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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 19, Number 07 (July 1994)

Managing Editor: Richard Wunderman

Aira (Japan)

Volcanism continues; 14 explosive eruptions

Arenal (Costa Rica)

Continued gas and lava emissions; sporadic Strombolian eruptions

Asosan (Japan)

Crater 1 at Nakadake still restless

Batur (Indonesia)

First significant eruptive activity in 18 years leads to ashfall 6 km WSW of the summit

Cumbal (Colombia)

Increased fumarolic activity

Etna (Italy)

Explosive degassing from La Voragine; fumarole temperatures reported

Galeras (Colombia)

Seismicity remains low; crater described and fumarole temperatures reported

Gamalama (Indonesia)

Eruptions generate ash cloud to ~5 km altitude and cause ashfall

Huila, Nevado del (Colombia)

Description of the Paez earthquake's mass wasting

Ijen (Indonesia)

Minor phreatic eruption in February described

Kanaga (United States)

Steam-and-ash plume rises 4,500 m; enlarged hot spot on imagery

Kilauea (United States)

Bench collapses and littoral explosions occur as lava flows continue to enter the ocean

Krakatau (Indonesia)

Frequent ash explosions (300-450/day) reach heights up to 500 m

Langila (Papua New Guinea)

Thick ash clouds from Crater 2 accompanied by explosion sounds

Lascar (Chile)

Moderate short-lived eruption sends plume over Argentina

Manam (Papua New Guinea)

Explosions on 5-7 July generate ash clouds and eject lava fragments

Marapi (Indonesia)

Eruption sends ash column to ~6 km above sea level; summary of 1993 activity

Masaya (Nicaragua)

Sulfur-rich plume and incandescent ejections from opening in lava lake

Merapi (Indonesia)

Increased deformation precedes a nuee ardente

Momotombo (Nicaragua)

Summit fumarole temperatures range from 238 to 655°C

Nyamuragira (DR Congo)

High lava fountains feed lava flow on NW flank

Nyiragongo (DR Congo)

Lava lake activity produces strong red glow above crater

Poas (Costa Rica)

Ashfall SW of the summit covers 56 km2

Rabaul (Papua New Guinea)

Seismicity remains low; minor subsidence

Ruapehu (New Zealand)

Relatively stable with water cooling of Crater Lake

Semeru (Indonesia)

Small ash eruptions to 500 m above the summit

Telica (Nicaragua)

Explosive eruption causes ashfall >12 km SW of the summit

Ulawun (Papua New Guinea)

White vapor emissions and low-frequency tremor

Unzendake (Japan)

Lava lobe 13 grows endogenously but then nearly stops growing in late-July

Whakaari/White Island (New Zealand)

No eruptive activity, but new shifts in leveling and magnetic data



Aira (Japan) — July 1994 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Volcanism continues; 14 explosive eruptions

Sakura-jima generated 22 eruptions in July, including 14 explosive ones. None of them caused damage. The highest plume rose to 2.2 km (at 1859 on 5 July). In July, the amount of ashfall at [KLMO] was 237 g/m3. Volcanic swarms were absent in July but 520 earthquakes were detected at a seismic station 2.3 km NW of Minami-dake crater.

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

Information Contacts: JMA.


Arenal (Costa Rica) — July 1994 Citation iconCite this Report

Arenal

Costa Rica

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

All times are local (unless otherwise noted)


Continued gas and lava emissions; sporadic Strombolian eruptions

At . . . Crater C, July marked another month of continued gas and lava emissions, and sporadic Strombolian eruptions. During July, the lava flow that began at the end of April continued to erupt and flow down an established channel. During 23 days in July, seismic station VACR (2.7 km NE of crater C) recorded an average of 18 events/day. These were interspersed with days having very low seismicity and tremor. Beginning on 23 July, Strombolian-type eruptions became common, and during 23-30 July they were seen 52 times. In some cases these eruptions were accompanied by sounds similar to a jet or steam engine. On 28 July tremor reached an amplitude of 27 mm at a frequency below 2.5 Hz.

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

Information Contacts: E. Fernández, J. Barquero, V. Barboza, R. Van der Laat, F. de Obaldia, and T. Marino, OVSICORI; G. Soto, G. Alvarado, and F. Arias, ICE; M. Mora, C. Ramirez, and G. Peraldo, Univ de Costa Rica.


Asosan (Japan) — July 1994 Citation iconCite this Report

Asosan

Japan

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

All times are local (unless otherwise noted)


Crater 1 at Nakadake still restless

Crater 1 remained restless through July, but the intensity of activity became more moderate compared to the last two months. Through July the average amplitude of continuous tremor was around 0.1 µm.

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: JMA.


Batur (Indonesia) — July 1994 Citation iconCite this Report

Batur

Indonesia

8.242°S, 115.375°E; summit elev. 1717 m

All times are local (unless otherwise noted)


First significant eruptive activity in 18 years leads to ashfall 6 km WSW of the summit

Beginning on 4 August, the daily number of A-type volcanic earthquakes increased to 14; two days later 125 events were registered. An eruption on 7 August from the E part of the summit, Batur Crater III, caused ashfall as far as ~6 km WSW (figure 1). Ash covered Kintamani on the caldera rim, one of Bali's famous tourist attractions. Incandescent lava fragments and black smoke were ejected to heights of 300 m. None of the larger lava fragments fell outside of the active crater. News reports indicated that the eruption generated 960 explosions through 11 August. Volcanic tremor recorded by the VSI on 13 August had a maximum amplitude of 4.5 mm, but was increasing. By 14 August, when lava reached the surface, the tremor amplitude was 23 mm.

Figure (see Caption) Figure 1. Map of the Batur caldera, showing hazard zones, selected towns, and extent of ashfall from the eruption that began on 7 Aug 1994. The inner caldera is not shown, but includes most of danger zones I and II. Courtesy of VSI.

As of 18 August, no evacuations from the area around the . . . volcano had taken place. About 180,000 people live in Bangli Regency, but only ~500 live in what a spokesman called the "critical region." Batur was declared off-limits for climbers on 7 August, and local villagers were put on alert. An official at a monitoring center said tourists who evaded guards and climbed the mountain were taking large risks. According to press reports, the eruptions have not reduced the number of visitors to the popular resort island; Batur's crater attracts ~300 people every day. Many observe the volcanic activity from Kintamani, on the crater rim (figure 1).

Geologic Background. The historically active Batur is located at the center of two concentric calderas NW of Agung volcano. The outer 10 x 13.5 km wide caldera was formed during eruption of the Bali (or Ubud) Ignimbrite about 29,300 years ago and now contains a caldera lake on its SE side, opposite the satellitic Gunung Abang cone, the topographic high of the complex. The inner 6.4 x 9.4 km wide caldera was formed about 20,150 years ago during eruption of the Gunungkawi Ignimbrite. The SE wall of the inner caldera lies beneath Lake Batur; Batur cone has been constructed within the inner caldera to a height above the outer caldera rim. The Batur stratovolcano has produced vents over much of the inner caldera, but a NE-SW fissure system has localized the Batur I, II, and III craters along the summit ridge. Historical eruptions have been characterized by mild-to-moderate explosive activity sometimes accompanied by lava emission. Basaltic lava flows from both summit and flank vents have reached the caldera floor and the shores of Lake Batur in historical time.

Information Contacts: VSI; AP; Reuters; UPI; ANS; D. Shackleford, Fullerton CA, USA.


Cumbal (Colombia) — July 1994 Citation iconCite this Report

Cumbal

Colombia

0.95°N, 77.87°W; summit elev. 4764 m

All times are local (unless otherwise noted)


Increased fumarolic activity

"Cumbal . . . (figure 1), has been showing signs of possible reactivation during the past year. New fumaroles have appeared and the gas column has grown noticeably larger. Cumbal was visited by volcanologists from INGEOMINAS and the Univ de Montréal on 11-15 July 1994. A portable seismometer was installed . . . at 4,185 m elev, ~580 m below the summit. Both high-frequency and long-period events were recorded, as well as some possible tremor episodes. Several fumarole fields at the summit (figure 2) exhibited maximum temperatures as follows: El Verde, 378°C; El Tábano, 191°C; La Desfondada, 132°C; La Plazuela, 99°C; La Grieta-verde, 84°C; Vecino a la verde, 80°C. El Tábano is a new fumarole field that appeared in early 1994. For comparison, in 1988 El Verde had measured temperatures of 150-326°C. The El Verde fumaroles produced audible noise. Most of the gas column at Cumbal appeared to emanate from the El Verde fumaroles."

Figure (see Caption) Figure 1. Location map showing Cumbal volcano and the city of Cumbal. Modified from Mendez (1989).
Figure (see Caption) Figure 2. Sketch map of the crater area of Cumbal, July 1994, showing fumarole locations. Courtesy of INGEOMINAS.

Reference. Mendez F., R.A., 1989, Catálogo de los volcanes actives de Colombia: Bol. Geol., v. 30, no. 3, 75 p.

Geologic Background. Many youthful lava flows extend from the glacier-capped Cumbal volcano, the southernmost historically active volcano of Colombia. The volcano is elongated in a NE-SW direction and is composed primarily of andesitic-dacitic lava flows. Two fumarolically active craters occupy the summit ridge: the main crater on the NE side and Mundo Nuevo crater on the SW. A young lava dome occupies the 250-m-wide summit crater, and eruptions from the upper E flank produced a 6-km-long lava field. The oldest crater lies NNE of the summit crater, suggesting SW-ward migration of activity. Explosive eruptions in 1877 and 1926 are the only known historical activity. Thermal springs are located on the SE flanks.

Information Contacts: G. Patricia Cortes and R. Torres Corredor, INGEOMINAS, Pasto; J. Stix and M. Heiligmann, Univ de Montréal.


Etna (Italy) — July 1994 Citation iconCite this Report

Etna

Italy

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

All times are local (unless otherwise noted)


Explosive degassing from La Voragine; fumarole temperatures reported

The following describes [fieldwork] on 1-27 June and 10-18 July 1994.

"As during visits in June-July and September-October 1993, Northeast Crater was blocked and inactive, but collapse was continuing around the edge with minor rockfalls every few minutes or so. Southeast Crater was also little changed from 1993, with a quietly degassing vent under the SE rim, but no indication of gas coming out under pressure. There was strong high-temperature fumarolic activity around the crater rim, temperatures being generally highest in the cracks.

"The Chasm (La Voragine) had a single vent in its floor measuring ~ 8 x 10 m, discharging gas continuously under pressure in rhythmic puffs at a rate of ~ 30 puffs/min. On 17 June and 12 July only, distinct explosions could be heard at the rate of 1-8/min. These were the first signs of explosive activity since the end of the 1991-93 eruption, and an indication that the Strombolian degassing that has characterized the summit over the past few hundred years is resuming.

"Bocca Nuova vent was degassing almost totally silently from two vents, one to the SE and one to the W; however, on 27 June when the weather was calm, 13 very faint gas puffs/min could be heard. The SE vent seemed similar to last year, measuring ~ 10 m in diameter, but the W vent had collapsed and enlarged considerably, now measuring perhaps as much as 50 m in diameter. On the early morning of 16 June a reddish tinge to the plume above Bocca Nuova was first noticed. Upon closer inspection on 17 June, the SE vent was seen to be pouring out thick clouds of red dust, apparently a result of internal collapse within the vent, while the W vent continued to emit white fume only. Dust emission intensified in the following days, causing the downwind side (S through W) of the summit to become a striking red color. The activity was continuing in mid-July.

"The levelling traverse showed comparatively small vertical movements since September 1993. The area near Belvedere, and other areas over the dyke intruded during the 1991-93 eruption, had subsided by up to 2 cm, as had the NE rift zone near Monte Pizzillo. During the same period, a small area ~1 km SW of the summit inflated by just over 1 cm. Horizontal movements measured since October 1993 showed generally small or insignificant changes, with nearly all lines recording changes of >1 cm. Only two stations appear to have moved by more than this; a station on the E edge of Southeast Crater had shifted 3 cm E relative to nearby stations, and a station close to the NW edge of the Bocca Nuova had moved 2 cm W. These movements are consistent with expansion of the central magma column as it refills.

"Surface temperatures were measured between 1 and 27 June at four active fumarole areas with a Minolta/Land Cyclops Compac 3 hand-held radiometer (8-14 mm). Temperatures were not corrected for spectral emissivity, so all radiant temperatures are given here as brightness temperatures. On the NE rift zone, nine areas of fumaroles were observed near the N edge of the 1966-67 lavas (between 2,450 and 2,500 m altitude). Temperatures for fumaroles at the two lowest of these areas ranged between 33 and 50°C. Another area of fumaroles observed at the upper rim of the W wall of the Valle del Bove around Belvedere, above the 1991-93 dyke, had temperatures in the 57.5-84.7°C range. Temperatures measured at fumaroles and cracks in the still-cooling 1991-93 lava-flow field in the Valle del Bove were between 85 and 221°C. The locations and temperatures of fumarole areas measured in the vicinity of the summit craters are given in table 5. Temperatures of the vents within the central craters were also measured from the crater rim: 342°C for the Chasm vent, and 159 and 81.5°C, respectively, for the SE and W vents of Bocca Nuova. Active fumaroles were observed, but not measured, along the 1991-93 fissure zone and 14 December 1991 cones and flows between Southeast Crater and Belvedere, along the October 1986 fissure zone, and in the Valle del Bove below Monte Simone."

Table 5. Fumarole temperatures in the vicinity of Etna's summit craters, measured on 18 and 27 June, and 14 October 1994. Courtesy of Andrew Harris, Open University.

Date Fumarole / Rift Locations Temperature (°C)
27 Jun 1994 NE Crater - at N rim 50.4-65.0
27 Jun 1994 NE Crater - rifts at NW rim 56.0-141
27 Jun 1994 NE Crater - at dip in NW rim 45.5-97.4
27 Jun 1994 NE Crater - at E rim 51.4-85.6
18 Jun 1994 Bocca Nuova - on N slope 40.5-75.6
18, 27 Jun 1994 Bocca Nuova - inside N rim 42.2-54.3
27 Jun 1994 Bocca Nuova - rifts at N rim 52.0-74.4
18 Jun 1994 Bocca Nuova - at SW rim 52.0-65.7
18, 27 Jun 1994 Central Craters - at S rim 40.6-82.6
27 Jun 1994 Between central and SE Craters 59.1-81.3
18, 27 Jun 1994 SE Crater - rifts and fumarole at N rim 51.2-312
27 Jun 1994 SE Crater - rifts and fumarole at W rim 60.0-208
14 Oct 1994 NE Crater - fumarole at N rim 39.2-77.4
14 Oct 1994 NE Crater - rifts at NW rim 153-246
14 Oct 1994 NE Crater - fumarole at W flank 50.4-74.2
14 Oct 1994 NE Crater - fumarole at W rim 41.0-210
14 Oct 1994 NE Crater - fumarole at S rim 50.5-221
14 Oct 1994 Bocca Nuova - fumarole at N flank 50.1-75.5
14 Oct 1994 Bocca Nuova - rifts and fumarole at N rim 47.3-74.5
14 Oct 1994 Bocca Nuova - fumarole at SW rim 50.0-72.4
14 Oct 1994 Central Craters - fumarole at S rim 49.2-82.4
14 Oct 1994 Fumarole between central and SE craters 50.2-82.8
14 Oct 1994 SE Crater - rifts and fumarole at N rim 57.5-482
14 Oct 1994 SE Crater - rifts and fumarole at NW rim 56.4-218
14 Oct 1994 SE Crater - rifts and fumarole at W rim 46.8-99.5
14 Oct 1994 SE Crater - rifts and fumarole at S rim 49.9-88.0
14 Oct 1994 SE Crater - rifts and fumarole at E rim 68.5-180
14 Oct 1994 SE Crater - rifts and fumarole at NE rim 52.2-121

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: J. Murray and A. Harris, Open Univ; L. Platt, Sheffield Univ; D. Renouf, UK.


Galeras (Colombia) — July 1994 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Seismicity remains low; crater described and fumarole temperatures reported

Seismicity during June and July showed no significant changes. . . . Low-frequency seismicity was at very low levels during June, although a "screw-type" event did occur; this type of event was numerous before eruptions in 1992-93. Shallow "butterfly-type" activity during the first half of June was similar to May, when the number of events decreased notably. These small-amplitude, short-duration, high-frequency events, interpreted as caused by fluid movement or rock fracture at shallow depths (<2 km) near the active cone, increased in number in the second half of June and through July. During June the fracture events were located N of the volcano, near the source that was active during November-December 1993, with other fracture events to the NE or closer to the crater. Additional sources were W and S of the crater. Fracture activity within the crater consisted of very small magnitude events (M <2.3) at depths between 2.1 and 9.7 km.

The active inner cone was visited on 21 July 1994 by volcanologists from INGEOMINAS and the Univ de Montréal. The morphology of the cone was modified considerably by the eruptions of 1992-93, which seem to have progressively deepened the crater to the present level of 200-300 m (figure 71). Prior to dome emplacement during October-November 1991 the crater was ~ 150 m deep; after dome growth in 1991-92, the crater was ~80 m deep. A N-S trending fracture, named Novedad, now breaches the S crater rim. Partial collapse of the crater rim and blocks 10-20 cm in size were noted on the N side of the cone.

Figure (see Caption) Figure 71. Sketch map (top) and perspective view (bottom) of the Galeras crater, July 1994. Small ovals represent fumaroles; crater depth is ~200-300 m. View is from the west. Drawn by Milton Ordonez, INGEOMINAS.

Some low-pressure fumaroles were noted in the deepest part of the crater, but gas was being emitted mainly in the shallower W and SW sectors. At Deformes fumarole, on the SW flank of the cone, temperature was measured and gas samples were collected for analysis. Maximum temperature was 138°C, significantly cooler than the ~200°C recorded in December 1992 and January 1993 (Zapata G., 1992; Goff et al., 1993). Besolima, generally the hottest measured fumarole on the cone's outer flanks, had largely disappeared. Las Chavas fumarole showed very low activity with a maximum temperature of 105°C. A new fumarole near the W rim of the cone, named Nuevas, had temperatures of 208 and 392°C. This fumarole is in the area where Florencia fumarole and remnants of the lava dome (destroyed in July 1992) had temperatures of 640°C on 26 November 1992 (Zapata G., 1992).

Stationary COSPEC measurements of SO2 in June from five points around the volcano showed low levels of gases (18-176 t/d), similar to the measurements obtained using the mobile COSPEC (79-217 t/d). July degassing was concentrated on the W periphery of the active cone, with low concentrations of SO2 (<220 t/d) measured by COSPEC.

Electronic tiltmeter variations in June at the Peladitos station were 2.4 µrad in the tangential component and 7.8 µrad in the radial component. The Crater tiltmeter fluctuated in June due to electronic problems; no deformation was observed in July. On 7 July the Agua Tibia springs, located in the Rio Azufral valley 5 km W of the active cone, had a temperature of 21°C and pH of 5.

References. Zapata G., J.A., 1992, Visita al crater del volcan Galeras: INGEOMINAS Internal Report, 30 November 1992, 2 p.

Goff, F., McMurtry, G.M., Adams, A.I., and Roldán-M., A., 1993, Stable isotopes and tritium of magmatic water at Galeras volcano, Colombia: EOS, Trans. Am. Geophys. Union, 74(43), p. 690.

Geologic Background. Galeras, a stratovolcano with a large breached caldera located immediately west of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Long-term extensive hydrothermal alteration has contributed to large-scale edifice collapse on at least three occasions, producing debris avalanches that swept to the west and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid-Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.

Information Contacts: R. Corredor and C. Gonzalez, INGEOMINAS, Pasto; J. Stix and M. Heiligmann, Univ de Montréal.


Gamalama (Indonesia) — July 1994 Citation iconCite this Report

Gamalama

Indonesia

0.8°N, 127.33°E; summit elev. 1715 m

All times are local (unless otherwise noted)


Eruptions generate ash cloud to ~5 km altitude and cause ashfall

A NOTAM that originated from the Ujung Pandang FIR on 6 May 1994 requested that all aircraft avoid the area around Gamalama volcano. VSI did not note any unusual activity on that day, and no ash cloud was detected on satellite imagery. The warning only noted that the height of "dust" was variable.

Members of the SVE visited Gamalama at 1130 on 21 July. Summit activity consisted of violent degassing from the summit crater, producing a white-gray plume above the volcano; no solid material was ejected during the observations. A small active fumarolic area on the W crater rim exhibited yellow sulfur deposits. White vapor was rising from a large crack on the E crater rim, a part of the crater that appeared to be very unstable. The bottom of the crater could not be seen from the rim.

VSI reported that activity from the main crater increased with a sudden eruption on 5 August 1994 at 2125. The eruption produced an ash cloud to a height of 3,000 m above the summit . . . and accompanying ash falls. A felt earthquake a few minutes before the eruption had an intensity of MM II-III. Volcanic tremor recorded since 10 August preceded another eruption at about 2400 on 13 August from the same location. A news report indicated that explosions on 14 August caused ashfall in Ternate (~ 4 km SE), and that 5-20 minor explosions/day had occurred in recent days.

Following eruptions in May 1993 (18:5 & 7; and VSI, 1993a), seismicity steadily decreased to low levels by the end of June; vapor emission stopped by the end of August 1993 (VSI, 1993b). Seismicity began increasing again in December 1993 (VSI, 1993b), and explosions were reported during January-March 1994 (19:05).

Geologic Background. Gamalama is a near-conical stratovolcano that comprises the entire island of Ternate off the western coast of Halmahera, and is one of Indonesia's most active volcanoes. The island was a major regional center in the Portuguese and Dutch spice trade for several centuries, which contributed to the thorough documentation of Gamalama's historical activity. Three cones, progressively younger to the north, form the summit. Several maars and vents define a rift zone, parallel to the Halmahera island arc, that cuts the volcano. Eruptions, recorded frequently since the 16th century, typically originated from the summit craters, although flank eruptions have occurred in 1763, 1770, 1775, and 1962-63.

Information Contacts: W. Tjetjep, VSI; H. Gaudru, C. Pittet, M. Auber, C. Bopp, and O. Saudan, EVS, Switzerland; BOM Darwin, Australia; AP; Radio Republik Indonesia.


Nevado del Huila (Colombia) — July 1994 Citation iconCite this Report

Nevado del Huila

Colombia

2.93°N, 76.03°W; summit elev. 5364 m

All times are local (unless otherwise noted)


Description of the Paez earthquake's mass wasting

The destructive earthquake-triggered mudflows of 6 June (19:5) were the subject of a preliminary report (Casadevall and others, 1994) following an investigation by a team from INGEOMINAS and the USGS during 30 June-9 July. What follows is a summary of that report, which includes first-hand observations on slope-failure and transport of loosened material.

The M 6.4 earthquake that struck on 6 June 1994 is now termed the Paez earthquake. Although the preliminary epicenter determination was W of the volcano's summit, a more recent estimate places it on Nevado del Huila's SSW flank, several kilometers N of the village of Irlanda (figure 1; BGVN 19:5). Prior to the earthquake, normal background seismicity prevailed; a series of aftershocks also took place beneath the volcano.

Earthquake damage was attributed to shaking, mass movement of loosened material, and flooding. The volcano's topography and volcanic deposits contributed to the disaster, but the primary area of landslides lay S of the main volcanic edifice and reached a maximum elevation of ~3,000 m. Aerial observers on 7 July saw no changes in either the vigor of fumaroles present near the summit or in the distribution and surface appearance of glaciers. Though dislodged ice was noted in news reports, none was found during fieldwork. The latest estimates on direct human impact from the earthquake are >150 fatalities, 500 people listed as missing, and 20,000 people displaced. Six bridges and >100 km of roads were destroyed.

All mass movement due to slope failure was previously called "mudflows" (19:5). The new report uses more precise terminology (Varnes, 1978), and provides an English-Spanish glossary that includes these and other terms: (a) rock, soil, and earth falls, (b) various kinds of slides including earth slides and debris slides, (c) rock avalanches, (d) debris avalanches, and (e) earth flows. According to this scheme, the bulk of the observed slides were earth slides derived from weathered residual soils that have developed on the bedrock. Lack of bedrock involvement and the limited amount of translations that involved bouncing, rolling, or falling resulted in few mass movements categorized as rock avalanches.

Nearly all of the 6 June earthquake-triggered landslides originated on slopes of >=30°. In this steep terrain they mainly began as shallow slips in residual soils. The soils had been saturated a few weeks prior to the earthquake by heavy rains. Reduced shear strength because of the saturated soils was a major factor in the observed slope failures and the velocity of the downslope movements. Typically these water-charged slides were ~ 1-2 m thick, and immediately liquified, transforming into either debris avalanches or earth flows moving rapidly downslope. In total, these processes stripped >50% of the vegetation from the steep hillsides. The slides themselves caused little direct damage since the steep slopes were generally uninhabited.

Adjacent to the volcano, in up-river villages such as Irlanda and Wila, damage took place as the mobile earth flows ran across relatively flat terrace surfaces. Earth flows in Irlanda were only 2 m thick, but they destroyed the houses and structures in their path. Some of the damage at Irlanda may have been caused by a high-velocity earth flow that began on the opposite side (the E side) of Rio Paez and crossed over.

The 1994 debris flows in the Rio Paez were cohesive (>3% of sediment with <0.004 mm size), which means that they remain intact and travel long distances. On the other hand, large previous debris flows preserved in lateral terraces along the river are of the noncohesive type that transformed into hyperconcentrated flows as they moved downstream. The noncohesive debris flows are thought to have been more closely related to past explosive volcanism and provide one means of analyzing past behavior at Huila. This point is noteworthy because the headwaters of the Rio Paez provide the drainage for almost the entire volcano. Because the bulk of debris flows must travel down the Rio Paez, study of the deposits along it should provide a thorough record of the volcano's seismically and magmatically generated deposits.

The report noted several analogous cases of "widespread stripping of saturated materials and vegetative cover from steep slopes" during seismic loading. One case involved the M 6.1 and 6.9 earthquakes of March 1987 in NE Ecuador. Those earthquakes triggered an estimated 75-110 million m3 of mass wasting, killed an estimated 1,000 people, destroyed a major oil pipeline, and caused US $1 billion in damages. These events are also of interest because Mount Rainier (Washington State, USA) contains a gravitationally unstable zone of altered rock high on its edifice. The zone could detach during seismic loading and move downslope, eventually reaching heavily populated areas.

Researchers continue to watch the volcano to see if the recent seismicity causes any changes to its normally passive hydrothermal system. Monitoring is done from an observatory in Popayan, 83 km SW.

References. Casadevall, T.J., Schuster, R.L., and Scott, K.M., 29 July 1994, Preliminary report on the effects of the June 6, 1994 Sismo de Paez (Paez earthquake), Southern Colombia: U.S. Geological Survey Response Team, 15 p.

Varnes, D.J., 1978, Classification of mass movements, in Schuster, R.L., and Krizek, R.J. (eds.), Landslides: Analysis and Control: U.S. National Academy of Sciences, Transportation Research Board Special Report 176, p. 11-33.

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

Information Contacts: INGEOMINAS, Popayan; T. Casadevall, USGS.


Ijen (Indonesia) — July 1994 Citation iconCite this Report

Ijen

Indonesia

8.058°S, 114.242°E; summit elev. 2769 m

All times are local (unless otherwise noted)


Minor phreatic eruption in February described

At 0915 on 3 February 1994, a small phreatic eruption took place from the S part of the crater lake. Coincident with the eruption, lake level rose ~1 m. Visual and seismic activity then returned to normal through July. During 7-14 August, the number of volcanic earthquakes and tremor increased compared to earlier in August. The temperature of the light-green crater lake was 39-42°C.

Geologic Background. The Ijen volcano complex at the eastern end of Java consists of a group of small stratovolcanoes constructed within the large 20-km-wide Ijen (Kendeng) caldera. The north caldera wall forms a prominent arcuate ridge, but elsewhere the caldera rim is buried by post-caldera volcanoes, including Gunung Merapi, which forms the high point of the complex. Immediately west of the Gunung Merapi stratovolcano is the historically active Kawah Ijen crater, which contains a nearly 1-km-wide, turquoise-colored, acid lake. Picturesque Kawah Ijen is the world's largest highly acidic lake and is the site of a labor-intensive sulfur mining operation in which sulfur-laden baskets are hand-carried from the crater floor. Many other post-caldera cones and craters are located within the caldera or along its rim. The largest concentration of cones forms an E-W zone across the southern side of the caldera. Coffee plantations cover much of the caldera floor, and tourists are drawn to its waterfalls, hot springs, and volcanic scenery.

Information Contacts: VSI.


Kanaga (United States) — July 1994 Citation iconCite this Report

Kanaga

United States

51.923°N, 177.168°W; summit elev. 1307 m

All times are local (unless otherwise noted)


Steam-and-ash plume rises 4,500 m; enlarged hot spot on imagery

On the morning of 15 July a pilot observed steam plumes rising from multiple vents to ~600 m above the summit. FWS personnel in Adak . . . reported steam plumes during 16-22 July. A distinct hot spot . . . was seen on a satellite image from 0906 on 22 July. FWS personnel aboard the RV Tiglax observed incandescent flows on the flank of Kanaga during the night of 27-28 July; low-level steaming from the summit area was continuing. Also in late July the FWS crew saw a blocky lava flow entering the sea on the NW flank, forming a new headland and small cove. Pilots reported incandescent flows on the NW flank during the following week, and steam plumes to 1,500 m altitude. On 10 August the RV Tiglax passed within ~3 km of shore and the crew observed the two NW-flank lava flows for the first time during daylight. Steam was rising from where the flows were entering the sea, and a strong SO2 odor was detected. Satellite imagery again recorded hot spots . . . during 2-12 August.

At 0500 on 18 August, the FAA received a pilot report of "glowing" at the summit. Pilots reported a light gray, dense steam cloud at 0800 rising to 4,500 m above the summit that had a mushroom-shaped top and was trailing to the E. A satellite infrared image taken at 0836 showed a summit hot spot twice as large as that seen in recent weeks, suggesting an increase in heating associated with production of lava flows. Also visible in the image was a plume extending 15-20 km NE; enhancements of calibrated data suggested that the plume may have contained some ash. Throughout the day, pilots and FWS personnel in Adak observed an eruption cloud consisting of a white, dominantly steam portion, which rose to ~4,500 m altitude, and a vigorously roiling, gray, ash-bearing portion that rose to an estimated 2,400-3,000 m altitude. A loud rumbling, similar to the sound of a freight train, was heard in Adak all afternoon and into the evening. Prevailing winds carried the plume NE, and a light curtain of fallout was observed. Satellite images from 1133 and about 2000 on 18 August showed a plume drifting NE.

The summit hot spot, which on 18 August appeared to have doubled in size, persisted on a satellite image from 1004 on 19 August. No plume was visible that day, although cloud cover may have obscured it. FWS observers reported continued rumbling from the direction of the volcano. Kanaga continued to erupt minor amounts of ash during 20-21 August, interfering with local air traffic and dropping a light dusting of ash on the community of Adak. As of midday on 22 August, analysis of satellite imagery indicated a possible plume, containing minor ash, drifting generally ESE from the volcano over Adak. The FAA enforced a 24-km restricted flight zone around Kanaga until 1430 to minimize the possibility of aircraft encountering an ash cloud during instrument approach and departure. Poor weather obscured the volcano through the morning of 22 August. However, no ash cloud was seen from Adak as visibility improved through the day.

Pilots and other observers continued to report and photograph avalanches of hot fragmental debris cascading down the N flank of the volcano into the ocean. Although AVO has been unable to clearly discern the source of this material, it likely represents collapse of a growing lava dome or ejection of hot blocks of lava from near or within the summit crater. Based on the last eight months of activity, continuing episodes of ash eruption accompanied by avalanching of hot debris down the volcano's flanks can be expected. Depending on wind conditions and the size of a given eruptive episode, additional ashfall on Adak is possible.

. . . .The eruption has been characterized by intermittent, low-level steam and ash emissions producing plumes rarely rising over 3,000-4,500 m altitude and drifting a few tens of kilometers downwind. Although tracking of ash fallout is limited due to the remote location of Kanaga, it appears from satellite imagery that detectable fallout has been confined to within a few tens of kilometers of the volcano. On 22 August, AVO learned that several very light dustings of fine ash on the N portions of Adak had occurred over the past few months.

Geologic Background. Symmetrical Kanaga stratovolcano is situated within the Kanaton caldera at the northern tip of Kanaga Island. The caldera rim forms a 760-m-high arcuate ridge south and east of Kanaga; a lake occupies part of the SE caldera floor. The volume of subaerial dacitic tuff is smaller than would typically be associated with caldera collapse, and deposits of a massive submarine debris avalanche associated with edifice collapse extend nearly 30 km to the NNW. Several fresh lava flows from historical or late prehistorical time descend the flanks of Kanaga, in some cases to the sea. Historical eruptions, most of which are poorly documented, have been recorded since 1763. Kanaga is also noted petrologically for ultramafic inclusions within an outcrop of alkaline basalt SW of the volcano. Fumarolic activity occurs in a circular, 200-m-wide, 60-m-deep summit crater and produces vapor plumes sometimes seen on clear days from Adak, 50 km to the east.

Information Contacts: AVO.


Kilauea (United States) — July 1994 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 collapses and littoral explosions occur as lava flows continue to enter the ocean

"The . . . eruption continued throughout July with more lava entering the ocean in the W Kamoamoa/Lae Apuki area. On the morning of 8 July, a piece of the Kamoamoa bench, ~4,000 m2, fell into the ocean. Littoral explosions following the collapse deposited a small amount of spatter on the delta. A wave associated with the collapse event deposited blocks on the surface of the delta, 40 m inland of the sea cliff. One line of stations, set up to monitor movement of cracks on the active bench, disappeared into the ocean with the collapse. Following the event, the remaining lines recorded several centimeters of seaward movement. The cracks on the bench continued to widen throughout the month. Some of the larger cracks contained standing water.

"Surface activity was confined mostly to the W Kamoamoa/Lae Apuki bench; however, on 11 July, a surface flow broke out of the active tube on Pali Uli. This flow did not reach the ocean before stagnating. There were no significant changes in the Pu`u `O`o lava pond, which was 79 m below the crater rim in July.

"The ocean entries were intermittently explosive, following the 8 July collapse, due to smaller collapses along the front of the bench. Littoral explosions increased in frequency and magnitude later in the month. The most dramatic event began on the afternoon of 26 July. By the following day, large spatter bursts had built a 10-m-high littoral cone on the leading edge of the Kamoamoa/Lae Apuki bench. Explosive activity was initially episodic but was continuous by at least 1810 on 27 July. At 2025 a cascade of lava, about 5 m wide, ripped out of the tube on Pali Uli, from the same area as the 11 July flow. Within 50 minutes, the explosive activity at the ocean had subsided. The cascade on Pali Uli fed flows that eventually stagnated the following day. Activity at the ocean paused briefly, but by 1112 on 28 July, plumes were again visible off the Kamoamoa/Lae Apuki bench. Surface flows broke out on the bench, and by the end of the month extended the bench 5-10 m W."

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: T. Mattox, HVO.


Krakatau (Indonesia) — July 1994 Citation iconCite this Report

Krakatau

Indonesia

6.102°S, 105.423°E; summit elev. 155 m

All times are local (unless otherwise noted)


Frequent ash explosions (300-450/day) reach heights up to 500 m

Ash explosions continued at a rate of 300-450/day in early August. The height of the ash columns, measured from the [Pasuaran Observatory] during clear weather, ranged from 150 to 500 m above the summit, with incandescent projections evident at night. The sporadic eruptions have deposited ash over almost the entire island. During the second week of August, explosion earthquakes averaged 460 events/day. Occasionally, explosion sounds were heard and vibrations felt at the observatory.

Geologic Background. The renowned volcano Krakatau (frequently misstated as Krakatoa) lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 or 535 CE, formed a 7-km-wide caldera. Remnants of this ancestral volcano are preserved in Verlaten and Lang Islands; subsequently Rakata, Danan, and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan, and left only a remnant of Rakata. This eruption, the 2nd largest in Indonesia during historical time, caused more than 36,000 fatalities, most as a result of devastating tsunamis that swept the adjacent coastlines of Sumatra and Java. Pyroclastic surges traveled 40 km across the Sunda Strait and reached the Sumatra coast. After a quiescence of less than a half century, the post-collapse cone of Anak Krakatau (Child of Krakatau) was constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan. Anak Krakatau has been the site of frequent eruptions since 1927.

Information Contacts: VSI.


Langila (Papua New Guinea) — July 1994 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)


Thick ash clouds from Crater 2 accompanied by explosion sounds

"Eruptive activity at Crater 2 continued during July, while Crater 3 activity was at a low level. Throughout the month, Crater 2's normal moderate emissions of thin white-grey vapour were disrupted by forceful ejections of thick, mushroom-shaped, grey-brown ash clouds accompanied by low explosion and rumbling sounds. These caused fine ashfall NW of the volcano. On 16 and 22 July, the ash clouds rose several thousands of meters above the crater. Steady weak night glow was reported on 26 July and there was fluctuating weak-bright glow on the 29th. Crater 3 continued to emit small volumes of mostly white vapour, sometimes with blue and grey vapour. There were no audible sounds or night glow reported during July. Seismic activity throughout the month remained at a low level with between 1 and 7 small low-frequency earthquakes/day."

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: B. Talai, R. Stewart, and C. McKee, RVO.


Lascar (Chile) — July 1994 Citation iconCite this Report

Lascar

Chile

23.37°S, 67.73°W; summit elev. 5592 m

All times are local (unless otherwise noted)


Moderate short-lived eruption sends plume over Argentina

Renewed Vulcanian activity during 20-26 July generated plumes up to ~9,000 m altitude, ~4,000 m above the summit . . . . On 20 July at 1630 a grayish column 400-500 m high was emitted from the crater. The next day at 1230 a brownish eruptive column rose 3,000-4,000 m and immediately drifted NE. Very fine ashfall was reported in Salar de Olaroz in the Argentine Puna, 120 km NE of the vent. At 1430 on 23 July another eruption plume to a height of 3,000-4,000 m was blown NNE. No ashfall was reported in the Argentine Puna following this activity.

A single short-lived Vulcanian explosion at about 1200 on 26 July generated a column and NNE-trending plume that soon detached from the volcano; prevailing high-level winds then shifted the plume toward the E. Witnesses from Toconao (35 km NW) and San Pedro de Atacama (70 km NW) reported a moderate explosion followed by a dark-colored mushroom-shaped column that slowly rose to 4,000 m height. Pilots from Aerolineas Argentinas, AeroMonterrey, and Lineas Aereas de Chile reported to the Argentina National Metereological Service that the plume, ~30 km wide and 200 km long, reached an altitude of 9,000 m. Ashfall was only reported in areas close to the volcano. No ashfall was reported in the small village of Catua along the Chilean-Argentine border, 80 km E of Lascar. Immediately after the eruption the volcano showed very diminished activity, with weak white fumarolic plumes that hardly rose above the crater rim. From 27 July to 4 August the volcano exhibited normal fumarolic activity.

Infrared images of the 26 July ash cloud were captured by Raúl Rodano and Luis Ganz from the Meteosat 3 satellite (figure 22). An image taken at 1346 on 26 July showed an ESE-directed plume 50 x 20 km in size, reaching an altitude between 3,600 and 5,400 m (figure 22, top). At 1523 another image showed a 130-km-long plume with the trailing edge located 60 km from Lascar (figure 22, middle). On the E side of the plume, a core (40 km in diameter) developed vertically and reached ~7,000 m altitude. The lower levels of the plume were oriented ESE, following the general atmospheric circulation. Because of wind-shear between 5,400 and 7,000 m, the plume was reoriented NNE by upper-level winds (200°- 70 km/hour). On the image taken at 1631, the plume is 180 km long and 100 km from the source (figure 22, bottom). Based on analysis of this imagery, the NNE-oriented E end of the plume reached an estimated maximum height of 7,500 m. Although the sky was cloudy by 1830, scattered parts of the NNE-oriented plume could be seen 80 km E of Jujuy, Argentina, drifting E at 80 km/hour at an estimated altitude of 4,500 m. With frame animation it was possible to discern the dispersed plume reaching Presidente Roque Saenz Pena city, 800 km E of Lascar, at 2009 on 26 July.

Figure (see Caption) Figure 22. Infrared images of the 26 July 1994 plume from Lascar (white area) taken from the Meteosat 3 satellite. At 1346 (top) the small plume (50 x 20 km) was moving ESE. By 1523 (middle) the trailing edge of the 130-km-long detached plume was located 60 km from the volcano. On the image taken at 1631 (bottom), the plume was 100 km from the source, 180 km long, and the E end was oriented NNE. Approximate location of Lascar is shown by the black triangle; Jujuy, Argentina, is indicated by the white square. Courtesy of Raúl Rodano and Luis Ganz.

These eruptions comprise the fourth period of Vulcanian activity following the large subplinian eruption of 19-20 April 1993. Eruptions were also reported in August and December 1993, and February 1994. All are thought to have been caused by blockage of the degassing magmatic system due to collapse of the dome formed in the late stages of the April 1993 eruption. The present morphology of the crater is unknown, although this renewed activity suggests further subsidence of the crater floor due to conduit degassing. Lascar, the most active volcano of the northern Chilean Andes, contains five overlapping summit craters along a NE trend. Prominent lava flows descend its NW flanks.

Reference. Gardeweg P., M.C., 1994, La Explosion del 26 de Julio, 1994, X Informe sobre el comportamiento del Volcan Lascar: Informe Inedito, Biblioteca Servicio Nacional de Geologia y Mineria, 4 p.

Geologic Background. Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km E, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away. The largest historical eruption took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Information Contacts: M. Gardeweg, SERNAGEOMIN, Santiago; J. Viramonte, R. Becchio, I. Petrinovic, and R. Arganaraz, Instituto Geonorte Univ Nacional de Salta, Argentina; B. Coira and A. Perez, Instituto de Geologia Universidad de Jujuy, Argentina; R. Rodano and L. Ganz, Aerolineas Argentinas Weather Division, Buenos Aires, Argentina; H. Corbella, CONICET - Argentine Museum of Natural Sciences, Buenos Aires.


Manam (Papua New Guinea) — July 1994 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)


Explosions on 5-7 July generate ash clouds and eject lava fragments

"During July, there was a brief increase in the level of activity from Southern Crater, while Main Crater activity continued to remain at a low level. Activity from Southern Crater was low from 1 to 4 July with gentle emissions of small volumes of white vapour. From 1430 on 5 July onwards, activity increased as weak deep-sounding explosions were heard at 5-10 minute intervals accompanying forceful emissions of grey-brown ash clouds. Incandescent lava fragments were seen being ejected from Southern Crater during the evening until the activity stopped at 2130. Ash emissions continued to occur until 7 July, and only one explosion was heard on 6 July. For the remainder of the month, activity at Southern Crater continued at the normal low level, with only white vapour emissions and blue vapour observed on 12 and 15 July.

"Throughout the month Main Crater continued to emit white vapour, weak to moderate in volume. A whitish-grey plume was seen on 31 July. No sounds were heard and no night glow was observed.

"Seismic activity remained at a low-moderate level throughout the month, with small fluctuations in the number and amplitude of low-frequency earthquakes. On average ~1,170 earthquakes/day were recorded, and there was a brief quiet period from 25 to 27 July when <500 earthquakes/day were recorded. There were no significant tilt changes in July.

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

Information Contacts: B. Talai, R. Stewart, and C. McKee, RVO.


Marapi (Indonesia) — July 1994 Citation iconCite this Report

Marapi

Indonesia

0.38°S, 100.474°E; summit elev. 2885 m

All times are local (unless otherwise noted)


Eruption sends ash column to ~6 km above sea level; summary of 1993 activity

An eruption at 0016 on 12 August 1994 sent an ash column to ~6 km altitude, a height of 3,200 m above the summit. Another explosion at 0046 ejected ash 280 m high. From the observatory ~7 km from the crater, observers noted incandescent projections as high as 300 m above the crater rim, accompanied by explosion sounds and vibrations. Ashfall in and around the city of Bukittinggi . . . ranged from 0.5 to 1 mm thick. Shallow volcanic earthquakes were recorded after the explosions, but gradually decreased.

Eruptions during the first half of 1993 (VSI, 1993a) produced lapilli and ash that were deposited in a radius of 1.5-3 km from the active crater. A dark gray column rose as high as 1,200 m above the summit . . . , but was usually in the 400-500 m range. Explosion earthquakes from January to July 1993 fluctuated between 1 and 77 events/day. The frequency of explosions increased in July 1993, but then decreased from August through December (VSI, 1993b). These explosions during Jul-Dec 1993 deposited lapilli and ash within a 750-m-radius of the active crater. Incandescent material fell within a few tens of meters of the crater rim. Average plume height in the second half of 1993 was 400-800 m, reaching a maximum of 3,200 m above the summit. Throughout 1993, deep volcanic earthquakes (A-type) were detected at a rate of 6-41/month. Between 42 and 338 shallow (B-type) events were recorded each month.

Geologic Background. Gunung Marapi, not to be confused with the better-known Merapi volcano on Java, is Sumatra's most active volcano. This massive complex stratovolcano rises 2,000 m above the Bukittinggi Plain in the Padang Highlands. A broad summit contains multiple partially overlapping summit craters constructed within the small 1.4-km-wide Bancah caldera. The summit craters are located along an ENE-WSW line, with volcanism migrating to the west. More than 50 eruptions, typically consisting of small-to-moderate explosive activity, have been recorded since the end of the 18th century; no lava flows outside the summit craters have been reported in historical time.

Information Contacts: VSI.


Masaya (Nicaragua) — July 1994 Citation iconCite this Report

Masaya

Nicaragua

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

All times are local (unless otherwise noted)


Sulfur-rich plume and incandescent ejections from opening in lava lake

Scientists from FIU and INETER visited Masaya for about an hour on the afternoon of 26 May 1994 and noted that the two incandescent openings (5-7 m in diameter) in the cooling lava lake observed on 1 March near the N wall of Santiago crater (BGVN 19:03) had coalesced into a single opening 10-12 m long. A sulfur-rich plume was being emitted from the opening at a rate of several pulses/minute; the pulses were accompanied by jetting sounds easily heard from the S rim. Fresh, black ash covered the crater floor immediately SW of the opening. INETER scientists reported that small Strombolian explosions ejected incandescent material from the opening several times during May and June 1994.

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

Information Contacts: Peter C. La Femina, Michael Conway, and Andrew MacFarlane, FIU; Christian Lugo, INETER.


Merapi (Indonesia) — July 1994 Citation iconCite this Report

Merapi

Indonesia

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

All times are local (unless otherwise noted)


Increased deformation precedes a nuee ardente

A nuée ardente erupted around 1400 on 16 July 1994, an event preceded by a clear increase in tilt several days before the eruption. Figure 9 shows tilt measurements during the interval 1-18 July. One set of measurements came from a site on Merapi's summit (Goa Jepang, ~2,900 m elevation); the other set of measurements came from a cave on Merapi's S flank (~1,000 m elevation).

Figure (see Caption) Figure 9. Tilt at Merapi recorded at both the summit and in a cave on the S flank, 1-18 July 1994 Courtesy of Arnold Brodscholl.

The daily temperature variation in the cave is<1°C, suggesting little influence from temperature there (left-hand scale). The daily record of tilt varied significantly less at the cave site (typically <100 µrad) than at the summit site (typically ~150 µrad), an observation consistent with the more stable temperature in the cave.

Tilt began increasing at both sites roughly five days prior to the eruption. During this interval the tilt at both sites correlated consistently overall, and moderately at the finer-scale. Tilt ceased to track consistently near the end of the eruption, when the flank site underwent a dramatic decrease, a turn-around that began prior to the end of the eruption. Summit tilt measurements in January 1993 were similar to those presented here but then measurements at the cave site were a rarity, leaving the increased tilt without confirmation.

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: A. Brodscholl, GMU; Subandryo, VSI; B. Voight, Pennsylvania State Univ.


Momotombo (Nicaragua) — July 1994 Citation iconCite this Report

Momotombo

Nicaragua

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

All times are local (unless otherwise noted)


Summit fumarole temperatures range from 238 to 655°C

Beginning on 11 June, scientists from FIU and INETER deployed a datalogger in the crater to continuously monitor fumarole temperatures and barometric pressure. The team entered the summit crater three times along a trail that crosses an active avalanche chute and leads around to the NE crater rim. Condensate and Giggenbach-type samples were collected from fumaroles along the SW crater wall. These fumaroles were very corrosive, as indicated by the destruction of the datalogger thermocouples, and had temperatures ranging from 238 to 655°C. A voluminous plume was rising from the crater on 13 March.

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

Information Contacts: Peter C. La Femina, Michael Conway, and Andrew MacFarlane, FIU; Christian Lugo M., INETER.


Nyamuragira (DR Congo) — July 1994 Citation iconCite this Report

Nyamuragira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


High lava fountains feed lava flow on NW flank

High lava fountaining in early July took place from a new vent on the W flank, named Kimera. Located ~100 m S of the 1971 Rugarama cone, this vent became active at 2148 on 4 July, but remained active for only 4-5 days. The lava flows generally moved W until at least 10 July, when the flows reached their maximum extent. By 11 July, the small lake (Magera) at the E foot of a Precambrian escarpment was entirely filled and dried by the flow. High SO2 concentrations detected by the TOMS during 5-10 July were most likely caused by this activity at Nyamuragira and not from the lava lake at Nyiragongo. Nyamuragira also emitted levels of SO2 detectable by satellite during 17-19 July 1986 (275-375 ± 30% kt) and on 24 September 1991 (20 kt).

A press report described falls of both ash and Pele's hair during the first half of July in the Mokoto Hills, above the W escarpment of the rift ~20 km from the volcano. Several farmers reported problems caused by cattle eating ash-laden grass.

Long-term monitoring data indicated an apparent acceleration in seismo-geodetic activity in the past 10 years. Seismicity steadily increased from <200 volcanic events/month in 1960-65 to ~300-400/month in the early 1980's (figure 13). Increased seismicity after 1985 suggests an acceleration of magma supply into the volcano. The geodimeter network operating on the Nyamuragira summit has also revealed a gradual strain increase since 1980, showing that the crater is dilated.

Figure (see Caption) Figure 13. Monthly number of volcanic earthquakes at Nyamuragira, 1960-92. The short-period seismic station is located 110 km from the volcano. Vertical arrows indicate flank eruptions. Courtesy of H. Hamaguchi.

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

Information Contacts: N. Zana, Centre de Recherche en Géophysique, Kinshasa; H. Hamaguchi, Tohoku Univ; J. Durieux, GEVA, Lyon, France; G. Benhamou, Libération newspaper, France; T. Casadevall, USGS; I. Sprod, GSFC.


Nyiragongo (DR Congo) — July 1994 Citation iconCite this Report

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


Lava lake activity produces strong red glow above crater

For four days around 14 July a dense steam-and-gas plume was visible from Goma, and red glow could be seen at night. An amateur video taken on an unknown day between 19 and 24 July included a 6-second partial view of the crater that revealed a large very active lava fountain roughly in the center of the crater. A large, flat spatter cone had been built, with a least three large openings in the walls and lava flows radiating from the openings. The entire lava lake was not active. The background was hidden by gases and clouds, making it impossible to determine the elevation of the lava lake surface. Following the 1982 activity, the surface was 400 m below the crater rim. A very strong red glow was again observed above the crater during the night of 29 July. Very little red glow was reported in early August.

Another eruption within the summit lava lake began at about 1900 on 10 August. Red glow above the summit could be seen from Goma during daylight as well as at night. Press reports also stated that "ash and dust" had been emitted from the volcano. The increased activity on 10-13 August and strong red glow visible from the refugee camps caused some concern among the refugees and relief workers.

Volcanologists from Zaire, Japan, France, and the USGS were all present in Goma from 19 to 23 August. The primary purpose of the USGS scientists was to evaluate the hazards posed to the ongoing relief operations in Goma, which contained more than one million Rwandan refugees and the large Zairian population. Specific hazards addressed included the threat of active lava flows to resettlement camps and infrastructure, the threat of volcanic ash to air relief operations, and the threat of CO2 accumulation to refugees in resettlement camps along the Goma-Sake road.

During the flight to Goma on 19 August, USGS volcanologists flew over and around the crater. Although the crater floor was clearly visible, no signs of activity were observed. However, during the pre-dawn hours on 20 August, strong red glow above the main crater could be seen. Early that morning the French Army flew USGS and French volcanologists to the summit. At that time the lava lake was very active, with fountaining of lava up to 40 m above the surface of the crater floor, estimated to be ~450 m below the crater rim. Seismograms from instruments operated by Zairan scientists clearly showed this eruptive activity. The eruption-related seismicity had ended by 22 August, and no additional red glow was noted. No activity was observed during an aerial inspection the next day, but red glow was again seen early on 24 August.

Geologic Background. One of Africa's most notable volcanoes, Nyiragongo contained a lava lake in its deep summit crater that was active for half a century before draining catastrophically through its outer flanks in 1977. The steep slopes of a stratovolcano contrast to the low profile of its neighboring shield volcano, Nyamuragira. Benches in the steep-walled, 1.2-km-wide summit crater mark levels of former lava lakes, which have been observed since the late-19th century. Two older stratovolcanoes, Baruta and Shaheru, are partially overlapped by Nyiragongo on the north and south. About 100 parasitic cones are located primarily along radial fissures south of Shaheru, east of the summit, and along a NE-SW zone extending as far as Lake Kivu. Many cones are buried by voluminous lava flows that extend long distances down the flanks, which is characterized by the eruption of foiditic rocks. The extremely fluid 1977 lava flows caused many fatalities, as did lava flows that inundated portions of the major city of Goma in January 2002.

Information Contacts: H. Hamaguchi, Tohoku Univ; J. Durieux, GEVA; T. Casadevall and J. Lockwood, USGS; AP.


Poas (Costa Rica) — July 1994 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Ashfall SW of the summit covers 56 km2

Despite roughly 3 months of rainy weather, the colorful northernmost crater lake that evaporated this past year remained nearly dry, venting became alarmingly noisy, and in the interval from 9 July to 5 August the volcano produced a series of ash falls. These falls were carried to the SW and covered a roughly 56 km2 area.

Increased vigor of fumaroles has led to vapor columns reaching >1 km above the lake floor; the columns were blown to the W and SW. Some of the columns were red to orange in color, presumably due to combustion of sulfur. In the recent past the most vigorous fumaroles were located near the former lake's center. These fumaroles diminished in size; during July the ones located SW of the former lake were of greatest importance.

On 21 July, a fumarole S of the former lake generated a white-colored column; thermocouple measurements of the fumarole revealed a 495°C temperature. The highest pressure fumarole, also located S of the former lake, emitted a red- to orange-colored plume. Continuously jetted gases contained entrained sediment. These escaping gases had a temperature of 515°C, measured with a pyrometer aimed toward the vent. Other fumaroles issued sporadic sediment and colored gases; temperature at the dome was 81°C. ICE and ECG reported jetting gases thrusting to 350 m above the crater floor and then rising convectively to 1 km. Using infrared thermometry, temperatures as high as 700°C were measured in the S-vent area.

Ash was erupted on the night of 9 July and into the morning of 10 July. Continued reports of ash fall came from San Miguel Arriba, Trojas, San Luis de Grecia, Cajon, and Porvenir de Sarchi (figure 53). These reports continued for 2 days; later, mapping and compilation led to an ash distribution map for this and later eruptions in July (figure 53). Blocks were principally limited to the crater area, fine ash covered much of the summit area, and the finest ash blew as far as about 15 km. The fumaroles ejecting lake sediment continued to grow, and ejected ash with blocks. Such events were noted seven times in late July (24, 25, 27, 28, 29, and twice on 30 July). In general, the strongest ash eruptions were accompanied by loud jet-like noises.

Figure (see Caption) Figure 53. Distribution of ash from Poás during July 1994. Scale is approximate; roads indicated by dashed lines, rivers by solid lines, and settlements by dots. Courtesy of OVSICORI-UNA.

OVSICORI-UNA reported July seismicity from station POA2 (2.5 km SW of the active crater) in terms of several types of events (figure 54). In July, a total of 4,994 events took place. Starting on 26 July several high-frequency (volcano-tectonic) earthquakes took place each day.

Figure (see Caption) Figure 54. Poás seismicity for July 1994. Courtesy of OVSICORI-UNA.

The amount of deformation on two distance-measurement lines has, since 1973, shown a tendency toward contraction, amounting to about 0.7 and 1.8 ppm/month, respectively. Between 24 June and 5 July both lines suddenly contracted about 19 ppm. From 22 July until the end of the month there were no further significant changes. Back in the interval between 8 March and 12 May a component of two leveling lines deflated slightly (10 µrad). During the last re-occupation of the leveling lines, which took place at the end of July, one line 2 km S of the active crater had inflated by about 17 µrad.

The increased degassing has led to a variety of health and environmental problems. Crops and soils have been damaged. Residents on the W and SW flanks continue to report irritations to the throat, skin, and eyes when gases and ash enter their communities.

On the morning of 22 August an American Airlines flight reported an eruption cloud to ~6 km. Visibility over Poás was poor due to thunder storms to the E and clouds in its vicinity; satellite imagery was unable to detect the plume. Jorge Barquero described this plume as consisting of vapor and gas. A plume on the previous day reached to about 2 km above the vent; heights of these plumes were highly dependant on local wind conditions. As of 22 August, no confirmed ash-bearing plumes had erupted since 5 August.

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

Information Contacts: E. Fernández, J. Barquero, V. Barboza, R. Van der Laat, F. de Obaldia, and T. Marino, OVSICORI; G. Soto, G. Alvarado, and F. Arias, ICE; M. Mora, C. Ramirez, and G. Peraldo, UCR.


Rabaul (Papua New Guinea) — July 1994 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)


Seismicity remains low; minor subsidence

"July was relatively quiet, with 220 detected earthquakes . . . . Activity was highest in the middle of the month, with half the earthquakes occurring between 13 and 19 July, and two swarms on those days. Most of the earthquakes, including the 13 July swarm, were located on the NE portion of the ring fault on the E side of Greet Harbour at depths of 0-4 km. Most of the rest were located near the W portion of the ring fault. An exception to this was the swarm on 19 July, which was located, albeit poorly, in the center of Karavia Bay. None of the earthquakes were large enough to be felt. The largest earthquake during the month, M 2.7, occurred on 5 July. Leveling measurements on 19 July showed a very small amount of subsidence, <9 mm, at the end of Matupit Island since 27 June.

"On 13 July, signals were recorded from three earthquakes that originated outside the network, somewhere N of Rabaul. S-P times between 2 and 4 seconds were consistent with locations near Tavui caldera, an underwater caldera N of Rabaul. This caldera was only discovered in 1984 and virtually nothing is known about it. Records are currently being checked for any other seismic activity that may have come from this vicinity."

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

Information Contacts: B. Talai, R. Stewart, and C. McKee, RVO.


Ruapehu (New Zealand) — July 1994 Citation iconCite this Report

Ruapehu

New Zealand

39.28°S, 175.57°E; summit elev. 2797 m

All times are local (unless otherwise noted)


Relatively stable with water cooling of Crater Lake

When visited on 8 June, Crater Lake appeared a very pale, almost yellowish, gray. On 4 July, as was more typical for the recent past, the crater lake was a uniform battleship-gray with no evidence of convection or slicks. Temperature at Outlet, 22°C, was slightly higher than for June-July in past years. The lake is currently cooling following a minor heating event in early June that followed strong acoustic signals, minor earthquakes, and volcanic tremor 10-15 days earlier. These two recent visits revealed no evidence of eruptive activity.

On 4 July, unusually thick accumulations of snow prevented deformation surveys and emphasized the need to install tiltmeters in key locations to improve the continuity of monitoring. Snow and ice were removed from the ARGOS satellite installation, but the solar panel could not be located under deep snow and battery and transmission power steadily declined.

A working party coordinated by the Ministry of Civil Defence has considered developing a contingency plan for volcanic hazards. They also may adopt a system using "Volcanic Alert Levels" graded from 1 (low level) to 5 (highest level, hazardous eruption in progress).

Geologic Background. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The dominantly andesitic 110 km3 volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 km3 ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake (Te Wai a-moe), is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3,000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys.

Information Contacts: P. Otway, B. Scott, and A. Hurst, IGNS Wairakei.


Semeru (Indonesia) — July 1994 Citation iconCite this Report

Semeru

Indonesia

8.108°S, 112.922°E; summit elev. 3657 m

All times are local (unless otherwise noted)


Small ash eruptions to 500 m above the summit

Eruptive activity on 3 February 1994 produced ashfalls, lava avalanches, and pyroclastic flows, destroying a village and killing 6 people (19:01). Total volume of the pyroclastic-flow deposits was about 6 million m3.

During 5-14 August observations, visual and seismic activity . . . were normal. The daily number of explosion earthquakes fluctuated between 40 and 100 events, and volcanic tremor was occasionally recorded with a maximum amplitude of 4 mm. Ash eruptions generated clouds up to 500 m above the summit. There were no pyroclastic flows or lava avalanches.

Geologic Background. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano.

Information Contacts: VSI.


Telica (Nicaragua) — July 1994 Citation iconCite this Report

Telica

Nicaragua

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

All times are local (unless otherwise noted)


Explosive eruption causes ashfall >12 km SW of the summit

An eruption on 31 July produced a gas-and-ash column that rose ~800 m above the 1,060-m-high summit. Ashfall was reported SW of the volcano (figure 6). Phreatic activity continued until 12 August with gas emission and minor ash explosions. Seismicity has been recorded continuously since December 1993, when a permanent telemetered seismic station (TELN: short-period, vertical-component) was installed ~500 m E of the active crater rim (figure 7). Also since December 1993, the Instituto Nicaragüense de Estudios Territoriales (INETER) has collaborated with the government, local authorities, civil defense, and the media, to educate the population about the situation at the volcano. Due to the relatively low magnitude of this eruption, it was not necessary to carry out the prepared evacuation plans.

Figure (see Caption) Figure 6. Ashfall from Telica, 31 July-6 August 1994. Courtesy of INETER.
Figure (see Caption) Figure 7. Sketch map of the summit area at Telica, showing locations of crater fumaroles (left) and seismic stations (right). Courtesy of INETER.

A seismic event on 15 June 1994 was recorded by several stations of the Nicaraguan seismic network, up to distances of ~40 km from Telica. This event at a depth of 6 km had a maximum magnitude of 2.1. The 31 July eruption was preceded by a steady increase in seismicity during 15-25 July (figure 8), recorded by station TELN. Seismicity had increased from25 events/day at the end of May. By the end of July there were up to 150 events/day.

Figure (see Caption) Figure 8. Seismicity at Telica, February-August 1994. Courtesy of INETER.

Crater and fumarole observations, March-June 1994. Beginning on 3 June, scientists from Florida International Univ (FIU) and INETER spent 15 days at Telica as part of an ongoing investigation to determine the areal extent and intensity of degassing, and the role of structural controls on degassing from the volcanic complex. A lacustrine deposit was observed in March at the S end of the crater, and a small, muddy brown lake was visible in May-June. All observations were made from the NE rim, where jetting sounds were clearly audible. Sulfur-rich steam from the crater sometimes moved down the slopes of the volcano, filling the NW valley with high concentrations of SO2; sulfur odor could occasionally be smelled on the NE slope. Residents on the flanks of the volcano stated that the activity was not unusual for this time of the year.

Fumarole temperatures near station TELN were in the 81-86°C range, similar to temperatures in September 1993 and March 1994. A low-temperature fumarole was discovered on the lower ESE slope of the ridge occupied by the seismic station. A data-logger recorded fumarole temperatures and barometric pressure for four days. Fumaroles near TELN and in the active crater exhibited increased flux since March. At times the crater fumaroles appeared to be emitting steam and gases in discrete clouds at intervals of several minutes. The most intense fumarole was in the upper NW corner of the crater (A on figure 7). Other fumaroles were observed in the lower NW corner, on the N, E, and SE crater walls, and in avalanche deposits on the S and SE parts of the crater floor. Fumarole A had temperatures of 150-160°C in July 1994 (figure 7). In the NE corner of the crater, fumarole B increased in temperature from 55°C in April to 174°C in July. Another fumarole area on the E side of the crater (C) had a temperature of 498°C in July, a significant increase from 246°C in 1990.

Eruptive activity. A relatively small explosive eruption at about 1645 on 31 July produced a gas-and-ash column that rose ~800 m above the summit. The light-gray ash cloud was driven SW by the wind, depositing about 2 mm of ash in the towns of Chichigalpa (20 km WSW), Quezalguaque (12.5 km SSW), and Posoltega (16 km SW) (figure 6). No seismic events were felt by residents near the volcano, but the sound of the explosion was heard at distances up to 10 km.

Following the 31 July eruption, phreatic activity continued in the next hours and days with varying intensity of gas emanation and ash expulsion. One of the strongest explosions, on 5 August, produced an ash column 1,200 m high. One phase of gas emission reached heights of 200-300 m above the crater rim. Gas also filled a valley W of the volcano with high concentrations of SO2, sometimes causing breathing problems for INETER scientists who traveled through the valley at a distance of ~2 km from the crater. Seismicity at shallow depths (~2 km) beneath the crater was recorded by TELN and four stations installed after the eruption began: telemetric stations TEL 2, 3, & 4, and local digital registration station TEL 5 (figure 7). The numerous weak events during the eruption were only recorded by the local seismic stations.

Chemical analyses of washed ash samples collected on different days indicated an increase of the SO42- and Cl- contents over time. Several very heavy rainfalls occurred during the eruptive period. Analyzed rainwater samples also showed high concentrations of SO42- with respect to Cl- and F2-, and a corresponding low pH level. Similar measurements two weeks before the eruption showed normal low concentrations of SO42- and Cl-.

Early eruption products consisted of very fine-grained, light-colored, blocky ash. INETER volcanologists believe that the ash was non-juvenile, and was ejected during phreatic or phreatomagmatic eruptions. Major explosions generally lasted for ~10-25 minutes. Early eruption columns were mostly white in color, and ranged from several hundred meters to 1,400 m above the vent. On 9 and 10 August, the ash was black, significantly darker than before, with correspondingly darker eruption plumes. The ash remained blocky and non-vesicular.On 10 August, 40-50 high-frequency seismic events were recorded, including one that lasted 4.5 hours. High-frequency events prior to 10 August occurred at a rate of ~70-90/day and were associated with more frequent explosions (10-20/day). The number of daily explosions also decreased to 6 on 10 August, including one major explosion that lasted for 16 minutes. An explosion at 1800 on 11 August generated a plume that rose 350 m, but only 16 high-frequency events were detected that day. On the early morning of 12 August one of the strongest explosions of this eruption occurred; activity then decreased throughout the day. By that evening the explosions had stopped and gas emanation and seismicity reached very low levels.

Seismicity had increased slightly by 16 August, five microseismic events were detected during 24 hours on 17-18 August, and on 20 August tremor lasted for 6.2 hours. However, no seismic events were detected on 21-22 August, and activity remained low as of 26 August.

On 23 August, Oto Matias (INSIVUMEH, Guatemala) arrived with a COSPEC instrument to assist INETER scientists in making SO2-flux measurements. Attempts to carry out COSPEC measurements of the SO2 concentration in the gas plume were made on 24 August, but low levels of gas emission and cloudy skies prevented good results.

Soil sampling. During three field surveys by FIU and INETER scientists in early June, >60 stations were deployed over 50 km2 to determine the concentration of radon (Rn), CO2, Hg, and He in soils. One identified anomaly had intensified between March and May/June 1994. This anomaly, ~750 m long and 250 m wide, surrounded the TELN seismic station. Along this anomaly, Hg values ranged from several tens of ppb to >2,900 ppb, He from 5,399 to 5,415 ppb, CO2 to 2.1 volume %, and Rn to 1,819 pico-Curies/liter.

San Jacinto Hot Springs. The village of San Jacinto, 9 km NE of the town of Telica and 2 km E of Santa Clara volcano, contains a field of boiling mudpots (BGVN 19:03). Soil samples for Hg and CO2 measurements were collected from the hydrothermal field in March and May/June 1994. The March samples contained CO2 concentrations up to 0.09 volume % and Hg from 6,710 to 21,512 ppb. The onset of the rainy season had resulted in an increase in both the size of the field and the steam flux since 9 March. Exploration for a new geothermal power plant was taking place approximately 250 m WNW.

Historical activity. Telica is a composite volcano located 19 km N of León at the NW end of a large volcanic complex. Known historical activity dates from a strong eruption that occurred in 1527-29. Strong activity was also noted in 1685, 1740-43, and at least 7 times in the 20th century. During several eruptions ash has damaged agricultural crops. In February 1982 several strong explosions generated ash columns of 3.5 km height and the ashfall affected nearby towns. The most recent eruption of Telica in November 1987 included Strombolian-type activity.

Eruptions in pre-historical times produced ash deposits of 50 cm thickness or more within a radius of 50 km. A volcanic hazard map (figure 9) suggests that ashfall poses the greatest threat to the local population. Lava flows have occurred, but with low frequency, most recently ~1,000 years ago. The hazard zone for pyroclastic eruptions lies within ~2 km of the crater. Lahars have occurred as a result of very strong eruptions during the rainy season.

Figure (see Caption) Figure 9. Volcanic hazards map of Telica. Hazard zones are shown for ashfall and tephra, lava flows, and column collapse. Courtesy of INETER.

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

Information Contacts: H. Taleno, L. Urbina, M. Navarro, O. Canales, C. Guzman, C. Buitrago, A. Izaguirre, Christian Lugo M. (Vulcanology); W. Strauch (Seismology); C. Urbina, and A. Acosta (Electronics), INETER, Managua; Peter C. La Femina, Michael Conway, and Andrew MacFarlane, Florida International Univ, USA.


Ulawun (Papua New Guinea) — July 1994 Citation iconCite this Report

Ulawun

Papua New Guinea

5.05°S, 151.33°E; summit elev. 2334 m

All times are local (unless otherwise noted)


White vapor emissions and low-frequency tremor

"The level of activity . . . was slightly lower in July . . . . The summit crater continued to emit mainly white vapour, of variable volume. Faint blue vapour emissions were seen on 3, 5, 9, and 20 July. No sounds or night glow were reported.

"Seismic activity . . . continued the pattern of previous months, with mainly sub-continuous, low-level, low-frequency tremor, and the occasional larger low-frequency earthquake. Only two high-frequency earthquakes were recorded during the month. Amplitude measurements and RSAM monitoring were made difficult at the start of the month by storm-generated noise. However, both showed a gradual increase through the month until about 23 July when there were sharp drops; gradual increases were again seen through the end of the month."

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

Information Contacts: B. Talai, R. Stewart, and C. McKee, RVO.


Unzendake (Japan) — July 1994 Citation iconCite this Report

Unzendake

Japan

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

All times are local (unless otherwise noted)


Lava lobe 13 grows endogenously but then nearly stops growing in late-July

Lobe 13 . . . grew endogenously at slow rates until late-July. Its final size was ~80 m long, 70 m wide, and 30 m high; it lies hidden behind the roughly 10x longer lobe 11, which forms the prominent bulge on figures 73 and 74.

Figure (see Caption) Figure 73. Sketch of the Unzen lava done showing features of the 22 July photograph (figure 74); view is roughly [from] the N. Vegetated surfaces are shown in black, undifferentiated dome, talus, pyroclastic-flow, and other deposits shown lightly shaded. Courtesy of S. Nakada.
Figure (see Caption) Figure 74. Photograph of the lava dome at Unzen, 22 July 1994. Taken from a helicopter looking [from] approximately N. Courtesy of S. Nakada.

In Unzen's summit area, the endogenous dome developed three E-W trending ridges along its top. The highest (central) ridge uplifted in early-July between two other ridges. The central ridge and a N ridge moved to the N at a rate of ~2 m/day during July, leaving behind the S ridge and increasing the width of a graben between them. The central ridge also rose vertically at a rate of <1 m/day. The E part of the central ridge consisted of brown-colored massive lava that was rounded, convex upward, and relatively smooth. The ridge was composed of massive lava squeezed from the interior of the dome, an effect also seen in April. When the lava reached the top of the ridge it broke and collapsed.

The ridges stopped moving N at the end of July. Occasionally there were small, low-density rockfalls to the SW in early- to mid-August. Owing to fragmentation, the massive lava of the central ridges decreased its height by ~20 m during the first two weeks in August, and at the same time the talus slope hardly advanced in any direction. These observations imply that for this two-week period in August an extremely low eruption rate (estimated at 4m3/day) prevailed.

During mid-July to early-August a continuous rain of N-directed rockfalls occurred when the N ridge became exposed at the cliff top. These rockfalls transformed into small pyroclastic flows, generally with run-out distances under 1 km. Pyroclastic flows were detected seismically at a station 1 km WSW of the dome and real-time monitoring of the dome was accomplished by four sets of visible and thermal infrared video cameras. During July this system detected 44 pyroclastic flows.

During most of July, microearthquakes beneath the dome generally took place <80 times a day. The total number of earthquakes in July was 2,488, roughly a 20% drop from the previous two months.

EDM by the JMA and the GSJ found that during late-June through mid-July the radial distance to one reflector on Unzen's N flank shortened rapidly, by tens of centimeters/day. The lack of confirmation from other reflectors suggested that the area in motion was of limited size.

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

Information Contacts: S. Nakada, Kyushu Univ; JMA.


Whakaari/White Island (New Zealand) — July 1994 Citation iconCite this Report

Whakaari/White Island

New Zealand

37.52°S, 177.18°E; summit elev. 294 m

All times are local (unless otherwise noted)


No eruptive activity, but new shifts in leveling and magnetic data

Routine monitoring visits on 23 April and 28 June 1994 found no evidence of any eruptive activity. On 23 April the floor of Princess Crater was occupied by a muddy pond that contained fresh landslide debris (see figure 21). The divide between Wade and Royce craters had been destroyed. Active fumaroles included those in TV1 Crater, and those escaping from beneath landslide debris in the Royce area.

Scientists who made brief trips on 12 and 15 May noted 5-10 m subsidence of the lake occupying the active vent area on the floor of Wade Crater; the lowered lake level persisted until at least 29 May. A triangulation survey on 28 June determined the lake to be 56 m below sea level and 92 m below the rim of the 1978/90 Crater Complex.

Deformation was surveyed in nearly ideal conditions on 28 June, achieving a good error of closure; the results showed that since 19 January 1994 a subtle but significant crater-wide uplift, typically 5-10 mm, has taken place. Stronger uplifts occurred at Donald Mound (+15 mm) and SE of Peg M (+21 mm). This kind of crater-wide inflation was last seen in the three years preceding the 1976-93 eruptions.

A magnetic survey of established sites revealed a pattern of net magnetic changes very similar to the two previous periods of measurements in 1993. A negative anomaly lay to the N of Donald Mound (-100 nT), and a positive one to the S (+60 nT). P. Rickerby noted that "these anomalies could be interpreted as resulting from shallow heating under Donald Mound (~50 m deep) and shallow cooling under TV1."

Seismicity recorded during January-June 1994 has generally showed little change; tremor in this interval has remained near background, though it has been present on 54% of the obtained records.

Geologic Background. The uninhabited Whakaari/White Island is the 2 x 2.4 km emergent summit of a 16 x 18 km submarine volcano in the Bay of Plenty about 50 km offshore of North Island. The island consists of two overlapping andesitic-to-dacitic stratovolcanoes. The SE side of the crater is open at sea level, with the recent activity centered about 1 km from the shore close to the rear crater wall. Volckner Rocks, sea stacks that are remnants of a lava dome, lie 5 km NW. Descriptions of volcanism since 1826 have included intermittent moderate phreatic, phreatomagmatic, and Strombolian eruptions; activity there also forms a prominent part of Maori legends. The formation of many new vents during the 19th and 20th centuries caused rapid changes in crater floor topography. Collapse of the crater wall in 1914 produced a debris avalanche that buried buildings and workers at a sulfur-mining project. Explosive activity in December 2019 took place while tourists were present, resulting in many fatalities. The official government name Whakaari/White Island is a combination of the full Maori name of Te Puia o Whakaari ("The Dramatic Volcano") and White Island (referencing the constant steam plume) given by Captain James Cook in 1769.

Information Contacts: T. Hunt, B. Scott, T. Kabayashi, and T. Tosha, IGNS, Wairakei; P. Rickerby, Victoria Univ, Wellington.

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