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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 23, Number 02 (February 1998)

Managing Editor: Richard Wunderman

Aira (Japan)

Several explosions during January-February

Axial Seamount (Undersea Features)

Hydrothermal plumes detected on research cruise suggest lava extrusion

Bezymianny (Russia)

Fumarolic plumes present on most days

Cameroon (Cameroon)

1997 seismicity remains low with one earthquake swarm

Fournaise, Piton de la (France)

First eruption in over 5 years begins 9 March

Heard (Australia)

No evidence of recent activity in March

Huila, Nevado del (Colombia)

Significant increase in seismicity in December 1997

Karymsky (Russia)

Ongoing gas-and-ash explosions

Kilauea (United States)

Steady, low activity during February

Klyuchevskoy (Russia)

Earthquakes, tremor, and gas-and-steam plumes throughout February

Langila (Papua New Guinea)

Intermittent eruptive activity at Crater 2

Manam (Papua New Guinea)

Low-level vapor emission and nighttime summit-crater glow in February

McDonald Islands (Australia)

The eruption of 1996-97 and its inferred lavas and tephra

Popocatepetl (Mexico)

Cyclical dome extrusions that by late 1997 filled one-third of crater capacity

Rabaul (Papua New Guinea)

January activity presages February eruption

Sheveluch (Russia)

Frequent gas-and-steam plumes

Soufriere Hills (United Kingdom)

Dome growth continues; discussion of the 26 December dome collapse



Aira (Japan) — February 1998 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Several explosions during January-February

Sakura-jima produced frequent explosions in December 1997-January 1998 (BGVN 23:01). A 20 January volcanic ash advisory reported an eruption at 1227. An 8 February advisory reported an eruption at 0420; the volcanic ash cloud reached ~2.1 km altitude and drifted SE. A notice later in the day reported another eruption at 0508 with an ash cloud at ~2.1 km altitude extending SE. A 16 February advisory reported an eruption on 15 February that sent a plume to the E at ~18 km altitude. Observers in Kagoshima Airport saw a volcanic ash cloud to the SE and S at 0600 on 16 February. Satellite images did not show a plume due to the presence of low weather clouds. A 24 February ash advisory noted an eruption at 0705; volcanic ash extended E at ~18 km altitude.

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: Sakurajima Volcanological Observatory (SVO), Disaster Prevention Research Institute (DPRI), Kyoto University, Sakurajima, Kagoshima, 891-14, Japan; Volcanological Division, Japan Meteorological Agency (JMA), 1-3-4 Ote-machi, Chiyoda-ku, Tokyo 100, Japan.


Axial Seamount (Undersea Features) — February 1998 Citation iconCite this Report

Axial Seamount

Undersea Features

45.95°N, 130°W; summit elev. -1410 m

All times are local (unless otherwise noted)


Hydrothermal plumes detected on research cruise suggest lava extrusion

An episode of intense seismicity occurred at Axial Seamount during 25 January-early February (see map, BGVN 23:01). In response, a team of scientists sailed aboard Oregon State University's research vessel Wecoma during 9-16 February. The following report summarizes the preliminary findings of the Axial Response Team (ART). Although the team found evidence of extensive new venting at Axial Volcano, vigorous event plumes were absent.

Despite wind gusts and high seas, the team deployed 8 ocean bottom hydrophones on 10 February around the intersection of Axial's S rift zone and summit caldera. In addition, the team made measurements of water conductivity, temperature, depth, and light attenuation at 16 sites (figure 4). The light- attenuation measurements were used to estimate particle loading in the hydrothermal plumes.

Figure (see Caption) Figure 4. Deployment of a water-sampling instrument package during the ART cruise. Ron Greene of Oregon State University is on the right. Courtesy of R. Embley.

Some instruments had been previously deployed and were in place on the sea floor before and during the event, including two volcanic system monitors and an array of three temperature sensor/current-meter moorings along the rectangular caldera's SE corner at the center of the summit epicenter locations. Earlier pre-event data on plume distribution and chemistry were gathered during a research cruise in the summer of 1997, a time when very weak plumes were present close to the sea floor.

Hydrothermal discharge from Axial seamount's summit was roughly an order of magnitude greater than before the eruption. The caldera's S end was filled with plumes that had temperature anomalies approaching 0.2°C and intense light-attenuation coefficients (~0.2/m); these plumes rose at least 200 m above the ocean bottom. The temperature anomalies were about twice as great as those seen after the 1993 CoAxial eruption (BGVN18:07). The plume was tracked ~20 km SW, where it remained as strong as in the caldera. The areal pattern of integrated relative light-attenuation (figure 5) indicated that the plume drifted steadily SW, in agreement with past current-meter readings. Both methane and hydrogen gas concentrations were higher during the cruise than in previous measurements, reaching concentrations as high as 600 nM and 200 nM, respectively. Background concentrations for methane are typically <1 nM.

Figure (see Caption) Figure 5. Plan view showing contours of relative light-attenuation that has been integrated over depths of 1.1-1.5 km. Dots indicate water sampling stations; the heavy line indicates the transect shown in figure 6. Increased suspended particles cause greater light-attenuation. Courtesy of NOAA/PMEL.

Vertical profiles gathered at the water sampling stations revealed hydrothermal signal maxima occurring at shallow (1.2-1.4 km) and/or deep (1.4-1.5 km) locations. A very strong plume at the S end of the caldera at a depth of ~1.4-1.5 km was detected on 12 February. The plume's peak (~1.47 km depth) had a light- attenuation coefficient >0.440/m, a value significantly greater and found at shallower water depths than previously detected over Axial Caldera. Increased mass concentration of particles suspended in the water column causes greater light-attenuation values. Water samples collected from the plume had very high levels of methane (~600 nM); hydrogen gas concentration measured ~4 nM. The profile taken over the vent field (at station 6) revealed a very strong plume with considerable vertical structure that extended ~1.2 km to the sea floor. The plume showed light attenuation (figure 6) and temperature anomalies with maxima occurring at both 1375- and 1425-m depth.

No event plumes were detected directly above the caldera. The team may have arrived after any event plumes had drifted away from the site. The few wispy plumes ~50-80 m thick found almost 600 m above the caldera were possible event plume remnants. No sign of venting was detected along the length of the S rift zone; a dike intrusion was thought to have occurred there during the seismic swarm of late January 1998. The lack of plumes differed from the 1993 CoAxial eruption, where the intrusion was associated with long plumes.

A small but distinct hydrothermal signal at 1.2-1.3 km depth was detected on 15 February ~18 km S of the caldera, within the central seismic cluster. The signal was interpreted as a plume remnant. Water sampling revealed methane concentrations of 5-20 nM but no elevated H2 concentrations. This indicated either that the original hydrothermal source was low in H2 or that the H2 had been lost to microbial oxidation.

A NE-SW transect of relative light attenuation (figure 6) suggested that the plume thickened and shallowed downstream from the caldera. The changes in intensity along the transect may have arisen from one or more causes, including fluctuations in water speed, temporal changes in the intensity of venting, and initial venting of more buoyant fluids.

Figure (see Caption) Figure 6. Cross-section showing relative light attenuation in and adjacent to Axial's caldera. Water-sampling sites (eg., 10, 11, etc.) are labeled along the top axis. The line of the cross section appears on figure 5. Courtesy of NOAA/PMEL.

Particles in water samples from stations 11 and 1 (figure 5) were studied by scanning electron microscope (SEM). Samples from station 11 contained many angular glass shards up to 95 micrometers in diameter. Many of the shards had precipitated halite particles attached to them; precipitation of halite coatings on altered glass surfaces was consistent with heating seawater to >400°C at 1.5 km depth. Similar coatings were found on basaltic particles from the 1993 CoAxial eruption.

Many small particles with high iron concentrations were also observed. Although these particles were of similar size to iron oxides from past eruptive sites, their shapes were more angular than the typically rounded, globular shapes seen in the past. Chemical analysis showed that these particles also contained halides and a higher than usual ratio of phosphorus to iron. Analysis of particles from station 1 showed abundant elemental sulfur. These observations were taken to suggest a lava eruption on the SE caldera floor.

Axial Volcano rises 700 m above the mean level of the ridge crest and is the most magmatically robust and seismically active site on the Juan de Fuca Ridge between the Blanco Fracture Zone and the Cobb offset. The summit is marked by an unusual rectangular-shaped caldera (3 x 8 km, figure 5) that lies between the two rift zones. The caldera is defined on three sides by a boundary fault of up to 150 m relief. Organisms have colonized the hydrothermal vents near the caldera faults and the rift zones. Following the initial discovery of venting N of the caldera in 1983, a concentrated mapping and sampling effort was made in the mid-late 1980s.

Geologic Background. Axial Seamount rises 700 m above the mean level of the central Juan de Fuca Ridge crest about 480 km W of Cannon Beach, Oregon, to within about 1400 m of the sea surface. It is the most magmatically robust and seismically active site on the Juan de Fuca Ridge between the Blanco Fracture Zone and the Cobb offset. The summit is marked by an unusual rectangular-shaped caldera (3 x 8 km) that lies between two rift zones and is estimated to have formed about 31,000 years ago. The caldera is breached to the SE and is defined on three sides by boundary faults of up to 150 m relief. Hydrothermal vents with biological communities are located near the caldera fault and along the rift zones. Hydrothermal venting was discovered north of the caldera in 1983. Detailed mapping and sampling efforts have identified more than 50 lava flows emplaced since about 410 CE (Clague et al., 2013). Eruptions producing fissure-fed lava flows that buried previously installed seafloor instrumentation were detected seismically and geodetically in 1998 and 2011, and confirmed shortly after each eruption during submersible dives.

Information Contacts: Jim Cowen, Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawai'i at Manoa, 1000 Pope Road, Honolulu, HI USA 96822; Ed Baker, NOAA Pacific Marine Environmental Laboratory (PMEL), 7600 Sand Point Way N.E., Seattle, WA USA 98115; Bob Embley, NOAA Pacific Marine Environmental Laboratory (PMEL), 2115 SE OSU Drive, Newport, OR 97365 USA (URL: http://www.pmel.noaa.gov/).


Bezymianny (Russia) — February 1998 Citation iconCite this Report

Bezymianny

Russia

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

All times are local (unless otherwise noted)


Fumarolic plumes present on most days

Fumarolic plumes rose 50-800 m above the volcano on 27 January, 3-5, 9, 12-14, 17-18, 20-22, 23-25, and 28 February. A steam plume rose 50 m on 30 January. Plumes on 17-18, 23-25, and 28 February traveled SE. No seismicity registered under the volcano during 23 February-1 March.

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

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


Cameroon (Cameroon) — February 1998 Citation iconCite this Report

Cameroon

Cameroon

4.203°N, 9.17°E; summit elev. 4095 m

All times are local (unless otherwise noted)


1997 seismicity remains low with one earthquake swarm

Local seismicity in the Mt. Cameroon region has remained consistently low from 1995 through 1997 at an average of 15 events/month (figure 2). An earthquake swarm recorded in January 1996 consisted of 33 events (modified from BGVN 22:02). Another swarm, of 30 earthquakes, occurred in August 1997. All of the recorded signals were A-type volcanic earthquakes under M 3. Many seismic stations remain out of order and in need of repair, so there is the possibility that other data were lost. However, no events were felt by local residents.

Figure (see Caption) Figure 2. Monthly seismicity in the Mt. Cameroon region, 1993-97. Note that the number of seismic stations functioning varied over the interval shown. Courtesy of IRGM/ARGV.

Geologic Background. Mount Cameroon, one of Africa's largest volcanoes, rises above the coast of west Cameroon. The massive steep-sided volcano of dominantly basaltic-to-trachybasaltic composition forms a volcanic horst constructed above a basement of Precambrian metamorphic rocks covered with Cretaceous to Quaternary sediments. More than 100 small cinder cones, often fissure-controlled parallel to the long axis of the 1400 km3 edifice, occur on the flanks and surrounding lowlands. A large satellitic peak, Etinde (also known as Little Cameroon), is located on the S flank near the coast. Historical activity was first observed in the 5th century BCE by the Carthaginian navigator Hannon. During historical time, moderate explosive and effusive eruptions have occurred from both summit and flank vents. A 1922 SW-flank eruption produced a lava flow that reached the Atlantic coast, and a lava flow from a 1999 south-flank eruption stopped only 200 m from the sea. Explosive activity from two vents on the upper SE flank was reported in May 2000.

Information Contacts: Ateba Bekoa and Ntepe Nfomou, IRGM Antenne de Recherches Geophysiques et Volcanologiques (ARGV), P.O. Box 370, Buea, Cameroon; G.E. Ekodek and J.M. Nnange, Institut de Recherches Geologiques et Minieres (IRGM), P.O. Box 4110, Yaounde, Cameroon; J.D. Fairhead, Dept. of Earth Sciences, The University of Leeds, Leeds, LS2 9JT, United Kingdom.


Piton de la Fournaise (France) — February 1998 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)


First eruption in over 5 years begins 9 March

Piton de la Fournaise began erupting 9 March at 1500 preceded by a number of earthquakes and strong deformations. The volcano had been quiet since the last fissure eruption on 27 August 1992. The Volcanological Observatory of Piton de la Fournaise (OVPDLF) was able to give authorities two days warning of the impending crisis. Thomas Staudacher, director of OVPDLF, deployed additional seismic and deformation monitoring equipment in the early stages of the event.

Eruptions first started from a fissure at 2,450 m on the N flank of the terminal Dolomieu crater, a spot in the interior of l'Enclos Fouqu' caldera (figure 40). Venting quickly migrated northward to lower altitudes (1,950 m). The activity was focused at two fissures near the very bottom of the slope of Dolomieu and cones were forming at the place where lava fountains were most active.

Figure (see Caption) Figure 40. Sketch map of Piton de la Fournaise and vicinity. Notice that the topographic contour intervals are uneven. Courtesy of OVPDLF.

The lava fountains, some reaching 50 m in height, fed a voluminous flow that progressed N and E towards the Indian Ocean. Lava issued in a sustained flow rate estimated at 20 m3/s; the total volume since the start of the eruption was estimated on 10 March at 7 x 106 m3. The zone where the lava was flowing, to the NE along Osmondes plain in the direction of the sea, is wholly uninhabited. By 10 March activity appeared to be weakening, the front of the flow moving more slowly towards Grandes Pentes. Mist and haze over the Osmondes plain on 11 March prevented observation of the advance of the flow.

Seismicity had increased since the beginning of 1998. Volcanic tremor accompanied venting, including an almost continuous seismic swarm (30 earthquakes per hour in the hours preceding the eruption) beneath the summit's Bory crater in the SW. In the hour before magma venting, inclinometers in the summit area indicated the injection of a dyke and then the opening of a surface fissure. Tremors and swarm were accompanied by intermittent earthquakes, discrete events not usually seen in Piton's past eruptions.

By 1600 on 11 March, cones of scoria had attained heights of 10 m on Piton's upper slopes and 30 m on its lower slopes and were being fed by lava fountains nearly 30 m high. On 12 March at about 0245, a new but much less productive eruptive fissure opened on the opposite (SW) side of the terminal cone at 2,250 m elevation.

A "level one" volcano alert was issued 9 March at 0500 by island prefect Robert Pommies following heavy seismic activity during the weekend. The alert was reduced to "level two" after it was seen that the lava eruption was centered on the N of the volcano. Agence France Presse reported that there was no threat to the village of Sainte-Rose, which had to be evacuated in 1978.

A 14-16 March report stated that eruptive activity at both fissures (N and SW of the central cone) continued uninterrupted through 12 March. Emissions at the N fissures focused on the central vents and built cones ~50 m high. The output rate was ~15-30 m3/s and the lava flow front was stationary (4 km E at ~1,100 m elevation) with a maximum lava temperature of 1,167°C. Also, venting on the SW fissure centered on a limited stretch and built a spatter rampart ~70 m long. The output rate was ~5-10 m3/s with a maximum temperature of ~1,135°C. The latter activity gave rise to a 1.5 km flow. The discrete seismic events that were observed over the continuous tremor had ceased since 12 March but a single event was observed in the night of 13-14 March.

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

Information Contacts: Thomas Staudacher, Director, Observatoire Volcanologique du Piton de la Fournaise (OVPDLF), 14 RN3, le 27Km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.jussieu.fr/); Agence France Presse, Paris, France.


Heard (Australia) — February 1998 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


No evidence of recent activity in March

During 18-21 March geologists sampled Holocene lava flows on Heard Island. On beaches of the N Laurens Peninsula, they found fresh pumice ranging in size up to about 20 x 20 cm . The pumice was concentrated among other storm- transported debris a little distance above the normal surf zone and appeared to have been deposited by wave action. Light creamy green to pale gray in color, the pumice had angular, ovoid or flattened shapes and contained predominantly microphenocrysts and occasional phenocrysts visible to the naked eye. Lithic fragments were not observed.

On Heard Island, Big Ben's summit was usually obscured by clouds. The summit was visible on 20 March, however, and at this time no evidence of recent volcanic activity was observed at Mawson Peak, Big Ben's recently active crater (figure 3). Similarly no plume was seen coming from Heard when McDonald vented steam in early April. In accord with these observations, scientists inferred that the December 1996-January 1997 volcanic activity attributed to Heard actually denoted activity at McDonald.

Figure (see Caption) Figure 3. Map of Heard Island showing principal volcanic centers on both the Laurens and Azorella Peninsulas (see shaded boxes) and on Big Ben (the massif comprising the bulk of the SE part of the island). The beached pumice samples were collected at the N end of the Laurens Peninsula. Courtesy of K. Collerson.

References. LeMasurier, W.E., and Thompson, J.W., primary eds., 1990, Volcanoes of the Antarctic Plate and Southern Oceans, Antarctic Research Series: American Geophysical Union, Washington, D. C. (ISBN 0066-4634).

Collerson, K. D., 1997, Field studies at Heard and McDonald Island in March 1997: unpublished Australian National Antarctic Research Expedition (ANARE) report.

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: Kenneth Collerson, Department of Earth Sciences, University of Queensland, Brisbane, Queensland 4072, Australia; Kevin Kiernan, Department of Geography and Environmental Sciences, University of Newcastle, Newcastle, New South Wales 2300, Australia; Richard Williams, Australian Antarctic Division, Channel Highway, Hobart, Tasmania, Australia; Andrew Tupper, Northern Territory Regional Forecasting Centre, Bureau of Meteorology, P. O. Box 735, Darwin, Northern Territory 0801, Australia.


Nevado del Huila (Colombia) — February 1998 Citation iconCite this Report

Nevado del Huila

Colombia

2.93°N, 76.03°W; summit elev. 5364 m

All times are local (unless otherwise noted)


Significant increase in seismicity in December 1997

The Observatorio Vulcanológico y Sismológico de Popayán (OVSP) reported increased seismicity at the Nevado del Huila volcanic complex. The complex is studied using three seismic stations in SW Colombia. One substantial seismic increase occurred during 20-25 December 1997. About 108 volcano-tectonic earthquakes in three swarms were located in a small area 3 km east of Pico Norte (figure 2). Seismic activity has not previously been known in this area. The swarms were 6-8.5 km in depth (figure 3) with magnitudes ranging from 0.93 to 2.98 (Richter scale).

Figure (see Caption) Figure 2. Epicenter map showing volcano-tectonic seismicity at the Nevado del Huila complex during January to December 1997. Courtesy OVSP.
Figure (see Caption) Figure 3. Depths of volcano-tectonic seismicity at Nevado del Huila during January to December 1997. Courtesy OVSP

A second increase, energy released by volcano-tectonic earthquakes, has grown over the last two years. The period with the largest recorded energy was associated with the swarms of late December 1997, which totaled 1.20 x 108 ergs (figure 4).

Figure (see Caption) Figure 4. Seismic energy from volcano-tectonic and long-period (LP) earthquakes recorded at stations monitoring Nevado del Huila, 1993-1998. Courtesy OVSP.

The Nevado del Huila volcanic complex is comprised of three main peaks aligned N-S; these are named Pico Norte, Pico Central and Pico Sur. Pico Central is the highest summit in the Cordillera Central, is composed of interbedded tephra and steep-sided lava flows located inside an old caldera. The sole known eruption recorded in historical time was an explosion in the 16th century. Two persistent steam columns rise from the southern peak and hot springs surround the volcano. The volcano has 13.4 km2 of glacial cover.

Geologic Background. Nevado del Huila, the highest peak in the Colombian Andes, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. The high point of the complex is Pico Central. Two glacier-free lava domes lie at the southern end of the volcanic complex. The first historical activity was an explosive eruption in the mid-16th century. Long-term, persistent steam columns had risen from Pico Central prior to the next eruption in 2007, when explosive activity was accompanied by damaging mudflows.

Information Contacts: Fabiola Patricia Rodríguez and Juan Carlos Diago, Observatorio Vulcanológico y Sismológico de Popayán, Calle 5B 2-14, Popayán, Colombia.


Karymsky (Russia) — February 1998 Citation iconCite this Report

Karymsky

Russia

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

All times are local (unless otherwise noted)


Ongoing gas-and-ash explosions

Seismicity remained above background level and low-level Strombolian activity sent ash and steam 300-400 m above the crater during 27 January-1 March. During 27 January-8 February, gas-and-ash explosions occurred every 30-40 minutes. During 9 February-1 March, 70-100 gas-and-ash explosions occurred per day. On 9 February, 11 tectonic earthquakes were recorded ~10 km S of Karymsky.

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


Kilauea (United States) — February 1998 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Steady, low activity during February

During 4 February-5 March, the Pu`u `O`o eruption returned to steady-state activity after a brief magma surge and two seismic swarms in January (BGVN 22:12 and 23:01). Seismicity was low and little inflation or deflation was detected at Kilauea's summit. Magma moved through shallow conduits towards the E rift zone without disturbing the ground surface.

The Pu`u `O`o vent area remained relatively unchanged in appearance during February. Fumes issued from cracks in the cone and surrounding area. Profuse fumes from new cracks near the N rim obscured the views of remote surveillance cameras and observers on helicopter overflights.

Lava continued to travel in tubes from the Pu`u `O`o vents to the ocean; however, during 4-24 February surface lava flows were sparse. Every 4-5 days a small flow issued from the lava tubes across the coastal plain. Most of the surface flows were near the Waha`ula ocean entry. At Kamokuna, lava continued to form a low shelf or bench at the foot of a 10-15 m cliff bordering the ocean. A bench collapse at the Kamokuna coastal entry occurred between 16 and 19 February. The collapse destroyed 4 hectares of land that had formed since the most recent collapse on 15 January (BGVN 22:12). The lava supply to the coastal tube system was interrupted briefly on 21 February, causing the steam plumes at the sea entry to dwindle for most of the day.

Kilauea is one of five coalescing volcanoes that comprise the island of Hawaii. Historically its eruptions originated primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the summit caldera to the sea. This latest Kilauea eruption began in January 1983 along the E rift zone. The eruption's early phases, or episodes, occurred along a portion of the rift zone that extends from Napau Crater on the uprift end to ~8 km E on the downrift end. Activity eventually centered on what was later named Pu`u `O`o. More than 223 hectares of new land have been added to the island and local communities have suffered more than $100 million in damages since the beginning of the eruption.

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 Volcanoes National Park, HI 96718, USA (URL: https://volcanoes.usgs.gov/observatories/hvo/); Ken Rubin and Mike Garcia, Hawaii Center for Volcanology, University of Hawaii, Dept. of Geology & Geophysics, 2525 Correa Rd., Honolulu, HI 96822 USA (URL: http://www.soest.hawaii.edu/GG/hcv.html).


Klyuchevskoy (Russia) — February 1998 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Earthquakes, tremor, and gas-and-steam plumes throughout February

Beginning at 0616 on 28 January and continuing until 1 March, seismicity at Kliuchevskoi was above background level. During 28 January-8 February, earthquakes registered at depths of 25-30 km under the volcano and were accompanied by volcanic tremor. Surface earthquakes accompanied by volcanic tremor were recorded during 9-22 February, and deep earthquakes were detected during 23 February-1 March.

Fumarolic plumes rose 1-3 km above the volcano on 27 January, 3 February, and 17 February. Gas-and-steam plumes rose 50-2000 m on 30 January, 4-5, 9, 11-15, 18-22, 24-28 February, and 1 March. The plumes drifted 1-10 km with prevailing winds.

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

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


Langila (Papua New Guinea) — February 1998 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)


Intermittent eruptive activity at Crater 2

Throughout February, there was intermittent weak eruptive activity at Langila's Crater 2 while Crater 3 remained quiet. On the 3rd, two loud explosions were heard that produced thick dark ash clouds rising 2,500 m above the crater. A similar explosion occurred on 5 February. During 6-14 and 24-26 February, Crater 2 discharged small- to moderate-sized gray ash clouds. Low roaring and rumbling sounds were heard on the 20th, 22nd, and 24th. Crater 3 was restricted to weak fumarolic emissions the entire month. Both seismographs remained inoperative.

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) — February 1998 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)


Low-level vapor emission and nighttime summit-crater glow in February

Activity at both summit craters of Manam was low throughout February. Both craters emitted continuous weak white vapor. Glow was observed at Southern crater on the nights of 3, 5-9, 14-18, and 25-27 February, but there were no sounds.

Seismic activity showed no significant change: 1,100-1,300 low-frequency earthquakes of very low magnitude were recorded daily. Following a deflation of ~1.5 µrad in January, radial tilt as measured at Tabele stabilized for February.

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.


McDonald Islands (Australia) — February 1998 Citation iconCite this Report

McDonald Islands

Australia

53.03°S, 72.6°E; summit elev. 230 m

All times are local (unless otherwise noted)


The eruption of 1996-97 and its inferred lavas and tephra

This report discusses field and geochemical observations that indicates activity at McDonald Island. The activity is inferred to have began in December 1996; it continued through early 1997.

Visual observations. During mid-December 1996, a pilot reported a vapor plume in the vicinity of Heard Island (figure 1). Initially, the report was thought to indicate an eruption of Big Ben, an intermittently active volcano on Heard Island that last erupted in 1993 (BGVN 17:12). Another report discussed a possible volcanic plume near Heard Island on 5 January 1997 (BGVN 22:01). A 15 January 1997 satellite image showed an extensive high-altitude linear cloud formation drifting E from near Heard Island; this activity was also assumed to be associated with Big Ben.

Figure (see Caption) Figure 1. Location of Heard and McDonald Islands on the Kerguelen Plateau in the S Indian Ocean. "SWIR" refers to the Southwest Indian Ridge, "SEIR" to the Southeast Indian Ridge. Gaussberg is an isolated conical mountain of volcanic origin on the coast of Antarctica. Courtesy of K. Collerson.

On 18 March 1997, the "RSV Aurora Australis," a ship en route to Heard Island, sailed within 7.4 km of McDonald Island. Observers on board reported seeing steam plumes emitted at high velocity from several point sources and from the fissure system on the island's steep N face between the topographic features known as The Needle, Samarang Hill, and Macaroni Hill (figure 2). They also saw a low, diffuse, white vapor plume extending SE from the island's N summit. Steam vented from a rubble-covered slope that possibly indicated a lava flow or pyroclastic deposit. Ken Collerson documented these observations on video tape (Collerson, 1997; Collerson and others, 1998).

Figure (see Caption) Figure 2. Sketch map of McDonald Island showing the new lavas in the vicinity of Samarang Hill. Courtesy of K. Collerson.

On 2 April, observers on the vessel "FV Austral Leader" saw vapor rising from the island's summit. The ship came within 2.6-4.6 km of McDonald Island for closer observation and confirmed steam venting similar to that observed on 18 March. Observations included "smoke" clouds rising from the summit and flanks of the N and middle parts of the island, possible lava flows traveling down gullies, and a yellow- green deposit (possibly sulfur) close to the source of the steam emissions. In addition, a diffuse white vapor plume from the N summit of the island was drifting N to NE. An early April photograph of steam venting appears on figure 3.

Figure (see Caption) Figure 3. Photo of McDonald Island taken early April 1997 portraying steam venting at Samarang Hill (in the foreground). In the background resides glacier-draped Heard Island (44 km E of McDonald Island, with a summit elevation of 2,750 m). Copyrighted photo taken by Richard Williams and used with permission of the Australian Antarctic Division.

Although observers never went ashore on McDonald Island during or after the eruption, Collerson estimated the extent of the lavas and fumarolic activity from visual observations, digital video images, and 35 mm photographs. A preliminary sketch map of new lavas appears on figure 2.

During 18-21 March geologists sampled Holocene lava flows on Heard Island. On beaches of the N Laurens Peninsula, they found fresh pumice ranging in size up to about 20 x 20 cm . The pumice was concentrated among other storm- transported debris a little distance above the normal surf zone and appeared to have been deposited by wave action. Light creamy green to pale gray in color, the pumice had angular, ovoid or flattened shapes and contained predominantly microphenocrysts and occasional phenocrysts visible to the naked eye. Lithic fragments were not observed.

On Heard Island, Big Ben's summit was usually obscured by clouds. The summit was visible on 20 March, however, and at this time no evidence of recent volcanic activity was observed at Mawson Peak, Big Ben's recently active crater (figure 4). Similarly no plume was seen coming from Heard when McDonald vented steam in early April (figure 3). In accord with these observations, scientists inferred that the December 1996-January 1997 volcanic activity attributed to Heard actually denoted activity at McDonald.

Figure (see Caption) Figure 4. Map of Heard Island showing principal volcanic centers on both the Laurens and Azorella Peninsulas (see shaded boxes) and on Big Ben (the massif comprising the bulk of the SE part of the island). The beached pumice samples were collected at the N end of the Laurens Peninsula. Courtesy of K. Collerson.

Satellite observations. Satellite images showing plumes similar to volcanic ash clouds extending E from the Heard Island area were reported to Australia's Bureau of Meteorology during the summers of 1996-97. Standard detection techniques did not confirm that the clouds were volcanic; however, several volcanologists and meteorologists studied the plumes and concluded that the clouds were probably not volcanic.

Meteorologists from the Tasmanian and Antarctic office of the Bureau of Meteorology suggested that the plumes were probably banner clouds, a type of cloud that often forms behind mountain peaks at high latitudes.

The ~600-km-long plumes seen repeatedly on the satellite images were not consistent with the prior activity of Heard Island; Heard Island was unlikely to produce large-scale eruptions and high-level ash clouds. However, McDonald Island was not ruled out as a possible source of volcanic plumes.

Geochemical studies. Researchers conducted major element and inductively coupled plasma mass spectrometer trace element analyses on the fresh pumice collected from Heard Island. The pumices were strongly alkaline with elevated incompatible element abundances. Although the results were similar to previous studies of McDonald Island phonolites, the pumices were generally more evolved, suggesting that they were derived from an extremely fractionated magma chamber. This conclusion was also supported by high- precision Th isotopic data. Extreme Na2O values for two samples, coupled with very high volatile contents and carbonatite-like HFSE and LILE abundances, suggested that some of the pumices contained an exsolved sodium- rich carbonate phase.

Sr, Nd, and Pb isotopic compositions of six samples of the fresh pumice collected on Heard Island were within the error of values reported for McDonald Island phonolites. The Sr, Nd, and Pb isotopic data for the pumices differed from other potential young volcanic sources in the southern hemisphere such as South Sandwich Islands, Marion Island, Iles Crozet, and the Ross Sea Igneous Province, and were thus interpreted as derived from McDonald Island.

References. LeMasurier, W.E., and Thompson, J.W., primary eds., 1990, Volcanoes of the Antarctic Plate and Southern Oceans, Antarctic Research Series: American Geophysical Union, Washington, D. C. (ISBN 0066-4634).

Collerson, K. D., Regelous, M., Frankland, R., Wendt, J. I., Kiernan, K., and Wheller, G., 1998, 1997 eruption of McDonald Island (southern Indian Ocean): new trace element and Th-Sr-Pb-Nd isotopic constraints on Heard-McDonald Island magmatism. Abstr. 14th Aust. Geol. Convention, Townsville, July 1998.

Collerson, K. D., Regelous, M., Wendt, J. I., and Wheller, G., 1998, 1997 eruption of McDonald Island (Southern Indian Ocean): new trace element and Th-Sr-Pb-Nd isotopic constraints on Heard-McDonald Island magmatism: Earth Planet Sci. Lett (in prep.)

Collerson, K. D., 1997, Field studies at Heard and McDonald Island in March 1997: unpublished Australian National Antarctic Research Expedition (ANARE) report.

Geologic Background. Historical eruptions have greatly modified the morphology of the McDonald Islands, located on the Kerguelen Plateau about 75 km W of Heard Island. The largest island, McDonald, is composed of a layered phonolitic tuff plateau cut by phonolitic dikes and lava domes. A possible nearby active submarine center was inferred from phonolitic pumice that washed up on Heard Island in 1992. Volcanic plumes were observed in December 1996 and January 1997 from McDonald Island. During March of 1997 the crew of a vessel that sailed near the island noted vigorous steaming from a vent on the N side of the island along with possible pyroclastic deposits and lava flows. A satellite image taken in November 2001 showed the island to have more than doubled in area since previous reported observations in November 2000. The high point of the island group had shifted to the McDonald's N end, which had merged with Flat Island.

Information Contacts: Kenneth Collerson, Department of Earth Sciences, University of Queensland, Brisbane, Queensland 4072, Australia; Kevin Kiernan, Department of Geography and Environmental Sciences, University of Newcastle, Newcastle, New South Wales 2300, Australia; Richard Williams, Australian Antarctic Division, Channel Highway, Hobart, Tasmania, Australia; Andrew Tupper, Northern Territory Regional Forecasting Centre, Bureau of Meteorology, P. O. Box 735, Darwin, Northern Territory 0801, Australia.


Popocatepetl (Mexico) — February 1998 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Cyclical dome extrusions that by late 1997 filled one-third of crater capacity

The following report on Popocatépetl incorporates both background descriptive information, some of which had previously remained unreported, and a more detailed discussion of ongoing dome growth based on aerial photographs and flight observations. The volcano was last discussed in BGVN 23:01. By late 1997 the growing dome occupied 30-38% of the crater's capacity.

During 1996-98, Popocatépetl extruded six named domes in the summit crater (A through F, table 10 and figure 24). Elliptical in shape, the summit crater measures 820 x 650 m, with the longer axis trending approximately E-W. The lowest point of the crater rim occurs along the NE side and lies at 5,180 m elevation; the average elevation of the irregular floor was estimated at 5,030 m (De la Cruz-Reyna et al., in review). The crater's deepest point, at 4,963 m elevation, lay at the bottom of the ~160-m-diameter craterlet formed during the 1922 eruption (BGVN 21:03). Based on the observed shapes and dimensions, the crater could potentially contain a volume of ~35 x 106 m3 before additional material would spill out the low point on the crater rim.

Table 10. Approximate dates when the first extruded material was seen for Popocatépetl's domes A through F. Courtesy of CENAPRED.

Dome Extrusion date Comment
A late Mar 1996 --
B 21 May 1996 --
C 21 Jan 1997 Higher viscosity lavas than domes A or B.
D 04 Jul 1997 Followed the unusually large 30 June 1997 explosion that left a large crater in dome C.
E 19 Aug 1997 --
F 07 Dec 1997 --
Figure (see Caption) Figure 24. Schematic plan views showing the main crater at the summit of Popocatépetl and the sequence of named domes (A-F) found during 26 May 1996 through 7 December 1997. Courtesy of CENAPRED.

In late March 1996, observers saw dome A growing at the bottom of Popocatépetl crater and slowly covering the 1922 craterlet (BGVN 21:03). By 21 May 1996, two elliptical lava bodies were observed in the main crater of Popocat'petl, completely covering the older dome and craterlet (BGVN 21:04). As shown on figure 24, domes A and B grew along the SE and NW sectors of the principal crater's floor (BGVN 22:10). By 26 May 1996 the highest point on dome B reached 5,109 m elevation. Then, after July 1996 dome B's moderate growth slowly declined and subsequent circular fractures on the central dome indicated subsidence. By September 1996 the growth rate could not be measured and ash emissions became smaller. After September 1996, explosive emissions became less frequent, but more intense (e.g. those on 28 and 31 October 1996, BGVN 22:10).

By 21 November 1996, dome B had covered most of dome A and it crept radially out towards the crater's walls. Apparently, explosive activity around that time caused enhanced central subsidence as concentric fractures returned to the dome's surface and the elevation of its central part fell to 5,090 m. More explosions were recorded on 27, 28, and 29 November, on 2, 5, 7, and 29 December, and on 5, 12, 17, and 19 January, 1997. The January explosions were noted as large. By 21 January observers reported that dome B's previously irregular surface appeared smooth due to a cover of fresh tephra. More surprisingly, the central depression within dome B increased in depth, creating what looked like a new crater.

More explosions soon followed (on 23 and 29 January, and on 4, 5, 8, and 25 February; BGVN 22:03). Next, new lava extruded at the center of the depression constructing a new, smaller dome (C). The lavas comprising dome C appeared to have a greater viscosity than those of either A or B.

Explosions on 19 and 20 March 1997 (BGVN 22:04) failed to remove significant proportions of dome C; by 23 April dome C's central part reached 5,060 m elevation (figure 24). As previously reported (BGVN 22:04 and 22:07), subsequent explosions (24 and 29 April, 11, 14, 15, 24, and 27 May, and 3 and 11 June 1997) partially destroyed dome C leaving it covered by explosive clasts of very different sizes. Moreover, the central part of dome C had subsided, leaving its lowest point at 5,049 m elevation. More explosions on 14, 19, 21, and 30 June and on 2 July thwarted observations of the crater's interior. The 30 June 1997 explosion, the largest since the eruption began in 1994, quickly dispatched an ash column to 13 km altitude (BGVN 22:07). When observers looked into the crater on 4 July 1997, dome C had been partially destroyed and contained a large crater.

Within that crater there lay a dish-shaped zone of fresh ropy-lava given the name dome D. In addition, tongues of material radiated from the crater over the volcano's S and SE flanks; these were interpreted as granular flows deposited by the 30 June eruption (BGVN 22:07). Although not previously reported, on 10 August subsidence and radial fracturing became more evident on dome D. Later, by 19 August, dome D sprouted additional lava thus forming what was termed dome E (BGVN 22:10).

Dome E, initially an elliptical lobe that was 50-m long, 36-m wide, and 6-m high, had a very rough surface texture. Dome E later attained a circular shape, and by 10 September it had almost filled the hosting craterlet within the surrounding dome's body. Apart from some radial fractures, the surface appearance was rather regular with a slight inner depression and a region emitting gases in the center. This circular center had a height of 5,105 m elevation. From then on, E extruded in a piston-like manner and when seen on 22 October, E retained an almost cylindrical shape: Its height had grown about 15 m without significant change in its horizontal extent. When viewed on 29 November E's surface appeared smoother except for the presence of some minor explosion craterlets.

Starting on 25 November, significant seismic changes indicated subcrater magmatism and on 2 December observers noted both mild ash emissions and night-time incandescence. On 7 December observers recognized yet another new, large lava body in the crater (BGVN 22:11).

Dome F was composed of a lower-viscosity, black, ropy lava; it subsequently grew to a maximum diameter of 380 m and exceeded by 20 m the height of dome E as measured on 22 October. Relative quiet during 7-24 December ended on the latter day with a 30-minute-long series of explosions and moderate ash emissions. Volcano-tectonic seismicity took place during the final days of 1997, leading up to a large 1 January explosion. Aerial observers on 6 January saw that dome F had been partially destroyed and covered by volcanic debris (BGVN 22:12). The negative values on table 11 correspond to the 1 January 1998 explosion, which left a crater at dome F's center. This crater was 250 m in diameter and 60 m in depth with a shape similar to the 1922 dome and craterlet. Dense, degassed lava blocks with diameters of 0.6-0.8 m were thrown 2 km from the crater; they produced impact craters about 3 m in diameter.

Table 11. Estimates of Popocatépetl dome volumes for the stated dates. Volumes are "actual" and not adjusted as dense rock equivalents. The maximum crater capacity is estimated at ~ 35 x 106 m3. The negative emitted volume shown for 1 January 1998 appears because explosions removed material from the dome, although some uncertain amount of these broken dome fragments remained within the crater (see text). Courtesy of CENAPRED.

Date Emitted volume (m3) Cumulative volume (m3) Percent of crater capacity
Mar 1996-Oct 1997 9,500,000 9,500,000 27%
Nov 1997 1,500,000 11,000,000 31%
Dec 1997 2,500,000 13,500,000 38%
01 Jan 1998 -1,000,000 12,500,000 35%

Afterwards, until early February 1998, the volcano remained relatively quiet. On 14 March 1998, new precursory seismicity was detected. In behavior reminiscent of December 1997 and January 1998, two explosions occurred on 21 March at 0511 and 1559. The first, a moderately explosive exhalation, produced light ashfalls on towns in the state of Puebla. The second, a more intense explosion, produced a 3-km-tall plume and threw blocks 2-4 km about the crater. A 23 March exhalation appeared very similar to the one at 0511 on 21 March, resulting in a low-altitude plume that the wind dispersed NW. No damage or casualties were reported.

Reference. De la Cruz-Reyna, S., Macias, J.L., and Castillo-Alanis, F., (manuscript submitted late February 1998), Dome growth and associated activity during the current eruptive episode of Popocatepetl volcano, central Mexico: Earth and Planetary Sciences Letters.

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-Reyna1,2, Roberto Meli1, Jose Luis Macias1,2, Francisco Castillo Alanis1, and Bulamaro Cabrera3; 1Instituto de Geofisica, UNAM, Coyoac n 04510, México D.F., México; 2CENAPRED, Delfin Madrigal 665, Col. Pedregal de Santo Domingo, Coyoacan, 04360, México D.F., México; 3SCT, Aldadena 23, 6o piso, Col. N poles, 03810, México D.F., México.


Rabaul (Papua New Guinea) — February 1998 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)


January activity presages February eruption

A continuous glow was visible at nights throughout January 1998 at Tavurvur crater, and there was also a slow but steady inflation of the volcano during the month. An expected eruption began at Tavurvur on 3 February 1998.

The eruption began with emissions of pale to dark gray ash clouds typically 5-20 minutes apart. There was no noise associated with the emissions although small, low-frequency seismic events did accompany each event. Over the next few days roaring and rumbling could be heard down-wind (to the SE) of Tavurvur and seismic events became generally larger. Loud explosions were recorded once to 5 times daily. The explosions usually were accompanied by forceful emissions of dense gray to dark ash clouds that rose to 2000-3500 m above the crater. These were followed by moderate to small ash-cloud emissions lasting ~30 minutes. During the explosions lava fragments were ejected to heights of 200-300 m, showering the slopes 200-500 m from the base of the cone. Some small ash flows were also generated during explosions. During strong ash emissions at night, successive 5-minute projections of glowing lava fragments were observed. This pattern of eruptive activity lasted until the end of February.

Ash rose to 300 m above the crater (600 m a.s.l.) and was usually distributed to the SE, with occasional drifts to the N and W. Each ash emission produced light ash fall at Talwat village SE of Tavurvur near the base of the cone. There was also very light ash fall recorded elsewhere on New Britain, including at Tokua airport 20 km from Tavurvur.

Seismic activity was generally low. A slight increase in the frequency of volcanic earthquakes in early February reflected the increase in activity at the summit of Tavurvur. The increase was indicated on the 1- minute RSAM data as background values of 20 RSAM units increased to 100. Between 10 and 48 earthquakes were recorded daily. The average number per day was 27, but after 22 February they dropped to 9. Two high-frequency earthquakes recorded during February were located 20-30 km ESE of the caldera.

During the current phase of eruptive activity there has been no significant change in ground deformation compared to the inflationary trend prior to the eruption. A water-tube tiltmeter located 3.5 km NW of Tavurvur showed a slow yet steady rate of inflation: total accumulated tilt for February was 4 µrad. Real-time GPS measurement taken from a remote station on Matupit Island 2 km W of Tavurvur showed no significant change.

Although COSPEC SO2 measurements lacked precursory signatures suggesting an eruption, a slightly higher SO2 flux of ~350 metric tons/day was measured when the eruption started. After several days the flux decreased to a low level of ~190 tons/day. The low flux values attained during the month were partly due to a change in wind direction away from the fixed observation post.

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 (RVO), P.O. Box 386, Rabaul, Papua New Guinea.


Sheveluch (Russia) — February 1998 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Frequent gas-and-steam plumes

During February seismicity remained near or slightly above background level. No volcanic activity was observed during 27 January-1 February. Gas-and-steam plumes rose 50-1,000 m above the volcano on 3, 4, 8, 11-12, 12-14, 17-18, 20, 24, 28 February, and 1 March.

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


Soufriere Hills (United Kingdom) — February 1998 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)


Dome growth continues; discussion of the 26 December dome collapse

The following summarizes a scientific report of the Montserrat Volcano Observatory (MVO) for 18 January-1 February, a time period when seismic and volcanic activity were low but dome growth continued. In addition, this report condenses MVO's Special Report 6 on the 26 December 1997 dome collapse, perhaps the most intense outburst yet recorded during the current crisis.

Visual observations. Few views of the dome complex were obtained due to poor visibility until the end of January, when observers saw active growth in the crater left by the 26 December 1997 dome collapse in the volcano's SW sector (BGVN 22:12). Also reported were occasional rockfalls, ash venting, steaming, and a dilute steam-and-ash plume that drifted WNW. Ash venting and rockfall activity became slightly more vigorous at the end of January, when a shift in prevailing winds sent light ashfall to the N part of the island.

Seismicity. Rockfall signals dominated seismicity; most coincided with a seismic-amplitude cycle with a periodicity of ~12 hours. This regular, slight increase in seismicity despite any major events has continued since the 26 December collapse and has been interpreted to indicate cyclical degassing as the dome grew.

Ground deformation. Displacement vectors for the interval April/May 1997 to January 1998 for sites around the volcano (table 25) revealed that areas NE, E, and SE of the volcano had been significantly displaced. The sector between Whites, Hermitage, and Roches Yard had moved ~6 cm NNE. Similar measurements at Long Ground, Tar River, and Perches suggested that these sites were displaced as a homogenous unit with little deformation. The Hermitage site showed considerably more movement than the others. Because of its proximity to the dome, it may have been more strongly influenced by local pressure or loading effects. Distant sites on the volcano's W and N flanks (Dagenham, Old Towne and Windy Hill) showed less displacement.

Table 25. Displacement vectors during April 1997-January 1998 for sites around Soufriere Hills. The site at Harris is the baseline. The Tar River vector reflects readings beginning in March 1997; the Roches Yard vector, beginning in October 1996. Courtesy of MVO.

Site Displacement (mm) Vector (degrees from grid north)
Whites 25 353
Long Ground 66 033
Hermitage 100 026
Tar River 57 030
Perches 59 049
Roches Yard 66 342
Windy Hill 15 283
Dagenham 16 077
Old Towne (M27) 19 084

New GPS sites were established on the summit of Gages Mountain and in the N part of the island at Drummond's and Blakes. A triple-prism EDM reflector was installed on the remnant of Peak B, a piece of the crater wall between Tuitt's and Mosquito Ghauts. The reflector was installed less than 100 m from the dome's N limit and, along with the new GPS sites, will monitor the N flanks.

Environmental monitoring. Results from diffusion tubes revealed slightly elevated SO2 levels (11.5 ppb) at St. George's Hill. On 24 January new tubes were placed at various sites on the W side of island. Geochemical sampling showed that all samples had3) at the CPS site (~7 km NNW of the volcano), presumably due to human activity in this area.

Report on the 26 December dome collapse. The collapse occurred early on 26 December 1997 after the very rapid dome growth that followed the explosive phase of September-22 October 1997 (BGVN 22:09-22:11). Dome growth within the explosion crater and large lobes extruding N and S formed a large dome over the Galway's Wall attaining a summit elevation of 1,020 m (figure 38), the greatest dome height since the eruption began. Seismic activity was generally low but a hybrid swarm beginning at 1430 on 24 December merged to continuous tremor a few hours before the collapse.

Figure (see Caption) Figure 38. Cross-section of the Galway's Wall area prior to and after the 26 December dome collapse. "A" is presented as a reference point on figure 39. "Before" information is based on survey data from 23 November and 8 December as well as from video and photographs. "After" is based on information from video and photographs. Courtesy of MVO.

The slope failure and dome collapse occurred at about 0300 and lasted ~15 minutes. Seismic evidence provided information on the duration of the event and the timing of specific phenomena, but reconstruction of the event has been done chiefly by evaluating deposits, changes in dome and flank morphology, and changes due to material transportation processes.

The event included a debris avalanche from the Galway's Wall and Galway's Soufriere areas and the consequent collapse of a destabilized portion of the lava dome (figures 38 and 39). The debris avalanche moved down the SW flank following the White River, leaving deposits through much of the valley; these deposits were later blanketed by pyroclastic-flow deposits. A portion of the material may have reached the ocean, generating a small tsunami (BGVN 22:12). The dome collapse produced pyroclastic flows and ash-cloud surges within the White River valley; a considerable volume of this material may have also reached the sea.

Figure (see Caption) Figure 39. Maps of the Galway's Wall area prior to and after the 26 December dome collapse. Both maps have the same scale and orientation. "A" is presented as a reference point on figure 37. "Before" information is based on survey data from 23 November and 8 December as well as video and photographs. "After" map is based on information from video and photographs. Courtesy of MVO.

Very intense pyroclastic surges occurred during the collapse, causing widespread devastation in the area S of Gingoes Ghaut. Some surges were associated with the main flows, but others may have been caused by explosions in the collapsing dome. A convective ash cloud generated by the pyroclastic flows and surges rose ~14.3 km and deposited fine ash over SW Montserrat.

Deposits. Five main depositional units from the 26 December event were identified (figure 40): debris-avalanche deposits, block-and-ash flow deposits, pyroclastic-surge deposits, co- ignimbrite fallout, and a possible blast deposit.

Figure (see Caption) Figure 40. Map of deposits from the 26 December dome collapse. Arrows indicate orientation of trees that were blown down. Courtesy of MVO.

A ~500 m wide, 25-70 m thick debris-avalanche deposit covered the central delta and lower reaches of the White River valley. The hummocky, orange-brown debris was poorly sorted, coarse, and blocky with an irregular bulbous ~25 m-high front. The deposit resulted from a slope failure of hydrothermally altered rocks in the Galway's Soufriere area, the lower outward flank of the Galway's Wall, and the overlying apron of fresh dome talus. Much of the material had a smoothed, heavily scoured upper surface with discontinuous remnants of pre- existing hydrothermally altered stratigraphy preserved within the deposit.

Block-and-ash deposits left by pyroclastic flows were similar to previous dome collapse flows at Soufriere Hills. They comprised dense to slightly vesicular (friable-textured) blocks in a poorly sorted, ash-rich matrix with little internal organization. The pyroclastic flows were largely confined to the White River valley, although some material spilled out at the river bend (~1.7 km from the coast) and traveled towards Morris'. The flows produced erosion features over the area between the White River valley and Morris' village. The block-and- ash deposits ponded behind and on top of the debris-avalanche deposits, filling the remainder of the White River valley to a maximum depth of 50-70 m. Block-and-ash deposits on the river delta were relatively thin (50-70 cm), broad, and flat-lying. They were poorly sorted with blocks reaching a maximum size of about 1 m (blocks >0.1 m formed ~10% of the surface).

Surge deposits associated with the collapse covered 9.1 km2 around the volcano's S flanks. Quite variable, some deposits differed markedly from previous surge deposits associated with pyroclastic-flow emplacement at Soufriere Hills. Conventional ash-cloud-surge deposits were found E of the White River valley on the delta and in the Trials area. These deposits were composed of a fine grained, ash-rich, and sandy layer (6-10 cm thick) with an underlying thin (0.5-2 cm) fines-depleted coarse sand layer. The surge deposits between the White River valley and German's Ghaut varied but the dominant facies was a 15-40 cm-thick, coarse sand/gravel fines- depleted unit. In some areas this deposit was overlain by a second fine-grained surge deposit. The coarse surge deposits largely comprised sub-angular dense dome rock and crystals with little pumiceous or friable component.

Small secondary pyroclastic-flow deposits with abundant charcoal occurred in the deep ghauts that drain the area covered by the surge deposits. One of these flows drained towards the E side of Soufriere Hills down Dry Ghaut. The thin, highly mobile flow was confined to the bottom of the ghaut (average width of 2-4 m) and extended to within 300 m of the sea. The deposit was poorly sorted and 50-70 cm thick, consisting predominantly of fine ash-rich sand.

A possible blast deposit was found on the volcano's SW flank between Gingoes Ghaut and the White River. The deposit comprised angular to sub-angular lithic clasts scattered on the surface, some up to 70 cm in diameter. The surface of the deposit was very subtly corrugated in the flow direction, suggesting a highly energetic emplacement mechanism.. This deposit was distinctly different from thinly spread 'normal' facies block- and-ash flows as it was locally only one clast thick and was completely fines depleted. Dense, fresh, angular dome rock made up most of the deposit, with small amounts of altered dome rock and sub-rounded, semi-vesicular, steely blue-gray dome rock. There was a marked lack of impact craters, bread crust-textured clast, or any ballistic blocks.

Co-ignimbrite ash covered most of the SW part of Montserrat and draped all the 26 December deposits, although heavy rains in early January altered the deposit. Near the coast in the Trials area the co- ignimbrite ash fell as accretionary lapilli, caused by incorporation of steam generated by hot material entering the ocean. The accretionary lapilli were up to 8 mm in diameter and formed a layer up to 4 cm thick. The fine-grained, crystal- rich ash was typical of ash generated from pyroclastic flows sourced from dome collapse. The co-ignimbrite ash plume reached an altitude of ~14 km and light ash fall was reported from Guadeloupe (60 km SSW), as well as St. Vincent and Bequia (both ~400 km SSW).

Temperatures determined from the various deposits several days after the eruption had values up to 293°C (table 26). The debris-avalanche deposit was mainly emplaced cold, although parts of the Galway's Soufriere and dome talus debris would have been warm at the time of incorporation into the avalanche.

Table 26. Temperature measurements for deposits from the 26 December collapse. 'PF' refers to pyroclastic flow; 'DAD', to the debris-avalanche deposit. Courtesy of MVO.

Deposit type Location Measurement depth (cm) Days after event Temp (°C)
Secondary PF Dry Ghaut 20 4 48
Secondary PF Dry Ghaut 25 4 138
Secondary PF Dry Ghaut 35 4 122
Surge White River delta 30 9 155
Surge White River delta 60 9 216
Surge White River delta 30 9 228
Surge White River delta 30 9 83
Surge White River delta 50 9 93
Fumarole White River delta 30 9 68
Surge/PF over DAD 20 13 157
Surge/PF over DAD 25 13 103
Surge/PF over DAD 60 13 293

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, P. O. Box 292, Plymouth, Montserrat (URL: http://www.mvo.ms/).

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