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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

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

Nyiragongo (DR Congo) Lava lake persists during June-November 2019

Ebeko (Russia) Frequent moderate explosions, ash plumes, and ashfall continue through November 2019

Nevado del Ruiz (Colombia) Intermittent ash plumes with significant gas and steam emissions during January 2016-December 2017



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/).


Nyiragongo (DR Congo) — December 2019 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Lava lake persists during June-November 2019

Nyiragongo is a stratovolcano with a 1.2 km-wide summit crater containing an active lava lake that has been present since at least 1971. It is located the Virunga Volcanic Province (VVP) in the Democratic Republic of the Congo, part of the western branch of the East African Rift System. Typical volcanism includes strong and frequent thermal anomalies, primarily due to the lava lake, incandescence, gas-and-steam plumes, and seismicity. This report updates activity during June through November 2019 with the primary source information from monthly reports by the Observatoire Volcanologique de Goma (OVG) and satellite data.

In the July 2019 monthly report, OVG stated that the lava lake level had dropped during the month, with incandescence only visible at night (figure 68). In addition, the small eruptive cone within the crater, which has been active since 2014, decreased in activity during this timeframe. A MONUSCO (United Nations Stabilization Mission in the Democratic Republic of the Congo) helicopter overflight took photos of the lava lake and observed that the level had begun to rise on 27 July. Seismicity was relatively moderate throughout this reporting period; however, on 9-16 July and 21 August strong seismic swarms were recorded.

Figure (see Caption) Figure 68. Webcam images of Nyiragongo on 20 July 2019 where incandescence is not visible during the day (left) but is observed at night (right). Incandescence is accompanied by gas-and-steam emissions. Courtesy of OVG.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data continued to show frequent and strong thermal anomalies within 5 km of the crater summit through November 2019 (figure 69). Similarly, the MODVOLC algorithm reported almost daily thermal hotspots (more than 600) within the summit crater between June 2019 through November. These data are corroborated with Sentinel-2 thermal satellite imagery and a photo from OVG on 19 December 2019 showing the active lava lake (figures 70 and 71).

Figure (see Caption) Figure 69. Thermal anomalies at Nyiragongo from 3 January through November 2019 as recorded by the MIROVA system (Log Radiative Power) were frequent and strong. Courtesy of MIROVA.
Figure (see Caption) Figure 70. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) showed ongoing thermal activity (bright yellow-orange) at Nyiragongo during June through November 2019. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 71. Photo of the active lava lake in the summit crater at Nyiragongo on 19 December 2019. Incandescence is accompanied by a gas-and-steam plume. Courtesy of OVG via Charles Balagizi.

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

Information Contacts: Observatoire Volcanologique de Goma (OVG), Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; 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); Charles Balagizi (Twitter: @CharlesBalagizi, https://twitter.com/CharlesBalagizi).


Ebeko (Russia) — December 2019 Citation iconCite this Report

Ebeko

Russia

50.686°N, 156.014°E; summit elev. 1103 m

All times are local (unless otherwise noted)


Frequent moderate explosions, ash plumes, and ashfall continue through November 2019

Activity at Ebeko includes frequent explosions that have generated ash plumes reaching altitudes of 1.5-6 km over the last several years, with the higher altitudes occurring since mid-2018 (BGVN 43:03, 43:06, 43:12, 44:07). Ash frequently falls in Severo-Kurilsk (7 km ESE), which is monitored by the Kamchatka Volcanic Eruptions Response Team (KVERT). This activity continued during June through November 2019; the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

Explosive activity during December 2018 through November 2019 often sent ash plumes to altitudes between 2.2 to 4.5 km, or heights of 1.1 to 3.4 km above the crater (table 8). Eruptions since 1967 have originated from the northern crater of the summit area (figure 20). Webcams occasionally captured ash explosions, as seen on 27 July 2019(figure 21). KVERT often reported the presence of thermal anomalies; particularly on 23 September 2019, a Sentinel-2 thermal satellite image showed a strong thermal signature at the crater summit accompanied by an ash plume (figure 22). Ashfall is relatively frequent in Severo-Kurilsk (7 km ESE) and can drift in different direction based on the wind pattern, which can be seen in satellite imagery on 30 October 2019 deposited NE and SE from the crater(figure 23).

Table 8. Summary of activity at Ebeko, December 2018-November 2019. S-K is Severo-Kurilsk (7 km ESE of the volcano). TA is thermal anomaly in satellite images. Data courtesy of KVERT.

Date Plume Altitude (km) Plume Distance Plume Directions Other Observations
30 Nov-07 Dec 2018 3.6 -- E Explosions. Ashfall in S-K on 1, 4 Dec.
07-14 Dec 2018 3.5 -- E Explosions.
25 Jan-01 Feb 2019 2.3 -- -- Explosions. Ashfall in S-K on 27 Jan.
02-08 Feb 2019 2.3 -- -- Explosions. Ashfall in S-K on 4 Feb.
08-15 Feb 2019 2.5 -- -- Explosions. Ashfall in S-K on 11 Feb.
15-22 Feb 2019 3.6 -- -- Explosions.
22-26 Feb 2019 2.5 -- -- Explosions. Ashfall in S-K on 23-26 Feb.
01-02, 05 Mar 2019 -- -- -- Explosions. Ashfall in S-K on 1, 5 Mar.
08-10 Mar 2019 4 30 km ENE Explosions. Ashfall in S-K on 9-10 Mar.
15-19, 21 Mar 2019 4.5 -- -- Explosions. Ashfall in S-K on 15-16, 21 Mar.
22, 24-25, 27-28 Mar 2019 4.2 -- -- Explosions. Ashfall in S-K on 24-25, 27 Mar.
29-31 Mar, 01, 04 Apr 2019 3.2 -- -- Explosions. Ashfall in S-K on 31 Mar. TA on 31 Mar.
09 Apr 2019 2.2 -- -- Explosions.
12-15 Apr 2019 3.2 -- -- Explosions. TA on 13 Apr.
21-22, 24 Apr 2019 -- -- -- Explosions.
26 Apr-03 May 2019 3 -- -- Explosions.
04, 06-07 May 2019 3.5 -- -- Explosions. TA on 6 May.
12-13 May 2019 2.5 -- -- Explosions. TA 12-13 May.
16-20 May 2019 2.5 -- -- Explosions. TA on 16-17 May.
25-28 May 2019 3 -- -- Explosions. TA on 27-28 May.
03 Jun 2019 3 -- E Explosions.
12 Jun 2019 -- -- -- TA.
14-15 Jun 2019 2.5 -- NW, NE Explosions.
21-28 Jun 2019 -- -- -- TA on 23 June.
28 Jun-05 Jul 2019 4.5 -- Multiple Explosions. TA on 29 Jun, 1 Jul.
05-12 Jul 2019 3.5 -- S Explosions. TA on 11 Jul.
15-16 Jul 2019 2 -- S, SE Explosions. TA on 13-16, 18 Jul.
20-26 Jul 2019 4 -- Multiple Explosions. TA on 18, 20, 25 Jul
25-26, 29 Jul, 01 Aug 2019 2.5 -- Multiple Explosions.
02, 04 Aug 2019 3 -- SE Explosions. TA on 2, 4 Aug.
10-16 Aug 2019 3 -- SE Explosions. TA on 10, 12 Aug.
17-23 Aug 2019 3 -- SE Explosions. TA on 16 Aug.
23, 27-28 Aug 2019 3 -- E Explosions. TA on 23 Aug.
30-31 Aug, 03-05 Sep 2019 3 -- E, SE Explosions on 30 Aug, 3-5 Sep. TA on 30-31 Aug.
07-13 Sep 2019 3 -- S, SE, N Explosions. Ashfall in S-K on 6 Sep. TA on 8 Sep.
13-15, 18 Sep 2019 2.5 -- E Explosions. TA on 15 Sep.
22-23 Sep 2019 3 -- E, NE Explosions. Ashfall in S-K.
27 Sep-04 Oct 2019 4 -- SE, E, NE Explosions.
07-08, 10 Oct 2019 2.5 -- E, NE Explosions. Ashfall in S-K on 4-5 Oct. Weak TA on 8 Oct.
11-18 Oct 2019 4 -- NE Explosions. Ashfall in S-K on 15 Oct. Weak TA on 12 Oct.
18, 20-21, 23 Oct 2019 3 -- N, E, SE Explosions. Weak TA on 20 Oct.
25-26, 29-30 Oct 2019 2.5 -- E, NE Explosions. Weak TA on 29 Oct.
02-06 Nov 2019 3 -- N, E, SE Explosions.
11-12, 14 Nov 2019 3 -- E, NE Explosions.
15-17, 20 Nov 2019 3 -- SE, NE Explosions.
22-23, 28 Nov 2019 2.5 -- SE, E Explosions. Ashfall in S-K on 23 Nov.
Figure (see Caption) Figure 20. Satellite image showing the summit crater complex at Ebeko, July 2019. Monthly mosaic image for July 2019, copyright 2019 Planet Labs, Inc.
Figure (see Caption) Figure 21. Webcam photo of an explosion and ash plume at Ebeko on 27 July 2019. Videodata by IMGG FEB RAS and KB GS RAS (color adjusted and cropped); courtesy of Institute of Volcanology and Seismology FEB RAS, KVERT.
Figure (see Caption) Figure 22. Satellite images showing an ash explosion from Ebeko on 23 September 2019. Top image is in natural color (bands 4, 3, 2). Bottom image is using "Atmospheric Penetration" rendering (bands 12, 11, 8A) to show a thermal anomaly in the northern crater visible around the rising plume. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 23. A satellite image of Ebeko from Sentinel-2 (LC1 natural color, bands 4, 3, 2) on 30 October 2019 showing previous ashfall deposits on the snow going in multiple directions. Courtesy of Sentinel Hub Playground.

The MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data detected four low-power thermal anomalies during the second half of July, and one each in the months of June, August, and October; no activity was recorded in September or November MODVOLC thermal alerts observed only one thermal anomaly between June through November 2019.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Planet Labs, Inc. (URL: https://www.planet.com/); 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/).


Nevado del Ruiz (Colombia) — December 2019 Citation iconCite this Report

Nevado del Ruiz

Colombia

4.892°N, 75.324°W; summit elev. 5279 m

All times are local (unless otherwise noted)


Intermittent ash plumes with significant gas and steam emissions during January 2016-December 2017

Nevado del Ruiz is a glaciated volcano in Colombia (figure 86). It is known for the 13 November 1985 eruption that produced an ash plume and associated pyroclastic flows onto the glacier, triggering a lahar that approximately 25,000 people in the towns of Armero (46 km west) and Chinchiná (34 km east). Since 1985 activity has intermittently occurred at the Arenas crater. The eruption that began on 18 November 2014 included ash plumes dominantly dispersed to the NW of Arenas crater (BGVN 42:06). This bulletin summarizes activity during January 2016 through December 2017 and is based on reports by Servicio Geologico Colombiano and Observatorio Vulcanológico y Sismológico de Manizales, Washington Volcanic Ash Advisory Center (VAAC) notices, and satellite data.

Figure (see Caption) Figure 86. A satellite image of Nevado del Ruiz showing the location of the active Arenas crater. September 2019 Monthly Mosaic image copyright Planet Labs 2019.

Activity during 2016. Throughout January 2016 ash and steam plumes were observed reaching up to a few kilometers. Significant water vapor and volcanic gases, especially SO2, were detected throughout the month. Thermal anomalies were detected in the crater on the 27th and 31st. Significant water vapor and volcanic gas plumes, in particular SO2, were frequently detected by the SCAN DOAS (Differential Optical Absorption Spectroscopy) station and satellite data (figure 87). A M3.2 earthquake was felt in the area on 18 January. Similar activity continued through February with notable ash plumes up to 1 km, and a M3.6 earthquake was felt on the 6th. Ash and gas-and-steam plumes were reported throughout March with a maximum of 3.5 km on the 31st (figure 88). Significant water vapor and gas plumes continued from the Arenas crater throughout the month, and a thermal anomaly was noted on the 28th. An increase in seismicity was reported on the 29th.

Figure (see Caption) Figure 87. Examples of SO2 plumes from Nevado del Ruiz detected by the Aura/OMI instrument on 10, 26, and 31 January 2019. Courtesy of Goddard Space Flight Center.
Figure (see Caption) Figure 88. Ash plumes at Nevado del Ruiz during March. Webcam images courtesy of Servicio Geologico Colombiano, various 2016 reports.

The activity continued into April with a M 3.0 earthquake felt by nearby inhabitants on the 8th, an increase in seismicity reported in the week of 12-18, and another significant increase on the 28th with earthquakes felt around Manizales. Thermal anomalies were noted during 12-18 April with the largest on the 16th. Ash plumes continued through the month as well as significant steam-and-gas plumes. Ashfall was reported in Murillo on the 29th.

The elevated activity continued through May with significant steam plumes up to 1.7 km above the crater during the week of 10-16. Thermal anomalies were reported on the 11th and 12th. Steam, gas, and ash plumes reached 2.5 km above the crater and dispersed to the W and NW. Ashfall was reported in La Florida on the 20th (figure 89) and multiple ash plumes on the 22nd reached 2.5 km and resulted in the closure of the La Nubia airport in Manizales. Ash and gas-and-steam emission continued during June (figure 90).

Figure (see Caption) Figure 89. Ash plumes at Nevado del Ruiz on 17, 18, and 20 May 2016 with fine ash deposited on a car in La Florida, Manizales on the 20th. Webcams located in the NE Guali sector of the volcano, courtesy of Servicio Geologico Colombiano 20 May 2016 report.
Figure (see Caption) Figure 90. Examples of gas-and-steam and ash plumes at Nevado del Ruiz during June and July 2016. Courtesy of Servicio Geologico Colombiano (7 July 2016 report).

Similar activity was reported in July with gas-and-steam and ash plumes often dispersing to the NW and W. Ashfall was reported to the NW on 16 July (figure 91). Drumbeat seismicity was detected on 13, 15, 16, and 17 July, with two hours on the 16th being the longest duration episode do far. Drumbeat seismicity was noted by SGC as indicating dome growth. Significant water vapor and gas emissions continued through August. Ash plumes were reported through the month with plumes up to 1.3 km above the crater on 28 and 2.3 km on 29. Similar activity was reported through September as well as a thermal anomaly and ash deposition apparent in satellite data (figure 92). Drumbeat seismicity was noted again on the 17th.

Figure (see Caption) Figure 91. The location of ashfall resulting from an explosion at Nevado del Ruiz on 16 July 2016 and a sample of the ash under a microscope. The ash is composed of lithics, plagioclase and pyroxene crystals, and minor volcanic glass. Courtesy of Servicio Geologico Colombiano (16 July 2016 report).
Figure (see Caption) Figure 92. This Sentinel-2 thermal infrared satellite image shows elevated temperatures in the Nevado del Ruiz Arenas crater (yellow and orange) on 16 September 2016. Ash deposits are also visible to the NW of the crater. In this image blue is snow and ice. False color (urban) satellite image (bands 12, 11, 4) courtesy of Sentinel Hub Playground.

During the week of 4-10 October it was noted that activity consisting of regular ash plumes had been ongoing for 22 months. Ash plumes continued with reported plumes reaching 2.5 above the crater throughout October (figure 93), accompanied by significant steam and water vapor emissions. A M 4.4 earthquake was felt nearby on the 7th. Similar activity continued through November and December 2016 with plumes consisting of gas and steam, and sometimes ash reaching 2 km above the crater.

Figure (see Caption) Figure 93. An ash plume rising above Nevado del Ruiz on 27 October 2016. Courtesy of Servicio Geologico Colombiano.

Activity during 2017. Significant steam and gas emissions, especially SO2, continued into early 2017. Ash plumes detected through seismicity were confirmed in webcam images and through local reports; the plumes reached a maximum height of 2.5 km above the volcano on the 6th (figure 94). Drumbeat seismicity was recorded during 3-9, and on 22 January. Inflation was detected early in the month and several thermal anomalies were noted.

Intermittent deformation continued into February. Significant steam-and-gas emissions continued with intermittent ash plumes reaching 1.5-2 km above the volcano. Thermal anomalies were noted throughout the month and there was a significant increase in seismicity during 23-26 February.

Figure (see Caption) Figure 94. Ash plumes at Nevado del Ruiz on 6 January 2017. Courtesy of Servicio Geologico Colombiano.

Thermal anomalies continued to be detected through March. Ash plumes continued to be observed and recorded in seismicity and maximum heights of 2 km above the volcano were noted. Deflation continued after the intermittent inflation the previous month. On 10-11 April a period of short-duration and very low-energy drumbeat seismicity was recorded. Significant gas and steam emission continued through April with intermittent ash plumes reaching 1.5 km above the volcano. Thermal anomalies were detected early in the month.

Unrest continued through May with elevated seismicity, significant steam-and-gas emissions, and ash plumes reaching 1.7 km above the crater. Five episodes of drumbeat seismicity were recorded on 29 May and intermittent deformation continued. There were no available reports for June and July.

Variable seismicity was recorded during August and deflation was measured in the first week. Gas-and-steam plumes were observed rising to 850 m above the crater on the 3rd, and 450 m later in the month. A thermal anomaly was noted on the 14th. There were no available reports for September through December.

On 18 December 2017 the Washington VAAC issued an advisory for an ash plume to 6 km that was moving west and dispersing. The plume was described as a "thin veil of volcanic ash and gasses" that was seen in visible satellite imagery, NOAA/CIMSS, and supported by webcam imagery.

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

Information Contacts: Servicio Geologico Colombiano (SGC), Diagonal 53 No. 34-53 - Bogotá D.C., Colombia (URL: https://www2.sgc.gov.co/volcanes/index.html); Observatorio Vulcanológico y Sismológico de Manizales (URL: https://www.facebook.com/ovsmanizales); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

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Bulletin of the Global Volcanism Network - Volume 36, Number 04 (April 2011)

Managing Editor: Richard Wunderman

Arenal (Costa Rica)

Activity and seismicity decrease; new analysis of acid-rain

Endeavour Segment (Canada)

Acoustic imaging of ongoing hydrothermal venting

Eyjafjallajokull (Iceland)

Eruption ended in late 2010; sample of growing literature on the eruption

Irazu (Costa Rica)

Crater lake dries and regional acid-rain report

Machin (Colombia)

Seismic and non-eruptive unrest detected in 2004, 2008, 2009, and again in 2010

Poas (Costa Rica)

Photos of phreatic eruptions from acid lake; surrounding vegetation damaged by gases

Ranau (Indonesia)

Fish kill in April 2011 strikes hot-spring areas of intra-caldera lake

Rincon de la Vieja (Costa Rica)

Fumarolically active but non-eruptive through January 2011

Sheveluch (Russia)

Ongoing dome growth into early 2011; and pyroclastic flows of 27 October 2010



Arenal (Costa Rica) — April 2011 Citation iconCite this Report

Arenal

Costa Rica

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

All times are local (unless otherwise noted)


Activity and seismicity decrease; new analysis of acid-rain

Our previous report about Arenal discussed ongoing sporadic eruptive behavior, preliminary information about the 24 May 2010 dome collapse, and the higher frequency of rockfalls through September 2010 (BGVN 35:07). Since October 2010, volcanic activity at Arenal appears to be decreasing. Events like the explosion on 24 July 2010, discussed below (see figure 110) have become rare. Reports from Costa Rica's Volcanological and Seismological Observatory and National University (OVSICORI-UNA) include direct observations of summit activity, seismic analysis, and acid-rain data and provide the basis for this report covering the 24 May, 2010 event in addition to activity from October 2010 to May 2011.

Figure (see Caption) Figure 110. At 0538 on 24 July 2010 (local time) an ash explosion at Arenal was recorded seismically and its resulting cloud was photographed. In the lower left-hand corner is the seismic trace of the event, which began suddenly and saturated the record (seismic station VACR; OVSICORI-UNA). Courtesy of Phil Slosberg (OVSICORI-UNA).

Incandescent avalanche of 24 May 2010. Sudden activity down Arenal's SW flank on 24 May 2010 produced long, incandescent avalanches and pyroclastic flows, forcing the National Park to evacuate visitors on this day. No injuries or damage to infrastructure had been reported during Arenal's activity in May 2010. Previous pyroclastic events had also caused evacuations in June 2009, June 2008, and September 2007.

Beginning at noon on 24 May, incandescent avalanches descended from the summit dome. They affected a sector that has been subject to avalanches in the last 3 years (see figure 111). A field investigation by OVSICORI on 31 May found that material fell from the summit down to 1,200 m elevation and accumulating in a toe 400 m x 80 m. The majority of blocks surpassed 2 m in diameter. Deposits from the dome collapse were still hot when they arrived at the forest that borders Río Agua Caliente. The OVSICORI-UNA field report of 31 May 2010 contains photos and additional details. Several sections of the river scarp show signs of being struck and eroded by direct impact of the incandescent blocks that arrived with high speed. The dome that supplied the block-and-ash flows became visibly deflated but activity culminated through the week with the formation of a new dome toward the E side of the summit. The formation and destruction of domes at the top of Crater C is very common. These domes reach ten's of meters in size and frequently collapse violently, especially when they are destabilized at the crater rim.

Figure (see Caption) Figure 111. Changes in morphology at Arenal's Crater C are visible owing to the 24 May 2010 dome collapse. Located on the eastern side of the summit, the point of failure was attributed to the "Unstable area." Courtesy of E. Duarte (OVSICORI-UNA).

Decreasing activity. The number of explosive events peaked in February 2010, became regular up to October, but since mid-October they have become sporadic. No lava flows or night-time incandescence was observed on the flanks. Gas emission continued at the active Crater C and fumarolic activity was continuous at Crater D, the pre-1968 summit crater.

Acid-rain affected Arenal's flanks and the NE, E, and SE flanks showed a loss of vegetation. These conditions plus the high amounts of rainfall aggravated erosion on the steep slopes; rockfalls and landslides continued to occur in these valleys: Calle de Arenas, Manolo, Guillermina, and Río Agua Caliente. OVSICORI-UNA released a report on acid-rain measurements that began on 9 April 2003 and ended on 30 November 2010; data from four stations showed generally decreasing acidity with time (figure 112). The trend steadily increased from pH ~4 to ~4.5 for all stations. Although irregular spikes are recorded, the low outliers were generally less acidic with time.

Figure (see Caption) Figure 112. Variation of the pH (level of acidity) of rain-water collected from four stations on Arenal. Data points represent measurements from 9 April 2003 to 30 November 2010. Courtesy of OVSICORI-UNA.

Waldo Taylor assessed seismic data from the local network. The 2010 mid-year ICE report discussed seismicity and the general trend shown in table 26. The large spike in seismic events from 2009 dropped off abruptly the following year.

Table 26. Earthquakes counted at Arenal during 2005-2010. Courtesy of ICE.

Year Number of earthquakes
2005 3
2006 12
2007 15
2008 47
2009 239
2010 56

Gerardo J. Soto discussed Arenal seismicity. "In general terms, the average magnitude increased from 2.0 in 2006 to 2.3 in 2010. The biggest was M 4.1 in 1 November 2009. Mean [focal] depth deepened from 5.5 km in 2006 to about 2 km in 2010. Most of them were between 2 and 5 km deep in 2009-2010, and down to 9 km deep in 2010.

"The number of [respective] earthquakes from September through December 2010 decreased monthly [in the sequence] 24, 12, 9, 3. Epicenters shifted from SE to NW quadrangle of the volcano through time.

"We preliminarily interpret this as a possible withdrawal of magma below the volcano, [on the basis of] focal mechanisms."

Secondary hazards. With Arenal's decrease in explosive activity, no ash collection has been possible this year (2011). A network of seven stations exists for regular sampling. The most effusive event occurred in 1968 when roughly 2 x 105 metric tons of ash fell on the flanks. Later, a hydroelectric project was completed in the 1970s and filled the basin below the volcano with 2.416 x 106 m3 of water (the maximum storage capacity), forming Lake Arenal. From 1992 to 1997, the annual sediment load into the lake contained 1.4% remobilized material from Arenal.

Future activity at Arenal within the next 100 years may include large eruptions with the potential to produce 10 million metric tons of volcanic sediments; within the next 200 years an extreme event could contribute 107 metric tons of volcaniclastics to Lake Arenal (Soto, 1998). The distribution of volcaniclastic sediments is largely controlled by the Río Agua Caliente, a drainage connecting tributaries from Arenal's southern flank. Roughly every 2-5 years there are relatively large debris flows along this river. As recently as the first week of May 2011, intense flooding damaged a bridge by severely undermining the concrete abutments (G.J. Soto, personal communication).

Satellite thermal alerts. Since 15 September 2010 there have been no MODVOLC satellite thermal alerts through February 2011.

References. Soto, G.J., 1998, Cálculo de ceniza eyectada por el Volcán Arenal y ceniza caída en el embalse durante el período 1992-1997; Informe OSV.98.05.ICE, 18 pp. (in Spanish)

OVSICORI-UNA, 2010, Cambios Morfológicos y Avalanchas Incandescentes del 24 de Mayo en el Volcán Arenal. (in Spanish) (URL: http://www.ovsicori.una.ac.cr/vulcanologia/informeDeCampo/2010/InfcampAremayo10.pdf)

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: Phil Slosberg and Eliecer Duarte, Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Gerardo J. Soto, Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica; Waldo Taylor, Sismológico y Vulcanológico de Arenal y Miravalles (OSIVAM), Oficina de Sismología y Vulcanología (OSV), Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica.


Endeavour Segment (Canada) — April 2011 Citation iconCite this Report

Endeavour Segment

Canada

47.95°N, 129.1°W; summit elev. -2050 m

All times are local (unless otherwise noted)


Acoustic imaging of ongoing hydrothermal venting

The Grotto vent cluster contains an assemblage of black smoker vents that lie within the Main Endeavour Field on the northern Juan de Fuca ridge (Bemis, 2001; Rona and others, 2001, 2010a; Bobbitt, 2007) (figure 4). New imagery of submarine plume behavior and properties was achieved with a new acoustic system that extends underwater observational distances beyond those of light to image buoyant plumes of submarine black smokers in 3-dimensions and image areas of diffuse flow seeping from the sea floor in 2-dimensions (Rona, 2011; Rona and others, 2010a, 2010b, and 2011).

Figure (see Caption) Figure 4. Map of Main Endeavour Field, Juan de Fuca Ridge (grid system in meters), showing the location of the Grotto Vent at grid coordinates of about 6115 and 4920. Note scale-the entire Endeavour Field is only ~400 m long. According to Merle (2006) Grotto vent resides at 47.95°N latitude, 129.10°W longitude, and at a depth of ~2,196 m.

The Cabled Observatory Vent Imaging Sonar (COVIS) was installed in September 2010 (Light, 2011). Operations were initiated with in situ sensors in the NEPTUNE (North-East Pacific Time-Series Underwater Networked Experiments) Canada Program cabled observatory on the Main Endeavour Field (MEF) of the Juan de Fuca Ridge, nearly 370 km (200 nautical miles) off British Columbia, Canada, in the NE Pacific Ocean (figures 5 and 6). NEPTUNE is a Canadian research facility designed for regional-scale underwater ocean investigations focusing on continuous monitoring of temperature, chemistry, biodiversity, and motion. This data will be broadcast via the Internet for scientists, students, educators and the public to collaborate and promote investigations into: underwater volcanic processes; earthquakes and tsunamis; minerals, metals, and hydrocarbons; ocean-atmosphere interactions; climate change; greenhouse gas cycling in the ocean; marine ecosystems; long-term changes in ocean productivity; marine mammals; fish stocks; pollution and toxic blooms. The public can gain a more in-depth understanding of the seafloor, while ocean scientists can run deep-water experiments from labs and universities anywhere around the world.

Figure (see Caption) Figure 5. Map of NEPTUNE Canada Program's six submarine sites with multiple sensors connected to a high-speed optical cable linked with University of Victoria in British Columbia, Canada. The Main Endeavour Field, labeled as Endeavor (in red), one of the instrumented sites, is ~350 km WSW from Port Alberni. Over the project's 25-year lifespan, Endeavor will collect data for underwater volcanic processes, seismicity, plate tectonics, hydrothermal vent systems, and deep sea ecosystems. Courtesy of NEPTUNE Canada (2011).

During a research cruise in September-October 2010, scientists from the University of Washington and Rutgers University connected COVIS to the NEPTUNE Canada cable system for the first time and initiated data acquisition on 29 September 2010. COVIS, equipped with a customized multibeam sonar, 400/200 kHz projectors, and a rotator system to orient acoustic transducers, was positioned to acquire acoustic data from a fixed site on the floor of the ridge's axial valley at a range of tens of meters from the Grotto vent cluster in the MEF (figure 6).

Figure (see Caption) Figure 6. COVIS acoustic image, oriented NE on the left to NW on the right, made at 0600 UTC on 11 October 2010, looking S at black smoker plumes and areas of diffuse flow draped over bathymetry of the Grotto vent cluster (Jackson and others, 2003) in the Main Endeavour Field, Juan de Fuca Ridge. The image was made when tidal currents were minimal (e.g., near slack tide). The larger plume is from the N tower edifice at the NW end, and the smaller plumes are from the NE end of Grotto vent at the in-situ experiments. The legend (at the upper left) specifies isosurfaces of plume volume scattering strengths (in decibels per meter) related to particle content and temperature-density discontinuities. The vertical color bar (at the far right) gives normalized decorrelation of backscatter (0-1) due to diffuse flow from the sea floor at 0.8-sec lag. The plumes decrease in acoustic backscatter intensity as they mix with surrounding seawater with height (in meters) above vents. From Rona (2011).

The purpose of the COVIS experiment was to acoustically image, quantify, and monitor seafloor hydrothermal flow on time scales of hours (response to ocean tides) to weeks-months-years (response to volcanic and tectonic events); this advances our understanding of these interrelated processes. According to Rona and others (2003), net volume flux of a plume can be calculated by integrating the vertical flux through a plume cross-section, which can then be converted to heat and particle flux if coordinated with in-situ measurements of temperature and particle properties (concentration, size distribution, density). To achieve this, COVIS acquired acoustic data from a projector mounted on a tripod ~4 m above the seafloor at a fixed position. A computer controlled, 3- degrees-of-freedom (yaw, pitch, and roll), positioning system was used to point the sonar transducers providing a large coverage area at the site. Sonar data is collected at ranges of tens of meters from targets to make three types of measurements: 1) volume backscatter intensity from suspended particulate matter and temperature fluctuations in black smoker plumes which was used to reconstruct the size and shape of the buoyant portion of a plume; 2) Doppler phase shift which was used to obtain the flow rise velocity at various levels in a buoyant plume; 3) scintillation which was used to image the area of diffuse flow seeping from the seafloor.

References. Bemis, K.G., Rona, P.A., Jackson, D.R., Jones, C., Mitsuzawa, K., Palmer, D., Silver, D., and Gudlavalletti, R., 2001, Time-averaged images and quantifications of seafloor hydrothermal plumes from acoustic imaging data: a case study at Grotto Vent, Endeavour Segment Seafloor Observatory, Abstract OS21B-0446 presented at American Geophysical Union, Fall Meeting 2001, San Francisco, CA, December.

Bobbitt, A., 2007, NeMO 2007 Cruise Report: Axial Volcano, Endeavour Segment, and Cobb Segment, Juan de Fuca Ridge, R/V Atlantis Cruise AT 15-21, August 3-20, 2007, Astoria, Oregon, to Astoria Oregon, Jason dives J2-286 to J2-295, unpublished report (URL: http://www.pmel.noaa.gov/vents/nemo/NeMO2007-cruise-report.pdf)

Jackson, D.R., Jones, C.D., Rona, P.A., and Bemis, K.G., 2003, A method for Doppler acoustic measurement of black smoker flow fields, Geochemistry Geophysics Geosystems (G3), v. 4, no. 11, p. 1095 (DOI: 10.1029/2003GC000509, 2003).

Light, R., Miller, V., Rona, P., and Bemis, K., 2010, Acoustic Instrumentation for Imaging and Quantifying Hydrothermal Flow in the NEPTUNE Canada Regional Cabled Observatory at Main Endeavour Field (unpublished paper - URL: http://www.apl.washington.edu/projects/apl_presents/topics/covis/covis.php).

Light, R., Miller, V., Jackson, D.R., Rona, P.A., and Bemis, K.G., 2011, Cabled observatory vent imaging sonar (abstract of presentation), Journal of the Acoustical Society of America, v. 129, no. 4, p. 2373.

Merle, S. (compiler), 2006, NeMO 2006 Cruise Report, NOAA Vents Program, Axial Volcano and the Endeavour Segment, Juan de Fuca Ridge, R/V THOMPSON Cruise TN-199, August 22 - September 7, 2006. Seattle WA to Seattle WA; ROPOS dives R1008 - R1014 (URL: http://www.pmel.noaa.gov/vents/nemo2006/nemo06-crrpt-final.pdf).

NEPTUNE Canada, 2011, Transforming Ocean Science; Ocean Networks Canada. (URL: http://www.neptunecanada.ca/about-neptune-canada/neptune-canada-101/)

Rona, P.A., Bemis, K.G., Jackson, D.R., Jones, C.D., Mitsuzawa, K., Palmer, D.R., and Silver, D., 2001, Acoustic Imaging Time Series of Plume Behavior at Grotto Vent, Endeavour Observatory, Juan de Fuca Ridge, Abstract OS21B-0445 presented at American Geophysical Union, Fall Meeting 2001, San Francisco, CA, December.

Rona, P.A., Jackson, D.J., Bemis, K.G., Jones, C.D., Mitsuzawa, K., Palmer, D.R., and Silver, D., 2003, A New Dimension in Investigation of Seafloor Hydrothermal Flows, Ridge 2000 Events, v. 1, no. 1, p. 26 (URL: http://ridge2000.bio.psu.edu).

Rona, P.A., Bemis, K.G., Jones, C., Jackson, D. R., Mitsuzawa, K, and Palmer, D. R., 2010a, Partitioning Between Plume and Diffuse Flow at the Grotto Vent Cluster, Main Endeavour Vent Field, Juan de Fuca Ridge: Past and Present, Abstract OS21C-1519 presented at American Geophysical Union, Fall Meeting 2010, San Francisco, Calif., December.

Rona, P., Light, R., Miller, V., Jackson, D., Bemis, K., Jones, C., and KenneyM., 2010b, Cabled Observatory Vent Imaging Sonar (COVIS) Connected to NEPTUNE Canada Cabled Observatory (poster abstract), 2010 R2K (Ridge 2000) Community Meeting, Portland, OR, 29-31 October 2010 (URL: http://ridge2000.marine-geo.org/community-meeting/october-2010/2010-r2k-community-meeting).

Rona, P., 2011, Sonar images hydrothermal vents in seafloor observatory, EOS Transactions, American Geophysical Union, v. 92, no., 20, p. 169-170.

Rona, P.A., Benis, K.G., Jones, C.D., and Jackson, D.R., 2011, Multibeam sonar observations of hydrothermal flows at the Main Endeavour Field (abstract of presentation), Journal of the Acoustical Society of America, v. 129, no. 4, p. 2373.

Geologic Background. The Endeavour Segment (or Ridge) lies near the northern end of the Juan de Fuca Ridge, west of the coast of Washington and SW of Vancouver Island. The northern end is offset to the east with respect to the West Valley Segment, which extends north to the triple junction with the Sovanco Fracture Zone and the Nootka Fault. The 90-km-long, NNE-SSW-trending segment lies at a depth of more than 2000 m and is the site of vigorous high-temperature hydrothermal vent systems that were first discovered by scientists in 1981. Five major vent fields that include sulfide chimneys and black smoker vents, first seen from the submersible vehicle Alvin in 1984, are spaced at about 2-km intervals in a 1-km-wide axial valley at the center of the ridge. Preliminary uranium-series dates of Holocene age were obtained on basaltic lava flows, and other younger "zero-age" flows were sampled. Seismic swarms were detected in 1991 and 2005.

Information Contacts: Peter Rona, Institute of Marine and Coastal Sciences and Department of Earth and Planetary Sciences, Rutgers University, New Brunswick, NJ; NEPTUNE Canada (URL: http://www.oceannetworks.ca/).


Eyjafjallajokull (Iceland) — April 2011 Citation iconCite this Report

Eyjafjallajokull

Iceland

63.633°N, 19.633°W; summit elev. 1651 m

All times are local (unless otherwise noted)


Eruption ended in late 2010; sample of growing literature on the eruption

Gudmundsson and others (2010a) noted that the last day of sustained activity at Eyjafjallajökull took place on 22 May 2010. By 23 June 2010, the Iceland Meteorological Office (IMO) and the University of Iceland Institute of Earth Sciences (IES) ceased issuing regular status reports. In addition to discussing the eruption and its final stages, this report also cites a small sample of abstracts and papers from the numerous conferences, sessions, and publications that have thus far emerged on the eruption.

The eruption's initial phase, 20 March-12 April 2010, occurred at Fimmvörðuháls, a spot on the E flanks of Eyjafjallajökull (figure 16, and "F" and "E" on figure 17). Venting at Fimmvörðuháls took place on an exposed ridge cropping out in a region with extensive glaciers to the E and W. Eruptions began in the initially ice-capped summit crater of Eyjafjallajökull on 14 April 2010 (BGVN 35:03 and 35:04). After melting overlying portions of the icecap, the summit crater then emitted clouds of fine-grained ash that remained suspended in the atmosphere for long distances. The ash blew both over the Atlantic and for considerable intervals passed directly over Europe, halting flights of most commercial aircraft for nearly a week in a controversial shutdown with economic impacts in the billions.

Figure (see Caption) Figure 16. Index map showing Iceland, some major plate-tectonic features and generalized spreading directions, and the location of Eyjafjallajökull volcano. Note proximity of Eyjafjallajökull to Katla and to the volcanoes of the Vestmann island area (Vestmannaeyjar), Surtsey and Heimaey. Courtesy of USGS.
Figure (see Caption) Figure 17. A shaded-relief map showing Eyjafjallajökull (E), and 9 km to its E, the flank vent Fimmvörðuháls (F). Stars indicate 2010 eruptive sites (map scale at top left). Glaciers cover extensive portions of both Eyjafjallajökull and Katla volcanoes (light pattern). During 14-29 April 2010 many earthquakes struck with epicenters along the N-S axis of Eyjafjallajökull (black dots). The map includes a small slice of the Atlantic ocean along the lower left-hand margin. Two of four geodetic (GPS) stations are shown (STE2 and THEY). Revised from a map by Sigmundsson and others (2010).

In terms of satellite thermal data on the overall eruption, the MODVOLC system measured extensive (multi-pixel) daily alerts during 21 March-21 May 2010, but the alerts became absent thereafter.

Venting at Fimmvörðuháls. At a 15-19 September 2010 conference on the eruption, Höskuldsson and others (2010a) characterized the course of events during the 20 March to 12 April basaltic Fimmvörðuháls flank eruption at Eyjafjallajökull as follows: "At the beginning the eruption featured as many as 15 lava fountains with maximum height of 150 m. On March 24 only four vents were active with fountains reaching to heights of 100 m. On March 31 and April 1 the activity was characterized by relatively weak fountaining through a forcefully stirring pool of lava. The vents were surrounded by 60-80 m high ramparts and the level of lava stood at approximately 40 m. This high stand led to opening of a new fissure trending northwest from the central segment of the original fissure. As activity on the new fissure intensified, the discharge from the original fissure declined and stopped on April 7.

"The intensity of the lava fountains varied significantly on the time scale of hours and was strongly influenced the level of the lava pond in the vents, producing narrow, gas-charged, piston-like fountains during periods of low lava levels, but spray-like fountains when the lava level was high . . ..

"The eruption produced a fountain-fed lava flow field with an area of about 1.3 km2. Initially (20-25 March), the lava advanced towards northeast, but on March 26 the lava began advancing to the west and northwest, especially after April 1 when the activity became concentrated on the new fissure. The flow field morphology is dominantly 'a'a, but domains of pahoehoe and slabby pahoehoe are present, particularly in the western sector of the flow field. The advance of the lava from the vents was episodic; when the lava stood high the lava surged out of the vents, but at low stand there was a lull in the advance. The lava discharged from the vents through open channels as well as internal pathways. The open channels were the most visible part of the transport system, feeding lava to active 'a'a flow fronts and producing spectacular lava falls when cascading into deep gullies just north of the vents. The role of internal pathways was much less noticeable, yet an important contribution to the overall growth of the flow field as it fed significant surface breakouts emerging on the surface of what otherwise looked like stagnant lava. When activity stopped on April 12 the fissure had issued about 0.025 km3 of magma, giving a mean discharge of 13 m3/s."

Summit eruption. The second eruption occurred within the initially ice-covered caldera of Eyjafjallajökull. Opening of the ice cover and explosivity into the atmosphere was amplified by magma-ice interaction that produced a fine ash capable of suspension in the atmosphere for prolonged periods.

Höskuldsson and others (2010b) described the eruption at Eyjafjallajökull's summit (beginning 14 April 2010) as consisting of three phases (table 2). They also stated that at the summit the "Total amount of tephra produced in the eruption is about 0.11 km3 and that of lava 0.025 km3 DRE [dense-rock equivalent]. Average discharge rate in the eruption was about 40 m3/s DRE or about 4 times that of Fimmvörðuháls eruption."

Table 2. Three phases of the eruption at Eyjafjallajökull volcano's summit beginning 14 April 2010 as summarized and condensed by Höskuldsson and others (2010b).

Dates Phase Description of Activity
14 Apr-17 Apr 2010 I Plumes often under 6 km but up to ~9 km altitude.
18 Apr-04 May 2010 II High tremor with lava flows; generally weak and ash-poor plumes. Pulsating activity with small discrete explosions every few seconds. Tephra grains had fluidal shapes suggesting magmatic fragmentation and decreased viscosity of erupting magma. Plumes on 28th to 7 km altitude.
05 May-22 May 2010 III Plumes up to 5 km altitude.

The summit area was still steaming and geothermally active, and the eruption channel was still very hot in October 2010 (figure 18). Investigators expected that cooling to ambient temperatures would take a few years . As noted below, during June 2010, hot lava could still be seen in cracks in the cooled rock on Fimmvörðuháls, and inside craters, but that was not the case at the ice-engulfed summit caldera.

Figure (see Caption) Figure 18. The summit crater complex of Eyjafjallajökull taken after the first winter snow, as seen from the air at 0810 on 9 October 2010. The scene helps explain the high degree of water and ice interaction with the erupting lavas. Snow had melted from numerous ash and lava-covered surfaces (black areas). Although portions of the crater emitted steam, evidence of substantial ongoing lava emissions were absent at this point in time. Photo courtesy of Ólafur Sigurjónsson, IMO.

According to Gudmundsson and others (2010b) the summit eruption produced 0.1-0.2 km3 (dense rock equivalent) of tephra. IES reported that by 11 June 2010 a lake about 300 m in diameter had formed in the large summit crater, and by 23 June water was slowly accumulating in the crater because ice was no longer in contact with hot material.

Intrusion triggering. Sigmundsson and others (2010) noted that the 2010 eruptions came after 18 years of intermittent volcanic unrest. The deformation associated with the eruptions was unusual because it did not relate to pressure changes within a single source. Deformation was rapid before the flank eruption (0.5 mm per day after 4 March 2010), but negligible during it.

During the summit eruption (beginning 14 April 2010) gradual contraction of a source, distinct from the pre-eruptive inflation sources, was evident from geodetic data. Thus, clear signals of volcanic unrest may occur over years to weeks, indicating reawakening of such volcanoes, whereas immediate short-term eruption precursors may be subtle and difficult to detect.

Figure 19 shows a cross-sectional model of the shallow crust by Sigmundsson and others (2010) based deformation and seismic analyses of the 2010 event. A previous issue of the Bulletin (BGVN 35:03) contained an alternate model by Paul Einarsson.

Figure (see Caption) Figure 19. Schematic E-W cross-section across the Eyjafjallajökull summit area, with deformation sources plotted at their best-fit depth (vertical exaggeration of 2). Gray shaded background indicates source-depth uncertainties (95% confidence interval), which overlap. Courtesy of Sigmundsson and others (2010).

Processed satellite image. Vincent J. Realmuto created two composite figures generated from the MODIS-Terra satellite data acquired 15 April 2010 at 1135 UTC (figure 20). Outlined in black in each image are Iceland on the upper left side (W), Faroe Islands in the center, Scotland and N Ireland in the lower center, and part of the Scandinavian peninsula on the right side (E). An ash plume can be seen in each image extending from Iceland SW toward Europe. The left-hand image is the true-color RGB (red-green-blue) composite and the right-hand image is a false-color composite; in the right-hand rendition the ash plume appears red and the ice-rich clouds appear blue. The right-hand image puts obvious emphasis on the ash plume and shows it streaming and more or less intact for several hundreds of kilometers E of Iceland.

Figure (see Caption) Figure 20. Graphics generated from the MODIS-Terra satellite data acquired 15 April 2010 at 1135 UTC. The left-hand graphic is a true-color RGB (red-green-blue) composite, and the right-hand image is a false-color composite of Bands 32, 31, and 29 (12, 11, and 8.5 um, respectively) displayed in red, green, and blue, respectively. These data were processed with the decorrelation stretch (D-stretch), a technique for enhancing spectral contrast based on principal components analysis. In this rendition the ash plume appears red and the ice-rich clouds appear blue. The D-stretch was based on scene statistics and was intended to be a quick method for discriminating material that may be volcanic in origin. Courtesy of Vincent J. Realmuto, Jet Propulsion Laboratory, California Institute of Technology.

Conference field trip. Following The Atlantic Conference on Eyjafjallajökull and Aviation in Iceland, 15-16 September 2010 (discussed below), a field trip brought scientists to accessible areas on the volcano, including the flank vent on Fimmvörðuháls ridge where the eruption began. John and Liudmila Eichelberger provided some photographs from this trip (figure 21). The same base map appeared in BGVN 35:03, with the key and other data. The horseshoe shape of the lava distribution in this figure is the feature imaged by an ASTER satellite thermal signature as active lava flows on 19 April 2010 in BGVN 35:03.

Figure (see Caption) Figure 21. (Central panel) Map showing fissures at Fimmvörðuháls (thin red lines) and the distribution of new scoria and lava deposited at various points in time (shaded areas) during 21 March-7 April 2010. Marked arrows on the map give locations of labeled photos (A-E) taken 18 September 2010. (A) Fresh lava (darker) seen looking N. In the distance appear fresh black lava flows, some portions of which formed the lava falls down the valley walls. (B) View showing the elongate ridge as seen from the upslope perspective (people in the distance for scale). (C, looking down) Glowing lava (~1.5 m long and ~0.3 m wide) at the bottom of a fissure. This photo was taken with a flash, otherwise the fissure walls would have been very dark. (D) The fracture indicated on the map as it appeared near the rim of the ridge of newly erupted lava. (E) The same fracture seen in D from another perspective. Courtesy of John and Ludmilla Eichelberger.

More on conferences and publications. Recently, several conferences have been held and many publications have been issued relevant to the eruption. What follows is a mere sample of the available resources, many of which emphasized plume research. At the American Geophysical Union (AGU) 2010 Fall Meeting, several sessions focused on the 2010 eruption (eg., Carn and others, 2010; see References for the link to abstracts volume).

The Workshop on Ash Dispersal Forecast and Civil Aviation held in Geneva, 18-20 October 2010, addressed the characteristics and range of application of different volcanic ash transport and dispersal models (VATDM), identifying the needs of the modeling community, investigating new data acquisition strategies, and discussing how to improve communication between the volcanology community and operational agencies (eg., Bonadonna and others, 2011).

The Cities on Volcanoes conference (COV-6; Tenerife, Canary Islands, Spain, 31 May-4 June 2010) included both papers (eg. Fischer and others, 2010) and a forum on the "Assessment of volcanic ash threat: learning and considerations from the Eyjafjallajökull eruption."

In addition, several other papers relevant to the eruption were presented during this meeting, as well as at the Annual Meeting of the American Meteorological Society (AMS) in Seattle, WA, in January 2011, and at the European Geosciences Union (EGU) 2011 General Assembly in Vienna, Austria.

The journal Atmospheric Chemisrty and Physics published multiple issues with a section entitled "Atmospheric implications of the volcanic eruptions of Eyjafjallajökull, Iceland 2010." These and other papers discussed various means of plume detection, and in some cases, sampling, including on the ground, in ultralight aircraft, and on satellites; models of plume dispersion were evaluated (Flentje and others, 2010; Emeis and others, 2011; Vogel and others, 2011; Fischer and others, 2010).

According to Loughlin (2010), scientists from the British Geological Survey found large ash particles from the eruption in the United Kingdom. Most of the very small ash particles in volcanic plumes fell as clusters of particles known as aggregates. The aggregation could have resulted from a number of mechanisms, including electrostatic attraction, particle collisions, condensation of liquid films and secondary mineralization. The process of aggregation effectively removed very small particles from the plume and was therefore one variable on how long ash particles stay in the atmosphere. Ripley (2010) and Chivers (2010) published articles on the U.K. Met Office's tracking and prediction of movements of volcanic ash based on observations from the Eyjafjallajökull eruption.

Gislason and others (2011) reported on analyses of two sets of fresh, comparatively dry ash samples that fell in Iceland and were collected rapidly on 15 and 27 April, during more and less explosive phases, respectively. Both sets of samples were kept dry and analyzed swiftly to minimize issues with hydration and alteration, particularly to salts on the ash surfaces. The ash was dominantly glass of andesitic composition (57-58% SiO2). They found the ash particles especially sharp and abrasive over their entire size range, from submillimeter to tens of nanometers.

References. Bonadonna, C., Folch, A., and Loughlin, S., 2011, Future Developments in Modeling and Monitoring of Volcanic Ash Clouds, Eos, Transactions of the American Geophysical Union (AGU), v. 92, no. 10; pp. 85-86, DOI: 10.1029/2011EO100008 (URL: http://www.agu.org/pub/eos/).

Carn, S.A., Karlsdottir, S., and Prata, F., 2010, The 2010 Eruption of Eyjafjallajokull: A Landmark Event for Volcanic Cloud Hazards I, II, and III, Abstracts V41E, V53F, and V54C presented at 2010 Fall Meeting, American Geophysical Union, San Francisco, CA, 13-17 December 2010 (URL: http://www.agu.org/meetings/fm10/program/index.php).

Chivers, H., 2010, Dark Cloud: VAAC and predicting the movement of volcanic ash, Meterological Technology International, June 2010, pp. 62-65.

Emeis, S., Forkel, R., Junkermann, W., Schäfer, K., Flentje, H., Gilge, S., Fricke, W., Wiegner, M., Freudenthaler, V., Groß, S., Ries, L., Meinhardt, F., Birmili, W., Münkel, C., Obleitner, F., and Suppan, P., 2011, Measurement and simulation of the 16/17 April 2010 Eyjafjallajökull volcanic ash layer dispersion in the northern Alpine region, Atmospheric Chemistry and Physics, v. 11, pp. 2689-2701.

Fischer, C., van Haren, G., Pohl, T., Vogel, A., and Weber, K., 2010, Airborne in-situ measurements of the volcanic ash dust plume over a part of Germany caused by the volcano eruption of the Eyjafjallajökull (Iceland) by means of an optical particle counter and a light

sport aircraft, Abstract, Session 1.3, p. 229, Cities on Volcanoes 6 Conference (URL: http://www.citiesonvolcanoes6.com/ver.php).

Flentje, H., Claude, H., Elste, T., Gilge, S., Köhler, U., Plass-Dülmer, C., Steinbrecht, W., Thomas, W., Werner, A., and Fricke W., 2010, The Eyjafjallajökull eruption in April 2010 - detection of volcanic plume using in-situ measurements, ozone sondes and lidar-ceilometer profiles, Atmospheric Chemistry and Physics, v. 10, pp. 10085-10092, DOI: 10.5194.

Gasteiger, J., Groß, S., Freudenthaler, V., and Wiegner, M., 2011, Volcanic ash from Iceland over Munich: mass concentration retrieved from ground-based remote sensing measurements, Atmospheric Chemistry and Physics, v. 11, pp. 2209-2223.

Gislason, S.R., Hassenkam, T., Nedel, S., Bovet, N., Eiriksdottir, E.S., Alfredsson, H.A., Hem, C.P., Balogh, Z.I., Dideriksen, K., Oskarsson, N., Sigfusson, B., Larsen, G., and Stipp, S.L.S., 2011, Characterization of Eyjafjallajökull volcanic ash particles and a protocol for rapid risk assessment, Proceedings of the National Academy of Sciences, v. 108, no. 18, p. 7303-7312.

Gudmundsson, M. T., Pedersen, R., Vogfjörd, K., Thorbjarnardóttir, B., Jakobsdóttir, S., and Roberts, M.J., 2010a, Eruptions of Eyjafjallajökull Volcano, Iceland, Eos, Transactions of the American Geophysical Union (AGU), v. 91, no. 21, p. 190, DOI: 10.1029/2010EO210002.

Gudmundsson, M.T., Thordarson, T., Hoskuldsson, A., Larsen, G., Jónsdóttir, I., Oddsson, B., Magnusson, E., Hognadottir, T., Sverrisdottir, G., Oskarsson, N., Thorsteinsson, T., Vogfjord, K., Bjornsson, H., Pedersen, G.N., Jakobsdottir, S., Hjaltadottir, S., Roberts, M.J., Gudmundsson, G.B., Zophoniasson, S., and Hoskuldsson, F., 2010b, The Eyjafjallajökull eruption in April-May 2010; course of events, ash generation and ash dispersal, EOS, Transactions of the American Geophysical Union (AGU), V. 91, no. 21, Abstract V53F-01, 2010 Fall Meeting, AGU, San Francisco, Calif., 13-17 December (URL: http://www.agu.org/cgi-bin).

Heue, K.-P., Brenninkmeijer,C.A.M., Baker, A. K., Rauthe-Schöch, A., Walter, D., Wagner, T., Hörmann, C., Sihler, H., Dix, B., Frieß, U., Platt, U., Martinsson, B. G., van Velthoven, P.F.J., Zahn, A., and Ebinghaus, R., 2011, SO2 and BrO observation in the plume of the Eyjafjallajökull volcano 2010: CARIBIC and GOME-2 retrievals, Atmospheric Chemistry and Physics, v. 11, pp. 2973-2989.

Höskuldsson, A., Magnusson, E., Guðmundsson, M.T., Sigmundsson, F., and Sigmarsson, O., 2010a, The 20 March to 12 April basaltic Fimmvörðuháls flank eruption at Eyjafjallajökull volcano, Iceland: Course of events, abstract of presentation in Program of the Eyjafjallajökull and Aviation Conference (15-16 September 2010) and associated Eyjafjallajökull Eruption Workshop (Hotel Hvolsvellir, 17-19 September 2010); (URL: http://en.keilir.net/keilir/conferences/eyjafjallajokull/volcanological-workshop).

Höskuldsson, Á., Larsen, G., Gudmundsson, M.T., Oddsson, B., Magnússon, E., Sigmarsson, O., Óskarsson, N., Jónsdóttir, I., Sigmundsson, F., Einarsson, P., Hreinsdóttir, S., Pedersen, R., Högnadóttir, Þ., Thordarson, T., Hayward, C., Hartley, M., Meara, R., Arason, Þ., Karlsdóttir, S., and Petersen, G.N., 2010b, The Eyjafjallajökull eruption April to May 2010: Magma fragmentation, plume and tephra transport, and course of events, abstract of presentation in Program of the Eyjafjallajökull and Aviation Conference (15-16 September 2010) and associated Eyjafjallajökull Eruption Workshop (17-19 September 2010); (URL: http://en.keilir.net/keilir/conferences/eyjafjallajokull/volcanological-workshop).

Laursen, L., 2010, Iceland eruptions fuel interest in volcanic gas monitoring, Science, v. 328, no. 5977, p. 410-411.

Loughlin, S., 2010, Modelling of Iceland volcanic ash particles, news item from British Geological Survey (URL: http://www.bgs.ac.uk/research/highlights/IcelandAshParticles.html?src=sfb).

Ripley, T., 2010, Cloud Busting: How the UK is tracking the volcanic ash cloud, Meterological Technology International, June 2010, pp. 6-10.

Schumann, U., Weinzierl, B., Reitebuch, O., Schlager, H., Minikin, A., Forster, C., Baumann, R., Sailer, T., Graf, K., Mannstein, H., Voigt, C., Rahm, S., Simmet, R., Scheibe, M., Lichtenstern, M., Stock, P., Rüba, H., Schäuble, D., Tafferner, A., Rautenhaus, M., Gerz, T., Ziereis, H., Krautstrunk, M., Mallaun, C., Gayet, J.-F., Lieke, K., Kandler, K., Ebert, M., Weinbruch, S., Stohl, A., Gasteiger, J., Groß, S., Freudenthaler, V., Wiegner, M., Ansmann, A., Tesche, M., Olafsson, H., and Sturm, K., 2011, Airborne observations of the Eyjafjalla volcano ash cloud over Europe during air space closure in April and May 2010, Atmospheric Chemistry and Physics, v. 11, pp. 2245-2279.

Sigmundsson, F., Hreinsdóttir, S., Hooper, A., Árnadóttir, T., Pedersen, R., Roberts, M.J., Óskarsson, N., Auriac, A., Decriem, J., Einarsson, P., Geirsson, H., Hensch, M., Ófeigsson, B.G., Sturkell, E., Sveinbjörnsson, H., and Feigl, K.L., 2010, Letter: Intrusion triggering of the 2010 Eyjafjallajökull explosive eruption, Nature, v. 468, pp. 426-430.

Stohl, A., Prata, A.J., Eckhardt, S., Clarisse, L., Durant, A., Henne, S., Kristiansen, N.I., Minikin, A., Schumann, U., Seibert, P., Stebel, K., Thomas, H.E., Thorsteinsson, T., Tørseth, K., and Weinzierl, B., 2011, Determination of time- and height-resolved volcanic ash emissions and their use for quantitative ash dispersion modeling: the 2010 Eyjafjallajökull eruption, Atmospheric Chemistry and Physics, v. 11, pp. 4333-4351.

Vogel, A., Weber, K., Fischer, C., van Haren, G., Pohl, T., Grobety, B., and Meier, M., 2011, Airborne in-situ measurements of the Eyjafjallojökull ash plume with a small aircraft and optical particle spectrometers over north-western Germany - comparison between the aircraft measurements and the VAAC-model calculations, European Geophysical Union General Assembly, Geophysical Research Abstracts, v. 13, p. EGU2011-13253.

Geologic Background. Eyjafjallajökull (also known as Eyjafjöll) is located west of Katla volcano. It consists of an elongated ice-covered stratovolcano with a 2.5-km-wide summit caldera. Fissure-fed lava flows occur on both the E and W flanks, but are more prominent on the western side. Although the volcano has erupted during historical time, it has been less active than other volcanoes of Iceland's eastern volcanic zone, and relatively few Holocene lava flows are known. An intrusion beneath the S flank from July-December 1999 was accompanied by increased seismic activity. The last historical activity prior to an eruption in 2010 produced intermediate-to-silicic tephra from the central caldera during December 1821 to January 1823.

Information Contacts: Institute of Earth Sciences (IES), University of Iceland, Sturlugata 7, Askja , 101 Reykjavík (URL: http://www.earthice.hi.is/); Icelandic Meteorological Office (IMO) (URL: http://en.vedur.is/earthquakes-and-volcanism/articles/nr/1884); U.K. Meteorological Office (URL: http://www.metoffice.gov.uk); ármann Höskuldsson, Institute of Earth Sciences (IES), University of Iceland, Sturlugata 7, Askja , 101 Reykjavík (URL: http://www.earthice.hi.is); 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/); Sue C. Loughlin, The British Geological Survey, Murchison House, West Mains Road, Edinburgh EH9 3LA, Scotland, UK (URL: http://www.bgs.ac.uk/); Vincent J. Realmuto, Jet Propulsion Laboratory, California Institute of Technology, M/S 183-501, 4800 Oak Grove Drive, Pasadena, CA 91109 USA; John Eichelberger, U.S. Geological Survey, Volcano Hazards Program, Reston, VA (URL: http://volcanoes.usgs.gov/); Ludmilla Eichelberger, Global Volcanism Program, National Museum of Natural History, 10th and Constitution Ave., NW, Washington, DC 20560 USA; Iceland Review (URL: http://icelandreview.com/icelandreview/daily_news/).


Irazu (Costa Rica) — April 2011 Citation iconCite this Report

Irazu

Costa Rica

9.979°N, 83.852°W; summit elev. 3432 m

All times are local (unless otherwise noted)


Crater lake dries and regional acid-rain report

In April 2010 the lake within Irazú's crater dwindled to only a few centimeters depth and from May to August the lake was dry enough to allow plants to grow up to 10 cm high. Water began to accumulate in September 2010 but disappeared again during the following month. Since November 2010 water returned to the crater and as late as April 2011, a shallow turquoise-blue lake was maintained. Continuous monitoring of acid rain on Irazú's flanks reflected contributions from Turrialba. Often called Irazú's "twin volcano," Turrialba is less than 10 km to the ENE and during the past 4 years it has caused a region-wide increase in acid rain. Covering January 2004 through September 2007, the last Bulletin report on Irazú (BGVN 32:11) highlighted decreasing lake levels, fumarolic changes, and minor mass wasting on the crater walls during January 2004 to March 2007 (see table 8 for a summary of lake changes).

Table 8. Changing lake conditions based on observations of Irazú's crater. Double asterisks indicate times when the lake disappeared; "--" fills cells where no data is available; lake levels are reported qualitatively except for the 7 October to 12 March 2010 time interval when absolute values were measured. This summary is based on ICE data and OVSICORI Monthly Reports.

Date Lake level Temp. °C Water color Notes
** Apr 1990 Empty -- -- --
1991-1994 Stable -- green Infrequent Bubbles
08 Dec 1994 ~VEI 2 explosion from the NW outer flank fumarole~ -- -- --
1994-1996 Stable -- green Bubbles
May 2000 Decreasing 18 yellow-green Bubbles
Jan 2001 ~30 -- green Bubbles
08 Feb 2003 Stable 15 reddish Rockslide into lake
Jan-Dec 2004 Stable -- green Convection cells at edges
Jan-Nov 2005 Stable -- green Convection cells in center
Mar-Dec 2006 Stable -- increasingly yellow-green Convection cells in various locations
Mar-Sep 2007 Decreasing 145 light-green Convection cells at edges and center; bubbles
20 Sep 2007-Mar 2008 Decreasing 17 -- Bubbles
05 Mar 2008-07 Oct 2009 Decreasing 14 dark green Bubbles
07 Oct 2009-12 Mar 2010 1.4 m 16 dark-to-light green --
Apr 2010 Only few cm -- -- --
** May-Aug 2010 Empty -- -- Plants on crater floor
Sep 2010 Re-forming -- -- --
** Oct 2010 Empty -- -- --
Nov 2010-Jan 2011 Forming -- turquoise --
Feb-Apr 2011 Few meters -- turquoise-to-blue --

On 22 July 2010 a team of investigators from Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA) descended to the dry crater floor. They documented changes in vegetation, fumaroles, and clay deposition on the crater floor. Photos taken during prior trips provided comparisons with previous conditions (figure 14). Rockfalls and minor mass wasting had been occurring regularly and the long runout of debris across the crater floor was visible during this investigation. Most of the debris fell from the E and SW walls. On the NE side of the dry crater a rocky area emitted low temperature (24°C) sulfur-smelling gases from three aligned vents. Higher temperatures (86°C) were measured from fumaroles on the N side of the crater but they appeared to be releasing gas with less energy than observed in the past years when bubbles were visible within the lake. Another interesting finding was a waterfall on the inside of the crater on the SW wall; this small waterfall did not have sufficient volume to pool on the crater floor and instead soaked directly into the surrounding clay.

Figure (see Caption) Figure 14. Views taken from Irazú's S rim. (top) The crater on 24 April 2004 contained a turquoise lake. (bottom) A repeat photo taken on 22 July 2010 shows the lake had disappeared; the former lake level and the clay base on the crater floor are marked. Since November 2010 water had accumulated and as of April 2011, was several meters deep. Courtesy of Eliecer Duarte, OVSICORI-UNA.

The water level in Irazú's crater has been variable throughout time; the Bulletin recorded a dry crater during February 1977 and June 1987 (SEAN 12:07), and April 1990 (BGVN 15:04). Factors highlighted during the IAVCEI CVL-7 ("Commission of Volcanic Lakes" Costa Rica, 10-19 March 2010) included complex connections with Turrialba, seasonal effects, infiltration within the crater, and the role of mass wasting. The mechanism for the recent disappearance of the lake is still under investigation by OVSICORI-UNA and ICE investigators (Guillermo Alvarado, personal communication).

Erosion. Mass wasting had been an ongoing process for at least 10 years. Material is primarily shed from the E and SW walls and the lake contained islands of black and red material formed from the debris. In February 2003 a major rockslide into the lake caused the water color to change from green to shades of red. An analysis of seismicity during that month showed no correlation to these slope failures (BGVN 28:12). Cracks along the NW rim formed and widened since December 2007; these cracks caused blocks up to 3 x 20 m to fall from the rim in March 2008.

Local gas measurements. Since the large phreatic explosion in December 1994 (BGVN 19:12), the NW fumarole has been releasing low gas emissions regularly. Different temperature measurements recorded since June 2010 ranged between 90°C to 86°C. To monitor changes in sulfur dioxide output from Irazú, a network of three stations collected rain samples from sites along the volcano's flanks.

The pH data from September 2004 through July 2010 were plotted in the OVSICORI-UNA July 2010 monthly report. The results correlate pH changes to much larger degassing events occurring at Turrialba, a neighboring volcano that began major degassing in 2007. Only the "Borde Sur" station was sampling continuously but the other two stations reflected similar trends in acidity. Despite irregular fluctuations, a decreasing pH trend began in 2007. The lowest point of the trend was measured by "Borde Este" at approximately pH 3.25. Where there "Pacayas" station data began, the trend appeared to have stabilized between pH 3.25 and 4.75.

References. D. Rouwet, R.A. Mora-Amador, C.J. Ramírez-Umaña, G. González, Seepage of "aggressive" fluids reduce volcano flank stability: the Irazú and Turrialba case, Costa Rica, Abstract, CVL 7 Workshop Costa Rica, IAVCEI-Commission of Volcanic Lakes, March 2010.

Geologic Background. Irazú, one of Costa Rica's most active volcanoes, rises immediately E of the capital city of San José. The massive volcano covers an area of 500 km2 and is vegetated to within a few hundred meters of its broad flat-topped summit crater complex. At least 10 satellitic cones are located on its S flank. No lava flows have been identified since the eruption of the massive Cervantes lava flows from S-flank vents about 14,000 years ago, and all known Holocene eruptions have been explosive. The focus of eruptions at the summit crater complex has migrated to the W towards the historically active crater, which contains a small lake of variable size and color. Although eruptions may have occurred around the time of the Spanish conquest, the first well-documented historical eruption occurred in 1723, and frequent explosive eruptions have occurred since. Ashfall from the last major eruption during 1963-65 caused significant disruption to San José and surrounding areas.

Information Contacts: E. Duarte, Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); G. Alvarado and G.J. Soto, Oficina de Sismologia y Vulcanologia del Arenal y Miravalles (OSIVAM), Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San Jose, Costa Rica.


Machin (Colombia) — April 2011 Citation iconCite this Report

Machin

Colombia

4.487°N, 75.389°W; summit elev. 2749 m

All times are local (unless otherwise noted)


Seismic and non-eruptive unrest detected in 2004, 2008, 2009, and again in 2010

This is the first Bulletin report on Cerro Machín volcano, the site of seismic unrest for many years, most recently, 1992, 1999, 2002, 2004, 2008, 2009, and 2010. This activity did not lead to eruptions. Instrumental monitoring by INGEOMINAS began in 1987 and has determined Machín's background seismicity ranged from 1 to10 earthquakes/day, but during intervals of unrest, seismicity sometimes reached several hundred earthquakes per day.

This is a small but explosive volcano located at the S end of the Ruiz-Tolima massif, 185 km NNE of the Nevado del Huila volcano and 147 km WSW of Bogotá, the capital (figure 1). (Tolima volcano, not shown, lies ~22 km NNE of Machín.)

Figure (see Caption) Figure 1. Map of Colombia showing the location of the Machín volcano. Note the Departments (states) of Tolima (1) and Huila (2) are shaded regions. Courtesy of the IFRC and Relief Web.

Machín caldera contains three dacitic domes; the 3-km-wide caldera is breached to the S. According to Mendez and others (2002), there have been six eruptions within the past 10,000 years. In the same report, the authors noted geomorphological similarities between Machín and Pinatubo prior to its large 1991 eruption. The seismic events have drawn increased attention to Machín from the Volcanic and Seismological Observatory of Manizales, Colombia Institute of Geology and Mining (INGEOMINAS).

According to news articles published in mid-May 2004, INGEOMINAS reported that there had been an increase in seismicity at Machín in April. About 60 earthquakes were recorded daily (in comparison to the 1-10 earthquakes normally recorded); however, no surface changes were seen at that time at the volcano.

There was no further significant seismic activity until the first week of January 2008 when INGEOMINAS reported unusual seismicity at Machín during 6-8 January. Long-period earthquakes were detected S of the main lava dome. On 7 January, the volcano-tectonic seismic signals were occasionally felt and reported by nearby residents. The simultaneous occurrence of both types of seismic signals was unusual for Machín. Again, the activity diminished to the previous background levels until 9 November when INGEOMINAS reported a cluster of ~375 earthquakes, the majority of which were located towards the E sector and below the dome of the volcano with depths between 2.5 and 5 km. The earthquake activity occurred underneath the central and E parts of the lava dome complex in the summit caldera and fumarolic activity in the area increased. During 8-10 November 2008, Machín registered 1,210 volcano-tectonic earthquakes, 9 of which were M 2.5. According to news articles, approximately 400-450 people evacuated to shelters or other safe areas. There were also reports of landslides that blocked a highway.

Table 1 and figure 2 detail the local villages in proximity to Machín.

Table 1. Villages in proximity to Machín and the respective distances from the caldera (approximate). Taken from web sources such as Google Earth.

Village/town Crater distance (km) Direction
El Rodeo 96 NNW
Santa Marte 15 NNE
Aguacaliente 23 SSW
Toche 62 NW
Cajamarca 8 SSW
Ibague 17 ESE
Salento 24 NW
Circasia 31 WNW
Calarca 30 W
Figure (see Caption) Figure 2. A regional map showing population centers and paved and unpaved roads. Courtesy of INGEOMINAS.

On 10 November the seismic activity of the volcano diminished to background conditions. On 17 December INGEOMINAS reported that a swarm of 98 earthquakes occurred at Machín SE of the lava domes at depths of 2-6 km. The largest earthquake was M 2.6 at a depth of ~4 km.

There were two significant seismic events at Machín during 2009. On 31 July there was in increase in seismic activity, which consisted of ~200 events. Initially the increase was gradual, however, during the last hour the activity increased abruptly and included an earthquake of M 2.7. This subsided to a background level until early December when INGEOMINAS detected 54 earthquakes, some M ~ 1.3. Authorities issued a "Yellow" alert (Yellow; "changes in the behavior of volcanic activity") for Machín. The Tolima Regional Emergency Committee conducted evacuation training with local communities as a precaution.

INGEOMINAS reported that on 24 July 2010 a seismic crisis at Machín was characterized by volcano-tectonic earthquakes. An M 2.6 earthquake was located S of the main lava dome at a depth of ~4 km. The next day an M 4.1 volcano-tectonic earthquake occurred 0.8 km S of the main dome at a depth of ~3.9 km. The Yellow alert remained in effect following the increase in registered seismic activity in the area. On 29 July the number of volcano-tectonic events again increased; the earthquakes were a maximum M 1.7 and between 3 and 4 km depth, S of the main dome.

On 17 September 2010, INGEOMINAS again reported increased seismicity. About 140 volcano-tectonic earthquakes as large as M 1.85 were located S and SW of the main lava dome at depths of 2-4 km. On 4 October there was an M 3.5 tectonic earthquake located 0.37 km S of the main dome at a depth of ~4.14 km. Residents near the volcano felt this earthquake. The Alert Level remained at Yellow.

On 3 December 2010 about 340 volcano-tectonic earthquakes with low magnitudes were located SW of the main lava dome, at an average depth of 4 km. The largest event, a M 3.7 earthquake located SW of the dome at a depth of about 3.5 km, was felt by local residents. On 31 December INGEOMINAS reported a period of increased seismicity. A total of 346 volcano-tectonic events no stronger than M 2.1 were located S and SW of the main lava dome.

On 1 January 2011 seismicity again increased, and at the time of the report, 367 events had been detected. The low-magnitude events were located S and SW of the main dome at depths between 2.5 and 4.5 km. The largest event, M 2.3, was located S of the dome at a depth of about 3.3 km and felt by residents near the volcano and in the municipality of Cajamarca, 8 km SSW. On 13 January an increased number of earthquakes were located to the W and SW of the main dome at depth of 2.5-3.5 km. The largest event registered M ~2.6 and was reported to have been felt by residents near the volcano.

Since 1989, INGEOMINAS noted a gradual increase in seismicity has been following the events closely in order to report any changes on the volcano's activities (figure 3). All the local emergency committees were activated in the area near Machín volcano in addition to the regional emergency committees in Tolima District.

Figure (see Caption) Figure 3. Map showing potential hazards from hypothetical future activity at Machín. Thicknesses of potential ash fall to the W are shown (in cm) as modeled by computer-aided dispersion modeling (VAFTAD); PF stands for pyroclastic flow deposits. Adaped from INGEOMINAS (2007).

References. Méndez, RA; Cortés, GP; and Cepeda, H; [Calvache, ML, Project Chief], 2002, Evaluacíon de la Amenaza Volcánica Potencial del Cerro Machín (Departamento del Tolima, Colombia), Manizales, Sept. 2002, INGEOMINAS, 66 p. (in Spanish).

Méndez, RA, Cortés, GP, and Cepeda, H., 2007, Evaluacíon amenazas potencial de volcan Cerro Machín [Large map in Spanish taken from 2002 report of same name. Name in English, 'Evaluation of potenial hazards from volcan Cerro Machín'] Mapa Amenaza Volcán Machín, INGEOMINAS (URL: http://intranet.ingeominas.gov.co/manizales/images/5/55/MAPA_AMENAZA_VOLCAN_MACHIN.jpg)

Geologic Background. The small Cerro Machín stratovolcano lies at the southern end of the Ruiz-Tolima massif about 20 km WNW of the city of Ibagué. A 3-km-wide caldera is breached to the south and contains three forested dacitic lava domes. Voluminous pyroclastic flows traveled up to 40 km away during eruptions in the mid-to-late Holocene, perhaps associated with formation of the caldera. Late-Holocene eruptions produced dacitic block-and-ash flows that traveled through the breach in the caldera rim to the west and south. The latest known eruption of took place about 800 years ago.

Information Contacts: Instituto Colombiano de Geologia y Mineria (INGEOMINAS), Observatorio Vulcanológico y Sismológico de Manizales, Manizales, Colombia; Relief Web (URL: https://reliefweb.int/); International Federation of Red Cross And Red Crescent Societies (IFRC) (URL: http://www.ifrc.org/); Caracol Radio; El Tiempo:Portafolio (URL: http://columbiareports.com).


Poas (Costa Rica) — April 2011 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Photos of phreatic eruptions from acid lake; surrounding vegetation damaged by gases

Occasional, typically minor phreatic eruptions occurred at Poás through at least early February 2011 (BGVN 35:12). They emerged from the active crater lake, Lago Caliente. The Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) illuminated intervals of phreatic eruptions and relations on the chemistry of Lago Caliente's waters over a period of more than 30 years (figure 94). This report includes photos of phreatic eruptions in 2009, 2010, and early 2011, and reviews events through March 2011.

Figure (see Caption) Figure 94. Plots of the sulfur, chlorine, and fluorine concentrations, as well as the temperature, pH, and gas volumes in the Lago Caliente waters at Poás, with respect to time. The data on the time axis extends from early 1978 to late 2009. Arrows along the top indicate periods with frequent phreatic eruptions. Notice the low pH, often well below pH 1.5. Courtesy of OVSICORI-UNA.

Volcanic gases and associated condensate and rainfall led to increasing areal extent and degree of damage to vegetation in nearby areas. In studying the Lago Caliente's waters, Martinez and others (2011) found in solution a variety of oxo-anions of sulfur called polythionates (SnO6-2, where n can be 20 or larger), which they found to vary in concentration from undetectable to 8,000 mg/L. They considered polythionates to be "highly relevant for monitoring purposes at Poás, in particular because they may signal impending phreatic eruptions."

More on the 25 December 2009 phreatic eruption. A previous report (BGVN 35:12) discussed a phreatic eruption on 25 December 2009 but some further comments are worth adding. As previously noted (BGVN 35:12), "Steam and lake water mixed with sediment and blocks were ejected 550-600 m above Laguna Caliente and fell in the vicinity of the lake, within the crater." No mention was previously made of a 24 December 2009 phreatic eruption discussed by OVSICORI-UNA. It took place in the morning at 0808 and all erupted material fell back in the crater.

Photos taken on 25 December 2009 and recently posted on the Picasa website have come to our attention. The four photos on figure 95 come from a set of nine taken from the S rim. The earliest of the set depict a very tranquil lake with steaming at or near the dome (not shown here). The next photo, taken 129 seconds after that tranquil scene, portrays the advancing eruption (figure 95a). The subsequent two photos (figure 95b and c) captured the interval closest to the peak of the eruptive vigor.

Figure (see Caption) Figure 95. Four sequential photos taken looking N at Poás of a phreatic eruption from the center of Lago Caliente on 25 December 2009. The time intervals between the four photos was as follows: photos (a) to (b), 5 sec; photos (b) to (c), 5 sec; and photos (c) to (d), 11 sec. Photo descriptions below: (a) The earliest available photo of the eruption cloud, which, based on the next photo in this set, was clearly still emerging energetically. It advanced with the leading portions of the plume chiefly dark. At the plume's base, white steam clouds mask the lake. (b and c) The shots taken closest to the maximum point of the eruption's thrust phase, with dark material still conspicuous. White tufts expanded and began to cap most of the advancing jets. The clouds engulfing the base of the plume now contain more discolored zones. (d) As the plume evolves and the vigorous exhalative part of the eruption ends or wanes, a steam-rich cloud envelops the eruption cloud. Note the gray-colored rain falling out of the plume. Taken from Cindy and JM's Gallery (undated) on the Picasa photo sharing website (see References and Information Contacts below).

An exact assessment of the photos is complicated by several factors. There were shifts in the focal length of the lens (documented in camera metadata found on the website). Also, in detail, the camera's time record indicated 0252 hrs, clearly incorrect for this daylight scene. That problem is reconciled by a photo featured in the OVSICORI-UNA report, which showed a plume photo by another photographer at a stage nearly identical to figure 95b and the text indicated the eruption occurred at 0952 hrs local time.

An email response from Cindy Doire provided these comments about witnessing the phreatic eruption.

"We arrived at the volcano early in the morning. We were one of the first to arrive that day. Our group and a few other tourists were looking at it and NOTHING was happening. The people finished looking and started leaving that spot. It was just about 4 of us still there, when suddenly the volcano started to erupt. There was NO warning at all. Even the rangers were surprised. At the beginning, white steam (gas?) shot up, then black rock and dirt started exploding out. I believe that everything that shot up, fell back into the crater . . . the gas could be smelled and was strong . . .."

In an email to GVP regarding the 25 December 2009 eruption, Eliecer Duarte commented: "It seems that this [25 December 2009] eruption opened a more permanent vent at the bottom of the lake. Since that event the frequency of phreatic ones increased and remained like this for [a] year and a half. We still have dozens of smaller ones daily.

More on crater degassing. Field visits during 2010 and 2011 allowed scientists to see the expanding effects of Poás volcanic gases on vegetation (figures 96 and 97). Dry conditions resulted in winds carrying the gases considerable distances from the volcano. The area most affected was an elongate zone downwind of the active crater and extending ~4 km SW. Figure 97 portrays transitional zones with intermediate effects.

Figure (see Caption) Figure 96. A commercial airline pilot and amateur photographer took this and other photos of Poás on 28 April 2010. The active crater and its discolored lake (Lago Caliente) reside at the right-hand side of this shot. It is part of an elongate zone of barren rock stretching ~4 km across the otherwise lushly vegetated landscape. As is typical, the plume's orientation on this day lies directly over the barren zone. From "Len" (undated), (see Reference below).
Figure (see Caption) Figure 97. Oblique view highlighting the area to the S of Poás (note volcano's crater lakes, including the active "Lago Caliente") On color versions of this figure, the pink rhombuses show sites for collecting acid rain. Providencia is shown in the lower left. The crater lake at upper right, "Botos" is ~0.5 km across in the long direction but the scale on this image varies with distance towards the foreground. Courtesy E. Duarte, OVSICORI-UNA.

Starting just beyond the elongate zone of harsh effects, the areas of discolored vegetation had increased impact and areal extent. One such impacted area was a nature preserve called Providencia, which is seen in figure 97 to the left of Poás. Farther from the volcano lies Cerro Pelón (2.5 km distance and direction SW of the crater) , which also showed the effects of chemical burning from volcanic gases (figure 97).

In the past, activity centers have migrated within the crater. OVSICORI-UNA reported that, for at least the past year (ending March 2011), the points of degassing have been concentrated in the hot crater lake and dome (figure 98). The emanating steam and gases, often carried by wind, have affected areas up to several hundred meters around the crater (figures 96-98).

Figure (see Caption) Figure 98. The active crater at Poás, showing pronounced steam release both from fractures in the dome as well as from the lake's surface. Conditions like this (with more or less steam) often prevailed in recent times (including just a few seconds prior to the eruption sequence shown in figure 95). The crater lake (Lago Caliente) rests behind (N of) the dome and steam clouds. Courtesy E. Duarte, OVSICORI-UNA.

OVSICORI-UNA reported that through at least March 2011 small phreatic eruptions occurred daily at Lago Caliente. These eruptions sometimes only reached the lake's surface, but at other times reached a few meters above the lake, and occasionally, tens of meters above the lake. The majority of the erupted sediments fell back into the lake. The fine sediments sometimes remained suspended in the lake water and caused its gray color. The majority of eruptions occurred in the central part of the crater, with a few originating slightly more to the N or S of the center. Because of the phreatic activity and high temperature of the lake (57°C), strong evaporation occurred and plumes traveled long distances in the wind (figure 99).

Figure (see Caption) Figure 99. At Poás, a phreatic eruption at Lago Caliente reaching several meters high, in a manner typical of daily activity during recent months. View from the active crater's N side (opposite the viewpoint). Photo taken sometime in January 2011. Courtesy E. Duarte, OVSICORI-UNA.

A comparison of vegetation in the area between Cerro Pelón and Providencia (designated "F1" in figure 97) made during August 2010 to January 2011 found that most plant species were resistant at certain levels of acidification. However, when their tolerance thresholds were reached, the affected species decayed quickly and were sometimes unable to recover. Certain species, including eucalyptus, pine, alder, and cypress, were particularly sensitive to the volcanic gases. Minor effects from gases were observed on Cypress trees as far as 9 km SW of the emission source. OVSICORI-UNA reports contained several photos showing more details on the effects of acidic gases on vegetation. One of their later reports, from April 2011, discussed ongoing phreatic eruptions and dome temperature of 560°C.

References. Cindy and JM's Gallery, undated, "Poas volcano eruption, December 25th, 2009" [9 photos] Picassa (URL: https://picasaweb.google.com/cjmdoire); [includes camera-related metadata].

Len (Barfbag), undated, "Wednesday, April 28, 2010, Mt Poas, Costa Rica" ; in Viewsfrom the left seat, A look at the airline world ... ride along in the cockpit (URL: http://viewsfromtheleftseat.blogspot.com/2010/04/mt-poas-costa-rica.html)

Martínez, M., van Bergen, M.J., Fernández, E., and Takano, B., 2011, Polythionates monitoring at the acid crater lake of Poás Volcano, IAVCEI-COMMISSION OF VOLCANIC LAKES, CVL7 Workshop, Costa Rica, 10-19 March 2010, Online Abstracts volume (May 2011), p. 12 (URL: http://www.ulb.ac.be/sciences/cvl/)

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: E. Duarte and E. Fernández, Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/); Cindy Doire (address withheld by request).


Ranau (Indonesia) — April 2011 Citation iconCite this Report

Ranau

Indonesia

4.871°S, 103.925°E; summit elev. 1854 m

All times are local (unless otherwise noted)


Fish kill in April 2011 strikes hot-spring areas of intra-caldera lake

This report on Ranau, a Pleistocene caldera that lies along the Great Sumatran fault, is based on accounts of fish kills, including one on 4 April 2011. The fish died near hot springs in Lake Ranau, a large caldera lake, and their deaths were attributed to seismically induced H2S releases by the Center of Volcanology and Geological Hazard Mitigation (CVGHM). CVGHM reported the surface area of Lake Ranau to be ~127 km2, and noted that the Lake Ranau complex is geothermally active, with hot springs that emerge at the foot of Mount Seminung on the banks of Lake Ranau. In addition to the 2011 event, fish kills have been recorded in Lake Ranau (figure 1) for the past five decades (table 1).

Figure (see Caption) Figure 1. Photo of Lake Ranau with Mount Seminung in the background. Posted by blogger "masternewstoday" in May 2011.

Table 1. Previous fish kills in Lake Ranau reported during the past five decades. (Note that there is no mention of any correlation between seismicity and geochemical anomalies.) Courtesy of CVGHM.

Year Description
1962  Residents in Sende Simpang Village noted that the lake water became milky white in color and all of the fish died.
1993 One or more fish kills over 3 months.
1995 Small-scale fish kill accompanied by a rotten smell (presumably H2S).
1998 Large-scale fish kill occurred. According to the head of the village, the event began with turbulent water in Lake Ranau that lasted for approximately 30 minutes.

Reports stated that the 4 April 2011 fish kill was large in scale. According to the head of a nearby village, Sugih Sane, the event began with turbulent water in Lake Ranau that lasted for approximately 30 minutes. Local residents reported that the fish kill occurred during a relatively short time in portions of the lake surrounding hot springs. At the time of the incident, the water in the affected areas appeared milky white, and wind spread the smell of sulfur to surrounding areas.

Geochemistry. Scientists conducted field work near the three hot springs Kota Batu, Ujung, and Way Wahid during 16-19 April 2011. At that time they reported the following: No dead algae were found on the lake's surface. There was no smell of sulfur, the water was clear, and the water around the hot springs was bubbling and warm. * Dead fish were no longer present. The pH of the lake water was 7.74, and the temperature was 26.1°C. The water near the hot springs had a pH of 6.32-7.06, with a temperature of 47.8-62°C. The water of the river that empties into Lake Ranau (input) had a pH of 8.07-8.10, and the lake water discharge (output) had a pH of 7.86. The result of ambient gas examination showed no gases associated with magmatic gases, such as CH4, CO2, CO, and H2S, in the vicinity of the hot springs discharge. The degree to which the above measurements were anomalous was unstated.

Seismicity. Seismic data recorded during 16-20 April 2011 showed microearthquake activity around Lake Ranau. The earthquakes were located along a fault line oriented in the SE-NW direction along Lake Ranau, at depths of 0.6 and 10 km below the surface of the lake. The Berkelulusan location coincides with the location of the Kota Batu hot springs. Prior to the fish kill at Lake Ranau on 4 April, an M 5.1 earthquake was recorded on 29 March 2011 in Bengkulu, ~160 km W of Lake Ranau.

Cause of the fish kill. CVGHM concluded that, based on the results of the field work (location of dead fish near hot springs, sulfur smell carried by wind up to 3 km away, absence of dead algae, and changing color of the lake water to milky white during the event), the fish kill in Lake Ranau was caused by the release of H2S gas into the lake water, which caused imbalances in lake water chemistry. They said that hydrothermal gas was trapped over time and escaped to the surface after the pressure due to tectonic disturbances. CVGHM concluded that the M 5.1 earthquake in Bengkulu on 29 March 2011 led to increased pressure on the fault in the vicinity of Lake Ranau; then, H2S gas was released to the surface in the vicinity of the hot springs. According to CVGHM, the occurrence of microearthquakes is a result of the fault in the vicinity of Lake Ranau, and are neither dangerous nor destructive. However, CVGHM asked residents to report future fish kills to the local government.

Geologic Background. Ranau is an 8 x 13 km Pleistocene caldera partially filled by the crescent-shaped Lake Ranau. The caldera lies along the Great Sumatran Fault that extends the length of Sumatra. Incremental formation of the caldera culminated in the eruption of the voluminous Ranau Tuff about 0.55 million years ago. A morphologically young post-caldera stratovolcano, Gunung Semuning, was constructed within the SE side of the caldera to a height of more than 1,200 m above the lake surface. The volcano has not been mapped in sufficient detail to determine the age of its latest eruptions, although fish kills and sulfur smells in the late 19th and early 20th centuries may be related to volcanism.

Information Contacts: Center of Volcanology and Geological Hazard Mitigation (CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://vsi.esdm.go.id/); Masternewstoday (URL: http://hot-breaking-news-masternewstoday.blogspot.com).


Rincon de la Vieja (Costa Rica) — April 2011 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

10.83°N, 85.324°W; summit elev. 1916 m

All times are local (unless otherwise noted)


Fumarolically active but non-eruptive through January 2011

Low-frequency earthquakes and tremor were reported at Rincón de la Vieja during the first half of 2008 (BGVN 33:07). Since then, Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA) had issued intermittent reports of activity through January 2011. Those reports are summarized in the following sections, with much of the discussion centered around fumaroles and behavior of the geothermally warmed lake in the active crater. Occasional, typically small phreatic eruptions had occurred here in past years, for example in the 1990s (eg., BGVN 21:02, 21:03, 22:01, and 23:03) but were absent in the current reporting interval (last half of 2008 through January 2011).

August 2008. OVSICORI-UNA reported that the level of the lake was at a high level, with a bluish color, generated convection cells with evaporation, and had sulfur particles visible on it's surface. Sulfur deposition and fumarolic activity continued along the SW wall.

March 2009. In mid-March 2009, scientists visited the S and SW flank, collected samples, and noted some temperatures of 75-78°C. Because the visit occurred during the dry season, most areas encountered were dry. The scientists examined an area of acidification to the W of Von Seebach crater, ~3 km SW of the active crater. Strong winds common in that direction sometimes carried volcanic gases. Consequently, most of this narrow expanse only contained patches of grassland and shrubs that barely covered the rocky surface.

October 2009. OVSICORI-UNA reported that seismographic station RIN3, located ~5 km SW of the main crater, registered volcano-tectonic events and tremor lasting for minutes.

Weak ongoing fumarolic activity during 2010 through January 2011. OVSICORI-UNA reported that the level of the crater lake remained high during 2010, with constant evaporation. Geochemical, seismic, and deformation data did not show significant changes in physico-chemical parameters during 2010. The changing color of the lake, from blue to gray, was attributed to intense rains and fumarolic activity in the crater.

Later reporting. Reports during 2010 through at least January 2011 described fumarolic activity along the S and SW walls of the crater, with sulfur deposition and moderate gas discharge. The lake remained a gray color, with sulfur particles in suspension. Figure 15 shows a photo taken in April of the crater looking at the SW wall with fumarolic activity along with sulfur deposition. In April 2010, OVSICORI-UNA reported that the temperature of the lake was 49°C. A fumarole sometimes seen active along the N flank had stopped discharging gas.

Figure (see Caption) Figure 15. Photo of the active crater lake of Rincón de la Vieja on 29 April 2010 showing yellow sulfur deposits and fumarolic activity along the SW wall of the crater. This kind of activity was typical throughout the reporting interval (last half of 2008 through January 2011). Photo by E. Fernandez, OVSICORI-UNA.

OVSICORI-UNA reported that 2010 was unusual in that four domestic volcanoes were active: Arenal, Poás, Turrialba, and Rincón de la Vieja. Irazú was comparatively inactive (see separate report in this issue of the Bulletin).

Geologic Background. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Sometimes known as the "Colossus of Guanacaste," it has an estimated volume of 130 km3 and contains at least nine major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 km3 Río Blanca tephra about 3500 years ago was the last major magmatic eruption. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent active crater containing a 500-m-wide acid lake located ENE of Von Seebach crater.

Information Contacts: E. Fernández, W. Sáenz, E. Duarte, M. Martínez, S. Miranda, F. Robichaud, T. Marino, M. Villegas, and J. Barquero, Observatorio Vulcanologico Sismologica de Costa Rica-Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica (URL: http://www.ovsicori.una.ac.cr/).


Sheveluch (Russia) — April 2011 Citation iconCite this Report

Sheveluch

Russia

56.653°N, 161.36°E; summit elev. 3283 m

All times are local (unless otherwise noted)


Ongoing dome growth into early 2011; and pyroclastic flows of 27 October 2010

This report first describes activity seen at Shiveluch during December 2010-March 2011. Data from that interval included several ash plumes visible as they blew to over 100 km from the volcano. Thermal imagery analysis showed the character of the dome and the path of pyroclastic-flow deposits during that interval. After that, we provide a follow-up to the 27 October 2010 eruption (BGVN 35:11), adding some previously unmentioned details. That eruption destroyed the dome's SE sector and generated pyroclastic flows.

During December 2010-March 2011, KVERT reported that Shiveluch both underwent moderate seismicity and emitted bright thermal anomalies conspicuous in satellite imagery (figure 27). Details of significant explosions and ash plumes during that time appear on table 10. Figure 28 shows a photo with the distant skyline dominated by a long Shiveluch ash plume.

Table 10. An inexhaustive synopsis of significant plumes at Shiveluch visible on satellite imagery from December 2010 through 26 March 2011 (times and dates are UTC). Courtesy KVERT.

Date Comments
03 Dec 2010 Ash plumes drifted 322 km SE.
14 Dec 2010 Ash plume drifted 230 km NE, 2-km-long pyroclastic flow.
23-24 Dec 2010 Ash plumes rose to altitudes as high as 4.5 km
02 Jan 2011 Ash plumes rose to altitudes as high as 8 km and drifted 92 km S.
18 Jan 2011 Ash plumes rose to altitudes as high as 7 km and drifted W.
26 Jan 2011 Ash plume drifted 54 km S.
31 Jan-1 Feb, 4 Feb 2011 Ash plume drifted 120 km NE, E. Ash plumes rose 7.5 km
23-24 Feb 2011 Ash plumes altitudes below 6 km and drifted 220 km SE (figure 28).
26-27 Feb 2011 Ash plumes drifted over 140 km N.
10, 16 Mar 2011 Ash plumes drifted 312 km W, NW.
18-20 Mar 2011 Ash plumes drifted 373 km SE, N.
26 Mar 2011 Ash plumes drifted 57 km SE.
Figure (see Caption) Figure 27. Satellite thermal anomalies recorded at Shiveluch during December 2010-March 2011. Data from KB GS RAS, with cooperation from Alaska Volcano Observatory (AVO).
Figure (see Caption) Figure 28. A panoramic photo showing a long ash plume from Shiveluch, seen in the distant parts of the photo (volcano is on the left). Photo taken on 24 February 2011 from N slope of Kliuchevskoi volcano by Yuri Demyanchuk.

More on the 27 October 2010PFs. As previously reported, an explosive eruption on 27 October 2010 (BGVN 35:11) vented at the dome and destroyed its SE portion, generating pyroclastic flows laden with many fragments of dome material (figure 29). The associated eruptive plume extended more than 1,500 km from the volcano. The pyroclastic flows traveled SSE in a radial direction, as far as 20 km from the source.

Figure (see Caption) Figure 29. Two images showing the lava dome of Shiveluch. Photo (a) was taken before the eruption, on 7 October 2010. Photo (b) was taken a few days after the eruption, on 2 November 2010 and discloses enormous losses to the mass of the dome toward the SE (free face). The large ash clouds from the dome document ongoing explosions, processes associated with continued rebuilding of the lava dome. Both photos courtesy of Yuri Demyanchuk.

Near the dome, visiting scientists found agglomerate deposits of fragmental dome material spread widely down the SE slope. The character of the deposits was similar to debris avalanches, since so much dome material suddenly traveled down slope. The pyroclastic flow deposits retraced numerous upslope tributaries along the Kabeku River. The deposits filled small valleys and other low-lying areas, leveling landscapes that had prior to the eruption been rough (figure 30).

Figure (see Caption) Figure 30. Photo showing the fresh pyroclastic flow deposits filling Bekesh river valley to the point where the valley had become nearly flat in transverse profile. In the background appears the steaming, Shiveluch with its recently broken lava dome. Photo taken 2 November 2010 by Alexander Ovsyannikov.

Figures 31a and b, satellite images, illustrate the trail of hot material descending to the S. They formed a large, complex, and widely distributed deposit following the recent collapse of the lava dome. A sub-circular area about ~4 km in diameter at about 9-14 km distance from the dome may reflect denser deposition (figure 31a). The images make clear that pyroclastic flow deposits descended yet farther, leaving dense, thermally radiant tracks over narrower valleys trending to the SE. The images are from ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). Figure 31b shows the flow's heat signature as measured in thermal infrared energy. The white area at the lava dome was very hot, while the red areas on the edge of the flow were merely warmer than the surrounding snow.

Figure (see Caption) Figure 31. (a) False-color ASTER satellite image of Shiveluch showing the visible-wavelength information that discloses the remnants of the 27 October 2010 pyroclastic flow. Image taken 25 February 2011. (b) The hot pyroclastic flow appears in this ASTER image made using thermal infrared wave lengths. The white area at the lava dome is very hot, while the red areas on the edge of the flow are simply warmer than the surrounding snow. Image taken on 25 January 2011. Courtesy of NASA Earth Observatory.

Fieldwork in the distal area revealed that the most powerful pyroclastic flow went into the headwaters of two narrow valleys, then merged into a single stream down into the Kabeku Valley river almost to its confluence with the Bekesh river (5 km N of the Kluchi-Ust'-Kamchatsk road, figures 32 and 33).

Figure (see Caption) Figure 32. Images (a) and (b) show Shiveluch deposits of pyroclastic flows in the Bekesh river valley. Note person in distance in center of photo for scale. Courtesy Yuri Demyanchuk and Alexander Manevich.
Figure (see Caption) Figure 33. Results of pyroclastic surges, with small trees and shrubs knocked over and stripped of bark. Trees and shrubs showed signs of scorching up to 3-4 m high. Deposits of pyroclastic surges were found on the sides of the Bekesh river valley. Image taken 2 November 2010. Courtesy of Yuri Demyanchuk.

Water in the bed of the Bekesh river ran down the same path as thick pyroclastic flows and continued to be fed by melting snow on the upper slopes. Water also seeped through the loose pyroclastic flow deposit, resulting in large amounts of steam escaping at the surface in the form of fumaroles, degassing pipes, and zones of jetting emissions. This created the impression that the river water was boiling; on its surface rose a wall of steam (figure 34). Walking over the pyroclastic flow deposit was difficult and potentially dangerous, since the deposit's upper portion remained hot and gas saturated (figure 34b).

Figure (see Caption) Figure 34. At Shiveluch, fresh pyroclastic-flow deposits occurring on the Bekesh river. (a) Steam and gas pervade the atmosphere as the river makes its way across the fresh pyroclastic-flow deposits. (b) The still-hot deposits emitting abundant steam and gas. Photos courtesy of Yuri Demyanchuk.

Reference. Ovsyannikov, A., Manevich, A., 2010, Eruption Shiveluch in October 2010, Bulletin of Kamchatka Regional Association (Educational-Scientific Center); Earth Sciences (in Russian), IV&S FEB RAS, Petropavlovsk-Kamchatsky, 2010, vol. 2, no. 16, ISSN 1816-5532 (Online).

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Institute Volcanolohy and Seismology Far East Division, Russian Academy of Sciences (IVS FED RAS), Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences (KB GS RAS) (URL: http://www.emsd.iks.ru/index-e.php). 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/); Y. Demyanchuk, A. Ovsyannikov, A. Manevich (IVS FED RAS); Alaska Volcano Observatory (AVO), a cooperative program of the U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/); Tokyo Volcanic Ash Advisory Centre (VAAC), Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); NASA Earth Observatory (URL: http://earthobservatory.nasa.gov/).

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 (BGVN 22:08) False Report of Mount Pinokis Eruption

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

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

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

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

UFO adherent claims new volcano in Sea of Marmara

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

Fumaroles and minor seismicity since October 2002

12/2005 (BGVN 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/).