VOLCANO: Smithsonian/USGS Weekly Volcanic Activity Report 11-17 May 2011

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Smithsonian/USGS Weekly Volcanic Activity Report 11-17 May 2011
From: Sally Kuhn Sennert <kuhns@xxxxxx>
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Smithsonian/USGS Weekly Volcanic Activity Report
11-17 May 2011

Sally Kuhn Sennert - Weekly Report Editor
kuhns@xxxxxx
URL: http://www.volcano.si.edu/reports/usgs/


New Activity/Unrest: | Aso, Kyushu | Bulusan, Luzon | Etna, Sicily (Italy) | Kizimen, Eastern Kamchatka (Russia) | Telica, Nicaragua | Tungurahua, Ecuador | Ulawun, New Britain | Yasur, Vanuatu (SW Pacific)

Ongoing Activity: | Bagana, Bougainville | Batu Tara, Komba Island (Indonesia) | Dukono, Halmahera | Karymsky, Eastern Kamchatka (Russia) | Katmai, Alaska Peninsula | Kilauea, Hawaii (USA) | Popocatépetl, México | Sakura-jima, Kyushu | Santa María, Guatemala | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat


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 pilot observations, the Tokyo VAAC reported that on 15 May an ash plume from Aso rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted NE. JMA reported that the next day plumes rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. A pilot noted that an ash plume rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted N that same day. During 17-18 May the JMA reported that ash plumes rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted E and SE.

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


BULUSAN Luzon 12.770°N, 124.05°E; summit elev. 1565 m

On 13 May, PHIVOLCS reported that an explosion from Bulusan's summit crater was accompanied by a rumbling sound audible up to 5 km away. The event was recorded by the seismic network as an explosion-type earthquake lasting for about 10 minutes. Cloud cover prevented observations of the summit area. Field investigation conducted immediately after the explosion confirmed the presence of thin ash deposits (0.5- 2.5 mm) approximately 9 km away from the crater in the NW and SW sectors. Several barangays in the municipalities of Juban and Irosin reported light ashfall. The Alert Level remained at 1 (on a scale of 0-5). Entry into the permanent danger zone, defined by a 4-km radius around the volcano, was prohibited.

During 15-16 May the seismic network detected four earthquakes. Then, on 16 May, the number of earthquakes rapidly increased to 80 in a seven-hour period. On 17 May PHIVOLCS reported that 144 earthquakes were recorded in the previous 24 hours. Steam rose from the active vents.

Geologic Summary. Luzon's southernmost volcano, Bulusan, was constructed within the 11-km-diameter dacitic Irosin caldera, which was formed more than 36,000 years ago. A broad, flat moat is located below the prominent SW caldera rim; the NE rim is buried by the andesitic Bulusan complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit of Bulusan volcano is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS) http://www.phivolcs.dost.gov.ph/


ETNA Sicily (Italy) 37.734°N, 15.004°E; summit elev. 3330 m

Sezione di Catania - Osservatorio Etneo reported that on 8 May mild and discontinuous Strombolian activity resumed at the pit crater located on the E flank of Etna's SE Crater cone. On 11 May volcanic tremor amplitude progressively increased, and at about 2030 lava started to overflow the E crater rim. The activity intensified during the following hours and, shortly before 0400 on 12 May, culminated with lava fountaining which generated an ash cloud that drifted SSE. The lava fountaining lasted around 2 hours, showing a gradual diminution around 0545; an abrupt drop in the volcanic tremor amplitude at 0610 marked the end of the eruptive activity.

Geologic Summary. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BC. Historical lava flows cover much of the surface of this massive basaltic stratovolcano, the highest and most voluminous in Italy. Two styles of eruptive activity typically occur at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater. Flank eruptions, typically with higher effusion rates, occur less frequently and originate from fissures that open progressively downward from near the summit. A period of more intense intermittent explosive eruptions from Etna's summit craters began in 1995. The active volcano is monitored by the Instituto Nazionale di Geofisica e Volcanologia (INGV) in Catania.

Source: Sezione di Catania - Osservatorio Etneo http://www.ct.ingv.it/


KIZIMEN Eastern Kamchatka (Russia) 55.130°N, 160.32°E; summit elev. 2376 m

KVERT reported that on 5 and 11 May seismicity from Kizimen was high; seismic data was not collected the other days during 6-13 May because of technical problems. Satellite images showed a large bright thermal anomaly daily on the volcano. During 6-7 May, ash plumes drifted 45 km SE and gas-and-steam plumes drifted 59 km N. Ashfall formed a layer as thick as 1 mm in Milkovo village, 120 km SW, on 10 May. A The Aviation Color Code remained at Orange.

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


TELICA Nicaragua 12.602°N, 86.845°W; summit elev. 1061 m

Based on reports from INETER, the Washington VAAC stated that emissions of gas-and-ash from Telica were detected and ash fell in areas 4 km N. Seismicity was elevated for a period of time.

Geologic Summary. Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. The Telica volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the Telica group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of 1061-m-high Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately SE of Telica, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.

Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html


TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m

IG reported that, although visual observations of Tungurahua during 11-15 May were often limited due to cloud cover, gas-and-steam plumes were noted during 12-14 May that rose 200-300 m above the crater and drifted E, SE, W, and NW. A small explosion on 15 May produced an ash plume that rose 500 m above the crater and drifted E. An ash plume the next day rose 200 m and drifted E. On 16 May an ash plume rose to an altitude of 8 km (26,200 ft) a.s.l. and drifted E, NE, and N. Incandescent blocks were ejected from the crater and rolled up to 500 m down the flanks. Ashfall was reported in the region of the Negro river.

Geologic Summary. The steep-sided Tungurahua stratovolcano towers more than 3 km above its northern base. It sits ~140 km S of Quito, Ecuador's capital city, and is one of Ecuador's most active volcanoes. Historical eruptions have all originated from the summit crater. They have been accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. The last major eruption took place from 1916 to 1918, although minor activity continued until 1925. The latest eruption began in October 1999 and prompted temporary evacuation of the town of Baños on the N side of the volcano.

Source: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/


ULAWUN New Britain 5.05°S, 151.33°E; summit elev. 2334 m

RVO reported that during 13-14 and 17 May gray-to-brown ash plumes rose above Ulawun. On 17 May the emissions were forceful for a short time and booming noises were reported. Light ashfall was reported in areas between Ubili in the NW and Voluvolu in the NE.

Geologic Summary. 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. Ulawun rises above the N coast of New Britain opposite Bamus volcano. The upper 1,000 m of the 2,334-m-high volcano is unvegetated. A steep-walled valley cuts the NW side of the volcano, and a flank lava-flow complex lies to the S 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.

Source: Rabaul Volcano Observatory (RVO)


YASUR Vanuatu (SW Pacific) 19.53°S, 169.442°E; summit elev. 361 m

On 12 May, the Vanuatu Geohazards Observatory reported that, based on information collected by the Vanuatu Meteorology and Geohazards Department, satellite imagery showed strong degassing from Yasur during the previous week. Residents living close to the volcano reported persistent strong explosions that were heard and felt on 12 May. The Vanuatu Volcano Alert Level (VVAL) remained at 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


BAGANA Bougainville 6.140°S, 155.195°E; summit elev. 1750 m

Based on analyses of satellite imagery, the Darwin VAAC reported that on 16 May an ash plume from Bagana rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 55 km NE.

Geologic Summary. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. Bagana is a massive symmetrical lava cone largely constructed by an accumulation of viscous andesitic lava flows. The entire lava cone could have been constructed in about 300 years at its present rate of lava production. Eruptive activity at Bagana is 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 volcano's flanks on all sides.

Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html


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 on 15 and 17 May ash plumes from Batu Tara rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted 75-130 km W and NW.

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


DUKONO Halmahera 1.68°N, 127.88°E; summit elev. 1335 m

Based on analyses of satellite imagery, the Darwin VAAC reported that during 11-12 May ash plumes from Dukono rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted 75-110 km NE and E. On 16 May an ash plume rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted over 90 km E.

Geologic Summary. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the N-flank cone of Gunung Mamuya. Dukono is a complex volcano presenting a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of Dukono's summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

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 6-13 May. Possible ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. on 10 May and to an altitude of 4.2 km (13,800 ft) a.s.l. on the other days. Pilots reported that on 6 May ash plumes rose to an altitude of 3 km (9,800 ft) a.s.l. Satellite imagery showed a thermal anomaly and ash plumes that drifted 340 km E during 6-7 May. 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


KATMAI Alaska Peninsula 58.280°N, 154.963°W; summit elev. 2047 m

Based on analysis of satellite imagery, pilot observations, KVERT reports, and information from AVO, the Anchorage VAAC reported that on 11 May strong winds in the Katmai area re-suspended loose ash deposited during the 1912 eruption. The Volcano Alert Level remained at Normal and the Aviation Color Code remained at Green.

Geologic Summary. Prior to 1912, Mount Katmai was a compound stratovolcano with four NE-SW-trending summits, most of which were truncated by caldera collapse in that year. Most of the two overlapping pre-1912 Katmai volcanoes are Pleistocene in age, but Holocene lava flows from a flank vent descend the SE flank of the SW stratovolcano into the Katmai River canyon. Katmai was initially considered to be the source of the Valley of Ten Thousand Smokes ash flow in 1912. However, the 3 x 4 km wide caldera of 1912 is now known to have formed as a result of the voluminous eruption at nearby Novarupta volcano. The steep walled young caldera has a jagged rim that rises 500-1,000 m above the caldera floor and contains a 250-m-deep, still-rising lake. Lake waters have covered a small post-collapse lava dome (Horseshoe Island) that was seen on the caldera floor at the time of the initial ascent to the caldera rim in 1916. Post-1912 glaciers have formed on a bench within Katmai caldera.

Source: Anchorage Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AK/messages.html


KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m

HVO reported that two lava lakes at Kilauea were active during 11-17 May. The level of the summit lava lake fluctuated but remained mostly stable deep in the vent inset within the E wall of Halema'uma'u Crater. Lava from a vent above the south side cascaded down into the lake. A gas plume from the vent generally drifted SW or W and deposited very small amounts of ash nearby. At Pu'u 'O'o crater, lava mostly from vents near the W edge of the lake continued to fill in a perched lava lake in the center of the crater floor. The lake level fluctuated and occasionally overflowed the edges, sending lava onto the Pu'u 'O'o crater floor.

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/


POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m

CENAPRED reported steam-and-gas emissions from Popocatépetl during 11-17 May. The emissions occasionally contained small amounts of ash during 14-17 May.

Geologic Summary. Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5,426 m 70 km SE of Mexico City and is North America's second-highest volcano. Frequent historical eruptions have been recorded since the beginning of the Spanish colonial era. A small eruption on 21 December 1994 ended five decades of quiescence. Since 1996 small lava domes have incrementally been constructed within the summit crater and destroyed by explosive eruptions. Intermittent small-to-moderate gas-and-ash eruptions have continued, occasionally producing ashfall in neighboring towns and villages.

Source: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.unam.mx/es/


SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m

Based on information from JMA, the Tokyo VAAC reported that during 11-18 May explosions from Sakura-jima sometimes produced plumes that rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. Plumes occasionally drifted SE and S. During 11, 13-14, and 17 May, pilots observed ash plumes that rose to altitudes of 2.1-3 km (7,000-10,000 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


SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m

INSIVUMEH reported that during 12-13 May explosions from Santa María's Santiaguito lava dome complex produced ash plumes that rose 900 m above Caliente dome and drifted SE, depositing fine ash in areas downwind. During 14-15 May explosions produced ash plumes that rose 2 km above Caliente dome. Pyroclastic flows descended the SW and E flanks. Rumbling noises and block avalanches were also noted. Ash was deposited on the E, S, SW, and W flanks including the communities of Loma Linda, San Marcos, and Palajunoj. During 16-17 May explosions produced ash plumes that rose 0.7-1 km above Caliente dome and drifted SW. A pyroclastic flow traveled E.

Geologic Summary. Symmetrical, forest-covered Santa María volcano is one of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1-km-wide crater, which formed during a catastrophic eruption in 1902 and extends from just below the summit to the lower flank. The renowned Plinian eruption of 1902 followed a long repose period and devastated much of SW Guatemala. The large dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, accompanied by almost continuous minor explosions and periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/


SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m

KVERT reported that during 5-7 May seismic data at Shiveluch indicated that possible ash plumes rose to an altitude of 3.9 km (12,800 ft) a.s.l. According to ground-based observations ash plumes rose to an altitude of 7.5 km (24,600 ft) a.s.l. on 7 May and to altitudes of 3-4 km (9,800-13,100 ft) a.s.l. during 5-6 and 8 May. Satellite imagery showed ash plumes drifting 196 km N during 5-6 May. On 7 May small ash clouds drifted S and SE, and gas-and-steam plumes drifted 230 km E. A thermal anomaly was detected during 7-8 May. KVERT noted that the Aviation Color Code remained at Orange. Based on information from KEMSD, the Tokyo VAAC reported that on 15 May an eruption produced a plume that rose to an altitude of 6.1 km (20,000 ft) a.s.l. and drifted E.

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 6-13 May activity at the Soufrière Hills lava dome was at a low level. On 11 May a pyroclastic flow that occurred in the February 2010 collapse scar traveled about 1 km. An ash cloud rose 1.8 km and drifted NNE, causing light ashfall in Lookout village. 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/

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