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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

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

Sheveluch (Russia) Lava dome growth and thermal anomalies continue through April 2020, but few ash explosions

Dukono (Indonesia) Numerous ash explosions continue through March 2020

Etna (Italy) Strombolian explosions and ash emissions continue, October 2019-March 2020

Merapi (Indonesia) Explosions produced ash plumes, ashfall, and pyroclastic flows during October 2019-March 2020



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).


Sheveluch (Russia) — May 2020 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Lava dome growth and thermal anomalies continue through April 2020, but few ash explosions

The eruption at Sheveluch has continued for more than 20 years, with strong explosions that have produced ash plumes, lava dome growth, hot avalanches, numerous thermal anomalies, and strong fumarolic activity (BGVN 44:05). During this time, there have been periods of greater or lesser activity. The most recent period of increased activity began in December 2018 and continued through October 2019 (BGVN 44:11). This report covers activity between November 2019 to April 2020, a period during which activity waned. The volcano is monitored by the Kamchatka Volcanic Eruptions Response Team (KVERT) and Tokyo Volcanic Ash Advisory Center (VAAC).

During the reporting period, KVERT noted that lava dome growth continued, accompanied by incandescence of the dome blocks and hot avalanches. Strong fumarolic activity was also present (figure 53). However, the overall eruption intensity waned. Ash plumes sometimes rose to 10 km altitude and drifted downwind over 600 km (table 14). The Aviation Color Code (ACC) remained at Orange (the second highest level on a four-color scale), except for 3 November when it was raised briefly to Red (the highest level).

Figure (see Caption) Figure 53. Fumarolic activity of Sheveluch’s lava dome on 24 January 2020. Photo by Y. Demyanchuk; courtesy of KVERT.

Table 14. Explosions and ash plumes at Sheveluch during November 2019-April 2020. Dates and times are UTC, not local. Data courtesy of KVERT and the Tokyo VAAC.

Dates Plume Altitude (km) Drift Distance and Direction Remarks
01-08 Nov 2019 -- 640 km NW 3 November: ACC raised to Red from 0546-0718 UTC before returning to Orange.
08-15 Nov 2019 9-10 1,300 km ESE
17-27 Dec 2019 6.0-6.5 25 km E Explosions at about 23:50 UTC on 21 Dec.
20-27 Mar 2020 -- 45 km N 25 March: Gas-and-steam plume containing some ash.
03-10 Apr 2020 10 km 526 km SE 8 April: Strong explosion at 1910 UTC.
17-24 Apr 2020 -- 140 km NE Re-suspended ash plume.

KVERT reported thermal anomalies over the volcano every day, except for 25-26 January, when clouds obscured observations. During the reporting period, thermal anomalies, based on MODIS satellite instruments analyzed using the MODVOLC algorithm recorded hotspots on 10 days in November, 13 days in December, nine days in January, eight days in both February and March, and five days in April. The MIROVA (Middle InfraRed Observation of Volcanic Activity) volcano hotspot detection system, also based on analysis of MODIS data, detected numerous hotspots every month, almost all of which were of moderate radiative power (figure 54).

Figure (see Caption) Figure 54. Thermal anomalies at Sheveluch continued at elevated levels during November 2019-April 2020, as seen on this MIROVA Log Radiative Power graph for July 2019-April 2020. Courtesy of MIROVA.

High sulfur dioxide levels were occasionally recorded just above or in the close vicinity of Sheveluch by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite, but very little drift was observed.

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

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), 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/); Tokyo Volcanic Ash Advisory Center (VAAC), 1-3-4 Otemachi, Chiyoda-ku, Tokyo, Japan (URL: http://ds.data.jma.go.jp/svd/vaac/data/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); 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/).


Dukono (Indonesia) — May 2020 Citation iconCite this Report

Dukono

Indonesia

1.693°N, 127.894°E; summit elev. 1229 m

All times are local (unless otherwise noted)


Numerous ash explosions continue through March 2020

The ongoing eruption at Dukono is characterized by frequent explosions that send ash plumes to about 1.5-3 km altitude (0.3-1.8 km above the summit), although a few have risen higher. This type of typical activity (figure 13) continued through at least March 2020. The ash plume data below (table 21) were primarily provided by the Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) and the Darwin Volcanic Ash Advisory Centre (VAAC). During the reporting period of October 2019-March 2020, the Alert Level remained at 2 (on a scale of 1-4) and the public was warned to remain outside of the 2-km exclusion zone.

Table 21. Monthly summary of reported ash plumes from Dukono for October 2019-March 2020. The direction of drift for the ash plume through each month was highly variable; notable plume drift each month was only indicated in the table if at least two weekly reports were consistent. Data courtesy of the Darwin VAAC and PVMBG.

Month Plume Altitude (km) Notable Plume Drift
Oct 2019 1.8-3 Multiple
Nov 2019 1.8-2.3 E, SE, NE
Dec 2019 1.8-2.1 E, SE
Jan 2020 1.8-2.1 E, SE, SW, S
Feb 2020 2.1-2.4 S, SW
Mar 2020 1.5-2.3 Multiple
Figure (see Caption) Figure 13.Satellite image of Dukono from Sentinel-2 on 12 November 2019, showing an ash plume drifting E. Image uses natural color rendering (bands 4, 3, 2). Courtesy of Sentinel Hub Playground.

During the reporting period, high levels of sulfur dioxide were only recorded above or near the volcano during 30-31 October and 4 November 2019. High levels were recorded by the Ozone Mapping and Profiler Suite (OMPS) instrument aboard the Suomi National Polar-orbiting Partnership (NPP) satellite on 30 October 2019, in a plume drifting E. The next day high levels were also recorded by the TROPOspheric Monitoring Instrument (TROPOMI) aboard the Copernicus Sentinel-5 Precursor satellite on 31 October (figure 14) and 4 November 2019, in plumes drifting SE and NE, respectively.

Figure (see Caption) Figure 14. Sulfur dioxide emission on 31 October 2019 drifting E, probably from Dukono, as recorded by the TROPOMI instrument aboard the Sentinel-5P satellite. Courtesy of NASA Global Sulfur Dioxide Monitoring Page.

Geologic Background. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); 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).


Etna (Italy) — April 2020 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Strombolian explosions and ash emissions continue, October 2019-March 2020

Mount Etna is a stratovolcano located on the island of Sicily, Italy, with historical eruptions that date back 3,500 years. The most recent eruptive period began in September 2013 and has continued through March 2020. Activity is characterized by Strombolian explosions, lava flows, and ash plumes that commonly occur from the summit area, including the Northeast Crater (NEC), the Voragine-Bocca Nuova (or Central) complex (VOR-BN), the Southeast Crater (SEC, formed in 1978), and the New Southeast Crater (NSEC, formed in 2011). The newest crater, referred to as the "cono della sella" (saddle cone), emerged during early 2017 in the area between SEC and NSEC. This reporting period covers information from October 2019 through March 2020 and includes frequent explosions and ash plumes. The primary source of information comes from the Osservatorio Etneo (OE), part of the Catania Branch of Italy's Istituo Nazionale di Geofisica e Vulcanologica (INGV).

Summary of activity during October 2019-March 2020. Strombolian activity and gas-and-steam and ash emissions were frequently observed at Etna throughout the entire reporting period, according to INGV and Toulouse VAAC notices. Activity was largely located within the main cone (Voragine-Bocca Nuova complex), the Northeast Crater (NEC), and the New Southeast Crater (NSEC). On 1, 17, and 19 October, ash plumes rose to a maximum altitude of 5 km. Due to constant Strombolian explosions, ground observations showed that a scoria cone located on the floor of the VOR Crater had begun to grow in late November and again in late January 2020. A lava flow was first detected on 6 December at the base of the scoria cone in the VOR Crater, which traveled toward the adjacent BN Crater. Additional lava flows were observed intermittently throughout the reporting period in the same crater. On 13 March, another small scoria cone had formed in the main VOR-BN complex due to Strombolian explosions.

MIROVA (Middle InfraRed Observation of Volcanic Activity) analysis of MODIS satellite data shows multiple episodes of thermal activity varying in power from 22 June 2019 to March 2020 (figure 286). The power and frequency of these thermal anomalies significantly decreased between August to mid-September. The pulse of activity in mid-September reflected a lava flow from the VOR Crater (BGVN 44:10). By late October through November, thermal anomalies were relatively weaker and less frequent. The next pulse in thermal activity reflected in the MIROVA graph occurred in early December, followed by another shortly after in early January, both of which were due to new lava flows from the VOR Crater. After 9 January the thermal anomalies remained frequent and strong; active lava flows continued through March accompanied by Strombolian explosions, gas-and-steam, SO2, and ash emissions. The most recent distinct pulse in thermal activity was seen in mid-March; on 13 March, another lava flow formed, accompanied by an increase in seismicity. This lava flow, like the previous ones, also originated in the VOR Crater and traveled W toward the BN Crater.

Figure (see Caption) Figure 286. Multiple episodes of varying activity at Etna from 22 June 2019 through March 2020 were reflected in the MIROVA thermal energy data (Log Radiative Power). Courtesy of MIROVA.

Activity during October-December 2019. During October 2019, VONA (Volcano Observatory Notice for Aviation) notices issued by INGV reported ash plumes rose to a maximum altitude of 5 km on 1, 17, and 19 October. Strombolian explosions occurred frequently. Explosions were detected primarily in the VOR-BN Craters, ejecting coarse pyroclastic material that fell back into the crater area and occasionally rising above the crater rim. Ash emissions rose from the VOR-BN and NEC while intense gas-and-steam emissions were observed in the NSEC (figure 287). Between 10-12 and 14-20 October fine ashfall was observed in Pedara, Mascalucia, Nicolosi, San Giovanni La Punta, and Catania. In addition to these ash emissions, the explosive Strombolian activity contributed to significant SO2 plumes that drifted in different directions (figure 288).

Figure (see Caption) Figure 287. Webcam images of ash emissions from the NE Crater at Etna from the a) CUAD (Catania) webcam on 10 October 2019; b) Milo webcam on 11 October 2019; c) Milo webcam on 12 October 2019; d) M.te Cagliato webcam on 13 October 2019. Courtesy of INGV (Report 42/2019, ETNA, Bollettino Settimanale, 07/10/2019 - 13/10/2019, data emissione 15/10/2019).
Figure (see Caption) Figure 288. Strombolian activity at Etna contributed to significant SO2 plumes that drifted in multiple directions during the intermittent explosions in October 2019. Top left: 1 October 2019. Top right: 2 October 2019. Middle left: 15 October 2019. Middle right: 18 October 2019. Bottom left: 13 November 2019. Bottom right: 1 December 2019. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.

The INGV weekly bulletin covering activity between 25 October and 1 November 2019 reported that Strombolian explosions occurred at intervals of 5-10 minutes from within the VOR-BN and NEC, ejecting incandescent material above the crater rim, accompanied by modest ash emissions. In addition, gas-and-steam emissions were observed from all the summit craters. Field observations showed the cone in the crater floor of VOR that began to grow in mid-September 2019 had continued to grow throughout the month. During the week of 4-10 November, Strombolian activity within the Bocca Nuova Crater was accompanied by gas-and-steam emissions. The explosions in the VOR Crater occasionally ejected incandescent ejecta above the crater rim (figures 289 and 290). For the remainder of the month Strombolian explosions continued in the VOR-BN and NEC, producing sporadic ash emissions. Isolated and discontinuous explosions in the New Southeast Crater (NSEC) also produced fine ash, though gas-and-steam emissions still dominated the activity at this crater. Additionally, the explosions from these summit craters were frequently accompanied by strong SO2 emissions that drifted in different directions as discrete plumes.

Figure (see Caption) Figure 289. Photo of Strombolian activity and crater incandescence in the Voragine Crater at Etna on 15 November 2019. Photo by B. Behncke, taken by Tremestieri Etneo. Courtesy of INGV (Report 47/2019, ETNA, Bollettino Settimanale, 11/11/2019 - 17/11/2019, data emissione 19/11/2019).
Figure (see Caption) Figure 290. Webcam images of summit crater activity during 26-29 November and 1 December 2019 at Etna. a) image recorded by the high-resolution camera on Montagnola (EMOV); b) and c) webcam images taken from Tremestieri Etneo on the southern slope of Etna showing summit incandescence; d) image recorded by the thermal camera on Montagnola (EMOT) showing summit incandescence at the NSEC. Courtesy of INGV (Report 49/2019, ETNA, Bollettino Settimanale, 25/11/2019 - 01/12/2019, data emissione 03/12/2019).

Frequent Strombolian explosions continued through December 2019 within the VOR-BN, NEC, and NSEC Craters with sporadic ash emissions observed in the VOR-BN and NEC. On 6 December, Strombolian explosions increased in the NSEC; webcam images showed incandescent pyroclastic material ejected above the crater rim. On the morning of 6 December a lava flow was observed from the base of the scoria cone in the VOR Crater that traveled toward the adjacent Bocca Nuova Crater. INGV reported that a new vent opened on the side of the saddle cone (NSEC) on 11 December and produced explosions until 14 December.

Activity during January-March 2020. On 9 January 2020 an aerial flight organized by RAI Linea Bianca and the state police showed the VOR Crater continuing to produce lava that was flowing over the crater rim into the BN Crater with some explosive activity in the scoria cone. Explosive Strombolian activity produced strong and distinct SO2 plumes (figure 291) and ash emissions through March, according to the weekly INGV reports, VONA notices, and satellite imagery. Several ash emissions during 21-22 January rose from the vent that opened on 11 December. According to INGV’s weekly bulletin for 21-26 January, the scoria cone in the VOR crater produced Strombolian explosions that increased in frequency and contributed to rapid cone growth, particularly the N part of the cone. Lava traveled down the S flank of the cone and into the adjacent Bocca Nuova Crater, filling the E crater (BN-2) (figure 292). The NEC had discontinuous Strombolian activity and periodic, diffuse ash emissions.

Figure (see Caption) Figure 291. Distinct SO2 plumes drifting in multiple directions from Etna were visible in satellite imagery as Strombolian activity continued through March 2020. Top left: 21 January 2020. Top right: 2 February 2020. Bottom left: 10 March 2020. Bottom right: 19 March 2020. Captured by the TROPOMI instrument on the Sentinel 5P satellite, courtesy of NASA Global Sulfur Dioxide Monitoring Page.
Figure (see Caption) Figure 292. a) A map of the lava field at Etna showing cooled flows (yellow) and active flows (red). The base of the scoria cone is outlined in black while the crater rim is outlined in red. b) Thermal image of the Bocca Nuova and Voragine Craters. The bright orange is the warmest temperature measure in the flow. Courtesy of INGV, photos by Laboratorio di Cartografia FlyeEye Team (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

Strombolian explosions continued into February 2020, accompanied by ash emissions and lava flows from the previous months (figure 293). During 17-23 February, INGV reported that some subsidence was observed in the central portion of the Bocca Nuova Crater. During 24 February to 1 March, the Strombolian explosions ejected lava from the VOR Crater up to 150-200 m above the vent as bombs fell on the W edge of the VOR crater rim (figure 294). Lava flows continued to move into the W part of the Bocca Nuova Crater.

Figure (see Caption) Figure 293. Webcam images of A) Strombolian activity and B) effusive activity fed by the scoria cone grown inside the VOR Crater at Etna taken on 1 February 2020. C) Thermal image of the lava field produced by the VOR Crater taken by L. Lodato on 3 February (bottom left). Image of BN-1 taken by F. Ciancitto on 3 February in the summit area (bottom right). Courtesy of INGV; Report 06/2020, ETNA, Bollettino Settimanale, 27/01/2020 - 02/02/2020, data emissione 04/02/2020 (top) and Report 07/2020, ETNA, Bollettino Settimanale, 03/02/2020 - 09/02/2020, data emissione 11/02/2020 (bottom).
Figure (see Caption) Figure 294. Photos of the VOR intra-crater scoria cone at Etna: a) Strombolian activity resumed on 25 February 2020 from the SW edge of BN taken by B. Behncke; b) weak Strombolian activity from the vent at the base N of the cone on 29 February 2020 from the W edge of VOR taken by V. Greco; c) old vent present at the base N of the cone, taken on 17 February 2020 from the E edge of VOR taken by B. Behncke; d) view of the flank of the cone, taken on 24 February 2020 from the W edge of VOR taken by F. Ciancitto. Courtesy of INGV (Report 10/2020, ETNA, Bollettino Settimanale, 24/02/2020 - 01/03/2020, data emissione 03/03/2020).

During 9-15 March 2020 Strombolian activity was detected in the VOR Crater while discontinuous ash emissions rose from the NEC and NSEC. Bombs were found in the N saddle between the VOR and NSEC craters. On 9 March, a small scoria cone that had formed in the Bocca Nuova Crater and was ejecting bombs and lava tens of meters above the S crater rim. The lava flow from the VOR Crater was no longer advancing. A third scoria cone had formed on 13 March NE in the main VOR-BN complex due to the Strombolian explosions on 29 February. Another lava flow formed on 13 March, accompanied by an increase in seismicity. The weekly report for 16-22 March reported Strombolian activity detected in the VOR Crater and gas-and-steam and rare ash emissions observed in the NEC and NSEC (figure 295). Explosions in the Bocca Nuova Crater ejected spatter and bombs 100 m high.

Figure (see Caption) Figure 295. Map of the summit crater area of Etna showing the active vents and lava flows during 16-22 March 2020. Black hatch marks indicate the crater rims: BN = Bocca Nuova, with NW BN-1 and SE BN-2; VOR = Voragine; NEC = North East Crater; SEC = South East Crater; NSEC = New South East Crater. Red circles indicate areas with ash emissions and/or Strombolian activity, yellow circles indicate steam and/or gas emissions only. The base is modified from a 2014 DEM created by Laboratorio di Aerogeofisica-Sezione Roma 2. Courtesy of INGV (Report 13/2020, ETNA, Bollettino Settimanale, 16/03/2020 - 22/03/2020, data emissione 24/03/2020).

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: Sezione di Catania - Osservatorio Etneo, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: http://www.ct.ingv.it/it/); Toulouse Volcanic Ash Advisory Center (VAAC), Météo-France, 42 Avenue Gaspard Coriolis, F-31057 Toulouse cedex, France (URL: http://www.meteo.fr/aeroweb/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Boris Behncke, Sonia Calvari, and Marco Neri, Istituto Nazionale di Geofisica e Vulcanologia (INGV), Sezione di Catania, Piazza Roma 2, 95123 Catania, Italy (URL: https://twitter.com/etnaboris, Image at https://twitter.com/etnaboris/status/1183640328760414209/photo/1).


Merapi (Indonesia) — April 2020 Citation iconCite this Report

Merapi

Indonesia

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

All times are local (unless otherwise noted)


Explosions produced ash plumes, ashfall, and pyroclastic flows during October 2019-March 2020

Merapi is a highly active stratovolcano located in Indonesia, just north of the city of Yogyakarta. The current eruption episode began in May 2018 and was characterized by phreatic explosions, ash plumes, block avalanches, and a newly active lava dome at the summit. This reporting period updates information from October 2019-March 2020 that includes explosions, pyroclastic flows, ash plumes, and ashfall. The primary reporting source of activity comes from Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG, the Center for Research and Development of Geological Disaster Technology, a branch of PVMBG) and Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM).

Some ongoing lava dome growth continued in October 2019 in the NE-SW direction measuring 100 m in length, 30 m in width, and 20 m in depth. Gas-and-steam emissions were frequent, reaching a maximum height of 700 m above the crater on 31 October. An explosion at 1631 on 14 October removed the NE-SW trending section of the lava dome and produced an ash plume that rose 3 km above the crater and extended SW for about 2 km (figures 90 and 91). The plume resulted in ashfall as far as 25 km to the SW. According to a Darwin VAAC notice, a thermal hotspot was detected in HIMAWARI-8 satellite imagery. A pyroclastic flow associated with the eruption traveled down the SW flank in the Gendol drainage. During 14-20 October lava flows from the crater generated block-and-ash flows that traveled 1 km SW, according to BPPTKG.

Figure (see Caption) Figure 90. An ash plume rising 3 km above Merapi on 14 October 2019.
Figure (see Caption) Figure 91. Webcam image of an ash plume rising above Merapi at 1733 on 14 October 2019. Courtesy of BPPTKG via Jaime S. Sincioco.

At 0621 on 9 November 2019, an eruption produced an ash plume that rose 1.5 km above the crater and drifted W. Ashfall was observed in the W region as far as 15 km from the summit in Wonolelo and Sawangan in Magelang Regency, as well as Tlogolele and Selo in Boyolali Regency. An associated pyroclastic flow traveled 2 km down the Gendol drainage on the SE flank. On 12 November aerial drone photographs were used to measure the volume of the lava dome, which was 407,000 m3. On 17 November, an eruption produced an ash plume that rose 1 km above the crater, resulting in ashfall as far as 15 km W from the summit in the Dukun District, Magelang Regency (figure 92). A pyroclastic flow accompanying the eruption traveled 1 km down the SE flank in the Gendol drainage. By 30 November low-frequency earthquakes and CO2 gas emissions had increased.

Figure (see Caption) Figure 92. An ash plume rising 1 km above Merapi on 17 November 2019. Courtesy of BPPTKG.

Volcanism was relatively low from 18 November 2019 through 12 February 2020, characterized primarily by gas-and-steam emissions and intermittent volcanic earthquakes. On 4 January a pyroclastic flow was recorded by the seismic network at 2036, but it wasn’t observed due to weather conditions. On 13 February an explosion was detected at 0516, which ejected incandescent material within a 1-km radius from the summit (figure 93). Ash plumes rose 2 km above the crater and drifted NW, resulting in ashfall within 10 km, primarily S of the summit; lightning was also seen in the plume. Ash was observed in Hargobinangun, Glagaharjo, and Kepuharjo. On 19 February aerial drone photographs were used to measure the change in the lava dome after the eruption; the volume of the lava had decreased, measuring 291,000 m3.

Figure (see Caption) Figure 93. Webcam image of an ash plume rising from Merapi at 0516 on 13 February 2020. Courtesy of MAGMA Indonesia and PVMBG.

An explosion on 3 March at 0522 produced an ash plume that rose 6 km above the crater (figure 94), resulting in ashfall within 10 km of the summit, primarily to the NE in the Musuk and Cepogo Boyolali sub-districts and Mriyan Village, Boyolali (3 km from the summit). A pyroclastic flow accompanied this eruption, traveling down the SSE flank less than 2 km. Explosions continued to be detected on 25 and 27-28 March, resulting in ash plumes. The eruption on 27 March at 0530 produced an ash plume that rose 5 km above the crater, causing ashfall as far as 20 km to the W in the Mungkid subdistrict, Magelang Regency, and Banyubiru Village, Dukun District, Magelang Regency. An associated pyroclastic flow descended the SSE flank, traveling as far as 2 km. The ash plume from the 28 March eruption rose 2 km above the crater, causing ashfall within 5 km from the summit in the Krinjing subdistrict primarily to the W (figure 94).

Figure (see Caption) Figure 94. Images of ash plumes rising from Merapi during 3 March (left) and 28 March 2020 (right). Images courtesy of BPPTKG (left) and PVMBG (right).

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

Information Contacts: Balai Penyelidikan dan Pengembangan Teknologi Kebencanaan Geologi (BPPTKG), Center for Research and Development of Geological Disaster Technology (URL: http://merapi.bgl.esdm.go.id/, Twitter: @BPPTKG); Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); Badan Nasional Penanggulangan Bencana (BNPB), National Disaster Management Agency, Graha BNPB - Jl. Scout Kav.38, East Jakarta 13120, Indonesia (URL: http://www.bnpb.go.id/, Twitter: https://twitter.com/BNPB_Indonesia); 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/); Jamie S. Sincioco, Phillipines (Twitter: @jaimessincioco, Image at https://twitter.com/jaimessincioco/status/1227966075519635456/photo/1).

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Bulletin of the Global Volcanism Network - Volume 21, Number 03 (March 1996)

Managing Editor: Richard Wunderman

Aira (Japan)

Frequent explosive ash eruptions continue

Akademia Nauk (Russia)

More details about the early January eruptions

Akutan (United States)

Seismicity declines with no eruption after two earthquake swarms

Arenal (Costa Rica)

Continued eruptions and recently updated map of lava flows

Avachinsky (Russia)

Increased seismicity and a higher steam plume

Etna (Italy)

Intermittent ash emissions and Strombolian activity from two summit craters

Fukutoku-Oka-no-Ba (Japan)

Emission of colored water and long discolored aqueous plumes

Hokkaido-Komagatake (Japan)

Additional information about the 5 March eruption

Irazu (Costa Rica)

Infrequent microseisms in February and March

Iwatesan (Japan)

Volcanic tremor registered again on 4 March

Karymsky (Russia)

More details about the early January eruptions

Kilauea (United States)

Heightened activity on 1-4 February followed by 10-day pause; bench construction

Kuchinoerabujima (Japan)

Increasing number of earthquakes since January

Kujusan (Japan)

Increased seismicity in late March, but plume remains ash-free

Langila (Papua New Guinea)

Vulcanian explosions continue

Manam (Papua New Guinea)

Inaudible, weak-to-moderate steaming from two craters

Oshima-Oshima (Japan)

Earthquakes and tremor detected

Pinatubo (Philippines)

Rainfall during October-November 1995 typhoons generates floods and lahars

Poas (Costa Rica)

Seismicity decreased roughly 10-fold since October 1995

Popocatepetl (Mexico)

Continued ash emissions; new lava dome and lava flows in summit crater

Rabaul (Papua New Guinea)

December-March ash deposits now 10-cm thick; seismicity continues

Rincon de la Vieja (Costa Rica)

Mild seismicity continues in February

Sangay (Ecuador)

Phreatic explosions, blue gas plumes, crater glow, and dome rockfalls

Socorro (Mexico)

Slight temperature increases at most summit fumaroles and hot springs

Soufriere Hills (United Kingdom)

Escalating dome growth spawns pyroclastic flows and another evacuation

Suwanosejima (Japan)

Weak ash eruptions in early March cause ashfalls

Ulawun (Papua New Guinea)

Still emitting low to moderate amounts of steam

Unzendake (Japan)

Tremor associated with minor tilt changes



Aira (Japan) — March 1996 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Frequent explosive ash eruptions continue

Minor activity continued at Minami-dake until mid-March, although the highest ash plume of the month rose 2,100 m above the crater on the 6th. Twelve explosive eruptions occurred on 18 March. Overall during March there were 88 eruptions, 69 of which were explosive. The monthly total ashfall measured 10 km W of the crater was 22 g/m2. Seismicity recorded 2.3 km NW of the crater during March consisted of 970 earthquakes and 773 tremors.

Geologic Background. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.


Akademia Nauk (Russia) — March 1996 Citation iconCite this Report

Akademia Nauk

Russia

53.98°N, 159.45°E; summit elev. 1180 m

All times are local (unless otherwise noted)


More details about the early January eruptions

According to the Institute of Volcanology (IV), the eruption on 2 January (BGVN 21:01) began around 0800. This activity was preceded by an upsurge in seismicity that started in April 1995. At 1926 on 31 December 1995, a M 5.8 earthquake occurred in the Kronotsky gulf, 50-60 km NE of the volcano. On 1 January at 2057 an earthquake of M 5.2 in the Karymsky region was followed at 2157 by a M 6.9 event centered ~25 km S of the volcano. During the next day there were more than 10 aftershocks of M >= 5.0. On 2 January at 1540, a group of IV volcanologists arrived by helicopter. Eruptive centers were observed near the summit and 5-6 km S in Karymsky Lake (maximum depth 115 m), which fills the Akademii Nauk caldera.

The eruption began with formation of a vent with a diameter of 20-30 m, located 50 m below the summit. Violent emissions of ash-rich gas jets rose to 1 km from another vent on the SW slope. Steam-and-gas jets, occasionally with black-colored matter, were also ejected to several hundred meters from beneath the surface of Karymsky Lake. The presumed eruptive center was 100-200 m from the shore in the NW sector of the lake. Turbulent steam-and-gas plumes rose 5-6 km above the surface from a 200-m-diameter area. Ice covering the lake had completely melted.

On 3 January the near-summit vent increased in size to 50 m in diameter. Gas and steam blasts alternated with ash ejections from the two simultaneously active vents on the volcano. Ash was usually ejected from the upper vent, and a white-colored plume was emitted from the lower vent. Ash ejections lasted 2-3 minutes, and gas blasts lasted 1.5-2 minutes. An ash-and-gas column rose 1-1.2 km and was blown E and SE by the wind. The surface of Karymsky Lake steamed intensely, sending clouds 800-1,000 m above the lake. Areas of green water were visible through breaks in the clouds, and a newly-formed black beach was seen. In the N and NE sector of the lake a narrow spit, beginning from the source of the Karymsky river and extending 250-300 m to the center of the lake, had formed. The water level in the lake had dropped a few meters. The upper reaches of the river had dried up, but on 2 January waves from the submarine eruption (up to 10 m high or more) overflowed the N shore, flooding a wide valley 1.5 km below the source. During a surveillance flight on 4 January, large areas of the valley were covered by black mud. The beach contained three fumarolic vents along the NE-trending fault zone. Within a radius of 500-800 m of the source of the Karymsky River, the surrounding snow-covered hills contained thousands of holes with diameters ranging from 10 cm to 1.5-2 m formed by lithic blocks ejected from the lake. The water level of the lake continued to fall because of intense evaporation.

Light-gray dacitic ash covered an area of about 150-200 km2. At a distance of 8 km from the volcano fractions ranging from 0.16 to 0.06 mm dominated. Estimates made by S.A. Fedotov indicated that on 2 and 3 January the ash ejection rate from the summit crater reached 3-4 tons/second.

Routine observations from 2 January through 11 February showed that the climactic phase of the subaqueous eruption continued for no more than 12-15 hours. That eruption consisted of frequent explosions during which a vapor-gas mixture with lithic material was ejected to the surface. In the N sector of the lake at the shore W of the Karymsky River, damaged trees provided evidence of two eruptive sources 500-600 m from each other. This zone contained the main concentration of bomb material ejected from the lake. A portion of the shoreline (150-200 m long and 5-15 m wide) E of the river sank several meters into the lake. The main eruption center was 500 m from the shore, but smaller peripheral centers were also observed. As a result of the eruption, in the NNW sector of the lake, a beach in the form of a wide 0.4 km2 cape was produced, as well as a narrow spit extending SE from the old shore. The length of the new shoreline was 2.4 km, and a large shoal was observed around the new peninsula. According to the preliminary estimates, the ejected deposits in the lake are at least 1 km2 in area and 5-10 x 106 m3 in volume.

Thermal springs that discharge at the S shore of Karymsky Lake were destroyed by ejecta from this eruption, and several new mud pots were formed; chemical composition of the solutions was unchanged. Near the center of the new beach, composed of sand-gravel and bomb material, a chain of five explosive vents with diameters from 1.5 to 30 m was observed. At the N end was a thermal site with a diameter of ~50 m that exhibited intense vapor emission and was covered by sublimates; visiting scientists detected a hydrogen sulfide odor. A dry funnel with a diameter of ~3 m and high gas emission at a temperature of 97°C was in the center of this site. Other explosion funnels had water at a depth of 1.2-1.5 m with temperatures from 33 to 70°C. The three funnels closest to the lake and on the opposite shore had gas emissions with temperatures of 97-98°C.

On 4 January run-off from the lake ceased owing to damming by ejected material. Analyses of water samples from the lake, river, and various hot springs in the area indicated that there had been chemical contributions to the lake water by an underlying magma body.

Geologic Background. The scenic lake-filled Akademia Nauk caldera is one of three volcanoes constructed within the mid-Pleistocene, 15-km-wide Polovinka caldera. Beliankin stratovolcano, in the SW part of Polovinka caldera, is eroded, but has been active in postglacial time (Sviatlovsky, 1959). Two nested calderas, 5 x 4 km Odnoboky and 3 x 5 km Akademia Nauk (also known as Karymsky Lake or Academii Nauk), were formed during the late Pleistocene, the latter about 30,000 years ago. Eruptive products varied from initial basaltic-andesite lava flows to late-stage rhyodacitic lava domes. Two maars, Akademia Nauk and Karymsky, subsequently formed at the southern and northern margins of the caldera lake, respectively. The northern maar, Karymsky, erupted about 6500 radiocarbon years ago and formed a small bay. The first historical eruption from Akademia Nauk did not take place until January 2, 1996, when a brief, day-long explosive eruption of unusual basaltic and rhyolitic composition occurred from vents beneath the NNW part of the caldera lake near Karymsky maar.

Information Contacts: G.A. Karpov, Ya.D. Muravyev, R.A. Shuvalov, S.M. Fazlullin, and V.N. Chebrov, Institute of Volcanology, Far East Division, Russian Academy of Sciences, Petropavlovsk-Kamchatsky, 683006, Russia.


Akutan (United States) — March 1996 Citation iconCite this Report

Akutan

United States

54.134°N, 165.986°W; summit elev. 1303 m

All times are local (unless otherwise noted)


Seismicity declines with no eruption after two earthquake swarms

Intense seismicity was felt by Akutan residents beginning on the evening of 10 March and through the next day (BGVN 21:02). Students in Akutan (13 km E of the summit; figure 1) carefully counted the frequency and intensity of the earthquakes during the day on 11 March. The resulting information was the first quantitative dataset about the earthquakes and suggested that this was an earthquake swarm rather than a classic mainshock-aftershock sequence. The strongest shocks rattled small objects on tables and caused some cabinet doors to open; ground shaking was continuous. The largest of the earthquakes had a magnitude of about 5.1, and there were several of M 4-5, most of them were probably in the M 2.5 to 4 range. There were no operating seismometers on Akutan Island at the onset of seismic unrest; the nearest seismometer was at Sand Point, ~380 km NE. The intense seismic activity began subsiding at about 1700 on 11 March but remained at a level substantially above normal. Seismicity continued through most of that night with many events strongly felt in Akutan. Seismicity declined on 12 March, and late that day a seismologist from the Alaska Volcano Observatory (AVO) who reached Akutan with a seismometer and a portable recording system determined that the earthquakes were volcano-tectonic.

Figure (see Caption) Figure 1. Terrain-corrected synthetic aperture radar (SAR) image showing Akutan and Makushin volcanoes in the Aleutian Islands, Alaska. Courtesy of the Alaska SAR Facility; data copyright European Space Agency.

At about 1700 on 13 March, felt-earthquakes began occurring at a rate of greater than 1/minute, a higher rate than on 11 March. Damage associated with these earthquakes included objects tumbling off shelves, and ground shaking was again continuous. The strongest of these events were felt as far away as Dutch Harbor/Unalaska 50 km SW of Akutan. The number of earthquakes recorded in Akutan was over 800/day during the intense earthquake swarm on 13-14 March. A slight decrease in the rate of activity occurred at about 0500 on 14 March, but felt earthquakes still occurred every 2-3 minutes. There were a few earthquakes with M >= 5, and more between 4 and 5. This swarm began subsiding about 18 hours after onset. Because of the continued high seismicity AVO initiated use of a Level of Concern Color Code system and designated the current level to be Orange on 14 March, indicating an eruption was possible at any time within the next few days. On the night of 14 March, AVO's seismologist in Akutan reported 4-5 felt events.

On 15 March the rate and intensity of recorded earthquakes, although much lower than earlier in the week, remained well above background. At about 1700, a geologist flying into Akutan glimpsed a part of the N flank and summit area through broken clouds, but observed no evidence of eruptive activity. AVO scientists in Akutan felt only a few earthquakes that night. The number of earthquakes recorded on 16 March was much lower than during the swarms of 11 and 13 March. However, the rate and intensity of earthquake activity remained well above background. The weather continued to be poor, hampering visual observations. The number of daily earthquakes remained about the same through 19 March. Scientists in Akutan reported feeling only a few earthquakes each of those nights.

The Level of Concern Color Code was downgraded to Yellow on 20 March based on decreasing seismicity over the previous six days to 60-80 events/day. The Yellow code indicates that the threat of imminent eruption has declined, and the possibility that the volcano will return to quiet over a period of weeks without eruption has increased. An airline passenger reported seeing the snow-filled summit crater, with very slight normal wisps of steam from the central cinder cone, and no evidence of eruptive activity. The level of seismicity remained above background, and several earthquakes each day were felt in Akutan.

By 22 March a total of five seismic stations in four locations had been installed and all data were being sent to the Fairbanks and Anchorage laboratories in real time. Maximum separation of the stations was ~9 km. Four of the stations were located around Akutan Harbor, and the fifth was on the E slopes of the volcano about midway between the village of Akutan and the summit. The seismic array will remain in its present geometry until additional stations can be placed by helicopter this summer. By 24 March all AVO personnel had left, and around-the-clock monitoring using the new seismic stations was being conducted from AVO.

The number of earthquakes continued during 21-25 March at a rate of ~60-80/day, decreased slightly by 27 March to ~40-60/day, and remained at that level through 29 March. As of 5 April seismicity continued to slowly diminish. Earthquakes were distributed widely beneath the E half of the island with a cluster, shallower than 10 km, located ~8-10 km due E of the summit cinder cone and ~5 km W of the village of Akutan. The rate of seismicity during 6-12 April was about half that of the previous week, with ~10-20 earthquakes/day, most too small to be felt by local residents. Seismicity decreased again by half during 13-19 April, to ~5-10 small earthquakes/day.

Geologic Background. One of the most active volcanoes of the Aleutian arc, Akutan contains 2-km-wide caldera with an active intracaldera cone. An older, largely buried caldera was formed during the late Pleistocene or early Holocene. Two volcanic centers are located on the NW flank. Lava Peak is of Pleistocene age, and a cinder cone lower on the flank produced a lava flow in 1852 that extended the shoreline of the island and forms Lava Point. The 60-365 m deep younger caldera was formed during a major explosive eruption about 1600 years ago and contains at least three lakes. The currently active large cinder cone in the NE part of the caldera has been the source of frequent explosive eruptions with occasional lava effusion that blankets the caldera floor. A lava flow in 1978 traveled through a narrow breach in the north caldera rim almost to the coast. Fumaroles occur at the base of the caldera cinder cone, and hot springs are located NE of the caldera at the head of Hot Springs Bay valley and along the shores of Hot Springs Bay.

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


Arenal (Costa Rica) — March 1996 Citation iconCite this Report

Arenal

Costa Rica

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

All times are local (unless otherwise noted)


Continued eruptions and recently updated map of lava flows

During February and March, Crater C continued to emit gas, lava, and sporadic Strombolian eruptions. For both months, OVSICORI-UNA reported that the intensity of explosive activity was slightly below that of January, however, columns still rose ~1 km. Prevailing winds blew towards the NW, W, and SW. Arenal continued to cause acidic rains and to eject volcanic bombs, blocks, and ash. The volcano's steep slopes and receding vegetation have led to gullying in unconsolidated material and cold avalanches down local drainages.

ICE reported the distribution of lava flows down Arenal's W slopes (figure 76). A flow active from May 1995 through early January 1996 ceased and a new one trending WNW began in late January, its downslope end reaching 1,200-m elevation in early March. Also, on the N flank in early March, some rolling blocks destroyed forest down to 1,150 m elevation. Deposits reminiscent of those from pyroclastic flows were found in late December at 950 m elevation.

Figure (see Caption) Figure 76. Sketch map of Arenal area showing distribution of lavas as of March 1996. Courtesy of G. J. Soto.

ICE noted that December explosions were ~15-30 minutes apart; after mid-January the explosions were ~27 ± 21 minutes apart (1 sigma standard deviation); steam often vented in the N quadrant of Crater C. Nightime observers saw cyclic changes in the intensity of crater glow repeating every 39 ± 22 seconds; the changes were attributed to convection in the intra-crater lava pool. ICE also repeatedly measured ash deposition rates adjacent to the crater (table 13).

Table 13. Mass of Arenal's ash collected at a site 1.8 km W of the active vent. Courtesy of ICE.

Collection Interval Avg daily ashfall (grams/m2) Ash % 300+µ Ash % less than 300µ
24 Aug-26 Sep 1995 20.7 36 64
26 Sep-23 Oct 1995 1.1 0 100
23 Oct-22 Dec 1995 24.2 56 44
22 Dec-06 Mar 1996 32.9 50 50

OVSICORI-UNA reported the respective values of tremor duration and local seismicity during February and March: 386 and 261 hours and 758 and 624 events. Events of frequency below 3.5 Hz typically accompanied those eruptions that ejected pyroclastics.

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

Information Contacts: Erick Fernández, Elicer Duarte, Vilma Barboza, Rodolfo Van der Laat, and Enrique Hernandez, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica; Gerardo J. Soto, Oficina de Sismolog¡a y Vulcanolog¡a, Departamento de Geolog¡a, Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica.


Avachinsky (Russia) — March 1996 Citation iconCite this Report

Avachinsky

Russia

53.256°N, 158.836°E; summit elev. 2717 m

All times are local (unless otherwise noted)


Increased seismicity and a higher steam plume

On 7 March the Institute of Volcanic Geology and Geochemistry (IVGG) reported a noteworthy increase in seismicity beneath Avachinsky and an increase in the height of the steam plume to ~100 m above the volcano. The steam plume suggested a possible increase in heat flux. The IVGG reported that the possibility of an eruption within the next few weeks to months has increased significantly. Elevated seismicity was previously reported in late 1993 and early 1994 (BGVN 19:01).

Geologic Background. Avachinsky, one of Kamchatka's most active volcanoes, rises above Petropavlovsk, Kamchatka's largest city. It began to form during the middle or late Pleistocene, and is flanked to the SE by the parasitic volcano Kozelsky, which has a large crater breached to the NE. A large horseshoe-shaped caldera, breached to the SW, was created when a major debris avalanche about 30,000-40,000 years ago buried an area of about 500 km2 to the south underlying the city of Petropavlovsk. Reconstruction of the volcano took place in two stages, the first of which began about 18,000 years before present (BP), and the second 7000 years BP. Most eruptive products have been explosive, with pyroclastic flows and hot lahars being directed primarily to the SW by the breached caldera, although relatively short lava flows have been emitted. The frequent historical eruptions have been similar in style and magnitude to previous Holocene eruptions.

Information Contacts: Tom Miller, Alaska Volcano Observatory (URL: https://www.avo.alaska.edu/); Vladimir Kirianov, Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk-Kamchatsky, 683006, Russia.


Etna (Italy) — March 1996 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Intermittent ash emissions and Strombolian activity from two summit craters

Adverse weather conditions that prevented observation of the summit in late February (BGVN 21:02) continued throughout March. Ash puffs from Bocca Nuova crater (BN) were seen during some clear periods on 1 and 5 March, and on the morning of 6 March several black ash emissions were observed. Between 1200 and 1300 a sequence of ash puffs was produced from Northeast Crater (NEC). At 1530, another dense black ash puff was emitted from BN. At sunset the snow mantle was discontinuously covered by a thin ash layer. Ash emissions were again observed during some clearings on 7 March.

On 11 March around 2300 a one-hour long increase in tremor amplitude was recorded at the summit stations. During the afternoon of 12 March the weather improved and after sunset pulsating red glows were observed above NEC by the surveillance camera. Glow produced by the Strombolian activity after 1730 was almost continuous until changing to pulses at 1840 and disappearing at 2100. At the climax, red tracks of volcanic bombs were recognizable up to 150 m above the crater rim. The eruptive episode was marked by increased seismic tremor amplitude similar to that of the previous night.

On the morning of 14 March weather conditions became worse and the video link was interrupted. The video link was restored on 21 March and some minor ash emissions were observed. The observations by the video camera remained intermittent due to the poor weather. Around 2000 on 30 March a remarkable increase in low-frequency events and explosion earthquakes was recorded at all stations of the seismic network; poor weather prevented visual confirmation. The phenomena continued until 2100 on 31 March and during the daytime strong pulsing steam emissions, sometimes with ash, were observed at NEC and BN.

Strombolian activity that began the day after the eighth fire fountaining episode (9-10 February) continued in April, building several nested spatter and scoria cones on the NEC floor; these rose as high as the crater rim.

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: Mauro Coltelli, CNR Istituto Internazionale di Vulcanologia (IIV), Piazza Roma 2, Catania, Italy (URL: http://www.ingv.it/en/).


Fukutoku-Oka-no-Ba (Japan) — March 1996 Citation iconCite this Report

Fukutoku-Oka-no-Ba

Japan

24.285°N, 141.481°E; summit elev. -29 m

All times are local (unless otherwise noted)


Emission of colored water and long discolored aqueous plumes

Aviators from the Japan Marine Safety Agency (JMSA) began observing yellowish-green discoloration of seawater during 25-28 November 1995 (BGVN 20:11/12). Similar discoloration was seen on 12, 22, and 23 January 1996 (BGVN 21:01), and also on 26 January, as reported by the Japan Meteorological Agency.

Information from the Volcano Research Center revealed that JMSA observers once again noted yellowish brown discolored seawater in the area on 4 April. According to the reports, the colored area expanded like a belt up to ~3 km long. Strong emission of colored water was recognized from two points. Although white-colored suspension was observed on the surface, floating pumices were not recognized. Yellowish-green to yellowish-brown water observed on 12 April formed a plume ~4 km long and 200 m wide, including 3-4 spots from which colored-water was gushing out intermittently. No pumices were recognized.

Geologic Background. Fukutoku-Oka-no-ba is a submarine volcano located 5 km NE of the pyramidal island of Minami-Ioto. Water discoloration is frequently observed from the volcano, and several ephemeral islands have formed in the 20th century. The first of these formed Shin-Ioto ("New Sulfur Island") in 1904, and the most recent island was formed in 1986. The volcano is part of an elongated edifice with two major topographic highs trending NNW-SSE, and is a trachyandesitic volcano geochemically similar to Ioto.

Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan; Volcano Research Center, Earthquake Research Institute, University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html); Hydrographic Department, Maritime Safety Agency, 3-1 Tsukiji, 5-Chome, Chuo-ku, Tokyo 104, Japan.


Hokkaido-Komagatake (Japan) — March 1996 Citation iconCite this Report

Hokkaido-Komagatake

Japan

42.063°N, 140.677°E; summit elev. 1131 m

All times are local (unless otherwise noted)


Additional information about the 5 March eruption

Volcanic tremor was registered for six minutes starting at 1810 on 5 March by the JMA station 4.1 km WSW of the crater. During this activity, two main vents opened on and near the S side of Showa 4-nen (1929) crater. A line of vents extending ~200 m N-S formed on the S part of the crater floor. Strong eruptive activity was observed until 7 March and then decreased. Volcanic earthquakes had increased somewhat prior to the eruption, but seismicity remained low afterwards through mid-April.

Geologic Background. Much of the truncated Hokkaido-Komagatake andesitic volcano on the Oshima Peninsula of southern Hokkaido is Pleistocene in age. The sharp-topped summit lies at the western side of a large breached crater that formed as a result of edifice collapse in 1640 CE. Hummocky debris avalanche material occurs at the base of the volcano on three sides. Two late-Pleistocene and two Holocene Plinian eruptions occurred prior to the first historical eruption in 1640, which began a period of more frequent explosive activity. The 1640 eruption, one of the largest in Japan during historical time, deposited ash as far away as central Honshu and produced a debris avalanche that reached the sea. The resulting tsunami caused 700 fatalities. Three Plinian eruptions have occurred since 1640; in 1694, 1856, and 1929.

Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.


Irazu (Costa Rica) — March 1996 Citation iconCite this Report

Irazu

Costa Rica

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

All times are local (unless otherwise noted)


Infrequent microseisms in February and March

During March, the dark-blue lake dropped 30 cm with respect to December 1995. Constant bubbling continued along the N, NW, W, and SE shores. The NW-flank site of the December 1994 eruption continued to emit low volumes of gas. During February and March seismic station IRZ2, 5 km SW of the crater, registered 31 and 19 microseisms, respectively. These events were only detected locally. Significant tilt was not detected over the deformation network.

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

Information Contacts: Erick Fernández, Elicer Duarte, Vilma Barboza, Rodolfo Van der Laat, and Enrique Hernandez, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica; Gerardo J. Soto, Oficina de Sismología y Vulcanología, Departamento de Geología, Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica.


Iwatesan (Japan) — March 1996 Citation iconCite this Report

Iwatesan

Japan

39.853°N, 141.001°E; summit elev. 2038 m

All times are local (unless otherwise noted)


Volcanic tremor registered again on 4 March

Small-amplitude volcanic tremor was detected on 4 March. Tremor was last registered on three days in January 1996 (BGVN 21:02) and once in October 1995.

Geologic Background. Viewed from the east, Iwatesan volcano has a symmetrical profile that invites comparison with Fuji, but on the west an older cone is visible containing an oval-shaped, 1.8 x 3 km caldera. After the growth of Nishi-Iwate volcano beginning about 700,000 years ago, activity migrated eastward to form Higashi-Iwate volcano. Iwate has collapsed seven times during the past 230,000 years, most recently between 739 and 1615 CE. The dominantly basaltic summit cone of Higashi-Iwate volcano, Yakushidake, is truncated by a 500-m-wide crater. It rises well above and buries the eastern rim of the caldera, which is breached by a narrow gorge on the NW. A central cone containing a 500-m-wide crater partially filled by a lake is located in the center of the oval-shaped caldera. A young lava flow from Yakushidake descended into the caldera, and a fresh-looking lava flow from the 1732 eruption traveled down the NE flank.

Information Contacts: Japan Meteorological Agency (JMA), Volcanological Division, Seismological and Volcanological Department, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.


Karymsky (Russia) — March 1996 Citation iconCite this Report

Karymsky

Russia

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

All times are local (unless otherwise noted)


More details about the early January eruptions

According to the Institute of Volcanology (IV), the eruption on 2 January began around 0800. This activity was preceded by an upsurge in seismicity that started in April 1995. At 1926 on 31 December 1995, a M 5.8 earthquake occurred in the Kronotsky gulf, 50-60 km NE of the volcano. On 1 January at 2057 an earthquake of M 5.2 in the Karymsky region was followed at 2157 by a M 6.9 event centered ~25 km S of the volcano. During the next day there were more than 10 aftershocks of M >= 5.0. On 2 January at 1540, a group of IV volcanologists arrived by helicopter. Eruptive centers were observed near the summit and 5-6 km S in Karymsky Lake (maximum depth 115 m), which fills the Akademii Nauk caldera.

The eruption began with formation of a vent with a diameter of 20-30 m, located 50 m below the summit. Violent emissions of ash-rich gas jets rose to 1 km from another vent on the SW slope. Steam-and-gas jets, occasionally with black-colored matter, were also ejected to several hundred meters from beneath the surface of Karymsky Lake. The presumed eruptive center was 100-200 m from the shore in the NW sector of the lake. Turbulent steam-and-gas plumes rose 5-6 km above the surface from a 200-m-diameter area. Ice covering the lake had completely melted.

On 3 January the near-summit vent increased in size to 50 m in diameter. Gas and steam blasts alternated with ash ejections from the two simultaneously active vents on the volcano. Ash was usually ejected from the upper vent, and a white-colored plume was emitted from the lower vent. Ash ejections lasted 2-3 minutes, and gas blasts lasted 1.5-2 minutes. An ash-and-gas column rose 1-1.2 km and was blown E and SE by the wind. The surface of Karymsky Lake steamed intensely, sending clouds 800-1,000 m above the lake. Areas of green water were visible through breaks in the clouds, and a newly-formed black beach was seen. In the N and NE sector of the lake a narrow spit, beginning from the source of the Karymsky river and extending 250-300 m to the center of the lake, had formed. The water level in the lake had dropped a few meters. The upper reaches of the river had dried up, but on 2 January waves from the submarine eruption (up to 10 m high or more) overflowed the N shore, flooding a wide valley 1.5 km below the source. During a surveillance flight on 4 January, large areas of the valley were covered by black mud. The beach contained three fumarolic vents along the NE-trending fault zone. Within a radius of 500-800 m of the source of the Karymsky River, the surrounding snow-covered hills contained thousands of holes with diameters ranging from 10 cm to 1.5-2 m formed by lithic blocks ejected from the lake. The water level of the lake continued to fall because of intense evaporation.

Light-gray dacitic ash covered an area of about 150-200 km2. At a distance of 8 km from the volcano fractions ranging from 0.16 to 0.06 mm dominated. Estimates made by S.A. Fedotov indicated that on 2 and 3 January the ash ejection rate from the summit crater reached 3-4 tons/second.

Routine observations from 2 January through 11 February showed that the climactic phase of the subaqueous eruption continued for no more than 12-15 hours. That eruption consisted of frequent explosions during which a vapor-gas mixture with lithic material was ejected to the surface. In the N sector of the lake at the shore W of the Karymsky River, damaged trees provided evidence of two eruptive sources 500-600 m from each other. This zone contained the main concentration of bomb material ejected from the lake. A portion of the shoreline (150-200 m long and 5-15 m wide) E of the river sank several meters into the lake. The main eruption center was 500 m from the shore, but smaller peripheral centers were also observed. As a result of the eruption, in the NNW sector of the lake, a beach in the form of a wide 0.4 km2 cape was produced, as well as a narrow spit extending SE from the old shore. The length of the new shoreline was 2.4 km, and a large shoal was observed around the new peninsula. According to the preliminary estimates, the ejected deposits in the lake are at least 1 km2 in area and 5-10 x 106 m3 in volume.

Thermal springs that discharge at the S shore of Karymsky Lake were destroyed by ejecta from this eruption, and several new mud pots were formed; chemical composition of the solutions was unchanged. Near the center of the new beach, composed of sand-gravel and bomb material, a chain of five explosive vents with diameters from 1.5 to 30 m was observed. At the N end was a thermal site with a diameter of ~50 m that exhibited intense vapor emission and was covered by sublimates; visiting scientists detected a hydrogen sulfide odor. A dry funnel with a diameter of ~3 m and high gas emission at a temperature of 97°C was in the center of this site. Other explosion funnels had water at a depth of 1.2-1.5 m with temperatures from 33 to 70°C. The three funnels closest to the lake and on the opposite shore had gas emissions with temperatures of 97-98°C.

On 4 January run-off from the lake ceased owing to damming by ejected material. Analyses of water samples from the lake, river, and various hot springs in the area indicated that there had been chemical contributions to the lake water by an underlying magma body.

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

Information Contacts: G.A. Karpov, Ya.D. Muravyev, R.A. Shuvalov, S.M. Fazlullin, and V.N. Chebrov, Institute of Volcanology, Far East Division, Russian Academy of Sciences, Petropavlovsk-Kamchatsky, 683006, Russia.


Kilauea (United States) — March 1996 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Heightened activity on 1-4 February followed by 10-day pause; bench construction

Unusually heightened activity along Kilauea's East Rift zone on 1-4 February was followed by a pause that began on 4 February and ended at midnight on 14 February (BGVN 21:01). Tilt in the N-S direction increased roughly 3-fold; in the E-W direction, roughly 4-fold. Daily counts of shallow, summit SPC earthquake counts rose from around 10/day to 580/day.

During the 14-day pause, lava continued circulating inside the lava pond at Pu`u `O`o cone but no lava was seen flowing in downstream tubes. The lava pond rose to 60-70 m below the rim as the eruption restarted and lava re-entered the tubes around mid-day on 14 February.

Lava subsequently broke out of the tubes to reach the surface at numerous locations (including those at 750-, 720-, 700-, 450-, and 90-m elevations and on the coastal flats). About 31 hours later lava reached the ocean via the old tube system. Despite these numerous sites where lava had been escaping from tubes on 14-15 February, in the days following lava generally ceased reaching the surface and feeding lava flows. Lava did emerge at elevations of 60 to 100 m and on the coastal plain between Kamokuna and Kamoamoa (figure 99). The surface of the lava pond dropped by 19-21 February, possibly reaching 90 m below the rim. Still, on 23 February aa emerged at 270 m elevation. The same day, 23 February, explosive activity at the Kamokuna bench built a new littoral cone.

Figure (see Caption) Figure 99. New land and active entries in the Kamokuna area, March 1996. Index map shows the swath of 1992-96 lava flows. Courtesy of HVO.

As late as 9 March, flows confined to the area below Pulama Pali and the coast covered much of the S half of the Kamoamoa flow field but failed to reach either adjacent grasslands or the sea. During the early hours of 29 February the entire lower coastal bench, a roughly 30 x 100 m area, fell into the ocean. The event was recorded seismically at an instrument 10 km distant. Since then, freshly erupted lava began constructing a new coastal bench.

During the second half of February through early March, low-amplitude tremor in the East Rift continued; during 13-26 February and 12-25 March tremor amplitudes were ~3x background but showed fluctuations. During the February interval microearthquake counts were low beneath the summit and rift zones. Shallow, long-period microearthquake counts were high on 4-5 March and briefly again on 8 March. On 2, 5, 7, and 8 March there were four events > M 3.0 in the 7-33 km range. Deep tremor from the usual SW source was recorded in three episodes during 14-15 March: a total of 90 minutes on 14 March and 108 minutes on 15 March. Counts of shallow, long-period earthquakes increased during 19-23 March reaching a maximum daily total of 1,750.

On 24 March, 2 hours of elevated tremor (4-5x background) took place without accompanying shallow short-period earthquakes. That same day, the summit inflated rapidly for an hour and then deflated for several hours. The rate of inflation was similar to that of 1 February but the summit acquired only 3 µrads of tilt compared with the 15 µrads seen on 1 February. As the summit deflated on the afternoon of 24 March, the eruption site on the East Rift zone probably received a small magma surge resulting in moderate-sized breakouts in the early afternoon. The breakouts, which originated from the lava tube at the 820-, 750-, and near the 600-m elevations, produced small pahoehoe flows that were mostly stagnant by the next morning. On the night of the 24th, bright glow from Pu`u `O`o indicated turbulence in the lava pond. Except for these flows on 24 March, surface lavas mainly appeared below the base of Pulama Pali.

At the coast, spectacular explosions, some as high as 70 m, began on 19 March. Though diminishing thereafter, they persisted until at least 6 days. Observers saw lava bubble-bursts, lava fountains, and steam jets. These explosions built up five new littoral cones ~130 m W of the earlier Kamokuna entries inside the National Park (figure 99).

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

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii National Park, HI 96718, USA.


Kuchinoerabujima (Japan) — March 1996 Citation iconCite this Report

Kuchinoerabujima

Japan

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

All times are local (unless otherwise noted)


Increasing number of earthquakes since January

According to the Sakura-jima Volcanological Observatory of Kyoto University, the number of earthquakes has increased around Shin-dake since January. The total number of earthquakes recorded was 32 in January, 40 in February, and 77 in March.

A group of young stratovolcanoes forms the E end of Kuchinoerabu-jima Island, midway between Suwanose-jima and Kyushu. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater of Shin-dake and have suffered damage from historical eruptions. Shin-dake is the summit cone, and has been the site of all 13 eruptions known since 1840. The last eruption was a weak 30-minute explosion on 28 September 1980 that sent an ash plume 2-3 km high.

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), Volcanological Division, Seismological and Volcanological Department, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.


Kujusan (Japan) — March 1996 Citation iconCite this Report

Kujusan

Japan

33.086°N, 131.249°E; summit elev. 1791 m

All times are local (unless otherwise noted)


Increased seismicity in late March, but plume remains ash-free

Seismicity increased during 24-27 March, and volcanic tremors were detected late in the month. The total number of earthquakes in March was 507. The height of the ash-free plume remained at 100-300 m for most of the month, with increases to 600 m on 12 and 27 March.

Geologic Background. Kujusan is a complex of stratovolcanoes and lava domes lying NE of Aso caldera in north-central Kyushu. The group consists of 16 andesitic lava domes, five andesitic stratovolcanoes, and one basaltic cone. Activity dates back about 150,000 years. Six major andesitic-to-dacitic tephra deposits, many associated with the growth of lava domes, have been recorded during the Holocene. Eruptive activity has migrated systematically eastward during the past 5000 years. The latest magmatic activity occurred about 1600 years ago, when Kurodake lava dome at the E end of the complex was formed. The first reports of historical eruptions were in the 17th and 18th centuries, when phreatic or hydrothermal activity occurred. There are also many hot springs and hydrothermal fields. A fumarole on Hosho lava dome was the site of a sulfur mine for at least 500 years. Two geothermal power plants are in operation at Kuju.

Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.


Langila (Papua New Guinea) — March 1996 Citation iconCite this Report

Langila

Papua New Guinea

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

All times are local (unless otherwise noted)


Vulcanian explosions continue

Moderate explosive activity continued at Crater 2 during March, however, there was possibly a slight decline compared to last September. Intermittent Vulcanian explosions released ash clouds that rose several hundred meters above the crater. These explosions resulted in minor ashfalls to the volcano's SE. A weak but steady crater-glow was observed on a few nights. In accord with these observations, 6-30 daily explosion earthquakes registered at a station 4 km away. There was no visible activity from Crater 3.

Geologic Background. Langila, one of the most active volcanoes of New Britain, consists of a group of four small overlapping composite basaltic-andesitic cones on the lower eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater is breached widely to the SE; Langila volcano was constructed NE of the breached crater of Talawe. An extensive lava field reaches the coast on the north and NE sides of Langila. Frequent mild-to-moderate explosive eruptions, sometimes accompanied by lava flows, have been recorded since the 19th century from three active craters at the summit of Langila. The youngest and smallest crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Information Contacts: Ben Talai, RVO.


Manam (Papua New Guinea) — March 1996 Citation iconCite this Report

Manam

Papua New Guinea

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

All times are local (unless otherwise noted)


Inaudible, weak-to-moderate steaming from two craters

When visible, South and Main Craters only gave off weak to moderate white vapor. There were no audible sounds from either crater and no sighting of glow at night. Seismic monitoring at Manam was absent during March. Measurements from the water tube tiltmeters at Tabele Observatory (4 km SW of the summit) indicated no deflation to slight deflation.

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

Information Contacts: Ben Talai, RVO.


Oshima-Oshima (Japan) — March 1996 Citation iconCite this Report

Oshima-Oshima

Japan

41.51°N, 139.367°E; summit elev. 732 m

All times are local (unless otherwise noted)


Earthquakes and tremor detected

Volcanic earthquakes and tremors were detected near the end of March by instruments maintained by Hokkaido University.

This small island 55 km W of Hokkaido in the Japan Sea consists of two coalescing volcanoes. An eruption in August 1741 produced heavy ashfall on the Hokkaido mainland. A violent explosion and landsliding from the Nishi-yama cone accompanied a large tectonic earthquake and a major tsunami that killed 1,475 people, most on the W coast of the Oshima Peninsula. Subsequent eruptions through early 1742 produced a new central cone and lava flows. Minor explosive activity was documented in 1759, 1786, and 1790.

Geologic Background. Oshima-Oshima, a small, 4-km-wide Japan Sea island 55 km west of the SW tip of Hokkaido, is the emergent summit of two coalescing basaltic-to-andesitic stratovolcanoes. Higashiyama, at the east end of the island, is cut by a 2-km-wide caldera covered on its west side by Nishiyama volcano. The western cone failed during an eruption in 1741, creating a large horseshoe-shaped caldera breached to the north that extends from the summit down to the sea floor at the base of the volcano and producing a mostly submarine debris avalanche that traveled 16 km. A tsunami associated with the collapse swept the coasts of Hokkaido, western Honshu, and Korea, and caused nearly 1500 fatalities. The 1741 eruption, the largest in historical time at Oshima-Oshima, concluded with the construction of a basaltic pyroclastic cone at the head of the breached caldera. No eruptions have occurred since the late-18th century.

Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.


Pinatubo (Philippines) — March 1996 Citation iconCite this Report

Pinatubo

Philippines

15.13°N, 120.35°E; summit elev. 1486 m

All times are local (unless otherwise noted)


Rainfall during October-November 1995 typhoons generates floods and lahars

Intense and prolonged rainfall, associated with the passage of two typhoons on 1 October and 3 November 1995, triggered lahars and floods along the Pasig-Potrero River.

On 1 October 1995, Typhoon Mameng delivered 337 mm of rain on the Sacobia pyroclastic fan triggering five distinct and fairly continuous lahar episodes over a 14-hour period. The largest episode had an estimated peak discharge of 400 m3/sec at Mancatian, Porac. Within each episode were discrete peak readings that could be generated by several causes: variations in rainfall intensity and duration, bank caving, repeated damming and breaching along channel constrictions, as well as any combination of these. Flows were described as steaming at observation point Delta 5 (15.5 km from Pinatubo), but progressive dilution through the incorporation of older materials cooled the flows to ambient temperature by the time they reached Bacolor.

The Typhoon Mameng deposit can be distinguished from earlier lahar deposits by the abundance of pebble to boulder-size clasts rip-ups of older, pre-1991, eruption materials scoured from the channel. The Mameng deposit was provisionally classified in two distinct debris flow units: a gray pumiceous, pebbly sand unit (A), and a brown, lithic-rich, coarse gravel unit (B). Unit A occurs as small overbank deposits at Mancatian, and as laterally extensive coalescing lobes from San Antonio, Bacolor down to the Gapan-San Fernando-Ologampo (GSO) road. Its occurrence as an overbank facies at Mancatian suggests that this unit correlates to the above mentioned peak flow episode. Unit B corresponds to subsequent flows and waning episodes: it occurred as in-channel, gravel terrace deposits from Delta 5 observation point downstream to the GSO road, and from thereon as an overbank facies where it overlaid unit A.

A total area of 25 km2 was buried beneath 0.5 to 6 m thick of sediment. An estimated sediment volume of 50 x 106 was deposited during these events, with roughly 40% consisting of either old, pre-1991 eruption deposits or post-1991 eruption lahar materials.

On 3 November 1995, 150 mm of rain fell on Mount Pinatubo with the passage of Typhoon Rosing. Lahars observed at Delta 5 watch point were relatively cold hyperconcentrated flows, based on the absence of steaming. Estimated peak discharge was about 120 m3/sec. Based on flow sensor data from the Pasig-Potrero river, the peak flow was channel-confined down to the GSO road and lasted ~2.6 hours. It eroded ~30 m of the left bank along the Porac-Angels Road. Sediments were mostly clayey remobilized Mameng deposits.

Former flows had already filled the stretch of the channel at a point 2 km upstream of the GSO road down to the S portion of Bacolor. When the peak flow reached the channel-filling stage, it caused flows to bifurcate and incise a new channel (figure 34) ~50 m W of the typhoon Mameng channel. Average in-channel deposition was 2 m thick; average overflow deposition, ~0.3-m thick. Overflow units were observed along the banks of the previous channel along the GSO road and leveled to a recently emplaced steel bridge. Flows reached farther downstream causing flooding and siltation near Mesalipit and Tinajeros. The other channel backflowed following considerable aggradation along the GSO road. The new channel delivered muddy flows that induced flooding and siltation in the W portion of San Fernando, particularly in the Barangays of St. Nino and St. Lucia.

Figure (see Caption) Figure 34. Map of the 1991-95 lahars at Pinatubo. Courtesy of PHIVOLCS.

Lahars have occurred during every rainy season since the eruption of 15 June 1991. Pinatubo's last reported lahars were triggered by the heavy rainfalls of July 1995, when 30 x 106 m3 of debris, deposited over a 12 km2 area, forced mass evacuation of Porac and Bacalor (BGVN 20:07).

Geologic Background. Prior to 1991 Pinatubo volcano was a relatively unknown, heavily forested lava dome complex located 100 km NW of Manila with no records of historical eruptions. The 1991 eruption, one of the world's largest of the 20th century, ejected massive amounts of tephra and produced voluminous pyroclastic flows, forming a small, 2.5-km-wide summit caldera whose floor is now covered by a lake. Caldera formation lowered the height of the summit by more than 300 m. Although the eruption caused hundreds of fatalities and major damage with severe social and economic impact, successful monitoring efforts greatly reduced the number of fatalities. Widespread lahars that redistributed products of the 1991 eruption have continued to cause severe disruption. Previous major eruptive periods, interrupted by lengthy quiescent periods, have produced pyroclastic flows and lahars that were even more extensive than in 1991.

Information Contacts: Raymundo S. Punongbayan, director, Philippine Institute of Volcanology and Seismology (PHIVOLCS), Department of Science and Technology, (DOST), 5th & 6th Floors Hizon Building, 29 Quezon Avenue, Quezon City, Philippines.


Poas (Costa Rica) — March 1996 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Seismicity decreased roughly 10-fold since October 1995

During a February visit, the temperature of the turquoise-green crater lake was 26°C and its surface had risen 2 m with respect to its January level. Except that this lake-level rise had covered some active fumaroles, their behavior was similar to previous months. Fumaroles on the SE, S, and SW sides of the crater had temperatures of 93-95°C. One fumarole along the lake's W shore had migrated upward along a crack.

When visited during March, the lake appeared sky blue in color, its surface had dropped by 0.5 m compared to the previous month, and the water temperature was 30°C. Fumaroles, their gas emission rates, and temperatures were similar to previous months. A distance survey across the crater found that a 21 ppm/year expansion had occurred since mid-1995. At a spot adjacent to the lake, the survey found an 18 mm contraction since October 1995.

The pyroclastic cone, the major source of gas emission, discharged plumes 200-400 m high. Where accessible the temperatures of the emitted gases were around 94°C; gas emissions sounded like releases from a pressure valve, particularly those venting along the inaccessible N wall.

February and March seismicity consisted of a total 1,100 and 983 events, respectively, the majority being low frequency. This was a roughly 10-fold decrease since a peak in October 1995. Tremor duration was <10 hours, down from over 250 hours in November and December 1995.

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

Information Contacts: Erick Fernández, Elicer Duarte, Vilma Barboza, Rodolfo Van der Laat, and Enrique Hernandez, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA); Gerardo J. Soto, Oficina de Sismología y Vulcanología, Departamento de Geología, Instituto Costarricense de Electricidad (ICE).


Popocatepetl (Mexico) — March 1996 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Continued ash emissions; new lava dome and lava flows in summit crater

A new eruption began early on 5 March with continuous tremor followed by small ash emissions (BGVN 21:02). Low-level ash emissions continued through 11 March with some larger events on 10 and 11 March. Those episodes generated plumes that extended SW over the Pacific Ocean.

After 11 March and through the 19th, the overall level of activity appeared to have reached a steady state. Fumarolic activity alternated with 4-6 short-duration ash emissions each day from the same vents as the 1994-95 episode. These emissions formed short-lived ash columns that were carried away by the wind. Light ashfalls were reported from several towns around the volcano, particularly to the E and S. Seismicity, as low-level tremor accompanied by minor A- and B-type volcanic earthquakes, also showed almost stationary patterns and energy release rates. No deformation was detected by the 3-tiltmeter network on the N flank.

Satellite imagery during this interval revealed intermittent plumes extending E at altitudes around 6-7 km. Late on 13 March the plume was visible as far as 340 km ESE of the summit at 5-7 km altitude; ashfall was reported in Puebla, 70 km E. Large plumes of very thin dispersed ash blowing E over the Gulf of Mexico were observed through 15 March, with denser plumes closer to the volcano. During 15-19 March, when observed on satellite imagery, plumes averaged ~20 km wide and 60 km long before they dissipated; altitudes were in the 5-7 km range.

Ash emission increased between 2000 on 19 March and 0300 on 20 March, when characteristic signals of eight emission events or 'puffs' were detected by the seismic monitoring network. Afterwards, the emission-event rate returned to the previous range of 4-6 events/day. This, combined with stronger winds towards the E, produced light ashfalls on towns in that direction. The 'puff' events were detected on top of a moderate level of volcanic seismicity, consisting of A- and B-type events and low-level tremor, as well as strong signals from Pacific-coast tectonic earthquakes unrelated to the volcanic activity.

On 21 March the ash emission rate remained stable. The next day, the puffs' frequency increased to ~9/day, but their size decreased. Average height of the ash plumes was ~500 m above the summit, and duration <5 minutes. This activity continued without significant changes until 25 March, when the rate of ash emissions reached 8 puffs between 1030 and 1230 before returning to a rate of 8-10/day. This condition prevailed until 28 March, when another increase in the level of activity was detected similar to that on 25 March. The ash puffs were easily recognized in the seismograms as 30-40 seconds of tremor followed by an impulsive signal, similar to seismic events in the 1994-95 episode. Although the release of seismic energy increased after 25 March, the levels never reached high values, and remained well below the energy level of 5 March. Seismicity decreased again in late March.

Plumes after 20 March continued to be visible on satellite imagery, and were interpreted based on wind data to generally have been below 7 km altitude, with some slightly higher. However, poor weather and low levels of activity limited the number of plumes identified. Aviation notices from Mexico City and observers at the Puebla airport through 4 April continued to report ash at low levels, usually within ~20-30 km of the summit, blowing in easterly directions.

On 29 March during a COSPEC flight, Lucio Cardenas, Juan Jose Ramirez, and Hugo Delgado observed a new lava dome with an area of 400 m2 on the E side of the crater floor along the rim of the inner crater (a lava dome destroyed during the 1920-27 eruption). This new lava dome was observed coming from a source outside that inner crater but flowing into the it. Another helicopter flight later that day confirmed that block-lava was flowing from a vent located between the vents opened on December 1994 and the 1919 craterlet near the center of the crater. This lava slowly flowed towards the craterlet. When the dome was checked again on 1 April lava had filled most of the inner crater (nearly 60 m deep) and increased its area to nearly 600 m2. Assuming that the lava started to flow towards the craterlet on 25 March, and that it had been almost filled by 1 April, a rough estimate of the lava extrusion rate is 5,000-6,000 m3/day.

The formation of this craterlet was described in detail by Dr. Atl, the painter-volcanologist who later studied the Parícutin eruption in detail. According to him, the bottom of the volcano crater was almost flat before 1919. That year, extruded lava formed a small dome ~35 m high and 60-70 m diameter in the base. That dome collapsed in 1923 forming the craterlet. The volume of the internal cone of the craterlet is estimated to be 40,000 m3.

A series of SO2 flux measurements was begun after January 1994 (BGVN 19:11 and 19:12). During 1995 measurements rose to nearly 8,000 metric tons/day (t/d) in March, but gradually decreased to 2,000 t/d in June. A persistent decrease in gas emissions starting in July reduced the SO2 flux to nearly 100 t/d by December 1995. During the 5 March 1996 event, renewed ash emissions coincided with SO2 fluxes of up to 15,000 t/d; by late March it was decreasing, but emission levels remained high (>5,000 t/d). Currently, the COSPEC measurements are carried out by the Instituto de Geofisica (National University of Mexico), sponsored by the Secretaria de Gobernacion (Ministry of the Interior) through CENAPRED (Disaster Prevention National Center) using an instrument borrowed from the University of Colima and a plane owned by the Mexican Navy.

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: Servando De la Cruz-Reyna (CENAPRED and Instituto de Geofisica, UNAM); Roberto Quaas Weppen, Enrique Guevara Ortiz, Bertha López Najera, and Alicia Martinez Bringas, Centro Nacional de Prevencion de Desastres (CENAPRED), México D.F., México; Hugo Delgado Granados, Instituto de Geofisica, UNAM, Circuito Cientifico C.U., 04510 Mexico D.F., México; Jim Lynch, NOAA Synoptic Analysis Branch.


Rabaul (Papua New Guinea) — March 1996 Citation iconCite this Report

Rabaul

Papua New Guinea

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

All times are local (unless otherwise noted)


December-March ash deposits now 10-cm thick; seismicity continues

During March the intra-caldera cone Tavurvur produced ash explosions at 2-5 minute intervals; these rose to ~400-1,500 m altitude and then generally drifted SE. As a result, over the last 4 months ~10 cm of ash accumulated on the abandoned village of Talwat (2 km SE of Tavurvur). Vulcan only produced weak fumarolic emissions.

Seismicity fluctuated slightly during March, remaining at a level slightly lower than the peak reached in mid-February. Low-frequency earthquakes, events associated with Tavurvur ash emissions, took place 100-250 times/day (a total of 4,708 times during March). There were also five brief intervals where non-harmonic tremor took place. Only six high-frequency earthquakes occurred; some were kilometers outside the caldera to the NE in the area most seismically active since the 1994 eruption.

No significant ground deformation affected the caldera during the month. Overall, during the recent eruptive phase, the only observed ground deformation has been a slight (20 µrad) deflation at the tiltmeters nearest to Tavurvur.

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

Information Contacts: Ben Talai, Rabaul Volcano Observatory, P.O. Box 386, Rabaul, Papua New Guinea.


Rincon de la Vieja (Costa Rica) — March 1996 Citation iconCite this Report

Rincon de la Vieja

Costa Rica

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

All times are local (unless otherwise noted)


Mild seismicity continues in February

Several small-to-moderate eruptions took place in early November 1995 (BGVN 20:10 and 20:11/12). Mild seismicity continued after the eruption; during February seismic station RIN3, located 5 km SW of the active crater, registered seven microseisms (six low-frequency, one high-frequency). These microseisms were only detected locally.

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

Information Contacts: Erick Fernández, Elicer Duarte, Vilma Barboza, Rodolfo Van der Laat, and Enrique Hernandez, Observatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica; Gerardo J. Soto, Oficina de Sismolog¡a y Vulcanolog¡a, Departamento de Geolog¡a, Instituto Costarricense de Electricidad (ICE), Apartado 10032-1000, San José, Costa Rica.


Sangay (Ecuador) — March 1996 Citation iconCite this Report

Sangay

Ecuador

2.005°S, 78.341°W; summit elev. 5286 m

All times are local (unless otherwise noted)


Phreatic explosions, blue gas plumes, crater glow, and dome rockfalls

From 24 November to 12 December 1995, the first detailed study of Sangay volcano (figures 1 and 2) was carried out by an Instituto Geofísico/ORSTOM team (Escuela Politécnica Nacional, Quito), with helicopter support from the Ecuadorian Army and the assistance of five local guides from Alao. During this time, activity was characterized by continuous fumarolic steaming, frequent phreatic explosions, occasional crater glow, and dome rockfalls. Previous reports from August 1976, August 1983, and June-August 1988 (SEAN 01:10, 08:07, and 13:08) identified four summit vents aligned WSW-ENE, which are here numbered from 1 to 4 going from W to E.

Figure (see Caption) Figure 1. Present cone of Sangay in December 1995 viewed from the base camp 4.3 km SW. The recent pyroclastic-flow deposit on which the campsite is located is in the foreground, among the badlands corresponding to an older edifice. At the summit can be seen the W lava dome (Vent 1) and its now inactive lava tongues. Photo by M. Monzier, courtesy of ORSTOM.
Figure (see Caption) Figure 2. View of the Sangay summit in December 1995 looking NE from the base camp showing the lava dome and associated lava flows from Vent 1. Behind this dome, a steam plume rises from the main crater (Vent 3). Photo by M. Monzier, courtesy of ORSTOM.

In 1976, Vent 1 consisted of a fracture from which lava was slowly issuing, but by August 1983 it had built a lava dome. This small dome was apparently more active in August 1988, and sent a lava flow 400 m down the W flank, where it split into two lobes. In late 1995 this dome was possibly still growing, and was the source of some fumarolic activity and many rockfalls, making the W and SW slopes of the cone dangerous to cross. Apparently there have been no new lava flows from this vent since August 1988. Vent 2, a small 15-m-diameter crater immediately ENE of Vent 1 has frequently been the site of explosive activity (1976 and 1983), but apparently was less active in 1988 and was quiet during the 1995 visit. The ENE crater (Vent 4) remained inactive but with occasional fumarolic activity.

Vent 3, at 80-100 m across, is the largest and deepest crater. In 1976 and 1983 only fumarolic activity was observed from this crater, but lava was reported in 1988. During the 1995 visit it was the site of frequent phreatic explosions, some separated by hours, others coming as often as every 26 minutes. Several explosions were followed by a rhythmic, pulsating roar that lasted for up to 50 oscillations. White vapor plumes, ejected with the audible explosions, rose several hundred meters above the summit. Light blue gas plumes and occasional red glow at night immediately above this crater implied the presence of lava. Frequent rockfalls from the upper S flank of the cone suggested that some lava may be escaping, breaking off, and rolling down the S slopes.

During the visit a portable MEQ-800 Sprengnether seismograph with a vertical, 1-Hz L4C geophone was operated at the La Playa base camp, 4.3 km SW of the main crater at 3,600 m elevation. A preliminary study of the smoked-paper seismograms showed three types of seismic signals, frequently associated with observed explosions in the crater (figures 3 and 4): tremor, long-period, and hybrid events. Tremor events had a monochromatic signature with a period of 1 second and lasted < 60 seconds. The long-period events had emergent arrivals and a constant period of ~0.7 seconds; they were often associated with observed explosions. Hybrid events began with a long-period event (0.7 seconds) and were followed by a signal similar to that of the tremor (1 second). Some hybrid events were associated with audible and observed explosions followed by a roar like pulsating, rhythmic exhalations. No local high-frequency events were detected.

Figure (see Caption) Figure 3. Types of volcanic earthquakes at Sangay recorded by the seismic station 4.3 km SW in December 1995. Courtesy of ORSTOM.
Figure (see Caption) Figure 4. Volcanic seismicity recorded at Sangay, 26 November-10 December 1995. Courtesy of ORSTOM.

Recent lavas and pyroclastic-flow, debris-flow, and lahar deposits are ubiquitous around the cone and testify to Sangay's nearly continuous activity. The site of the La Playa camp (figure 5) is on an andesitic pyroclastic-flow deposit containing bombs up to 4 m in diameter which was emplaced between 1956 and 1965. An accident with two fatalities happened in August 1976 (SEAN 01:10). A previously unreported accident occurred in December 1993 when the main crater exploded just as two mountaineers looked over its rim. Both were blinded by the heat and fragment impacts and remained lost in the jungle on the cone's lower slopes until rescued three days later.

Figure (see Caption) Figure 5. Preliminary geological/structural map of Sangay volcano based on fieldwork, aerial photographs, and 1:50,000 topographic maps from the Instituto Geografico Militar, Quito. Key: M = metamorphic formations; I, II, III = successive volcanic edifices; C1 and C2 = avalanche calderas; AD = avalanche deposits. Campsites are shown as black dots (La Playa = basecamp, Z = Zumbacocha and D = Duende are secondary camps).

In addition to the present cone (Sangay III), two previous edifices were identified and sampled, both of which had been destroyed by collapse. The remnant calderas are found on the E side of the present cone and are breached E toward the Amazon plain. Their probable avalanche deposits lie at the E foot of the cone. A preliminary geologic map of Sangay (figure 5) shows the three successive edifices and the two associated calderas. Edifice I is mainly built of lava, whereas edifices II and III contain both lava and pyroclastic deposits. The products of edifices I and II appear to be more varied in composition (greater differentiation) than those of Sangay III, where mafic andesites seem to predominate.

This isolated stratovolcano E of the Andean crest is one of Ecuador's most active volcanoes having been in frequent eruption for the past several centuries. The steep-sided glacier-covered volcano towers above the tropical jungle on the E side; on the other sides heavy rains have caused plains of ash to be sculpted into steep-walled canyons up to 600 m deep. The first historical eruption was reported in 1628, and more or less continuous eruptions took place from 1728 until 1916, and again from 1934 to the present.

Geologic Background. The isolated Sangay volcano, located east of the Andean crest, is the southernmost of Ecuador's volcanoes and its most active. The steep-sided, glacier-covered, dominantly andesitic volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the east, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. It towers above the tropical jungle on the east side; on the other sides flat plains of ash have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of a historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The almost constant activity has caused frequent changes to the morphology of the summit crater complex.

Information Contacts: M. Monzier and C. Robin, ORSTOM, A.P. 17-11-6596, Quito, Ecuador; M. Hall, P. Mothes, and P. Samaniego, Instituto Geofísico, Escuela Politécnica Nacional, A.P. 17-01-2759, Quito, Ecuador.


Socorro (Mexico) — March 1996 Citation iconCite this Report

Socorro

Mexico

18.78°N, 110.95°W; summit elev. 1050 m

All times are local (unless otherwise noted)


Slight temperature increases at most summit fumaroles and hot springs

Logistical support from the Méxican Navy enabled researchers to measure seven fumarole and hot spring temperatures on 2 February 1995 in the summit region of Socorro Island's Mount Everman. Previous measurements, taken on 5-12 February 1993, were made at the same sites. These sites, labeled A-G, are shown on sketch maps and tables in Siebe and others (1995) and BGVN 18:01. In this most recent series of measurements, all temperatures were 90°C, except site D, which was 74°C. The 1993 measurements were made in conjunction with a local submarine eruption that also produced T-wave signals. These new measurements showed a several-degree increase over many of those in 1993.

The 1993 eruption was seen at the ocean surface over the island's submarine W flanks; during this visit further signs of eruption were absent from the ocean's surface and from distant hydrophones. Unfortunately, local hydrophones on the S end of the island were not operational. Several hundred meters N of the summit, on North Dome, the visitors saw recently killed vegetation and dead trees on the margins of some hydrothermally active pits. They also noted soft warm ground, dead bracken, and newly established pits, suggesting reactivation. In other cases green trees grew in the pit walls. While the majority of the fumaroles appeared similar to those in 1993, the observers noted three 'mud volcanoes'; two were active and the third issued deep rumblings. A stream in the vicinity of the summit and North Dome had a temperature of 60°C and numerous 80°C springs were seen both along its bed and nearby.

Reference. Siebe, C., Komorowski, J-C., Navarro, C., McHone, J., Delgado, H., and Cortes, A., 1995, Submarine eruption near Socorro Island, Mexico: Geochemistry and scanning electron microscope studies of floating scoria and reticulite: Journal of Volcanology and Geothermal Research, v. 68, p. 239-71.

Geologic Background. Socorro, the SE-most of the Revillagigedo Islands south of Baja California, is the summit of a massive, predominately submarine basaltic shield volcano capped by a largely buried, 4.5 x 3.8-km-wide summit caldera. A large tephra cone and lava dome complex, Cerro Evermann, forms the summit, and along with other cones and vents, fills much of the Pleistocene caldera. Rhyolitic lava domes have been constructed along flank rifts oriented to the N, W, and SE, and silicic lava flows from summit and flank vents have reached the coast and created an extremely irregular shoreline. Late-stage basaltic eruptions produced cones and flows near the coast. Only minor explosive activity, some of which is of uncertain validity, has occurred from flank vents in historical time dating back to the 19th century. In 1951 a brief phreatic eruption ejected blocks, and the gas column reached 1200 m altitude. A submarine eruption occurred during 1993-94 from a vent 3 km W of the island during which large scoriaceous blocks up to 5 m in size floated to the surface without associated explosive activity.

Information Contacts: Andrew M. Burton, OCEAN, Organizatión para la Conservación Estudio y Análisis de la Naturaleza, A.C., 22 de Diciembre No. 1, Col. Manuel Avila Camancho, Naucalpan, Edo. de México.


Soufriere Hills (United Kingdom) — March 1996 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Escalating dome growth spawns pyroclastic flows and another evacuation

During March ash plumes continued to blow over the Capital and environs, and the rate of dome extrusion escalated. Later, on 3 April, explosions at the dome and pyroclastic flows down the Tar River prompted an evacuation of the southern part of the island.

Seismicity during March from both rockfalls and deeper sources continued in a manner consistent with dome growth. Tremor was repeatedly recorded at Gages station. Although there were exceptions, deformation mainly continued as a shortening of line lengths equivalent to ~1 mm/day (similar to trends seen since mid-November). The chief exception was on the W flank (Amersham to Chances Steps line), which on March 11 showed a surprising 3 cm lengthening since last measured on February 19. This is a reversal of the shortening that occurred from October to late December on this line.

Numerous rockfalls and avalanches from the dome in early March chiefly appeared on the dome's SW and NW sides. Next, they were repeatedly seen on the NW but some also started in the dome's central area (week 2). Rockfalls then shifted from the dome's NW margin to the E margin (week 3). Later rockfalls descended the NW, W, and E margins (week 4).

Rapidly growing spines continued to be common during much of March. They were noted on the dome's SW (weeks 1 and 2) and NW (week 4). On the NW, one spine achieved the greatest absolute height of any yet seen. It extruded rapidly, rising 10 m over an interval of about one day on 26-27 March. Over a 24-hour interval beginning at 1600 on 21 March, another spine's vertical growth measured ~7 m.

The dome's topography was mapped during week 2 from Farrell's lookout (on the WNW). The resulting map allowed workers to estimate the dome's mid-March volume as ~6.7 x 106 m3, a value comparable to previous, cruder estimates made in the field. It appeared that the dome's growth rate increased 7- to 10-fold in the last few months. Specifically, the late-November and December rate was ~0.2-0.3 m3/second whereas the March rate was closer to 2 m3/sec. On 3 and 12 March the growing dome's summit elevations were 845 and 875 m, a 30 m rise in ~9 days. Later, on 20 March, a visit to Gages Wall revealed that, even though this sector had few rockfalls around the time of the visit, the dome's talus apron had grown to within ~15 m of the wall's top.

During week 2, fine ash carried from some larger rock falls was deposited on the upper W flanks. On 17 March, viewers on Farrell's lookout were enveloped in a warm ash cloud following a rockfall that occurred without a noticeable explosive component. That same day an explosion may have helped drive an ash column to 2,300 m.

Other relatively large ash clouds appeared repeatedly during late March and early April. On 27 March there were ash clouds generated at 0642, 0700, 0848, and 1725. The 0642 event produced an ash column that reached a height of 2,000-2,300 m and blew W blanketing areas in vicinity of the Capital. The 0642 event accompanied a seismic signal comprised of seven pulses in a 14-minute interval; the 0700 event generated a smaller ash column accompanied by three seismic pulses. Except for these intervals of unusual seismicity and frequent signals from large rockfalls, seismicity during the 24-hour interval prior to the 27 March events had been generally quiet. Helicopter observations shortly after the 0700 event disclosed that ash had been channeled to the E down a drainage called the Hot River Ghaut. Hot ash had traveled for ~1 km from the dome, igniting dead trees along its path. Observers witnessed the 0848 event, but it was much smaller and areally restricted.

Several other plumes on 31 March led to a nearly one-hour interval late that day when unusually intense seismicity registered at all the stations. The seismicity was correlated with ash plumes that blew W. On 1 April a helicopter flight confirmed the largest block-and-ash flows yet seen. Although runout distances were similar to those seen on 27 March (on the order of 1 km from the base of the Castle Peak dome), those on 1 April entrained bigger blocks and had a more widely dispersed dilute component that burned a broader swath of trees and foliage around the Tar River Soufriere (~1 km NE of Castle Peak's summit).

Until a small explosive event at 0652 on 3 April, the majority of the airborne ash was thought to have come from rockfalls and avalanches off the dome. This explosion, and several other significant ones the same day, discharged from a fissure on the dome's E flank, a spot that also appeared as the source of recent rockfalls. At various times on 3 April, continuous ash emissions came from the crater area. The activity continued to build during the day, with many small explosive seismic signals and continuous tremor recorded at the closest seismic station on Chances Peak.

At 1518, a pyroclastic flow occurred in the Tar River area. It traveled ~1.9 km down this drainage and burned vegetation and set fire to sulfur at the Tar River Soufriere. It also extended 1.9 km down the Hot River Valley (to where the road crosses the river), stopping ~400 m upslope of the Tar River Estate house. Although no inhabited areas were affected by the pyroclastic flow, the settlement of Long Ground lies ~2 km NE of Castle Peak's summit. The flow generated an ash plume that rose to ~6,700 m. Much of the ash blew N in light and variable winds. Other pyroclastic flows occurred at 1808 and 1818. These events, some of which were captured on NASA GOES satellite images, prompted scientists to note the possibility of further explosive eruptions during the next few days and to urge residents to move to the island's N end. The 3 April evacuation continued through at least 30 April.

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

Information Contacts: Montserrat Volcano Observatory (MVO), c/o Chief Minister's Office, PO Box 292, Plymouth, Montserrat (URL: http://www.mvo.ms/); NOAA/NESDIS Synoptic Analysis Branch (SAB), Room 401, 5200 Auth Road, Camp Springs, MD 20746, USA.


Suwanosejima (Japan) — March 1996 Citation iconCite this Report

Suwanosejima

Japan

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

All times are local (unless otherwise noted)


Weak ash eruptions in early March cause ashfalls

Weak ash eruptions were observed on 5 and 6 March; occasional ashfalls were reported on the island. Nine explosions were observed in 1995 and there were small eruptions during 10-13 January (BGVN 21:01). Activity has been high since 1950.

Geologic Background. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.

Information Contacts: Volcanological Division, Seismological and Volcanological Department, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100 Japan.


Ulawun (Papua New Guinea) — March 1996 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


Still emitting low to moderate amounts of steam

As in previous months, during March Ulawun emitted weak to moderate volumes of white vapor. The seismograph did not operate.

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

Information Contacts: Ben Talai, RVO.


Unzendake (Japan) — March 1996 Citation iconCite this Report

Unzendake

Japan

32.761°N, 130.299°E; summit elev. 1483 m

All times are local (unless otherwise noted)


Tremor associated with minor tilt changes

Volcanic tremor on 24 March was associated with minor tiltmeter changes. A pyroclastic flow on 10 February (BGVN 21:02) was the first in a year. Dome growth followed by collapses that generated pyroclastic flows was a common occurrence during the 1990-95 eruption.

Geologic Background. The massive Unzendake volcanic complex comprises much of the Shimabara Peninsula east of the city of Nagasaki. An E-W graben, 30-40 km long, extends across the peninsula. Three large stratovolcanoes with complex structures, Kinugasa on the north, Fugen-dake at the east-center, and Kusenbu on the south, form topographic highs on the broad peninsula. Fugendake and Mayuyama volcanoes in the east-central portion of the andesitic-to-dacitic volcanic complex have been active during the Holocene. The Mayuyama lava dome complex, located along the eastern coast west of Shimabara City, formed about 4000 years ago and was the source of a devastating 1792 CE debris avalanche and tsunami. Historical eruptive activity has been restricted to the summit and flanks of Fugendake. The latest activity during 1990-95 formed a lava dome at the summit, accompanied by pyroclastic flows that caused fatalities and damaged populated areas near Shimabara City.

Information Contacts: Japan Meteorological Agency (JMA), Volcanological Division, Seismological and Volcanological Department, 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.

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