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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

Klyuchevskoy (Russia) Strombolian activity November 2019 through May 2020; lava flow down the SE flank in April

Nyamuragira (DR Congo) Intermittent thermal anomalies within the summit crater during December 2019-May 2020

Nyiragongo (DR Congo) Activity in the lava lake and small eruptive cone persists during December 2019-May 2020

Kavachi (Solomon Islands) Discolored water plumes seen using satellite imagery in 2018 and 2020

Kuchinoerabujima (Japan) Eruption and ash plumes begin on 11 January 2020 and continue through April 2020

Soputan (Indonesia) Minor ash emissions during 23 March and 2 April 2020

Heard (Australia) Eruptive activity including a lava flow during October 2019-April 2020

Kikai (Japan) Ash explosion on 29 April 2020

Fuego (Guatemala) Ongoing ash explosions, block avalanches, and intermittent lava flows

Ebeko (Russia) Frequent moderate explosions, ash plumes, and ashfall continue, December 2019-May 2020

Piton de la Fournaise (France) Fissure eruptions in February and April 2020 included lava fountains and flows

Sabancaya (Peru) Daily explosions with ash emissions, large SO2 flux, ongoing thermal anomalies, December 2019-May 2020



Klyuchevskoy (Russia) — June 2020 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Strombolian activity November 2019 through May 2020; lava flow down the SE flank in April

Klyuchevskoy is part of the Klyuchevskaya volcanic group in northern Kamchatka and is one of the most frequently active volcanoes of the region. Eruptions produce lava flows, ashfall, and lahars originating from summit and flank activity. This report summarizes activity during October 2019 through May 2020, and is based on reports by the Kamchatkan Volcanic Eruption Response Team (KVERT) and satellite data.

There were no activity reports from 1 to 22 October, but gas emissions were visible in satellite images. At 1020 on 24 October (2220 on 23 October UTC) KVERT noted that there was a small ash component in the ash plume from erosion of the conduit, with the plume reaching 130 km ENE. The Aviation Colour Code was raised from Green to Yellow, then to Orange the following day. An ash plume continued on the 25th to 5-7 km altitude and extending 15 km SE and 70 km SW and reached 30 km ESE on the 26th. Similar activity continued through to the end of the month.

Moderate gas emissions continued during 1-19 November, but the summit was obscured by clouds. Strong nighttime incandescence was visible at the crater during the 10-11 November and thermal anomalies were detected on 8 and 10-13 November. Explosions produced ash plumes up to 6 km altitude on the 20-21st and Strombolian activity was reported during 20-22 November. Degassing continued from 23 November through 12 December, and a thermal anomaly was visible on the days when the summit was not covered by clouds. An ash plume was reported moving to the NW on the 13th, and degassing with a thermal anomaly and intermittent Strombolian activity then resumed, continuing through to the end of December with an ash plume reported on the 30th.

Gas-and-steam plumes continued into January 2020 with incandescence noted when the summit was clear (figure 33). Strombolian activity was reported again starting on the 3rd. A weak ash plume produced on the 6th extended 55 km E, and on the 21st an ash plume reached 5-5.5 km altitude and extended 190 km NE (figure 34). Another ash plume the next day rose to the same altitude and extended 388 km NE. During 23-29 Strombolian activity continued, and Vulcanian activity produced ash plumes up to 5.5 altitude, extending to 282 km E on the 30th, and 145 km E on the 31st.

Figure (see Caption) Figure 33. Incandescence and degassing were visible at Klyuchevskoy through January 2020, seen here on the 11th. Courtesy of KVERT.
Figure (see Caption) Figure 34. A low ash plume at Klyuchevskoy on 21 January 2020 extended 190 km NE. Courtesy of KVERT.

Strombolian activity continued throughout February with occasional explosions producing ash plumes up to 5.5 km altitude, as well as gas-and-steam plumes and a persistent thermal anomaly with incandescence visible at night. Starting in late February thermal anomalies were detected much more frequently, and with higher energy output compared to the previous year (figure 35). A lava fountain was reported on 1 March with the material falling back into the summit crater. Strombolian activity continued through early March. Lava fountaining was reported again on the 8th with ejecta landing in the crater and down the flanks (figure 36). A strong persistent gas-and-steam plume containing some ash continued along with Strombolian activity through 25 March (figure 37), with Vulcanian activity noted on the 20th and 25th. Strombolian and Vulcanian activity was reported through the end of March.

Figure (see Caption) Figure 35. This MIROVA thermal energy plot for Klyuchevskoy for the year ending 29 April 2020 (log radiative power) shows intermittent thermal anomalies leading up to more sustained energy detected from February through March, then steadily increasing energy through April 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 36. Strombolian explosions at Klyuchevskoy eject incandescent ash and gas, and blocks and bombs onto the upper flanks on 8 and 10 March 2020. Courtesy of IVS FEB RAS, KVERT.
Figure (see Caption) Figure 37. Weak ash emission from the Klyuchevskoy summit crater are dispersed by wind on 19 and 29 March 2020, with ash depositing on the flanks. Courtesy of IVS FEB RAS, KVERT.

Activity was dominantly Strombolian during 1-5 April and included intermittent Vulcanian explosions from the 6th onwards, with ash plumes reaching 6 km altitude. On 18 April a lava flow began moving down the SE flank (figures 38). A report on the 26th reported explosions from lava-water interactions with avalanches from the active lava flow, which continued to move down the SE flank and into the Apakhonchich chute (figures 39 and 40). This continued throughout April and May with sustained Strombolian and intermittent Vulcanian activity at the summit (figures 41 and 42).

Figure (see Caption) Figure 38. Strombolian activity produced ash plumes and a lava flow down the SE flank of Klyuchevskoy on 18 April 2020. Courtesy of IVS FEB RAS, KVERT.
Figure (see Caption) Figure 39. A lava flow descends the SW flank of Klyuchevskoy and a gas plume is dispersed by winds on 21 April 2020. Courtesy of Yu. Demyanchuk, IVS FEB RAS, KVERT.
Figure (see Caption) Figure 40. Sentinel-2 thermal satellite images show the progression of the Klyuchevskoy lava flow from the summit crater down the SE flank from 19-29 April 2020. Associated gas plumes are dispersed in various directions. Courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 41. Strombolian activity at Klyuchevskoy ejects incandescent ejecta, gas, and ash above the summit on 27 April 2020. Courtesy of D. Bud'kov, IVS FEB RAS, KVERT.
Figure (see Caption) Figure 42. Sentinel-2 thermal satellite images of Klyuchevskoy show the progression of the SE flank lava flow through May 2020, with associated gas plumes being dispersed in multiple directions. Courtesy of Sentinel Hub Playground.

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: 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/); 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).


Nyamuragira (DR Congo) — June 2020 Citation iconCite this Report

Nyamuragira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


Intermittent thermal anomalies within the summit crater during December 2019-May 2020

Nyamuragira (also known as Nyamulagira) is located in the Virunga Volcanic Province (VVP) in the Democratic Republic of the Congo and consists of a lava lake that reappeared in the summit crater in mid-April 2018. Volcanism has been characterized by lava emissions, thermal anomalies, seismicity, and gas-and-steam emissions. This report summarizes activity during December 2019 through May 2020 using information from monthly reports by the Observatoire Volcanologique de Goma (OVG) and satellite data.

According to OVG, intermittent eruptive activity was detected in the lava lake of the central crater during December 2019 and January-April 2020, which also resulted in few seismic events. MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows thermal anomalies within the summit crater that varied in both frequency and power between August 2019 and mid-March 2020, but very few were recorded afterward through late May (figure 88). Thermal hotspots identified by MODVOLC from 15 December 2019 through March 2020 were mainly located in the active central crater, with only three hotspots just outside the SW crater rim (figure 89). Sentinel-2 thermal satellite imagery also showed activity within the summit crater during January-May 2020, but by mid-March the thermal anomaly had visibly decreased in power (figure 90).

Figure (see Caption) Figure 88. The MIROVA graph of thermal activity (log radiative power) at Nyamuragira during 27 July through May 2020 shows variably strong, intermittent thermal anomalies with a variation in power and frequency from August 2019 to mid-March 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 89. Map showing the number of MODVOLC hotspot pixels at Nyamuragira from 1 December 2019 t0 31 May 2020. 37 pixels were registered within the summit crater while 3 were detected just outside the SW crater rim. Courtesy of HIGP-MODVOLC Thermal Alerts System.
Figure (see Caption) Figure 90. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) confirmed ongoing thermal activity (bright yellow-orange) at Nyamuragira from February into April 2020. The strength of the thermal anomaly in the summit crater decreased by late March 2020, but was still visible. 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: 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/exp.


Nyiragongo (DR Congo) — June 2020 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Activity in the lava lake and small eruptive cone persists during December 2019-May 2020

Nyiragongo is located in the Virunga Volcanic Province (VVP) in the Democratic Republic of the Congo, part of the western branch of the East African Rift System and contains a 1.2 km-wide summit crater with a lava lake that has been active since at least 1971. Volcanism has been characterized by strong and frequent thermal anomalies, incandescence, gas-and-steam emissions, and seismicity. This report summarizes activity during December 2019 through May 2020 using information from monthly reports by the Observatoire Volcanologique de Goma (OVG) and satellite data.

In the December 2019 monthly report, OVG stated that the level of the lava lake had increased. This level of the lava lake was maintained for the duration of the reporting period, according to later OVG monthly reports. Seismicity increased starting in November 2019 and was detected in the NE part of the crater, but it decreased by mid-April 2020. SO2 emissions increased in January 2020 to roughly 7,000 tons/day but decreased again near the end of the month. OVG reported that SO2 emissions rose again in February to roughly 8,500 tons/day before declining to about 6,000 tons/day. Unlike in the previous report (BGVN 44:12), incandescence was visible during the day in the active lava lake and activity at the small eruptive cone within the 1.2-km-wide summit crater has since increased, consisting of incandescence and some lava fountaining (figure 72). A field survey was conducted on 3-4 March where an OVG team observed active lava fountains and ejecta that produced Pele’s hair from the small eruptive cone (figure 73). During this survey, OVG reported that the level of the lava lake had reached the second terrace, which was formed on 17 January 2002 and represents remnants of the lava lake at different eruption stages. There, the open surface lava lake was observed; gas-and-steam emissions accompanied both the active lava lake and the small eruptive cone (figures 72 and 73).

Figure (see Caption) Figure 72. Webcam image of Nyiragongo in February 2020 showing an open lava lake surface and incandescence from the active crater cone within the 1.2 km-wide summit crater visible during the day, accompanied by white gas-and-steam emissions. Courtesy of OVG (Rapport OVG February 2020).
Figure (see Caption) Figure 73. Webcam image of Nyiragongo on 4 March 2020 showing an open lava lake surface and incandescence from the active crater cone within the 1.2 km-wide summit crater visible during the day, accompanied by white gas-and-steam emissions. Courtesy of OVG (Rapport OVG Mars 2020).

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data continued to show frequent strong thermal anomalies within 5 km of the summit crater through May 2020 (figure 74). Similarly, the MODVOLC algorithm reported multiple thermal hotspots almost daily within the summit crater between December 2019 and May 2020. These thermal signatures were also observed in Sentinel-2 thermal satellite imagery within the summit crater (figure 75).

Figure (see Caption) Figure 74. Thermal anomalies at Nyiragongo from 27 July through May 2020 as recorded by the MIROVA system (Log Radiative Power) were frequent and strong. Courtesy of MIROVA.
Figure (see Caption) Figure 75. Sentinel-2 thermal satellite imagery (bands 12, 11, 8A) showed ongoing thermal activity (bright yellow-orange) in the summit crater at Nyiragongo during January through April 2020. Courtesy of Sentinel Hub Playground.

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).


Kavachi (Solomon Islands) — May 2020 Citation iconCite this Report

Kavachi

Solomon Islands

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

All times are local (unless otherwise noted)


Discolored water plumes seen using satellite imagery in 2018 and 2020

Kavachi is a submarine volcano located in the Solomon Islands south of Gatokae and Vangunu islands. Volcanism is frequently active, but rarely observed. The most recent eruptions took place during 2014, which consisted of an ash eruption, and during 2016, which included phreatomagmatic explosions (BGVN 42:03). This reporting period covers December 2016-April 2020 primarily using satellite data.

Activity at Kavachi is often only observed through satellite images, and frequently consists of discolored submarine plumes for which the cause is uncertain. On 1 January 2018 a slight yellow discoloration in the water is seen extending to the E from a specific point (figure 20). Similar faint plumes were observed on 16 January, 25 February, 2 March, 26 April, 6 May, and 25 June 2018. No similar water discoloration was noted during 2019, though clouds may have obscured views.

Figure (see Caption) Figure 20. Satellite images from Sentinel-2 revealed intermittent faint water discoloration (yellow) at Kavachi during the first half of 2018, as seen here on 1 January (top left), 25 February (top right), 26 April (bottom left), and 25 June (bottom right). Images with “Natural color” rendering (bands 4, 3, 2); courtesy of Sentinel Hub Playground.

Activity resumed in 2020, showing more discolored water in satellite imagery. The first instance occurred on 16 March, where a distinct plume extended from a specific point to the SE. On 25 April a satellite image showed a larger discolored plume in the water that spread over about 30 km2, encompassing the area around Kavachi (figure 21). Another image on 30 April showed a thin ribbon of discolored water extending about 50 km W of the vent.

Figure (see Caption) Figure 21. Sentinel-2 satellite images of a discolored plume (yellow) at Kavachi beginning on 16 March (top left) with a significant large plume on 25 April (right), which remained until 30 April (bottom left). Images with “Natural color” rendering (bands 4, 3, 2); courtesy of Sentinel Hub Playground.

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

Information Contacts: Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Kuchinoerabujima (Japan) — May 2020 Citation iconCite this Report

Kuchinoerabujima

Japan

30.443°N, 130.217°E; summit elev. 657 m

All times are local (unless otherwise noted)


Eruption and ash plumes begin on 11 January 2020 and continue through April 2020

Kuchinoerabujima encompasses a group of young stratovolcanoes located in the northern Ryukyu Islands. All historical eruptions have originated from the Shindake cone, with the exception of a lava flow that originated from the S flank of the Furudake cone. The most recent previous eruptive period took place during October 2018-February 2019 and primarily consisted of weak explosions, ash plumes, and ashfall. The current eruption began on 11 January 2020 after nearly a year of dominantly gas-and-steam emissions. Volcanism for this reporting period from March 2019 to April 2020 included explosions, ash plumes, SO2 emissions, and ashfall. The primary source of information for this report comes from monthly and annual reports from the Japan Meteorological Agency (JMA) and advisories from the Tokyo Volcanic Ash Advisory Center (VAAC). Activity has been limited to Kuchinoerabujima's Shindake Crater.

Volcanism at Kuchinoerabujima was relatively low during March through December 2019, according to JMA. During this time, SO2 emissions ranged from 100 to 1,000 tons/day. Gas-and-steam emissions were frequently observed throughout the entire reporting period, rising to a maximum height of 1.1 km above the crater on 13 December 2019. Satellite imagery from Sentinel-2 showed gas-and-steam and occasional ash emissions rising from the Shindake crater throughout the reporting period (figure 7). Though JMA reported thermal anomalies occurring on 29 January and continuing through late April 2020, Sentinel-2 imagery shows the first thermal signature appearing on 26 April.

Figure (see Caption) Figure 7. Sentinel-2 thermal satellite images showed gas-and-steam and ash emissions rising from Kuchinoerabujima. Some ash deposits can be seen on 6 February 2020 (top right). A thermal anomaly appeared on 26 April 2020 (bottom right). Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.

An eruption on 11 January 2020 at 1505 ejected material 300 m from the crater and produced ash plumes that rose 2 km above the crater rim, extending E, according to JMA. The eruption continued through 12 January until 0730. The resulting ash plumes rose 400 m above the crater, drifting SW while the SO2 emissions measured 1,300 tons/day. Ashfall was reported on Yakushima Island (15 km E). Minor eruptive activity was reported during 17-20 January which produced gray-white plumes that rose 300-500 m above the crater. On 23 January, seismicity increased, and an eruption produced an ash plume that rose 1.2 km altitude, according to a Tokyo VAAC report, resulting in ashfall 2 km NE of the crater. A small explosion was detected on 24 January, followed by an increase in the number of earthquakes during 25-26 January (65-71 earthquakes per day were registered). Another small eruptive event detected on 27 January at 0148 was accompanied by a volcanic tremor and a change in tilt data. During the month of January, some inflation was detected at the base on the volcano and a total of 347 earthquakes were recorded. The SO2 emissions ranged from 200-1,600 tons/day.

An eruption on 1 February 2020 produced an eruption column that rose less than 1 km altitude and extended SE and SW (figure 8), according to the Tokyo VAAC report. On 3 February, an eruption from the Shindake crater at 0521 produced an ash plume that rose 7 km above the crater and ejected material as far as 600 m away. As a result, a pyroclastic flow formed, traveling 900-1,500 m SW. The previous pyroclastic flow that was recorded occurred on 29 January 2019. Ashfall was confirmed in the N part of Yakushima Island with a large amount in Miyanoura (32 km ESE) and southern Tanegashima. The SO2 emissions measured 1,700 tons/day during this event.

Figure (see Caption) Figure 8. Webcam images from the Honmura west surveillance camera of an ash plume rising from Kuchinoerabujima on 1 February 2020. Courtesy of JMA (Weekly bulletin report 509, February 2020).

Intermittent small eruptive events occurred during 5-9 February; field observations showed a large amount of ashfall on the SE flank which included lapilli that measured up to 2 cm in diameter. Additionally, thermal images showed 5-km-long pyroclastic flow deposits on the SW flank. An eruption on 9 February produced an ash plume that rose 1.2 km altitude, drifting SE. On 13 February a small eruption was detected in the Shindake crater at 1211, producing gray-white plumes that rose 300 m above the crater, drifting NE. Small eruptive events also occurred during 20-21 February, resulting in gas-and-steam emissions that rose 200 m above the crater. During the month of February, some horizontal extension was observed since January 2020 using GNSS data. The total number of earthquakes during this month drastically increased to 1225 compared to January. The SO2 emissions ranged from 300-1,700 tons/day.

By 2 March 2020, seismicity decreased, and activity declined. Gas-and-steam emissions continued infrequently for the duration of the reporting period. The SO2 emissions during March ranged from 700-2,100 tons/day, the latter of which occurred on 15 March. Seismicity increased again on 27 March. During 5-8 April 2020, small eruptive events were detected, generating ash plumes that rose 900 m above the crater (figure 9). The SO2 emissions on 6 April reached 3,200 tons/day, the maximum measurement for this reporting period. These small eruptive events continued from 13-20 and 23-25 April within the Shindake crater, producing gray-white plumes that rose 300-800 m above the crater.

Figure (see Caption) Figure 9. Webcam images from the Honmura Nishi (top) and Honmura west (bottom) surveillance cameras of ash plumes rising from Kuchinoerabujima on 6 March and 5 April 2020. Courtesy of JMA (Weekly bulletin report 509, March and April 2020).

Geologic Background. A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyu Islands, 15 km W of Yakushima. The Furudake, Shindake, and Noikeyama cones were erupted from south to north, respectively, forming a composite cone with multiple craters. The youngest cone, centrally-located Shindake, formed after the NW side of Furudake was breached by an explosion. All historical eruptions have occurred from Shindake, although a lava flow from the S flank of Furudake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shindake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.

Information Contacts: Japan Meteorological Agency (JMA), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo 100-8122, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Soputan (Indonesia) — May 2020 Citation iconCite this Report

Soputan

Indonesia

1.112°N, 124.737°E; summit elev. 1785 m

All times are local (unless otherwise noted)


Minor ash emissions during 23 March and 2 April 2020

Soputan is a stratovolcano located in the northern arm of Sulawesi Island, Indonesia. Previous eruptive periods were characterized by ash explosions, lava flows, and Strombolian eruptions. The most recent eruption occurred during October-December 2018, which consisted mostly of ash plumes and some summit incandescence (BGVN 44:01). This report updates information for January 2019-April 2020 characterized by two ash plumes and gas-and-steam emissions. The primary source of information come from the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and the Darwin Volcanic Ash Advisory Center (VAAC).

Activity during January 2019-April 2020 was relatively low; three faint thermal anomalies were observed at the summit at Soputan in satellite imagery for a total of three days on 2 and 4 January, and 1 October 2019 (figure 17). The MIROVA (Middle InfraRed Observation of Volcanic Activity) based on analysis of MODIS data detected 12 distal hotspots and six low-power hotspots within 5 km of the summit during August to early October 2019. A single distal thermal hotspot was detected in early March 2020. In March, activity primarily consisted of white to gray gas-and-steam plumes that rose 20-100 m above the crater, according to PVMBG. The Darwin VAAC issued a notice on 23 March 2020 that reported an ash plume rose to 4.3 km altitude; minor ash emissions had been visible in a webcam image the previous day (figure 18). A second notice was issued on 2 April, where an ash plume was observed rising 2.1 km altitude and drifting W.

Figure (see Caption) Figure 17. Sentinel-2 thermal satellite imagery detected a total of three thermal hotspots (bright yellow-orange) at the summit of Soputan on 2 and 4 January and 1 October 2019. Sentinel-2 atmospheric penetration (bands 12, 11, 8A) images courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 18. Minor ash emissions were seen rising from Soputan on 22 March 2020. Courtesy of MAGMA Indonesia.

Geologic Background. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano is located SW of Riendengan-Sempu, which some workers have included with Soputan and Manimporok (3.5 km ESE) as a volcanic complex. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.

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/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Heard (Australia) — May 2020 Citation iconCite this Report

Heard

Australia

53.106°S, 73.513°E; summit elev. 2745 m

All times are local (unless otherwise noted)


Eruptive activity including a lava flow during October 2019-April 2020

Heard Island is located on the Kerguelen Plateau in the southern Indian Ocean and contains Big Ben, a snow-covered stratovolcano with intermittent volcanism reported since 1910. Due to its remote location, visual observations are rare; therefore, thermal anomalies and hotspots detected by satellite-based instruments are the primary source of information. This report updates activity from October 2019 to April 2020.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed three prominent periods of strong thermal anomaly activity during this reporting period: late October 2019, December 2019, and the end of April 2020 (figure 41). These thermal anomalies were relatively strong and occurred within 5 km of the summit. Similarly, the MODVOLC algorithm reported a total of six thermal hotspots during 28 October, 1 November 2019, and 26 April 2020.

Figure (see Caption) Figure 41. Thermal anomalies at Heard from 29 April 2019 through April 2020 as recorded by the MIROVA system (Log Radiative Power) were strong and frequent in late October, during December 2019, and at the end of April 2020. Courtesy of MIROVA.

Six thermal satellite images ranging from late October 2019 to late March showed evidence of active lava at the summit (figure 42). These images show hot material, possibly a lava flow, extending SW from the summit; a hotspot also remained at the summit. Cloud cover was pervasive during the majority of this reporting period, especially in April 2020, though gas-and-steam emissions were visible on 25 April through the clouds.

Figure (see Caption) Figure 42. Thermal satellite images of Heard Island’s Big Ben showing strong thermal signatures representing a lava flow in the SW direction from 28 October to 17 December 2019. These thermal anomalies are located NE from Mawson Peak. A faint thermal anomaly is also captured on 26 March 2020. Satellite images with atmospheric penetration (bands 12, 11, and 8A), courtesy of Sentinel Hub Playground.

Geologic Background. Heard Island on the Kerguelen Plateau in the southern Indian Ocean consists primarily of the emergent portion of two volcanic structures. The large glacier-covered composite basaltic-to-trachytic cone of Big Ben comprises most of the island, and the smaller Mt. Dixon lies at the NW tip of the island across a narrow isthmus. Little is known about the structure of Big Ben because of its extensive ice cover. The historically active Mawson Peak forms the island's high point and lies within a 5-6 km wide caldera breached to the SW side of Big Ben. Small satellitic scoria cones are mostly located on the northern coast. Several subglacial eruptions have been reported at this isolated volcano, but observations are infrequent and additional activity may have occurred.

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


Kikai (Japan) — May 2020 Citation iconCite this Report

Kikai

Japan

30.793°N, 130.305°E; summit elev. 704 m

All times are local (unless otherwise noted)


Ash explosion on 29 April 2020

The Kikai caldera is located at the N end of Japan’s Ryukyu Islands and has been recently characterized by intermittent ash emissions and limited ashfall in nearby communities. On Satsuma Iwo Jima island, the larger subaerial fragment of the Kikai caldera, there was a single explosion with gas-and-steam and ash emissions on 2 November 2019, accompanied by nighttime incandescence (BGVN 45:02). This report covers volcanism from January 2020 through April 2020 with a single-day eruption occurring on 29 April based on reports from the Japan Meteorological Agency (JMA).

Since the last one-day eruption on 2 November 2019, volcanism at Kikai has been relatively low and primarily consisted of 107-170 earthquakes per month and intermittent white gas-and-steam emissions rising up to 1.3 km above the crater summit. Intermittent weak hotspots were observed at night in the summit in Sentinel-2 thermal satellite imagery and webcams, according to JMA (figures 14 and 15).

Figure (see Caption) Figure 14. Weak thermal hotspots (bright yellow-orange) were observed on 7 January (top) and 6 April 2020 (bottom) at Satsuma Iwo Jima (Kikai). Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 15. Incandescence at night on 10 January 2020 was observed at Satsuma Iwo Jima (Kikai) in the Iodake crater with the Iwanogami webcam. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, January 2nd year of Reiwa [2020]).

Weak incandescence continued in April 2020. JMA reported SO2 measurements during April were 400-2000 tons/day. A brief eruption in the Iodake crater on 29 April 2020 at 0609 generated a gray-white ash plume that rose 1 km above the crater (figure 16). No ashfall or ejecta was observed after the eruption on 29 April.

Figure (see Caption) Figure 16. The Iwanogami webcam captured a brief gray-white ash and steam plume rising above the Iodake crater rim on Satsuma Iwo Jima (Kikai) on 29 April 2020 at 0609 local time. The plume rose 1 km above the crater summit. Courtesy of JMA (An explanation of volcanic activity at Satsuma Iwo Jima, April 2nd year of Reiwa [2020]).

Geologic Background. Kikai is a mostly submerged, 19-km-wide caldera near the northern end of the Ryukyu Islands south of Kyushu. It was the source of one of the world's largest Holocene eruptions about 6,300 years ago when rhyolitic pyroclastic flows traveled across the sea for a total distance of 100 km to southern Kyushu, and ashfall reached the northern Japanese island of Hokkaido. The eruption devastated southern and central Kyushu, which remained uninhabited for several centuries. Post-caldera eruptions formed Iodake lava dome and Inamuradake scoria cone, as well as submarine lava domes. Historical eruptions have occurred at or near Satsuma-Iojima (also known as Tokara-Iojima), a small 3 x 6 km island forming part of the NW caldera rim. Showa-Iojima lava dome (also known as Iojima-Shinto), a small island 2 km E of Tokara-Iojima, was formed during submarine eruptions in 1934 and 1935. Mild-to-moderate explosive eruptions have occurred during the past few decades from Iodake, a rhyolitic lava dome at the eastern end of Tokara-Iojima.

Information Contacts: Japan Meteorological Agency (JMA), Otemachi, 1-3-4, Chiyoda-ku Tokyo 100-8122, Japan (URL: http://www.jma.go.jp/jma/indexe.html); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Fuego (Guatemala) — April 2020 Citation iconCite this Report

Fuego

Guatemala

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

All times are local (unless otherwise noted)


Ongoing ash explosions, block avalanches, and intermittent lava flows

Fuego is a stratovolcano in Guatemala that has been erupting since 2002 with historical eruptions that date back to 1531. Volcanism is characterized by major ashfalls, pyroclastic flows, lava flows, and lahars. The previous report (BGVN 44:10) detailed activity that included multiple ash explosions, ash plumes, ashfall, active lava flows, and block avalanches. This report covers this continuing activity from October 2019 through March 2020 and consists of ash plumes, ashfall, incandescent ejecta, block avalanches, and lava flows. The primary source of information comes from the Instituto Nacional de Sismologia, Vulcanología, Meteorología e Hidrologia (INSIVUMEH), the Washington Volcanic Ash Advisory Center (VAAC), and various satellite data.

Summary of activity October 2019-March 2020. Daily activity persisted throughout October 2019-March 2020 (table 20) with multiple ash explosions recorded every hour, ash plumes that rose to a maximum of 4.8 km altitude each month drifting in multiple directions, incandescent ejecta reaching a 500 m above the crater resulting in block avalanches traveling down multiple drainages, and ashfall affecting communities in multiple directions. The highest rate of explosions occurred on 7 November with up to 25 per hour. Dominantly white fumaroles occurred frequently throughout this reporting period, rising to a maximum altitude of 4.5 km and drifting in multiple directions. Intermittent lava flows that reached a maximum length of 1.2 km were observed each month in the Seca (Santa Teresa) and Ceniza drainages (figure 128), but rarely in the Trinidad drainage. Thermal activity increased slightly in frequency and strength in late October and remained relatively consistent through mid-March as seen in the MIROVA analysis of MODIS satellite data (figure 129).

Table 20. Activity summary by month for Fuego with information compiled from INSIVUMEH daily reports.

Month Ash plume heights (km) Ash plume distance (km) and direction Drainages affected by avalanche blocks Villages reporting ashfall
Oct 2019 4.3-4.8 km 10-25 km, W-SW-S-NW Seca, Taniluyá, Ceniza, Trinidad, El Jute, Honda, and Las Lajas Panimaché I and II, Morelia, Santa Sofía, Porvenir, Finca Palo Verde, La Rochela, San Andrés Osuna, Sangre de Cristo, and San Pedro Yepocapa
Nov 2019 4.0-4.8 km 10-20 km, W-SW-S-NW Seca, Taniluyá, Trinidad, Las Lajas, Honda, and Ceniza Panimaché I and II, Morelia, Santa Sofía, Porvenir, Sangre de Cristo, Finca Palo Verde, and San Pedro Yepocapa
Dec 2019 4.2-4.8 km 10-25 km, W-SW-S-SE-N-NE Seca, Taniluya, Ceniza, Trinidad, and Las Lajas Morelia, Santa Sofía, Finca Palo Verde, El Porvenir, Sangre de Cristo, San Pedro Yepocapa, Panimaché I and II, La Rochela, and San Andrés Osuna
Jan 2020 4.3-4.8 km 10-25 km, W-SW-S-N-NE-E Seca, Ceniza, Taniluyá, Trinidad, Honda, and Las Lajas Morelia, Santa Sofía, Sangre de Cristo, San Pedro Yepocapa, Panimaché I and II, El Porvenir, Finca Palo Verde, Rodeo, La Rochela, Alotenango, El Zapote, Trinidad, La Reina, Ceilán
Feb 2020 4.3-4.8 km 8-25 km, W-SW-S-SE-E-NE-N-NW Seca, Ceniza, Taniluya, Trinidad, Las Lajas, Honda, La Rochela, El Zapote, and San Andrés Osuna Panimache I and II, Morelia, Santa Sofia, Sangre de Cristo, San Pedro Yepocapa, Rodeo, La Reina, Alotenango, Yucales, Siquinalá, Santa Lucia, El Porvenir, Finca Los Tarros, La Soledad, Buena Vista, La Cruz, Pajales, San Miguel Dueñas, Ciudad Vieja, San Miguel Escobar, San Pedro las Huertas, Antigua, La Rochela, and San Andrés Osuna
Mar 2020 4.3-4.8 km 10-23 km, W-SW-S-SE-N-NW Seca, Ceniza, Trinidad, Taniluyá, Las Lajas, Honda, La Rochela, El Zapote, San Andrés Osuna, Morelia, Panimache, and Santa Sofia San Andrés Osuna, La Rochela, El Rodeo, Chuchu, Panimache I and II, Santa Sofia, Morelia, Finca Palo Verde, El Porvenir, Sangre de Cristo, La Cruz, San Pedro Yepocapa, La Conchita, La Soledad, Alotenango, Aldea la Cruz, Acatenango, Ceilan, Taniluyá, Ceniza, Las Lajas, Trinidad, Seca, and Honda
Figure (see Caption) Figure 128. Sentinel-2 thermal satellite images of Fuego between 21 November 2019 and 20 March 2020 showing lava flows (bright yellow-orange) traveling generally S and W from the crater summit. An ash plume can also be seen on 21 November 2019, accompanying the lava flow. Sentinel-2 satellite images with “Atmospheric penetration” (bands 12, 11, 8A) rendering; courtesy of Sentinel Hub Playground.
Figure (see Caption) Figure 129. Thermal activity at Fuego increased in frequency and strength (log radiative power) in late October 2019 and remained relatively consistent through February 2020. In early March, there is a small decrease in thermal power, followed by a short pulse of activity and another decline. Courtesy of MIROVA.

Activity during October-December 2019. Activity in October 2019 consisted of 6-20 ash explosions per hour; ash plumes rose to 4.8 km altitude, drifting up to 25 km in multiple directions, resulting in ashfall in Panimaché I and II (8 km SW), Morelia (9 km SW), San Pedro Yepocapa (8 km NW), Sangre de Cristo (8 km WSW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), Finca Palo Verde, La Rochela and San Andrés Osuna. The Washington VAAC issued multiple aviation advisories for a total of nine days in October. Continuous white gas-and-steam plumes reached 4.1-4.4 km altitude drifting generally W. Weak SO2 emissions were infrequently observed in satellite imagery during October and January 2020 (figure 130) Incandescent ejecta was frequently observed rising 200-400 m above the summit, which generated block avalanches that traveled down the Seca (W), Taniluyá (SW), Ceniza (SSW), Trinidad (S), El Jute, Honda, and Las Lajas (SE) drainages. During 3-7 October lahars descended the Ceniza, El Mineral, and Seca drainages, carrying tree branches, tree trunks, and blocks 1-3 m in diameter. During 6-8 and 13 October, active lava flows traveled up to 200 m down the Seca drainage.

Figure (see Caption) Figure 130. Weak SO2 emissions were observed rising from Fuego using the TROPOMI instrument on the Sentinel-5P satellite. Top left: 17 October 2019. Top right: 17 November 2019. Bottom left: 20 January 2020. Bottom right: 22 January 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

During November 2019, the rate of explosions increased to 5-25 per hour, the latter of which occurred on 7 November. The explosions resulted in ash plumes that rose 4-4.8 km altitude, drifting 10-20 km in the W direction. Ashfall was observed in Panimaché I and II, Morelia, Santa Sofía, Porvenir, Sangre de Cristo, Finca Palo Verde, and San Pedro Yepocapa. Multiple Washington VAAC notices were issued for 11 days in November. Continuous white gas-and-steam plumes rose up to 4.5 km altitude drifting generally W. Incandescent ejecta rose 100-500 m above the crater, generating block avalanches in Seca, Taniluyá, Trinidad, Las Lajas, Honda, and Ceniza drainages. Lava flows were observed for a majority of the month into early December measuring 100-900 m long in the Seca and Ceniza drainages.

The number of explosions in December 2019 decreased compared to November, recording 8-19 per hour with incandescent ejecta rising 100-400 m above the crater. The explosions generated block avalanches that traveled in the Seca, Taniluya, Ceniza, Trinidad, and Las Lajas drainages throughout the month. Ash plumes continued to rise above the summit crater to 4.8 km drifting up to 25 km in multiple directions. The Washington VAAC issued multiple daily notices almost daily in December. A continuous lava flow observed during 6-15, 21-22, 24, and 26 November through 9 December measured 100-800 m long in the Seca and Ceniza drainages.

Activity during January-March 2020. Incandescent Strombolian explosions continued daily during January 2020, ejecting material up to 100-500 m above the crater. Ash plumes continued to rise to a maximum altitude of 4.8 km, resulting in ashfall in all directions affecting Morelia, Santa Sofía, Sangre de Cristo, San Pedro Yepocapa, Panimaché I and II, El Porvenir, Finca Palo Verde, Rodeo, La Rochela, Alotenango, El Zapote, Trinidad, La Reina, and Ceilán. The Washington VAAC issued multiple notices for a total of 12 days during January. Block avalanches resulting from the Strombolian explosions traveled down the Seca, Ceniza, Taniluyá, Trinidad, Honda, and Las Lajas drainages. An active lava flow in the Ceniza drainage measured 150-600 m long during 6-10 January.

During February 2020, INSIVUMEH reported a range of 4-16 explosions per hour, accompanied by incandescent material that rose 100-500 m above the crater (figure 131). Block avalanches traveled in the Santa Teresa, Seca, Ceniza, Taniluya, Trinidad, Las Lajas, Honda, La Rochela, El Zapote, and San Andrés Osuna drainages. Ash emissions from the explosions continued to rise 4.8 km altitude, drifting in multiple directions as far as 25 km and resulting in ashfall in the communities of Panimache I and II, Morelia, Santa Sofia, Sangre de Cristo, San Pedro Yepocapa, Rodeo, La Reina, Alotenango, Yucales, Siquinalá, Santa Lucia, El Porvenir, Finca Los Tarros, La Soledad, Buena Vista, La Cruz, Pajales, San Miguel Dueñas, Ciudad Vieja, San Miguel Escobar, San Pedro las Huertas, Antigua, La Rochela, and San Andrés Osuna. Washington VAAC notices were issued almost daily during the month. Lava flows were active in the Ceniza drainage during 13-20, 23-24, and 26-27 February measuring as long as 1.2 km.

Figure (see Caption) Figure 131. Incandescent ejecta rose several hundred meters above the crater of Fuego on 6 February 2020, resulting in block avalanches down multiple drainages. Courtesy of Crelosa.

Daily explosions and incandescent ejecta continued through March 2020, with 8-17 explosions per hour that rose up to 500 m above the crater. Block avalanches from the explosions were observed in the Seca, Ceniza, Trinidad, Taniluyá, Las Lajas, Honda, Santa Teresa, La Rochela, El Zapote, San Andrés Osuna, Morelia, Panimache, and Santa Sofia drainages. Accompanying ash plumes rose 4.8 km altitude, drifting in multiple directions mostly to the W as far as 23 km and resulting in ashfall in San Andrés Osuna, La Rochela, El Rodeo, Chuchu, Panimache I and II, Santa Sofia, Morelia, Finca Palo Verde, El Porvenir, Sangre de Cristo, La Cruz, San Pedro Yepocapa, La Conchita, La Soledad, Alotenango, Aldea la Cruz, Acatenango, Ceilan, Taniluyá, Ceniza, Las Lajas, Trinidad, Seca, and Honda. Multiple Washington VAAC notices were issued for a total of 15 days during March. Active lava flows were observed from 16-21 March in the Trinidad and Ceniza drainages measuring 400-1,200 m long and were accompanied by weak to moderate explosions. By 23 March, active lava flows were no longer observed.

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); 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); 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/); 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, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Crelosa, 3ra. avenida. 8-66, Zona 14. Colonia El Campo, Guatemala Ciudad de Guatemala (URL: http://crelosa.com/, post at https://www.youtube.com/watch?v=1P4kWqxU2m0&feature=youtu.be).


Ebeko (Russia) — June 2020 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, December 2019-May 2020

The current moderate explosive eruption of Ebeko has been ongoing since October 2016, with frequent ash explosions that have reached altitudes of 1.3-6 km (BGVN 42:08, 43:03, 43:06, 43:12, 44:12). Ashfall is common in Severo-Kurilsk, a town of about 2,500 residents 7 km ESE, where the Kamchatka Volcanic Eruptions Response Team (KVERT) monitor the volcano. During the reporting period, December 2019-May 2020, the Aviation Color Code remained at Orange (the second highest level on a four-color scale).

During December 2019-May 2020, frequent explosions generated ash plumes that reached altitudes of 1.5-4.6 km (table 9); reports of ashfall in Severo-Kurilsk were common. Ash explosions in late April caused ashfall in Severo-Kurilsk during 25-30 April (figure 24), and the plume drifted 180 km SE on the 29th. There was also a higher level of activity during the second half of May (figure 25), when plumes drifted up to 80 km downwind.

Table 9. Summary of activity at Ebeko, December 2019-May 2020. S-K is Severo-Kurilsk (7 km ESE of the volcano). TA is thermal anomaly in satellite images. In the plume distance column, only plumes that drifted more than 10 km are indicated. Dates based on UTC times. Data courtesy of KVERT.

Date Plume Altitude (km) Plume Distance Plume Directions Other Observations
30 Nov-05 Dec 2019 3 -- NE, E Intermittent explosions.
06-13 Dec 2019 4 -- E Explosions all week. Ashfall in S-K on 10-12 Dec.
15-17 Dec 2019 3 -- E Explosions. Ashfall in S-K on 16-17 Dec.
22-24 Dec 2019 3 -- NE Explosions.
01-02 Jan 2020 3 30 km N N Explosions. TA over dome on 1 Jan.
03, 05, 09 Jan 2020 2.9 -- NE, SE Explosions. Ashfall in S-K on 8 Jan.
11, 13-14 Jan 2020 3 -- E Explosions. Ashfall in S-K.
19-20 Jan 2020 3 -- E Ashfall in S-K on 19 Jan.
24-31 Jan 2020 4 -- E Explosions.
01-07 Feb 2020 3 -- E, S Explosions all week.
12-13 Feb 2020 1.5 -- E Explosions. Ashfall in S-K.
18-19 Feb 2020 2.3 -- SE Explosions.
21, 25, 27 Feb 2020 2.9 -- S, SE, NE Explosions. Ashfall in S-K on 22 Feb.
01-02, 05 Mar 2020 2 -- S, E Explosions.
08 Mar 2020 2.5 -- NE Explosions.
13, 17 Mar 2020 2.5 -- NE, SE Bursts of gas, steam, and small amount of ash.
24-25 Mar 2020 2.5 -- NE, W Explosions.
29 Mar-02 Apr 2020 2.2 -- NE, E Explosions. Ashfall in S-K on 1 Apr. TA on 30-31 Mar.
04-05, 09 Apr 2020 1.5 -- NE Explosions. TA on 5 Apr.
13 Apr 2020 2.5 -- SE Explosions.
18, 20 Apr 2020 -- -- -- TA on 18, 20 Apr.
24 Apr-01 May 2020 3.5 180 km SE on 29 Apr E, SE Explosions all week. Ashfall in S-K on 25-30 Apr.
01-08 May 2020 2.6 -- E Explosions all week. Ashfall in S-K on 3-5 May. TA on 3 May.
08-15 May 2020 4 -- E Explosions. Ashfall in S-K on 8-12 May. TA during 12-14 May.
14-15, 19-21 May 2020 3.6 80 km SW, S, SE during 14, 20-21 May -- Explosions. TA on same days.
22-29 May 2020 4.6 60 km SE E, SE Explosions all week. Ashfall in S-K on 22, 24 May.
29-31 May 2020 4.5 -- E, S Explosions. TA on 30 May.
Figure (see Caption) Figure 24. Photo of ash explosion at Ebeko at 2110 UTC on 28 April 2020, as viewed from Severo-Kurilsk. Courtesy of KVERT (L. Kotenko).
Figure (see Caption) Figure 25. Satellite image of Ebeko from Sentinel-2 on 27 May 2020, showing a plume drifting SE. Image using natural color rendering (bands 4, 3, 2) courtesy of Sentinel Hub Playground.

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).


Piton de la Fournaise (France) — May 2020 Citation iconCite this Report

Piton de la Fournaise

France

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

All times are local (unless otherwise noted)


Fissure eruptions in February and April 2020 included lava fountains and flows

Piton de la Fournaise is a massive basaltic shield volcano on the French island of Réunion in the western Indian Ocean. Recent volcanism is characterized by multiple fissure eruptions, lava fountains, and lava flows (BGVN 44:11). The activity during this reporting period of November 2019-April 2020 is consistent with the previous eruption, including lava fountaining and lava flows. Information for this report comes from the Observatoire Volcanologique du Piton de la Fournaise (OVPF) and various satellite data.

Activity during November 2019-January 2020 was relatively low; no eruptive events were detected, according to OVPF. Edifice deformation resumed during the last week in December and continued through January. Seismicity significantly increased in early January, registering 258 shallow earthquakes from 1-16 January. During 17-31 January, the seismicity declined, averaging one earthquake per day.

Two eruptive events took place during February-April 2020. OVPF reported that the first occurred from 10 to 16 February on the E and SE flanks of the Dolomieu Crater. The second took place during 2-6 April. Both eruptive events began with a sharp increase in seismicity accompanied by edifice inflation, followed by a fissure eruption that resulted in lava fountains and lava flows (figure 193). MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data showed the two eruptive events occurring during February-April 2020 (figure 194). Similarly, the MODVOLC algorithm reported 72 thermal signatures proximal to the summit crater from 12 February to 6 April. Both of these eruptive events were accompanied by SO2 emissions that were detected by the Sentinel-5P/TROPOMI instrument (figures 195 and 196).

Figure (see Caption) Figure 193. Location maps of the lava flows on the E flank at Piton de la Fournaise on 10-16 February 2020 (left) and 2-6 April 2020 (right) as derived from SAR satellite data. Courtesy of OVPF-IPGP, OPGC, LMV (Monthly bulletins of the Piton de la Fournaise Volcanological Observatory, February and April 2020).
Figure (see Caption) Figure 194. Two significant eruptive events at Piton de la Fournaise took place during February-April 2020 as recorded by the MIROVA system (Log Radiative Power). Courtesy of MIROVA.
Figure (see Caption) Figure 195. Images of the SO2 emissions during the February 2020 eruptive event at Piton de la Fournaise detected by the Sentinel-5P/TROPOMI satellite. Top left: 10 February 2020. Top right: 11 February 2020. Bottom left: 13 February 2020. Bottom right: 14 February 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 196. Images of the SO2 emissions during the April 2020 eruptive event at Piton de la Fournaise detected by the Sentinel-5P/TROPOMI satellite. Left: 4 April 2020. Middle: 5 April 2020. Right: 6 April 2020. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

On 10 February 2020 a seismic swarm was detected at 1027, followed by rapid deformation. At 1050, volcanic tremors were recorded, signaling the start of the eruption. Several fissures opened on the E flank of the Dolomieu Crater between the crater rim and at 2,000 m elevation, as observed by an overflight during 1300 and 1330. These fissures were at least 1 km long and produced lava fountains that rose up to 10 m high. Lava flows were also observed traveling E and S to 1,700 m elevation by 1315 (figures 197 and 198). The farthest flow traveled E to an elevation of 1,400 m. Satellite data from HOTVOLC platform (OPGC - University of Auvergne) was used to estimate the peak lava flow rate on 11 February at 10 m3/s. By 13 February only one lava flow that was traveling E below the Marco Crater remained active. OVPF also reported the formation of a cone, measuring 30 m tall, surrounded by three additional vents that produced lava fountains up to 15 m high. On 15 February the volcanic tremors began to decrease at 1400; by 16 February at 1412 the tremors stopped, indicating the end of the eruptive event.

Figure (see Caption) Figure 197. Photo of a lava flow and degassing at Piton de la Fournaise on 10 February 2020. Courtesy of OVPF-IPGP.
Figure (see Caption) Figure 198. Photos of the lava flows at Piton de la Fournaise taken during the February 2020 eruption by Richard Bouchet courtesy of AFP News Service.

Volcanism during the month of March 2020 consisted of low seismicity, including 21 shallow volcanic tremors and near the end of the month, edifice inflation was detected. A second eruptive event began on 2 April 2020, starting with an increase in seismicity during 0815-0851. Much of this seismicity was located on the SE part of the Dolomieu Crater. A fissure opened on the E flank, consistent with the fissures that were active during the February 2020 event. Seismicity continued to increase in intensity through 6 April located dominantly in the SE part of the Dolomieu Crater. An overflight on 5 April at 1030 showed lava fountains rising more than 50 m high accompanied by gas-and-steam plumes rising to 3-3.5 km altitude (figures 199 and 200). A lava flow advanced to an elevation of 360 m, roughly 2 km from the RN2 national road (figure 199). A significant amount of Pele’s hair and clusters of fine volcanic products were produced during the more intense phase of the eruption (5-6 April) and deposited at distances more than 10 km from the eruptive site (figure 201). It was also during this period that the SO2 emissions peaked (figure 196). The eruption stopped at 1330 after a sharp decrease in volcanic tremors.

Figure (see Caption) Figure 199. Photos of a lava flow (left) and lava fountains (right) at Piton de la Fournaise during the April 2020 eruption. Left: photo taken on 2 April 2020 at 1500. Right: photo taken on 5 April 2020 at 1030. Courtesy of OVPF-IPGP (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, April 2020).
Figure (see Caption) Figure 200. Photo of the lava fountains erupting from Piton de la Fournaise on 4 April 2020. Photo taken by Richard Bouchet courtesy of Geo Magazine via Jeannie Curtis.
Figure (see Caption) Figure 201. Photos of Pele’s hair deposited due to the April 2020 eruption at Piton de la Fournaise. Samples collected near the Gîte du volcan on 7 April 2020 (left) and a cluster of Pele’s hair found near the Foc-Foc car park on 9 April 2020 (right). Courtesy of OVPF-IPGP (Monthly bulletin of the Piton de la Fournaise Volcanological Observatory, April 2020).

Geologic Background. The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); 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); GEO Magazine (AFP story at URL: https://www.geo.fr/environnement/la-reunion-fin-deruption-au-piton-de-la-fournaise-200397); AFP (URL: https://twitter.com/AFP/status/1227140765106622464, Twitter: @AFP, https://twitter.com/AFP); Jeannie Curtis (Twitter: @VolcanoJeannie, https://twitter.com/VolcanoJeannie).


Sabancaya (Peru) — June 2020 Citation iconCite this Report

Sabancaya

Peru

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

All times are local (unless otherwise noted)


Daily explosions with ash emissions, large SO2 flux, ongoing thermal anomalies, December 2019-May 2020

Although tephrochronology has dated activity at Sabancaya back several thousand years, renewed activity that began in 1986 was the first recorded in over 200 years. Intermittent activity since then has produced significant ashfall deposits, seismic unrest, and fumarolic emissions. A new period of explosive activity that began in November 2016 has been characterized by pulses of ash emissions with some plumes exceeding 10 km altitude, thermal anomalies, and significant SO2 plumes. Ash emissions and high levels of SO2 continued each week during December 2019-May 2020. The Observatorio Vulcanologico INGEMMET (OVI) reports weekly on numbers of daily explosions, ash plume heights and directions of drift, seismicity, and other activity. The Buenos Aires Volcanic Ash Advisory Center (VAAC) issued three or four daily reports of ongoing ash emissions at Sabancaya throughout the period.

The dome inside the summit crater continued to grow throughout this period, along with nearly constant ash, gas, and steam emissions; the average number of daily explosions ranged from 4 to 29. Ash and gas plume heights rose 1,800-3,800 m above the summit crater, and multiple communities around the volcano reported ashfall every month (table 6). Sulfur dioxide emissions were notably high and recorded daily with the TROPOMI satellite instrument (figure 75). Thermal activity declined during December 2019 from levels earlier in the year but remained steady and increased in both frequency and intensity during April and May 2020 (figure 76). Infrared satellite images indicated that the primary heat source throughout the period was from the dome inside the summit crater (figure 77).

Table 6. Persistent activity at Sabancaya during December 2019-May 2020 included multiple daily explosions with ash plumes that rose several kilometers above the summit and drifted in many directions; this resulted in ashfall in communities within 30 km of the volcano. Satellite instruments recorded SO2 emissions daily. Data courtesy of OVI-INGEMMET.

Month Avg. Daily Explosions by week Max plume Heights (m above crater) Plume drift (km) and direction Communities reporting ashfall Min Days with SO2 over 2 DU
Dec 2019 16, 13, 5, 5 2,600-3,800 20-30 NW Pinchollo, Madrigal, Lari, Maca, Achoma, Coporaque, Yanque, Chivay, Huambo, Cabanaconde 27
Jan 2020 10, 8, 11, 14, 4 1,800-3,400 30 km W, NW, SE, S Chivay, Yanque, Achoma 29
Feb 2020 8, 11, 20, 19 2,000-2,200 30 km SE, E, NE, W Huambo 29
Mar 2020 14, 22, 29, 18 2,000-3,000 30 km NE, W, NW, SW Madrigal, Lari, Pinchollo 30
Apr 2020 12, 12, 16, 13, 8 2,000-3,000 30 km SE, NW, E, S Pinchollo, Madrigal, Lari, Maca, Ichupampa, Yanque, Chivay, Coporaque, Achoma 27
May 2020 15, 14, 6, 16 1,800-2,400 30 km SW, SE, E, NE, W Chivay, Achoma, Maca, Lari, Madrigal, Pinchollo 27
Figure (see Caption) Figure 75. Sulfur dioxide anomalies were captured daily from Sabancaya during December 2019-May 2020 by the TROPOMI instrument on the Sentinel-5P satellite. Some of the largest SO2 plumes are shown here with dates listed in the information at the top of each image. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 76. Thermal activity at Sabancaya declined during December 2019 from levels earlier in the year but remained steady and increased slightly in frequency and intensity during April and May 2020, according to the MIROVA graph of Log Radiative Power from 23 June 2019 through May 2020. Courtesy of MIROVA.
Figure (see Caption) Figure 77. Sentinel-2 satellite imagery of Sabancaya confirmed the frequent ash emissions and ongoing thermal activity from the dome inside the summit crater during December 2019-May 2020. Top row (left to right): On 6 December 2019 a large plume of steam and ash drifted N from the summit. On 16 December 2019 a thermal anomaly encircled the dome inside the summit caldera while gas and possible ash drifted NW. On 14 April 2020 a very similar pattern persisted inside the crater. Bottom row (left to right): On 19 April an ash plume was clearly visible above dense cloud cover. On 24 May the infrared glow around the dome remained strong; a diffuse plume drifted W. A large plume of ash and steam drifted SE from the summit on 29 May. Infrared images use Atmospheric penetration rendering (bands 12, 11, 8a), other images use Natural Color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

The average number of daily explosions during December 2019 decreased from a high of 16 the first week of the month to a low of five during the last week. Six pyroclastic flows occurred on 10 December (figure 78). Tremors were associated with gas-and-ash emissions for most of the month. Ashfall was reported in Pinchollo, Madrigal, Lari, Maca, Achoma, Coporaque, Yanque, and Chivay during the first week of the month, and in Huambo and Cabanaconde during the second week (figure 79). Inflation of the volcano was measured throughout the month. SO2 flux was measured by OVI as ranging from 2,500 to 4,300 tons per day.

Figure (see Caption) Figure 78. Multiple daily explosions at Sabancaya produced ash plumes that rose several kilometers above the summit. Left image is from 5 December and right image is from 11 December 2019. Note pyroclastic flows to the right of the crater on 11 December. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-49-2019/INGEMMET Semana del 2 al 8 de diciembre de 2019 and RSSAB-50-2019/INGEMMET Semana del 9 al 15 de diciembre de 2019).
Figure (see Caption) Figure 79. Communities to the N and W of Sabancaya recorded ashfall from the volcano the first week of December and also every month during December 2019-May 2020. The red zone is the area where access is prohibited (about a 12-km radius from the crater). Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-22-2020/INGEMMET Semana del 25 al 31 de mayo del 2020).

During January and February 2020 the number of daily explosions averaged 4-20. Ash plumes rose as high as 3.4 km above the summit (figure 80) and drifted up to 30 km in multiple directions. Ashfall was reported in Chivay, Yanque, and Achoma on 8 January, and in Huambo on 25 February. Sulfur dioxide flux ranged from a low of 1,200 t/d on 29 February to a high of 8,200 t/d on 28 January. Inflation of the edifice was measured during January; deformation changed to deflation in early February but then returned to inflation by the end of the month.

Figure (see Caption) Figure 80. Ash plumes rose from Sabancaya every day during January and February 2020. Left: 11 January. Right: 28 February. Courtesy of OVI (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-02-2020/INGEMMET Semana del 06 al 12 de enero del 2020 and RSSAB-09-2020/INGEMMET Semana del 24 de febrero al 01 de marzo del 2020).

Explosions continued during March and April 2020, averaging 8-29 per day. Explosions appeared to come from multiple vents on 11 March (figure 81). Ash plumes rose 3 km above the summit during the first week of March and again the first week of April; they were lower during the other weeks. Ashfall was reported in Madrigal, Lari, and Pinchollo on 27 March and 5 April. On 17 April ashfall was reported in Maca, Ichupampa, Yanque, Chivay, Coporaque, and Achoma. Sulfur dioxide flux ranged from 1,900 t/d on 5 March to 10,700 t/d on 30 March. Inflation at depth continued throughout March and April with 10 +/- 4 mm recorded between 21 and 26 April. Similar activity continued during May 2020; explosions averaged 6-16 per day (figure 82). Ashfall was reported on 6 May in Chivay, Achoma, Maca, Lari, Madrigal, and Pinchollo; heavy ashfall was reported in Achoma on 12 May. Additional ashfall was reported in Achoma, Maca, Madrigal, and Lari on 23 May.

Figure (see Caption) Figure 81. Explosions at Sabancaya on 11 March 2020 appeared to originate simultaneously from two different vents (left). The plume on 12 April was measured at about 2,500 m above the summit. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya, RSSAB-11-2020/INGEMMET Semana del 9 al 15 de marzo del 2020 and RSSAB-15-2020/INGEMMET Semana del 6 al 12 de abril del 2020).
Figure (see Caption) Figure 82. Explosions dense with ash continued during May 2020 at Sabancaya. On 11 and 29 May 2020 ash plumes rose from the summit and drifted as far as 30 km before dissipating. Courtesy of OVI-INGEMMET (Reporte Semanal de Monitorio de la Actividad de la Volcan Sabancaya , RSSAB-20-2020/INGEMMET Semana del 11 al 17 de mayo del 2020 and RSSAB-22-2020/INGEMMET Semana del 25 al 31 de mayo del 2020).

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: 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); 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); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).

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Bulletin of the Global Volcanism Network - Volume 25, Number 12 (December 2000)

Managing Editor: Richard Wunderman

Dawson Strait Group (Papua New Guinea)

Occasional seismic swarms 1989-99; no eruptive activity

Etna (Italy)

Summary of July to November 2000 notes small lava flows, Strombolian eruptions

Fournaise, Piton de la (France)

12 October-13 November eruption near July eruption site

Inielika (Indonesia)

Explosions eject tephra in first eruption since 1905

Karangetang (Indonesia)

Explosions generate ash plumes, ashfall, lava flows and avalanches

Kelut (Indonesia)

Inflation and increase in crater lake's temperature and surface height

Lengai, Ol Doinyo (Tanzania)

Continued intermittent eruptive activity; scientist burned by lava

Merapi (Indonesia)

Dome failure and growth during January 2001; over 30 pyroclastic flows

Momotombo (Nicaragua)

Previously unreported low activity during March and April 2000

Popocatepetl (Mexico)

December set records in tremor, dome extrusion rates, SO2 flux, and tilt



Dawson Strait Group (Papua New Guinea) — December 2000 Citation iconCite this Report

Dawson Strait Group

Papua New Guinea

9.62°S, 150.88°E; summit elev. 500 m

All times are local (unless otherwise noted)


Occasional seismic swarms 1989-99; no eruptive activity

During August-October 2000 there were no reports of unusual volcanic activity occurring at Esa'ala (also called the Dawson Strait group). RVO had a 1960s-vintage seismic recorder at Esa'ala until 1994. Since then, maintenance and funding problems have meant it has neither functioned nor been replaced. Discussion with Professor Abe following a seismic survey in the area in the second part of 1999 revealed that he had seen continued seismicity at the Esa'ala base station.

The last notable seismic swarm at Esa'ala before the RVO instrument broke down was in November-December 1992. Another prior swarm of earthquakes took place in mid-December 1989 (BGVN 15:01). RVO maintains a part-time observer at Esa'ala who keeps track of felt earthquakes. He typically reports that no felt earthquakes have occurred.

General References. Davies, H.L., 1973, Fergusson Island, Papua New Guinea-1:250,000 Geological Series: Bur. Miner. Resour. Aust. explan. Notes, SC/56-5.

Smith, I.E.M., 1976, Peralkaline rhyolites from the D'Entrecasteaux Islands, Papua New Guinea, in Johnson, R.W., ed., Volcanism in Australasia: Elsevier, Amsterdam, p. 275-285.

Smith, I.E.M., 1981, Young volcanoes in eastern Papua in Johnson, R.W., ed., Cooke-Ravian Volume of Volcanological Papers: Geological Survey of Papua New Guinea Memoir 10, p. 257-265.

Geologic Background. The Dawson Straits, located between eastern Fergusson and western Normanby Islands in the D'Entrecasteaux island group, contains a volcanic field with several centers that define a possible partly submerged caldera. There have been no historical eruptions, but morphology suggests an extremely young age for some lava flows, and the area displays vigorous thermal activity. The most prominent volcanic centers are Mounts Lamonai and Oiau, located about 10 km apart on the SW tip of Fergusson Island. The summit of Lamonai is capped by a steep-walled crater, and rhyolitic lava flows are exposed on the NE side of the cone. The dominantly volcaniclastic Oiau cone has also produced obsidian lava flows. Dobu Island to the south is formed of coalescing volcanic centers and likewise has produced youthful rhyolitic obsidian flows.

Information Contacts: Ima Itikarai, Rabaul Volcano Observatory (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Etna (Italy) — December 2000 Citation iconCite this Report

Etna

Italy

37.748°N, 14.999°E; summit elev. 3320 m

All times are local (unless otherwise noted)


Summary of July to November 2000 notes small lava flows, Strombolian eruptions

This summary of Sistema Poseidon reports covers the period from July to November 2000. The summit craters discharged several minor lava flows, some Strombolian eruptions, and frequent degassing. The Bocca Nuova (BN) vent was particularly active.

During July and well into August the summit craters displayed comparatively low activity. During July at BN three different vents were degassing. During July at NEC emissions came from one primary vent. Emissions were robust on 18 August, and commonly bore light-brown ash.

During late August, Southeast Crater (SEC) renewed emission of a weak lava flow from a fracture on the N side. The lava stream, which flowed into the Valle de Bove, persisted throughout 27 August, and increased progressively on the night of 27-28 August.

At 0135 on 28 August fairly sustained degassing occurred at SEC with initially violent Strombolian emissions. Beginning at about 0600, the explosive Strombolian activity changed rapidly to violent lava fountains, which generated an eruptive cloud rising thousands of meters above the summit. Ash and lapilli fell on the Etna's E slopes. This phase lasted about one hour, and was analogous to what had been observed during episodes in the first half of 2000.

The lava flow, despite appearing larger during the more violent degassing phase, moved little on its farthest-advanced fronts, which along the W face of the Valle del Bove reached to about 2,200-2,300 m elevation. Rather, the flow tended to widen in the zone between 2,800 and 2,700 m. The lava emission rate at the vent appeared to be drastically reduced at the end of this degassing phase.

A new degassing episode was confirmed on 29 August. This was characterized by its brevity and by the way in which it manifested itself, producing explosive Strombolian blasts (rhythmic expulsion of pyroclastics) rather than true lava fountains.

As frequently observed for the last episode, this one also started with a glimmer of light on the N flank of the SEC announcing the beginning of a new lava emission. Eruptive activity increased between 22 and 28 August, while the volcanic tremor first showed a modest increase at 0339 on 29 August, when sporadic explosions from the SEC summit crater began. Only after 0530 did the explosive activity reach a continuous intensity. It concluded at about 0610. Peak activity did not reach the same levels as the preceding phase, but ejected pyroclastics ~200 m above the crater rim. The finer portions were carried several hundred meters and dispersed E, without reaching residential areas.

Observations at the conclusion of the late-August explosive phase showed the new lava flow still spreading over the N flank of the SEC, but new lava had ceased venting. This new flow overrode the one from 28 August, and descended to ~2,100 m on the W face of the Valle del Bove.

The other craters in the volcano's summit area chiefly slowly emitted gas vapors, with the exception of one of BN's vents, which frequently ejected brown ash. The emission of ash from this vent intensified during the week. As September began, BN continued to produce abundant steam and ash emissions, which at times seemed aided by elevated atmospheric humidity and by infiltration of recent precipitation. This effect continued later into September.

In mid-September, BN produced generally mild degassing. During 19, 22, and 23 September nearly continuous ash emission took place. Primarily dark gray and sometimes brownish colored plumes were visible for many kilometers. For the preceding weeks these plumes had vented at two distinct crater cavities on the inside of the BN. The larger cavity lies in BN's center and discharged gaseous blue-white emissions. The smaller cavity lay near BN's internal SW wall, and it expelled ash. During this same time, as in past weeks during the month, the Voragine and Northeast Crater continued to emit abundant steam. The SEC weakly degassed from fumaroles.

October activity continued as in past months with ash emissions at the BN. These were particularly visible on 3-6 October. At night it was possible to observe light coming from the crater cavity on the inside of the BN, suggesting weak Strombolian activity. Mid-October behavior included explosive Strombolian eruptions from both crater cavities; incandescent bombs occasionally fell outside of the crater. Milder episodes occurred on 17 and 21 October. Between 24 and 29 October two stronger episodes took place.

At the Voragine and the NEC, the early days of October showed rather sustained steam emissions, in part accentuated by the first snowfalls and by the elevated humidity on the summit. The SEC displayed mostly fumarolic activity. Later, the Voragine gave off copious steam, but at the SEC and NEC weak degassing occurred.

The last days of October and the early days of November were distinguished by a decline of the explosive Strombolian activity from the two emission points within BN. Strombolian activity sent tephra ~100-150 m high, which still frequently fell outside of the BN crater.

During November, BN continued to produce modest explosive Strombolian activity that sometime spewed incandescent material of moderate size outside the crater walls. Observers continued to note two distinct cavities in BN.

In the early hours of 29 November observers noted the presence of a small lava flow at the base of the SEC. Upon close viewing, observers found that the flow gushed from the base of a fracture on the N sector of the cone at the SEC and continued downslope for ~200 m. Although lava continued to flow in the succeeding days, atmospheric conditions obscured later views of this area. No relevant activity aside from a constant steam emission occurred either at the Voragine or at the NEC during this time.

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

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


Piton de la Fournaise (France) — December 2000 Citation iconCite this Report

Piton de la Fournaise

France

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

All times are local (unless otherwise noted)


12 October-13 November eruption near July eruption site

Piton de la Fournaise erupted several times during 2000; 14 February to 4 March (BGVN 25:01), 23 June to 30 July (BGVN 25:07), and in October. The last eruption in 2000 began on 12 October after two periods of inflation, high pre-eruptive radon emissions, and three weeks of increased seismicity beneath the volcano.

During the two months prior to the eruption, two tiltmeter stations, "Dolomieu Sud," located at the volcano's summit and "Château Fort" on its southern base, showed tilt variations of up to 50 µrad, which indicated a clear inflation of the S flank. In addition, extensometer data at Château Fort showed that fissure openings had significantly increased since the preceding eruption in June 2000. The fissure expansions confirmed that inflation was occurring.

Three weeks prior to the eruption high seismicity occurred under the volcano, with 10 to 20 earthquakes per day. A small seismic crises that consisted of 57 earthquakes occurred on 6 October (figure 56). Thereafter, the number of seismic events returned to the high levels that had been recorded during the previous 3 weeks until the number of earthquakes significantly increased on 12 October, marking the beginning of the eruption. All of the 278 seismic events that occurred between the end of September and 12 October were of very low energy, usually with magnitudes less than 0.7. Only seven earthquakes were recorded with higher magnitudes, ranging between 0.9 and 1.7.

Figure (see Caption) Figure 56. The number of daily seismic events recorded at seismic stations at Piton de la Fournaise during 10 September through 21 October 2000. Courtesy of OVPDLF.

In addition to increased seismicity, high radon activity was measured at the volcano. Three different probes in soil and old eruption vents at the "Bory" station on the W rim of the summit crater showed a high mean level of radon activity. The "Bory 3" radon probe showed about 40 counts per day, which was 2.7 times higher than during January-May 2000. OVPDLF scientists determined that the high counting rates indicated a general increase in volcanic gas emissions from the volcano, reflecting the presence of degassing magma.

At 0401 on 12 October a seismic crisis began that consisted of 201 low-energy events (figure 56). All but five events had magnitudes less than or equal to 1.1, with the largest being 1.6. The seismic crisis lasted 64 minutes and at 0505 a strong eruption tremor, which was localized on the E flank of the volcano, appeared at the summit stations. Visual observations helped to constrain the eruption site between "Signal de l'Enclos" and "Le Langlois" craters, and above "Piton Pârvédi" crater, which formed during the previous eruption in June 2000 (figure 57). Field observations conducted with a hand-held GPS receiver allowed scientists to precisely locate the two fissures where lava was emitted during the eruption. The smaller fissure (fissure 1) was several tens of meters long, located at 2,260 m in altitude, and emitted a small, 50-100 m long aa lava flow. The other fissure (fissure 2) was 680 m long and ran continuously between 2,220 m and 2,000 m in altitude.

Figure (see Caption) Figure 57. Sketch map showing the location of craters of the 12 October activity and fissures where lava flows were emitted. PDN (Piton de Neiges) is a coordinate system used on Reunion Island by IGN and other scientists. In general, IGN maps include both PDN and international ellipsoid coordinates. Courtesy of OVPDLF.

Almost all of the lava-flow activity occurred at fissure 2. At 1100 on 12 October, lava fountaining still occurred within the lower 350 m of fissure 2, and lava output was relatively high. A large network of numerous aa lava flows of up to 200 m width traveled down the SE flank of the volcano towards "Piton Pârvédi" and continued in a single, large lava flow for 5.5 km on the southern border of the June lava flow until reaching 400 m in altitude. At 2100 on 13 October, about 40 hours after the eruption began, the rate of lava emission was still high with an estimated rate of 40-60 m3/s. A continuous incandescent lava flow, at least 2 km long, was visible.

The following day volcanic activity was focused on the lower end of fissure 2, and a crater began to build up. It was named "Piton Morgabim." Initially the crater was U-shaped with an opening towards the ESE. Throughout the entire period of activity a permanent lava lake was present within the crater, and lava flows were observed on the downhill (SE) side of the crater. During the first week of November the crater closed so that the lava lake was no longer visible, and the upper crater walls were high and sub-vertical. Several tunnels began to form and a tumulus that was several tens of meters high piled up in front of "Piton Morgabim" (figure 58). Since the end of October pahoehoe lava flows appeared in the upper part of the initial aa lava flows and surrounded "Piton Pârvédi" crater to the N and S.

Figure (see Caption) Figure 58. Photograph of the eruption, taken from the SW at 0943 on 9 November from a helicopter. The photograph shows the initial crater ("Piton Morgabim") and the new vent (circled to the left) and an active incandescent lava flow channel. The pahoehoe lava flows above "Piton Pârvédi" that began in late October can be distinguished (gray area), as well as the tumulus in front of "Piton Morgabim." Courtesy of OVPDLF.

Since 29 October, tremor began to increase until it reached the same high value as during the first minutes of the eruption. Tremor remained at high levels for the following 5 days. Beginning on 5 November strong degassing and liberation of H2S occurred just above "Piton Morgabim." On 8 November the upper crater walls collapsed and the [lava] lake, which was ~40 m in diameter, was visible again. On 9 November an intense explosion occurred ~50 m NW of "Piton Morgabim" crater, and rocks and lava were ejected up to 200 m in altitude. A second vent formed in this area and both it and "Piton Morgabim" were simultaneously active for several tens of hours (figure 58 and 59). From 12 November, explosions and black ash were observed at the upper vent, which were most likely phreatomagmatic features. Lava bombs were ejected up to 250 m away from the vent. Both vents fused together, and the initial crater raised up, finally forming one single large crater named "Piton Morgabim" (figure 59). Figures 16 and 17 show different stages of the vents growing together. During the period of increased tremor, new several-km-long pahoehoe flows formed. Again they surrounded Piton Pârvédi to the N and S and covered large parts of the June 2000 lava flow. In particular, one pahoehoe lava flow extended beyond the front of the June eruption in the "Grand Brûlé" by ~500 m length down to 370 m elevation.

Figure (see Caption) Figure 59. Photograph of "Piton Morgabim" and a second crater coalescing at Piton de la Fournaise. The photograph was taken on 11 November from the E flank of the volcano. The saddle-shaped separation between the two craters disappeared during the next days. Bright spots to the left and right of the craters were emanations from the lava flow and fissure 2, respectively. Courtesy of P. Morin.

The high level of tremor suddenly disappeared at 2310 on 13 November, marking the end of the eruption. By this time the remaining crater, "Piton Morgabim," was ~100 x 75 m across and 30-40 m deep (figure 60). On 15 November, the lava flow SE of the crater was still hot; a temperature of ~800°C was measured 40 cm below the surface.

Figure (see Caption) Figure 60. Photograph of the surface of the affected area of Piton de la Fournaise after the eruption. The black line shows the outline of the lava flow. Courtesy of OVPDLF.

Basalt samples were collected throughout the eruption. The initial basalt was apheric, near the end of October olivine crystals appeared, and near the end of the eruption the basalt had numerous centimeter-sized olivine crystals.

Digital photos were analyzed in order to map the lava flow and to obtain an estimate of it's erupted volume. The total erupted volume was estimated to be on the order of 5 x 106 m3, which is a typical value for eruptions at Piton de la Fournaise.

Correction. In BGVN 25:07 the area of the entire lava flow from the 23 June-30 July 2000 eruption of Piton de la Fournaise was reported as being 3 x 102 m2, when it was actually 3 x 106 m2.

Geologic Background. The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Information Contacts: Thomas Staudacher, Jean Louis Cheminée, Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, Institut National des Sciences de l'Univers, 14 RN3 - Km 27, 97418 La Plaine des Cafres, Réunion, France (URL: http://www.ipgp.fr/fr/ovpf/observatoire-volcanologique-piton-de-fournaise).


Inielika (Indonesia) — December 2000 Citation iconCite this Report

Inielika

Indonesia

8.73°S, 120.98°E; summit elev. 1559 m

All times are local (unless otherwise noted)


Explosions eject tephra in first eruption since 1905

A minor explosion occurred at 1915 on 11 January 2001. The explosion ejected ash that coated Bajawa (~8 km from the summit) with an ash layer less than 0.5 mm thick. Increased activity after 11 January prompted the VSI to set the volcano's hazard status to 3 (on a scale of 1-4). Three explosions occurred at about 0700 on 13 January, sending ash 300-1,000 m above the crater rim. Workers at the volcano's observatory post, located ~7.5 km from the summit, subsequently heard thundering sounds. Ash, which appeared dense and light in color, blew E to Toa and S to Boya, Bolodio, and Bajawa. By 15 January, a seismograph recorded continuous tremor with an amplitude of 2 mm in addition to 59 explosion earthquakes with amplitudes of 2-14 mm.

Ash emission was ongoing as of 16 January, and ranged from 100 to 1,000 m above the summit. VSI workers observed two new large craters trending SE-NW. The top of the SE crater measured 50 m in diameter, narrowed to 25 m at its base, and was 10 m deep. It emitted an audible sound and ejected an ash plume from its N wall with variable pressure. Winds tended to blow ash toward the S. The NW crater was 20 m in diameter and 1.1 m deep. The temperature of a fumarole measured 95°C, and nearby ground temperature measured 89°C.

During 16-22 January, explosions produced both ash and lapilli. Light gray ash fell around the main crater within a 10-20 m radius. Lapilli, which had a maximum size of 50 cm, fell up to 500 m from the main crater.

Geologic Background. Inielika is a broad, low volcano in central Flores Island that was constructed within the Lobobutu caldera. The complex summit contains ten craters, some of which are lake filled, in a 5 km2 area north of the city of Bajawa. The largest of these, Wolo Runu and Wolo Lega North, are 750 m wide. A phreatic explosion in 1905 formed a new crater, and was the volcano's only eruption during the 20th century. Another eruption took place about a century later, in 2001. A chain of Pleistocene cinder cones, the Bajawa cinder cone complex, extends southward to Inierie.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).


Karangetang (Indonesia) — December 2000 Citation iconCite this Report

Karangetang

Indonesia

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

All times are local (unless otherwise noted)


Explosions generate ash plumes, ashfall, lava flows and avalanches

Heightened activity continued at Karangetang in late December 2000-late January 2001, following a year of frequent activity in 2000 (BGVN 25:11). The main crater and Crater II sent a white, variably-thick ash plume up to 600 m above the summit during 19-25 December. Plume illumination up to 150 m above the craters was visible at night. Lava flows occurred on 21-22 December and reached as far as 1,250 m laterally along the SW flank. The seismic record also showed increased activity with multi-phase earthquakes predominating.

Activity, however, tailed off during 26 December-1 January before increasing again with renewed vigor from 2 to 8 January. At 1258 on 2 January an explosion produced a white-gray ash plume that rose ~500 m above the summit. At 1845 on the same day, workers observed a glowing lava avalanche issuing from the main crater and moving 50 m from the summit down toward the Naitu River. A larger explosion on 7 January sent gray ash 1,500 m above Karangetang. A coeval Strombolian eruption cloud rose 200 m. Ashfall occurred W of the volcano, coating Pahe, Lehi, Mini, and Kinali villages. Lava flowed down to the Tanitu River as far a 1 km from the summit. Tectonic earthquakes dominated seismicity during the week, and a significant number of tremor earthquakes also occurred.

A minor explosion occurred on 10 January; ash rose and subsequently fell back into the crater. Tectonic earthquakes again overshadowed all other types during 9-15 January. At 0845 on 17 January an explosion generated a small ash plume and a lava avalanche. Ash fell on Salili and Beong villages; lava flowed down both the E and W flanks of the volcano. Seismicity remained elevated with earthquake distributions similar to the previous week. The VSI maintained a hazard status of 2 (on a scale of 1-4) for Karangetang throughout the report period.

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: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).


Kelut (Indonesia) — December 2000 Citation iconCite this Report

Kelut

Indonesia

7.93°S, 112.308°E; summit elev. 1731 m

All times are local (unless otherwise noted)


Inflation and increase in crater lake's temperature and surface height

Increasing crater lake temperature, water level, and inflation have been observed since 19 January 2001. Water temperature in the crater lake rose to 47.5-49.1°C. On 21 January water level rose 5 cm. Leveling measurement showed 5.5-6 mm of inflation. During 16-22 January, seismographs recorded 20 tectonic earthquake events. These observations prompted the VSI to increase Kelut's hazard status from 1 to 2 (on a scale of 1-4).

Geologic Background. The relatively inconspicuous Kelut stratovolcano contains a summit crater lake that has been the source of some of Indonesia's most deadly eruptions. A cluster of summit lava domes cut by numerous craters has given the summit a very irregular profile. Satellitic cones and lava domes are also located low on the E, W, and SSW flanks. Eruptive activity has in general migrated in a clockwise direction around the summit vent complex. More than 30 eruptions have been recorded from Gunung Kelut since 1000 CE. The ejection of water from the crater lake during the typically short but violent eruptions has created pyroclastic flows and lahars that have caused widespread fatalities and destruction. After more than 5000 people were killed during an eruption in 1919, an ambitious engineering project sought to drain the crater lake. This initial effort lowered the lake by more than 50 m, but the 1951 eruption deepened the crater by 70 m, leaving 50 million cubic meters of water after repair of the damaged drainage tunnels. After more than 200 deaths in the 1966 eruption, a new deeper tunnel was constructed, and the lake's volume before the 1990 eruption was only about 1 million cubic meters.

Information Contacts: Dali Ahmad, Volcanological Survey of Indonesia (VSI), Jalan Diponegoro No. 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/).


Ol Doinyo Lengai (Tanzania) — December 2000 Citation iconCite this Report

Ol Doinyo Lengai

Tanzania

2.764°S, 35.914°E; summit elev. 2962 m

All times are local (unless otherwise noted)


Continued intermittent eruptive activity; scientist burned by lava

Activity has continued intermittently since early August 1999 (BGVN 24:11). Celia Nyamweru compiled a report based on observations and interpretations of photographs taken of the crater on various dates between 2 September 1999 and 29 July 2000, and observations made during a 23-26 July 2000 visit to the summit crater. Observations and photos during this period are from the mountain guide Burra Ami Gadiye unless otherwise noted. The report for July 2000 also includes the observations of Fred Belton. A report of fieldwork performed in early October 2000 was prepared by Christoph Weber.

Some cones have been renumbered according to the system agreed on by Nyamweru, Belton, and Weber in October 2000. Under the revised system a new eruption center is assigned a new T-number (e.g. T49). New cones at the flank of an existing cone, and clearly fed by this, will be identified with letters appended to the T-number (e.g T49B, T49C, etc.). This leads to the following renumbering: T52 (formerly T52C), T52B (formerly T52W), T52C (formerly T52E), T37 (formerly T37S), T37B (formerly T37N1), T37C (formerly T37N2), and T37D (formerly T37E and also formerly T5/9). This report reflects the new cone names.

Activity during September-December 1999. Reports and photographs from Gadiye on 2 and 10 September 1999 showed no eruptive activity, almost no dark lava visible, and steaming from cone T47. Colors of the crater floor ranged from white to light gray and light brown, with a slightly darker (chestnut brown) patch of lava around the lower slopes of T45. Small dark patches on the upper slopes of T40 might have been fresh spatter. There were no new cones or significant changes since July 1999. On 10 October Gadiye reported similar activity, plus steam from T37 and T47. A small flat-topped cone W of T37 and T45 may be new, though it is pale gray.

Gadiye's notes from 9 November refer to a cone (most likely T40) throwing out lava. The eruption appeared to be small, with lava bubbling at the top of a hornito on the lower slope of the cone. Some small flows appeared to have come from the central part of the slopes of one or two of the large cones, so possibly there had been some minor activity since 10 October 1999. Joerg Keller reported about a 23 December visit to the crater by Michael Kraml, Ralf Gertisser, Marika Vespa, and Andrea Bull. Patches of relatively fresh looking lava were seen around cones T48 and T49. Between cones T48 and T49 there was a 30-cm-thick layer of natrocarbonatite tear-drop lapilli, relatively fresh in appearance and about a week old. No new cone was present on the W side of the crater floor.

Activity during January-20 July 2000. Gadiye's notes from 2 January refer to "a completely new cone that appeared in December 1999" shown in several photos. In one, he describes it as "throwing out lava violently" although this is not entirely clear from the photograph. This cone, towards the W side of the crater, has been named T51. Most of the crater floor was white to light gray and light brown, with pahoehoe lobes and other well-defined structures. Located close to the W wall, T51 had regular, rather steep slopes and was surrounded with fresh lava. These flows are pahoehoe but appear rather thick in comparison to their length, possibly 10-20 cm thick rather than the 2-5 cm layers observed elsewhere. Emission of steam occurred from several cones in the central cluster.

On 6 January Gadiye noted that very dark fresh-looking lava seemed to originate from a small vent between the E (T37-T45) and W (T47-T49) cone clusters. This may be the beginning of the activity that produced the T52 group described in July 2000. Overall the colors of the crater floor ranged from white to light gray and light brown. The lower slopes of T45 look significantly darker than the pale gray lava surrounding them.

Gadiye's photographs from 24 January showed continued activity from the area between the E and W cone clusters. The source of four long narrow tongues of lava seemed to be a low flat-topped cone between T48 and T37B. Other photographs show a large patch of dark lava between the older cone clusters and possibly a small flow from it towards the NE. Colors of the crater floor ranged from white to light gray, except for the dark patches around T52 and the new flows. The lava at the E overflow was white and showed little or no change since 1999.

Aerial photographs taken on 8 February by Benoit Wangermez showed no visible eruptive activity. No significant changes seemed to have occurred since late January 2000. Gadiye noted no eruptive activity on 12 March. T40 showed little change, there was a small pale brown hornito between T40 and the NW overflow, and T51 was rather pale brown with no sign of dark lava flows around it. Photographs by David Bressler in late April/early May revealed a cone with fresh lava on its slopes, probably T49B. No eruptive activity could be seen on an aerial photograph taken by Nigel Pavitt on 2 May (figure 65). Gadiye also did not report any activity on 7 May. No fresh lava flows were visible in his photographs; the flows originating from the T52 vent(s) were mid-brown in color.

Figure (see Caption) Figure 65. An aerial photograph of Ol Doinyo Lengai taken on 2 May 2000 from the W showing the upper part of the cone with Ketumbeine mountain in the background. The summit crater is white, with no details of individual cones visible. The outer walls on the NW and W side are clearly visible, along with the NW overflow, the breakout lava flow of June 1993 on the W wall, and the numerous erosional gullies that expose white ash. The similarity of color between the weathered lava and the weathered ash in the gullies makes it very difficult to determine how far down the slopes the lava flows have extended. Photograph by Nigel Pavitt; courtesy of Celia Nyamweru.

No activity was obvious in 20 July aerial photographs from Luigi Cantamessa (Geo-Decouverte SA), though some very fresh lava may have been present around T51. A near-vertical view of the crater floor and outer W and NW slopes showed the NW overflow clearly, with very pale brown seeming to extend several hundred meters down the outer slope. The breakout lava flow of June 1993 was also visible on the W slope, and seemed shorter than the NW overflow. A photo taken from over the summit looking N revealed a variety of colors on the crater floor, evidence of many lava flows. One medium-sized brown flow extended S from T46, ending in a broad front of rounded lobes. A near-vertical view with the NW wall in the foreground showed several flows of pale brown and pale gray lava that had moved across the crater rim. The darkest patches on the crater floor were NNW of T49B and W of T51. The patch near T51 was small with very narrow lava tongues radiating outwards. These appeared to be very recent, as such small very narrow flows would not remain dark for very long once the eruption ended.

Activity during 23-30 July 2000. Observations and photographs were made during summit visits by C. Nyamweru (23-26 July) and F. Belton (23-30 July).

Observations made by Nyamweru of the crater floor on 24 July (figure 66) showed that the N part was mostly pale gray, pale brown, or white in color, with no sign of recent lava flows. The youngest lava flows were in the S and E parts of the crater floor. Flow 1, originating from a small vent on the slopes of T46, was probably several weeks old; it still retained its form, pahoehoe surface texture, and a slightly darker brown color than its surroundings. It had recently been partly covered by Flow 2, which was probably less than 24 hours old when Nyamweru's group arrived at the summit on 23 July. On the morning of 23 July it could just be touched with a bare hand; most of the flow was very dark brown with a small amount of whitening around the edges of the slabs. It retained significant warmth and cracking sounds could frequently be heard from within this flow. Flow 2 was ~1.5 m thick with a rough surface composed of broken, tilted pahoehoe slabs, covering much of the S crater floor. It appeared to have originated from the small T37D vent. The lava flowed S and E, surrounding two remnant slabs of the old crater wall and pouring down in a 'lava fall' between T24 and the crater wall to the lower level of the S crater floor. It flowed into T24 and partly buried it, and also flowed around T26, T27, and T30. 'Lava strandlines' were visible around the crater wall E of T24 where the lava lake had been held at a higher level. Flow 3 moved from the N slope of T37B to the N and E to within a few meters of the E overflow. It was still very hot about 1330 on 23 July. Several large blocks of older lava on the upper part of Flow 3 had probably been part of the top of T37B.

Figure (see Caption) Figure 66. A sketch of crater features at Ol Doinyo Lengai made from the summit on 24 July 2000. Notable features include three recent lava flows, large cracks in the crater floor and walls, and a lapilli field. Courtesy of C. Nyamweru.

The N and W crater floor were crossed by radiating cracks, some of which continued from the floor up through the crater wall. Some of them emitted steam and sulfur fumes, and in places the ground along the cracks was bright yellow with sulfur crystals. Such cracks have long been features of the crater floor, but compared with earlier years there were more of them and they were wider. Nyamweru estimated one crack on the N wall as being ~1 m wide; Belton measured a crack between T40 and T49 and obtained a width of 60 cm and a depth of 4.1 m. Four or five big cracks continued from the floor up onto the N crater wall; this was not something that had been obvious in earlier years. A deep crack extended from T51 across the SW crater floor and up onto the crater wall.

At the NW overflow a photograph taken from the road N of the cone showed what may be a very narrow tongue of white lava (?), not present in July 1999. It appeared to have flowed down a gully in which whitish patches of ash are visible lower down. There is no evidence of major lava flows spilling out of the crater during the last few months, possibly even during the last year. The most recent flows to have crossed the rim may be towards the S end of the overflow, and are small, discolored pahoehoe flows that may have emerged from T51 since January 2000. A crack over 20 cm wide emitting sulfur fumes and steam ran from T49B NW towards the crater rim at the overflow.

In a photograph of the E overflow taken from the road E of the cone no changes were evident since July 1999. However in July 1999 Nyamweru measured the width of this overflow as 22 m, whereas in July 2000 it was 38 m. In July 2000 there was no sign of any fresh lava approaching the overflow apart from Flow 3, which reached within 20 m of the N side of the overflow on 23 July. The low point on the SW rim had changed little since July 1999; small pahoehoe flows from T51 had reached the SW crater wall, but not close to this low point.

T51 was the new cone on the W side of the crater, probably formed in late December 1999. T47/T36/T39 showed little or no change. T46/T44 showed little or no change, but was the source of Flow 1. T48 had collapsed. T49 has been joined by a well-defined cone to its W, called T49B. Three new cones (T52 group) formed E of T48; the western one was a jagged brown cone with no signs of recent activity; the two eastern ones were younger, with smoother shapes and dark gray to black in color, possibly the source of some small lava flows within the last few days. T37B's big open vent had collapsed. The small T37D cone, visible in 1999 photographs, seemed to have been very active in the few days preceding the visit, in particular as the source of Flow 2.

The lapilli field covered an area some tens of meters across, S of T45 and E of T37D. Here the lapilli, well-formed spheres and ovals less than 2 mm in diameter, were black and still warm on 23 July, forming a layer ~8 cm thick. In this area the lapilli overlay some recent lava but in turn were overlain by small pahoehoe flows. Nearby the surface layer of lapilli had already turned white, but below 1-cm depth they were still warm and black. Elsewhere, smaller quantities of lapilli very similar in appearance occurred on the crater floor and on the E crater wall. Lapilli extended ~130 m across the crater floor from the N end of the E overflow, lying in small depressions. In this area the lapilli were pale gray on the afternoon of 23 July. Small amounts of similar gray lapilli were seen on the surface to about a quarter to a third of the way up the SE crater rim.

Belton provided detailed descriptions of the activity at the cones during this period. Activity was nearly continuous at T49B, but varied considerably in nature and intensity. The cone degassed frequently, sometimes emitting loud jets of steam and lava fragments, other times producing a steady output of invisible gases. The degassing alternated with lava splashes that coated the sides of the cone. Eruptions usually occurred 4-5 times per minute. On the night of 23 July cone T49B produced several short aa flows. Rockfall from the top of T49B was also common, with some lava boulders 30 cm in diameter rolling up to 7 m from the base. Throughout the week the summit vent(s) of T49B frequently changed size and location.

The T51 cone built up a low shield in the WNW part of the crater. Lava overflowed from the summit vent of T51 several times during the early morning of 23 July. In a much larger eruption at 1130, lava of very low viscosity cascaded down the N flank and formed pahoehoe flows at its base. A similar but smaller eruption occurred at 1900. From 24 through 27 July cone T51 contained lava at depth (5 m). At 0600 on 28 July a lava pond was 2 m below the rim of the 1-m-diameter summit vent. The pond degassed with increasing vigor and gradually rose closer to the top of the vent. At 1645 lava overflowed the N side, forming channel-fed pahoehoe flows (figure 67). Similar activity continued through the night and into 29 July. Numerous small cones formed above the lava tubes and erupted highly vesicular lava, really nothing more than brown foam. Around 1300 on 29 July surges about once per minute caused the pond to overflow. The eruption continued through 0800 on 30 July (figure 68). One flow traveled 75 m NW to within 16 m of the NW crater rim breach. During the 39 hours of activity, T51 grew in height by at least 1.5 m and its summit vent was reduced in size by ~75%.

Figure (see Caption) Figure 67. Cone T51 in the Ol Doinyo Lengai summit crater overflowed at 1645 on 28 July, sending lava flows down the N and NW slopes. The shape of the small lava shield that T51 has constructed is apparent here. The summit of Ol Doinyo Lengai is just behind the hornito. Courtesy of F. Belton.
Figure (see Caption) Figure 68. Photograph showing the summit area of cone T51 in the crater of Ol Doinyo Lengai on the morning of 29 July. After erupting through the night of 28 July, the lava dropped to a lower level inside T51 by 0800 on the 29th. A climb to the top revealed beautiful lava stalactites around the interior rim of the ~ 1-m-diameter summit vent. Courtesy of F. Belton.

At around 1300 on 23 July a short (about one minute) unusually violent eruption from T37B sprayed ejecta ~25 m above the cone. It is probable that this activity also created Flow 3, a fast moving 15-cm-thick flow of ropy lava that moved to the E. Minor activity also occurred in this part of the crater on 25 July between about 1500 and 1600 when a 10-m-long pahoehoe flow emerged from a small ground-level vent just E of T37D.

Activity during October 2000. An expedition organized by Chris Weber from 3 to 11 October 2000 consisted of a film team and four scientists, led by Joerg Keller. Observations were made by J. Keller, A. Zaytsev, D. Wiedenmann, J. Klaudius, D. Szczepanski, M. Szeglat, and C. Weber. The best-known track is on the WNW flank. Two other different routes were taken during descents following the visit (figure 69). The track down the NE flank (named Dorobo-Route) and a second track starting halfway between the W crater wall and the summit and descending the WSW flank to pass the Kirurum crater (named Reck-Route) were followed by different expedition members. An overnight camp was made at the Kirurum crater to give time for fieldwork. GPS data and barometric measurements gave new information about the elevations of various points on Ol Doinyo Lengai. The summit peak is approximately 2,955 m (2,950-2,960 m) elevation, cone C on the N crater rim is approximately 2,835 m, and the crater floor was approximately 2,925 m at the NW and E overflows.

Figure (see Caption) Figure 69. Sketch map of the Ol Doinyo Lengai area showing nearby geographic features and climbing routes, October 2000. Courtesy of C. Weber.

Flow 1 (figure 70) still had a brown appearance, but continued to weather and was lighter in color than on 30 July. The younger Flow 2 was partly black to gray in the joints and cracks of the aa flow field. Some smaller flows around T49 and T49B were slightly black, though probably only a few hours old. Hydration of fresh lava flows (especially under high humidity) can cause a black surface to turn white within 24 hours. NW of T49B another cone appeared after 30 July and was named T49C. T51 was surrounded by flat pahoehoe flows and had grown since 30 July. There was a new cone in the collapsed T48 with some small light gray lava flows close to the cone. During this year many new cracks (at maximum up to 1 m wide and 5 m deep) had opened all across the crater floor. Most of the V-shaped cracks pointed to the T52 and T49 clusters, roughly the center of the major cone concentration. Some of the cracks broke through the crater rim. Other cracks were filled or covered by young lava flows.

Figure (see Caption) Figure 70. Sketch maps of the Ol Doinyo Lengai crater, October 2000, showing cracks (left) and recent lava flows (right). Courtesy of C. Weber.

Between 1200 and 1350 on 3 October spattering occurred from a small vent in the saddle between T49 and T49B. Two small lava flows were observed at the N and S flank of T49 during that time. At 1350 the W side of T49B collapsed, creating a ~6-m-wide and 5-m-high opening from which a sudden flash flood of lava was released. Parts of the collapsed wall of T49B were washed towards the W as big blocks. Within a few seconds the flow had reached halfway between the cone and the NW overflow. After 5 minutes the flow (Flow 4A) had reached its final extent ~40 m short of the NW overflow (figure 70). The lava flow was up to 5 cm thick and later aa flows were several decimeters thick. Until 8 October lava spattering and small lava flows had nearly closed the gap in the W wall of T49B. On the morning of 9 October at 1035 the W flank again collapsed in the same manner as on 3 October, leaving a 7-m-wide and 7-m-high gap. A flash flood of lava moved NW (Flow 4B) within seconds and stopped just 10 m from the NW overflow, covering Flow 4A. During the afternoon of 9 October T48 had strong degassing and for 10 minutes ejected tear-drop lapilli; no further activity was seen. Right after sunset of 9 October a crack opened at the SSW base of T49C with a noisy gas jet followed by a 10-minute spray of lava droplets and spherical lapilli up to ~10 m high. Small lava flows (Flow 4C) were emitted and moved NW. No more flows were observed through 11 October, but the lava lake inside T49B was splashing and degassing.

Between 3 and 9 October 2000 temperature measurements were made by three different instruments and gave consistent values. A digital thermometer (TM 914C with a K-type stab feeler) was used in the 0-1,200°C mode, taking readings by inserting the feeler 10 cm into still-moving and liquid lavas (10 times on various days) and as deep as possible into the fumaroles (five times on various days). Calibration was by the Delta-T method: values are ± 6°C in the 0-750°C range. All values were recorded by four repeat measurements at one spot. The pahoehoe lava flow (15 m below outflow from the T49B lava pond in an closed lava tube) was at 507°C. An aa flow front in slow motion (shortly after escaping an enclosed lava tube near T49B, 25 cm thick) was 496°C. The fumarole 25 m NNW of T49C in a crater crack towards the rim was at 75°C. The fumarole at the NW overflow inside the old crater rim was at 69°C. The fumarole on the NW flank of T48 was at 95°C.

On the evening of 3 October, one of the scientists (Jurgis Klaudius) accidentally stepped in a fresh but already solid-looking lava flow (~25 cm thick) at the W slope of T49B. This can easily happen in the dark when it is difficult to discern between solid and fresh black flows. In this case it caused a serious second-degree burn around his left ankle up to his lower leg. The lava, at a temperature of about 500°C, burned away all of the light plastic parts of his sport shoe, leaving the leather parts and the sole. On 6 October evacuation was necessary because of the risk of infection. He managed to slide down the steep slopes on his hands and right foot for most of the steep upper track, but was finally carried the rest of the way down in a seat on the shoulders of four porters. He was brought to a hospital in Arusha and then flown to Germany 24 hours later. Klaudius is recovering very well following skin grafts and will not suffer lasting damage.

Lengai is as dangerous as any other active volcano. Activity includes explosive eruptions, suddenly appearing lava fountains, several cone collapses, lava flash floods, and flows of enormous quantity. A lava temperature of 500°C is hot enough to burn someone seriously and because of the very low viscosity, this natrocarbonatite lava is extremely fluid and can flow very fast. Visits are not recommend without a guide.

Geologic Background. The symmetrical Ol Doinyo Lengai is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent stratovolcano, known to the Maasai as "The Mountain of God," rises abruptly above the broad plain south of Lake Natron in the Gregory Rift Valley. The cone-building stage ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatitic and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra ejections and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater and occasionally down the upper flanks. The depth and morphology of the northern crater have changed dramatically during the course of historical eruptions, ranging from steep crater walls about 200 m deep in the mid-20th century to shallow platforms mostly filling the crater. Long-term lava effusion in the summit crater beginning in 1983 had by the turn of the century mostly filled the northern crater; by late 1998 lava had begun overflowing the crater rim.

Information Contacts: Celia Nyamweru, Department of Anthropology, St. Lawrence University, Canton NY 13617 USA (URL: http://blogs.stlawu.edu/lengai/); Joerg Keller, IMPG, Albert-Ludwig-University Freiburg, Albertstrasse 23b, 79104 Freiburg, Germany; Christoph Weber, Volcano Expeditions International, Friesenstrasse 20, 42107 Wuppertal, Germany (URL: http://www.Vulkanexpeditionen.de); Frederick Belton, 3555 Philsdale Ave., Memphis, TN 38111 USA (URL: http://oldoinyolengai.pbworks.com/); Marc Szeglat (contact for video-film clips), Duelmenerstrasse 11, 46117 Oberhausen, Germany (URL: http://www.vulkane.net).


Merapi (Indonesia) — December 2000 Citation iconCite this Report

Merapi

Indonesia

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

All times are local (unless otherwise noted)


Dome failure and growth during January 2001; over 30 pyroclastic flows

Eruptive activity increased markedly at Merapi during the period of 26 December 2000-22 January 2001. Instrumental monitoring first recorded a significant increase in seismicity, expressed in both shallow and deep volcanic earthquakes, during 26 December-1 January. Visual observations were hindered during this time because of hazy conditions, and VSI maintained a hazard status of 2 (on a scale of 1-4) for Merapi.

Activity continued to increase during 2-8 January. Atmospheric conditions were clearer, allowing observation of a 1,500-m-high plume above the summit. Lava avalanches flowed ~1 km from the summit down to the Sat River. Seismicity remained high, again with a significant number of shallow and deep volcanic earthquakes, and was dominated by multi-phase and avalanche earthquakes.

During 9-15 January, activity again increased with respect to the previous week. Accordingly, VSI elevated Merapi's hazard status to 3. Observers noted a light-colored, variable-density, low-pressure ash plume that rose 500 m above the summit. Glowing lava avalanches flowed into the headwaters of the Lamat, Sat, and Senowo Rivers, up to 2 km from the summit. On 14 January, 29 pyroclastic flows traveled down the volcano's flanks into the three above-mentioned rivers and reached up to 4 km from their source. During the week, lava avalanches and pyroclastic flows occurred with an average interval of 0.5-1 hours.

Visual observations from several post observatories during 16-22 January revealed ash eruptions, glowing lava flows and avalanches, and pyroclastic flows. Merapi ejected a dense, light-colored ash plume under medium to high pressure. Ash rose 850-1,300 m above the summit, with an estimated emission volume of 95 metric tons/day. Ashfall occurred on the surrounding areas of Babadan, Kaliurang, and Ngepos. Glowing lava avalanches, with more than 150 occurring per day, reached as far as 3.5 km from the summit into the Bebeng, Sat, and Senowo Rivers. Observers suggested more than one source vent for these flows. More than 20 pyroclastic flows occurred daily during the week, sending ash and gas a maximum of 3 km down the Bebeng River, 4.5 km down the Sat River, and an unreported distance down the Senowo River.

The Darwin VAAC issued an ash advisory on 19 January to advise pilots of ash emanating from Merapi. The advisory reported an ash plume up to an altitude of ~3,400 m. Prevailing winds were projected to carry ash to the E or SE; cloud cover prevented any further descriptions.

A new lava dome, termed "2001," grew on top of the 1998 dome that had collapsed around 16 January. Growth appeared continuous with the glowing dome visible at night. Researchers speculated that the failure of the 1998 dome and the instability of the new dome accounted for the high frequency and volume of pyroclastic flows.

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


Momotombo (Nicaragua) — December 2000 Citation iconCite this Report

Momotombo

Nicaragua

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

All times are local (unless otherwise noted)


Previously unreported low activity during March and April 2000

This report discusses previously unreported information about the activity during March and April 2000. This interval of low activity occurred prior to one with heightened seismicity during May and June 2000 (BGVN 25:06).

The seismic swarm that began in May 2000 reached its peak during 9-11 June when the INETER seismic network registered over 500 earthquakes (BGVN 25:06). Many of the earthquake magnitudes were between 3.4 and 4.1, and the small epicentral area was directly under a geothermal plant on the S slope of the volcano. INETER reported that prior to the seismic activity, in March 2000, seismicity was low, with only two seismic events during the month. They did not visit the volcano during March.

On 9 April, Pierre Delmelle of the Université de Montréal along with local guides visited the volcano's crater. According to Delmelle, the crater was horseshoe-shaped and recent landslides had occurred down the crater's walls. He also noted that the majority of the fumarolic activity took place in the bottom of the crater. Gas was released from the fumaroles with very weak pressure, and temperatures ranged from 100 to 460°C. INETER personnel made a previous trip to the crater interior in September 1998 and found a lack of fresh landslides down the crater walls; fumarolic gas temperatures were 79 to 235°C.

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

Information Contacts: Wilfried Strauch and Virginia Tenorio, Dirección General de Geofísica, Instituto Nicaragüense de Estudios Territoriales (INETER), Apartado 1761, Managua, Nicaragua (URL: http://www.ineter.gob.ni/); Pierre Delmelle, Département de Géologie, Université de Montréal, Montréal, Québec H3C 3J7, Canada.


Popocatepetl (Mexico) — December 2000 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


December set records in tremor, dome extrusion rates, SO2 flux, and tilt

Around the end of the year 2000 and in January 2001 Popocatépetl extruded dome lavas at record-setting rates and amassed the largest active dome ever recorded on the volcano. The seismic energy released in one 25-hour interval in mid-December was greater than the accumulated energy for any entire year for which measurements are available. The highest plume of the interval rose to ~8 km above the summit crater.

During late 2000 into January 2001, but particularly in December, tremor reached the biggest amplitudes yet recorded during this multi-year crisis; it was felt by people 12-14 km distant, and one tremor episode prevailed for ~10 hours. Another episode saturated instruments to the point of damage and drove tiltmeters in dramatic oscillations.

Although impressive plumes had been seen before in this crisis, for the first time hot ash and gases began escaping the summit crater regularly, accompanied by pyroclastic flows and mudflows. The longest pyroclastic flow reached a runout distance of ~8 km. Preliminary photo analysis made during episodes of harmonic tremor in mid-December led to lava extrusion-rate estimates that were more than an order of magnitude higher than those typically seen at stratovolcanoes. During mid-December, sulfur dioxide (SO2) fluxes reached ten to twenty times larger than the volcano's typical ~5,000 tons/day.

Although later Bulletin reports will provide more details, what follows here are critical highlights for assessing the behavior through 29 January. The report was provided by Servando de la Cruz-Reyna, Carlos Valdés-Gonzalez, Roberto Quaas-Weppen, and affiliated CENAPRED scientists noted below.

Relative quiet followed by unrest. The previous episode of dome growth took place in February 2000, resulting in the smallest of all domes grown since 1996 (see BGVN 25:01). After a period of relative quiescence, unrest followed at Popocatépetl in early September 2000 (BGVN 25:10). This marked the beginning of a new episode.

September unrest was marked by two seismic observations. First, harmonic tremor appeared in the peak of the exhalation signals. Second, tectono-volcanic earthquakes below the crater were followed by long-duration explosive eruptions that generated higher-altitude plumes. GOES satellite imagery depicted strong thermal anomalies in the crater. Still, only comparatively minor dome growth was detected in mid-September, and this same pattern continued during early November. A variable, somewhat reduced level of activity continued into early December.

Escalation in December 2000. As discussed below, RSAM values climbed precipitously during a 7-day interval in mid-December. Prior to that, on 2 December an ash emission of moderate-to-large size lasted about 90 minutes. On 6 December, nine low-magnitude earthquakes (M ~1.7-2.4) occurred followed by a similar swarm on 8-9 December. These earthquakes, in turn, were followed by a period of low-frequency harmonic tremor that lasted about 5 minutes. Although brief, this tremor had the largest amplitude recorded since this eruptive period began in 1994.

Particularly during December, tiltmeters, for the first time since their installation, registered all of the large tremor signals (figure 30). Tilt oscillation amplitudes were typically in the range of 100 µrad, reaching peak-to-peak values near 200 µrad. Seismicity during 11-18 December was extremely high (figures 31 and 32).

Figure (see Caption) Figure 30. Tilt at Popocatépetl recorded by various stations for 11-20 December 2000. The large tilt displacements occurred in conjunction with high-amplitude tremor. The x and y directions are neither radial nor strictly tangential in orientation. The two axes lie at right angles on a horizontal plane such that a line 45 degrees away and bisecting both these axes trends through the center of the volcano. Courtesy of CENAPRED.

Eruptive activity increased on 12 December 2000 with frequent ash-bearing emissions (up to 200 per day), some of them reaching about 5-6 km above the volcano's summit. During the following night observers saw incandescence and small amounts of hot debris. Similar activity and longer-duration eruptions during 13-15 December produced light ashfalls on towns around the volcano.

Early on 15 December more episodes of high-amplitude, low-frequency harmonic tremor were detected, lasting a few minutes. At 1404, the low-frequency harmonic tremor grew to a continuous signal, with amplitudes peaking on all the monitoring stations, including the most distant one. These signals were strong enough to be felt by residents 12-14 km away, and to be detected at stations of the Mexican Seismological Network as far as 150 km from the volcano. This tremor episode remained at constant intensity for about 10 hours, and may have stemmed from very high rates of lava extrusion.

Starting early on 16 December activity underwent a dramatic drop that was reversed 16 hours later by a return of low-frequency harmonic tremor of increasing amplitude. This tremor again saturated all monitoring stations; it lasted about 9.5 hours. The amplitudes of the signals were so high that pen drivers and several styli of the paper-drum recorders were damaged. A still-larger tremor episode took place on 18-19 December.

Figures 31 and 32 illustrate the seismic traces and cumulative RSAM data. RSAM peaked during an interval of slightly over 7 days in mid-December, when low-frequency tremor prevailed for ~25 hours and the seismic energy released exceeded that of the rest of the year 2000. Actually, the peak surpassed that accumulated during any previous entire year for which records exist (including 1997, see figure 32).

Figure (see Caption) Figure 31. Paper-drum records from Popocatépetl photographed while laid out on a flat surface. The records depict the record-setting seismic signals at Canario station (PPPN) on 30 June 1997 (labeled "a") and on 18-19 December 2000 (labeled "b"). Some of the records in the latter set (b, central to upper left) were re-scaled when the maximum pen displacement was shifted from 8 cm to 4 cm in order to stop damaging pens and motors during ongoing saturating oscillations. It is clear that the amplitude and duration of the 18-19 December 2000 events greatly exceeded those from 30 June 1997. Prior to mid-December, the 30 June 1997 events represented the largest amplitude tremor seen since 1994. Courtesy of CENAPRED.
Figure (see Caption) Figure 32. Real-time seismic amplitude measurement (RSAM) plots for two Popocatépetl stations for the years 1997-8 and 2000, illustrating the extremely high seismic energy release seen in a time interval just over 7 days long (11-18 December 2000). This interval includes the acute increase seen on 18 December 2000. This ~7-day interval's energy release was eightfold larger than the total annual release in 1997. Courtesy of CENAPRED.

The episodes of quiescence and high-amplitude, low-frequency harmonic tremors occurred in such a pattern that they could be described as a load-and-discharge model, as suggested by the time-predictable model of Shimazaki and Nagata (1980). Using this paradigm, workers forecast the onset of the 18 December eruption and tremor episode.

Aerial photos taken on 16 December showed significant dome growth inside the crater (figure 33) and allowed correlation of the episodes of high amplitude, low-frequency harmonic tremor with periods of lava extrusion at very high rates. Analysis of the photos indicated that the dome grew at an average rate of ~180-200 m3/s during the episodes of intense harmonic tremor. This rate, which was not sustained, was about two orders of magnitude higher than any other previously observed.

Figure (see Caption) Figure 33. A photograph taken looking into the crater at Popocatépetl, as viewed from the N on 16 December 2000. The substantial glacier on the N side lies covered by ash. Courtesy of CENAPRED.

At Popocatépetl, correlation spectrometer (COSPEC) measurements of SO2 flux have had yearly averages on the order of 5,000 metric tons/day (t/d). In contrast, during 13-19 December the estimates were in excess of 50,000 t/d. On 19 December the reported value was near 100,000 t/d.

Civil authorities were made aware of the high magnitude of the monitoring signals, the very high rate of lava production, and the growth of the largest dome yet observed. This motivated them to constitute, on 15-16 December, an emergency board. They declared a further increase in the alert level and defined a security radius of 13 km. This radius was suggested to include at least some of the most vulnerable towns, like Santiago Xalitzintla (centered ~15 km NE of the crater) and San Pedro Benito Juarez (with a few residences 10 km SE of the crater, but the main town at 12 km from it). Santiago Xalitzintla sits downstream of the E side of the largest glacier along one of the main N-flank drainages. San Pedro Benito Juarez lies on a fracture zone on the SE flank, an area where many of the largest tectono-volcanic earthquakes were located. Additionally, increased deformation was also detected using the geodetic network located on that fault. San Pedro Benito Juarez is an isolated town closest to a notch in the SE crater rim. This notch is believed to have formed by collapse on 24 February 1664 during an eruption similar to the current one.

Preventive evacuation of Santiago Xalitzintla, San Pedro Benito Juarez, and other towns began on late 15 December and early 16 December. The decisions regarding which other towns should be evacuated were made by authorities at the state and municipal level. This caused some towns, well outside the security radius of 13 km, to also be evacuated by decision of their mayors. About 41,000 people left the area. Around half left the region by their own will and means. The other half used resources provided by local civil protection authorities. Of these, ~14,000 accepted transportation to shelters where they remained for about 10 days. Others moved to stay with relatives or friends.

The total volume of fresh lava accumulated within the crater of Popocatépetl was estimated to be between 15 and 19 million cubic meters on 18 December, exceeding the combined volume of all the previous domes (figures 33 and 35). The estimated vertical growth rate of the dome was such that another 20 or 30 hours of tremor associated with the above-mentioned lava production rate could potentially have enabled the dome to begin escaping the confines of the crater. The rate slowed, however, and the dome's upper surface remained well within the crater (figures 33 and 35).

As anticipated by the applying the above-mentioned model, after a three-day period of relative quiescence, on the afternoon of 18 December, a new eruption began. The relatively low-explosivity, yet long-lasting eruption of 18-19 December (figure 34) ejected large amounts of hot debris on the flanks of the volcano in three episodes of incandescent fountaining. Ejected hot debris is believed to have ultimately flowed a maximum distance of 5-6 km from the crater. Some images of these eruptions were distributed by some news media, which had installed cameras around the volcano and broadcast images in real time. After 19 December activity decreased noticeably. The next expected period of unrest, suggested by the time-predictable model to ensue near 23 December (figure 35), did not occur, likely indicating that the rate of magma supply had changed. What was believed to be the first dome-destruction explosion of this episode occurred on 24 December, ejecting incandescent debris to a distance of 3.5 km from the volcano, and producing an ash plume estimated to reach 5 km above the crater. When the nature and size of this event was understood, authorities reduced the security radius to 12 km. No towns lie within that radius, and accordingly many people returned to their homes.

Figure (see Caption) Figure 34. An ash-bearing eruption column rises from Popocatépetl on 19 December 2000, viewed from the N. This kind of activity was common during the energetic mid-December time interval and stimulated international attention (e.g. the media and websites of Reuters, Stromboli Online, and others). Courtesy of CENAPRED.
Figure (see Caption) Figure 35. Aerial photograph taken looking into the crater at Popocatépetl, as seen from the NE on 23 December. Courtesy of CENAPRED.

Later explosive events failed to excavate substantial portions of the new dome. The current estimate as of 16 January 2001 was that ~10-20% of the new dome volume has been blown out by explosions recorded after 18 December 2000. In many of the previous dome growth-and-destruction episodes since 1996, most of the dome mass has been removed by small to moderate (VEI <= 2) explosions; a similar scenario may play out in the near future.

After several weeks of relative calm, significant activity resumed at Popocatépetl on 22 January. At 1458 a M 2.8 volcano-tectonic earthquake occurred on the E flank. This event was possibly a precursor to a large ash emission that started at 1615, and initially produced an ash plume several kilometers in height. Eight minutes later observers saw a more explosive phase throwing incandescent fragments around the crater. After several more minutes, pyroclastic flows were generated and moved 4-6 km down several ravines on the N flank. Ash emission from the crater was continuous and punctuated by intermittent explosions. By 1640, the ash plume towered more than 8 km above the summit crater. At 1800 fluctuating harmonic tremor, similar to that of December, was registered. At times the signals again reached saturation amplitudes; the tremor could have been associated with magma intrusion into the base of the crater, an idea also suggested to explain previous tremor events. Harmonic tremor lasted for ~30 minutes. Ashfall was documented in Santiago Xalitzintla, Atlixico, and parts of Puebla and Tetela del Volcán. At 2200 it was possible to see ejected incandescent fragments that fell up to 1 km from the crater. On 29 January (figure 36), pyroclastic flows caused some glacial melting. The pyroclastic flows initially reached up to 8 km from their source, halting in the drainage upstream of Santiago Xalitzintla. They triggered some glacial melting and in early February their deposits were remobilized and came to rest about 15 km from the crater, about 2 km upstream of Santiago Xalitzintla. As of 29 January Popocatépetl remained at a Stage 3 Yellow alert.

Figure (see Caption) Figure 36. Popocatépetl on 29 January photographed looking S. The image captured the forceful ejection of an ash-laden cloud. Courtesy of CENAPRED.

Reference. Shimazaki and Nagata,1980, Time-predictable recurrence model for large earthquakes: Geophys Res. Lett. 7, p. 279-282.

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

Information Contacts: Carlos Valdés-Gonzalez, Roberto Quaas-Weppen, E. Guevara, A. Martinez, G. Castelán, S. Alcocer, C. Gutiérrez, G. Espitia, F. Galicia, M. Galicia, A. Gomez, G. Jiménez, C. Morquecho, J. Ortiz, E. Ramos, H. Romero, Centro Nacional de Prevencion de Desastres (CENAPRED), Delfin Madrigal 665, Col. Pedregal de Santo Domingo, Coyoacán, 04360, México D.F. (URL: https://www.gob.mx/cenapred/); Servando de la Cruz-Reyna, Instituto de Geofisica, UNAM, Coyoacán 04510, México D.F., México.

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  Obituaries

Misc 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 subject.

Additional Reports  False Reports