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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 22, Number 11 (November 1997)

Managing Editor: Richard Wunderman

Ambrym (Vanuatu)

August visit reveals lava fountains, Strombolian explosions

Arenal (Costa Rica)

January-November tremor and earthquakes

Asosan (Japan)

Two tourists killed by volcanic gas on 23 November

Atmospheric Effects (1995-2001) (Unknown)

Volcanic aerosol optical thicknesses since 1960

Avachinsky (Russia)

Fumarolic plume on 22 December

Bezymianny (Russia)

Explosive eruption on 5 December

Campi Flegrei (Italy)

Increase in sulfate concentrations and fumarole temperatures

Chiginagak (United States)

Increased fumarolic activity in late October

Karymsky (Russia)

Low-level Strombolian activity continues

Kilauea (United States)

Bench collapse and pit formation; lava flows continue to reach the coast

Klyuchevskoy (Russia)

Elevated seismicity during 13 October-1 December; gas-and-steam plumes

Koryaksky (Russia)

Above-background seismicity in late December

Langila (Papua New Guinea)

Increased eruptive activity at Crater 2

Long Valley (United States)

Summary of 1996 activity

Manam (Papua New Guinea)

Moderate explosions in late November

Monowai (New Zealand)

Inferred eruption during 15-18 December

Obituary Notices (Unknown)

Death of Werner F. Giggenbach at Rabaul

Poas (Costa Rica)

June-November earthquakes; thermally stable fumaroles

Popocatepetl (Mexico)

Low activity through November; lava extrusion and explosion in December

Rabaul (Papua New Guinea)

Slow ongoing inflation

Sheveluch (Russia)

Normal seismicity and fumarolic activity

Soufriere Hills (United Kingdom)

Explosions and dome growth

Vulcano (Italy)

Trends in fumarolic gas composition during 1996-97

Yasur (Vanuatu)

Strombolian eruptions; decreasing seismic activity since March 1997



Ambrym (Vanuatu) — November 1997 Citation iconCite this Report

Ambrym

Vanuatu

16.25°S, 168.12°E; summit elev. 1334 m

All times are local (unless otherwise noted)


August visit reveals lava fountains, Strombolian explosions

During 5-13 August 1997, a team from the Société de Volcanologie Genève (SVG) observed Ambrym caldera and deployed an infrared (1.55 µm wavelength) optical pyrometer (Optix-G, Keller GMBH., Ibbenburen-Lagenbeck). Temperatures of lavas were estimated from the pyrometer by measuring emissivity factors of lavas heated to known temperatures in an oven. In some cases comparisons were also made with a thermocouple on the floor of Marum crater (contact the authors regarding procedures and results).

At Benbow cone, most activity, including lava fountaining, occurred inside the S part of the crater. A deep crater in the cone's N flank emitted a large amount of hot, very concentrated gas. The crater bottom was not visible; however, strong night glow revealed the proximity of magma.

At Marum cone, three different craters were active during the SVG visit. At Mbwelesu, the main crater, two closely spaced openings full of lava were visible from the rim. The lava surface was continuously overturned by fountains that were tens of meters high. The maximum temperature of the chimney opening was estimated with the optical pyrometer at 910°C. The pyrometer measurement was taken on the NNE side of the crater rim under conditions of good visibility and strong degassing.

At Niri Mbwelesu, a secondary crater close to Mbwelesu's rim, strong degassing was observed. Although the crater was often full of vapor, occasionally the bottom was visible. A small, elongated lake surrounded by fumaroles was seen in the crater near a glowing opening that was emitting pulses of hot gas; however, magma was not directly observed.

Inside Niri Mbwelesu Taten, a small collapse pit (169 x 185 m; 140 m deep) to the S of Niri Mbwelesu, Strombolian explosions were observed until 7 August. The explosions lasted a few hours, stopped, then resumed a few hours later. The explosions were caused by the bursting of magma bubbles 2-3 m in diameter as they reached the surface. The noise from the explosions could be heard a few kilometers away. Shock waves were sometimes observed in the cloud above the pit. The maximum temperature of liquid lava inside the pit was estimated with the optical pyrometer at 964°C. Pyrometer measurements were taken standing on the S border of the crater rim under conditions of good visibility. Maximum temperature estimates on liquid lava varied between ~935°C and 965°C.

In addition, the team measured rain acidity at different sites inside the caldera. A clear gradient was found: the rain had a pH of 2 on the Benbow crater rim and a pH of 4 close to the caldera's border.

Geologic Background. Ambrym, a large basaltic volcano with a 12-km-wide caldera, is one of the most active volcanoes of the New Hebrides Arc. A thick, almost exclusively pyroclastic sequence, initially dacitic then basaltic, overlies lava flows of a pre-caldera shield volcano. The caldera was formed during a major Plinian eruption with dacitic pyroclastic flows about 1,900 years ago. Post-caldera eruptions, primarily from Marum and Benbow cones, have partially filled the caldera floor and produced lava flows that ponded on the floor or overflowed through gaps in the caldera rim. Post-caldera eruptions have also formed a series of scoria cones and maars along a fissure system oriented ENE-WSW. Eruptions have apparently occurred almost yearly during historical time from cones within the caldera or from flank vents. However, from 1850 to 1950, reporting was mostly limited to extra-caldera eruptions that would have affected local populations.

Information Contacts: P. Vetch and S. Haefeli, Société de Volcanologie Genève (SVG), C.P. 298, CH-1225, Chene-bourg, Switzerland.


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

Arenal

Costa Rica

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

All times are local (unless otherwise noted)


January-November tremor and earthquakes

Seismicity for Arenal during January through November 1997 is shown on figure 83. The monthly earthquake count peaked in July at around 1,600 events, but many months had fewer than 600. Tremor reached durations of 250-300 hours during January, March, and June.

Figure (see Caption) Figure 83. Arenal's monthly earthquake count and tremor duration for the interval January-October 1997. Data were registered at station "VACR," 2.7 km NE of the main crater. Courtesy of OVSICORI-UNA

Arenal's first historical eruption, in mid-1968, began an unbroken sequence of Strombolian explosions and lava effusion from multiple vents. Since then the volcano has erupted material of basaltic-andesite composition.

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

Information Contacts: E. Fernandez, R. Van der Laat, F. de Obaldia, T. Marino, V. Barboza, W. Jimenez, R. Saenz, E. Duarte, M. Martinez, E. Hernandez, and F. Vega, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica.


Asosan (Japan) — November 1997 Citation iconCite this Report

Asosan

Japan

32.884°N, 131.104°E; summit elev. 1592 m

All times are local (unless otherwise noted)


Two tourists killed by volcanic gas on 23 November

Tomoki Tsutsui (Aso Volcanological Laboratory, Kyoto University) reported that a new fumarolic vent ~10 m in diameter formed on the S wall of Crater 1 in early November; later, small mounds of mud formed around the vent. Although Crater 1 had been quiet since 1993, hot greenish-gray water remained in the crater. Videos of Crater 1 taken by the Aso Volcano Museum recorded emissions of mud fragments and white fumes from the new vent, as well as a bubbling noise; other instruments detected low-level volcanic tremors.

According to news reports, inhalation of volcanic gas killed two men, aged 62 and 51 years, after they collapsed ~100 m S of Crater 1's rim at 0945 and 1040 on 23 November. Volcanic gas concentration around the crater is monitored using a sensor installed by the Japan Meteorological Agency in April 1997. Due to high levels of SO2 (~5 ppm), the Crater 1 overlook was closed on the morning of 23 November, but re-opened at 0900 when the SO2 level dropped to2 levels rose to ~8 ppm. The weather station at Aso had recorded no abnormal volcanic conditions.

Seventy-one people have been hospitalized due to inhalation of volcanic gases at Aso since 1980; of those, seven were killed. In June 1994, five junior high school students on a field trip collapsed near Crater 1.

Aso, a 24-km wide caldera, produced Pleistocene pyroclastic-flow deposits that cover much of Kyushu. Fifteen central cones form an E-W line on the caldera floor. Naka-dake, one of the intra-caldera cones, has erupted more than 165 times since 553 AD. Naka-dake has a group of craters (1.1 km long) including Crater 1 at the summit. Strombolian, phreatic, and phreatomagmatic eruptions are common in Crater 1. The 4 km2 100-m-deep Crater 1 is accessible by cable car, automobile, and on foot.

Geologic Background. The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 km3 of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 CE. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.

Information Contacts: Tomoki Tsutsui, Aso Volcanological Laboratory, Kyoto University, Choyo, Aso, Kumamoto, 869-1404, Japan; Volcano Research Center, Earthquake Research Institute (ERI), University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113, Japan (URL: http://www.eri.u-tokyo.ac.jp/VRC/index_E.html).


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

Atmospheric Effects (1995-2001)

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Volcanic aerosol optical thicknesses since 1960

Richard A. Keen submitted the following report. About once per year, on average, the moon is eclipsed as it passes into the earth's shadow; at these times it can be used a remote sensor of the globally averaged optical depth of stratospheric aerosols of volcanic origin. Conceptually, the linkage between volcanic aerosols and lunar eclipses is as follows: 1) The moon is visible during total lunar eclipses due to sunlight refracted into the shadow (umbra) by the earth's atmosphere (primarily the stratosphere); 2) Stratospheric aerosols reduce the transmission of sunlight into the umbra; and 3) The path length of sunlight through a stratospheric aerosol layer is ~40x the vertical thickness of the layer. Therefore, the brightness of the eclipsed moon is extremely sensitive to the amount of aerosols in the stratosphere.

Methodology and data reduction. Aerosol optical thicknesses can be calculated for the date of an eclipse from the difference between the observed brightness of the eclipse and a modeled brightness computed for an aerosol-free standard atmosphere, modified by assumed distributions of ozone and cloud. A report on this technique, applied to observations during 1960 through 1982, appeared in Keen (1983); an update following the eruption of Pinatubo was reported in February 1993 (Bulletin v. 18, no. 2).

This report updates the time series from 1960 through the lunar eclipse of 16 September 1997 (figure 4), the last total lunar eclipse until January 2001. Plotted values are actual derived optical depths, modified as described below. Due to the higher concentration of Agung and El Chichón aerosols in the southern and northern hemispheres, respectively, a sampling bias due to the moon's passing though the southern or northern portion of the umbra was removed by using an empirical adjustment factor of 0.8 (thus, if the moon passed south of the earth's shadow axis during an eclipse following Agung, the derived optical thickness was multiplied by 0.8, while the derived value was divided by 0.8 if the moon passed north of the axis).

Figure with caption Figure 4. Volcanic aerosol optical thicknesses derived from 35 total or near-total lunar eclipses during 1960-97. Courtesy of Richard Keen.

No lunar eclipses occurred until 18 months after the June 1991 Pinatubo eruption, while results from Agung and El Chichón indicate that peak optical depths occurred about 9 months after those eruptions. Therefore, for plotting purposes, the time series of optical thicknesses following Pinatubo was extrapolated backwards to a date 9 months after the eruption using a composite decay curve derived from the Agung and El Chichón data. Finally, the global optical depths were set to zero on the dates of the eruptions of Agung, Fuego, and Pinatubo; observed values were near zero for eclipses close to the eruption dates of Fernandina and El Chichón.

Time series. The volcanic eruptions probably responsible for the major peaks in the time series are identified, although the correlation of Fernandina with the 1968 peak is highly uncertain. Comparative maximum global optical thicknesses are: Pinatubo (1991), 0.15; Agung (1963), 0.10; El Chichón (1982), 0.09; Fernandina (1968), 0.06; Fuego (1974), 0.04. The results indicate that the volcanic aerosol veil from Pinatubo disappeared between the eclipses of November 1993 and April 1996, with optical depth probably reaching zero sometime in 1995. A slight increase to an observed value of 0.01 for the September 1997 eclipse is close to the noise level due to the uncertainty in the brightness observations; if real, it could indicate aerosols from the eruption of Soufriere Hills. Interestingly, a similarly slight increase in optical depth in 1979 may have been due to the eruption of Soufriere of St. Vincent.

Acknowledgments. Thanks are due to the following who supplied observations of the four eclipses in 1996-97: K. Hornoch and M. Plsek (Czech Republic), G. Glitscher (Germany), K. Yoshimoto (Japan), K. Al-Tell, N. Abanda, M. Odeh, S. Abdo (Jordan), R. Bouma, G. Comello, H. Feijth, and E. van Dijk (Netherlands), B. Granslo and O. Skilbrei (Norway), C. Vitorino and A. Pereira (Portugal), P. Schlyter (Sweden), R. Pickard, A. Moss, J. Shanklin, and W. Worraker (UK), and D. Green (USA).

Reference. Keen, R., 1983, Volcanic aerosols and lunar eclipses: Science, v. 222, p. 1011- 1013.

Geologic Background. 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 thorugh 1989. Lidar data and other atmospheric observations were again published intermittently between 1995 and 2001; those reports are included here.

Information Contacts: Richard A. Keen, 34296 Gap Road, Golden, CO 80403 USA.


Avachinsky (Russia) — November 1997 Citation iconCite this Report

Avachinsky

Russia

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

All times are local (unless otherwise noted)


Fumarolic plume on 22 December

Seismicity continued at normal background levels during November 1996-December 1997. On 22 December, a fumarolic plume rose ~200 m above the crater.

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

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


Bezymianny (Russia) — November 1997 Citation iconCite this Report

Bezymianny

Russia

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

All times are local (unless otherwise noted)


Explosive eruption on 5 December

An explosive eruption began on 5 December. Seismic and fumarolic activity had mainly been normal since May 1997 (BGVN 22:09). Seismicity was at background level during 13 October-2 November with normal fumarolic activity (plumes 50-100 m tall) observed during 21-26 October. During 3-9 November seismicity increased and plumes up to 1 km high were seen; the plume extended 10-15 km SSE on 8-9 November. Normal low plumes were again seen on 12, 14-15, 18, 27, and 30 November.

A growing hot spot was monitored on satellite images by Alaska Volcano Observatory (AVO) remote sensing specialists during 3-4 December. The hot spot was not accompanied by unusual activity; it was assumed to be related to small debris avalanches at the dome. Visual observations during that period indicated that a fumarolic plume rose 500 m above the volcano and extended 15-20 km SW.

An explosive eruption began at about 0630 on 5 December. No preliminary seismicity was detected; however, the eruption's onset was indicated by an abrupt increase in seismicity. By 0830, the eruption plume reached a height of 6 km and had traveled ~20 km NE. By 1200 observers in the towns of Kozyrevsky and Klyuchi reported an increase in the eruption's intensity; at 1215, the Kamchatka Volcanic Eruption Response Team (KVERT) estimated the plume height at ~9 km dispersing >50 km NE . . . . Seismicity remained elevated until 1400, but eruptive activity declined.

Several volcanic ash advisories were issued to warn aviators about the ash plume during 5-7 December. For example, an advisory at 1015 on 5 December reported an ash plume extending 15 km NE at an altitude of ~6 km. Another advisory cited a GMS infrared image taken at [0932] showing a plume 55 km wide extending NE (figure 4). [Satellite imagery at 1332 showed the plume rising to ~9-10 km; it was 63 km wide and extended 211 km E. Pilot reports later in the day estimated the ash plume at altitudes of ~12-13 km.] . . . .

Figure (see Caption) Figure 4. [Sketches showing Bezymianny's ash plume on 5 December 1997 at 0932 (2132 GMT on 4 December) and 1332 (0132 GMT) based on GMS infrared satellite imagery. Courtesy of SAB.]

. . . [Judging from] satellite imagery, activity declined during the night of 5-6 December. At 0800 on 6 December, a small steam plume with little to no ash rose ~3.5-4 km and moved ~20 km NE. By 1030 decreased eruptive activity led KVERT to downgrade the hazard status to yellow (during the eruption it was red). Local seismicity was masked by intense aftershocks following a M 7.8 earthquake off the E coast of Kamchatka during the night of 5-6 December.

On 7 December, a gas-and-steam plume rose 500 m above the volcano and extended as far as 1 km SE. A fumarolic plume on 8-9 December rose 50-100 m and extended SE. By 9 December, the hazard status had returned to green and seismicity was at background. During 15-21 December, the volcano was obscured by clouds but seismicity remained normal. A fumarolic plume on 24 December rose 50-100 m above the volcano.

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, IVGG, Piip Blvd, 9 Petropavlovsk-Kamchatskiy, 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; NOAA/NESDIS Satellite Analysis Branch (SAB), Room 401, 5200 Auth Road, Camp Spring, MD 20746, USA.


Campi Flegrei (Italy) — November 1997 Citation iconCite this Report

Campi Flegrei

Italy

40.827°N, 14.139°E; summit elev. 458 m

All times are local (unless otherwise noted)


Increase in sulfate concentrations and fumarole temperatures

Since the ground upheaval events of 1982-84, systematic geochemical surveillance has been performed at Campi Flegrei. Fumarolic gases, crater lakes, and thermal springs have been monitored; since 1984, no significant physical or chemical changes have occurred.

However, two characteristics showed a statistically significant change; the temperature in the Bocca Grande fumarole increased (figure 19) and the sulfate concentration in crater lakes and thermal springs increased sharply during 1995-97 (figure 20). These increases may have resulted from a perturbation in the area caused by increased permeability; thus the interaction of confined, hot, sulfate-rich aquifers may have increased.

Figure (see Caption) Figure 19. Temperature of Bocca Grande fumarole at Campi Flegrei during 1988-97. Courtesy of M. Martini.
Figure (see Caption) Figure 20. Sulfate concentration in crater lakes and thermal springs at Campi Flegrei, 1988-97. Courtesy of M. Martini.

Geologic Background. Campi Flegrei is a large 13-km-wide caldera on the outskirts of Naples that contains numerous phreatic tuff rings and pyroclastic cones. The caldera margins are poorly defined, and on the south lie beneath the Gulf of Pozzuoli. Episodes of dramatic uplift and subsidence within the dominantly trachytic caldera have occurred since Roman times. The earliest known eruptive products are dated 47,000 yrs BP. The caldera formed following two large explosive eruptions, the massive Campanian ignimbrite about 36,000 BP, and the over 40 km3 Neapolitan Yellow Tuff (NYT) about 15,000 BP. Following eruption of the NYT a large number of eruptions have taken place from widely scattered subaerial and submarine vents. Most activity occurred during three intervals: 15,000-9500, 8600-8200, and 4800-3800 BP. Two eruptions have occurred in historical time, one in 1158 at Solfatara and the other in 1538 that formed the Monte Nuovo cinder cone.

Information Contacts: Marino Martini, Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, 50125, Firenze, Italy.


Chiginagak (United States) — November 1997 Citation iconCite this Report

Chiginagak

United States

57.135°N, 156.99°W; summit elev. 2221 m

All times are local (unless otherwise noted)


Increased fumarolic activity in late October

Beginning 22 October, the Alaska Volcano Observatory (AVO) received several reports of increased steaming, snowmelt, and sulfur smells at Chiginagak volcano. Residents of the area, including the community of Pilot Point (60 km NW), noticed increased steam emissions as early as mid-summer 1997. Possible new thermal anomalies were detected on AVHRR satellite imagery in late October. According to AVO, this change in fumarolic activity may have reflected increased heat flux at the volcano.

On 30 October, observers on an AVO flight reported an enlarged area of fumarolic activity directly above previously known sites, including new fumaroles at approximately 1,920 m. However, there were no signs of recently erupted ash, large-scale melting, or mud flows. Observers at Pilot Point reported vigorous steam emissions over the following weeks. During the first week of December, persistent poor weather conditions obscured observations; however, steam was observed on 2 and 3 December. No thermal anomalies were observed on satellite images during the first week of December.

Chiginagak is not monitored by scientific instrumentation; however, satellite imagery and observers in Pilot Point provide information. In addition, Chiginagak is located in a National Wildlife Refuge; the U.S. Fish and Wildlife Service frequently overflies the area, especially when activity persists or intensifies.

Geologic Background. The symmetrical, calc-alkaline Chiginagak stratovolcano located about 15 km NW of Chiginagak Bay contains a small summit crater, which is breached to the south, and one or more summit lava domes. Satellitic lava domes occur high on the NW and SE flanks of the glacier-mantled volcano. An unglaciated lava flow and an overlying pyroclastic-flow deposit extending east from the summit are the most recent products of Chiginagak. They most likely originated from a lava dome at 1687 m on the SE flank, 1 km from the summit of the volcano, which has variably been estimated to be from 2075 to 2221 m high. Brief ash eruptions were reported in July 1971 and August 1998. Fumarolic activity occurs at 1600 m elevation on the NE flank of the volcano, and two areas of hot-spring travertine deposition are located at the NW base of the volcano near Volcano Creek.

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


Karymsky (Russia) — November 1997 Citation iconCite this Report

Karymsky

Russia

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

All times are local (unless otherwise noted)


Low-level Strombolian activity continues

During 13 October-24 November seismicity remained above background level; low-level Strombolian eruptive activity that has continued since January 1996 (BGVN 21:01) consisted of gas and ash explosions occurring every 20 minutes, sending ash and steam 200-400 m above the crater. During 24 November- 29 December there was elevated seismicity and explosions every 20-30 minutes that sent ash and steam 300-400 m above the crater. On 14 December, the level of concern was downgraded to yellow from orange, indicating that the volcano's activity was less indicative of a major eruption.

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) — November 1997 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Bench collapse and pit formation; lava flows continue to reach the coast

Activity within the Pu`u `O`o crater was at a diminished level during late October-23 November 1997. Lava in the crater was visible only from the crater walls. The Pu`u `O`o vent rarely effused lava onto the crater floor during November; the magma column remained 10-20 m below the rim. Magma in the vent circulated below the crusted lava surface, where it was not visible except from the air.

Lava from the S shield continued to travel ~10 km to the coast in tubes; travel time was estimated at ~3 hours from the vent to the ocean. The eruption rate was 500,000-600,000 m3/day. Although lava continued to flow into the ocean at East Kamokuna and Waha'ula, no breakouts of lava from the tubes onto the coastal plain occurred after the 18-19 October event (BGVN 22:09).

At East Kamokuna, a bench collapse in the first week of November removed 1.9 hectares of recent deposits and created a new cliff a few meters high and ~50 m long; after the collapse, lava began building a shelf at the foot of the new cliff. Curtain-like steam plumes rose continuously from the 500-m-long edge of the lava flow. A smaller lava bench collapse (0.26 hectares) occurred on 24 November.

Sulfur dioxide emissions from Pu`u `O`o remained high during November. Although during late October the emission rate had been 1,500-2,000 metric tons/day (t/d), during November it increased to 2,800 t/d and occasionally reached 5,000 t/d. On 16 November, eastern Hawaii, especially Hawaii Volcanoes National Park, was engulfed in one of 1997's worst volcanic-smog episodes. Elevated levels of volcanic smog were detected as far away as Oahu (~330 km NW). Gentle winds from the SE pushed SO2 emissions from Kilauea's E rift zone inland, resulting in levels of airborne SO2 that exceeded Environmental Protection Agency standards; the National Park Service thus closed headquarters at the Kilauea summit for the day. On 7 December, SO2 emissions were 4,300 t/d.

Although visible activity within Pu`u `O`o crater remained diminished, visitors and nearby residents heard roaring sounds during 24 November-5 December. Tephra fell up to 10 km from the vents and included "Pele's hair" (thin strings of solidified lava ~2.5 cm in length). During 28-30 November, a particularly active period of tephra deposition occurred; the associated emission events were detected on seismic instruments near the Pu`u `O`o vent.

On 7 December the SW flank of Pu`u `O`o cone collapsed, creating a funnel-shaped pit ~50 m in diameter at the surface midway between the S base and rim. A small glowing hole on the floor of the pit revealed that the pit intersected the magma supply system underlying the cone and flank vents. The new collapse pit resembled the Great Pit that formed on the cone's W slope in early 1993 (BGVN 18:02 and 18:03); the Great Pit later enlarged, causing the cone's W wall to collapse in January 1997 (BGVN 22:01). Pits of this type form when Pu`u `O`o is undermined by magma feeding the on-going eruption.

Lava output inside Pu`u `O`o crater visibly increased during 7-8 December; flows from the crater vent filled the crater's E side. The increased activity may have been related to the formation of the new collapse pit.

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. Between January 1983 and December 1996 the volume of erupted lava totaled ~1.45 km3.

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

Information Contacts: Hawaiian Volcano Observatory (HVO), U.S. Geological Survey, PO Box 51, Hawaii 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) — November 1997 Citation iconCite this Report

Klyuchevskoy

Russia

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

All times are local (unless otherwise noted)


Elevated seismicity during 13 October-1 December; gas-and-steam plumes

During 13 October-29 December, seismicity under Kliuchevskoi was above background level. During 13 October- 2 November the activity occurred at depths of 20-30 km, but during 3-16 November, hypocenters were concentrated both near the summit crater and at depths of 25-30 km. Volcanic tremor recorded on 10-16 November was followed by tremor under the volcano and earthquake hypocenters 25-30 km deep during 17 November-14 December.

Gas-and-steam plumes rose 100 m above the crater on 18, 25, and 30 October, and on 1-2, 17-18, 23, and 28 November. A gas-and-steam plume rose 70 m above the summit crater on 6-7 November; by 8 November the plume rose 1 km above the crater and extended 5 km NW. By 9 November, the plume returned to a more typical height of 50-100 m. On 11-12 and 14-16 November, gas-and-steam plumes rose 100-200 m. During 2-6 December a gas-and- steam plume rose 300-1,000 m and extended 5-10 km SE to SW. On 7 December, a fumarolic plume rose less than 300 m above the summit crater. A gas-and-steam plume rose 300-700 m above the summit crater and extended 3-10 km NE and SW on 8-9 and 12 December. On 23, 24, and 28 December, a gas- and-steam plume rose 100-300 m and extended 3-5 km SE to SW. A fumarolic plume rose 2 km above the volcano on 25 December.

The level of concern was upgraded to yellow from green during 3-16 November, indicating that normal activity could possibly change into an eruption. During 17-23 November, although seismicity continued above background, the level of concern returned to green. On 1 December, the level of concern was again upgraded to yellow but returned to green as of 15 December.

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- Kamchatskiy 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.


Koryaksky (Russia) — November 1997 Citation iconCite this Report

Koryaksky

Russia

53.321°N, 158.712°E; summit elev. 3430 m

All times are local (unless otherwise noted)


Above-background seismicity in late December

Seismicity was at normal background levels from September 1996 through mid-December 1997; the period of normal activity began in July 1996 (BGVN 21:09). However, during 22-29 December, seismicity was reported above background level.

Geologic Background. The large symmetrical Koryaksky stratovolcano is the most prominent landmark of the NW-trending Avachinskaya volcano group, which towers above Kamchatka's largest city, Petropavlovsk. Erosion has produced a ribbed surface on the eastern flanks of the 3430-m-high volcano; the youngest lava flows are found on the upper W flank and below SE-flank cinder cones. Extensive Holocene lava fields on the western flank were primarily fed by summit vents; those on the SW flank originated from flank vents. Lahars associated with a period of lava effusion from south- and SW-flank fissure vents about 3900-3500 years ago reached Avacha Bay. Only a few moderate explosive eruptions have occurred during historical time, but no strong explosive eruptions have been documented during the Holocene. Koryaksky's first historical eruption, in 1895, also produced a lava flow.

Information Contacts: Vladimir Kirianov, Kamchatka Volcanic Eruptions Response Team (KVERT), Institute of Volcanic Geology and Geochemistry, Piip Ave. 9, Petropavlovsk- Kamchatskiy 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) — November 1997 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)


Increased eruptive activity at Crater 2

Since 20 October, increased activity was noticeable at Crater 2; emissions were thicker, occasional roaring or rumbling sounds were heard, and Vulcanian explosions produced dark black clouds that rose ~2 km above the crater. Occasional loud Vulcanian activity occurred throughout November. A bright fluctuating glow and occasional incandescent projections were visible during 15-25 November. Weak fumarolic vapor was released from Crater 3. Seismic levels remained moderate.

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: Patrice de Saint-Ours, RVO.


Long Valley (United States) — November 1997 Citation iconCite this Report

Long Valley

United States

37.7°N, 118.87°W; summit elev. 3390 m

All times are local (unless otherwise noted)


Summary of 1996 activity

This report summarizes 1996 activity (Hill, 1996). More recent activity will be presented in subsequent reports.

During early 1996, a series of small earthquake swarms occurred in the S moat of the caldera between Convict Lake moraine and the SE margin of the resurgent dome. Swarm activity in the area gradually increased in intensity during February-March 1996, culminating with an earthquake swarm during 29 March-10 April, the most energetic in the caldera since January 1983 (SEAN 07:12); the swarm included 24 earthquakes of M 3 or greater. On 30 March two M 4.0 events occurred; on 1 April there was a M 4.1 event, the largest in the sequence. Altogether the swarm included over 1,600 locatable earthquakes (M >0.5) and had a cumulative seismic moment of ~5 x 1022 dyne-cm, the equivalent of a single M 4.8 earthquake. Instruments showed no unusual ground deformation associated with the swarm.

Earthquake activity within the caldera gradually slowed following the 29 March-10 April swarm through the remainder of April and May. Activity increased again in June with four bursts of seismicity at 5-day intervals during 9-25 June. Swarms on 9, 14, and 25 June were located near the SW margin of the resurgent dome (figure 19), near the junction of Highways 203 and 395; the swarm on 19-20 June was located at the SE margin of the resurgent dome (~2 km N of the airport). The largest earthquakes in these swarms were a M 2.6 event on 9 June, M 3.2 and M 3.5 events on 14 June, and a M 3.3 event on 19 June. The long-base tiltmeter, centered 1 km SE of the 19-20 June swarm, showed a 0.3 µrad tilt down to the NW coincident with that swarm.

Figure (see Caption) Figure 19. Earthquake epicenters in the Long Valley region during 1996. Courtesy of USGS.

Small earthquake swarms on 30 July, and 7 and 9 August, were the last to occur within the caldera for the remainder of 1996; all were located near the SW margin of the resurgent dome. The caldera was relatively quiet during the last half of 1996 (figure 20), producing only occasional small earthquakes, all less than M 3.

Figure (see Caption) Figure 20. Daily number of earthquakes (M > 1.0) measured in 1996 at Long Valley Caldera. Courtesy of the USGS.

Occasional long-period volcanic earthquakes continued to occur during 1996 at depths of 10-20 km beneath the Devils Postpile area SW of Mammoth Mountain. These events have become more frequent since their 1989 onset during a swarm beneath Mammoth Mountain (SEAN14:06).  Minor volcano- tectonic earthquake activity in the shallow crust (<10 km depth) beneath Mammoth Mountain showed no significant change in rate or spatial distribution since 1989.

Long-term uplift and extensional deformation of the resurgent dome gradually slowed through the last half of 1996; this was defined by 2-color geodimeter measurements. The decrease in the resurgent dome's deformation rate and intra-caldera earthquake activity during the last half of 1996 was similar to the relative seismic quiescence and low deformation rates during 1984 to mid-1989. Continuous deformation monitoring showed no significant changes during 1996, with the exception of the 0.3 µrad tilt accompanying the 19-20 June earthquake swarm.

Dominant variations in carbon dioxide soil-gas concentrations in the tree-kill areas around Mammoth Mountain reflected the blanketing effect of snow during the winter months. Continuous CO2 monitors at Horseshoe Lake showed increased concentrations from early February through the end of April. Concentrations gradually returned to minimum values by mid-summer. The areas showing evidence of high CO2 soil-gas concentrations around the flank of Mammoth Mountain changed relatively slowly since 1991. In the late summer of 1995, there were seven areas of CO2-induced tree-kill scattered around the S, W, and N flanks of the mountain covering ~150 acres. A series of small collapse pits extending from the S-most tree-kill area at Horseshoe Lake merged with a crack in the bottom of Horseshoe Lake that was first detected in late September. Whether this system of shallow fractures is related to the anomalously high CO2 soil-gas concentration in the adjacent Horseshoe Lake tree-kill area has not been determined; however, the fracture system explained Horseshoe Lake's tendency to drain internally. A survey around Horseshoe Lake was planned in order to determine if the fracture system was associated with local deformation.

The 17 x 32 km Long Valley caldera lies E of the central Sierra Nevada, ~320 km E of San Francisco. The caldera formed ~730,000 years ago as a result of the Bishop Tuff eruption. Resurgent doming was followed by eruptions of rhyolite from the caldera moat and rhyodacite from the outer ring-fracture vents until ~50,000 years ago. Since then the caldera has remained thermally active, and in recent years has undergone significant deformation. Although distinct from Long Valley Caldera, both Inyo Craters and Mammoth Mountain are adjacent to it.

Reference. Hill, David P., 1996, Long Valley Caldera monitoring report (October- December 1996): U.S. Geological Survey, Volcano Hazards Program.

Geologic Background. The large 17 x 32 km Long Valley caldera east of the central Sierra Nevada Range formed as a result of the voluminous Bishop Tuff eruption about 760,000 years ago. Resurgent doming in the central part of the caldera occurred shortly afterwards, followed by rhyolitic eruptions from the caldera moat and the eruption of rhyodacite from outer ring fracture vents, ending about 50,000 years ago. During early resurgent doming the caldera was filled with a large lake that left strandlines on the caldera walls and the resurgent dome island; the lake eventually drained through the Owens River Gorge. The caldera remains thermally active, with many hot springs and fumaroles, and has had significant deformation, seismicity, and other unrest in recent years. The late-Pleistocene to Holocene Inyo Craters cut the NW topographic rim of the caldera, and along with Mammoth Mountain on the SW topographic rim, are west of the structural caldera and are chemically and tectonically distinct from the Long Valley magmatic system.

Information Contacts: David Hill, U.S. Geological Survey, MS 977, 345 Middlefield Rd., Menlo Park, CA 94025 USA (URL: https://volcanoes.usgs.gov/observatories/calvo/).


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

Manam

Papua New Guinea

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

All times are local (unless otherwise noted)


Moderate explosions in late November

Moderate activity dominated during November except for the last week, when Vulcanian explosions occurred at Main Crater. The mild level of activity at Main Crater that began in late August continued until mid- November. Beginning on 23 November, the crater released thicker white and gray emissions. Moderate Vulcanian explosions (~700 m above the crater) started on 27 November and produced fine ashfalls. South Crater noiselessly and gently released thin to thick white vapor; a weak steady glow was visible on most nights during November.

Instrumental observation revealed no significant change in seismicity (~1,200 to 1,400 low-frequency events/day of small amplitude). Steady radial inflation of 1 µrad was detected at the Tabele observatory (4 km SW).

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: Patrice de Saint-Ours, RVO.


Monowai (New Zealand) — November 1997 Citation iconCite this Report

Monowai

New Zealand

25.887°S, 177.188°W; summit elev. -132 m

All times are local (unless otherwise noted)


Inferred eruption during 15-18 December

A cluster of high-amplitude acoustic signals from Monowai was recorded during 15-17 December (figure 4). During the activity, 171 acoustic waves of varying duration were recorded. Of the waves, nine were interpreted as explosive, determined according to seismic signal characteristics. The explosive waves occurred during the first episode of heightened activity on 15 December. The signals indicated that an eruptive event stronger than those of September 1996 (BGVN 21:11) and April 1997 (BGVN 22:05) was occurring. However, infrared and visible GOES-9 imagery showed no evidence of near-surface activity.

Figure (see Caption) Figure 4. Acoustic signals from Monowai Seamount during 13-18 December. Courtesy of O. Hyvernaud.

Three small acoustic waves on 12 and 14 December preceded the heightened activity. The first high- amplitude acoustic wave was generated at 2330 GMT on 14 December; the last was generated at 2021 GMT on 17 December. The acoustic activity stopped suddenly after a sequence of weak, very long acoustic waves. The strongest wave, generated at 0021 GMT on 16 December, had a peak-to-peak amplitude of 0.46 mm/s but was not explosive.

Monowai Seamount lies midway between the Kermadec and Tonga Islands, ~1,400 km NE of New Zealand. The adjacent trench is significantly shallower (~4 km) than the Tonga and Kermadec trenches (9-11 km deep). A T-wave swarm was detected in November 1995 (BGVN 20:11/12). Other noteworthy recent activity at Monowai included a possible eruption in 1944, and about seven documented eruptions during 1977-90 (BGVN 16:03).

Geologic Background. Monowai, also known as Orion seamount, rises to within 100 m of the sea surface about halfway between the Kermadec and Tonga island groups. The volcano lies at the southern end of the Tonga Ridge and is slightly offset from the Kermadec volcanoes. Small parasitic cones occur on the N and W flanks of the basaltic submarine volcano, which rises from a depth of about 1500 m and was named for one of the New Zealand Navy bathymetric survey ships that documented its morphology. A large 8.5 x 11 km wide submarine caldera with a depth of more than 1500 m lies to the NNE. Numerous eruptions from Monowai have been detected from submarine acoustic signals since it was first recognized as a volcano in 1977. A shoal that had been reported in 1944 may have been a pumice raft or water disturbance due to degassing. Surface observations have included water discoloration, vigorous gas bubbling, and areas of upwelling water, sometimes accompanied by rumbling noises.

Information Contacts: Olivier Hyvernaud, BP 640, Laboratoire de Geophysique, Papeete, Tahiti, French Polynesia.


Obituary Notices (Unknown) — November 1997 Citation iconCite this Report

Obituary Notices

Unknown

Unknown, Unknown; summit elev. m

All times are local (unless otherwise noted)


Death of Werner F. Giggenbach at Rabaul

We are saddened to report that Dr. Werner F. Giggenbach died on 7 November 1997 while conducting field research at Rabaul volcano. He was a Senior Scientist with the Institute of Geological and Nuclear Sciences, Lower Hutt, New Zealand, and was nearing his 60th birthday. Werner was a leading geochemist in the study of volcanic and geothermal systems, and developed many of the techniques used to sample volcanic gases and geothermal fluids in the field and to analyze them in the laboratory. The international standard bottle for collecting volcanic gases is called the Giggenbach bottle. Moreover, he was known and respected for his integrated physical and geochemical models of how volcanic and geothermal systems work. He assisted New Zealand and more than a dozen other countries in developing their geothermal energy potential. During his career Werner contributed reports to the GVN Bulletin concerning White Island, Rumble III, Raoul Island, Ngauruhoe, Erebus, and Lonquimay. He left the world a legacy of exceptionally innovative and practical contributions to the volcanological and geothermal sciences, and will be deeply missed.

Geologic Background. Obituary notices for volcanologists are sometimes written when scientists are killed during an eruption or have had a special relationship with the Global Volcanism Program.

Information Contacts:


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

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


June-November earthquakes; thermally stable fumaroles

This report focuses on June-November 1997 but includes histograms of monthly earthquake counts for the period January-November (figures 65 and 66). On these plots, earthquakes are grouped into three frequencies. ... Tremor was absent at Poás during November 1996 through October 1997; during November 1997 tremor prevailed for 22 hours. The previous high was in October 1996 (28 hours).

Figure (see Caption) Figure 65. Monthly count of low-frequency earthquakes (
Figure (see Caption) Figure 66. Monthly counts of medium- and high-frequency earthquakes detected at Poás during January-November 1997. Courtesy of OVSICORI-UNA.

Compared to its level in May, the lake surface in the northernmost crater rose during June-November. The greenish-turquoise lake's temperatures were as follows: June, 32°C; July, 31°C; September, 35°C; October, 34°C; November, 35°C. Deformation measurements in June disclosed no significant change.

During June-November a fumarole on the N terrace had a temperature of 91-92°C; sulfur was deposited at this fumarole even though gas emissions appeared low. During June-July, and again in October, colorless gas columns were conspicuous above the pyroclastic cone in the crater's center; the columns rose 300 m above the crater floor. Later, during September and November, these columns rose ~400 m. During June-September, escaping steam made a loud noise that was audible from the crater rim; during June-November, at a point where scientists could gain access, the steam's temperature remained at 92-93°C.

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

Information Contacts: E. Fernandez, R. Van der Laat, F. de Obaldia, T. Marino, V. Barboza, W. Jimenez, R. Saenz, E. Duarte, M. Martinez, E. Hernandez, and F. Vega, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA).


Popocatepetl (Mexico) — November 1997 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Low activity through November; lava extrusion and explosion in December

Low levels of eruptive and seismic activity characterized Popocatépetl through most of November. Typically, a few events occurred each day, including short episodes of low-amplitude harmonic tremor and gas- and-steam venting in plumes that drifted to the NE or SE. Tiltmeters showed little variation in November but indicated a slight increasing trend. Bad weather and poor visibility occurred frequently.

Table 9 lists type-A seismic events recorded during November. Two episodes of harmonic tremor were recorded on 1 November. A 2 November lightning strike disabled video monitoring until the 5th. Poor weather impeded observation on 11-12 November during a slight increase in activity. On 15 November, a slight increase in the number of events was accompanied by minor ash emission. Some ash was also emitted in conjunction with seismic events on 21 November.

Table 9. Type-A seismic events recorded at Popocatépetl in November 1997. Courtesy of CENAPRED.

Date Time Magnitude Depth (km) Flank
01 Nov 1997 0250 2.0 4.0 --
01 Nov 1997 0311 2.1 10.2 NE
01 Nov 1997 1849 2.8 6.1 SE
02 Nov 1997 1600 2.1 2.8 S
04 Nov 1997 0019 2.1 5.4 SE
04 Nov 1997 0036 2.2 5.5 --
05 Nov 1997 1538 1.9 6.0 NE
06 Nov 1997 0001 2.5 5.5 --
08 Nov 1997 1255 1.7 6.6 --
10 Nov 1997 1420 2.2 6.6 NE
22 Nov 1997 2204 2.3 2.1 SE
25 Nov 1997 0457 2.4 4.9 --
25 Nov 1997 0826 2.6 5.0 --
25 Nov 1997 0837 2.4 2.4 SE
26 Nov 1997 1517 2.9 3.6 N

On 24 November, seismic and associated eruptive activity began to increase. Thirty-six low- to moderate- intensity seismic events were recorded, including significant exhalations at 0823, 0829, 0857, and 0953; during these events, ash plumes rose to 1 km and drifted NE. Low-amplitude harmonic tremor 3-5 minutes in duration occurred in the afternoon. On 25 November, 42 seismic events were recorded; some were accompanied by ash emissions and periods of tremor lasting 2-8 minutes. No significant deformation was observed. During a 25 November helicopter flight, increased gas and steam from fumaroles obstructed views of the crater and dome. By 27 November, activity was subsiding; 29 seismic events and tremor 2-3 minutes long were recorded. Levels of seismic activity continued to decline until the end of the month.

The last of several flow-detection monitoring stations (BGVN 22:10) was installed on 7 November; also, a temporary high-gain broad-band seismograph was installed at the Canario station to study the N flank in more detail. The Canario station's instrumentation included a triaxial short-period seismograph, a triaxial broad-band seismograph, a digital inclinometer, a flow detector, and a rain gage. To reinforce the seismic and geodetic monitoring system, a new station was installed on 28 November on the W flank just under Ventorrillo peak near the Nexpayantla ravine at 4,452 m elevation. The instrumentation includes a triaxial short- period seismograph and a biaxial tiltmeter.

Two important eruption episodes highlighted activity in December. Both eruptions involved extrusion of lava into the crater, creating a dome that sealed fumaroles.

Small- and moderate-intensity emissions of gas and steam characterized activity at the volcano for most of December. Small type-A tectonic events occurred regularly along with incidents of tremor. The first increase in activity began 5 December with 15 small gas-and-steam emissions, tremor of 90 minutes duration beginning at 1335, and two type-A seismic events in the late afternoon. At 0315 on 6 December activity increased considerably and continued throughout the day. A moderately large high-frequency tremor accompanied by continuous gas, steam, and ash exhalations lasted until 1700. Early in the morning of the 6th a faint glow at the fumarole was observed through the video monitor, indicating the presence of incandescent material in the crater interior. In the late afternoon the gas emission abruptly stopped, possibly due to obstructions of the vents. Observers speculated that these phenomena indicated the extrusion of new lava in the bottom of the crater. No significant changes of the other measured parameters could be observed.

The following day saw a considerable decrease in activity: only six moderate emissions including some short ash puffs. Continuing very low emissions over several days indicated the vents were partially closed. On the morning of 9 December personnel from CENAPRED and the Instituto de Geof¡sica, UNAM, made a helicopter overflight during which the presence of a large lava dome, spread across almost over the entire crater floor, was seen. This observation confirmed the assumption of a new lava extrusion on 5-6 December. No important changes on the volcano flanks or the glacier could be observed. SO2 measurements made the afternoon of 9 December gave preliminary values of 6,100 tons/day. The other parameters that are continuously monitored showed little variation. Popocatépetl returned to characteristic low levels of activity, although some earthquakes of M 2.2 occurred at a depth of ~4.7 km during 14-15 December. On 13 December strong winds and low temperatures caused damage to monitoring equipment, including the video transmission link.

After several weeks of very low activity an eruption clearly observed from neighboring towns started at 1930 on 24 December. The activity began with a 2-minute explosion followed by 15 smaller volcano-tectonic events and several moderate emissions. According to reports from the nearby towns of San Nicolas de los Ranchos and Amecameca, during the first event observed brightness around the summit was produced by the expulsion of incandescent materials, and an associated shock wave was felt. From Puebla grass fires were reported on the E flank of the volcano. Ashfalls were reported starting at 2045 in towns E of the volcano (Atlixco, Calpan, and San Nicolas de los Ranchos). The whole episode lasted a total of 30 minutes. All monitored parameters except for seismicity then returned to normal levels. This eruption was probably associated with the reopening of conduits inside the crater, obstructed since 6 December by lava extrusion. This obstruction was carefully monitored because pressurization of the system raised the possibility of explosive events. Following the eruption of 24 December activity returned to very low, stable levels for the remainder of the month. The volcanic- alert system remained on "yellow" (caution) through all of December.

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

Information Contacts: Roberto Meli, Roberto Quaas Weppen, Alejandro Mirano, Bertha López Najera, Alicia Martinez Bringas, A. Montalvo, G. Fregoso, and F. Galicia, Centro Nacional de Prevencion de Desastres (CENAPRED); J.L. Macias, Instituto de Geofisica, UNAM, Circuito Cientifico.


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

Rabaul

Papua New Guinea

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

All times are local (unless otherwise noted)


Slow ongoing inflation

Slow caldera inflation continued throughout November. Weak emissions of white vapor were produced by Tavurvur cone. The volume of emissions increased at the end of the month in response to rainfall. On 26 November, weak night glow was visible and a brief rumbling sound was heard.

Slow, ongoing inflation has occurred since the last significant lava-producing eruption at Tavurvur on 14 March (BGVN 22:03), despite subsequent minor Strombolian and Vulcanian eruptions on 12 April, 1 June, 11 July, and 17 August (BGVN 22:04, 22:05, 22:07, and 22:08). The inflation mainly affected areas within ~3 km of Tavurvur and the Greet Harbour shallow magma reservoir. Maximum rates of tilt were no more than 4 µrad /month; maximum monthly uplift was no more than 1 cm.

One high-frequency event from the NW was recorded on 14 November; no low-frequency events occurred during the month. SO2 output measured by COSPEC decreased in mid-November from ~800 to ~300 tons/day. Soil CO2 flux, monitored at 14 locations around the bay, was relatively low (<=200 mg/(m2 day)).

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: Patrice de Saint-Ours, Rabaul Volcano Observatory, P.O. Box 386, Rabaul, Papua New Guinea.


Sheveluch (Russia) — November 1997 Citation iconCite this Report

Sheveluch

Russia

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

All times are local (unless otherwise noted)


Normal seismicity and fumarolic activity

Background seismicity prevailed during 13 October-29 December. Normal fumarolic activity was seen during 30 October-2 November and 6-7 November. No fumarolic activity was observed during 10 November-14 December. For the period 15-29 December, Shiveluch was usually obscured by clouds; however, on 22 December, a gas-and-steam plume rising 100 m above the volcano was seen.

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- Kamchatskiy 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) — November 1997 Citation iconCite this Report

Soufriere Hills

United Kingdom

16.72°N, 62.18°W; summit elev. 915 m

All times are local (unless otherwise noted)


Explosions and dome growth

The following summarizes Scientific Reports of the Montserrat Volcano Observatory (MVO) during 12 October-23 November 1997.

General. During September, activity was dominated by collapses with simultaneous pyroclastic flows down ghauts (BGVN 22:10). Particular events differed in magnitude, column height, or pyroclastic runout, possibly due to time elapsed between events. During 12-21 October, 29 explosions were recorded for a total of 61 since the latest episode began on 28 September. After the last explosion on 21 October, a new dome was seen in the crater, extruding at a rate of up to 8 m3/s. The new dome grew during the following week on the S side, weakening the crater wall on the Galway's side (figure 33) and creating two large vertical cracks on the outside of the wall by 2 November. Further growth in the weakened area led to a 4 November collapse, which removed much of the pre-explosion dome complex material. A subsequent collapse on the 6th removed a significant portion of the new dome and old material. Pyroclastic flows from these collapses reached the sea and a fan deposit at the mouth of White River was significantly extended. Dome growth coincided with large swarms of hybrid earthquakes. After the 6 November collapse, the swarms subsided yet seismicity remained relatively high. Low levels of eruptive activity prevailed for the rest of November. Although bad weather limited observation of the dome, the lobe in the Galway's area was seen as the focus of growth during 9-23 November but at a slower rate. Seismicity included rockfall signals and small-amplitude hybrid earthquakes.

Figure (see Caption) Figure 33. Map of Montserrat showing selected towns and features around the Soufriere Hills volcano.

Visual observations. Vulcanian explosions up to 21 October resulted in pyroclastic flows into surrounding ghauts. Intervals between explosions averaged 8.5 hours with a range of 2.75 to 20.5 hours. During 14-16 October, 12 explosions occurred; intervals between single events lengthened towards the end of the period. Three vigorous explosions on 20-21 October sent plumes to 9,100 m, pumice to Salem and Olveston, and ash to the N. Pumice from Cork's Hill measured up to 10 cm in diameter and ballistics fell 2 km N from the vent. Pyroclastic flows were generally radial for larger explosions; however, the N ghauts were preferred routes because the crater is open to the N. Some flows had relatively small runouts (<1 km) in only one or two ghauts. Pyroclastic flows over the past month have left thin (0.3-1 m) deposits on all flanks, accumulating and infilling the topography. Fort Ghaut in Plymouth and Mosquito Ghaut were completely filled, and Tuitt's and White's Ghauts were partially filled, resulting in fans advancing into towns. Gage's Soufriere was significantly filled with material stacked in front of St. George's hill.

A new dome was first recorded as an incandescence inside the scar during the evening of 22 October. The next day, fresh lava overspilled the tephra rampart between the scar and crater and, by 25 October, occupied a substantial portion of the scar. The lava appeared to be blocky, coarse material, which, due to oxidation at the top of the conduit, is darker than normal (similar to last October; BGVN 21:10). By 25 October the dome's peak had risen to 910 m, 40 m below the crater rim. Growth to the N and vertical infilling of the scar caused rockfalls that traveled a few hundred meters down Tuitt's Ghaut; however, rockfalls were few in number considering the rate and blockiness of the extrusion as well as the steepness of the ghaut. Dome growth continued over the next few weeks with vigorous ash-and-steam venting. Rockfalls from the new dome and old crater coincided with hybrid earthquake swarms.

An overflight on 2 November revealed two large vertical cracks on the Galway's side of the crater; by the next day, these had evolved to deep gullies. Rockfalls on the dome's S side occurred on the morning of 4 November. At 1206 on 4 November, a wide section of the crater in the Galway's area collapsed and caused an hour of pyroclastic flows. Some of the flows reached the sea at O'Garra's and formed a delta. Ash clouds rose to 3000 m. The collapse removed a large part of the old dome but left the 22 October dome mostly intact. Observations on 6 November included two distinct lobes of the new dome separated by a small crater venting ash; the N lobe remained at its 2 November height of 937 m while the S lobe grew. Following 18 hours of high- amplitude tremor a second collapse in the Galway's area began at 1430 on 6 November and lasted 35 minutes. More material was removed than in the previous collapse, rockfalls occurred in Tar River valley and Gage's areas, and an ash plume reaching 4,500 m drifted W.

After a few days of poor visibility, growth of the new dome in the collapse area was revealed. A fin-shaped lobe had grown almost vertically in the old crater wall position; it had a coarse, blocky outer face but a smooth appearance on the inner surface where it extruded out of a cleft in the dome center that exhibited vigorous degassing and venting of ash. The distinct N and S lobes divided by a central cleft or vent were similar to earlier structures (BGVN 21:08 and 22:05), although in this case the N lobe extruded first to reach a certain size then relaxed while growth shifted to the S lobe; this in turn lead to a catastrophic collapse of the old crater wall. Overflight observation on 11 November showed that the S lobe had doubled in size in 3 days to fill the collapse scar of 4-6 November; however, it was extruding at a slower rate. Ash and steam continued to vent from the central cleft. Ash clouds rose to 1800 m drifting W and fell out over Plymouth. Rockfall spalling off the S lobe eroded chutes S of the dome and accumulated in thick deposits in Galway's Soufriere.

Seismicity. Figures 34, 35, and 36 show seismicity during 12 October-23 November. The sequence that began on 22 September (BGVN 22:10) continued until 21 October. Seventy-six explosions at intervals of 3-34 hours were recorded. The explosions appeared as 1-Hz signals of varying relative amplitude and were followed by pyroclastic-flow signals; long-period energy continued through the flow duration and persisted as lower-amplitude tremor of 0.5 to 3 hours duration. Signals coincided with ash venting but there was little or no precursor activity.

Figure (see Caption) Figure 34. Daily events at Soufriere Hills triggering the broadband network system, 12 October-23 November 1997. Event counts are from 1600 on the previous day to 1600 on the date indicated. Data courtesy of MVO.
Figure (see Caption) Figure 35. Seismic swarms at Soufriere Hills during 20 October-13 November 1997. Data courtesy of MVO.
Figure (see Caption) Figure 36. Explosions from Soufriere Hills measured at the Windy Hill broadband station during 12-23 October 1997. Amplitudes are peak-to-peak in counts. Data courtesy of MVO.

The second explosion of 20 October and the first of 21 October were accompanied by swarms of hybrid and volcano-tectonic earthquakes. The second explosion of 21 October initiated 24 hours of hybrid and volcano- tectonic earthquakes and rockfalls down Tuitt's ghaut before ending in a long, sparse swarm on 23 October, although a high level of long-period earthquakes lingered thereafter. Volcano-tectonic earthquakes typically occurred 2-4 km from the top of the dome.

During late October and early November, intense swarms sometimes merged with tremor having frequencies similar to individual hybrids. Hybrid swarms during 1-2 November produced the highest amplitudes since 24 June, reported from stations in Antigua, Dominica, and Nevis. Large pyroclastic-flow signals were recorded on 4 and 6 November. During 6-8 November, particularly high levels of tremor occurred. Individual hybrids were detected on paper but not on the networks due to high background noise; thus low numbers of events did not reflect low activity. Tremor and hybrids were associated with ash venting at the dome. Small pyroclastic flows were recorded on 9 November, but otherwise hybrid earthquakes did not generate external activity. Amplitudes became progressively smaller later in November; from 14 November to the end of the month, rockfall signals dominated, although a significant number of low-amplitude hybrids not grouped in swarms occurred but were not detected by the network.

Ground deformation. On 20 October, a GPS survey was taken; however, the only sites accessible were White's, Harris, and Windy Hill due to thick ash cover. Measurement from Harris to White's showed a 2-cm increase since 20 September, closer to the pre-June 1997 level. Although less than two standard deviations below the mean, this single measurement did not indicate an acceleration in deformation. The line from Harris to Windy Hill showed slight shortening since 12 August. EDM measurements to Lee's Yard from MVO on 14 October revealed an increase of 1 cm since July.

Volume measurements. Gross morphology of the pre-21 September dome was unchanged since the collapse on that day (BGVN 22:10) until 22 October with some exceptions (see Visual observations). The volume of the 22 October dome was measured by geometric calculation until a survey was taken. Assuming the dome completely filled the explosion crater by 23 October (when overspilling was observed), the volume was approximately 1.7 x 106 m3 resulting in an extrusion rate of 8-10 m3/s, depending on the time of first appearance. A detailed survey was made on 6 November, before the collapse, from several points; theodolite points from Jackboy Hill, Center Hills, and Flemings, a GPS point at Center Hills (to be used in future surveys as an additional static photo point), and helicopter survey photographs of most areas around the dome except the Galway's side. Good coverage of the N lobe of the 22 October dome was obtained. Since this area had not changed since 3 November, the volume was calculated at 5 x 106 m3. Collapse volumes were calculated separately for an average extrusion rate of 5 m3/s over the first 11 days of the "22 October" dome growth. Visual observation revealed that the 4 November collapse involved less material than the 6 November collapse. The latest estimates of collapse volumes were 1.8 x 106 m3 from 4 November and 3.4 x 106 m3 from 6 November. The bulk of the collapse material was deposited in fans at the end of valleys that will be surveyed when the ash subsides. A 17 November survey of the White River valley fan revealed total deposits of 13.6 x 106 m3, an increase of 5.5 x 106 m3 since 15 May, resulting mostly from the 4 and 6 November collapses. The survey did not include recent deposits in the upper valley still covered in ash.

Environmental monitoring. Dust Trak sampling to measure airborne particulates was carried out at four fixed sites. The values at the fixed sites were low (3) during 12 October-23 November, except for the Catholic school site, which sometimes recorded elevated levels (0.05-0.1 mg/m3). This effect is caused by the large amount of human activity at this site and its location near a main road. Towards the end of this reporting period the three sites (not including the school) all had remarkably similar average concentrations each day. A new Dust Trak site was established at Mango Drive in Woodlands on 16 November to replace the Runaway site.

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

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


Vulcano (Italy) — November 1997 Citation iconCite this Report

Vulcano

Italy

38.404°N, 14.962°E; summit elev. 500 m

All times are local (unless otherwise noted)


Trends in fumarolic gas composition during 1996-97

Periodic observations of the chemical composition of fumarolic gases have been made at Vulcano since 1977. Several fumaroles with different temperatures but similar chemical compositions were observed. Differing trends in fumarolic gas composition at different locations on Vulcano have been observed during 1996-97.

Table 5 shows the trend in chemical composition of gases emitted by fumaroles on the rim and inside the crater during 1996-97. For fumaroles on the rim, percentages of typical magmatic species such as SO2, H2, and CO increased during 1996-97; percentages decreased for fumaroles inside the crater. Scientists estimated that the magmatic system was opening on the rim and closing inside the crater. This evolution pattern revealed that the stability of the system was affected by deformation of the Fossa cone produced by increased vapor pressures at depth.

Table 5. Fumarolic gas composition (percentages) on the rim (A) and inside the crater (B) of Vulcano, 1996-97. Courtesy of M. Martini.

Component A (rim) 1996 A (rim) 1997 B (crater) 1996 B (crater) 1997
Temperature 348°C 328°C 399°C 426°C
H2O (vol.) 84.41 88.86 81.50 85.38
CO2 (dry) 93.90 92.37 97.40 97.13
H2S 2.66 3.10 0.41 0.40
SO2 1.46 2.11 1.11 0.99
HCl 0.97 1.26 0.54 0.78
HF 0.52 0.46 0.077 0.029
B 0.017 0.023 0.014 0.017
NH4 0.010 0.010 0.006 0.017
H2 0.041 0.121 0.081 0.048
N2 0.525 0.547 0.580 0.513
CO 0.00047 0.00072 0.0038 0.0024

Correction: Boris Behncke (Istituto di Geologia e Geofisica at Università di Catania) noted that during a visit in late April 1997 (BGVN 22:07) steam emissions from the Fossa Grande crater appeared slightly more voluminous than during visits in 1995 and 1996. This statement may have created a false impression of renewed increase in fumarolic activity when it was actually due to the relative humidity of the air. Fieldwork by other scientists during spring 1997 revealed low fumarole temperatures and less abundant emissions. This was confirmed by Behncke during June-July and 10-12 October when fumarolic emissions were the lowest since 1989.

Geologic Background. The word volcano is derived from Vulcano stratovolcano in Italy's Aeolian Islands. Vulcano was constructed during six stages during the past 136,000 years. Two overlapping calderas, the 2.5-km-wide Caldera del Piano on the SE and the 4-km-wide Caldera della Fossa on the NW, were formed at about 100,000 and 24,000-15,000 years ago, respectively, and volcanism has migrated to the north over time. La Fossa cone, active throughout the Holocene and the location of most of the historical eruptions, occupies the 3-km-wide Caldera della Fossa at the NW end of the elongated 3 x 7 km island. The Vulcanello lava platform forms a low, roughly circular peninsula on the northern tip of Vulcano that was formed as an island beginning in 183 BCE and was connected to Vulcano in about 1550 CE. Vulcanello is capped by three pyroclastic cones and was active intermittently until the 16th century. The latest eruption from Vulcano consisted of explosive activity from the Fossa cone from 1898 to 1900.

Information Contacts: Marino Martini, Dipartimento di Scienze della Terra, Università di Firenze, Via La Pira 4, 50125, Firenze, Italy; Boris Behncke, Istituto di Geologia e Geofisica, Universitá di Catania, Corso Italia 55, 95129 Catania, Italy.


Yasur (Vanuatu) — November 1997 Citation iconCite this Report

Yasur

Vanuatu

19.532°S, 169.447°E; summit elev. 361 m

All times are local (unless otherwise noted)


Strombolian eruptions; decreasing seismic activity since March 1997

ORSTOM reported in late November that there has been little change in the appearance of Yasur's crater since February 1997. During this interval only craters B and C (figure 11) were active; crater A was quiet. Crater B produced a few explosions and small ash plumes; occasionally small lava bombs (a few tens of centimeter in diameter) reached the lip of the crater.

Figure (see Caption) Figure 11. Sketch of the summit crater area at Yasur. Labels A, B, and C correspond to named craters. The sketch was based on photographs taken on 28 February 1997. Drawn by Alfreda Mabonlala; provided courtesy of P. Gineste, ORSTOM.

Seismic signals in 1997 (figure 12), with frequencies of 1-7 Hz, were related to Strombolian explosions and correlated with surface phenomena (Nabyl and others, 1997). All signals were recorded 2 km from the crater (figure 13), relayed to an ARGOS satellite, and then to the receiving station. Regional seismicity accounted for a small percentage of signals and thus had negligible effect on event counts.

Figure (see Caption) Figure 12. Daily seismicity and smoothed average seismicity recorded at Yasur during January through early November 1997. The solid line depicts smoothed averages of 25 recording periods; the averages were made to the number of events with vertical displacements reaching over 12 µm. The histogram shows the number of events with vertical displacements over 60 µm; these stronger events were absent during October and early November 1997. Such quiet intervals were common during early 1996 and much of 1995. Courtesy of ORSTOM.
Figure (see Caption) Figure 13. The ARGOS-linked monitoring station with Yasur to the N in the background, 2 November 1997. Courtesy of Pascal Gineste, ORSTOM.

Continuous seismic monitoring since March 1997 (figure 12) revealed a general decrease in Strombolian activity over time. Still, some powerful explosions were recorded during August 1997 (BGVN 22:08). These powerful events occurred only a few times per day and had vertical displacements greater than 60 µm; their scarcity was taken as a further indication of decreased activity. Since October 1993, seismic monitors recorded periods of high activity during December 1993-March 1995 and during May 1996-April 1997; slightly elevated activity occurred during August-October 1995. It was also reported by ORSTOM that an undisclosed radiometric technique suggested that fresh magma entered the system in May 1996.

During 29 July-4 August 1997 a team from the Soci't' de Volcanologie GenŠve (SVG) visited Yasur and made visual and other observations, including some temperature estimates of lavas using an optical pyrometer. The team saw small but almost continuous Strombolian activity in the N vents area. The continuous activity was interrupted by stronger explosions every 1-1.5 hours; the explosions threw lava fragments in all directions. The fragments fell mainly inside the crater but sometimes fell on the NE part of the outside rim; in one instance, a bomb ~1 m in diameter was found still hot on the rim. The stronger phases of the eruption were accompanied by ground vibrations. Small convulsing ash clouds sometimes issued from another part of the vent area, indicating that at least two separate vents were active.

At the S vents area, the SVG team observed gas, ash, and old material suddenly and noisily emitting from different vents during the beginning of their visit; a few to no red lava fragments were projected during these emissions. The activity sounded like a jet engine and caused gases to ignite. Towards the end of their visit, the team observed that the quantity of ash emitted had increased; the eruptions created ash clouds that were easily seen from the volcano's foot.

The SVG team measured temperatures with an infrared (1.55 µm wavelength) optical pyrometer (Optix-G, Keller GMBH., Ibbenburen-Lagenbeck). At an opening in the N vents area, a maximum temperature of 581°C was obtained on a weakly incandescent area. Strong degassing was present around the target at the time of the measurement (2 August).

Figure (see Caption) Figure 14. Photograph of Yasur looking N on 2 November 1997. Courtesy of Pascal Gineste, ORSTOM.
Figure (see Caption) Figure 15. Photograph looking N towards Yasur with a dry lake bed in the foreground, 2 November 1997. In 1975 there was a landslide of 50,000 m3 of material, leaving a detachment scar 100 m wide that can be seen in this photo. Courtesy of Pascal Gineste, ORSTOM.
Figure (see Caption) Figure 16. Photograph looking S at the crater rim of Yasur during a period of quiet activity, 2 November 1997. Courtesy of Pascal Gineste, ORSTOM.

Reference. Nabyl, A., J. Dorel, and M. Lardy, 1997, A comparative study of low frequency seismic signals recorded at Stromboli (Italy) and Yasur (Vanuatu), New Zealand Journal of Geol. and Geophys. (December issue).

Geologic Background. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and Vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Located at the SE tip of Tanna Island, this mostly unvegetated pyroclastic cone has a nearly circular, 400-m-wide summit crater. The active cone is largely contained within the small Yenkahe caldera, and is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. The Yenkahe horst is located within the Siwi ring fracture, a 4-km-wide, horseshoe-shaped caldera associated with eruption of the andesitic Siwi pyroclastic sequence. Active tectonism along the Yenkahe horst accompanying eruptions has raised Port Resolution harbor more than 20 m during the past century.

Information Contacts: M. Lardy, D. Charley, and P. Gineste, Centre ORSTOM, BP 76, Port Vila, Vanuatu, and Départment des Mines et de la Géologie et des Resources en Eaux; J. Tabbagh, Centre de Téléobservation Informatisé des Volcans, CNRS-CRG, Garchy, France; A. Nabyl and J. Dorel, OPG, Centre de recherches volcaniques (CRV), Clermont Ferrand, France; Mf. le Cloarec, Centre des faibles radioactivités CFR, Gif sur Yvette, France; P. Vetch and S. Haefeli, Société de Volcanologie Genève (SVG), C.P. 298, CH-1225, Chene-bourg, Switzerland.

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