on 5 March. They estimated the total volume of 1981 lava at about 1 x 106 m3, for an average eruption rate of about 4 x 104 m3/day. The lava was petrologically similar to lavas from eruptions since 1970, consisting of basalt with abundant plagioclase phenocrysts and sparse olivine phenocrysts.

Geologic Background. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. This complex basaltic volcano was constructed just outside the southern topographic rim of the 14 x 16 km Pleistocene Amatitlán caldera. A cluster of dacitic lava domes occupies the southern caldera floor. The post-caldera Pacaya massif includes the ancestral Pacaya Viejo and Cerro Grande stratovolcanoes and the currently active Mackenney stratovolcano. Collapse of Pacaya Viejo between 600 and 1500 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (Mackenney cone) grew. A subsidiary crater, Cerro Chino, was constructed on the NW somma rim and was last active in the 19th century. During the past several decades, activity has consisted of frequent strombolian eruptions with intermittent lava flow extrusion that has partially filled in the caldera moat and armored the flanks of Mackenney cone, punctuated by occasional larger explosive eruptions that partially destroy the summit of the growing young stratovolcano.

Information Contacts: T. Bornhorst and C. Chesner, Michigan Tech. Univ.


Poas (Costa Rica) — March 1981 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Explosions; incandescence on dome

Activity at Poás had increased, with explosions observed [12] September and 26 December 1980. As of mid-March, ICE and the Univ. Nacional were keeping the volcano under continuous observation. The temperature of the "dome" in the crater lake was 650-750°C and some red areas were seen along fissures in the dome. Lake water temperatures were 50°C, similar to temperatures in the fall of 1980. The pH of the lake had decreased to 0.1. Fumaroles emitted large quantities of water vapor and SO2. Many landslides had occurred in the walls of the main crater.

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: G. Avila, ICE; J. Barquero H., Univ. Nacional, Heredia.


San Cristobal (Nicaragua) — March 1981 Citation iconCite this Report

San Cristobal

Nicaragua

12.702°N, 87.004°W; summit elev. 1745 m

All times are local (unless otherwise noted)


Emissions of SO2 increase by an order of magnitude; high seismicity; incandescence

"A trend of decreasing SO2 emissions had been evident since the small ash eruptions of March 1976. However, San Cristóbal has suddenly reversed this trend, after being in a heightened state of seismic activity since August 1980. In late February, SO2 output increased by approximately an order of magnitude to the several thousand t/d level of the mid-1970's. Flights over the crater in mid-February and mid-March showed evidence of considerable recent slumping in the crater formed by the 1976 eruptions, especially on the N and NW walls. Fumarolic activity was evident all over the crater but was most concentrated in the S and SE margins of the floor and in the lower parts of the walls. No new fumaroles or fissures were observed outside the 1976 crater. Night observation revealed extensive incandescence over much of the crater, even more than that observed in December at Momotombo. High gas concentrations and unstable footing prevented measurement of any fumarole temperatures. Seismic activity continued at high levels, with almost continuous harmonic tremor and at least one earthquake with magnitude greater than 2 (which occurred one week before the elevated SO2 emission was detected)."

Geologic Background. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1745-m-high youngest cone, named San Cristóbal (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km W of San Cristóbal; it and the eroded Moyotepe volcano, 4 km NE of San Cristóbal, are of Pleistocene age. Volcán Casita, containing an elongated summit crater, lies immediately east of San Cristóbal and was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes.

Information Contacts: R. Stoiber and S. Williams, Dartmouth College; D. de Jerez, IRENA; D. Fajardo B., Instituto de Investigaciones Sísmicas.


Santa Maria (Guatemala) — March 1981 Citation iconCite this Report

Santa Maria

Guatemala

14.757°N, 91.552°W; summit elev. 3745 m

All times are local (unless otherwise noted)


Explosive activity continues

On several occasions between 17 February and 2 March, R. W. Hodder and a group of students observed explosive activity at Santiaguito Dome. They saw morning eruptions from Caliente Vent on 17, 23, 24, 26, 27, and 28 February and 2 March, and late afternoon eruptions on 17 February and 2 March.

The group climbed Santiaguito on 23 and 24 February. During one eruption, accretionary lapilli fell, followed by raindrops coated with fine ash. About 1000 on 26 February, a large 30-minute eruption of gas with very little ash occurred from Caliente Vent. The eruption column rose to about 1,800 m, reaching a diameter of about 500 m (much larger than any other observed by Hodder's group) and forming a well-developed anvil-shaped top. At its maximum, the upper 25% of the column was ash-poor, nearly white vapor while the lower 75% darkened downward to a light brown (lighter colored than the 12 February eruption column described last month).

The group saw eruptions at 1000 and 1115 on 28 February during 5 hours of observations. The first consisted of a single 10-minute pulse that sent a vapor column to about 500 m above the vent. The second comprised four pulses in 30 minutes. Each pulse began with a white-topped column that developed a light tan base and an anvil-shaped top as it rose as much as 1,500 m above the vent. Between each pulse there was intense fuming.

Dartmouth College scientists climbed to the summit of Santa María on the morning of 24 March. They provided the following report.

"The plug dome previously observed in the crater of Caliente Vent was clearly visible and appeared to be covered with huge blocks of light gray lava. Four eruptions occurred within 3 hours with repose periods of 20 minutes, 1 hour, and 1 hour 40 minutes. Each was ash-rich and clearly audible from the summit (a distance of 2.8 km). All rose in the gas-thrust phase to approximately the elevation of the summit (a vertical distance of 1,272 m) and beyond convectively.

"Avalanches in the crater and down the SW flank occurred every 5-15 minutes suggesting nearly continuous activity of the dome. The several hundred meter-long lava flow, visible on the SW flank in February 1980 was not visible from the summit but avalanche clouds rising from that area suggested that it was still active there.

"One large fumarole in the NW part of the plug dome was continuously and very vigorously degassing, remaining essentially unchanged even during eruptions. All four eruptions began in the NE and E region of the crater and lasted 2-4 minutes."

Geologic Background. Symmetrical, forest-covered Santa María volcano is part of a chain of large stratovolcanoes that rise above the Pacific coastal plain of Guatemala. The sharp-topped, conical profile is cut on the SW flank by a 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank, and was formed during a catastrophic eruption in 1902. The renowned Plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four vents, with activity progressing W towards the most recent, Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Information Contacts: R. Hodder, Univ. of Western Ontario; T. Bornhorst, C. Chesner, W. Rose, Jr., Michigan Tech. Univ.; S. Williams, M. Mort, Dartmouth College.


Semeru (Indonesia) — March 1981 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Nuées ardentes and lava avalanches; one killed, 272 evacuated

Activity increased 28 March. The first nuée ardente moved about 4 km from the summit down the Kembar and Kobokan Rivers (on the S flank) at 1755. During the following days, increasingly intense nuées ardentes reached a distance of more than 7 km from the summit. Four nuées ardentes and 19 lava avalanches (presumably accompanied by nuées ardentes of eruptive origin) were reported on 29 March and four more nuées ardentes and 36 lava avalanches were observed the next day. As of 31 March, tremors were being continuously recorded by the VSI seismograph about 10 km from the summit.

One person was killed by a nuée ardente and 272 others were evacuated. The ongoing rainy season may cause lahars and associated flooding.

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

Information Contacts: A. Sudradjat and L. Pardyanto, VSI.


Shikotsu (Japan) — March 1981 Citation iconCite this Report

Shikotsu

Japan

42.688°N, 141.38°E; summit elev. 1320 m

All times are local (unless otherwise noted)


Seismicity declines without expected eruption

Local seismicity began to increase in November 1980 and the number of events per month reached 1,211 in February 1981 (figure 3). Seismicity began a gradual decline in early March and by mid-March had reached the usual average of fewer than three recorded earthquakes per day.

Figure (see Caption) Figure 3. Monthly numbers of days with eruptions (top), tremor events (center), and recorded earthquakes (bottom) at Tarumai, January 1978-March 1981. Courtesy of JMA.

Only 87 events were recorded in March. Although the December 1978-May 1979 eruption accompanied the last major increase in seismicity, no eruption has occurred during the current, much larger increase [but see 06:04].

Geologic Background. The 13 x 15 km Shikotsu caldera, largely filled by the waters of Lake Shikotsu, was formed during one of Hokkaido's largest Quaternary eruptions about 31-34,000 years ago. The small andesitic Tarumaesan stratovolcano was then constructed on its SE rim and has been frequently active in historical time. Pyroclastic-flow deposits from Tarumaesan extend nearly to the Pacific coast. Two other Holocene post-caldera volcanoes, Fuppushidake (adjacent to Tarumaesan) and Eniwadake (on the opposite side of the caldera), occur on a line trending NW from Tarumaesan, and were constructed just inside the caldera rim. Minor eruptions took place from the summit of Eniwadake as late as the 17th century. The summit of Tarumaesan contains a small 1.5-km-wide caldera formed during two of Hokkaido's largest historical eruptions, in 1667 and 1739. Tarumaesan is now capped by a flat-topped summit lava dome that formed in 1909.

Information Contacts: JMA, Tokyo.


St. Helens (United States) — March 1981 Citation iconCite this Report

St. Helens

United States

46.2°N, 122.18°W; summit elev. 2549 m

All times are local (unless otherwise noted)


Lava extrusion and small explosion follow deformation and seismicity

March eruptive activity was limited to occasional emission of small steam clouds, at least one of which contained ash. However, significant deformation was measured within the crater, and there was a slight increase in volcanic seismicity during the second half of March. Geologists announced that another eruptive episode was likely if the deformation and seismic trends continued, but none had occurred by press time.

The USGS-University of Washington seismic net recorded fifteen bursts of seismicity in March and five more bursts during the first six days of April. In the past, similar signals have often been correlated with episodes of steam emission, but because of poor weather, correlations with only two such episodes could be confirmed in March: a minor puff on 9 March at 1549, and a steam cloud containing some ash on 27 March at 1441. Newly fallen ash (made up of reworked dome material) observed NE of the volcano 25 March may have been ejected during a burst of seismicity the previous day.

The seismic net began to detect small, low-frequency, shallow events on Mt. St. Helens on 21 March. Fifteen of these discrete volcanic events were recorded by the end of March. Numerous aftershocks of the M 5.5 tectonic event that occurred 13 February about 12 km N of Mt. St. Helens, continued to appear on seismic records through March.

Deformation measurements showed that outward movement of the N-crater rampart resumed in March. Between 9 and 17 March, the rampart moved 7 cm to the N; by 22 March it had advanced 6 cm farther northward; and an additional 3.5 cm of movement was measured by 24 March.

A newly-established leveling net on the crater floor showed pronounced uplift near the lava dome, indicating that the dome was rising. Increasing crater-floor deformation was also demonstrated by accelerations in the rate of widening of a fissure from 3 mm/day to l cm/day and the rate of movement of a thrust fault from 0.5 cm/day to 1 cm/day by late March.

Addendum: On 9 April at about 1800, local seismicity began to increase, to about 1 event per hour at first and to about 2/hr after midnight. The USGS-University of Washington team issued an advisory about midnight stating that an eruption was likely within the next day if seismicity continued to increase.

Periods of constant low-frequency seismicity became more common and by 0230 on 10 April low-frequency activity was continuous. Individual events superimposed on this activity had increased to an average of 6-8/hour by 0600 and remained at that level through the day. At 0821, a small explosion produced an ash-bearing plume that rose to 4.5 km altitude. A light ashfall was reported at a ranger station 40 km to the NE. Although clouds prevented observation of the crater, a USGS helicopter crew could see that this explosion had generated no pyroclastic flows.

About 1900, the pattern of seismic activity started to change. The number of discrete events dropped to 4-6/hr, but these events were slightly stronger and total seismic energy release briefly stayed about the same. However, by midnight there had been a notable decline in both the number of events and seismic energy release, and by 0200 only one to two events were being recorded per hour. Seismicity had essentially ended by 2100-2200 on 11 April.

The weather cleared somewhat late 12 April, and geologists were able to view the crater between 1800 and 1900. New lava extended roughly 75 m NNW from the pre-existing dome. Television station videotape taken between 1900 and 1930 showed significant additional lava extrusion.

Geologic Background. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago and has been the most active volcano in the Cascade Range during the Holocene. Prior to 2200 years ago, tephra, lava domes, and pyroclastic flows were erupted, forming the older St. Helens edifice, but few lava flows extended beyond the base of the volcano. The modern edifice was constructed during the last 2200 years, when the volcano produced basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the north flank, and were witnessed by early settlers.

Information Contacts: D. Swanson, C. Newhall, S. Russell-Robinson, USGS, Vancouver, WA; C. Boyko, A. Adams, S. Malone, E. Endo, C. Weaver, University of Washington; R. Tilling, USGS, Reston, VA.


Telica (Nicaragua) — March 1981 Citation iconCite this Report

Telica

Nicaragua

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

All times are local (unless otherwise noted)


Holes in crater wall emit vapor plume; occasional minor ash eruptions

"Two flights were made over the summit crater of Telica, in mid-February and mid-March. Two large holes (each with a diameter of approximately 20-30 m) occurred high on the NW wall of the crater. They are reported (by Alain Creusot, Instituto Nicaraguense de Energía) to coalesce at depth. One or both of them emitted a continuous vapor plume. Occasional minor ash eruptions were reported by local people."

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

Information Contacts: R. Stoiber, S. Williams, Dartmouth College; D. de Jerez, IRENA; D. Fajardo B., Instituto de Investigaciones Sísmicas.


Whakaari/White Island (New Zealand) — March 1981 Citation iconCite this Report

Whakaari/White Island

New Zealand

37.52°S, 177.18°E; summit elev. 294 m

All times are local (unless otherwise noted)


Explosions and seismicity; tephra and tilt measured

NZGS personnel visited White Island on 17 January and 6 March, and overflew the volcano on 24 February after reports of explosive eruptions in January. On 17 January, a weakly convoluting gas column charged with light brown ash was issuing from the active vent in the S part of 1978 Crater. Gray tephra covered the main crater floor. Since the magmatic activity in early November, about 500 mm of ash had been deposited near the 1978 Crater rim, about 230 mm since 2 December. Two or possibly three generations of impact craters, the youngest perhaps less than a day or two old, were found 250-600 m NE of the active vent, with concentrations of up to 3 craters/m2 300-400 m away. Crater diameters ranged from 30 mm to 1.2 m. Blocks up to 0.7 m in diameter were found in some of the impact craters, but no fresh magma appeared to have been ejected. The apparent near-vertical final trajectory of the blocks in the impact craters was striking.

Seismic records showed that periods of high-frequency tremor occurred 7-13, 17-19, 22-23 and 25-28 January, and 30 January-11 February. Short bursts of harmonic tremor were recorded after the high-frequency tremor declined. Large discrete events (eruption sequences) were recorded on 24 and 29 January and 6, 12, 17, 23 and 24 February. The eruption accompanying the 24 January event produced ashfall at Cape Runaway (75 km E of White Island, on the mainland) and was witnessed by P. M. Otway (NZGS).

So little gas and tephra were being emitted during the 24 February overflight that viewing was excellent. The main crater floor appeared to be covered by a thick layer of red-brown principally fine-grained tephra. Impact craters formed since 17 January pocked the floor to 600 m E of the active vent, the greatest range since the March 1977 eruptions.

On 6 March, emissions from the active vent, entrenched in a subcrater at least 200 m deep, were very low. The rim of 1978 Crater showed no major changes, but a large portion of the crater floor N of the active vent had been raised several m by rapid accumulation of tephra between 17 January and 24 February. At the E edge of 1978 Crater rim, 410 mm of new tephra overlay earlier deposits. Within a kilometer to the E, the new tephra thinned to about 8 mm. The surface layer was a fine pink ash (mean diameter about 63 µm) containing abundant lithic clasts, subordinate crystals of pyroxene and olivine and minor amounts of glassy, weakly to moderately vesicular, essential, low-silica andesite. This layer was underlain by a finer green ash containing a greater percentage of essential clasts.

A few new impact craters had formed just outside 1978 Crater's E rim, some occupied by lithic blocks that were not coated with ash. Some of the older impact craters scattered across the main crater floor contained buried scoriaceous bombs, apparently of recent magmatic origin.

Fumaroles checked from the air in February were monitored in March. The inspection team measured minimum temperatures of 490°-650°C at 3 fumaroles formed within the past year E of 1978 Crater rim. One is the most energetic feature on the island other than the active vent.

The March levelling survey showed that subsidence had continued after the previous survey on 2 December. The volcano had deflated about 300 µrad since May, the peak of a 6-month period of inflation (figure 8). The greatest deformation, 12-13 mm since December and a total of 60 mm since May, was about in the center of the main crater, near the zone of fumarolic activity just E of 1978 Crater.

Geologic Background. The uninhabited Whakaari/White Island 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 SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused 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. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Information Contacts: B. Scott, B. Houghton, and I. Nairn, NZGS, Rotorua.

Atmospheric Effects

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

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

Special Announcements

Special announcements of various kinds and obituaries.

Special Announcements

Additional Reports

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

Kermadec Islands


Floating Pumice (Kermadec Islands)

1986 Submarine Explosion


Tonga Islands


Floating Pumice (Tonga)


Fiji Islands


Floating Pumice (Fiji)


Andaman Islands


False Report of Andaman Islands Eruptions


Sangihe Islands


1968 Northern Celebes Earthquake


Southeast Asia


Pumice Raft (South China Sea)

Land Subsidence near Ham Rong


Ryukyu Islands and Kyushu


Pumice Rafts (Ryukyu Islands)


Izu, Volcano, and Mariana Islands


Acoustic Signals in 1996 from Unknown Source

Acoustic Signals in 1999-2000 from Unknown Source


Kuril Islands


Possible 1988 Eruption Plume


Aleutian Islands


Possible 1986 Eruption Plume


Mexico


False Report of New Volcano


Nicaragua


Apoyo


Colombia


La Lorenza Mud Volcano


Pacific Ocean (Chilean Islands)


False Report of Submarine Volcanism


West Indies


Mid-Cayman Spreading Center


Atlantic Ocean (northern)


Northern Reykjanes Ridge


Azores


Azores-Gibraltar Fracture Zone


Antarctica and South Sandwich Islands


Jun Jaegyu

East Scotia Ridge


Additional Reports (database)

08/1997 (SEAN 22:08) False Report of Mount Pinokis Eruption

False report of volcanism intended to exclude would-be gold miners

12/1997 (SEAN 22:12) False Report of Somalia Eruption

Press reports of Somalia's first historical eruption were likely in error

11/1999 (SEAN 24:11) False Report of Sea of Marmara Eruption

UFO adherent claims new volcano in Sea of Marmara

05/2003 (SEAN 28:05) Har-Togoo

Fumaroles and minor seismicity since October 2002

12/2005 (SEAN 30:12) Elgon

False report of activity; confusion caused by burning dung in a lava tube



False Report of Mount Pinokis Eruption (Philippines) — August 1997

False Report of Mount Pinokis Eruption

Philippines

7.975°N, 123.23°E; summit elev. 1510 m

All times are local (unless otherwise noted)


False report of volcanism intended to exclude would-be gold miners

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.


False Report of Somalia Eruption (Somalia) — December 1997

False Report of Somalia Eruption

Somalia

3.25°N, 41.667°E; summit elev. 500 m

All times are local (unless otherwise noted)


Press reports of Somalia's first historical eruption were likely in error

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.


False Report of Sea of Marmara Eruption (Turkey) — November 1999

False Report of Sea of Marmara Eruption

Turkey

40.683°N, 29.1°E; summit elev. 0 m

All times are local (unless otherwise noted)


UFO adherent claims new volcano in Sea of Marmara

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.


Har-Togoo (Mongolia) — May 2003

Har-Togoo

Mongolia

48.831°N, 101.626°E; summit elev. 1675 m

All times are local (unless otherwise noted)


Fumaroles and minor seismicity since October 2002

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 (see Caption) 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 (see Caption) 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 (see Caption) 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.


Elgon (Uganda) — December 2005

Elgon

Uganda

1.136°N, 34.559°E; summit elev. 3885 m

All times are local (unless otherwise noted)


False report of activity; confusion caused by burning dung in a lava tube

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/).