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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

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

Sabancaya (Peru) Explosions, ash and SO2 plumes, thermal anomalies, and lava dome growth during June-November 2019

Karangetang (Indonesia) Lava flows, strong thermal anomalies, gas-and-steam emissions, and ash plumes during May-November 2019

Ulawun (Papua New Guinea) New vent, lava fountaining, lava flow, and ash plumes in late September-October 2019

Nyamuragira (DR Congo) Strong thermal anomalies and fumaroles within the summit crater during June-November 2019

Bagana (Papua New Guinea) Intermittent gas-and-steam emissions and thermal anomalies during June-November 2019

Kerinci (Indonesia) Intermittent gas-and-steam and ash plumes during June-early November 2019

Bezymianny (Russia) Lava dome growth, ongoing thermal anomalies, moderate gas-steam emissions, June-November 2019

Mayon (Philippines) Gas-and-steam plumes and summit incandescence during May-October 2019

Merapi (Indonesia) Low-volume dome growth continues during April-September 2019 with rockfalls and small block-and-ash flows



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).


Sabancaya (Peru) — December 2019 Citation iconCite this Report

Sabancaya

Peru

15.787°S, 71.857°W; summit elev. 5960 m

All times are local (unless otherwise noted)


Explosions, ash and SO2 plumes, thermal anomalies, and lava dome growth during June-November 2019

Sabancaya is an andesitic stratovolcano located in Peru. The most recent eruptive episode began in early November 2016, which is characterized by gas-and-steam and ash emissions, seismicity, and explosive events (BGVN 44:06). The ash plumes are dispersed by wind with a typical radius of 30 km, which occasionally results in ashfall. Current volcanism includes high seismicity, gas-and-steam emissions, ash and SO2 plumes, numerous thermal anomalies, and explosive events. This report updates information from June through November 2019 using information primarily from the Instituto Geofisico del Peru (IGP) and Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico) (OVI-INGEMMET).

Table 5. Summary of eruptive activity at Sabancaya during June-November 2019 based on IGP weekly reports, the Buenos Aires VAAC advisories, the HIGP MODVOLC hotspot monitoring algorithm, and Sentinel-5P/TROPOMI satellite data.

Month Avg. Daily Explosions by week Max plume Heights (km above crater) Plume drift MODVOLC Alerts Min Days with SO2 over 2 DU
Jun 2019 12, 13, 16, 17 2.6-3.8 30 km S, SW, E, SE, NW, NE 15 20
Jul 2019 23, 22, 16, 13 2.3-3.7 E, SE, S, NE 7 25
Aug 2019 12, 30, 25, 26 2-4.5 30 km NW, W S, NE, SE, SW 7 25
Sep 2019 29, 32, 24, 15 1.5-2.5 S, SE, E, W, NW, SW 14 26
Oct 2019 32, 36, 44, 48, 28 2.5-3.5 S, SE, SW, W 11 25
Nov 2019 58, 50, 47, 17 2-4 W, SW, S, NE, E 13 22

Explosions, ash emissions, thermal signatures, and high concentrations of SO2 were reported each week during June-November 2019 by IGP, the Buenos Aires Volcanic Ash Advisory Centre (VAAC), HIGP MODVOLC, and Sentinel-2 and Sentinel-5P/TROPOMI satellite data (table 5). Thermal anomalies were visible in the summit crater, even in the presence of meteoric clouds and ash plumes were occasionally visible rising from the summit in clear weather (figure 68). The maximum plume height reached 4.5 km above the crater drifting NW, W, and S the week of 29 July-4 August, according to IGP who used surveillance cameras to visually monitor the plume (figure 69). This ash plume had a radius of 30 km, which resulted in ashfall in Colca (NW) and Huambo (W). On 27 July the SO2 levels reached a high of 12,814 tons/day, according to INGEMMET. An average of 58 daily explosions occurred in early November, which is the largest average of this reporting period.

Figure (see Caption) Figure 68. Sentinel-2 satellite imagery detected ash plumes, gas-and-steam emissions, and multiple thermal signatures (bright yellow-orange) in the crater at Sabancaya during June-November 2019. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 69. A webcam image of an ash plume rising from Sabancaya on 1 August 2019 at least 4 km above the crater. Courtesy of IGP.

Seismicity was also particularly high between August and September 2019, according to INGEMMET. On 14 August, roughly 850 earthquakes were detected. There were 280 earthquakes reported on 15 September, located 6 km NE of the crater. Both seismic events were characterized as seismic swarms. Seismicity decreased afterward but continued through the reporting period.

In February 2017, a lava dome was established inside the crater. Since then, it has been growing slowly, filling the N area of the crater and producing thermal anomalies. On 26 October 2019, OVI-INGEMMET conducted a drone overflight and captured video of the lava dome (figure 70). According to IGP, this lava dome is approximately 4.6 million cubic meters with a growth rate of 0.05 m3/s.

Figure (see Caption) Figure 70. Drone images of the lava dome and degassing inside the crater at Sabancaya on 26 (top) and 27 (bottom) October 2019. Courtesy of INGEMMET (Informe Ténico No A6969).

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows strong, consistent thermal anomalies occurring all throughout June through November 2019 (figure 71). In conjunction with these thermal anomalies, the October 2019 special issue report by INGEMMET showed new hotspots forming along the crater rim in July 2018 and August 2019 (figure 72).

Figure (see Caption) Figure 71. Thermal anomalies at Sabancaya for 3 January through November 2019 as recorded by the MIROVA system (Log Radiative Power) were frequent, strong, and consistent. Courtesy of MIROVA.
Figure (see Caption) Figure 72. Thermal hotspots on the NW section of the crater at Sabancaya using MIROVA images. These images show the progression of the formation of at least two new hotspots between February 2017 to August 2019. Courtesy of INGEMMET, Informe Técnico No A6969.

Sulfur dioxide emissions also persisted at significant levels from June through November 2019, as detected by Sentinel-5P/TROPOMI satellite data (figure 73). The satellite measurements of the SO2 emissions exceeded 2 DU (Dobson Units) at least 20 days each month during this time. These SO2 plumes sometimes occurred for multiple consecutive days (figure 74).

Figure (see Caption) Figure 73. Consistent, large SO2 plumes from Sabancaya were seen in TROPOMI instrument satellite data throughout June-November 2019, many of which drifted in different directions based on the prevailing winds. Courtesy of NASA Goddard Space Flight Center.
Figure (see Caption) Figure 74. Persistent SO2 plumes from Sabancaya appeared daily during 13-16 September 2019 in the TROPOMI instrument satellite data. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Information Contacts: Instituto Geofisico del Peru (IGP), Calle Badajoz N° 169 Urb. Mayorazgo IV Etapa, Ate, Lima 15012, Perú (URL: https://www.gob.pe/igp); Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa, Peru (URL: http://ovi.ingemmet.gob.pe); 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/); 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/); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Karangetang (Indonesia) — December 2019 Citation iconCite this Report

Karangetang

Indonesia

2.781°N, 125.407°E; summit elev. 1797 m

All times are local (unless otherwise noted)


Lava flows, strong thermal anomalies, gas-and-steam emissions, and ash plumes during May-November 2019

Karangetang (also known as Api Siau), located on the island of Siau in the Sitaro Regency, North Sulawesi, Indonesia, has experienced more than 40 recorded eruptions since 1675 in addition to many smaller undocumented eruptions. In early February 2019, a lava flow originated from the N crater (Kawah Dua) traveling NNW and reaching a distance over 3 km. Recent monitoring showed a lava flow from the S crater (Kawah Utama, also considered the "Main Crater") traveling toward the Kahetang and Batuawang River drainages on 15 April 2019. Gas-and-steam emissions, ash plumes, moderate seismicity, and thermal anomalies including lava flow activity define this current reporting period for May through November 2019. The primary source of information for this report comes from daily and weekly reports by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM, or the Center of Volcanology and Geological Hazard Mitigation), the Darwin Volcanic Ash Advisory Center (VAAC), and satellite data.

PVMBG reported that white gas-and-steam emissions were visible rising above both craters consistently between May through November 2019 (figures 30 and 31). The maximum altitude for these emissions was 400 m above the Dua Crater on 27 May and 700 m above the Main Crater on 12 June. Throughout the reporting period PVMBG noted that moderate seismicity occurred, which included both shallow and deep volcanic earthquakes.

Figure (see Caption) Figure 30. A Sentinel-2 image of Karangetang showing two active craters producing gas-and-steam emissions with a small amount of ash on 7 August 2019. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 31. Webcam images of gas-and-steam emissions rising from the summit of Karangetang on 14 (top) and 25 (bottom) October 2019. Courtesy of PVMBG via Øystein Lund Andersen.

Activity was relatively low between May and June 2019, consisting mostly of gas-and-steam emissions. On 26-27 May 2019 crater incandescence was observed above the Main Crater; white gas-and-steam emissions were rising from both craters (figures 32 and 33). At 1858 on 20 July, incandescent avalanches of material originating from the Main Crater traveled as far as 1 km W toward the Pangi and Kinali River drainages. By 22 July the incandescent material had traveled another 500 m in the same direction as well as 1 km in the direction of the Nanitu and Beha River drainages. According to a Darwin VAAC report, discreet, intermittent ash eruptions on 30 July resulted in plumes drifting W at 7.6 km altitude and SE at 3 km, as observed in HIMAWARI-8 satellite imagery.

Figure (see Caption) Figure 32. Photograph of summit crater incandescence at Karangetang on 12 May 2019. Courtesy of Dominik Derek.
Figure (see Caption) Figure 33. Photograph of both summit crater incandescence at Karangetang on 12 May 2019 accompanied by gas-and-steam emissions. Courtesy of Dominik Derek.

On 5 August 2019 a minor eruption produced an ash cloud that rose 3 km and drifted E. PVMBG reported in the weekly report for 5-11 August that an incandescent lava flow from the Main Crater was traveling W and SW on the slopes of Karangetang and producing incandescent avalanches (figure 34). During 12 August through 1 September lava continued to effuse from both the Main and Dua craters. Avalanches of material traveled as far as 1.5 km SW toward the Nanitu and Pangi River drainages, 1.4-2 km to the W of Pangi, and 1.8 km down the Sense River drainage. Lava fountaining was observed occurring up to 10 m above the summit on 14-20 August.

Figure (see Caption) Figure 34. Photograph of summit crater incandescence and a lava flow from Karangetang on 7 August 2019. Courtesy of MAGMA Indonesia.

PVMBG reported that during 2-22 September lava continued to effuse from both craters, traveling SW toward the Nanitu, Pangi, and Sense River drainages as far as 1.5 km. On 24 September the lava flow occasionally traveled 0.8-1.5 km toward the West Beha River drainage. The lava flow from the Main Crater continued through at least the end of November, moving SW and W as far as 1.5 km toward the Nanitu, Pangi, and Sense River drainages. In late October and onwards, incandescence from both summit craters was observed at night. The lava flow often traveled as far as 1 km toward the Batang and East Beha River drainage on 12 November, the West Beha River drainage on 15, 22, 24, and 29 November, and the Batang and West Beha River drainages on 25-27 November (figure 35). On 30 November a Strombolian eruption occurred in the Main Crater accompanied by gas-and-steam emissions rising 100 m above the Main Crater and 50 m above the Dua Crater. Lava flows traveled SW and W toward the Nanitu, Sense, and Pangi River drainages as far as 1.5 km, the West Beha and Batang River drainages as far as 1 km, and occasionally the Batu Awang and Kahetang River drainages as far as 2 km. Lava fountaining was reported occurring 10-25 m above the Main Crater and 10 m above the Dua Crater on 6, 8-12, 15, 21-30 November.

Figure (see Caption) Figure 35. Webcam image of gas-and-steam emissions rising from the summit of Karangetang accompanied by incandescence and lava flows at night on 27 November 2019. Courtesy of MAGMA Indonesia via Øystein Lund Andersen.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed consistent and strong thermal anomalies within 5 km of the summit craters from late July through November 2019 (figure 36). Satellite imagery from Sentinel-2 corroborated this data, showing strong thermal anomalies and lava flows originating from both craters during this same timeframe (figure 37). In addition to these lava flows, satellite imagery also captured intermittent gas-and-steam emissions from May through November (figure 38). MODVOLC thermal alerts registered 165 thermal hotspots near Karangetang's summit between May and November.

Figure (see Caption) Figure 36. Frequent and strong thermal anomalies at Karangetang between 3 January through November 2019 as recorded by the MIROVA system (Log Radiative Power) began in late July and were recorded within 5 km of the summit craters. Courtesy of MIROVA.
Figure (see Caption) Figure 37. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) confirmed ongoing thermal activity (bright orange) at Karangetang from July into November 2019. The lava flows traveled dominantly in the W direction from the Main Crater. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 38. Sentinel-2 satellite imagery showing gas-and-steam emissions with a small amount of ash (middle and right) rising from both craters of Karangetang during May through November 2019. Courtesy of Sentinel Hub Playground.

Sentinel-5P/TROPOMI satellite data detected multiple sulfur dioxide plumes between May and November 2019 (figure 39). These emissions occasionally exceeded 2 Dobson Units (DU) and drifted in different directions based on the dominant wind pattern.

Figure (see Caption) Figure 39. SO2 emissions from Karangetang (indicated by the red box) were seen in TROPOMI instrument satellite data during May through November 2019, many of which drifted in different directions based on the prevailing winds. Top left: 27 May 2019. Top middle: 26 July 2019. Top right: 17 August 2019. Bottom left: 27 September 2019. Bottom middle: 3 October 2019. Bottom right: 21 November 2019. Courtesy of NASA Goddard Space Flight Center.

Geologic Background. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, about 125 km NNE of the NE-most point of Sulawesi island. The stratovolcano contains five summit craters along a N-S line. It is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts have produced pyroclastic flows.

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/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); 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); Øystein Lund Andersen (Twitter: @OysteinLAnderse, https://twitter.com/OysteinLAnderse, URL: https://www.oysteinlundandersen.com); Dominik Derek (URL: https://www.facebook.com/07dominikderek/).


Ulawun (Papua New Guinea) — December 2019 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


New vent, lava fountaining, lava flow, and ash plumes in late September-October 2019

Ulawun is a basaltic-to-andesitic stratovolcano located in West New Britain, Papua New Guinea, with typical activity consisting of seismicity, gas-and-steam plumes, and ash emissions. The most recent eruption began in late June 2019 involving ash and gas-and-steam emissions, increased seismicity, and a pyroclastic flow (BGVN 44:09). This report includes volcanism from September to October 2019 with primary source information from the Rabaul Volcano Observatory (RVO) and the Darwin Volcanic Ash Advisory Centre (VAAC).

Activity remained low through 26 September 2019, mainly consisting of variable amounts of gas-and-steam emissions and low seismicity. Between 26 and 29 September RVO reported that the seismicity increased slightly and included low-level volcanic tremors and Real-Time Seismic Amplitude Measurement (RSAM) values in the 200-400 range on 19, 20, and 22 September. On 30 September small volcanic earthquakes began around 1000 and continued to increase in frequency; by 1220, they were characterized as a seismic swarm. The Darwin VAAC advisory noted that an ash plume rose to 4.6-6 km altitude, drifting SW and W, based on ground reports.

On 1 October 2019 the seismicity increased, reaching RSAM values up to 10,000 units between 0130 and 0200, according to RVO. These events preceded an eruption which originated from a new vent that opened on the SW flank at 700 m elevation, about three-quarters of the way down the flank from the summit. The eruption started between 0430 and 0500 and was defined by incandescence and lava fountaining to less than 100 m. In addition to lava fountaining, light- to dark-gray ash plumes were visible rising several kilometers above the vent and drifting NW and W (figure 21). On 2 October, as the lava fountaining continued, ash-and-steam plumes rose to variable heights between 2 and 5.2 km (figures 22 and 23), resulting in ashfall to the W in Navo. Seismicity remained high, with RSAM values passing 12,000. A lava flow also emerged during the night which traveled 1-2 km NW. The main summit crater produced white gas-and-steam emissions, but no incandescence or other signs of activity were observed.

Figure (see Caption) Figure 21. Photographs of incandescence and lava fountaining from Ulawun during 1-2 October 2019. A) Lava fountains along with ash plumes that rose several kilometers above the vent. B) Incandescence and lava fountaining seen from offshore. Courtesy of Christopher Lagisa.
Figure (see Caption) Figure 22. Photographs of an ash plume rising from Ulawun on 1 October 2019. In the right photo, lava fountaining is visible. Courtesy of Christopher Lagisa.
Figure (see Caption) Figure 23. Photograph of lava fountaining and an ash plume rising from Ulawun on 1 October 2019. Courtesy of Joe Metto, WNB Provincial Disaster Office (RVO Report 2019100101).

Ash emissions began to decrease by 3 October 2019; satellite imagery and ground observations showed an ash cloud rising to 3 km altitude and drifting N, according to the Darwin VAAC report. RVO reported that the fissure eruption on the SW flank stopped on 4 October, but gas-and-steam emissions and weak incandescence were still visible. The lava flow slowed, advancing 3-5 m/day, while declining seismicity was reflected in RSAM values fluctuating around 1,000. RVO reported that between 23 and 31 October the main summit crater continued to produce variable amounts of white gas-and-steam emissions (figure 24) and that no incandescence was observed after 5 October. Gas-and-steam emissions were also observed around the new SW vent and along the lava flow. Seismicity remained low until 27-29 October; it increased again and peaked on 30 October, reaching an RSAM value of 1,700 before dropping and fluctuating around 1,200-1,500.

Figure (see Caption) Figure 24. Webcam photo of a gas-and-steam plume rising from Ulawun on 30 October 2019. Courtesy of the Rabaul Volcano Observatory (RVO).

In addition to ash plumes, SO2 plumes were also detected between September and October 2019. Sentinel-5P/TROPOMI data showed SO2 plumes, some of which exceeded 2 Dobson Units (DU) drifting in different directions (figure 25). MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed strong, frequent thermal anomalies within 5 km of the summit beginning in early October 2019 and throughout the rest of the month (figure 26). Only one thermal anomaly was detected in early December.

Figure (see Caption) Figure 25. Sentinel-5P/TROPOMI data showing a high concentration of SO2 plumes rising from Ulawun between late September-early October 2019. Top left: 11 September 2019. Top right: 1 October 2019. Bottom left: 2 October 2019. Bottom right: 3 October 2019. Courtesy of the NASA Space Goddard Flight Center.
Figure (see Caption) Figure 26. Frequent and strong thermal anomalies at Ulawun for February through December 2019 as recorded by the MIROVA system (Log Radiative Power) began in early October and continued throughout the month. Courtesy of MIROVA.

Activity in November was relatively low, with only a variable amount of white gas-and-steam emissions visible and low (less than 200 RSAM units) seismicity with sporadic volcanic earthquakes. Between 9-22 December, a webcam showed intermittent white gas-and-steam emissions were observed at the main crater, accompanied by some incandescence at night. Some gas-and-steam emissions were also observed rising from the new SW vent along the lava flow.

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

Information Contacts: Rabaul Volcano Observatory (RVO), Geohazards Management Division, Department of Mineral Policy and Geohazards Management (DMPGM), PO Box 3386, Kokopo, East New Britain Province, Papua New Guinea; Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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/); Christopher Lagisa, West New Britain Province, Papua New Guinea (URL: https://www.facebook.com/christopher.lagisa, images posted at https://www.facebook.com/christopher.lagisa/posts/730662937360239 and https://www.facebook.com/christopher.lagisa/posts/730215604071639).


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

Nyamuragira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


Strong thermal anomalies and fumaroles within the summit crater during June-November 2019

Nyamuragira (also known as Nyamulagira) is a high-potassium basaltic shield volcano located in the Virunga Volcanic Province (VVP) in the Democratic Republic of the Congo. Previous volcanism consisted of the reappearance of a lava lake in the summit crater in mid-April 2018, lava emissions, and high seismicity (BGVN 44:05). Current activity includes strong thermal signatures, continued inner crater wall collapses, and continued moderate seismicity. The primary source of information for this June-November 2019 report comes from the Observatoire Volcanologique de Goma (OVG) and satellite data and imagery from multiple sources.

OVG reported in the July 2019 monthly that the inner crater wall collapses that were observed in May continued to occur. During this month, there was a sharp decrease in the lava lake level, and it is no longer visible. However, the report stated that lava fountaining was visible from a small cone within this crater, though its activity has also decreased since 2014. In late July, a thermal anomaly and fumaroles were observed originating from this cone (figure 85). Seismicity remained moderate throughout this reporting period.

Figure (see Caption) Figure 85. Photograph showing the small active cone within the crater of Nyamuragira in late July 2019. Fumaroles are also observed within the crater originating from the small cone. Courtesy of Sergio Maguna.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows strong, frequent thermal anomalies within 5 km of the summit between June through November (figure 86). The strength of these thermal anomalies noticeably decreases briefly in September. MODVOLC thermal alerts registered 54 thermal hotspots dominantly near the N area of the crater during June through November 2019. Satellite imagery from Sentinel-2 corroborated this data, showing strong thermal anomalies within the summit crater during this same timeframe (figure 87).

Figure (see Caption) Figure 86. The MIROVA graph of thermal activity (log radiative power) at Nyamuragira during 30 January through November 2019 shows strong, frequent thermal anomalies through November with a brief decrease in activity in late April-early May and early September. Courtesy of MIROVA.
Figure (see Caption) Figure 87. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) confirmed ongoing thermal activity at Nyamuragira into November 2019. Courtesy of Sentinel Hub Playground.

Geologic Background. Africa's most active volcano, Nyamuragira, is a massive high-potassium basaltic shield about 25 km N of Lake Kivu. Also known as Nyamulagira, it has generated extensive lava flows that cover 1500 km2 of the western branch of the East African Rift. The broad low-angle shield volcano contrasts dramatically with the adjacent steep-sided Nyiragongo to the SW. The summit is truncated by a small 2 x 2.3 km caldera that has walls up to about 100 m high. Historical eruptions have occurred within the summit caldera, as well as from the numerous fissures and cinder cones on the flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938, at the time of a major flank eruption. Historical lava flows extend down the flanks more than 30 km from the summit, reaching as far as Lake Kivu.

Information Contacts: Observatoire Volcanologique de Goma (OVG), Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sergio Maguna (Facebook: https://www.facebook.com/sergio.maguna.9, images posted at https://www.facebook.com/sergio.maguna.9/posts/1267625096730837).


Bagana (Papua New Guinea) — December 2019 Citation iconCite this Report

Bagana

Papua New Guinea

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

All times are local (unless otherwise noted)


Intermittent gas-and-steam emissions and thermal anomalies during June-November 2019

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

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

Figure (see Caption) Figure 38. Thermal anomalies near the crater summit at Bagana during February-November 2019 as recorded by the MIROVA system (Log Radiative Power) increased in frequency and power in early August. A small cluster was detected in early October after a brief pause in activity in early September. Courtesy of MIROVA.
Figure (see Caption) Figure 39. Sentinel-2 thermal satellite imagery showing small thermal anomalies at Bagana between July-August 2019. Left: A very faint thermal anomaly and a gas-and-steam plume is seen on 7 July 2019. Right: Two small thermal anomalies are faintly seen on 6 August 2019. Both Sentinel-2 satellite images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 40. A gas-and-steam plume rising from the summit of Bagana on 18 September 2019. Courtesy of Brendan McCormick Kilbride (University of Manchester).

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

Figure (see Caption) Figure 41. Degassing plumes seen from drone footage 100 m above the summit of Bagana. Top: Zoomed out view of the summit of Bagana degassing. Bottom: Closer perspective of the gases emitted from Bagana. Courtesy of Kieran Wood (University of Bristol) and the Bristol Flight Laboratory.
Figure (see Caption) Figure 42. Photos of gas-and-steam plumes rising from Bagana between 14-19 September 2019. Courtesy of Brendan McCormick Kilbride (University of Manchester).

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

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


Kerinci (Indonesia) — December 2019 Citation iconCite this Report

Kerinci

Indonesia

1.697°S, 101.264°E; summit elev. 3800 m

All times are local (unless otherwise noted)


Intermittent gas-and-steam and ash plumes during June-early November 2019

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

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

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

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

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

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

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Bezymianny (Russia) — December 2019 Citation iconCite this Report

Bezymianny

Russia

55.972°N, 160.595°E; summit elev. 2882 m

All times are local (unless otherwise noted)


Lava dome growth, ongoing thermal anomalies, moderate gas-steam emissions, June-November 2019

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

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

Figure (see Caption) Figure 32. Photo of Bezymianny showing fumarolic activity on 4 July 2019. Photo by O. Girina (IVS FEB RAS, KVERT); courtesy of KVERT.
Figure (see Caption) Figure 33. Typical infrared satellite images of Bezymianny showing thermal anomalies in the summit crater, including a lava flow to the WNW. Top: 21 August 2019 with SWIR filter (bands 12, 8A, 4). Bottom: 17 September 2019 with Atmospheric Penetration filter (bands 12, 11, 8A). Courtesy of Sentinel Hub Playground.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Mayon (Philippines) — November 2019 Citation iconCite this Report

Mayon

Philippines

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

All times are local (unless otherwise noted)


Gas-and-steam plumes and summit incandescence during May-October 2019

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

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

Figure (see Caption) Figure 49. Sentinel-2 thermal satellite imagery of Mayon between May-October 2019. Small thermal anomalies were recorded in satellite imagery from the summit and some white gas-and-steam plumes are visible. Top left: 30 May 2019. Top right: 9 June 2019. Bottom left: 22 September 2019. Bottom right: 12 October 2019. Sentinel-2 satellite images with "Atmospheric penetration" (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 50. Small SO2 plumes rising from Mayon during May-September 2019 recorded in DU (Dobson Units). Top left: 28 May 2019. Top right: 26 July 2019. Bottom left: 16 August 2019. Bottom right: 23 September 2019. Courtesy of NASA Goddard Space Flight Center.

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

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

Information Contacts: Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, University of the Philippines Campus, Diliman, Quezon City, Philippines (URL: http://www.phivolcs.dost.gov.ph/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://SO2.gsfc.nasa.gov/).


Merapi (Indonesia) — October 2019 Citation iconCite this Report

Merapi

Indonesia

7.54°S, 110.446°E; summit elev. 2910 m

All times are local (unless otherwise noted)


Low-volume dome growth continues during April-September 2019 with rockfalls and small block-and-ash flows

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

Figure (see Caption) Figure 79. Merapi volcano is located north of Yogyakarta in Central Java. Photo courtesy of Øystein Lund Andersen.
Figure (see Caption) Figure 80. A view of the Gendol drainage where avalanches and block-and-ash flows are channeled from the active Merapi lava dome. The Gendol drainage is approximately 400 m wide at the summit. Courtesy of Brett Carr, Lamont-Doherty Earth Observatory.

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

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

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

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

Figure (see Caption) Figure 82. The development of the Merapi summit dome from 2 June 2018 to 17 June 2019. Courtesy of Øystein Lund Andersen.
Figure (see Caption) Figure 83. Photos taken of the Merapi summit lava dome in June 2019. Top: This nighttime time-lapse photograph shows incandescence at the south-facing side of the dome on the 16 June. Middle: A closeup of a small rockfall from the dome on 17 June. Bottom: A gas plume accompanying a small rockfall on 17 June. Courtesy of Øystein Lund Andersen.
Figure (see Caption) Figure 84. Blocks from an incandescent rockfall off the Merapi dome reached out to 1 km down the Gendol drainage on 26 June 2019. Courtesy of MAGMA Indonesia.

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

Figure (see Caption) Figure 85. The Merapi dome on 30 July 2019 producing a weak plume. Courtesy of MAGMA Indonesia.
Figure (see Caption) Figure 86. Incandescent rocks from the hot lava dome at the summit of Merapi form rockfalls down the Gendol drainage on 14 July 2019. Courtesy of Øystein Lund Andersen.

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

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

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

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

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

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

Geologic Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. It is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the western-to-southern flanks and caused many fatalities during historical time.

Information Contacts: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), Center for Research and Development of Geological Disaster Technology (URL: http://merapi.bgl.esdm.go.id/, Twitter: @BPPTKG); Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/, Twitter: https://twitter.com/BNPB_Indonesia); Øystein Lund Andersen? (Twitter: @OysteinLAnderse, URL: http://www.oysteinlundandersen.com); Sutopo Purwo Nugroho, BNPB (Twitter: @Sutopo_PN, URL: https://twitter.com/Sutopo_PN); Brett Carr, Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY, USA (URL: https://www.ldeo.columbia.edu/user/bcarr).

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Bulletin of the Global Volcanism Network - Volume 22, Number 03 (March 1997)

Managing Editor: Richard Wunderman

Arenal (Costa Rica)

Explosions diminished in January but continued through March

Atmospheric Effects (1995-2001) (Unknown)

Lidar data from Cuba, Hawaii, and Virginia

Callaqui (Chile)

Continuous fumarolic activity at main vent and upper S flank

Copahue (Chile-Argentina)

Crater lake lies several meters below drainage notch

Jan Mayen (Norway)

Weak fumaroles on the inner NE crater wall

Karymsky (Russia)

Ash plumes reported by aircraft pilot

Kilauea (United States)

Lava flows outside of Pu`u `O`o for the first time since 31 January

Klyuchevskoy (Russia)

Continuous presence of gas-and-steam plume up to 4 km above crater

Llaima (Chile)

Fumarolic activity at summit vent

Lonquimay (Chile)

1988-89 lava flows continue emitting steam

Manam (Papua New Guinea)

Activity low with increase near the end of the month

Masaya (Nicaragua)

Strombolian explosion; incandescent vent in Santiago crater; seismicity increases

Okmok (United States)

Emission of steam, ash, and lava continues

Pacaya (Guatemala)

Graduate students study gas emission and lava flow

Platanar (Costa Rica)

Dormancy continues but S-flank residents felt six earthquakes on 30 March

Poas (Costa Rica)

Relatively stable but seismically active

Popocatepetl (Mexico)

Summaries for March and parts of February and April

Rabaul (Papua New Guinea)

Lava flow issues from Tavurvur crater during 14 March eruption

Santa Maria (Guatemala)

Reports of 6 February dome collapse proven false

Sheveluch (Russia)

Steam and ash plume rises 1.5 km above the crater

Soufriere Hills (United Kingdom)

Pyroclastic flows advance over Galway's Wall on 29 March

Stromboli (Italy)

Summary of seismic and volcanic activity during May 1996-January 1997

Telica (Nicaragua)

Seismicity increases and fumarolic activity continues



Arenal (Costa Rica) — March 1997 Citation iconCite this Report

Arenal

Costa Rica

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

All times are local (unless otherwise noted)


Explosions diminished in January but continued through March

During January explosive activity diminished with respect to December 1996 in terms of both the number of eruptions and the quantity of ejected tephra. A S-flank avalanche on 1 January descended to ~1,000 m elevation. On the night of 14 January, a NE-flank pyroclastic flow traveled down to 800 m elevation, scalding vegetation. During February eruptive activity dropped yet lower, and in March, lower still. Despite these decreases, an incandescent avalanche was noted on 27 February at 1600. In addition, during the last week of that month the number of eruptions increased. March ash columns rose <1 km above Crater C. Crater D remained fumarolically active.

During January and February the lava flow on the N flank became active at 950 m elevation. During March, the N-flank flow maintained activity down to 800 m elevation and a new flow began, its path following the previous flow's channel and its front reaching 1,300 m elevation. Cold rock avalanches took place down local drainages (e.g. Calle de Arenas, Gillermina, and Rio Caliente).

Tremor duration peaked in April and June 1996 at around 400 hours/month; thereafter tremor typically remained at ~200-300 hours/month (figure 81). The number of earthquakes peaked in middle to late 1996 (figure 81). Surveys of the distance array revealed that between November 1996 and January 1997 the relative positions of survey stations contracted by an average of 4-5 ppm/month. In March it was reported that the average contraction seen in recent years (~27 ppm) continued along the radial lines on the volcano's W, SW, and S flanks. A dry-tilt station at the base of the volcano typically has small measured tilts amounting to 7-10 µrad/year.

Figure (see Caption) Figure 81. Arenal seismicity and tremor recorded during March 1996 through March 1997 (registered at station "VACR," 2.7 km NE of the main crater). Courtesy of OVSICORI-UNA.

The vegetation that had begun to regrow on the NE, E, and SE flanks continued to be affected by acid rain. Some species displayed burns on the edges and tops of leaves, while others showed signs of discolored leaves.

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

Information Contacts: E. Fernández, E. Duarte, V. Barboza, R. Van der Laat, E. Hernandez, M. Martinez, and R. Sáenz, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86, 3000 Heredia, Costa Rica.


Atmospheric Effects (1995-2001) (Unknown) — March 1997 Citation iconCite this Report

Atmospheric Effects (1995-2001)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Lidar data from Cuba, Hawaii, and Virginia

Table 10 lists atmospheric data from Cuba, Hawaii, and Virginia. Lidar data from Cuba for 27 September through 19 December 1996 indicated a possible atmospheric layer centered between 13.6 and 20.5 km altitude. Lidar data from Hawaii for 3 July through 18 December indicated a possible atmospheric layer centered between 21.7 and 28.0 km altitude. Lidar data from Virginia (USA) for 26 February through 3 April indicated a possible atmospheric layer centered between 15.5 and 20.5 km altitude.

Table 10. Lidar data collected for Cuba (1996), Hawaii (1996) and Virginia (1997), showing altitudes of aerosol layers. Backscattering ratios from Camagüey are for the Nd-YAG wavelength of 0.53 µm; those from Mauna Loa and Hampton are for the ruby wavelength of 0.69 µm. Integrated values show total backscatter, expressed in steradians-1, integrated over 300-m intervals from 16-33 km for Cuba, 15.8-33 km for Hawaii, and from the tropopause to 30 km for Virginia. For Cuba, only bases of the layers are shown. Courtesy of Rene Estevan Arredenta, John Barnes, and Mary Osborne.

DATE LAYER ALTITUDE (km) (peak) BACKSCATTERING RATIO BACKSCATTERING INTEGRATED
Camaguey, Cuba (21.2°N, 77.5°W)
27 Sep 1996 9.1 (16.3) 1.37 2.28 x 10-4
25 Oct 1996 15.1 (20.5) 1.21 1.00 x 10-4
30 Oct 1996 8.8 (19.0) 1.52 5.40 x 10-4
08 Nov 1996 9.4 (18.7) 1.45 3.54 x 10-4
01 Dec 1996 10.0 (18.1) 1.39 1.05 x 10-4
05 Dec 1996 9.4 (16.0) 1.31 2.14 x 10-4
11 Dec 1996 10.0 (18.1) 1.25 1.91 x 10-4
Mauna Loa, Hawaii (19.5°N, 155.6°W)
03 Jul 1996 16-28 (24.7) 1.22 0.48 x 10-4
10 Jul 1996 16-33 (24.1) 1.34 0.99 x 10-4
17 Jul 1996 6-34 (22.0) 1.29 0.83 x 10-4
01 Aug 1996 16-27 (25.3) 1.18 0.51 x 10-4
07 Aug 1996 16-32 (24.7) 1.36 0.88 x 10-4
20 Aug 1996 17-31 (24.4) 1.34 0.91 x 10-4
28 Aug 1996 16-31 (25.9) 1.28 0.67 x 10-4
04 Sep 1996 17-29 (23.5) 1.24 0.76 x 10-4
11 Sep 1996 17-30 (28.0) 1.40 0.88 x 10-4
18 Sep 1996 17-32 (24.1) 1.29 0.78 x 10-4
27 Sep 1996 17-32 (24.4) 1.28 0.73 x 10-4
02 Oct 1996 17-34 (25.3) 1.36 0.84 x 10-4
10 Oct 1996 16-34 (28.0) 1.38 0.97 x 10-4
17 Oct 1996 16-33 (25.0) 1.38 0.93 x 10-4
31 Oct 1996 16-32 (22.1) 1.30 0.95 x 10-4
27 Nov 1996 15-30 (24.4) 1.40 1.19 x 10-4
04 Dec 1996 17-34 (23.8) 1.28 0.63 x 10-4
10 Dec 1996 16-34 (25.0) 1.37 1.00 x 10-4
18 Dec 1996 16-34 (21.7) 1.45 1.20 x 10-4
Hampton, Virginia (37.1°N, 76.3°W)
26 Feb 1997 11-25 (19.6) 1.18 0.818 x 10-4
13 Mar 1997 11-25 (15.5) 1.15 0.562 x 10-4
21 Mar 1997 11-25 (16.1) 1.15 0.536 x 10-4
25 Mar 1997 13-25 (17.3) 1.16 0.508 x 10-4
03 Apr 1997 10-25 (20.5) 1.17 0.645 x 10-4

Information Contacts: Rene Estevan Arredondo, Centro Meterorologico de Camagüey, Apartado 134, Camaguey 70100, Cuba; John Barnes, Mauna Loa Observatory, P.O. Box 275, Hilo, HI 96720 USA; Mary Osborn, NASA Langley Research Center (LaRC), Hampton, VA 23665 USA.


Callaqui (Chile) — March 1997 Citation iconCite this Report

Callaqui

Chile

37.92°S, 71.45°W; summit elev. 3164 m

All times are local (unless otherwise noted)


Continuous fumarolic activity at main vent and upper S flank

A late-March overflight made after a prolonged dry season enabled views of Callaqui with relatively low snow levels. At the time of the overflight, the main vent at the summit showed vigorous steam emissions and sulfur deposits were noted around the two main fumarolic vents. Similar levels of fumarolic activity were noted over the preceding three weeks. Both the south side of the summit and the uppermost southern flank, at the head of the glaciers feeding the Río Malla, had continuous fumarolic activity. Rocks in these areas were highly altered. Emissions from the southern flank were more diffuse.

Geologic Background. The late-Pleistocene to Holocene Callaqui stratovolcano has a profile of an overturned canoe, due to its construction along an 11-km-long, SW-NE fissure above a 1.2-0.3 million year old Pleistocene edifice. The ice-capped, basaltic-andesite volcano contains well-preserved cones and lava flows, which have traveled up to 14 km. Small craters 100-500 m in diameter are primarily found along a fissure extending down the SW flank. Intense solfataric activity occurs at the southern portion of the summit; in 1966 and 1978, red glow was observed in fumarolic areas (Moreno 1985, pers. comm.). Periods of intense fumarolic activity have dominated; few historical eruptions are known. An explosive eruption was reported in 1751, there were uncertain accounts of eruptions in 1864 and 1937, and a small phreatic ash emission was noted in 1980.

Information Contacts: Jose Antonio Naranjo, Servicio Nacional de Geología e Minería (SERNAGEOMIN), Av. Santa María 0104, Casilla 10465, Santiago, Chile; Hugo Moreno Roa, Observatorío Volcanogía de los Andes del Sur (OVDAS), Manantial 1710-Carmino del Alba, Temuco, Chile; Simon R. Young, British Geological Survey (BGS), Murchison House, West Mains Road, Edinburgh EH9 3LA, United Kingdom.


Copahue (Chile-Argentina) — March 1997 Citation iconCite this Report

Copahue

Chile-Argentina

37.856°S, 71.183°W; summit elev. 2953 m

All times are local (unless otherwise noted)


Crater lake lies several meters below drainage notch

A late-March overflight made after a prolonged dry season enabled scientists to see Copahue with relatively low snow levels. The lake level was some meters below the prominent notch through which drainage occurs on the ESE side of the crater.

Light-gray mud deposits from recent overflow events extended halfway down the E flank. Deposits were also observed to the S and formed a small laharic fan of highly altered material near the head of the Río Lomín.

A pH of 2 was measured in Río Lomín in 1995; in contrast, during March the pH was neutral in the headwaters draining off the lahar fan. However, farther downstream the Río Lomím captures the Estero Turbío, which drains the S flank of the volcano and ran orange, presumably due to high acidity. After capturing Estero Turbío, Río Lomín reportedly became acidic and remained so all the way to its confluence with the Río Biobío, ~33 km from the volcano.

Geologic Background. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

Information Contacts: Jose Antonio Naranjo, Servicio Nacional de Geología e Minería (SERNAGEOMIN), Av. Santa María 0104, Casilla 10465, Santiago, Chile; Hugo Moreno Roa, Observatorío Volcanogía de los Andes del Sur (OVDAS), Manantial 1710-Carmino del Alba, Temuco, Chile; Simon R. Young, British Geological Survey (BGS), Murchison House, West Mains Road, Edinburgh EH9 3LA, United Kingdom.


Jan Mayen (Norway) — March 1997 Citation iconCite this Report

Jan Mayen

Norway

71.082°N, 8.155°W; summit elev. 2197 m

All times are local (unless otherwise noted)


Weak fumaroles on the inner NE crater wall

On 6 April, members of an SVE excursion visited the volcano and reported only weak fumarolic activity. White steam rose a few meters above the inner low part of the NE crater wall.

Beerenberg is a large glacier-covered stratovolcano at the N end of Jan Mayen Island. Numerous cinder cones have erupted along flank fissures, the latest in 1985.

Geologic Background. Remote Jan Mayen Island, located in the Norwegian Sea along the Jan Mayen Ridge about 650 km NE of Iceland, consists of two volcanic complexes separated by a narrow isthmus. The large Beerenberg basaltic stratovolcano (Nord-Jan) forms the NE end of the 40-km-long island, which is ringed by high cliffs. The glacier-covered Beerenberg has a 1-km-wide summit crater and numerous cinder cones that were erupted along flank fissures. It is composed primarily of basaltic lava flows with minor amounts of tephra. Historical eruptions at Beerenberg date back to the 18th century. The Sor-Jan group of pyroclastic cones and lava domes occupies the SW tip of Jan Mayen. The Holocene Sor-Jan cinder cones, tephra rings, and trachytic lava domes were erupted from short fissures with a NE-SW trend.

Information Contacts: Henry Gaudru, Michel Caplain, Alain Hirsh, and Yves Chetcuti, Société Volcanologique Européenne, C.P. 1, 1211 Genève 17, Switzerland (URL: http://www.sveurop.org/); Michel Halbwachs, Laboratoire d'Instrumentation Geophysique, University of Savoie, BP 1104, 73011 Chambery, France.


Karymsky (Russia) — March 1997 Citation iconCite this Report

Karymsky

Russia

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

All times are local (unless otherwise noted)


Ash plumes reported by aircraft pilot

No direct visual observations were made during 25 March-25 April, however the above-background seismicity suggested ongoing low-level Strombolian eruptions. On 14 April an airline pilot reported an ash plume at 6.1 km, but no plume was detected on GMS-5 satellite imagery.

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: Tom Miller, Alaska Volcano Observatory; Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry.


Kilauea (United States) — March 1997 Citation iconCite this Report

Kilauea

United States

19.421°N, 155.287°W; summit elev. 1222 m

All times are local (unless otherwise noted)


Lava flows outside of Pu`u `O`o for the first time since 31 January

Between 11 and 27 March, activity at the Pu`u `O`o vent along Kilauea's E rift zone was confined to the lava pond within the crater. Pond activity remained sluggish, with periodic resurfacing and localized overturning of the crust. On 21 March, the pond's surface rose to within 84 m of the NE rim of the crater, as indicated by a crusted-solidified shelf on the W floor of the crater, then subsided 14 m to 98 m below the crater rim. Reports of the crater glowing at night were thought to correspond with periods when the level of the pond's surface rose. Fumes emanating from the eruption site remained at low levels.

During these two weeks, the summit of Kilauea showed 8 µrad of inflationary tilt. In total, the summit recovered 29 µrad of the roughly 30 µrad of summit deflation that occurred on 30 January (BGVN 22:01).

On 28 March, lava was observed outside of the Pu`u `O`o crater for the first time since 31 January. Lava emanated from a collapse pit on the episode 51 shield that flanks the W side of Pu`u `O`o. This lava flowed into a depression to the S before it entered the old tube system, abandoned 30 January, through collapse pits and skylights. The following day, lava was seen flowing through the old tube system at the 2,400-ft (770 m) skylight. Also, the level of the pond in Pu`u `O`o rose to within 52 m of the NE rim, a level comparable to before the 30 January drain-back.

Three substantial lava flows escaped from the lava tube on 3 April. The lowest of the three breakouts fed a surface flow at the 721-m level. This flow progressed to the edge of the flow field and ignited vegetation along its edges as it advanced to elevations as low as 640 m. The next day, geophysical measurements showed that there was no lava flowing through tubes below the 705-m level. Through 7 April, flows repeatedly inflated, advanced, and stagnated.

Shallow, long-period summit earthquakes and earthquakes along the E rift zone remained at high to very high levels.

This latest resumption of activity, designated episode 55 by the Hawaiian Volcano Observatory, was considered likely to spread flows S over Pulama pali to the coast.

Kilauea is one of five coalescing volcanoes that comprise the island of Hawaii. Historically its eruptions originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the summit caldera to the sea. This latest Kilauea eruption began in January 1983 along the E rift zone. The eruption's early phases, or episodes, occurred along a portion of the rift zone that extends from Napau Crater on the uprift (towards the summit) end to ~8 km E on the downrift (towards the sea) end. Activity eventually centered on what was later named Pu`u `O`o. Between January 1983 and December 1996, erupted lava totaled ~1.45 km3.

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

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/).


Klyuchevskoy (Russia) — March 1997 Citation iconCite this Report

Klyuchevskoy

Russia

56.056°N, 160.642°E; summit elev. 4754 m

All times are local (unless otherwise noted)


Continuous presence of gas-and-steam plume up to 4 km above crater

Seismicity remained above background during 24 March-25 April. The presence of a gas-and-steam plume was reported from 25 March to 13 April at a height variable between 50 and 500 m above the crater and drifting NE to SE with the prevailing winds. On 27 March the plume rose to 1,500-4,000 m and spread 70 km to the E, and on 2 April to 1,500-3,000 m, moving 50 km to the E.

Geologic Background. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.

Information Contacts: 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; Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia.


Llaima (Chile) — March 1997 Citation iconCite this Report

Llaima

Chile

38.692°S, 71.729°W; summit elev. 3125 m

All times are local (unless otherwise noted)


Fumarolic activity at summit vent

A late-March overflight made after a prolonged dry season enabled scientists to see Llaima with relatively low snow levels. The main vent, in the SE part of the summit crater, emitted a bluish gas in poorly defined pulses at intervals of ~45 seconds. Similar pulses observed in mid-March took place at intervals of ~100 seconds.

The upper part of the main crater wall in the NW sector and small areas within the Pichillaima scar E of the main crater gave off diffuse steam emissions. A grayish plume at summit height was traceable for a few tens of kilometers to the ESE.

Geologic Background. Llaima, one of Chile's largest and most active volcanoes, contains two main historically active craters, one at the summit and the other, Pichillaima, to the SE. The massive, dominantly basaltic-to-andesitic, stratovolcano has a volume of 400 km3. A Holocene edifice built primarily of accumulated lava flows was constructed over an 8-km-wide caldera that formed about 13,200 years ago, following the eruption of the 24 km3 Curacautín Ignimbrite. More than 40 scoria cones dot the volcano's flanks. Following the end of an explosive stage about 7200 years ago, construction of the present edifice began, characterized by Strombolian, Hawaiian, and infrequent subplinian eruptions. Frequent moderate explosive eruptions with occasional lava flows have been recorded since the 17th century.

Information Contacts: Jose Antonio Naranjo, Servicio Nacional de Geología e Minería (SERNAGEOMIN), Av. Santa María 0104, Casilla 10465, Santiago, Chile; Hugo Moreno Roa, Observatorío Volcanogía de los Andes del Sur (OVDAS), Manantial 1710-Carmino del Alba, Temuco, Chile; Simon R. Young, British Geological Survey (BGS), Murchison House, West Mains Road, Edinburgh EH9 3LA, United Kingdom.


Lonquimay (Chile) — March 1997 Citation iconCite this Report

Lonquimay

Chile

38.379°S, 71.586°W; summit elev. 2832 m

All times are local (unless otherwise noted)


1988-89 lava flows continue emitting steam

A late-March overflight made after a prolonged dry season enabled observations with relatively low snow levels. The volcano lacked signs of fumarolic or other activity. However, during fieldwork S of La Holandesa crater, the 1988-89 lava flows to the NE of the main cone within the Las Paramelas valley continued to emit steam.

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

Information Contacts: Jose Antonio Naranjo, Servicio Nacional de Geología e Minería (SERNAGEOMIN), Av. Santa María 0104, Casilla 10465, Santiago, Chile; Hugo Moreno Roa, Observatorío Volcanogía de los Andes del Sur (OVDAS), Manantial 1710-Carmino del Alba, Temuco, Chile; Simon R. Young, British Geological Survey (BGS), Murchison House, West Mains Road, Edinburgh EH9 3LA, United Kingdom.


Manam (Papua New Guinea) — March 1997 Citation iconCite this Report

Manam

Papua New Guinea

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

All times are local (unless otherwise noted)


Activity low with increase near the end of the month

During March, Manam was only mildly active and visibility was poor. When visible, the crater was gently emitting a white plume and on two nights there were reports of crater glow. Activity increased slightly during the last week of March. Main Crater had white-to-gray emissions accompanied by occasional weak roaring. Aviation reports noted that at around 1600 on 22 March an eruption plume rose to 3,000 m and drifted SSE. The Tabele water-tube tiltmeter recorded a slight but steady radial inflation.

There was a slow and steady rise in seismicity throughout the month. The number of low-frequency earthquakes increased from ~1,400-1,600 events/day. The amplitude of the events also increased with time.

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

Information Contacts: B. Talai, H. Patia, D. Lolok, P. de Saint Ours, and C. McKee, RVO; Bureau of Meteorology, Northern Territory Regional Office, P.O. Box 735, Darwin, NT 0801 Australia.


Masaya (Nicaragua) — March 1997 Citation iconCite this Report

Masaya

Nicaragua

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

All times are local (unless otherwise noted)


Strombolian explosion; incandescent vent in Santiago crater; seismicity increases

A small Strombolian explosion on 5 December 1996 ejected blocks (<10 cm in diameter), ash, and some Pelee's hair. Some of the inner crater walls collapsed, partly closing the incandescent vent. Prior to this eruption the vent's gas temperature was 1,084°C; afterwards, it dropped to 360°C.

During three consecutive days in 1997, COSPEC SO2 fluxes varied as follows: on 12 February, 159 ± 73 metric tons/day (t/d) (1 sigma, n = 5); on 13 February, 363 ± 182 t/d (1 sigma, n = 6); on 14 February, 290 ± 65 t/d (1 sigma, n = 4). The 363 t/d figure is a minimum estimate since on the first 3 traverses the instrument went off the chosen recording scale indicating still larger values than reported.

A visit in March 1997 yielded COSPEC values of 300-400 t/d; these values were lower than those obtained during March 1996 (BGVN 21:04). Nightime observations of the active Santiago crater revealed that large amounts of incandescent gas were being released frequently through a conduit that had partially collapsed on 5 December 1996. As a result of the collapse, it was not possible to see incandescent magma during the night.

Seismicity increased since September 1996; in January 1997, 41 events (4 high- and 47 low-frequency) were recorded along with constant tremor. During 22 February-20 March, 18 events occurred, 15 of which were low-frequency and three high-frequency. Since November 1994 background levels of RSAM have varied between 12 and 16 RSAM units. Since mid-January, however, RSAM increased, fluctuating between 22 and 32 units.

In the crater area, gravity decreased steadily during 1993-95; it remained stable in 1996 and possibly increased a little in 1997.

A NE-trending fracture at the base of Comalito cone emitted gases reaching 68°C. In this same vicinity soil gas concentrations contained up to 25% CO2.

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

Information Contacts: Hazel Rymer and Mark Davies, Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom; John Stix, Dora Knez, Glyn Williams-Jones, and Alexandre Beaulieu, Departement de Geologie, Universite de Montreal, Montreal, Quebec H3C 3J7, Canada; Nicki Stevens, Department of Geography, University of Reading, Reading RG2 2AB, United Kingdom; Martha Navarro and Pedro Perez, INETER, Apartado Postal 2110, Managua, Nicaragua.


Okmok (United States) — March 1997 Citation iconCite this Report

Okmok

United States

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

All times are local (unless otherwise noted)


Emission of steam, ash, and lava continues

Reports on 27 March, and 4, 11, 18, and 25 April, confirmed that the eruption which began on 13 February was continuing at relatively low levels. Satellite images examined by AVO indicated the presence of hot lava flows in the caldera, and occasional thin, low-level plumes drifting downwind from the volcano. NOAA/NESDIS also reported that on 4 April an aircraft pilot saw lava flows and [observed] an ash column at ~3,500 m, drifting slowly SE. On 12 April another ash plume was reported by a pilot at 2.4 km; this same plume was detected in visible and infrared satellite imagery.

Okmok volcano is not monitored seismically and is not assigned a color code. Based on past eruptive history, lava flows and low--level ash emission could continue for weeks to months. Eruptive activity could intensify at any time.

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); NOAA/NESDIS Satellite Analysis Branch (SAB).


Pacaya (Guatemala) — March 1997 Citation iconCite this Report

Pacaya

Guatemala

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

All times are local (unless otherwise noted)


Graduate students study gas emission and lava flow

Between 5 and 13 February graduate students from Northern Illinois University in collaboration with INSIVUMEH scientists conducted studies at Pacaya volcano. Focused fumarolic activity was observed at the summit, whereas diffuse gas emissions occurred around the SW flanks. Numerous micro-seismic earthquakes were recorded daily during this period.

Lava samples were collected from the 11 November 1996 flow. Analysis showed that the lava was a highly- vesicular, plagioclase-phyric basalt that resembles basaltic flows from previous eruptions.

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

Information Contacts: Otoniel Matías, Seccion Vulcanología, INSIVUMEH (Instituto Nacional de Sismología, Vulcanología, Meteorología e Hydrología of the Ministerío de Communicacíones, Transporte y Obras Publicas), 7A Avenida 14-57, Zona 13, Guatemala City, Guatemala; Barry Cameron and Shane Rundle, Department of Geology, Northern Illinois University, USA.


Platanar (Costa Rica) — March 1997 Citation iconCite this Report

Platanar

Costa Rica

10.3°N, 84.366°W; summit elev. 2267 m

All times are local (unless otherwise noted)


Dormancy continues but S-flank residents felt six earthquakes on 30 March

On 30 March 1997 residents in the S-flank settlement of San Vicente felt about six earthquakes between 0900 and 2100. One of these earthquakes took place at 1429; it was M 2.7 and its epicenter was 5 km SE of the volcano. No residents in other nearby settlements (Porvenir, Sucre, and Quesada) reported feeling these earthquakes.

About 10 days after the earthquakes, two dry-tiltmeters, measured every 2-3 years, showed differing results. One showed great changes but had been disturbed; the other, which was considered more reliable, had changed little. An April 1980 seismic swarm near Platanar, attributed to a local fault, continued for 2-3 weeks.

Geologic Background. The Platanar volcanic center is the NW-most volcano in the Cordillera Central of Costa Rica. The massive complex covers about 900 km2 and is dominated by two largely Pleistocene stratovolcanoes, Platanar and Porvenir. These volcanoes were constructed within the Pleistocene Chocosuela caldera, which may have formed during a major slope failure. The Cerro Platanar volcano (known locally as Volcán Congo) on the N side of the complex has prehistorical lava flows on its W flanks and is the youngest volcanic center. The highest peak is Porvenir, whose summit crater lies 3 km S of Platanar. A thin layer of phreatic ash suggested that an eruption from Platanar occurred within the past few thousand years (Stine and Banks, 1991). The Aguas Zarcas group of nine basaltic cinder cones, located on the N flank of the Platanar-Porvenir complex to as low as 160 m altitude is, in part, Holocene in age.

Information Contacts: E. Fernández, E. Duarte, V. Barboza, R. Van der Laat, E. Hernandez, M. Martinez, and R. Sáenz, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86, 3000 Heredia, Costa Rica.


Poas (Costa Rica) — March 1997 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Relatively stable but seismically active

Periodic visits revealed that the crater lake level changed as follows compared to December 1996: January, a 31 cm decrease; February, a 55 cm decrease; and March, an 88 cm decrease. Lake-water temperatures during January, February, and March measured 32, 30, and 29°C, respectively. A pH of 1.7 was measured in March. During January-March constant bubbling took place on the lake's S and SW shores. During January and February one fumarole remained noisy; as late as March those on the SE, S, and SW remained at 91- 93°C. The migration of fumaroles was noted in March. Fumarolic gases emitted from the accessible parts of the pyroclastic cone had temperatures of 92°C (January) and 92-93°C (February). Temperatures were not reported for March. During January-March, steam clouds rose 400 m above the crater floor.

Scientists collected acid rain at Cerro Pelón on five days during 7 January-10 March. The respective SO4 and Cl ion concentrations ranged between ~5 and 12 mg/liter, and 1 and 6 mg/liter; pH ranged between 3.5 and 4.5.

A seismic swarm on 31 January consisted of 47 primarily low-frequency earthquakes; some occurred3.0 Hz), 0-99. During the same interval, monthly tremor prevailed for 0-28 hours, peaking in October 1996.

Figure (see Caption) Figure 64. Poás seismicity (at frequencies below 2 Hz) recorded 2.7 km SW of the active crater (station POA2), March 1996 to March 1997. Courtesy of OVSICORI-UNA.

During January, both the distance network and dry-tilt readings at the summit remained stable. As of March, the three deformation lines across the crater and one external radial line had shown no significant changes during 1997. Another line, from the S side of the overlook (mirador) to the crater bottom, detected a cumulative contraction of 119 ppm/year. This contraction may have come from adjustments due to shallow phreatic venting and an increase in the crater lake's height. Changes in the inclinometer network were not considered significant.

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

Information Contacts: E. Fernández, E. Duarte, V. Barboza, R. Van der Laat, E. Hernandez, M. Martinez, and R. Sáenz, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA).


Popocatepetl (Mexico) — March 1997 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Summaries for March and parts of February and April

A series of non-technical reports covering the volcano's behavior during the interval 17 February to 4 April are summarized in table 4. During this interval the hazard alert remained at yellow on a scale that encompasses the categories green (low), yellow, and red (high). The summaries document a pattern of isolated exhalations (some bearing ash) and occasional type-A seismic events. Noteworthy exhalations occurred on many days in the last three weeks of March. For example, on 20 March a relatively large exhalation lasted 7 minutes and spawned an ash column that rose to 4 km above the vent.

Table 4. Summary of non-technical reports describing activity at Popocatépetl, 17 February-4 April 1997. The alert status remained moderate (yellow) during this entire interval. Courtesy of Roberto Quaas, CENAPRED-UNAM.

Report Date Comment
17 Feb 1997 During 15-16 February activity was low and stable. Seismicity was also low but there were indications of isolated exhalations.
19 Feb 1997 Activity remained similar to that described in on the 17 February report; a type-A event of very small magnitude occurred at 0727.
25 Feb 1997 During the interval 1017-1130, tremor occurred accompanied by two intense exhalations (at 1029 and 1031). The exhalations produced a column of gas and ash that reached up to 3 km in altitude drifting to the SE. At 1239 a less-intense exhalation occurred but gas and ash were still emitted over a prolonged interval.
26 Feb 1997 After a short period of relative tranquility, during the previous night there was a moderate increase in the level of exhalations. At 0620 on 26 February a major exhalation occurred followed by prolonged tremor. A second large exhalation at 0915 accompanied increased tremor. Starting on 25 February, the volcano produced a plume of variable intensity that occasionally contained ash.
27 Feb 1997 Overall activity fell considerably compared to yesterday. Seismicity was limited to some weak exhalations and three type-A events of very low magnitude. Plume diminished in size and density.
28 Feb 1997 Stable activity such that in the last 24 hours there were only occasional exhalations and two type-A events of very low magnitude.
10 Mar 1997 During 8-9 March, activity remained stable without important changes. A few type-A events with low level magnitudes were registered. The plume was very small.
12 Mar 1997 At 0430 a moderate ash-bearing exhalation occurred associated with light tremor, which continued until the time of the report. High-velocity winds led to light ash rains on towns near the volcano. Local authorities were informed. Up until the time of the report, activity remained moderate without the threat of danger.
14 Mar 1997 General activity has decreased compared to that of 12 March. There persisted a white plume of small volume and on average, six small exhalations per day. Seismicity remained moderate except for type-A events: one, this day at 1130 (M 3.3) and the other, the previous day at 2130 (M 2.3).
17 Mar 1997 During 15-16 March there was a significant increase in exhalations both in terms of number and size, with an average of 50 per day. Between exhalations, type-A events occurred, many of low magnitude (only three reached near M 3). The larger earthquakes took place on 14, 15, and 17 March. The volcano produced a grayish-white plume. This level of activity was similar to that of April and May of 1996.
18 Mar 1997 The general level of activity stabilized, tending towards low values with respect to those seen yesterday. Although in minor proportion, the exhalations and type-A events persisted. The plume lacked significant changes.
19 Mar 1997 During the night, and today, the number and size of exhalations increased and at 0750 tremor occurred. It accompanied a plume that probably carried a moderate amount of ash.

The Satellite Analysis Branch of NOAA (SAB) conveyed several messages about ash plumes during February-March 1997. In one case, aviators near México City on American Airlines flight 1211 reported ash at 1500 on 5 February reaching 9.1 km. At 1715, GOES-8 satellite imagery indicated a detached plume ~90 km to the volcano's E; the plume was 45 km wide and at 7.6-9.1 km altitude. After that, Air Traffic Control in México City received no further pilot reports, and according to SAB, the plume dissipated in GOES-8 imagery around 2015.

A message from a United Airlines flight on 8 February around 0945 noted ash above México City at ~9.1 km altitude. Another pilot report noted that at 1715 there were narrow bands of ash at unspecified distances from the volcano at 5.5-6.1 km altitude, and farther S between 7.3 and 7.9 km altitude. A SIGMET issued in México City (valid during 1210-1800) warned of ash 28 km NE of the volcano between 5.2 and 6.4 km altitude. In addition, at 0945 a GOES-8 satellite image showed a plume near the summit extending S. By 1600 the eruption had stopped and radiosonde data established the plume at an altitude of ~9.4 km. At that time, the plume had become barely visible and rapidly fading on infrared imagery; it had moved 37 km SSE.

The third message, from a United Airlines flight at 0815 on 12 March, noted an eruption then. GOES-8 satellite imagery indicated a plume oriented ESE (on a bearing of 110 degrees). The plume extended for 70 km by 0945; at that time it was very narrow, linear, and at ~7.9 km altitude. Later, at 1115, a faint fan-shaped plume reached 55 km wide at 135 km SE of the volcano. The plume became covered by high-altitude weather clouds by 1315.

In addition, one available CENAPRED weekly seismic report (Number 59) covered the interval 7-13 April 1997; it showed a) the seismic and tiltmeter network (figure 16), b) computed epicenters during that time (figure 17), and c) cumulative seismicity for the interval 5 February 1996-15 April 1997 (figure 18). Figure 17 illustrates that many of the epicenters plot ~10 km SE of the crater. The epicenters SE of the crater caused investigators to ask if these earthquakes arose from volcanic or fault-related sources. To address this question, the investigators planned to deploy a network of portable broad-band seismometers to better cover this area.

Figure (see Caption) Figure 16. Popocatépetl seismic and tilt stations, February 1997. Courtesy of Roberto Quaas, CENAPRED-UNAM.
Figure (see Caption) Figure 17. Epicenters for Popocatépetl earthquakes registered on the monitoring network, 7-13 April 1997. The contour interval is 100 meters. Courtesy of Roberto Quaas, CENAPRED-UNAM.
Figure (see Caption) Figure 18. Number of weekly Popocatépetl earthquakes counted by visual inspection and using Xdetect software, 5 February-15 April 1997. The number of times alarms were triggered is also shown. Courtesy of Roberto Quaas, CENAPRED-UNAM.

Figure 18 shows monthly totals both for earthquakes counted by eye directly from the seismograms (higher bars) and by using software called Xdetect (lower bars). Although this latter technique detects events automatically, the totals (which depend on the trigger thresholds) are much smaller than counts made by eye.

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: Roberto Meli, Roberto Quaas Weppen, Servando De la Cruz- Reyna1, Alejandro Mirano, Bertha López Najera, and Alicia Martinez Bringas, Centro Nacional de Prevencion de Desastres (CENAPRED), Delfin Madrigal 665, Col. Pedregal de Santo Domingo, Coyoacan, 04360, México D.F., Mexico. 1Instituto de Geofisica, 1UNAM, Circuito Cientifico C.U.,04510 México D.F., México; NOAA/NESDIS Satellite Analysis Branch (SAB), Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA.


Rabaul (Papua New Guinea) — March 1997 Citation iconCite this Report

Rabaul

Papua New Guinea

4.271°S, 152.203°E; summit elev. 688 m

All times are local (unless otherwise noted)


Lava flow issues from Tavurvur crater during 14 March eruption

On 14 March, a strong Strombolian and lava-producing eruption occurred at Tavurvur, the small active cone on the E side of the Rabaul Caldera (figure 29). This was the third eruption of this type since October 1996 (BGVN 21:12 and 22:01). Two photos of Tavurvur and vicinity from November 1996 show the effects of eruptions since 1994 (figures 30 and 31).

Figure (see Caption) Figure 29. Map of Rabaul Caldera showing locations of volcanic vents, selected towns, and features (modified from Almond and McKee, 1982).
Figure (see Caption) Figure 30. Photograph of a weakly steaming Tavurvur cone taken from the peninsula leading to Matupit Island, November 1996. Turanguna cone sits in the background. The abundant ash in the foreground was deposited during the 1994 eruption. Courtesy of Nancy Roper.
Figure (see Caption) Figure 31. Photograph of Tavurvur's extreme N flank (upper right edge), Turanguna (right background), and devastated groves and structures, November 1996. Courtesy of Nancy Roper.

Emissions from Tavurvur in early March consisted of pale gray vapor clouds that commonly rose ~600 m above the crater. Vulcanian explosions occurred occasionally and were commonly followed by ash emission lasting from 20 minutes to 2 hours. On 6 March, a Vulcanian explosion ejected lithic blocks that fell over the entire cone, the farthest reaching Greet Harbor (1 km from the vent). During the explosion, a small landslide on the NW flank of the volcano left a scar several hundred meters long.

At 0736 on 14 March a large and loud explosion was accompanied by a gray ash-rich eruption plume. Within an hour, Strombolian explosions ejected fragments that showered Tavurvur cone. By 0930, sub-continuous Strombolian eruptions occurred; these commonly produced loud detonations; in addition, flashing arcs were noted in the eruption plume. Some of the explosions sent "large lumps of lava" up to 1 km above the crater at intervals ofBGVN22:01) and partially overrode the October 1996 and January 1997 lava flows. The strength of the eruption did not begin to decrease until about 1530. By 2200 the eruption had declined to discontinuous explosions. Lava reached the sea near Sulphur Point sometime during the night (figure 29).

Due to a strong wind, the eruption plume was dispersed to the SW and remained below 2 km in height. Approximately 2 km SW, the town of Talway accumulated a 13-cm-thick pumiceous deposit. The detonations were very loud in the Kokopo area, 14 km SW. The Tokua airport ~20 km SW was closed for most of the day due to the threat of ashfall.

On 15 March, strong eruptions continued at intervals of minutes to hours and eruption plumes rose 400-600 m. Occasionally a peculiar pulsating roaring sound was heard that generally correlated with periods of harmonic tremor.

The level of activity continued to decrease between 16 and 19 March. There were progressively less frequent, but still loud, explosions with occasional roaring sounds. For the remainder of March, the level of activity was low, with weak white plumes rising to ~500 m above the crater. Occasionally, large explosions sent plumes as high as 3,000 m above the crater.

Seismicity began to increase on 7 March and reached 300 events/day with real-time seismic amplitude measurement (RSAM) levels rising to ~60-120. Levels decreased during 11-12 March but increased again on the 13th. During the eruption on 14 March, RSAM levels reached a plateau of ~ 850, similar to October 1996 and January 1997 eruption levels. By 2200 on 14 March, RSAM levels had dropped to ~100. A few intervals of harmonic tremor were recorded on 18-20, 22, 24-25, and 28 March.

Correlation spectrometer (COSPEC) measurements early in the month revealed SO2 fluxes of 2 fluxes increased to 400-700 tons/day before returning to background levels on 18 March. By the end of March, SO2 fluxes began to rise again.

In response to the eruption, the SCK water-tube tiltmeter 3.3 km NW of Tavurvur showed a radial deflation of 11 µrad (compared to 16 µrad and 11 µrad during the October and January eruptions, respectively). By the end of the month, radial inflation began to increase again.

Reference. Almond, R.A., and McKee, C.O., 1982, Location of volcano-tectonic earthquakes within the Rabaul Caldera: Geological Survey of Papua New Guinea report 82/19.

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

Information Contacts: B. Talai, H. Patia, D. Lolok, P. de Saint Ours, and C. McKee, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea; Bureau of Meteorology, Northern Territory Regional Office, P.O. Box 735, Darwin, NT 0801 Australia.


Santa Maria (Guatemala) — March 1997 Citation iconCite this Report

Santa Maria

Guatemala

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

All times are local (unless otherwise noted)


Reports of 6 February dome collapse proven false

Reports of a significant dome collapse at Santiaguito on 6 February were proven false during investigations conducted by geologists from the Instituto Nacional de Sismología, Vulcanología, Meteorología e Hydrología (INSIVUMEH). It is likely that minor downslope movement of loose debris near the summit caused the report.

At 1900 and 2100 on 11 February, local residents from farms S of the dome saw a significant dacitic lava flow.

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

Information Contacts: Otoniel Matías, INSIVUMEH, Guatemala; Barry Cameron and Shane Rundle, Northern Illinois University, USA.


Sheveluch (Russia) — March 1997 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Steam and ash plume rises 1.5 km above the crater

On 25 March, a steam-and-ash plume rose ~1,500 m above the volcano and extended 30 km to the NW. During 26-31 March the usual fumarolic activity was observed above the crater. A steam-and-ash plume at 100- 200 m above the crater was also reported during 1-4 April.

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: 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; Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia.


Soufriere Hills (United Kingdom) — March 1997 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Pyroclastic flows advance over Galway's Wall on 29 March

The following summarizes the weekly Scientific Reports of the Montserrat Volcano Observatory for the period 9 March-5 April 1997.

Visual observations. During the first 20 days of March several ash clouds drifted W on the prevailing wind, small pyroclastic flows issued from the E and S areas of the dome, and small-scale rockfalls were confined to the area SE to NE of the dome complex.

Small, relatively cool, pyroclastic flows with a maximum run-out distance of ~1 km were almost continuous from the pre-17 September dome to the N of Galway's Wall (see map in BGVN 22:02). An erosional chute was formed in the pyroclastic-flow deposit leading out from the crater wall. Small landslides occurred from areas E and W of the point on the wall over which the flows traveled. On 18 March fresh deposits with well-developed levee structures reached beyond 1 km from the crater wall to the SW. On 20 March new fractures 100-150 m long and trending SSE were observed running through the S buttress of Galway's Wall, in the area adjacent to Perches Mountain.

Growth continued in the uppermost areas of the 20 January dome: during 13-21 March new spines appeared on the summit area and afterwards moved up toward the E side of the dome. Eventually extrusion in the summit region overgrew the original January scar and overall the shape of the dome changed from flat topped to a more conical geometry.

During the week of 22-29 March a large block tilting to the SSW appeared in the SW region of the dome complex. Two distinct peaks began to develop in the summit area of the dome, the highest being on the S side of the dome overlooking the Galway's Wall. A cleft formed between the two peaks, with material being extruded upwards and to the SW. The dome grew so much above Galway's Wall that there was no barrier left between the new material and the wall itself. Fresh cracks were observed running through the E shoulder of the Galway's Wall on 25 March. Fresh landslide scars and cracks were observed in the Gages Wall on 26 and 28 March, but no fresh activity was noted in the dome behind and above it.

At 1630 on 29 March a large pyroclastic flow occurred over the Galway's Wall into the White River valley. The flow traveled ~400 m farther than previous flows in this region and produced a dark ash cloud that rapidly convected to ~1,500 m. Activity increased at around 1330 on 30 March when another pyroclastic flow occurred over Galway's Wall from the SE summit. Observations from the helicopter of the Galway's Soufriere region revealed that the pyroclastic material was cascading over the Galway's Wall almost contiguously, with the higher velocity flows surging through the smaller, slower-moving flows. Vigorously convecting, co-ignimbrite-type ash clouds rose to heights of 3.5 km. Pyroclastic-flow activity waned at around 1630 after flows traveled 3.6 km down the White River and caused some burning of vegetation. Trees in the distal portion of the flows remained standing, suggesting sluggish movement of flows in the lower part of the valley.

The intense pyroclastic flow activity on 31 March sent material only ~50 m farther down the White River than the previous day. Pyroclastic flows observed from a helicopter on 31 March were valley-confined; on the W side of Galway's Soufriere there were fine-grained deposits and tree flattening associated with pyroclastic surges. Considerable ponding of pyroclastic-flow deposits had occurred, and the Great Alps Falls in the White river were reduced to only ~10 m high from the original 50 m. Finally it was observed that the pyroclastic flows had cut a gully 80 m deep and 50 m wide into Galway's Wall.

The "Easter scar"— the collapse scar formed in the dome complex — was composed of two scallops, one in the 20 January dome with a near vertical head wall, and the second cut into the pre-September dome. Growth of the dome since collapse, and rockfall debris, have rapidly begun to fill the scar.

At around 1500 and 1515 on 31 March two major pyroclastic flows from the NE summit of the dome occurred in the Tar River to the E. The first flow reached ~200 m past the first break in slope, the second flow reached to within ~50 m of the fan. Temperature patches positioned down the track leading into the Tar River valley were engulfed by the surge clouds of the latter flow, and indicated temperatures of 99-149°C for lateral distances of 60 m inside the pyroclastic surge.

Several relatively large pyroclastic flows occurred over the Galway's Wall starting from 1230 on 1 April, but none of them reached as far as those on the 30 and 31 March although considerably more tree flattening occurred in the area directly W of the Galway's Soufriere. This indicated that these flows had a large surge component, probably due to the earlier valley filling.

Large ash clouds associated with the flows rose to 4.3 km and drifted NW producing ash fall over large part of the island as far N as St Peters and St Johns. On 2 April more pyroclastic flows over Galway's Wall generated ash clouds to ~3.3 km of altitude.

Dome growth since the collapse was confined to the Easter scar with upward and southward growth of the steep head wall. The actively growing area had a smooth, scabby, arcuate upper surface with local fractures and N-S running striations indicative of extrusion. Vigorous brown gas jets were seen emerging from cracks in the upper surface. Rockfall debris began to fill the chute carved by the pyroclastic flows into the Galway's wall toward the end of the reporting period. Mudflows during the nights of 3 and 4 April in Fort Ghaut and Aymer's Ghaut left debris on roads and close to houses.

Seismicity. During 8-21 March there were swarms of mainly hybrid events interspersed with periods of relative quiescence. The foci were located at 1-3 km depth below the crater area. Rockfall activity was mainly concentrated in periods between the earthquake swarms, although some of the larger events during a swarm were followed by rockfall and pyroclastic signals from material cascading over the Galway's Wall.

After 22 March the seismicity decreased. The swarms became shorter and less intense, whereas there was a slight increase in the level of rockfall activity and in the number of long-period earthquakes. Occasionally long- period events were present for a few days to weeks, with a maximum of 40 events/day, mostly very small. About 50% of the long-period earthquakes were immediately followed by rockfall signals, as in October and December 1996. It is possible that the long-period events are caused by some dome process, such as gas venting or a sudden growth spurt that leads to partial collapse.

During 30 March-2 April, the dominant seismicity was related to dome collapse, with many rockfall and pyroclastic-flow signals. The level of rockfall and long-period activity decreased abruptly on 3 April, when a swarm of volcano-tectonic events followed by hybrid earth a very slow trend of shortening, respectively. EDM measurements on the N triangle (Windy Hill-Farrells-St. George's Hill) showed an overall stable trend. On 29 March a very slow shortening trend was recorded for the line Windy Hill-St. George's Hill: the total shortening over the past 15 months was ~15 mm.

GPS occupations on 10-11 March with a base station at Harris showed that Hermitage station had moved by 2.5 cm to the NNE since 18 January and had risen by ~9 cm. A GPS occupation of the Eastnet on 15 March recorded a total movement of 2.5 cm to the NNE for Farrells station, ~700 m from the N edge of the dome, since 13 June 1996. During 22-29 March GPS occupations with a base at Harris showed that Station FT3 (Farrells Crater Wall) , had moved 17.6 cm to the NW since 18 January (2.7 mm/day), Hermitage had no significant movement since 17 March, and Perches recorded a 1.6 cm movement to the N since 18 January.

A new crack on the shoulder of Galway's Mountain was measured for the first time on 25 March, with nails hammered into trees on either side of the crack. One array of nails was placed on the steep flank of the mountain at ~ 50 m from the crater wall; the second array was 90 m to the S in a flatter area. All the lines measured on 28 March showed no significant changes in length.

The GPS occupation of Eastnet on 30-31 March and 4 April revealed that the Farrells site had moved ~4 cm to the N since June 1996 at an increasing rate of movement.

Both the GPS and EDM techniques showed the ongoing slow deformation of the N crater wall in the Farrells area; deformation rate drops rapidly with distance from the dome. Neither technique was able to detect any significant deformation around the volcano.

Dome volume measurements. A survey completed on 14 March using the fixed location photographic method showed 1.34 x 106 m3 added to the dome since 1 March, at an average extrusion rate of 1.08 m3/s.

A GPS survey of the talus at the base of the dome combined with the fixed-location photographic method and the GPS/range-finding binocular method resulted in an estimate of 0.8 x 106 m3 material added to the dome from 14 to 19 March. From the photographic profiles it became apparent that the summit dome had grown by 15 m during the same period.

Evidence was found that the pre-September scar material, surrounding the dome on the NW, W, and SW sides, was pushed outward by the growing dome. The amount of movement was 3.9 m during 23 November to 8 January (80 mm/day), and 9.1 m during 8 January-19 March 1997 (13 mm/day).

A GPS bathymetry survey around the pyroclastic fan at the foot of the Tar River Valley on 21 March, combined with a survey of the fan surface on 12 February resulted in a total fan volume estimate of 15.5 x 106 m3.

The results of a 27 March GPS survey indicated that since 19 March the dome volume had increased by 0.98 x 106 m3, at a rate of 1.26 m3/s. This gave a total dome volume of 49.7 x 106 m3 (44.7 x 106 m3 DRE). Digital elevation models created from this survey indicated that growth was focused on the S peak of the dome and the rest of the dome remained relatively unchanged. A GPS dome survey on 2-3 April indicated that the last collapse removed ~1.6 x 106 m3 of material, of which roughly 40% was preSeptember 1996 scar material and 60% new dome material.

Environmental monitoring. Measurements of sulfur dioxide flux were made using the MiniCOSPEC on 10, 14, 15, 17, 24, 28 March, and 4 April and results were as follows: 700, 213, 341, 317, 198, 160, and 573 t/d respectively. The high values on 10 March and 4 April were associated with the recurrence of earthquake swarms and an increase in activity, respectively.

Results for SO2 diffusion tubes collected during the period 9-23 February showed values similar to those measured over the last few months and are presented in table 15.

Table 15. Sulfur dioxide diffusion tube results at Soufriere Hills for the period between 9 February and 23 February 1997. Courtesy of MVO.

Location SO2 (ppb)
Upper Amersham 47.70
Lower Amersham 17.30
Airport 0.80
Police HQ, Plymouth 9.00
Weekes 9.00
Control 0.00

Results from rain water samples collected at 4 locations around the volcano on 9, 16, 23, and 31 March, showed that the rainwater directly W of the volcano was still highly acidic and had high concentrations of certain anions (table 16). One sample collected from the overflow of Trials reservoir in Fairfield was within World Health Organization levels for all measured components.

Table 16. Rain and surface water geochemistry at Montserrat. Courtesy of MVO.

Date Location pH Conductivity (mS/cm) Total Dissolved Solids (g/l) Sulfates (mg/l) Chlorides (mg/l) Fluorides (mg/l)
09 Mar 1997 Upper Amersham 2.39 2.120 1.050 25 250 1.5
09 Mar 1997 Lower Amersham 2.55 1.162 0.582 16 115 1.5
09 Mar 1997 Police HQ, Plymouth 2.57 0.926 0.464 -- 97 1.5
09 Mar 1997 Weekes 6.49 0.172 0.086 -- 27 0.3
16 Mar 1997 Upper Amersham 2.39 1.883 0.942 34 232 1.35
16 Mar 1997 Lower Amersham 2.70 0.731 0.366 8 100 1.5
16 Mar 1997 Police HQ, Plymouth 2.81 0.571 0.285 3 68 1.4
16 Mar 1997 Weekes 6.11 0.070 0.035 -- 14.4 0.1
16 Mar 1997 Trials Reservoir 7.55 0.659 0.330 40 83 0.55
23 Mar 1997 Upper Amersham 2.28 2.41 1.20 36 211 1.45
23 Mar 1997 Trials Reservoir 7.63 0.675 0.388 39 76 0.40

The maximum thickness of ash collected on 31 March in Plymouth was 16 mm, at the American University of the Caribbean, and the total erupted airborne ash volume on 30-31 March was calculated to be 0.1 x 106 m3, dense rock equivalent (DRE).

Geologic Background. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. The volcano is flanked by Pleistocene complexes to the north and south. English's Crater, a 1-km-wide crater breached widely to the east by edifice collapse, was formed about 2000 years ago as a result of the youngest of several collapse events producing submarine debris-avalanche deposits. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits, including those from an eruption that likely preceded the 1632 CE settlement of the island, allowing cultivation on recently devegetated land to near the summit. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but no historical eruptions were recorded until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

Information Contacts: Montserrat Volcano Observatory (MVO), c/o Chief Minister's Office, PO Box 292, Plymouth, Montserrat (URL: http://www.mvo.ms/).


Stromboli (Italy) — March 1997 Citation iconCite this Report

Stromboli

Italy

38.789°N, 15.213°E; summit elev. 924 m

All times are local (unless otherwise noted)


Summary of seismic and volcanic activity during May 1996-January 1997

The following summarizes the interval from 15 May 1996 to 31 January 1997. Eruptive activity increased in mid-April 1996 (BGVN 21:04) and continued through mid-June with significant explosions (BGVN 21:05). A flight on 16 July 1996 documented a plume rising from Stromboli using a Wide Angle Optoelectronic Stereo Scanner (figure 50). This image of the entire island also shows older lava flows, the Sciara del Fuoco, and the Pizzo Sopra La Fossa (120 m above and 250 m SE of the vent), where people often make observations from.

Figure (see Caption) Figure 50. Wide Angle Optoelectronic Stereo Scanner (WAOSS) image of Stromboli taken on 16 July 1996. Courtesy of Martin Scheele, DLR.

Figure 51 illustrates the change in crater morphology between April 1996 and September 1996. Unfortunately the morphological changes in Crater 1 (typically a site of ongoing changes) were obscured on the September stereo photographs; however, the other two craters underwent noteworthy changes. In Crater 3, the front vent (3/3), which was essentially a pit in April, had become a small cone by September as a tephra apron enclosed the vent. In the westernmost part of Crater 3, vents 3/1 and 3/2 merged into a single chasm distinct from the rest of the crater.

Figure (see Caption) Figure 51. Sketches made from terrestrial stereo photographs shot on 25 April 1996 and 19 September 1996. View is towards the NW. The sketches allow comparison of morphological changes in the crater area between these two dates; vents and craters labeled 3/2? and 3/3? were inferred indirectly from ejecta trajectories; areas labeled "?" were obscured by particulate and gases. Courtesy of Jürg Alean (original photos by Alean and Carniel).

During the first half of August the activity increased at Crater 3, in particular at vent 3/1, where the magma rose to increasingly shallow levels. During 16--17 August 1996, amid vigorous seismicity (figure 52), local volcano guide Nino Zerilli saw a small lava flow discharged from vent 3/1. The lava flow proceeded for only a few meters inside the crater and stopped by the evening of 18 August. Around this same time interval magma also reached high levels in Crater 1.

On 22 August 1996 at 0230 a tourist was hit by volcanic ejecta while in a sleeping bag ~80 m from the crater. He had to be transported by helicopter to Messina for head surgery. Zerilli reported that during the previous days ejecta from Crater 3 had been thrown as far as observation sites between the Pizzo and Crater 3. Thus, this injury appeared to have been more a case of camping too close to the crater rather than an especially violent outburst that particular night.

By 26 August, vent 3/1 was completely inactive, whereas vents 3/2 and 3/3 had almost joined, and their activity consisted of very powerful Strombolian explosions sending small fragments onto the Pizzo. At Crater 1, vent 1/4 only rarely exploded but did so with strong gas jets. In contrast, vent 1/3 ceased the continuous activity that it had begun on 16 April 1996, a change interpreted as either another pause there or the end of an unusually long period of continuous spattering.

On 4 September 1996 at 1545 a blast threw incandescent pyroclastic material onto slope vegetation. This started several fires and the explosion was clearly heard and watched from the village of Stromboli. According to the local newspaper "Il Piccolo" some tourists were caught by the explosion in the crater area and six of them were slightly injured. After this, the Mayor of Lipari ordered the closure of the path to the craters. After the blast, however, Strombolian activity continued to decrease. In terms of seismicity, both the number of major events and the total number of events decreased to very low values, a situation which prevailed through the end of January 1997 (figure 52).

Figure (see Caption) Figure 52. Seismicity recorded at Stromboli 15 May 1996-31 January 1997. Open bars show the number of recorded events/day, and the solid bars those saturating the instrument (ground velocity exceeding 100 µm/s). The line shows daily tremor intensity computed by averaging hourly 60-second samples. The seismic station is 300 m from the craters at 800 m elevation. Arrows highlight the two powerful explosions of 1 June and 4 September 1996. Courtesy of R. Carniel.

A visit by Carniel at the end of September revealed extremely low activity as judged by the few audible eruptions seen or heard; however, smoke often covered most of the crater area. Remarkable were some very long rumbles, which could be heard even from the village of Stromboli. These rumbles were probably associated with strong degassing from Crater 2, although this interpretation remained unconfirmed by direct observation.

Matthias Hort and Ralf Seyfried visited and photographed portions of the volcano during 30 September-2 October (figures 53 and 51). They witnessed small eruptions from vent 2 at Crater 3. These eruptions took place while Craters 1 and 2 were inactive. Rumbling noises heard on 30 September from Crater 1 disappeared within the next two days. Overall, activity gradually declined from 30 September to 2 October. According to Hort, the most spectacular event during the observation period was an ash emission that produced a plume to 100 m above the craters. Periods of up to 2 hours passed without eruption.

Figure (see Caption) Figure 53. Ash and bomb emission from Crater 3 seen from Pizzo on 30 September 1996. Courtesy of Matthias Hort, GEOMAR.
Figure (see Caption) Figure 54. View of vent 1 in Crater 3, 30 September 1996. Bright incandescence is seen during daylight, indicating active magma at shallow depth. Courtesy of Matthias Hort, GEOMAR.

On the evening of 10 October Boris Behncke saw two lava fountains shooting up from Crater 3 during a 5- minute interval, reaching 80-100 m above the vent (to the height of Pizzo sopra la Fossa). Each fountain lasted ~20 seconds. About 10 minutes after the second fountain, an eruption apparently occurred at Crater 1.

Unusually low seismic activity appeared on 10 November, when the seismic station recorded only 17 events within 24 hours (none of them saturating the acquisition system). Exceptionally long intervals without a single event occurred on several other days: 7 hours on 25 October, 8 hours on 10 November, 10 hours during the night between 12 and 13 November. Although the tremor intensity slowly increased from September 1996 (1-2 V.s) to January 1997 (3-5 V.s), there was no significant increase in the number of recorded events or saturating events. Thus, activity at the end of January was still considered "low to moderate."

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

Information Contacts: Roberto Carniel, Dipartimento di Georisorse e Territorio, via Cotonificio 114, I-33100 Udine; Jürg Alean, Kantonsschule Zürcher Unterland, CH-8180 Bülach, Switzerland; Matthias Hort, Ralf Seyfried, and Boris Behncke, Geomar Research Center for Marine Geosciences, Wischhofstrasse 1-3, 24148 Kiel, Germany; Martin Scheele, Institut für Weltraumsensorik (Institute for Space Sensor Technology), Deutsche Forschungsanstalt für Luft- und Raumfahrt (German Aerospace Research Establishment), Forschungszentrum Berlin-Adlershof, Rudower Chaussee 5, 12489 Berlin (URL: http://www.dlr.de/).


Telica (Nicaragua) — March 1997 Citation iconCite this Report

Telica

Nicaragua

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

All times are local (unless otherwise noted)


Seismicity increases and fumarolic activity continues

On 27 February, during a visit to the summit crater, scientists noted continuing minor fumarolic activity with maximum temperatures of 300-350°C and an active collapse zone on the E crater rim (figure 10). At this time a portable seismic station recorded microearthquakes at 30-40 minute intervals. Night observations of the crater confirmed the absence of any incandescence.

Figure (see Caption) Figure 10. Sketch of the active crater at Telica indicating areas of fumarolic activity. Temperature is degrees C. Courtesy of Alain Creusot.

During March 1997, seismicity was high with about 150 seismic signals/day recorded. Seismicity levels increased from December 1996, when there were less than 100 signals/day. Most March events had frequencies of 1.5-4.6 Hz and durations of 9-40 seconds. Visits to the summit crater showed the presence of fresh ashfall, numerous small landslides inside the crater, and moderate fumarolic activity in the walls and floor of the crater. Scientists also measured Telica's gas emissions, thermal infrared signals, and microgravity. Small amounts of gas were emitted from fumaroles on the E and W crater walls; however, COSPEC measurements failed to detect any SO2, although local farmers smelled sulfur in the afternoon when the wind shifted to the W. Thus, the amount of released gas appeared to be less than in March 1996.

Fumaroles located along a NE-SW trending fracture near the seismic station outside the active crater had maximum temperatures of 85°C. Soil gas measurements made along the fracture on 11 March 1997 showed maximum CO2 concentrations of 3.2%. This fracture first appeared in September 1996.

Infrared camera measurements on 20 March 1997 detected a zone of high temperatures near the base of the W crater wall. This zone had temperatures up to 190°C. Since this was a remote measurement, it should be considered as a minimum estimate. The crater fumaroles were at a lower temperature than those at the base of the W crater wall. Minimum temperatures measured with the infrared camera were 58°C for fumaroles on the W side, 47°C for fumaroles on the N wall, and 107°C for fumaroles on the E wall.

On 20 March, gravity measurements with a Lacoste and Roberg meter near the crater measured a repetitive signal with a periodicity of about 18 seconds. Also, on 23 March, a large gas emission from the crater was visible at the seismic station.

An eruption on 31 July 1994 produced a gas-and-ash column to ~ 800 m above the summit; detectable ash fell as far as 17 km from the summit (BGVN 19:07). Phreatic explosions continued until 12 August 1994 when seismicity began decreasing (BGVN 19:09).

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

Information Contacts: Hazel Rymer and Mark Davies, Department of Earth Sciences, The Open University, Milton Keynes MK7 6AA, United Kingdom; John Stix, Dora Knez, Glyn Williams-Jones, and Alexandre Beaulieu, Departement de Geologie, Universite de Montreal, Montreal, Quebec H3C 3J7, Canada; Nicki Stevens, Department of Geography, University of Reading, Reading RG2 2AB, United Kingdom; Martha Navarro and Pedro Perez, INETER, Apartado Postal 2110, Managua, Nicaragua; Alain Creusot, Instituto Nicaraguense de Energía, Managua, Nicaragua

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


Central Chile and Argentina


Estero de Parraguirre


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/).