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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

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

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

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

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

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

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

Kikai (Japan) Ash explosion on 29 April 2020

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

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

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

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

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



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

Nyamuragira

DR Congo

1.408°S, 29.2°E; summit elev. 3058 m

All times are local (unless otherwise noted)


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

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

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

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

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

Information Contacts: Information contacts: Observatoire Volcanologique de Goma (OVG), Departement de Geophysique, Centre de Recherche en Sciences Naturelles, Lwiro, D.S. Bukavu, DR Congo; MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/exp.


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

Nyiragongo

DR Congo

1.52°S, 29.25°E; summit elev. 3470 m

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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


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

Kavachi

Solomon Islands

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

All times are local (unless otherwise noted)


Discolored water plumes seen using satellite imagery in 2018 and 2020

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

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

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

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

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

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

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


Kuchinoerabujima (Japan) — May 2020 Citation iconCite this Report

Kuchinoerabujima

Japan

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

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


Soputan (Indonesia) — May 2020 Citation iconCite this Report

Soputan

Indonesia

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

All times are local (unless otherwise noted)


Minor ash emissions during 23 March and 2 April 2020

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

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

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

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

Information Contacts: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as Indonesian Center for Volcanology and Geological Hazard Mitigation, CVGHM), Jalan Diponegoro 57, Bandung 40122, Indonesia (URL: http://www.vsi.esdm.go.id/); MAGMA Indonesia, Kementerian Energi dan Sumber Daya Mineral (URL: https://magma.vsi.esdm.go.id/); Darwin Volcanic Ash Advisory Centre (VAAC), Bureau of Meteorology, Northern Territory Regional Office, PO Box 40050, Casuarina, NT 0811, Australia (URL: http://www.bom.gov.au/info/vaac/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


Heard (Australia) — May 2020 Citation iconCite this Report

Heard

Australia

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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


Kikai (Japan) — May 2020 Citation iconCite this Report

Kikai

Japan

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

All times are local (unless otherwise noted)


Ash explosion on 29 April 2020

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

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

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

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

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

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

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


Fuego (Guatemala) — April 2020 Citation iconCite this Report

Fuego

Guatemala

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

All times are local (unless otherwise noted)


Ongoing ash explosions, block avalanches, and intermittent lava flows

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

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

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

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

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

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

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

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

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

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

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

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

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

Information Contacts: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia e Hydrologia (INSIVUMEH), Unit of Volcanology, Geologic Department of Investigation and Services, 7a Av. 14-57, Zona 13, Guatemala City, Guatemala (URL: http://www.insivumeh.gob.gt/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Washington Volcanic Ash Advisory Center (VAAC), Satellite Analysis Branch (SAB), NOAA/NESDIS OSPO, NOAA Science Center Room 401, 5200 Auth Rd, Camp Springs, MD 20746, USA (URL: www.ospo.noaa.gov/Products/atmosphere/vaac, archive at: http://www.ssd.noaa.gov/VAAC/archive.html); Crelosa, 3ra. avenida. 8-66, Zona 14. Colonia El Campo, Guatemala Ciudad de Guatemala (URL: http://crelosa.com/, post at https://www.youtube.com/watch?v=1P4kWqxU2m0&feature=youtu.be).


Ebeko (Russia) — June 2020 Citation iconCite this Report

Ebeko

Russia

50.686°N, 156.014°E; summit elev. 1103 m

All times are local (unless otherwise noted)


Frequent moderate explosions, ash plumes, and ashfall continue, December 2019-May 2020

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

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

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

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

Geologic Background. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. Blocky lava flows extend west from Ebeko and SE from the neighboring Nezametnyi cone. The eastern part of the southern crater contains strong solfataras and a large boiling spring. The central crater is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters, on the outer flanks of the cone, and in lateral explosion craters.

Information Contacts: Kamchatka Volcanic Eruptions Response Team (KVERT), Far Eastern Branch, Russian Academy of Sciences, 9 Piip Blvd., Petropavlovsk-Kamchatsky, 683006, Russia (URL: http://www.kscnet.ru/ivs/kvert/); Institute of Volcanology and Seismology, Far Eastern Branch, Russian Academy of Sciences (IVS FEB RAS), 9 Piip Blvd., Petropavlovsk-Kamchatsky 683006, Russia (URL: http://www.kscnet.ru/ivs/eng/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


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

Piton de la Fournaise

France

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

Information Contacts: Observatoire Volcanologique du Piton de la Fournaise, Institut de Physique du Globe de Paris, 14 route nationale 3, 27 ème km, 97418 La Plaine des Cafres, La Réunion, France (URL: http://www.ipgp.fr/fr); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Hawai'i Institute of Geophysics and Planetology (HIGP) - MODVOLC Thermal Alerts System, School of Ocean and Earth Science and Technology (SOEST), Univ. of Hawai'i, 2525 Correa Road, Honolulu, HI 96822, USA (URL: http://modis.higp.hawaii.edu/); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground); GEO Magazine (AFP story at URL: https://www.geo.fr/environnement/la-reunion-fin-deruption-au-piton-de-la-fournaise-200397); AFP (URL: https://twitter.com/AFP/status/1227140765106622464, Twitter: @AFP, https://twitter.com/AFP); Jeannie Curtis (Twitter: @VolcanoJeannie, https://twitter.com/VolcanoJeannie).


Sabancaya (Peru) — June 2020 Citation iconCite this Report

Sabancaya

Peru

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

All times are local (unless otherwise noted)


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

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

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

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

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

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

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

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

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

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

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

Geologic Background. Sabancaya, located in the saddle NE of Ampato and SE of Hualca Hualca volcanoes, is the youngest of these volcanic centers and the only one to have erupted in historical time. The oldest of the three, Nevado Hualca Hualca, is of probable late-Pliocene to early Pleistocene age. The name Sabancaya (meaning "tongue of fire" in the Quechua language) first appeared in records in 1595 CE, suggesting activity prior to that date. Holocene activity has consisted of Plinian eruptions followed by emission of voluminous andesitic and dacitic lava flows, which form an extensive apron around the volcano on all sides but the south. Records of historical eruptions date back to 1750.

Information Contacts: Observatorio Volcanologico del INGEMMET (Instituto Geológical Minero y Metalúrgico), Barrio Magisterial Nro. 2 B-16 Umacollo - Yanahuara Arequipa, Peru (URL: http://ovi.ingemmet.gob.pe); Buenos Aires Volcanic Ash Advisory Center (VAAC), Servicio Meteorológico Nacional-Fuerza Aérea Argentina, 25 de mayo 658, Buenos Aires, Argentina (URL: http://www.smn.gov.ar/vaac/buenosaires/inicio.php); Global Sulfur Dioxide Monitoring Page, Atmospheric Chemistry and Dynamics Laboratory, NASA Goddard Space Flight Center (NASA/GSFC), 8800 Greenbelt Road, Goddard, Maryland, USA (URL: https://so2.gsfc.nasa.gov/); MIROVA (Middle InfraRed Observation of Volcanic Activity), a collaborative project between the Universities of Turin and Florence (Italy) supported by the Centre for Volcanic Risk of the Italian Civil Protection Department (URL: http://www.mirovaweb.it/); Sentinel Hub Playground (URL: https://www.sentinel-hub.com/explore/sentinel-playground).


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/).

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Bulletin of the Global Volcanism Network - Volume 15, Number 08 (August 1990)

Managing Editor: Lindsay McClelland

Aira (Japan)

Continued vigorous explosions

Arenal (Costa Rica)

More frequent explosions; lava flow remains active

Asamayama (Japan)

Seismicity fluctuates; steam emission remains strong

Asosan (Japan)

Mud, water, and steam ejected from lake in active vent

Azufral (Colombia)

Fumaroles near young summit domes; extra-caldera ignimbrites may be only hundreds of years old

Bagana (Papua New Guinea)

Summit block lava extrusion and plume emission; reporting problems

Chiles-Cerro Negro (Colombia-Ecuador)

H2S-rich hot springs at Pleistocene volcano

Eldey (Iceland)

Strong seismicity SW of May 1989 swarm; possible new lava in 1989 swarm area

Galeras (Colombia)

Small tephra emissions, perhaps with minor magmatic component; strong seismicity and fumaroles

Kilauea (United States)

Continued East Rift lava production; two houses destroyed; three brief eruptive pauses

Kusatsu-Shiranesan (Japan)

Seismicity remains strong

Langila (Papua New Guinea)

Continued moderate Vulcanian activity

Lengai, Ol Doinyo (Tanzania)

Continued lava extrusion onto crater floor

Manam (Papua New Guinea)

Small ash eruption follows inflation and seismic changes

Monowai (New Zealand)

Extensive zone of sulfurous discolored water; bathymetric data show two plumes

Poas (Costa Rica)

Continued fumarolic activity

Popocatepetl (Mexico)

Most nearby earthquakes tectonic, but a few small B-type events detected

Purace (Colombia)

Sulfur-rich summit fumaroles and flank hot springs

Rabaul (Papua New Guinea)

Seismicity remains at background

Ruapehu (New Zealand)

Crater Lake temperature increases; tremor resumes; inflation

Ruiz, Nevado del (Colombia)

Frequent ash emission with associated tremor; ashfall to 30 km; hot springs described

Stromboli (Italy)

Strong explosions; one crater filled by tephra

Ulawun (Papua New Guinea)

Weak vapor emission and seismicity

Unzendake (Japan)

Seismicity declines slightly

Vulcano (Italy)

High fumarole temperatures and geochemical changes; seismicity suggests complex fumarolic system

Whakaari/White Island (New Zealand)

Block eruption; significant morphologic changes in 1978 Crater



Aira (Japan) — August 1990 Citation iconCite this Report

Aira

Japan

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

All times are local (unless otherwise noted)


Continued vigorous explosions

During August, 20 explosions (with a maximum ash cloud height of 3,000 m on the 23rd) were recorded . . . . A monthly total of 2,307 g/m2 of ash was deposited 10 km W of the crater.

On 28 August at 0230, a large explosion ejected many blocks to the middle flank of the volcano. Twenty lightning flashes were seen in the volcanic cloud. Two car windshields were broken by lapilli 4 km from the summit and two blocks, roughly 60 cm across, fell 3 km S of the summit. No eruption-related damage had been reported since 1 May.

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) — August 1990 Citation iconCite this Report

Arenal

Costa Rica

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

All times are local (unless otherwise noted)


More frequent explosions; lava flow remains active

An average of 24 explosions/day, with a maximum of 41 (12 August), were recorded during August; June and July averaged 20 explosions/day. The Strombolian explosions ejected material to 1,000 m above the crater. "Fountains of bombs," without corresponding explosions, were noted 14 and 17 August. In addition to the explosions, tremor activity increased, especially between 17 and 21 August. Crater gas emissions appeared to be water-rich and an active lava flow on the NW flank reached 1,200 m elevation.

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: G. Soto, ICE.


Asamayama (Japan) — August 1990 Citation iconCite this Report

Asamayama

Japan

36.406°N, 138.523°E; summit elev. 2568 m

All times are local (unless otherwise noted)


Seismicity fluctuates; steam emission remains strong

Although seismicity remained at high levels following the multiple ash emissions on 20 July (15:07), the number of earthquakes fluctuated, decreasing after mid-August, increasing 28 August to a peak 31 August-2 September, then decreasing as of 10 September. During August, 103 earthquakes (down from 167 in July) primarily located under the summit, were recorded. Of the 36 recorded tremor episodes, the majority (25) occurred on 30 August after tremor was absent 3-28 August. Steam plume heights . . . remained high as of 10 September.

Geologic Background. Asamayama, Honshu's most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern Maekake cone forms the summit and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofuyama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake, capped by the Kamayama pyroclastic cone that forms the present summit, is probably only a few thousand years old and has an historical record dating back at least to the 11th century CE. Maekake has had several major plinian eruptions, the last two of which occurred in 1108 (Asamayama's largest Holocene eruption) and 1783 CE.

Information Contacts: JMA.


Asosan (Japan) — August 1990 Citation iconCite this Report

Asosan

Japan

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

All times are local (unless otherwise noted)


Mud, water, and steam ejected from lake in active vent

Vent 892 on the NE floor of Crater 1 had been covered by a pool of water since the last noted ash ejection in the crater on 30 June. Frequent mud and water ejections, and white steam emissions occurred during July and August. A plume containing small amounts of ash, intermittently ejected to 100 m from a vent in the SW part of Crater 1, was noted along with strong rumbling during a visit 30 August. The number of tremor episodes gradually decreased toward the end of August and tremor amplitude was at low levels.

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.


Azufral (Colombia) — August 1990 Citation iconCite this Report

Azufral

Colombia

1.08°N, 77.68°W; summit elev. 4070 m

All times are local (unless otherwise noted)


Fumaroles near young summit domes; extra-caldera ignimbrites may be only hundreds of years old

"Azufral caldera, with associated dome complex, was visited during July and August 1990. The major goal of current research, by the Univ de Montréal, is to map the stratigraphy of the caldera-filling dome sequence and the very young ignimbrites, distributed primarily S and E of the complex. Within the summit caldera, a lake (Laguna Verde) had a temperature of 8°C and pH of 2.4. The lake was a distinct clear emerald green, notably not the opaque milky green of an extremely acid lake such as at Poás, Costa Rica. The hottest springs found on the NE edge of the lake had a temperature of 54°C and pH of 2.6. More acid vents must be located beneath the lake to produce its low pH. Giggenbach-type samples were collected from the lake-edge bubbles. The highest fumarole temperatures, encountered on the youngest rhyodacite dome, were 87°C. Extensive alteration was evident, usually near the base of the domes. Bedded tuffs and tuff breccias, on the NE side of the lake, appeared to be related to hydrothermal explosions. The relative stratigraphy of the domes was indicated by their youthful morphology, with those on the E side appearing to be the youngest. A series of wave-cut terraces around the lake extended to 4-5 m above the present lake level. Between early July and August, lake level dropped by ~ 5 cm, probably in response to the dry season that normally begins in July. Outside the caldera the rhyodacite ignimbrites appeared, from stratigraphy and erosion, to be young - perhaps less than several hundred years. Fumarolic activity at Azufral does not appear to be significantly influenced by volcanic processes."

Geologic Background. Azufral stratovolcano in southern Colombia, also known as Azufral de Túquerres, is truncated by a 2.5 x 3 km caldera containing a Holocene rhyodacitic lava-dome complex. A crescent-shaped lake, Laguna Verde, occupies the NW side of the caldera. Nearly a dozen lava domes are present, the latest of which were formed about 3600 years ago and have active fumaroles. Azufral rocks are more silicic than those of nearby Colombian volcanoes; an apron of rhyodacitic pyroclastic-flow deposits rings the volcano. The last known eruption took place about 1000 years ago.

Information Contacts: S. Williams, Louisiana State Univ; J. Stix and E. Fontaine, Univ de Montréal.


Bagana (Papua New Guinea) — August 1990 Citation iconCite this Report

Bagana

Papua New Guinea

6.137°S, 155.196°E; summit elev. 1855 m

All times are local (unless otherwise noted)


Summit block lava extrusion and plume emission; reporting problems

"Due to social unrest and political isolation on Bougainville Island Island, instrumental data is no longer being recorded and no reliable reports of visual observation were received. From the sparse reports of observations received between 12 and 27 August, it is presumed that the volcano is still extruding a blocky lava flow from its summit crater with accompanying moderate to strong white to grey plumes, summit night glow, and numerous rockfalls."

Geologic Background. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50 m thick with prominent levees that descend the flanks on all sides.

Information Contacts: I. Itikarai and C. McKee, RVO.


Chiles-Cerro Negro (Colombia-Ecuador) — August 1990 Citation iconCite this Report

Chiles-Cerro Negro

Colombia-Ecuador

0.817°N, 77.938°W; summit elev. 4698 m

All times are local (unless otherwise noted)


H2S-rich hot springs at Pleistocene volcano

"In April 1988 and again on 3 April 1990 we visited two hydrothermal springs [on Chiles] and collected samples. The first, La Calera, is a developed hot spring with baths just W of the town of Chiles and 8 km E of the crater of Chiles volcano, at 3,180 m elev. The maximum temperature was 40°C and pH was 6.2. No significant sulfur deposition was observed at the natural source of hot water, ~ 100 m uphill from the commercial baths. The second site, La Hedionda, was unsuccessfully developed as a tourist bath area, reputedly failing because of deadly levels of H2S. It is 3.5 km E of the crater, at 3,470 m elevation. The uppermost hot spring, with a temperature of 54°C and pH of 5.1, was sampled. These acid sulfate springs were actively depositing native sulfur and had an almost overwhelming odor of H2S. Fumarole samples were collected at both springs. No observations were made, on either visit, of the summit area, which was always covered by clouds. The observations at Chiles are consistent with a stable system, dominated by hydrothermal processes."

Geologic Background. The Chiles-Cerro Negro volcanic complex includes both the Pleistocene Chiles and the Cerro Negro de Mayasquer stratovolcanoes astride the Colombia-Ecuador border. Cerro Negro has a caldera open to the west, with andesitic and dacitic lava flows of possible Holocene age (Hall 1992, pers. comm.) and solfataras on the shore of a small crater lake. An eruption reported in 1936 may have been from Reventador (Catalog of Active Volcanoes of the World). The higher, glacier-covered summit of Chiles, about 4 km ESE of Cerro Negro, last erupted about 160,000 years ago, but it has a caldera open to the north with hot springs and an active hydrothermal system on its eastern flank.

Information Contacts: S. Williams, Louisiana State Univ; J. Stix and E. Fontaine, Univ de Montréal.


Eldey (Iceland) — August 1990 Citation iconCite this Report

Eldey

Iceland

63.733°N, 23°W; summit elev. 70 m

All times are local (unless otherwise noted)


Strong seismicity SW of May 1989 swarm; possible new lava in 1989 swarm area

A 9 September earthquake swarm has been located on the Reykjanes Ridge, site of a large number of earlier swarms, including one in May-June 1989 (Nishimura and others, 1989, and 14:5). Bergman and Solomon (1990) made a detailed analysis of spatial, temporal, and other characteristics of Mid-Atlantic Ridge earthquake swarms detected by worldwide seismic networks. Their results indicated that the swarms are tectonic in origin, and not representative of volcanic activity, although not necessarily exclusive of it. Work by Shor et al. (1990) suggests that there has been recent volcanic activity at the site of the May 1989 swarm, potentially concurrent with the swarm activity.

A joint venture of the Hawaii Institute of Geophysics (Alex Shor and Clyde Nishimura) and the Naval Research Laboratory (Peter Vogt and Michael Czarnecki), aboard the RV Ewing (Lamont-Doherty Geological Observatory), visited the May 1989 swarm site during July (S,hor et al., 1990). Simultaneous SeaMARCII sidescan imagery and Hydrosweep multibathymetry was used to examine a 1,000 km2 area of the seafloor at depths ranging from 700 to 1,350 m. Gravity and magnetics studies were also conducted.

A probable young lava flow was identified, centered near 59.47°N, 29.43°W, within the error radius of sonobuoy-based epicenter locations from the May 1989 swarm. The apparent lava flow (roughly 4 x 2 km) extends from the E margin of the neo-volcanic zone (NVZ) S over sedimented and faulted terrain and is bounded on the E by an inward-facing normal fault with an 80 m throw. The region is heavily faulted (faults are W-facing, spaced

During the investigation of the Reykjanes Ridge, the Ewing followed and surveyed the ridge axis from 52.8°N to 63.0°N. More than 100 discrete volcanic cones were identified within one 65-km-long, 10-km-wide strip, with many additional cones on the flanks.

On 9 September, six earthquakes were recorded originating near 56.7°N and 34.4°W (table 1), about 500 km SW along the ridge from the May 1989 swarm (figure 2). Preliminary planning and requests have been made to conduct an airborne sonobuoy mission similar to that employed during the May 1989 swarm. Pre-swarm seafloor imaging of the site was obtained during the July ridge axis survey. A second Ewing mission to the site of the May 1989 swarm (Lindsay Parson, Institute of Oceanographic Sciences, U.K.), had already been planned for October and should complete "before and after" views of the September swarm site.

Table 1. Earthquake epicenters and magnitudes for Reykjanes Ridge earthquakes, 9 September 1990. Courtesy of the USGS National Earthquake Information Center.

Time Location Magnitude (mb)
0017 56.94°N, 34.29°W 5.0
0030 56.1°N, 34.5°W 4.8
0215 56.78°N, 34.37°W 5.5
0625 56.60°N, 34.33°W 5.2
0635 56.65°N, 34.59°W 5.1
1235 56.75°N, 34.38°W 4.8
see figure caption Figure 2. Locations of earthquake swarms on the Reykjanes Ridge, after Bergman and Solomon (1990). The approximate site of the September 1990 swarm has been added.

References. Bergman, E.A., and Solomon, S.C., 1990, Earthquake swarms on the Mid-Atlantic Ridge: products of magmatism or extensional tectonics?: JGR, v. 95, p. 4943-4965.

Nishimura, C.E., Vogt, P.R., Smith, L., and Boyd, J.D., 1989, Investigation of a possible underwater volcanic eruption on the Reykjanes Ridge by airborne sonobuoys and AXBT's (abs.): Eos, v. 70, p. 1301.

Shor, A.N., Nishimura, C.E., Czarnecki, M., and Vogt, P.R., 1990, Lava extrusion from the 1989 Reykjanes Ridge seismic swarm? probably yes (SeaMARCII) (abs.): Eos, v. 71 (Fall AGU Abstract Volume).

Geologic Background. The Eldey volcanic system is located on the northernmost part of the Reykjanes Ridge and is submarine with the exception of Eldey Island and the skerries (small rocky islands) Eldeyjardrangur, Geirfugladrangur, and Geirfuglasker. Maximum water depth within the system is about 250 m. Eldey has been moderately active in Holocene time. Characteristic activity consists of explosive submarine basaltic eruptions. Six small eruptions have been located within this system during the last 1,100 years, the last occurring in 1926 CE.

Information Contacts: R. Stefánsson, Icelandic Meteorological Office; P. Vogt, Naval Research Laboratory; B. Presgrave, NEIC.


Galeras (Colombia) — August 1990 Citation iconCite this Report

Galeras

Colombia

1.22°N, 77.37°W; summit elev. 4276 m

All times are local (unless otherwise noted)


Small tephra emissions, perhaps with minor magmatic component; strong seismicity and fumaroles

Ash emissions and geology. Small ash emissions occurred 2 and 15 August. The activity on 2 August was preceded by an increase in the number of long-period earthquakes (figure 25) and accompanied by low-frequency tremor. Explosions ejected blocks as large as 15 cm in diameter up to the S-SW rim of the inner crater, and deposited a 3-4-cm layer of fine gray ash over a tight sector N and W of the crater. Seismic signals and the dispersion of deposits suggested that there could have been as many as three explosive events. S. Williams reported that "close examination of the 2 August ash under the petrographic microscope revealed a small (<1%) component of shiny fresh glass shards and enclosed crystals. The remainder of the deposit was entirely composed of lithic material, crystal fragments, and accessory material. Within the glassy specimens, there appeared to be two different types – one brown and the other (less common) clear. The petrographic characteristics of these shards was consistent with their having been erupted as fresh magmatic material."

Figure (see Caption) Figure 25. Number of earthquakes recorded/day at Galeras, July-August 1990. Lower (solid) line shows high-frequency events and upper (dashed) line represents low-frequency and long-period events. Courtesy of INGEOMINAS.

The 2 August explosions took place at the "Las Portillas" fumarolic area at the W wall within the inner crater. An increase in size of the fumaroles was noted.

Seismic activity. Long-period earthquakes increased in number during August, to the highest level since the initiation of monitoring at the volcano. Frequencies of the long-period events ranged from 1.25 to 1.67 Hz. Some were monochromatic and others alternated with high frequencies. Occasionally, they were linked to low-frequency tremor signals. The majority of the tremor episodes were of low frequency, with less frequent spasmodic tremor; signals often had poorly defined forms. Tremor episodes were associated with ash emissions on 2 and 15 August, and had up to 16 cm2 of reduced displacement (2 August).

High-frequency earthquakes were concentrated W of the crater at 2-5 km depth; others were located to the SE at similar depths (figure 26). A M 3.6 earthquake (the largest yet recorded at Galeras) occurred on 30 August, 4 km SE of the crater and at close to 4 km depth. A number of dynamic parameters of the high-frequency sources were determined: seismic momentum ranged from 1018-1021 dyne-cm with an average of 1020 dyne-cm, fault longitudes ranged from 125 to 325 m with an average of 200 m, fault dislocations and stress drop ranged from 0.1 cm and 1.5 bars (respectively) for an M 1.2 earthquake to 58.3 cm and 796 bars for an M 2.2 earthquake.

Figure (see Caption) Figure 26. Epicenter map (top) and E-W cross-section showing focal depths (bottom) of 76 high-frequency earthquakes recorded at Galeras, August 1990. Courtesy of INGEOMINAS.

Deformation. There were no significant changes in deformation, with the exception of peaks noted 2 km E of the crater (Peladitos EDM station) on 17 and 19 August. No clear relationship with seismicity was evident.

Gas geochemistry. The SO2 flux, as measured by COSPEC, fluctuated between 1,343 and 3,023 t/d during 10 measurements in August. The following is a report by S. Williams.

"The Las Deformes fumarole, ~10 m outside of the S lip of the inner crater, appeared to be roughly 25% larger than it was when visited in December 1989. Temperatures as high as 243°C were measured, where the maximum in December was 225°C. The fumarole had a very high-pressure noisy output of gas, with a very high SO2 content. Sublimate minerals within the highest temperature zones of the fumarole were black shiny crystals. Unfortunately, none were successfully collected. The Calvache fumaroles, NE of the crater, had maximum temperatures of 88°C, unchanged from December 1989. Increased activity was noted around the Calvache fumaroles. Giggenbach-type samples were collected from both fumaroles and condensate was collected at Las Deformes. The inner crater fumaroles could not be approached closely, due to the large volumes of gas and poor visibility. Their overall appearance was consistent with significantly higher temperatures (>500°C?) than encountered outside of the crater. At Pandiaco hot spring at the E foot of the volcano (in Pasto) the pH was 6.1 and temperature was 30°C, unchanged from December 1989 and April 1988 (when the site was first visited).

"A mudflow occurred on 28 April, apparently triggered by a heavy rain with no relation to eruptive activity. The flow swept down the river draining Galeras on its breached W side and went past Consacá (10 km W of the crater), to the Río Guitara. At the bridge just above Consacá, the mudflow scoured up to 5 m above the normal banks.

"Galeras is still in a very (and perhaps increasingly) active state, dominated by magmatic processes."

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: INGEOMINAS-OVP; S. Williams, Louisiana State Univ.


Kilauea (United States) — August 1990 Citation iconCite this Report

Kilauea

United States

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

All times are local (unless otherwise noted)


Continued East Rift lava production; two houses destroyed; three brief eruptive pauses

Kilauea's . . . eruption continued through August. Lava from Kupaianaha vent (figure 71) advanced through tubes and entered the ocean along a broad front. Lava breakouts occurred from many parts of the tube system. The resulting flows destroyed one house in Kalapana (and started brush fires that burned another) and built small shield-like features on the upper part of the main tube near the base of Kupaianaha's shield. Three brief pauses in activity were noted, bringing the year's total to nine.

Figure (see Caption) Figure 71. Lava produced by Kilauea's East rift zone eruption, 1983-90. Arrows indicate paths of recent flows, and crosses mark inflated areas at the base of the Kupaianaha shield. The locations of seismometers STC and KLC are indicated, as is the epicenter of the 8 August earthquake.

Eruptive pause, 30 July-1 August. Most surface activity slowed to a halt on 30 July, although lava flows at the coast showed little evidence of the pause, and by 2 August half of Kaimu beach (figure 70) was covered by lava. The most direct seismic expression of previous eruptive pauses had been the very low amplitude of volcanic tremor registered on seismometers near the vents. Tremor amplitude on the station nearest Kupaianaha (KLC) remained consistently low, but dropped near Pu`u `O`o (at station STC) by about a factor of two to a very quiet background level at about 1200 on 1 August. Background noise at STC remained low for ~12 hours, allowing detection of frequent small bursts of seismicity. Seismologists believed that these might be interpreted as small landslides or other crustal adjustments around Pu`u `O`o while local flow rates were diminished. During the same period of low seismicity on the East rift zone, from about 1200 to 2300 on 1 August, summit volcanic tremor was at high amplitude.

Eruption resumes, 2-8 August. The resumption of eruptive activity on 2 August was marked by a sharp increase in microearthquake activity beneath the summit that began as tremor background suddenly decreased and summit ground tilt sharply increased. The peak of the summit microearthquake swarm was recorded between 1 August at 2300 and 2 August at 0200. Tremor amplitude recorded near Pu`u `O`o gradually increased to levels registered during earlier periods of surface activity. Lava reoccupied the "Woodchip" tube system down to Kalapana. Initial sticky pahoehoe breakouts became more fluid later in the day and began to move down the tube system toward Kaimu. Numerous small breakouts observed in the Kalapana area by 6 August began to cover more land on the perimeter of the flow field. A surface breakout on the 7th advanced W of Kaimu Bay and entered the ocean. The next day, a large breakout below the coast highway quickly began to fill the area between the highway and inflated flows below it, threatening the road.

Eruptive pause, 8-9 August. Another eruptive pause began late 8 August. At the summit, a sharp decrease in ground tilt and a sharp increase in background volcanic tremor were preceded by a vigorous burst of long-period seismicity that began on 8 August at about 2100 and stopped abruptly at about 0400 the next morning. A M 4.9 earthquake was recorded in the East rift zone on 8 August at 1606 (figure 71). Tremor amplitudes registered near Kupaianaha and Pu`u `O`o remained unchanged. By 10 August, activity behind the active ocean entries had diminished, and breakouts along flow margins were viscous and of low volume.

Eruption resumes briefly, 10-12 August. Microearth- quake activity beneath the summit was slightly elevationated during the 24 hours beginning at 0900 on 10 August and a sharp increase in summit tilt was measured the same morning, probably reflecting the resumption of magma and lava movement. The eruption resumed on the 10th, and the next day a large breakout was noted from the "Woodchip" tube at 35 m (120 ft) elevation in the upper part of Kalapana, above some houses that had been spared by earlier flows. By afternoon, lava was 100 m from the nearest home, but the flow front advanced only another 50 m before stagnating on 13 August. That day (13th) several other breakouts were noted in Kalapana along the "Woodchip" tube system.

Third eruptive pause, 12-14 August, and subsequent seismicity. On the morning of 12 August, a sharp drop in summit tilt again coincided with the onset of stronger summit tremor. However, these changes were not preceded by significantly increased long-period seismicity beneath the summit. Tremor amplitudes near Pu`u `O`o decreased during the evening of 13 August, and through much of the next day the reduction in background tremor again made it possible to observe very small discrete events. Summit tilt reversed as inflation resumed during the afternoon of 14 August and tremor amplitude dropped. At about 1500, summit microearthquake activity increased, remaining elevationated through 18 August. Tremor amplitude near Pu`u `O`o gradually increased and by the morning of the 16th had returned to levels comparable to those during obvious surface activity. For much of the rest of the month, summit and East rift zone seismicity fluctuated around low average levels, but microearthquake activity approximately doubled 25-31 August.

Renewed lava production from 15 August. A significant decrease in the volume of lava entering the ocean was noted on 15 August, perhaps a delayed response to the pause. However, lava was attempting to reoccupy the tube system upslope, and a large aa/pahoehoe flow seen at 90 m (300 ft) elevation on 15 August destroyed one of the few houses remaining in Kalapana on the 20th. A large channelized aa flow broke out of the primary Kalapana tube system in the main flow field about 15 August. By the 21st, this flow had reached 50 m (160 ft) elevation but had not turned toward Kalapana. A large surface flow broke out of the "Woodchip" tube in Kalapana on 16 August, and by the 18th had crossed Hwy 130, cutting off access to a home and ranch above the highway.

Activity in Kalapana slowed 21-27 August. Surface flows generally remained on top of earlier lava, with some small breakouts burning vegetation on the edge of the flow field near the end of Hwy 130. Lava continued to enter the ocean along a broad front (between Right Point and the Harry K. Brown Park area). By the 27th, no surface activity was visible in the Kalapana area and only the ocean entry at Right Point remained active. On 28 August, a fluid sheet flow broke out of the "Woodchip" tube (just below Hwy 130) and advanced toward the fault scarp bordering Kalapana Gardens. Five homes isolated by previous flows were between the scarp and the ocean. The flow destroyed one home on the 30th and set off brush fires that burned another; the fires came within a couple of meters of the remaining three homes before going out. Another flow that broke out on 29 August followed the E edge of the former Kalapana Gardens subdivision. By 2 September, the two flows had merged, but were only producing small ooze-outs. The volume of lava entering the ocean then appeared to increase, and by 3 September several entries were active (between Right Point and the former canoe landing).

Near-vent lava breakouts. Activity increased at higher elevations during August. Several fluid pahoehoe flows were noted at the base of Kupaianaha shield on 16 August. The flows continued along the edge of the Kupaianaha flow field, reaching 500 m (1,700 ft) elevation by the 25th. Breakouts from an inflated area at the shield's base were observed the same day. By 2 September, four large inflated areas (marked x on figure 71) had developed over the tube that transports lava from Kupaianaha to 550-580 m (1,800-1,900 ft) elevation. Numerous shelly pahoehoe flows broke out from the inflated areas until they began to resemble small shields. The lava pond at Kupaianaha remained sealed over, but lava was noted in a collapse pit 50-60 m SE of the pond.

Lava ponds in Pu`u `O`o. Three kilometers uprift, two active lava ponds were noted ~75 m below the rim of Pu`u `O`o crater on 22 August. Lava from the E pond was seen overflowing and draining into the W pond on the 28th, producing a large lava river across the crater floor. Throughout the week, observers noted similar activity in the reverse direction, with lava from the W pond overflowing and feeding the E pond. Since 26 August, frequent gas-piston signatures have been recorded by the seismometer nearest Pu`u `O`o, with quiet periods of up to 30 minutes terminated by a strong seismic burst.

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. Moulds and P. Okubo, HVO.


Kusatsu-Shiranesan (Japan) — August 1990 Citation iconCite this Report

Kusatsu-Shiranesan

Japan

36.618°N, 138.528°E; summit elev. 2165 m

All times are local (unless otherwise noted)


Seismicity remains strong

During August, 171 earthquakes . . . and 35 tremor episodes . . . were recorded. Tremor amplitude ranged from 0.0 to 1.3 [µm].

Geologic Background. The Kusatsu-Shiranesan complex, located immediately north of Asama volcano, consists of a series of overlapping pyroclastic cones and three crater lakes. The andesitic-to-dacitic volcano was formed in three eruptive stages beginning in the early to mid-Pleistocene. The Pleistocene Oshi pyroclastic flow produced extensive welded tuffs and non-welded pumice that covers much of the E, S, and SW flanks. The latest eruptive stage began about 14,000 years ago. Historical eruptions have consisted of phreatic explosions from the acidic crater lakes or their margins. Fumaroles and hot springs that dot the flanks have strongly acidified many rivers draining from the volcano. The crater was the site of active sulfur mining for many years during the 19th and 20th centuries.

Information Contacts: JMA.


Langila (Papua New Guinea) — August 1990 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)


Continued moderate Vulcanian activity

"Moderate Vulcanian activity involving Crater 3 continued. Crater 3 . . . was releasing a plume of white vapour with frequent ash-laden clouds accompanied by weak Vulcanian explosions. The largest of these explosions (recorded by the nearby seismometer) totaled as many as 35/day. Ashfalls were reported in areas N and NW of the volcano. Rumbling noises were heard on 7 August and glows were observed on the 13th and 18th, associated with weak explosions.

"Meanwhile, emissions from Crater 2 consisted of white with occasionally blue vapour. Steady weak night glows were occasionally observed."

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: I. Itikarai and C. McKee, RVO.


Ol Doinyo Lengai (Tanzania) — August 1990 Citation iconCite this Report

Ol Doinyo Lengai

Tanzania

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

All times are local (unless otherwise noted)


Continued lava extrusion onto crater floor

The volcano was visited twice in July, during a hike to the crater rim on 3 July by Thad Peterson and others, and an overflight on 9 July by L. Eshelman and G. Price. No liquid lava was visible on 3 July, but apparent heat-shimmering was observed above vent T5/T9 (now almost level with the E rim of the crater) and a surf-like roar was heard emanating from a source on the NE side of the crater. A strong sulfur odor originating from the N rim (near cone C) was reported during the overflight.

Comparison of photos taken by Eshelman during the 9 July overflight (figure 17) with those from a 2 May overflight indicated changes in lava flow and cone morphology . . . . Fresh lava, of various shades of mid to dark gray suggesting emission during the previous few weeks, covered roughly 90% of the crater floor. The remaining 10% was covered by older, white and pale gray lava. T5/T9, a large broad cone with a blunt peak, continued to be the primary source of lava, although it remained approximately the same size and shape. Fresh, dark gray lava flows extended from inconspicuous vents on the lower N, NE, and SW slopes of T5/T9, covering T10, surrounding H6, T8, T4/T7, and T11, and continuing S through the saddle M1M2. The youngest flows, F16 and F17, may have been liquid 9 July. A dark mark on T5/T9's N slope suggested a large vertical vent and almost the entire cone was dark gray, probably coated with fresh spatter from small vents on the upper slope.

Figure (see Caption) Figure 17. Active crater at Ol Doinyo Lengai, 9 July 1990, looking W (top) and SE (bottom). Dark areas show fresh lava flows. Tracings of oblique airphotos taken by L. Eshelman; courtesy of C. Nyamweru.

The enlarged cone at the E end of T4/T7, newly designated as T14, was medium gray in color and had a number of large cracks on its slopes. It did not appear as fresh as the top of T5/T9, so it was believed to have formed in May or early June. T8 remained unchanged in shape since 2 May, but an increase in yellow sulfur deposition was noted. T11 was unchanged and appeared inactive. Cones along the crater walls (A5, C1, and D), appeared unchanged and showed no signs of fresh lava.

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

Information Contacts: C. Nyamweru, Kenyatta Univ.


Manam (Papua New Guinea) — August 1990 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)


Small ash eruption follows inflation and seismic changes

"A relative build-up of activity resulted in a small ash eruption from Southern Crater on 28 August. Prior to the 28th, both craters emitted weak white vapour but on 15-17 and 20 August, Southern Crater released emissions of blue vapour, low in volume. Weak low rumbling noises were heard from Southern Crater on the 17th. From 11 August, small-amplitude harmonic tremor was recorded with occasional large B-type earthquakes occurring after the 16th. At 1300 on the 28th, Southern Crater started to forcefully expel a dark column of ash to 500-600 m above the crater, accompanied by a sub-continuous weak rumbling sound with associated strong harmonic tremor. The emission decreased in vigour after 1345 and ended by 1415. A light ashfall occurred on the SW part of the island. Interestingly, a week before the ash eruption, the daily number of microearthquakes dropped from an average of 1000 to 500, and the seismic amplitude dropped by almost half. A 'normal' level of activity returned rapidly after this short eruptive phase and both Southern and Main Craters were again releasing very weak plumes of thin white vapours with a weak blue vapour plume from Southern Crater.

"Tilt measurements at Tabele Observatory showed a definite inflationary trend since late June and had accumulated up to 6 µrad by the end of August (and thus had more than recovered the deflation of April-May; 15:4-5)."

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: I. Itikarai and C. McKee, RVO.


Monowai (New Zealand) — August 1990 Citation iconCite this Report

Monowai

New Zealand

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

All times are local (unless otherwise noted)


Extensive zone of sulfurous discolored water; bathymetric data show two plumes

A sharply defined zone of brown water extended W from the seamount's summit area during a visit by the research vessel HMNZS Tui on 13 August between 0800 and 1400. A strong sulfur smell was noted but no bubbles were visible. The surface temperature in discolored water 400 m from the plume's origin was 2.0 ± 0.5°C higher than that of the surrounding sea water. At 9 km from the summit, the plume of discolored water was ~3.7 km wide.

An attempt to contour the bathymetry of the top 500 m of the seamount (figure 1) was hampered by intermittent availability of GPS satellite fixes. Southern slopes appeared to have a regular cone shape, but the N slopes, where ship navigation was based on inputs from a gyrocompass and doppler log, appeared distorted to the NE. A minimum depth of 100 m was measured. Two vertical plumes extended to the surface.

Figure (see Caption) Figure 1. N-S profile across the summit of Monowai Seamount using a 45-kHz sounder. Vertical exaggeration 6:1. Depths are in meters. Two vertical plumes (not seen on the 12 kHz sounder) extend from the summit area to the surface. Courtesy of the Defence Scientific Establishment.

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

Information Contacts: Lt. Cdr. Owen Hanley, HMNZSTui, Auckland Naval Base, Auckland; L. Hall, Defence Scientific Establishment, Auckland Naval Base, Auckland.


Poas (Costa Rica) — August 1990 Citation iconCite this Report

Poas

Costa Rica

10.2°N, 84.233°W; summit elev. 2708 m

All times are local (unless otherwise noted)


Continued fumarolic activity

Fumarolic activity continued within the small crater lake, concentrated at the three fumarole groups (to the SE, NE, and NW). Extensive sulfur exhalation and precipitation continued. The strongest activity was noted in the NW group of fumaroles, which formed an E-W-trending line. One of the fumaroles produced emissions of primarily SO2 gas, while others produced a jet aircraft sound, and two had orange flames. Temperatures of fumaroles on the top of the 1953-55 dome, S of the crater lake, were stable at <92.5°C.

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

Information Contacts: G. Soto, ICE.


Popocatepetl (Mexico) — August 1990 Citation iconCite this Report

Popocatepetl

Mexico

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

All times are local (unless otherwise noted)


Most nearby earthquakes tectonic, but a few small B-type events detected

Summit visits in March and April 1989 revealed large sulfur deposits in the main and inner craters, and more than 20 fumaroles on the upper S flank that had not been present 2 years earlier (14:04). The following is a report from Servando de la Cruz-Reyna.

"On 15 November 1989, the first telemetering seismic monitoring station at Popocatépetl began operation near Tlamacas, on the NW flank at 3,980 m above sea level. The station consists of a 3-component, 1-second seismometer, continuously transmitting analog signals to the Instituto de Geofísica, UNAM, in México City. The vertical component is registered on a drum analog recorder, and all three components are digitally recorded on a hard disc, then on an optical disc, when signal amplitudes exceed a preset level. The transducer and recording devices are property of the National Seismological Service, UNAM; the transmitter/receiver set was donated by the Japan International Cooperation Agency. A basic 6-point deformation network was also set up in November 1989 on the NW flank between 3,980 and 4,525 m altitude.

"So far, the 9-month seismic record indicates that background seismicity is dominated by small regional earthquakes occurring within a radius of 40 km, mainly W and SW of the volcano. However, a number of very small local B-type earthquakes have been persistently recorded. The activity has not shown any significant changes. Though minor, the B-type activity and the persistent condensation of sulfur in the inner parts of the crater call for more intensive monitoring."

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

Information Contacts: S. de la Cruz-Reyna, UNAM, México D.F.


Purace (Colombia) — August 1990 Citation iconCite this Report

Purace

Colombia

2.32°N, 76.4°W; summit elev. 4650 m

All times are local (unless otherwise noted)


Sulfur-rich summit fumaroles and flank hot springs

"The summit crater and hydrothermal sites were visited on 6 and 7 August, with María Luisa Monsalve (INGEOMINAS, Popayán). The Coconucos-Aguas Herviendo hot springs, 5.5 km WNW of the crater at ~2,900 m elev, in the Río Grande valley, are a very popular developed site, with concrete pools and restaurant. Maximum water temperatures were measured in the small central bubbling spring and were 74°C (unchanged since December 1989). pH was not measured on this trip but was 6.2 in December. Coconucos-Aguas Tibias, ~ 2 km S of Aguas Herviendo (6 km WSW of the crater), has one small concrete pool with a natural spring ~300 m to the S. Maximum temperatures were 61°C. Giggenbach-type gas samples were collected from the bubbles at both sites. A third hydrothermal site, Pilimbala, is at 3,350 m elev and 7.8 km from the crater. This site is maintained by the national park service (INDERENA) and has large tile-lined pools, filled with water from the single large spring. Maximum temperature was 31°C. No pH was measured and no bubbles were observed in the spring. Although there was abundant deposition of sulfur within the hot spring, there was little odor of H2S.

"At the nearby mine site (3,550 m elev), the swimming pool spring was sampled again. The temperature was 47°C, unchanged since December 1989, when the pH was 4.3. The odor of H2S was very strong and abundant sulfur deposition was evident in the spring and swimming pool.

"The crater was visited on a day with almost no visibility and during a freezing rain. A fumarole field is located on a circumferential crack, ~ 100 m outside of the crater, and on a line between the crater and the mine (340°). The summit crater is ~ 400 m in diameter and ~ 100 m deep. A central graben, oriented 100°, is located in the deepest part of the crater and all of the crater fumaroles are located within it. The maximum temperature in the westernmost fumarole field was 89°C (unchanged). The fumarole field covered an area of ~10 m diameter and had a typical low-temperature appearance, with abundant native sulfur and aluminum chloride deposition over a large area. Some collapse of the fumarole had apparently taken place since the December 1989 visit. During the first visit to the crater, in April 1988, the fumaroles looked as if they were hotter than in August 1990 but no temperatures were taken. The summit fumaroles were basically steam and the system appeared to be dominated by recirculation of groundwater, with little magmatic input at this time.

Geologic Background. One of the most active volcanoes of Colombia, Puracé consists of an andesitic stratovolcano with a 500-m-wide summit crater that was constructed over a dacitic shield volcano. It lies at the NW end of a volcanic massif opposite Pan de Azúcar stratovolcano, 6 km SE. A NW-SE-trending group of seven cones and craters, Los Coconucos, lies between the two larger edifices. Frequent explosive eruptions in the 19th and 20th centuries have modified the morphology of the summit crater. The largest eruptions occurred in 1849, 1869, and 1885.

Information Contacts: S. Williams, Louisiana State Univ; J. Stix and E. Fontaine, Univ de Montréal.


Rabaul (Papua New Guinea) — August 1990 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 at background

"Seismic activity remained at background level in August. A total of 113 caldera earthquakes was recorded (compared to 213 in July and an average of 215/month since mid-1986). The located events originated from the NW part of the annular caldera seismic zone. All events were of small magnitude (ML <=1.5). No significant changes were observed in levelling, tilt, EDM, and gravity measurements."

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: I. Itikarai and C. McKee, RVO.


Ruapehu (New Zealand) — August 1990 Citation iconCite this Report

Ruapehu

New Zealand

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

All times are local (unless otherwise noted)


Crater Lake temperature increases; tremor resumes; inflation

Crater Lake temperatures had risen to 25°C (at the Outlet) and 27° (at the logger site) on 22 August, compared to 20 and 21°C respectively during 20 July fieldwork. Convection above the lake's center was indicated by dark slicks, while yellow slicks were present over the N vents; the rest of the lake was battleship gray. Clearer visibility on 29 August confirmed central vent convection that produced dark yellow-green slicks. Steam rising from the lake formed an impressive column by 1330, when it was reported to the Dept of Conservation as a possible eruption by the crew of a commercial airliner. Lake water collected 22 August showed declines in Mg and Cl contents of 1.4% and 7.2% respectively since 20 July. The Mg/Cl ratio continued to drop (to 0.051) indicating continued steam discharge into the lake with little or no liquid phase input from the vent.

After a month with little or no tremor, amplitude rose to low-moderate levels for ~2 weeks beginning 1 August; after the 15th, only low-amplitude tremor has been recorded. A series of small to moderate volcanic earthquakes (maximum ML 2.1) was recorded, mainly between 2 and 5 August, and a short episode of low-frequency tremor occurred 10 August. Deformation measurements showed extensions of as much as 21 mm across Crater Lake between 20 July and 29 August.

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: B. Scott, NZGS Rotorua; P. Otway, DSIR Wairakei.


Nevado del Ruiz (Colombia) — August 1990 Citation iconCite this Report

Nevado del Ruiz

Colombia

4.892°N, 75.324°W; summit elev. 5279 m

All times are local (unless otherwise noted)


Frequent ash emission with associated tremor; ashfall to 30 km; hot springs described

Ash emissions were reported during May, July, and August, frequently with associated tremor. Tremor intensity and the number of high- and low-frequency earthquakes fluctuated, roughly corresponding with increased explosive activity. SO2 flux was moderate with the exception of high fluxes recorded during June, and the geochemistry of the hydrothermal system remained unchanged from December 1988.

Ash emissions. Ash was emitted on seven days during May (5, 6, 8, 12, 14, 17, and 24), deposited primarily to the N, NW, and W. On 14 May, ash was reported falling in Manizales (25 km W of the volcano) from 1120 to 1530 with an average cumulative thickness of 0.43 g/m2. No ash was reported during June, but five small ash emissions were reported during July, with a total accumulation of 500 g/m2 at Refugio (2.0 km NW of the crater). The largest emission, on 25 July, deposited ash 30 km from the volcano. The deposits, 2 mm thick at Refugio, were composed exclusively of lithic material. Several small ash emissions were also reported during August.

Volcanic tremor. Tremor was frequently associated with the ash emissions (and with long-period events in August), and its frequency of occurrence and intensity roughly corresponded with the frequency and intensity of ash emissions. During May and July, tremor was more frequent and more intense; the reduced displacement was 3.2 cm2 on 12 May, 2.85 cm2 on 14 May, 3.05 cm2 on 22 May, and reached 3.5 cm2 in July (these were considered moderate to below moderate levels for Ruiz). During June and August when there was little or no ash emission activity, reduced displacements were 0.32 cm2 on 9 June, 0.88 cm2 on 26 June, and <1.0 cm2 in August. During May-August, tremor episodes had periods of 0.1-0.5 seconds (0.15-0.4 seconds during August) and originated at <1 km depth. These episodes usually occurred in pulses with durations of 5-15 minutes, but occasionally were continuous (13-15 May and the end of August).

A second type of tremor, characterized as low-intensity and short-duration, has been noted at Ruiz. It is considered to be from a deeper source and is not associated with ash emissions. During July it originated W of the crater at >=1 km depth.

Other seismicity. Seismic activity increased during May with 1,326 high-frequency and 1,982 low-frequency recorded earthquakes (up from 579 and 1,580 respectively in April). Of these, 247 high- and 156 low-frequency earthquakes, occurred during a swarm on 31 May. The earthquakes were centered in three clusters; NE of, SW of, and under the crater, aligned with the Palestina fault, and at depths from 0.5 to 4.5 km. During June, 1,664 high- and 1,422 low-frequency earthquakes of M <= 2.8 were recorded, at depths of 0.5-12 km. Epicenters were aligned with and transverse to the Palestina Fault. Seismicity increased during July, with mainly long-period earthquakes and bursts of seismicity consisting of many high- and low-frequency earthquakes occurring in trains. The earthquakes were located around the crater at depths of 0.5-5.0 km. A swarm of 400 earthquakes (M <=2.6), with three felt shocks at the onset, were recorded over a 6-hour period on 28 August (figure 37). The swarm was located NE of the crater with focal depths < 1.5 km (figure 38).

Figure (see Caption) Figure 37. Seismicity at Ruiz, August 1990. Solid line, high-frequency events; dashed line, low-frequency events. Courtesy of INGEOMINAS.
Figure (see Caption) Figure 38. Epicenters of high-frequency earthquakes at Ruiz, August 1990. Courtesy of INGEOMINAS.

Deformation. Deformation continued to be monitored at Ruiz using a network of dry-tilt and EDM stations; one new EDM station was added to the network in June near the Bis seismic station (at 5,030 m, almost 6 km NW of the crater). A few short-term episodes of moderate deformation were noted during May, but no significant deformation was detected during June-mid-August. On 13 August, the Refugio EDM station showed a rapid 100-µrad displacement (figure 39), but this did not correspond with any other recognized changes in activity (seismic, geochemical, or deformational) at the volcano.

Figure (see Caption) Figure 39. Deformation at Refugio EDM station, Ruiz, August 1990. Courtesy of INGEOMINAS.

Measurement of topographic controls on the summit glaciers indicated a decrease in ablation in June with respect to April and May.

Plume geochemistry. COSPEC monitoring indicated a decrease in SO2 flux following high levels in June. The monthly average SO2 flux was 1,519 t/d in May (11 measurements with a range of 367-3,869 t/d), 5,985 t/d in June (three measurements, 5,208-7,498 t/d), 1,097 t/d in July (six measurements, 406-2,672 t/d), and 2,437 t/d in August (figure 40).

Figure (see Caption) Figure 40. Monthly average SO2 flux from Ruiz, 1988-90. Upper line is calculated with measured wind data; lower line without wind data. Courtesy of INGEOMINAS.

Geochemistry of the hydrothermal system. The following is by S. Williams, S. Schaefer, and José Vasquez.

"The large white gas column continues to boil continuously from Ruiz. We visited and sampled hydrothermal springs between 11 and 16 August. The geochemistry of all of the sites has been studied and is reported in Sturchio and others (1988) and Williams and others (1990). His isotopic data are reported in Sano and others, 1990. The Azufrera Nereidas gas vent, located in the Nereidas valley at 3,575 m elevation, had maximum temperatures of 86°C. Gas release appeared to be unchanged from the previous visit in December 1988. The hot spring, located in the river canyon below the gas vent, was found to have temperatures of 51°C and pH of 6.1. The flow rate was estimated to be between 1 and 5 liters/minute. Abundant sulfur deposition is evident at the spring. In Botero Londoño hotspring, at 15 km distance and 2,450 m elevation, spouting hot water had a maximum temperature of 95°C and pH of 7.6. The springs closest to the crater, Río Gualí (at 3 km and 4,670 m) had a maximum temperature of 57°C and pH of ~3.8. These are located within ~50 m of the tongue of the glacier in the Gualí valley. Aguas Calientes, at 7 km and 3,780 m elevation, was found to be unchanged from the previous visit (December 1989) with a maximum temperature of 61°C and pH of 1.6. Other hot springs sampled in July included El Recodo and the Hotel Termales del Ruiz. El Recodo, a bicarbonate spring, had a temperature of 60°C and pH of 7.8, unchanged from measurements made in December 1986. The Hotel is a strong acid-sulfate-chloride spring with a temperature of 64°C and pH of 1.1."

References. Sano, Y., Wakita, H., and Williams, S.N., 1990, Helium isotope anomaly in Nevado del Ruiz volcano, Colombia: implications for volcanic hydrothermal system: JVGR, v. 42, p. 41-52.

Sturchio, N.C., Williams, S.N., García P., N., and Londoño C., A., 1988, The hydrothermal system of Nevado del Ruiz Volcano, Colombia: BV, v. 50, p. 399-412.

Williams, S.N., Sturchio, N.C., Calvache, M.L., Mendez, R., Londoño C., A., and García P., N., 1990, Sulfur dioxide flux from Nevado del Ruiz volcano, Colombia: total flux and isotopic constraints on its origin: JVGR, v. 42, 53-68.

Geologic Background. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers more than 200 km2. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.

Information Contacts: C. Carvajal and F. Cruz, INGEOMINAS, Manizales; S. Williams and S. Schaefer, Louisiana State Univ; J. Vasquez, Beloit College.


Stromboli (Italy) — August 1990 Citation iconCite this Report

Stromboli

Italy

38.789°N, 15.213°E; summit elev. 924 m

All times are local (unless otherwise noted)


Strong explosions; one crater filled by tephra

An automatic telemetering short-period seismic station was installed near the active craters in October 1989 to monitor explosive activity and volcanic tremor. During that month, "normal Strombolian" activity from Craters 1 and 3 produced ~160 explosive events/day (figure 5). During the second half of November, several events with peculiar waveforms were recorded over a 4-day period. Volcano guides (who cooperate with volcanologists by noting visible activity, as reported below) observed a new cone inside Crater 1 in December 1989, and another cone that showed explosive activity between craters 1 and 2 in February 1990. In March, small cones produced bluish vapor inside Crater 3; emissions were accompanied by dull rumbling.

Figure (see Caption) Figure 5. Average number of seismic events/hour recorded at Stromboli, October-November 1989 and April-July 1990. Arrow marks 18 June explosions. Courtesy of M. Riuscetti.

During the end of May and the first half of June (28 and 30 May, and 3, 4, 11, 13, and 15 June) "normal" activity was observed at craters 1 and 3 with continuous explosions and ejection of incandescent material to 10-50 m height. Crater 2 was not active during this period. Morphologic changes to the new cones in Crater 1 were not evident.

At least four large explosions occurred on 18 June between 1700 and 1710. Ejecta fell onto the NW flank's Sciara del Fuoco and ash emission could be seen from S. Bartolo village on the NE side of the island. The wall between craters 2 and 3 collapsed. After this episode, explosive activity with ejection of small glowing blocks was observed at Crater 2 (on 19, 21, 24, 25, and 28 June, and 2 July) with almost continuous noisy gas emission (on 25 June, and 4, 7, and 9 July). Craters 1 and 3 were active, with ejection of glowing material to ~100-150 m height (on 24 and 26 June, and 1, 3, 4, 5, 7, and 9 July).

An increase in the number of low-energy explosion earthquakes occurred 9-16 July, while tremor amplitude decreased slightly. The number of events saturating the seismometer then increased sharply, while low-energy shocks dropped to near the long-term mean (figure 6). Ash and lapilli emissions were continuous from the three craters, with increases in ejecta height and emission frequency after 19 July. The strong eruptive activity declined after 26 July. Crater 2 had been completely filled by tephra, but included two active vents characterized by synchronous noisy explosions. Activity at Crater 3 was dominated by prolonged silent ash emissions. Continuous strong explosions from Crater 1 have been observed since 1 August.

Figure (see Caption) Figure 6. Top: detail of figure 5, showing daily average number of seismic events/hour recorded at Stromboli, 21 June-31 July, 1990. Bottom: number of events with amplitude ³ full scale (solid line) and average relative tremor amplitude (dashed line), 9 July-4 August, 1990. Mean values for the period are shown. Courtesy of M. Riuscetti.

Geologic Background. Spectacular incandescent nighttime explosions at this volcano have long attracted visitors to the "Lighthouse of the Mediterranean." Stromboli, the NE-most of the Aeolian Islands, has lent its name to the frequent mild explosive activity that has characterized its eruptions throughout much of historical time. The small island is the emergent summit of a volcano that grew in two main eruptive cycles, the last of which formed the western portion of the island. The Neostromboli eruptive period took place between about 13,000 and 5,000 years ago. The active summit vents are located at the head of the Sciara del Fuoco, a prominent horseshoe-shaped scarp formed about 5,000 years ago due to a series of slope failures that extend to below sea level. The modern volcano has been constructed within this scarp, which funnels pyroclastic ejecta and lava flows to the NW. Essentially continuous mild Strombolian explosions, sometimes accompanied by lava flows, have been recorded for more than a millennium.

Information Contacts: M. Riuscetti, Univ di Udine; volcano guides:Prospero Cultrera, Nino Aquilone, and Antonio Zerilli, Stromboli, Italy.


Ulawun (Papua New Guinea) — August 1990 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)


Weak vapor emission and seismicity

"Activity remained at a very low level in August. Emissions from the summit crater consisted of white vapour in weak to moderate amounts. Seismicity was at a very low level during 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: I. Itikarai and C. McKee, RVO.


Unzendake (Japan) — August 1990 Citation iconCite this Report

Unzendake

Japan

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

All times are local (unless otherwise noted)


Seismicity declines slightly

Seismicity declined in August, but remained at high levels (345 earthquakes) . . . . Five earthquakes were felt [at UWS] and 56 tremor episodes were recorded (an increase from 11 in July). Tremor amplitude ranged from 0.2 to 0.9 [µm] (figure 4).

Figure (see Caption) Figure 4. Amplitude of volcanic tremor at Unzen, July-August 1990. Courtesy of JMA.

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: JMA.


Vulcano (Italy) — August 1990 Citation iconCite this Report

Vulcano

Italy

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

All times are local (unless otherwise noted)


High fumarole temperatures and geochemical changes; seismicity suggests complex fumarolic system

"OV geologists visited Vulcano island in recent months. Temperatures of the sampled crater fumaroles F5, F5AT, and FA (figure 9) were 300°, 420°, and 537°C respectively on 18 August. During two night inspections inside the crater, bright glow was discovered at all fumaroles up to 530°C and blue flames were discovered at some points in the fumarolic field, probably revealing burning of molten sulfur.

Figure (see Caption) Figure 9. Map of Vulcano showing the locations of fumaroles (F5, F5AT, and FA), and the seismic stations (CNW and CNE) used during the May 1990 microseismicity study. Courtesy of the Osservatorio Vesuviano.

Geochemistry. "Several chemical variations have been observed since April 1990 in fluids sampled at F5 fumaroles. A sharp decrease in H2O content similar to that recorded in 1988 (see figure 7) has occurred. Consequently, CO2, SO2, N2, HCl, and HF increased in content. At the same time, the S/C ratio significantly decreased. Chemical variations seemed to follow the trend recorded in 1988. These data agree with an unpublished model by Tedesco et al. of possible mixing between shallow and deep fluids, continuously occurring in different proportions before gas escapes from fumarolic vents.

Geophysics. "A microseismicity study of Vulcano crater by the OV in the summer of 1988 revealed the presence of Rayleigh and Rayleigh-like waves with a prograde rotation (15:03). The analyzed earthquakes were low-frequency events, with energy up to 1012 ergs, showing phases not clearly identifiable on seismograms. Most scientists believe them to be related to gas flow in fumarolic conduits (Blot, 1971; Latter, 1971). Particle motion analysis revealed retrograde and prograde elliptical orbit phases that followed one another during such earthquakes (figures 10 and 11). This physical phenomenology was interpreted as due to propagation and reflection of tube waves in a fluid-filled conduit (White, 1983; Toksoz and Stewart, 1984; Hardage, 1985). According to such a model, the successive rotation inversions of particle motion would be generated from alternating downgoing and upgoing tube waves. The non-correlativity of phase arrivals among the seismic network stations suggested complex circulations discriminated by tube heights, because of the presence of several reflecting points (in fact seismographs operated at different altitudes on Vulcano island).

Figure (see Caption) Figure 10. Particle motion on the vertical-radial plane (with respect to crater axes) derived from Vulcano seismogram in figure 11. Numbered frames correspond to seismogram segments and represent several seconds; arrows mark rotation inversions relating to phase arrivals. Courtesy of the OV.
Figure (see Caption) Figure 11. Filtered three-component signal of the Vulcano microearthquake analyzed in figure 10. Dotted lines discriminate temporal intervals (numbered frames in figure 10) for particle motion, and arrows mark arriving of retrograde and prograde phases. Courtesy of OV.

"In May 1990, a survey was carried out to verify the possible presence of correlativity and synchrony of phase arrivals at two seismic stations placed at the same altitude on the top of the crater. Stations were installed at ~90° from each other with respect to the crater axes (figure 9). Notwithstanding the low activity level during the 2-week recording period, the few events analyzed show the same phenomenology observed on 1988 records. Unfortunately, the expected correlativity was absent. The negative result, not invalidating the proposed model, suggested a complex geometry of the tube-like source structure, such as non-vertical orientation."

References. Blot, C., 1971, Etude sismologique de Vulcano: Cahiers ORSTOM serie Géophysique, no. 11.

Hardage, B.A., 1985, Vertical seismic profiling, Part A: Principles, in Helbig, K., and Treitel, S., eds., Handbook of Geophysical Exploration: Geophysical Press, p. 71-95.

Latter, J.K., 1971, Near Surface seismicity of Vulcano, Aeolian Islands, Sicily: BV, v. 35, p. 117-126.

Toksoz, M.N., and Stewart, R.R., eds., 1984, Vertical seismic profiling, Part B: Advanced Concepts, in Helbig, K., and Treitel S., eds., Handbook of Geophysical Exploration: Geophysical Press, p. 256-313.

White, J.E., 1983, Underground sound: application of seismic waves: Elsevier, New York, p. 139-191.

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

Information Contacts: D. Tedesco, S. Vulcano, and G. Luongo, OV.


Whakaari/White Island (New Zealand) — August 1990 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)


Block eruption; significant morphologic changes in 1978 Crater

Late-August fieldwork revealed significant morphologic changes to 1978 Crater, which had deepened and extended 30-50 m E since May. A narrow zone of newly erupted lithic blocks extended several hundred meters from a vent E of the 1978 Crater complex.

During a 29 May visit, Ashley Cody found no significant changes since 17 May fieldwork (BGVN 15:05). Fresh impact craters had apparently been formed by small blocks erupted from the new pit vent observed 17 May on the E side of R.F. Crater. Ash and "gravel" was reported falling on fishing boats anchored on the N side of White Island 29-30 June.

When geologists returned on 30 August, blocks had fallen in a zone ~100 m wide extending several hundred meters SE from Donald Duck vent (E of 1978 Crater). In the tephra-fall zone within 150 m of the vent, the ground was almost completely covered by blocks up to 1 m across. Farther from the vent, blocks to 0.3 m occupied scattered impact craters with the most distant blocks ~450 m away. A gray ash deposit thickened toward Donald Duck, from 20 mm roughly 100 m SW of the vent, to 330 mm at a site 5 m from the rim. No fresh magma was noted in any of the ejecta. Donald Duck vent had deepened and enlarged to a pipe 2-3 m in diameter extending down to the NW at a shallow angle to the horizontal. Moderate amounts of non-incandescent gas were being emitted from the vent. To the N, gas emission from Noisy Nellie was the strongest it had been in several years, causing ground vibration nearby. The vent had slightly enlarged and deepened, and had deposited a continuous coarse tephra cover that extended 30 m S. A minimum temperature of 370°C was measured (by Minolta-Land infrared sensor) during a 1 September visit, compared to 459° on 17 May. Activity at other fumaroles was at low intensity.

The 1978 Crater complex had deepened and enlarged considerably since May. No eruptive activity appeared to have accompanied the collapse episode and it was not associated with any unusual seismicity, suggesting that it was triggered by recent heavy rainfall. On 30 August, the crater's E wall was 30-50 m E of its 17 May position, and ground cracking extended ~10 m farther E from the nearly vertical crater wall, suggesting that further collapse was likely. Within the crater, the dividing wall between R.F. and Congress Craters had been removed. R.F. Crater was the deepest part of the complex, and was occupied by a green lake with a few small steaming areas around its edges. Material that had collapsed from 1978 Crater's E wall formed a landslide deposit across its E floor. A deformation survey revealed subsidence centered on Donald Mound (S of Donald Duck vent) exceeding 20 mm since 17 May, reversing two months of inflation. However, one site just S of Donald Duck vent showed a 289 mm decrease, suggesting incipient ground failure.

Seismic instruments resumed operation 20 May, recording 5-13 A-type (high-frequency) events daily until the onset of a swarm on 14 June. During the next two days, >120 A-type shocks were detected, reaching about ML 2.7. The swarm ended with an E-type eruption earthquake that had an unusually low dominant frequency and lasted ~45 minutes. Additional E-type episodes with durations of 28-35 minutes followed, again with lower-than-usual dominant frequencies. A-type events declined until 25 July, then increased again to ~10/day. Another swarm of >80 shocks (maximum ML 2.1) occurred 28 July, then A-type events declined to ~5/day. B-type (low-frequency) volcanic earthquakes were recorded on most days after 20 May, initially exceeding 20/day but soon declining to < 5/day. After the 14-16 June swarm, the number of B-type events increased sharply for two days, then dropped to 5-10/day, remaining at that level through August. Other E-type (eruption) earthquake sequences occurred at the end of May, with four of similar size, 6-15-minute durations, and lower-than-usual dominant frequencies shortly after seismic recording resumed. An isolated 7-minute E-type event on 13 July was of distinctly higher dominant frequency. Five E-type episodes have occurred since 13 August, most recently on the 24th, all with high-frequency codas but short (2-14-minute) durations. No tremor has been recorded.

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: I. Nairn and B. Scott, NZGS Rotorua; P. Otway, DSIR, Wairakei.

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