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Smithsonian/USGS Weekly Volcanic Activity Report 8-14 June 2011
From: "Kuhn, Sally" <KUHNS@xxxxxx>
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Smithsonian/USGS Weekly Volcanic Activity Report
8-14 June 2011
Sally Kuhn Sennert - Weekly Report Editor
kuhns@xxxxxx
URL: http://www.volcano.si.edu/reports/usgs/
New Activity/Unrest: | Aso, Kyushu | Dieng Volcanic Complex, Central Java (Indonesia) | Kizimen, Eastern Kamchatka (Russia) | Nabro, Eritrea | Puyehue-Cordón Caulle, Central Chile | Yasur, Vanuatu (SW Pacific)
Ongoing Activity: | Batu Tara, Komba Island (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaii (USA) | Mayon, Luzon | Sakura-jima, Kyushu | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Tengger Caldera, Eastern Java (Indonesia)
The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network.
Note: Many news agencies do not archive the articles they post on the Internet, and therefore the links to some sources may not be active. To obtain information about the cited articles that are no longer available on the Internet contact the source.
New Activity/Unrest
ASO Kyushu 32.881°N, 131.106°E; summit elev. 1592 m
Based on notices from JMA, the Tokyo VAAC reported that during 7-9 June plumes from Aso rose to altitudes of 1.5-1.8 km (5,000-6,000 ft) a.s.l. and drifted NW, N, NE, and E.
Geologic Summary. The 24-km-wide Aso caldera was formed during four major explosive eruptions from 300,000 to 80,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. A group of 17 central cones was constructed in the middle of the caldera, one of which, Naka-dake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 AD. The Naka-dake 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 AD. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic Strombolian and phreatomagmatic activity. The summit crater of Naka-dake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.
Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
DIENG VOLCANIC COMPLEX Central Java (Indonesia) 7.20°S, 109.92°E; summit elev. 2565 m
CVGHM reported that during 31 May-10 June carbon dioxide gas emissions declined from Timbang, a cone that is part of the Dieng Volcanic Complex. Seismicity decreased during 5-7 June and was not detected during 8-10 June. White plumes were not observed. On 10 June the Alert Level was lowered to 2 (on a scale of 1-4).
Geologic Summary. The Dieng plateau in the highlands of central Java is renowned both for the variety of its volcanic scenery and as a sacred area housing Java's oldest Hindu temples, dating back to the 9th century AD. The Dieng volcanic complex consists of two or more stratovolcanoes and more than 20 small craters and cones of Pleistocene-to-Holocene age over a 6 x 14 km area. Prahu stratovolcano was truncated by a large Pleistocene caldera, which was subsequently filled by a series of dissected to youthful cones, lava domes, and craters, many containing lakes. Lava flows cover much of the plateau, but have not occurred in historical time, when activity has been restricted to minor phreatic eruptions. Toxic volcanic gas emission has caused fatalities and is a hazard at several craters. The abundant thermal features that dot the plateau and high heat flow make Dieng a major geothermal prospect.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://www.vsi.esdm.go.id/
KIZIMEN Eastern Kamchatka (Russia) 55.130°N, 160.32°E; summit elev. 2376 m
KVERT reported that during 3-10 June seismicity from Kizimen was above background levels and strong tremor continued to be detected. Seismic data indicated that possible ash plumes rose to an altitude of 6.6 km (21,700 ft) a.s.l. during 5-8 June. Satellite images showed a large bright thermal anomaly on the volcano during 3-5, 7, and 9 June, and an ash plume that rose to an altitude of 5 km (16,400 ft) a.s.l. on 9 June.
During 11-12 June seismicity significantly increased. Seismic data indicated 10 strong explosions and ash plumes that rose to altitudes of 4-5.9 km (13,120-19,350 ft) a.s.l. Satellite imagery showed a wide ash plume that drifted 135 km SE and a large bright thermal anomaly. The Aviation Color Code was raised to Red. On 12 June volcanic tremor magnitude decreased, then sharply decreased about 4 hours later. The next day ash plumes observed in satellite imagery drifted 760 km E at altitudes that did not exceed 5.9 km (19,350) a.s.l. A large bright thermal anomaly continued to be detected. Volcanic-tremor magnitude again increased for about a three-hour period, then decreased and remained low on 14 June. Satellite imagery from that day showed a large pyroclastic flow deposit on the NE flank from 11-13 June activity. An ash plume drifted 26 km S on 15 June.
Geologic Summary. Kizimen is an isolated, conical stratovolcano that is morphologically similar to Mount St. Helens prior to its 1980 eruption. The summit of Kizimen consists of overlapping lava domes, and blocky lava flows descend the flanks of the volcano, which is the westernmost of a volcanic chain north of Kronotsky volcano. The 2,376-m-high Kizimen was formed during four eruptive cycles beginning about 12,000 years ago and lasting 2,000-3,500 years. The largest eruptions took place about 10,000 and 8300-8400 years ago, and three periods of longterm lava-dome growth have occurred. The latest eruptive cycle began about 3,000 years ago with a large explosion and was followed by lava-dome growth lasting intermittently about 1,000 years. An explosive eruption about 1,100 years ago produced a lateral blast and created a 1.0 x 0.7 km wide crater breached to the NE, inside which a small lava dome (the fourth at Kizimen) has grown. A single explosive eruption, during 1927-28, has been recorded in historical time.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
NABRO Eritrea 13.37°N, 41.70°E; summit elev. 2218 m
According to the USGS Earthquake Hazards Program, an earthquake swarm was detected during the evening of 12 June on the border of Ethiopia and Eritrea, in the vicinity of Nabro, the most prominent of three volcanoes with large summit calderas aligned in a NE-SW direction SW of Dubbi volcano. The swarm began at 1837 with an M 5.1 earthquake. Several more were detected between M 4.3 and 5.1 over the next few hours. Two M 5.7 earthquakes at depths of 10.1 km and 9.9 km were detected at 2332 on 12 June and 0003 on 13 June, respectively.
The Toulouse VAAC reported that an eruption from Nabro (originally attributed to Dubbi) started between 0000 and 0200 on 13 June. An eruption plume initially rose to altitudes of 9.1-13.7 km (30,000-45,000 ft) a.s.l. then was later detected at altitudes of 6.1-10.7 km (20,000-35,000 ft) a.s.l. during 13-14 June. According to the Eritrean Ministry of Information, ashfall covered hundreds of kilometers and the government evacuated area residents. Witnesses noted that the eruption had started at about 2100 on 13 June. Satellite images that same day showed the plume drifting more than 1,000 km NW, over parts of Sudan. On 14 June a detached ash cloud was detected over southern Israel according to news articles. A plume from Nabro was not obvious on satellite imagery.
Geologic Summary. The 2218-m-high Nabro stratovolcano is the highest volcano in the Danakil depression of northern Ethiopia and Eritrea. Located at the SE end of the Danakil Alps, Nabro lies in the Danakil horst. Nabro is the most prominent and NE-most of three volcanoes with large summit calderas aligned in a NE-SW direction SW of Dubbi volcano. These three volcanoes, along with Sork Ale volcano, collectively comprise the Bidu volcanic complex. The complex Nabro stratovolcano is truncated by nested calderas, 8 and 5 km in diameter. The larger caldera is widely breached to the SW. Nabro was constructed primarily of trachytic lava flows and pyroclastics. Post-caldera rhyolitic obsidian domes and basaltic lava flows were erupted inside the caldera and on its flanks. Some very recent lava flows were erupted from NNW-trending fissures transverse to the trend of the Nabro volcanic range.
Sources: USGS Earthquake Hazards Program http://earthquake.usgs.gov/,
Toulouse Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/FR/messages.html,
MODIS Rapid Response System http://rapidfire.sci.gsfc.nasa.gov/,
Eritrean Ministry of Information http://www.shabait.com/news/local-news/5977-volcanic-eruption-witnessed-in-the-tip-of-southern-red-sea-region,
The Jerusalem Post http://www.jpost.com/Headlines/Article.aspx?id=224929
PUYEHUE-CORDON CAULLE Central Chile 40.590°S, 72.117°W; summit elev. 2236 m
OVDAS-SERNAGEOMIN reported that the eruption from the Cordón Caulle rift zone, part of the Puyehue-Cordón Caulle volcanic complex, that began on 4 June continued on 5 June. At least five pyroclastic flows were generated from partial collapses of the eruptive column and traveled N in the Nilahue River drainage. The pyroclastic flows were possibly 10 km long. On 6 June the continuous ash plume changed direction and was blown ENE as far as 178 km while the previous portion of the plume continued to drift ESE over the ocean. On 7 June the Buenos Aires VAAC reported that ash plumes rose to altitudes of 5.5-9.8 km (18,000-32,000 ft) a.s.l. and were 65-95 km wide.
OVDAS-SERNAGEOMIN reported that on 8 June satellite imagery showed a 1,200-km-long eruption plume drifting NE, then SE over the Atlantic Ocean. Personnel working in the area reported that the ash plume rose 7.5 km above the crater. On 9 June climatologic conditions prevented ground-based observations of the plume, however satellite imagery showed a 200-km-long plume drifting NE. Pumice and vitreous tephra had accumulated in many area lakes and rivers, and ash had turned many rivers darker. Despite poor visibility due to meteorological conditions on 10 June, the plume was observed to have risen 3.7 km above the crater and drifted SE. News articles stated that flight disruptions continued in Argentina and Uruguay, and flights from airports in Brazil had been cancelled. On 11 June the plume was whiter than previous days and rose to heights 4-4.5 km above the crater and drifted 350 km E. A dispersed plume was detected as far as 600 km ENE. Some flights resumed in affected parts of Chile, Argentina, and Uruguay.
An overflight on 11 June revealed that the vent was located at the head of the Nilahue River's basin, immediately to the N of the 1960 eruption fissure location. Abundant amounts of ash had accumulated around the vent as well as to the E and SW. Ash plumes rose 4-4.5 km above the crater; an explosion that day caused an ash plume to rise 8 km above the crater. On 12 June seismicity was relatively stable except for four hybrid earthquakes and a pulse of tremor that lasted about 2 hours and 40 minutes. A series of explosions (up to 8 events per minute) were also registered. Very dense, dark gray ash plumes rose 8 km above the crater. Satellite imagery showed a distinct eruption plume drifting 300 km E, with a diffuse plume reaching 1,000 km ENE. According to news articles, the ash plume that had been drifting mostly E since the beginning of the eruption had reached Australia and beyond, causing flight cancellations in southern Australia and New Zealand.
Scientists aboard an overflight on 13 June observed the plume height oscillating and noted that the eruptive vent diameter was 300-400 m. Gas-and-steam plumes rose from two or three locations along the same fissure as the eruptive vent. Pulses of tremor were associated with dark gray ash plumes that rose 9 km above the crater. Ashfall and column collapses were noted. At night incandescence from the base of the plume reached 1.5-2 km high. Satellite imagery showed the plume drifting 250 km SE. On 14 June explosions generated pyroclastic flows (that traveled N), with associated ash-and-gas plumes. Based on analysis of satellite imagery, the VAAC stated that ash plumes rose to altitudes of 5.5-7.6 km (18,000-25,000 ft) a.s.l. while previously emitted ash plumes drifted NE, E, and SE at altitudes of 0.9-3 km (3,000-10,000 ft) a.s.l. SERNAGEOMIN reiterated that the Alert Level remained at 6, Red.
Geologic Summary. The Puyehue-Cordón Caulle volcanic complex (PCCVC) is a large NW-SE-trending late-Pleistocene to Holocene basaltic-to-rhyolitic transverse volcanic chain SE of Lago Ranco. The 1799-m-high Pleistocene Cordillera Nevada caldera lies at the NW end, separated from Puyehue stratovolcano at the SE end by the Cordón Caulle fissure complex. The Pleistocene Mencheca volcano with Holocene flank cones lies NE of Puyehue. The basaltic-to-rhyolitic Puyehue volcano is the most geochemically diverse of the PCCVC. The flat-topped, 2236-m-high Puyehue volcano was constructed above a 5-km-wide caldera and is capped by a 2.4-km-wide summit caldera of Holocene age. Lava flows and domes of mostly rhyolitic composition are found on the eastern flank of Puyehue. Historical eruptions originally attributed to Puyehue, including major eruptions in 1921-22 and 1960, are now known to be from the Cordón Caulle rift zone. The Cordón Caulle geothermal area, occupying a 6 x 13 km wide volcano-tectonic depression, is the largest active geothermal area of the southern Andes volcanic zone.
Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/,
Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html,
BBC http://www.bbc.co.uk/news/world-latin-america-13735661,
AAP http://news.smh.com.au/breaking-news-national/volcanic-ash-causes-air-traffic-turmoil-20110612-1fyql.html,
Associated Press http://www.msnbc.msn.com/id/43365884/ns/travel-news/
YASUR Vanuatu (SW Pacific) 19.53°S, 169.442°E; summit elev. 361 m
On 13 June, the Vanuatu Geohazards Observatory reported that activity from Yasur decreased during the previous week after a brief period of high activity with significant explosions and ashfall. Even though Strombolian activity occasionally ejected bombs that fell around the crater, explosions had become slightly weaker and less frequent. The Alert Level was lowered to 2 (on a scale of 0-4).
Geologic Summary. Yasur, the best-known and most frequently visited of the Vanuatu volcanoes, has been in more-or-less continuous Strombolian and vulcanian activity since Captain Cook observed ash eruptions in 1774. This style of activity may have continued for the past 800 years. Yasur is a mostly unvegetated pyroclastic cone with a nearly circular, 400-m-wide summit crater. Yasur is largely contained within the small Yenkahe caldera in SE Tanna Island. It is the youngest of a group of Holocene volcanic centers constructed over the down-dropped NE flank of the Pleistocene Tukosmeru volcano. Active tectonism along the Yenkahe horst accompanying eruptions of Yasur has raised Port Resolution harbor more than 20 m during the past century.
Source: Vanuatu Geohazards Observatory http://www.geohazards.gov.vu/
Ongoing Activity
BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m
Based on analyses of satellite imagery, the Darwin VAAC reported that during 8-13 June ash plumes from Batu Tara rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 55-75 km NW, N, and E.
Geologic Summary. The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
KARYMSKY Eastern Kamchatka (Russia) 54.05°N, 159.45°E; summit elev. 1536 m
KVERT reported moderate seismic activity at Karymsky during 3-10 June and that possible ash plumes rose to an altitude of 6 km (15,100 ft) a.s.l. Satellite imagery showed a thermal anomaly during 3-4 June and an ash plume that drifted 254 km SE on 4 June. The Aviation Color Code remained at Orange.
Geologic Summary. Karymsky, the most active volcano of Kamchatka's eastern volcanic zone, is a symmetrical stratovolcano constructed within a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago. Construction of the Karymsky stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been Vulcanian or Vulcanian-Strombolian with moderate explosive activity and occasional lava flows from the summit crater. Most seismicity preceding Karymsky eruptions has originated beneath Akademia Nauk caldera, which is located immediately S of Karymsky volcano and erupted simultaneously with Karymsky in 1996.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m
HVO reported that two lava lakes at Kilauea were active during 8-14 June. The level of the summit lava lake remained mostly stable deep in the vent inset within the E wall of Halema'uma'u Crater. Occasional increases in the lake level covered a vent on the south side wall; on other days lava from the vent cascaded down into the lake. A gas plume from the vent drifted SW. At Pu'u 'O'o, lava from vents near the W and NE edges of the perched lava lake in the center of the crater floor continued to fill the lake. The lake level fluctuated and infrequently overflowed the edges or flowed through a rim breach, sending lava onto the Pu'u 'O'o crater floor. There was also minor lava activity from at least one source at the base of the SW crater wall.
Geologic Summary. Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world's most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed of lava flows less than about 1,100 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 sq km, destroying nearly 200 houses and adding new coastline to the island.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO) http://hvo.wr.usgs.gov/
MAYON Luzon 13.257°N, 123.685°E; summit elev. 2462 m
PHIVOLCS reported that a deformation survey of Mayon conducted during 31 May-4 June showed slight inflation since a 6-10 March survey. White steam emitted from the summit crater during 8-13 June crept down the NW and WNW flanks. Incandescence from the crater was also observed. The Alert Level remained at 1 and the public was reminded not to enter the 6-km-radius Permanent Danger Zone (PDZ).
Geologic Summary. Beautifully symmetrical Mayon volcano, which rises to 2,462 m above the Albay Gulf, is the Philippines' most active volcano. The structurally simple volcano has steep upper slopes that average 35-40° and is capped by a small summit crater. The historical eruptions of this basaltic-andesitic volcano date back to 1616 and range from Strombolian to basaltic Plinian. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas. Mayon's most violent eruption, in 1814, killed more than 1,200 people and devastated several towns. Eruptions that began in February 2000 led PHIVOLCS to recommend on 23 February 2000 the evacuation of people within a radius of 7 km from the summit in the SE and within a 6 km radius for the rest of the volcano.
Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS) http://www.phivolcs.dost.gov.ph/index.php
SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m
Based on information from JMA, the Tokyo VAAC reported that during 8-9 and 14 June explosions from Sakura-jima produced plumes that rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted E and SE. During 8-9 and 13-14 June, pilots observed ash plumes that rose to altitudes of 2.4-3.7 km (8,000-12,000 ft) a.s.l.
Geologic Summary. Sakura-jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow was associated with the formation of the 17 x 23-km-wide Aira caldera about 22,000 years ago. The construction of Sakura-jima began about 13,000 years ago and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kita-dake summit cone ended about 4,850 years ago, after which eruptions took place at Minami-dake. 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.
Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m
KVERT reported that during 3-10 June seismic activity at Shiveluch indicated that possible ash plumes rose to an altitude of 9 km (29,500 ft) a.s.l. on 5 June and to altitudes of 5-7 km (16,400-22,960 ft) a.s.l. during 4-6 and 8 June. Satellite imagery showed a thermal anomaly on the lava dome during 3-4 June, and ash plumes that drifted 734 km SE on 4 June and 377 km NE during 5-6 June. Based on information from Yelizovo Airport (UHPP), the Tokyo VAAC reported that on 10 June an ash plume rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted W. The Aviation Color Code remained at Orange.
Geologic Summary. The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group and forms one of Kamchatka's largest and most active volcanoes. The currently active Molodoy Shiveluch lava-dome complex was constructed during the Holocene within a large breached caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. Intermittent explosive eruptions began in the 1990s from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964.
Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php,
Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m
MVO reported that during 3-10 June activity at the Soufrière Hills lava dome was at a low level. Unusual wind directions caused a sulfur odor in inhabited areas multiple times during the reporting period. On 9 June a pyroclastic flow traveled down the S flank, the first to go S in more than a year. The pyroclastic flow generated an ash cloud that drifted N and caused light ashfall in NW Montserrat. The Hazard Level remained at 3.
Geologic Summary. The complex dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. English's Crater, a 1-km-wide crater breached widely to the E, was formed during an eruption about 4,000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufrière Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.
Source: Montserrat Volcano Observatory (MVO) http://www.mvo.ms/
TENGGER CALDERA Eastern Java (Indonesia) 7.942°S, 112.95°E; summit elev. 2329 m
CVGHM reported that during 1-10 May white-to-gray ash plumes from Tengger Caldera's Bromo cone rose 400-600 m above the crater and drifted ENE, and incandescence emanated from the crater. During 11-20 May white-to-gray ash plumes rose 200-400 m above the crater and drifted E. Ash plumes continued to rise from the crater during 1-13 June to heights of 100-200 m above the crater and drifted E. Ash continued to fall in areas within 2 km E and NE during May and June. On 13 June the Alert Level was lowered to 2 (on a scale of 1-4).
Geologic Summary. The 16-km-wide Tengger caldera in eastern Java is located at the northern end of a volcanic massif extending from Semeru volcano. The massive Tengger volcanic complex consists of five overlapping stratovolcanoes, each truncated by a caldera. The most recent is the 9 x 10 km wide Sandsea caldera, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most frequently visited and most active volcanoes. More than 50 mild-to-moderate explosive eruptions have occurred since 1804.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://www.vsi.esdm.go.id/
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