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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 26, Number 08 (August 2001)

Managing Editor: Richard Wunderman

Etna (Italy)

Strombolian activity during May and June 2001

Fuego (Guatemala)

Seismic activity during April and December, eruption in September 2000

Jackson Segment (Undersea Features)

Additional investigations show no evidence of April eruption

Karymsky (Russia)

Increased seismicity from December 2000 through September 2001

Lopevi (Vanuatu)

June 2001 lavas, debris avalanches, <= 1.5 m ashfall, and 7.5-km-high plume

Mayon (Philippines)

Two main episodes in 2001; quiet seen in late August

Okmok (United States)

Small earthquake swarm during 11-15 May 2001

Popocatepetl (Mexico)

Steam-and-ash emissions, periods of dome growth during 2001

Semeru (Indonesia)

Continuous seismic activity, plumes to ~11.6 km

Sheveluch (Russia)

Eruption on 15 July, pyroclastic flows and explosion on 23 August 2001



Etna (Italy) — August 2001 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Strombolian activity during May and June 2001

During 14-20 May 2000, lava emission continued from the N fissure of the Southeast Crater (SEC). At about 1900 on 17 May there was an increase in the intensity of Strombolian activity and lava began to flow in several directions, forming two sub-parallel tongues toward the E. On 18 May observers noted that the lava flow emerged from a single vent at 3,156 m elevation, with an effusion rate of 2.5-4.5 m3/s. A short distance below the effusive vent, the flow divided into three branches: one to the NE, whose front flowed at about 2,700 m and reached a distance of about 1 km from the vent; the central branch flowing to the E, widest of the three with some points wider than 20 m; and one to the S, flowing below 3,000 m elevation at about 700 m from the vent. The farthest lava front was estimated to reach ~2,700 m elevation, 1.2 km from the vent. During this period, the Bocca Nuova (BN) crater continued to degas, accompanied by occasional emissions of brown ash. Also noted were a further deepening and widening of the internal crater in the BN's SE quadrant.

During 21-27 May, lava flows from the N fissure of SEC continued intermittent and variably intense Strombolian activity. Sporadic emissions of brownish-reddish ash came from the N crater of BN. Problems with surveillance cameras precluded continuous observation of the summit craters; however, on the morning of 24 May, renewed explosive activity was seen. Observations from Belevedere showed three hornitos on the N flank of the SEC, which emitted pulsing pressurized gas. The lava flow was active and well fed, with branches of ~1.5-2 km in length.

Activity at SEC increased considerably during 28 May-3 June. On 28 May, the presence of a small cinder cone, possibly having formed slowly over recent months, was discovered at the base of Northeast Crater (NEC), occupying about 2/3 of the crater floor and at least 20 m high.

At SEC, evidence of Strombolian activity was masked by discrete flows of gas and steam. The active lava field on the N flank, emerged from a main vent at about 3155 m elevation, which fed two principal flows, one to the E and one to the NE (then turning E). The latter flow formed a lava tube and then re-emerged ~100 m downstream from a small tumulus from which spewed other lava flows, the longest of which extended more than 1.5 km. The S-most branch also initially flowed partly inside a lava tube.

During the evening of 28 May, between 2222 and 2242, Strombolian activity at SEC rose sharply, with ejecta reaching as high as 50 m above the crater rim and with materials occasionally falling on other flanks of the cone. Lava flow rates on 29 and 30 May were estimated at 6-8 m3/s. Temperatures measured using a K-type (Cr/Al) thermocouple showed a maximum temperature on the inside of an expansion bulb to be of 1,065°C at 5 cm depth. Intense degassing continued at SEC for the next several days.

On the evening of 3 June two sub-parallel lava flows descended to the E, of which the northernmost was the longest and reached at least 2,600 m elevation. A few hundred meters ahead of its front, a small branch flowed N but stopped soon after. The other flow was directed toward the Valle del Bove and its advances were discontinuous. Further deepening of the two interior Voragine vents was observed. Eruptive activity was not continuous.

The W rim of BN had a very warm fissure that ran to the N. The N vent was much widened, but it was not possible to observe the base. During observations, gas explosions occurred about every 15 minutes, but it was not possible to observe the fall of ejecta. The S vent had also widened and deepened. On its SE flank, a small semi-circular vent emitted rumbling explosions every 3-10 minutes, accompanied by mostly blue-colored gas mixed with brown ash.

Although intense degassing did not permit views of the interior of the NEC, an apparently recent fissure on the N side of the cone was very warm.

During 4-10 June, two episodes of lava fountaining occurred at the SEC. The first began during the night of 5-6 June, with modest Strombolian activity at the SEC's secondary vent. At 2136 on 6 June, Strombolian activity at the secondary vent reached a frequency of about one explosion per minute, which in successive hours included the main vent as well. The activity eventually climaxed at 0145 on 7 June, when the secondary vent produced a lava fountain whose altitude reached 50 m. Falling to the ground, the stream of lava formed a primary lava flow, which immediately divided into three branches and stopped at about 3,000 m elevation. A second stream flowed to the N before turning E, reaching 2,600 m and superimposing in part on earlier lava flows. The eruptive episode concluded about 0340, with copious ash emissions from the SEC and the BN.

On the night of 8-9 June, a new eruptive episode occurred at the SEC, also beginning with Strombolian activity at 2011 at the principal and secondary vents. The activity evolved into lava fountains which reached a maximum altitude of about 200 m at the principal vent and about 80 m at the secondary vent. The strong activity continued until about 0322 and was accompanied by sustained lava emissions from the secondary vent, which gave rise to two flows which spread to the E and N respectively, superimposing themselves over preceding lava flows.

Activity at the other craters during this period was characterized by continuous degassing at the Voragine and NEC, accompanied, as in the case of the BN, by frequent ash emissions in the SE sector of the crater.

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

Information Contacts: Sistema Poseidon, a cooperative project supported by both the Italian and the Sicilian regional governments, and operated by several scientific institutions (URL: http://www.ct.ingv.it/en/chi-siamo/la-sezione.html).


Fuego (Guatemala) — August 2001 Citation iconCite this Report

Fuego

Guatemala

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

All times are local (unless otherwise noted)


Seismic activity during April and December, eruption in September 2000

Ash venting began at Fuego on 5 April 2000, followed by increased ash emissions and strong seismic signals during 7 and 8 April, according to the Guatemala Volcano Observatory and the Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH) of Guatemala. On 8 April at 0215 a hot spot was visible in multi-spectral imagery. More hot spots were occasionally noted but there were no further reports of ash.

A news article from La Hora reported that a column of ash reached 1 km on 29 August 2000. According to the Guatemala Volcano Observatory, an eruption beginning on 6 September emitted an ash-and-steam plume that reached ~800 m. On 21 September a large amount of ash was emitted, blanketing nearby communities. Authorities considered evacuating residents and issued an Orange Alert for the area near the volcano.

Satellite imagery on 7 December showed an ash plume to the SW of the summit, extending 39 km and 11 km wide. According to ground observations the ash was centered at ~4.9 km elevation. INSIVUMEH reported that the volcano was producing loud rumbling sounds and a more significant eruption was likely. On 9 December 2000 satellite imagery confirmed a small eruption at about 1645. The eruption sent an ash cloud to ~4.5 km altitude, near the summit level. The ash cloud was initially dense, about 8 km wide, and drifted W and NW. By 2345, the cloud had dissipated and was no longer visible on satellite imagery. Occasional strong hot spots were visible on GOES-8 multi-spectral imagery throughout the day. That evening, volcanologists in Guatemala indicated that the volcano had become increasingly unstable with several explosions occurring within a few hours. Since then, no major activity has occurred.

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

Information Contacts: Otoniel Matías and Eddie Sánchez, Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hidrologia (INSIVUMEH), Ministero de Communicaciones, Transporto, Obras Públicas y Vivienda, 7a. Av. 14-57, zona 13, Guatemala City 01013, Guatemala (URL: http://www.insivumeh.gob.gt/); Washington Volcanic Ash Advisory Center, NOAA Satellite Services Division, NESDIS E/SP23, NOAA Science Center, Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ospo.noaa.gov/Products/atmosphere/vaac/); La Hora (URL: http://www.lahora.com.gt/).


Jackson Segment (Undersea Features) — August 2001 Citation iconCite this Report

Jackson Segment

Undersea Features

42.15°N, 127.05°W; summit elev. -3100 m

All times are local (unless otherwise noted)


Additional investigations show no evidence of April eruption

After a 3-9 April 2001 seismic swarm that was traced to the Jackson Segment of the Gorda Ridge (BGVN 26:03), seismically inferred volcanism remained unconfirmed. The signals detected on 3 April 2001 were located on the S side of the segment, and continued through 9 April. During a six-day period instruments detected over 3,500 earthquakes; 548 epicenters were located. By 11 April seismic activity was at very low levels, possibly below the detection threshold of the T-phase monitoring system.

On 10 April, an NSF- and NOAA-funded response team departed on the ship RV New Horizon to search for mega-plumes from the event, but no plumes were detected. On 26 April the U.S. Coast Guard ship Healy conducted conductivity, temperature, and depth (CTD) probes and took dredge samples on the site. A report made available in late May indicated that investigations from the Healy also failed to find evidence of an eruption at the Jackson Segment and detected no significant thermal anomalies from hydrothermal plumes. Rocks recovered by dredge from the sea floor were clearly old. The entire segment was also resurveyed with multibeam sonar to compare with bathymetry collected before the earthquake swarm. The early April earthquake swarm may have indicated moving magma that never made it up to the sea floor to erupt.

Geologic Background. The Jackson Segment of the Gorda Ridge more than 200 km off the coast of Oregon lies immediately SSW of the North Gorda Ridge, the northermost of five segments forming the Gorda Ridge spreading center. The first recorded activity took place in April 2001, when volcanic seismicity was detected by hydroacoustic monitoring. The seismicity indicated possible dike propagation to the south and was similar to that which was documented at the time of the eruption of a submarine lava flow from the adjacent North Gorda Ridge segment in 1996. The 2001 activity originated from the central axial valley of the Jackson Segment, near the "narrowgate" on the southern part of the segment. Later surveys, however, revealed no evidence for submarine eruptive activity in April 2001.

Information Contacts: Bob Embley (NOAA/PMEL) and Jim Cowen (SOEST, Univ. of Hawaii), NOAA Pacific Marine Environmental Laboratory (PMEL), 2115 SE Osu Drive, Newport, OR 97365 USA (URL: https://www.pmel.noaa.gov/).


Karymsky (Russia) — August 2001 Citation iconCite this Report

Karymsky

Russia

54.049°N, 159.443°E; summit elev. 1513 m

All times are local (unless otherwise noted)


Increased seismicity from December 2000 through September 2001

Since the activity reported from June through mid-October 2000 (BGVN 25:09), the Kamchatkan Volcanic Eruption Response Team (KVERT) reported that seismic activity at Karymsky remained mostly at background levels, with a few episodes of increased seismicity.

On 20 December 2000 around 0915 shallow earthquakes under the volcano were accompanied by short-lived explosions. At 2150 the same day a pilot confirmed the presence of ash at the summit of the volcano and mud traces from melting snow on the edifice slopes. The Concern Color Code was increased from Green (volcano is dormant; normal seismicity and fumarolic activity) to Yellow (volcano is restless; eruption may occur) until 29 December.

On 2 and 28 February several shallow seismic events took place, including a 5-minute-long series of weak shallow earthquakes on 28 February. During March, small shallow earthquakes and one episode of weak high-frequency spasmodic tremor were registered. On 12 March a high-frequency signal lasted for 90 minutes. On 28 March, from 1205 to 1300, an intense series of earthquakes with magnitudes up to ~3 was registered. Several local low-frequency earthquakes occurred during the end of March and beginning of April. Around 20 April, more than 40 earthquakes with magnitudes up to ~2.5 occurred. Since then through at least September 2001, seismic activity at Karymsky has remained at background levels with the exception of 23 August, when 30 earthquakes were registered.

General Reference. Khrenov, A.P., and others, 1982, Eruptive activity of Karymsky Volcano over the period of 10 Years (1970-1980): Volcanology and Seismology, no. 4, p. 29-48. Tokarev, P.I., 1990, Eruptions and seismicity at Karymskii volcano in 1965-1986: Volcanology and Seismology, v. 11, p. 117-134 (in English).

Geologic Background. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.

Information Contacts: Olga Chubarova, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Tom Miller, Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Lopevi (Vanuatu) — August 2001 Citation iconCite this Report

Lopevi

Vanuatu

16.507°S, 168.346°E; summit elev. 1413 m

All times are local (unless otherwise noted)


June 2001 lavas, debris avalanches, <= 1.5 m ashfall, and 7.5-km-high plume

Lopevi erupted explosively on 8 June 2001, with additional eruptions at least through the 19th. The current eruptive period, which started in July 1998, continued during 1999 and 2000 (BGVN 24:02, 24:07, 25:04, and 26:06). This report covers June and July 2001.

The explosive eruption that began around 1100 on 8 June generated an eruptive plume, a lava flow on the NW flank, and two debris avalanches on the W flank (figure 12). During the explosive activity, a crater opened at ~200 m elevation on the NW flank along the SE-NW crack. The ash plume rose to ~7,500 m (as determined by NOAA satellite data analysis). The ash blew NW, carried by ~35-45 km/hour winds; tephra-fall deposits on Lopevi reached ~0.5-1.5 m thick. As much as 7 cm of ash fell on the E coast and middle of Paama Island, 5 km WNW with ~1,700 residents, reaching a thickness of 7 cm.

Figure (see Caption) Figure 12. Sketch map of Lopevi showing the location of June 2001 deposits on the NW and NNW flanks. One lava flow and two debris avalanche deposits date from the 8 June 2001 eruption. Farther N, two lava flows date from the 15 June 2001 eruption. Produced from an original map by A-J. Warden including observations by A-J. Warden and R. Priam (Archive Service de Mines); revised and updated by S. Wallez and D. Charley; drafted by A. Mabonlala. Courtesy of IRD.

About 11 hours after the eruption the Along-Track Scanning Radiometer (ATSR-2) research instrument on the European Remote-Sensing Satellite (ERS-2) obtained data from which an image of the plume could be derived (figure 13). The instrument has infrared detection channels at ~11 and ~12 µm, which are used to discriminate ash from meteorological clouds. The image shows the temperature difference between the 11 and 12 µm channels. The greater this negative difference, the greater the likelihood that there is ash; larger negative differences usually mean more ash. A possible explanation of the complex plume structure shown on figure 13 is the presence of atmospheric water vapor, which would mask the ash signal over some parts of the plume. Water vapor has the opposite effect of ash on the image: a positive difference is created because water vapor tends to make the 11µm temperature larger than the 12 µm temperature.

Figure (see Caption) Figure 13. Lopevi ash plume as imaged by the ATSR-2 instrument on 8 June 2001 at 1134Z. The unlabeled island SW of the plume is Lopevi. The areas with the most ash are in the center of the shaded plume area. Courtesy of Fred Prata, CSIRO.

The 8 June explosion caused instability on the W flank that produced two debris avalanches-unsorted deposits composed of older material (figures 14 and 15). The smaller of the two avalanches was composed of fine gray debris. It occurred next to the lava flow from the NW-flank crater. The larger avalanche, which reached the sea, was beige in color and included basaltic lava fragments, unburned vegetation, and red and black scoria of the sort commonly found on the steep (45°) upper slopes. The scoria and other observations were consistent with this debris avalanche resulting from a partial collapse of the active cone. Aa lava from the NW-flank crater spread out along the coastline (figure 14) on the SW side of the 2000 lava flows (figure 16). This flow had cooled by the time of a field visit on 11 June.

Figure (see Caption) Figure 14. Lopevi's NW coastline showing the 8 June aa lavas and debris avalanches (barely visible); older lavas from 2000 also appear. The photograph was taken on 9 June 2001. Courtesy of S. Wallez.
Figure (see Caption) Figure 15. Lopevi's two W-flank debris avalanches produced during the 8 June 2001 eruption (photographed 9 June 2001). Courtesy of S. Wallez.
Figure (see Caption) Figure 16. Sub-vertical aerial photograph showing lava flows that reached the NNW coast of Lopevi during 2000. Additional lava flows from the June 2001 eruptions covered parts of the SW and NE areas of this delta. N is to the right. Courtesy of S. Wallez.

On a second visit during 14-17 June, geologists saw two new NW-flank flows, which they mapped and photographed (figures 12 and 17). Their guide said the lava flows were emplaced on 15 June 2001. These flows began at a height of ~400 m and added to a delta with a width of ~350 m at the coast.

Figure (see Caption) Figure 17. View of Lopevi from the ocean looking towards the NW coast towards the lava flows from 2000 and both 8 and 15 June 2001. Courtesy of S. Wallez.

According to United Nations reports, the strong SE trade winds had deposited ~18 cm of ash on Paama Island as of 20 June, and lesser ashfall on Ambrym and Malekula islands. The worst affected villages were Luli, Lulep, and Liro on Paama. Overall, it was estimated that 4,000-5,000 people were directly affected by the ashfall on Paama and SE Ambrym. The ashfall on Paama polluted open water-supplies, bringing the pH to 3-4, and caused darkness for a few hours beginning at about 1500 on 8 June. The 12 June report noted that the government of Vanuatu had approached the Australian High Commission in Port Vila and in response an Australian ship in the area, HMAS Kanimbla, was deployed to deliver drinking water from Red Cross stocks. The Vanuatu Red Cross Society provided water, blankets, and soap, as well as participating in assessment activities with government officials and scientists. The National Disaster Management Office reported to the UN that more ashfall occurred on the night of 19 June. As of 20 June sources of potable water had been identified, but there remained a shortage of cooking and wash water. As a precaution, 105 students and five teachers from Paama were evacuated to schools on other islands, but most residents remained and were occupied with clearing ash from roofs, water tanks, and gardens.

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

Information Contacts: Sandrine Wallez and Douglas Charley, Department of Geology, Mines & Water Resources (DGMWR), PMB 01, Port-Vila, Vanuatu; Michel Lardy, Institut de Recherche pour le Développement (IRD), Bondy, Paris, France; Fred Prata, Senior Principal Research Scientist, Commonwealth Scientific and Industrial Research Organization (CSIRO), Atmospheric Research, PB 1 Aspendale, Victoria 3195, Australia; United Nations Office for the Coordination of Humanitarian Affairs (OCHA), New York, NY 10017 USA (URL: https://reliefweb.int/).


Mayon (Philippines) — August 2001 Citation iconCite this Report

Mayon

Philippines

13.257°N, 123.685°E; summit elev. 2462 m

All times are local (unless otherwise noted)


Two main episodes in 2001; quiet seen in late August

Mayon has undergone two eruptive episodes thus far in 2001. The first episode began in January 2001 and involved a period of unrest that culminated in explosive eruptions on 24 and 29 June. The second episode took place on 20 July, climaxing on 26 July. Low-level lava spattering and active degassing continued for days after the latter climax but activity dropped in early August.

The stratovolcano was last reported on through 31 May 2001 (BGVN 26:05); the present report covers through mid-August 2001. The volcano's Alert Levels are discussed in more detail in the last section.

Precursors and minor explosive activity. Unrest during the year 2001 was first recognized on 8 January when the Lignon Hill Observatory (LHO) in Legaspi City (11.5 km SE of the summit) reported a blocky lava dome growing on top of the summit. Lava dome extrusions occurred before an explosive eruption the previous year, so the January 2001 dome was an ominous sign of renewed activity. From January to April 2001, the dome slowly grew and sporadic ash explosions accompanied or followed periods of seismic unrest. The hazard status was set at Alert Level 2, signifying the ascent of magma.

During the second week of May, LHO staff noticed that the growing summit lava dome overlapped the unconfined side of the SE crater rim. At 1752 on 11 May a minor explosion ejected ash and vapor to 50 m above the summit. A series of similar small explosions followed on 12 May that were likely triggered by magma intruding into the dome. As a result, the SE portion of the dome partially collapsed.

Subsequently, the SE flank of the dome facing the observatory glowed conspicuously and lava fragments began to detach from the summit lava dome. Rockfalls were episodic at first and it was not clear initially whether detaching lava was caused by instability of the growing dome or due to the effects of increased internal pressure.

In time, observations from Bonga, ~8 km SE of the summit, indicated that incandescent rockfalls were apparently caused by slowly ascending magma entering the dome. The magma was degassed but hot, presumably a remnant of magma erupted during 2000. PHIVOLCS later postulated that ascending magma punched an exit point on the SE flank of the growing lava dome. This material then spilled into the Bonga Gully, with hot lava boulders as big as trucks falling, rolling, and sliding to form a pyroclastic apron on slopes at 1,800-2,000 m elevation. Rockfall activity, monitored via the seismic network, progressively increased in frequency until magma discharge was sufficient to form a stubby lava flow on 17 June. By 20 June, the seismograms displayed more or less merging codas of high-frequency tremor, which suggested that lava extrusion dominated earlier rockfall activity. As seen earlier, the lava flow was thought to represent relatively fresh but still degassed magma.

Lava fills crater then extends 5 km. By 22 June, lava had already buried the summit dome and partially filled the crater. Lava was no longer exiting from a single patch at the side of the dome but from the whole breadth of the SE summit.

Episodes of conspicuous summit glow began on 23 June, and intensified to a pulsating light-yellow incandescence by early evening. The summit did not stay quiet for long because the crater began to vent voluminous gases and to shower spatter around the summit. COSPEC readings indicated an SO2 flux of ~7,000 metric tons per day (t/d), well above the baseline of ~500 t/d. At about 1909 on 23 June, a period of low-level lava fountaining began to feed lava flows that eventually descended from the summit elevation to ~500 m elevation-a distance of ~5 km.

When lava fountaining commenced the Alert Level rose from 3 to 4. This status meant that PHIVOLCS considered a hazardous eruption imminent, within hours to days. The corresponding Level 4 Bulletin carried with it a recommendation to evacuate areas within the 6-km-radius Permanent Danger Zone (PDZ) and a 7-km-radius Extended Danger Zone (EDZ) in the SE sector. The EDZ provided a buffer zone to the Bonga Gully, which descends from near the crater mouth to the lower mid-slopes (~600 m elevation) to the SE, a distance of ~4 km. By 0100 on 24 June the PDZ and EDZ were fully evacuated through the efforts of a group called "Task Force Mayon," a military and civilian organization charged with implementing the evacuation of the danger zones. Temporary shelters received ~25,000 people.

At 0317 on 24 June a series of explosions fed an ash column that rose to ~1 km above the volcano's summit. A thin blanket of ash fell mainly on the northern half of the volcano in the vicinity of barangays (hamlets) Amtic and Tambo of Ligao City and San Vicente, San Antonio, Quinastillojan, Bantayan, Tabiguian, and Buang of Tabaco City.

First substantial pyroclastic flows. Although lava fountaining and small ash puffs signaled the start of explosive activity, it was not until 1245 on 24 June that the first major pyroclastic flow occurred. It followed the eastern branch of the Bonga Gully in the general direction of Barangay Buyuan. PHIVOLCS promptly raised the status to the highest Alert Level, 5, first verbally to provincial disaster-mitigation officials shortly after 1245, followed by an official bulletin released by 1300. Alert Level 5 provided a reminder that hazardous eruptions were taking place. Although the 1245 pyroclastic flow was short-lived and ran down to the middle slopes only (~700-1,000 m elevation), this again-elevated status emphasized that more explosive eruptions were expected.

At 1444 on 24 June, large explosions commenced and generated multiple pyroclastic flows around the cone. Ash clouds from the eruption column and pyroclastic flows enveloped the volcano in ash and rose to ~10 km altitude. Although the volcano seemed to disappear within its own eruption clouds, giving the impression of massive explosions that might have threatened the lowlands, the pyroclastic flows and lava flows were all contained within the PDZ, with maximum runouts to only ~5.5 km.

Considerable airfall ash blanketed the northern areas, particularly the cities of Ligao and Tabaco, but this was chiefly a function of wind velocity and direction, because the wind mostly comes from the SW this time of the year.

Eruptions continued until 1921 on 24 June when seismographs began to record diminishing eruption intensity as indicated by decreasing harmonic tremor amplitudes. However, sporadic explosive eruptions continued throughout the evening as LHO noted light ashfall in Legaspi up to about 2135 that day. Thereafter, during 25-28 June, Mayon remained quiet, although Alert Level 5 was maintained in anticipation of more explosions.

At around 1605 and 1702 on 29 June, Mayon erupted again and sent relatively small pyroclastic flows down the Bonga Gully to the SE. Over the period 30 June to 19 July, Mayon's apparent activity waned and the hazard status was eventually lowered to level 3 (which states that an eruption may still be expected within the coming weeks). Observations in support of reduced activity included a general deflation of the edifice, decreased seismic activity, lowered gas emission rates, and the disappearance of summit incandescence. The first eruptive episode ended and scientists inferred that intrusions into the cone had ceased.

Activity during late July 2001. Mayon's eruptive episode during July 2001 was essentially a continuation of June's activity. On 20 July seismographs around the volcano recorded high-frequency, short-duration tremor associated with rockfalls. The number of seismically detected rockfalls had already declined from the pre-June 24 eruption level of more than 200 events per day to (by 19 July 2001) a post-eruption level of less than ~10 events per day. The latter number was attributed to unstable, freshly deposited lavas on steep upper slopes.

Scientists were alerted when the S-flank seismic station at ~800 m elevation registered an abrupt increase, from 5 rockfall events on 19 January to 48 events on 20 January. Over the same time period an upper seismic station (at 1,700 m elevation) recorded a jump from 25 to 142 events. Incandescent rockfalls became persistent.

Other striking changes soon occurred. On 21 July the SO2 flux tripled, to 7,400 t/d. The uppermost electronic tiltmeter (at 1,700 m elevation) fluctuated by ~20 µrad. Crater glow increased and rockfall occurrences peaked.

PHIVOLCS inferred that Mayon had again entered a mild eruptive stage. The character of unrest resembled activity observed between mid May and 20 June, prior to explosive eruptions on 24 June. Scientists recognized that an explosive and hazardous eruption could occur anytime. By 23 July, PHIVOLCS gave the Albay provincial government a notice of increasing unrest and by 25 July, the Municipal Mayors were informed of reactivation and possible explosive eruption of Mayon.

Overall, unrest was accelerating. On the morning on 25 July, the bulletin also added that the current extrusion of lava was clear evidence of eruption and that more explosive eruptions were expected. At 0418 on 25 July seismometers detected more or less continuous high-frequency tremor. Although clouds shrouded Mayon, volcanologists believed these signals indicated that a lava flow had extruded from the dome, an idea confirmed when observers saw a short lava tongue draping the SE slope just below the summit crater.

During 0219-0315 on 26 July, LHO staff saw mild lava fountaining that reached to ~70 m high. This prompted the return to Alert Level 4 at 0400 on 26 July and a rapid evacuation. During quiet times, farmers work portions of land within the 6-km-radius PDZ, but at Alert 4, people in this zone are required to evacuate as quickly as possible. As in the previous 24 June eruption, a 7-km-radius SE-flank EDZ was also declared (to include river gullies upstream of barangays Mabinit, Bonga, Buyuan and Matanag). But, lava fountaining declined at about 0400 and the volcano seemed quiet. This led some people to be initially lax, and some farmers viewed the lull as an opportunity to gather their livestock near the Bonga Gully. PHIVOLCS firmly advised not to proceed. This warning proved justified when at 0538 a brief burst from the crater sent an ash cloud to ~500 m above the summit. This was accompanied by a low-frequency type earthquake that lasted for about a minute. A lack of urgency towards evacuating may have been widespread. Legaspi City Mayor Rosal made the following admission, which appeared in The Philippine Star the next day. "We were surprised by its sudden explosion. We were told to evacuate last night but we did not know it would explode so fast."

At 0745 on 26 July there occurred another ash explosion with similar seismic signature. In retrospect, sequences of low-frequency seismic events were detected by the Mayon Resthouse station (780 m elevation) before the onset of explosive eruptions at 0756 on 26 July. These events were not detected at other stations or were obscured by high-frequency tremor associated with both lava flowing out at the uppermost elevations and lava fragments detaching from the advancing lava flow.

The 0756 eruption produced a turbulent head of steam and ash, followed by a column of roiling dark-gray ash clouds. The column convected to ~10 km altitude while pyroclastic flows descended the Bonga (SE flank) and Basud (E flank) gullies. Upper-level winds conveyed the topmost eruption column to the SW. Lower-level winds carried fine ash lofted upwards (elutriated) from pyroclastic flows to the SE. Accordingly, the main ashfall deposit reached ~7 mm or more in thickness to the SW (in Camalig); it included scoria up to 10 cm diameter and perhaps larger. Most scoria fragments broke up upon impact with hard surfaces such as concrete and asphalt, but scoria clasts that landed on softer ground were preserved. A second ashfall deposit occurred to the S, SE, and ESE (in Legazpi, Daraga, and Lidong, respectively), amounting to ~5 mm thickness during this initial eruption. Additional lighter ashfalls occurred to the S (in Daraga) and to the SW (in Guinobatan).

A brief helicopter flight over Albay Gulf looking at Legaspi and Santo Domingo showed the dark curtain of ash progressively blanketing these localities. Pyroclastic flows remained well within the PDZ, a fact used to conclude that additional areas were not endangered. Only small-volume pyroclastic flows were seen descending the S-flank regions (Mi-isi and Anoling gullies).

The eruption that began on 0756 on 26 July lasted for about an hour. Ash clouds remained suspended throughout the day, even when Typhoon Feria's rains swept over Mayon. At 1420 that day another episode of eruptions began. Although the suspended ash and rain clouds covered Mayon, harmonic tremor and booming sounds signified explosive discharge until about 1500. A third and final eruption episode occurred from 1749 until 1810. Like the second period of eruptions, ash and rain clouds obscured much of the volcano from Legaspi. From Santo Domingo, however, pyroclastic flows were seen descending the Basud Gully. A ground survey to Bonga, facing this gully in the SE indicated that very small pyroclastic flows were passing here, yet there were large pyroclastic flows to the E.

When the eruption cleared the following day, observers recognized that the septum between the Bonga and Basud Gullies near the summit had breached. It is therefore very likely that late-stage pyroclastic flows during the third eruptive episode were funneled through Basud and little material was channeled along the Bonga Gully. This demonstrates the high probability that subsequent flows will also affect the eastern sector and not just the SE. Fortunately, flow runouts remained within defined danger zones.

On 27 July Mayon entered an effusive state as lava from the summit fed a flow that eventually reached ~3.75 km to the SE at an elevation of ~650 m. This was smaller than the lava flow extruded in June; it traveled farther and eventually reached ~5.5 km down the SE slope at ~500 m elevation. Hazy conditions in the SE foothills were caused by ash-and-steam plumes from the summit and from pyroclastic-and lava-flow deposits. Seismicity remained active, with signals from sporadic explosions and persistent background tremor related to lava flows and other surface events. Numerous (206) discrete rockfall signatures, for example, were detected by the seismic network and many of these were visually confirmed from LHO. The resumption of rockfalls was interpreted to not result from another intrusion but from loosened lava debris on steep slopes.

The SO2 flux at 6,450 t/d remained very high on 27 July and even on the following days, SO2 emission rates varied between 3,265 and 9,915 t/d. Voluminous degassing coincided with loud roaring from the crater, which caused some residents of Santo Domingo, at least 8 km E of the crater, to evacuate. According to residents, the last time they heard the crater degas loudly was prior to the resurgence on 23 September 1984, so that they were troubled when they heard another explosive eruption after 26 July 2001. The concern was not at all unfounded. Although incandescence of the summit already diminished to faint conditions as observed from LHO, some low-level fountaining became evident on video cameras with night vision. The cameras clearly showed blobs of lava thrown 100 m above the crater rim. This new observation, along with elevated seismic and SO2 levels, and other monitored parameters, kept the alert status at Level 5.

Waning activity. It was not until there were clearer signals of gradual decline of activity that PHIVOLCS lowered the Alert Level 5 status to Level 4. A bulletin on 9 August 2001 explicitly noted the cessation of explosive eruptions.

After 10 August seismic activity decreased. Background tremor associated with active magma transport had stopped and rockfall occurrences had become insignificant. The number of low-frequency volcanic earthquakes occurring daily was still above baseline, up to 22 events, but this is not unusual after an eruption of Mayon and was probably related to shallow magma degassing. The SO2 fluxes, up to 6,600 t/d, were still very high, presumably for the same reason. Electronic tiltmeters supported the idea of substantial degassing, showing a general deflation episode following the 26 July eruption. In summary, while various monitoring parameters continued to show significant unrest of Mayon, the general trend was one of declining activity. This information may be used to eventually lower alerts over the volcano and allow the return of evacuees to their homes by the end of August 2001.

June and July eruptions compared. The eruptions in June appeared to be more voluminous and produced more lavas than tephra. The estimated volume of 15 x 106 m3 was in the ratio 2/3 lava and 1/3 pyroclastics. The June eruptions also produced pyroclastic flows that ran through many gullies radiating around the cone. The 26 July eruption produced roughly similar proportions of lava and tephra (namely, 5 x 106 m3 lava; 6 x 106 m3 tephra).

When the 26 July pyroclastic flows poured down the SE and E flanks, the low-altitude SE winds caused Legaspi City to be enveloped in ashfall. Legaspi City generally remains ash-free due to seasonal wind patterns. Not fully prepared to cope with ashfall, many residents panicked even though the threats to life were virtually nil. Phone lines jammed and vehicle traffic was backed up for several kilometers on the highway from Rawis, Legaspi City to Padang, and Santo Domingo. Busy communication networks also prevented PHIVOLCS from relaying real-time information by telephone to the central office in Quezon City. Fortunately, anticipation of explosive eruptions earlier that day meant that warnings to local and national authorities were already sent out. A notice to the Volcanic Ash Advisory Center in Tokyo was also made that morning.

Another marked difference between the June and July 2001 unrest was the time interval between perceived disquiet to the day of explosive eruption. The 24 June eruption was preceded by over a month of seemingly increasing rockfall activity. In a sense, rockfalls were an indicator of magma-discharge rates and the number of rockfalls per day progressively increased up until lava-flow extrusion. In contrast, the period between the onset of rockfalls and the 26 July eruption was barely a week, so that magma-discharge rates jumped abruptly before the onset of lava extrusion and explosive discharge.

Background provided by PHIVOLCS. The towering Mayon stratovolcano is famous for its highly conical shape and its symmetry. It is the most active volcano in the Philippines, with 47 historical eruptions since 1616. The typical eruption episode lasting from a few days to about a month produces a sequence of basaltic andesite lava flows, pyroclastic flows, and tephra falls. Based on geological studies on the nature and extent of deposits, a 6-km-radius "Permanent Danger Zone" (PDZ) has been defined to discourage people from permanently occupying hazardous areas.

Table 6 shows the Mayon warning scheme devised by PHIVOLCS. It is similar to the one employed at Pinatubo. Six alert levels provide the general activity status.

Table 6. A simplified version of the current warning scheme used at Mayon. Courtesy of PHIVOLCS.

Alert Level Meaning
0 Volcano is quiet; no eruption in foreseeable future
1 Little unrest, possibly of hydrothermal, magmatic or tectonic activity
2 Moderate unrest of magmatic origin; may lead to an eruption
3 High unrest; tendency towards an eruption within weeks
4 Eruption imminent within days
5 Hazardous eruption in progress

It has been suggested that Mayon erupts every 10 years, referring to the eruptions of 1928, 1938, and 1947. Then there were the eruptions of 1968 and 1978 as well as the interval between 1984 and 1993 events. Yet in recent years, it seems that this general periodicity has changed. The Millennium eruption, 24 February to 7 March 2000, occurred just 7 years after the 1993 outbursts. A similar period of repose is evident in the interval 1978-84. In fact, close inspection of the historical record suggests other intervals with eruption repose periods of less than 10 years.

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

Information Contacts: Ernesto Corpuz, Philippine Institute of Volcanology and Seismology, C.P. Garcia Ave., Univ. Philippines Campus, U.P. Diliman, 1101 Quezon City.


Okmok (United States) — August 2001 Citation iconCite this Report

Okmok

United States

53.43°N, 168.13°W; summit elev. 1073 m

All times are local (unless otherwise noted)


Small earthquake swarm during 11-15 May 2001

Since the February 1997 eruption (BGVN 22:04) until at least September 2001, Okmok has remained relatively quiet, with one period of increased seismic activity. On 11 May 2001, from about 0800 to at least 1700, the Alaska Volcano Observatory (AVO) detected a small earthquake swarm centered near the volcano. Earthquakes in the swarm had magnitudes ranging from ~2 to 3.6. The locations of the earthquakes could not be pinpointed because Okmok is not monitored by a local seismic network. AVO noted that the earthquakes may have been of volcanic origin, but swarms with similar characteristics are not uncommon at Aleutian arc volcanoes and do not necessarily lead to eruptive activity. The earthquake swarm ended by 15 May, and AVO has not reported any further activity at Okmok since then.

Geologic Background. The broad, basaltic Okmok shield volcano, which forms the NE end of Umnak Island, has a dramatically different profile than most other Aleutian volcanoes. The summit of the low, 35-km-wide volcano is cut by two overlapping 10-km-wide calderas formed during eruptions about 12,000 and 2050 years ago that produced dacitic pyroclastic flows that reached the coast. More than 60 tephra layers from Okmok have been found overlying the 12,000-year-old caldera-forming tephra layer. Numerous satellitic cones and lava domes dot the flanks of the volcano down to the coast, including 1253-m Mount Tulik on the SE flank, which is almost 200 m higher than the caldera rim. Some of the post-caldera cones show evidence of wave-cut lake terraces; the more recent cones, some of which have been active historically, were formed after the caldera lake, once 150 m deep, disappeared. Hot springs and fumaroles are found within the caldera. Historical eruptions have occurred since 1805 from cinder cones within the caldera.

Information Contacts: Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA.


Popocatepetl (Mexico) — August 2001 Citation iconCite this Report

Popocatepetl

Mexico

19.023°N, 98.622°W; summit elev. 5393 m

All times are local (unless otherwise noted)


Steam-and-ash emissions, periods of dome growth during 2001

Following an episode of intense volcanic activity at Popocatépetl during December 2000 and January 2001 (BGVN 25:12) volcanic activity through September 2001 consisted of periods of small-to-moderate emissions of steam, gas, and ash, several ash cloud-producing eruptions, periods of many high-frequency volcanic earthquakes, and fumarolic activity. In addition, a new lava dome grew within the crater left after a lava dome was destroyed in December 2000.

The Centro Nacionale de Prevencion de Desastres (CENAPRED) and the Washington Volcanic Ash Advisory Center (VAAC) noted several small-to-moderate sized eruptions during the report period. Large eruptions are discussed below, and others are in table 14.

Table 14. Eruptions at Popocatépetl during February-August 2001 not discussed in the report, based on information from CENAPRED, Washington VAAC, and the México City Meteorological Watch Office via the Washington VAAC. All heights are approximate values above the volcano.

Date Time Description of activity
01 Feb 2001 1345 Narrow ash plume visible in GOES-8 imagery rose to ~1 km, drifted NNE
08 Feb 2001 1921 Small ash cloud rose to 2 km, drifted NE
09 Feb 2001 1400 Ash cloud rose to 2 km
11 Feb 2001 1338 Ash cloud rose to 2.5 km, drifted S
11 Feb 2001 1348 Ash cloud rose to 2.5 km, drifted S
06 May 2001 1205 Steam-and-ash cloud rose to 1.5 km
14 May 2001 0939 Steam-and-ash cloud rose to 1.5 km
26 May 2001 1122 Steam-and-ash emission rose to 1.5 km
01 Jun 2001 0804 Steam-and-ash cloud rose to 1.5 km
09 Jun 2001 0424 Small explosion, most intense phase lasted 30 seconds
11 Jun 2001 1100 Ash cloud rose to 2 km, drifted W
12 Jun 2001 1648 Eruption occurred with the most intense phase lasting 30 seconds, too cloudy to observe ash cloud
24 Jun 2001 0900 Small ash cloud rose to 0.5 km, drifted SW
01 Jul 2001 0912 Ash cloud rose to 800 m, drifted SSW
14 Jul 2001 1045 Steam-and-ash cloud rose to 2 km, drifted W
14 Jul 2001 2303 Eruption occurred, but too cloudy to assign a height to the ash cloud
14 Jul 2001 2341 Ash cloud rose to 0.5 km, drifted NW
24 Jul 2001 0900 Summit-level emission, drifted W
09 Aug 2001 2300 Ash cloud rose to 2 km
17 Aug 2001 1514 Ash cloud rose to 2 km

Volcanic Activity during late January-February 2001. As of late January Popocatépetl was at Alert Level Yellow Phase Three, with a 12-km-radius restricted area. During the end of January through February several moderate-to-small eruptions occurred at Popocatépetl. On 30 January during 1530-1545 a moderate ash emission was visible on CENAPRED's video camera rising to ~1.5 km above the volcano's summit. The ~9-km-wide moderately-dense ash cloud extended from the summit to the N and NE. An eruption on 15 February at 1542 produced an ash cloud that rose to 2.5 km above the summit and drifted to the ENE. The intense phase of the eruption lasted about 15 minutes. The ash cloud was tracked using Geostationary Operational Environmental Satellite-8 (GOES-8) imagery as it drifted to the Gulf of México by 0102 the next day. The NOAA Operational Significant Event Imagery Support Team created a movie loop using images captured by GOES-8 that are available at http://www.osei.noaa.gov/.

New lava dome growth and destruction during March and April. Relatively low volcanic activity during the beginning of March consisted of small steam-and-ash emissions and periods of harmonic tremor. CENAPRED reported that beginning on 12 March volcanic activity rose to high levels, with harmonic tremor occurring for a cumulative hour and approximately 50 small emissions of steam, gas, and occasionally ash. An eruption at 2023 produced an ash column that rose 1 km above the summit and incandescent volcanic fragments were hurled up to 1 km away from the crater to the volcano's N flank.

On 13 March at 1953 another eruption produced an ash column that rose to 2 km. While flying over the volcano the same day CENAPRED personnel observed a new 100- to 150-m-diameter lava dome growing in the inner crater that was created after the December 2000 dome was destroyed. On both 14 and 15 March a cumulative hour-long period of harmonic tremor occurred and 55, and 73 emissions of steam, gas, and ash occurred, respectively. The lava dome was 200 m in diameter and about 40 m tall as of 15 March. On 16 March there was a larger number of volcanic emissions (95) than on the previous couple of days, but less harmonic tremor was registered (0.5 hour). Volcanic activity began to decrease on 17 March, with 38 emissions occurring and 15 minutes of harmonic tremor recorded.

During the remainder of March and early April volcanic activity related to the emplacement of the new lava dome occurred; there were episodes of harmonic tremor totaling up to 8 hours per day, a large amount of high-frequency tremor, an average of two tectono-volcanic earthquakes per day up to M 2.3, and fumarolic activity.

On 16 April at 1948 a moderate eruption produced an ash cloud that rose to 4 km above the volcano's summit and drifted to the SW (figure 37, a and b). The eruption also sent incandescent volcanic fragments up to 2 km from the crater to the volcano's NE and NW flanks. The 40-second-long eruption destroyed the lava dome that had formed within the crater over the course of the previous several weeks. After the eruption the level of volcanic activity stabilized, with a relatively low number of gas, steam, and ash emissions and episodes of harmonic tremor. On 17 April a small lahar traveled down the Achupashal Gorge.

Figure (see Caption) Figure 37. For Popocatépetl, (a) a photograph showing the 16 April 2001eruption at 1949, and (b) thermal image of the 16 April eruption at an unstated time. In the thermal image, the ash cloud is visible rising to 4 km above the volcano's summit. Higher temperatures are represented by red and pink color shades in the area of fresh tephra deposition. The N flank of the volcano is shown. Hot material is visible on the upper NE and NW flanks of the volcano. Courtesy of CENAPRED.

Volcanic activity during late April-July. Following episodes of harmonic tremor during 28 April through early on 29 April a moderate eruption at 0819 produced an ash cloud that CENAPRED reported rose 2 km above the summit and quickly drifted to the ESE. A pilot reported that the ash cloud reached up to 3.5 km. The most intense phase of the eruption lasted approximately 1 minute. Extreme cloudiness obstructed clear views of the volcano, but scientist believe incandescent volcanic fragments were ejected during the eruption. Noise from the eruption was heard in San Pedro Benito Juárez (Puebla), 10 km SE of the volcano. By 0930 small amounts of ash fell in San Pedro Benito Juárez. Another small eruption occurred at 1310 and produced an ash cloud that rose 1.5-2 km above the volcano. After the eruptions volcanic activity returned to previous levels, with episodes of harmonic tremor and small volcanic emissions.

One of the many small eruptions during May occurred on the 13th at 2301 and ejected volcanic fragments up to 0.5 km away from the volcano's crater. Cloudy conditions prohibited observation of a possible accompanying ash cloud. The eruption was followed by an episode of harmonic tremor. A moderate-sized eruption on 31 May at 2136 sent incandescent material 2-3 km from the crater down the NE flank. The ash cloud produced from the eruption rose ~2 km above the volcano's summit and drifted to the W. The most intense phase of the eruption lasted approximately 1 minute. Harmonic tremor started about 90 seconds after the eruption began, and lasted about 5 hours. The following day a similar, but smaller, eruption at 0804 sent a steam-and-ash cloud to ~1.5 km.

Volcanic activity was relatively low in June, with small steam-and-ash emissions (table 4). CENAPRED reported that a moderate-sized eruption occurred on 3 July at 0410, which may have ejected incandescent volcanic fragments around the rim of the summit crater. Later that day, at 0648, a larger eruption produced an ash cloud that rose more than 4 km above the summit in a few minutes (figure 38). According to the Washington VAAC, at least three ash-producing eruptions occurred on 3 July; at 0425, 0648, and 0830. They reported that the 0425 eruption produced an ash cloud that was visible on GOES-8 imagery spreading in two directions at different heights; less than 1 km above the volcano one portion of the ash cloud drifted to the NW, and ~1-4 km above the summit it drifted to the SE (figure 39). Small amounts of ash fell NW of the volcano in the towns of San Pedro Nexapa, Amecameca, Tlalmanalco, San Rafael, Iztapaluc, and as far away as 35 km in Chalco.

Figure (see Caption) Figure 38. Photograph of an eruption of Popocatépetl taken on 3 July 2001 at 0657. The northern side of the volcano is shown. Courtesy of CENAPRED.
Figure (see Caption) Figure 39. Sketch showing the distributions of two portions of a Popocatépetl ash cloud in GOES-8 imagery on 3 July 2001at 0515. The enclosed hatched areas depict the location of volcanic ash. The portion of the ash cloud that drifted to the NW was ~ 1 km above the volcano and the portion that drifted to the SE, ~ 1-4 km above the volcano. Courtesy of Washington VAAC.

Based on information from pilot reports and ground observations, the Washington VAAC reported that the ash cloud was 9.3 km SE of México City airport (~65 km NE of the volcano) at 0930. Very light ash fell on runways at the Mexico City Airport, causing some airlines to briefly suspend takeoffs. CENAPRED's seismic data revealed that the explosive event lasted ~10 minutes, after which volcanism returned to low levels.

On 23 July CENAPRED reduced the Alert Level from Yellow Phase Three to Phase Two because volcanism was lower than it had been in December 2000 when the Alert Level was originally raised (BGVN 25:12). Under the new Alert Level, activity continued to be prohibited within a 12 km radius around the volcano, but controlled travel was permitted on the road between Santiago Xalitzintla (Puebla) ~10 km NE of the volcano and San Pedro Nexapa (State of México) ~12 km NW of the volcano, including Paso de Cortés.

New dome growth episode during August. A new episode of dome growth was first detected at Popocatépetl on 9 August when a significant increase in seismicity at the volcano lasted for about 24 hours. The seismicity was much lower than that detected in the interval beginning on 13 December 2000, a time when the highest amplitude tremor was recorded at Popocatépetl to date. A high-altitude flight took place on 10 August (sponsored by the Secretary of Communication and Transportation); it revealed that a new dome had been emplaced. It emerged at the bottom of the inner crater that formed after the December 2000 dome was destroyed (figures 40 and 41).

Figure (see Caption) Figure 40. Sketch of Popocatépetl's summit crater and the new lava dome as they appeared on 10 August 2001. Courtesy of CENAPRED and Instituto de Geofísica, UNAM.
Figure (see Caption) Figure 41. Photograph of Popocatépetl's new lava dome taken on 20 August 2001. Courtesy of CENAPRED and the Secretary of Communication and Transportation.

The lava dome's volume was estimated to be slightly more than 0.5 million cubic meters. Based on the assumption that the period of dome growth coincided with the period of maximum seismicity, the rate of growth was estimated to be 7-8 m3/s; less than 5% of the rates measured in December 2000. On 13 August the dome was 190 m in diameter and 30 m tall, about 5% the size of the December 2000 dome.

On 15 August at 1545 a new episode of high seismic activity began at the volcano. This episode was similar to the 9 August episode, but more steam-and-ash emissions with higher intensities occurred on 15 August. Seismicity further increased at 1800. The entire episode was attributed to a higher rate of lava extrusion. The waveforms and amplitudes of seismic signals were similar to those recorded on 13 December 2000; however, the total seismic energy release was about 30 % of the energy released on 13 December.

Small amounts of ash from the emissions fell NW and W of the volcano in San Pedro Nexapa, Amecameca, Ozumba, Atlautla, and San Juan Tehuiztitlán. Volcanic activity decreased on 16 August around 0115. During the night incandescence was seen at the summit and at 0538 incandescent fragments were ejected more than 500 m down the volcano's N flank.

After the August 15 increase in seismicity, seismic and volcanic activity returned to normal levels, with small volcanic emissions and periods of high-frequency and low-amplitude tremor. On 9 September during 0815-1605 an episode of frequent small- to moderate-sized eruptions began at Popocatépetl. The eruptions produced steam-and-ash emissions that rose to a maximum height of 1 km above the dome and drifted to the NW. During the night a small eruption sent incandescent fragments up to 200 m from the crater. Small amounts of ash fell in Ozumba (~15 km W of the volcano) and in Yecapixtla (~25 km SW of the volcano). Aerial photographs taken on 20 September revealed that the lava dome was visible within the crater.

Geologic Background. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, rises 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major Plinian eruptions, the most recent of which took place about 800 CE, have occurred since the mid-Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since Pre-Columbian time.

Information Contacts: Carlos Valdés González, Roberto Quass Weppen, Gilberto Castelan, Enrique Guevara Ortiz, and Angel Gómez-Vázquez, Centro Nacional de Prevención de Desastres (CENAPRED), Av. Delfín Madrigal No.665. Coyoacan, México. D.F. 04360 (URL: https://www.gob.mx/cenapred/); Servando de la Cruz-Reyna, Instituto de Geofísica, UNAM. Cd. Universitaria. Circuito Institutos. Coyoácan. México, D.F. 04510 (URL: http://www.geofisica.unam.mx/); Washington VAAC, Satellite Analysis Branch (SAB), NOAA/NESDIS E/SP23, NOAA Science Center Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA (URL: http://www.ssd.noaa.gov/); NOAA Operational Significant Events Imagery Support Team (OSEI), NOAA/NESDIS, World Weather Building, Room 510, 5200 Auth Road, Camp Springs, MD 20748 USA (URL: https://www.nnvl.noaa.gov/); Secretaría de Comunicaciones y Transportes, Xola Y Avenida Universidad, Cuerpo "C",Piso 1, Col. Navarte, Del. Benito Juarez, C. P. 03028, México (URL: http://www.sct.gob.mx/); Associated Press.


Semeru (Indonesia) — August 2001 Citation iconCite this Report

Semeru

Indonesia

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

All times are local (unless otherwise noted)


Continuous seismic activity, plumes to ~11.6 km

From August 2000 through August 2001, activity at Semeru was characterized by continuous seismic activity and ash-and-steam plumes of varying heights above the summit. The Alert Level at Semeru remained at level 2 (on a scale of 1-4) throughout the report period.

The Darwin Volcanic Ash Advisory Center (VAAC) reported volcanic ash plumes and clouds on several occasions throughout the year (table 5). The plumes ranged from ~4.6 to ~11.6 km altitude, and moved mainly SSE. On 8 July at 1503 a SE-drifting ash plume rose to ~2.5 km above the volcano. Ground-based reports prior to the eruption revealed that each day during 18-24 June Semeru emitted ash to ~0.6 km above the volcano.

Table 5. Summary of Volcanic Ash Advisories from the Darwin VAAC issued between August 2000 and August 2001. Note that heights are given in altitude. Semeru's summit lies at 3,767 m above sea level. Information sources include air reports (for example, routed via airlines, AIREPS), pilot reports (PIREPS), satellite data, and reports from ground observations), and information from the Meteorological and Geophysical Agency of Indonesia. Source date was provided by the Darwin VAAC.

Date Time Source Comment
19 Aug 2000 0653 PIREPS Possible smoke plume observed extending to ~10.6 km and moving S to SE.
19 Aug 2000 0812 PIREPS Possible smoke plume extending to ~4.6 km.
20 Aug 2000 0944 AIREP Smoke plume observed extending to ~7.3 km.
21 Aug 2000 0938 AIREP Smoke plume observed extending to ~7.3 km.
14 Sep 2000 1135 AIREP Stationary smoke plume at ~6 km.
10 Oct 2000 0333 AIREP Volcanic ash cloud at ~6 km and ascending.
10 Oct 2000 0433 AIREP Volcanic ash cloud at ~6 km and ascending.
10 Oct 2000 1030 AIREP Volcanic ash cloud at ~6 km and ascending.
11 Oct 2000 0216 AIREP Volcanic ash cloud at ~6 km and ascending.
11 Oct 2000 0435 AIREP Volcanic ash cloud at ~6 km, intermittent discharge extending to a maximum of 30 NM.
11 Oct 2000 0528 AIREP Volcanic ash cloud at ~6 km, intermittent discharge extending to a maximum of 30 NM.
11 Oct 2000 0925 AIREP Volcanic ash cloud at ~6 km, intermittent discharge extending to a maximum of 30 NM.
13 Oct 2000 0426 AIREP Volcanic ash cloud at ~6 to ~7.6 km drifting SW.
27 Oct 2000 0215 AIREP Volcanic ash cloud at ~7.6 km lasting for ~10 minutes.
30 Oct 2000 1055 AIREP Volcanic ash cloud at ~6 km.
11 Dec 2000 0508 AIREP Volcanic ash to ~7.6 km.
08 Jul 2001 0929 AIREP Ash plume reported to ~6 km drifting SE.
09 Jul 2001 0857 AIREP Ash plume to ~6 km drifting SE.
09 Jul 2001 2355 AIREP Volcanic ash at ~11.6 km.
09 Jul 2001 0857 AIREP Ash plume reported to ~6 km drifting SE.

Explosion earthquakes dominated the seismicity (table 6), and pyroclastic flows occurred 17 times between 31 July 2000 and 15 July 2001. The Volcanological Survey of Indonesia (VSI) reported that a significant change in seismic activity occurred during 3-9 October 2000, when the number of explosion earthquakes increased to more than 700. A pyroclastic flow that reached the Kembar Besuki river, as far as 2,500 m from the summit, occurred on 2 October.

Table 6. Summary of seismicity at Semeru, 31 July 2000-15 July 2001. Ash plume heights are distances above the summit unless otherwise noted. Courtesy of the Volcanic Survey of Indonesia (VSI).

Date Deep Volcanic (A-type) Shallow Volcanic (B-type) Explosion Avalanche Tectonic Comment
31 Jul-07 Aug 2000 4 5 657 64 22 Five pyroclastic flows. Five pyroclastic-flow earthquakes. Four tremor events.
08 Aug-14 Aug 2000 5 4 584 43 13 Two pyroclastic flows; ash plume ~600 m. Two tremor events.
15 Aug-21 Aug 2000 2 -- 420 17 5 Ash plume ~600 m.
22 Aug-29 Aug 2000 23 1 542 27 21 Ash plume ~600 m. Three pyroclastic-flow earthquakes.
29 Aug-04 Sep 2000 23 1 542 27 21 Ash cloud ~600 m. Three pyroclastic-flow earthquakes.
05 Sep-11 Sep 2000 -- 2 594 8 -- Ashfall (105 events); white cloud to ~700 m.
12 Sep-18 Sep 2000 -- -- 623 -- -- Three pyroclastic flows; ashfall (72 events); ash plume to ~600 m. Two tremor events.
19 Sep-25 Sep 2000 -- 3 556 98 16 Ash plume to ~600 m.
26 Sep-02 Oct 2000 2 2 582 19 1 Thin white ash plume. One pyroclastic-flow earthquake. 79 tremor events.
03 Oct-09 Oct 2000 1 1 707 80 14 One pyroclastic flow.
10 Oct-16 Oct 2000 1 3 592 41 13 One pyroclastic flow; ash plume to ~600 m.
17 Oct-23 Oct 2000 3 -- 607 25 -- --
24 Oct-30 Oct 2000 42 1 592 22 7 Volcano covered by haze. Four tremor events.
31 Oct-06 Nov 2000 16 1 561 48 13 Ash plume to ~600 m.
28 Nov-04 Dec 2000 8 -- 483 24 2 Thick white fume 600 m above Jonggring Seloko crater.
05 Dec-11 Dec 2000 1 1 513 16 6 Two pyroclastic flows; thick white fume 600 m above Jonggring Seloko crater.
12 Dec-18 Dec 2000 2 -- 598 38 5 Volcano covered by smog.
19 Dec-25 Dec 2000 -- 1 319 22 2 --
26 Dec-01 Jan 2001 1 -- 559 98 7 White-gray ash plume to 600 m.
02 Jan-08 Jan 2001 6 -- 579 80 10 --
09 Feb-15 Feb 2001 29 1 693 80 4 --
13 Feb-19 Feb 2001 1 -- 519 29 1 No visual observations because of cloudy weather.
20 Feb-26 Feb 2001 3 -- 702 58 5 White-thin plume to ~100 m.
27 Feb-05 Mar 2001 -- -- 249 27 2 White-gray plumes to ~600 m.
06 Mar-12 Mar 2001 6 -- 303 31 -- --
12 Mar-18 Mar 2001 4 -- 349 10 3 --
19 Mar-23 Mar 2001 2 -- 259 -- 1 --
02 Apr-09 Apr 2001 28 -- 305 248 3 --
09 Apr-15 Apr 2001 -- -- 339 51 3 --
16 Apr-22 Apr 2001 -- -- 550 -- -- --
23 Apr-29 Apr 2001 12 1 759 157 4 --
30 Apr-06 May 2001 -- -- 782 96 7 --
07 May-13 May 2001 2 -- 670 113 7 --
14 May-20 May 2001 1 -- 616 143 2 --
28 May-03 Jun 2001 -- -- 396 115 3 --
04 Jun-10 Jun 2001 3 -- 430 75 5 --
11 Jun-17 Jun 2001 2 -- 361 81 4 --
18 Jun-24 Jun 2001 8 -- 346 62 3 --
25 Jun-01 Jul 2001 2 -- 331 37 2 --
02 Jul-08 Jul 2001 -- -- 299 30 6 --
09 Jul-15 Jul 2001 -- -- 687 57 11 --

During 27 March-1 April 2001, VSI personnel observed several lava avalanches that traveled to Kembar River valley as far as 750 m S of the summit. No seismic data were available because the seismometers broke on 24 March 2001. They were repaired on 1 April.

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

Information Contacts: Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/).


Sheveluch (Russia) — August 2001 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Eruption on 15 July, pyroclastic flows and explosion on 23 August 2001

During 14-16 July 2001, spasmodic volcanic tremor increased several times. On 15 July at 1803 a three-pixel anomaly was visible on AVHRR satellite imagery near the SW flank of the volcano and at 2100 a gas-and-steam plume was observed rising to 1.5 km above the dome. A moderate-sized eruption took place on 19 July at 1033. KVERT raised the level of concern from Yellow (volcano is restless; eruption may occur) to Orange (volcano is in eruption or eruption may occur at any time). The eruption produced an ash plume that rose 3 km above the lava dome.

After the eruption through 15 August, seismic activity remained above background levels, with many small earthquakes occurring within the volcano's edifice and many different seismic signals (explosion, avalanche, collapse) recorded locally. Gas-and-steam plumes rose from the summit level to ~2 km above the dome. One- to three-pixel anomalies were occasionally visible on AVHRR imagery near the SW flank of the volcano. The level of continuous spasmodic volcanic tremor increased on 28 and 30 July. On the night of 1 August ash fell in the town of Klyuchi, 46 km S of the volcano. On 11 August several thermal anomalies were recorded on satellite imagery, as well as a gas-and-steam plume that extended 75 km SE. On 15 August volcanic tremor decreased gradually to background levels, but increased again soon after. Pyroclastic flows traveled down the flanks of the volcano following an explosion on 23 August. The volcano remained at concern level Orange throughout August.

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: Olga Chubarova, Kamchatka Volcanic Eruptions Response Team (KVERT); Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia; Alaska Volcano Observatory (AVO), a cooperative program of a) U.S. Geological Survey, 4200 University Drive, Anchorage, AK 99508-4667, USA (URL: http://www.avo.alaska.edu/), b) Geophysical Institute, University of Alaska, PO Box 757320, Fairbanks, AK 99775-7320, USA, and c) Alaska Division of Geological & Geophysical Surveys, 794 University Ave., Suite 200, Fairbanks, AK 99709, USA; Anchorage Volcanic Ash Advisory Center (VAAC), NOAA Alaska Aviation Weather Unit, 6930 Sand Lake Road, Anchorage, AK 99502-1845, USA (URL: http://vaac.arh.noaa.gov/); Tokyo Volcanic Ash Advisory Center, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/).

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/).