*************************************************************************** SI/USGS Weekly Volcanic Activity Report 30 December 2009-5 January 2010 From: "Sally Kuhn Sennert" <KUHNS@xxxxxx> *************************************************************************** SI/USGS Weekly Volcanic Activity Report 30 December 2009-5 January 2010 Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Galeras, Colombia | Mayon, Luzon | Nyamuragira, Democratic Republic of Congo | Piton de la Fournaise, Reunion Island | Rinjani, Lombok Island (Indonesia) | Tungurahua, Ecuador | Turrialba, Costa Rica Ongoing Activity: | Barren Island, Andaman Is | Chaitén, Southern Chile | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Kliuchevskoi, Central Kamchatka (Russia) | Nevado del Huila, Colombia | Rabaul, New Britain | Sakura-jima, Kyushu | Sangay, Ecuador | Santa María, Guatemala | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Suwanose-jima, Ryukyu Islands (Japan) 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 GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m An explosive eruption from Galeras detected by the seismic network on 2 January prompted INGEOMINAS to raise the Alert Level to I (Red; "imminent eruption or in progress"). An ash plume rose to an altitude of 12 km (39,400 ft) a.s.l. and drifted W and NW. Ashfall was reported in areas downwind, as far away as 110 km W. Ejected incandescent blocks fell onto the flanks 3.2-3.5 km away from the summit and ignited fires. An overflight on 3 January revealed diffuse gas plumes from the main crater. Fires started the previous day continued to burn on the N flank. The Alert Level was lowered to II (Orange; "probable eruption in term of days or weeks"). Geologic Summary. Galeras, a stratovolcano with a large breached caldera located immediately W of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic Galeras volcanic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Longterm extensive hydrothermal alteration has affected the volcano. This has contributed to large-scale edifice collapse that has occurred on at least three occasions, producing debris avalanches that swept to the W 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. Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co// MAYON Luzon 13.257°N, 123.685°E; summit elev. 2462 m PHIVOLCS reported declining activity at Mayon from 28 December to 2 January. Steam plumes were emitted from the crater, but ash plumes were last seen on 29 December. In addition, the majority of the seismic signals originated from rockfalls and detached lava fragments rolling down the flanks from advancing lava flows. Sulfur dioxide emissions also decreased from close to 9,000 tonnes per day to about 2,600 tonnes per day. PHIVOLCS lowered the Alert Level from 4 to 3, and reminded the public that no human activity should occur within the 6-km radius Permanent Danger Zone (PDZ) around the volcano and the 7-km Extended Danger Zone (EDZ) on the SE flank. During 2-5 January, seismic activity indicated rockfall events related to the detachment of lava fragments at the upper slopes. Cloud cover at the summit prevented observations of steam plumes. Incandescence from the crater at night was noted. 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/ NYAMURAGIRA Democratic Republic of Congo 1.408°S, 29.20°E; summit elev. 3058 m According to news articles, Nyamuragira erupted on 2 January from a fissure on the SE flank. Park rangers reported hearing a loud explosion in the early morning before seeing flowing lava. By 3 January, the lava flow had traveled 4.6 km, was 15 m wide, and had burned about 10 hectares of forest in a non-populated area of the Virunga National Park. Geologic Summary. Africa's most active volcano, Nyamuragira (Also spelled Nyamulagira) is a massive basaltic shield volcano N of Lake Kivu and NW of Nyiragongo volcano. Lava flows from Nyamuragira cover 1,500 sq km of the East African Rift. The 3058-m-high summit is truncated by a small 2 x 2.3 km summit caldera that has walls up to about 100 m high. About 40 historical eruptions have occurred since the mid-19th century within the summit caldera and from numerous fissures and cinder cones on the volcano's flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938. Twentieth-century flank lava flows extend more than 30 km from the summit, reaching as far as Lake Kivu. Sources: CNN http://www.cnn.com/2010/WORLD/africa/01/02/congo.volcano/index.html?eref=ib_topstories, Agence France-Presse http://www.google.com/hostednews/afp/article/ALeqM5gttS1HfXOoqOMHLFL5jN2ek4Q9cA, UN News Centre http://www.un.org/apps/news/story.asp?NewsID=33396&Cr=&Cr1=, United Nations Organization Mission in the Democratic Republic of the Congo (MONUC) http://monuc.unmissions.org/Default.aspx?tabid=932&ctl=Details&mid=2070&ItemID=7098 PITON DE LA FOURNAISE Reunion Island 21.231°S, 55.713°E; summit elev. 2632 m OVPDLF reported that a seismic crisis at Piton de la Fournaise on 29 December was characterized by numerous earthquakes in the area W and NW of Dolomieu crater (max M 3), at depths of 1.1-2.2 km below the summit. Deformation was also detected. On 31 December, OVPDLF reported decreased seismicity and fewer landslides within Dolomieu crater on 30 and 31 December. On 2 January, an eruption from a fissure near the top of the W crater rim, preceded by a seismic crisis, produced lava fountains a few tens of meters high and lava flows in Dolomieu crater. Large landslides in Bory crater (W) along with the fissure eruption generated ash and gas plumes that rose above Piton de la Fournaise. During 2-3 January, seismicity and the number of landslides decreased. As of 4 January, the lava flows covered about 80 percent of the crater floor. Lava fountaining was still visible. Geologic Summary. Massive Piton de la Fournaise shield volcano on the island of Réunion is one of the world's most active volcanoes. Most historical eruptions have originated from the summit and flanks of a 400-m-high lava shield, Dolomieu, that has grown within the youngest of three large calderas. This depression is 8 km wide and is breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows within the caldera, have been documented since the 17th century. The volcano is monitored by the Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris. Source: Observatoire Volcanologique du Piton de la Fournaise (OVPDLF) http://www.ipgp.fr/pages/03030810.php RINJANI Lombok Island (Indonesia) 8.42°S, 116.47°E; summit elev. 3726 m Based on a pilot report, the Darwin VAAC reported that on 2 January an ash plume from Rinjani rose to an unspecified altitude. The plume was not identified in satellite imagery; however a meteorological cloud was present in the area. Geologic Summary. Rinjani volcano on the island of Lombok rises to 3,726 m, second in height among Indonesian volcanoes only to Sumatra's Kerinci volcano. Rinjani has a steep-sided conical profile when viewed from the E, but the W side of the compound volcano is truncated by the 6 x 8.5 km, oval-shaped Segara Anak caldera. The western half of the caldera contains a 230-m-deep lake whose crescentic form results from growth of the post-caldera cone Barujari at the E end of the caldera. Historical eruptions at Rinjani dating back to 1847 have been restricted to Barujari cone and consist of moderate explosive activity and occasional lava flows that have entered Segara Anak lake. Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m The IG reported steam emissions from Tungurahua during 30 December-3 January. On 1 January, an ash plume rose to an altitude of 5.9 km (19,500 ft) a.s.l. and drifted NW. Slight ashfall was reported the next day in Manzano, 8 km SW. Roaring noises and incandescence from the crater were also reported. On 3 and 4 January, incandescent blocks were ejected from the crater. Based on information from the Guayaquil MWO and SIGMET notices, the Washington VAAC reported that ash plumes rose to altitudes of 6.7-9.1 km (22,000-30,000 ft) a.s.l. and drifted W. Thermal anomalies were detected in satellite imagery. On 4 January, ashfall was reported in areas to the W and SW. 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. Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/, Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html TURRIALBA Costa Rica 10.025°N, 83.767°W; summit elev. 3340 m On 5 January, OVSICORI-UNA reported that an eruption from Turrialba produced ashfall in local areas, particularly in areas to the SW, including near Irazú volcano (11 km SW). According to news articles, about 20 people evacuated the area. Geologic Summary. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m wide summit depression that is breached to the NE. Most activity at Turrialba originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred at Turrialba during the past 3500 years. Turrialba has been quiescent since a series of explosive eruptions during the 19th century that were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters. Sources: Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/, Reuters http://www.reuters.com/article/idUSTRE6050FS20100106 Ongoing Activity BARREN ISLAND Andaman Is 12.278°N, 93.858°E; summit elev. 354 m Based on a pilot report, the Darwin VAAC reported that on 3 January a plume from Barren Island rose to an altitude of 1.5 km (5,000 ft) a.s.l. The plume was not identified in satellite imagery; however a meteorological cloud was present in the area. Geologic Summary. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S-trending volcanic arc extending between Sumatra and Burma (Myanmar). The 354-m-high island is the emergent summit of volcano that rises from a depth of about 2,250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the W, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. The morphology of a fresh pyroclastic cone that was constructed in the center of the caldera has varied during the course of historical eruptions. Lava flows fill much of the caldera floor and have reached the sea along the western coast during historical eruptions. Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m Based on web camera views, the Buenos Aires VAAC reported that a plume from Chaitén's lava-dome complex drifted SE on 30 December at an altitude of 2.1 km (7,000 ft) a.s.l. Geologic Summary. Chaitén is a small, glacier-free caldera with a Holocene lava dome located 10 km NE of the town of Chaitén on the Gulf of Corcovado. A pyroclastic-surge and pumice deposit considered to originate from the eruption that formed the elliptical 2.5 x 4 km wide summit caldera was dated at about 9400 years ago. A rhyolitic, 962-m-high obsidian lava dome occupies much of the caldera floor. Obsidian cobbles from this dome found in the Blanco River are the source of prehistorical artifacts from archaeological sites along the Pacific coast as far as 400 km away from the volcano to the north and south. The caldera is breached on the SW side by a river that drains to the bay of Chaitén, and the high point on its southern rim reaches 1122 m. Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m KVERT reported that a thermal anomaly over Karymsky was detected in satellite imagery during 24-26 and 29-30 December. Gas-and-steam bursts were seen by volcanologists on 28 December. The Level of Concern 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 During 30 December-3 January, HVO reported that lava flowed SE from beneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex through a lava tube system, reaching the ocean at Waikupanaha. Lava was not seen entering the ocean on 4 and 5 January. Thermal anomalies detected by satellite and occasional visual observations revealed active lava flows on the pali. Incandescence was seen almost daily coming from Pu'u 'O'o crater. During an overflight of Pu'u 'O'o crater on 29 December, geologists saw that a part of the high point of the W rim had collapsed, and a new gas vent had opened up at base of the N wall. The vent in Halema'uma'u crater continued to produce a plume that drifted NE and NW, dropping small amounts of ash, and occasionally fresh spatter, downwind. Incandescence originated from an active and sometimes sloshing lava surface within an opening on the deep floor of the vent cavity. 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/ KLIUCHEVSKOI Central Kamchatka (Russia) 56.057°N, 160.638°E; summit elev. 4835 m KVERT reported that during 24-31 December seismic activity from Kliuchevskoi was above background levels and lava continued to flow down the ESE flank. Strombolian activity ejected material 500 m above the crater. Satellite imagery revealed a large daily thermal anomaly at the volcano. The Level of Concern Color Code remained at Orange. Geologic Summary. Kliuchevskoi is Kamchatka's highest and most active volcano. Since its origin about 7,000 years ago, the beautifully symmetrical, 4,835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. More than 100 flank eruptions, mostly on the NE and SE flanks of the conical volcano between 500 m and 3,600 m elevation, have occurred during the past 3,000 years. The morphology of its 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included major explosive and effusive events from flank craters. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5364 m Based on web camera views, INGEOMINAS reported that during 23-29 December a continuous white plume from Nevado del Huila rose 1 km. The output of sulfur dioxide was less than during the previous months of October and November. Seismicity and the rate of lava extrusion had also decreased during the previous weeks. On 5 January, INGEOMINAS lowered the Alert Level to III (Yellow; "changes in the behavior of volcanic activity"). Geologic Summary. Nevado del Huila, the highest active volcano in Colombia, is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The andesitic-dacitic volcano was constructed within a 10-km-wide caldera. Volcanism at Nevado del Huila has produced six volcanic cones whose ages in general migrated from south to north. Two glacier-free lava domes lie at the southern end of the Huila volcanic complex. The first historical eruption from this little known volcano took place in the 16th century. Two persistent steam columns rise from the central peak, and hot springs are also present. Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co// RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m RVO reported that activity from Rabaul caldera's Tavurvur cone was at a low level during 21-31 December; no emission from the crater was observed on most days. White steam plumes accompanied by blue plumes were occasionally emitted. On 23 December, ash emissions rose less than 200 m above the cone. Based on analyses of satellite imagery, the Darwin VAAC reported that on 31 December an ash plume rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted less than 30 km SE. Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. 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 E, where its floor is flooded by Blanche Bay. Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. 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. Sources: Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m Based on information from JMA, the Tokyo VAAC reported that during 30 December-5 January multiple explosions from Sakura-jima often produced plumes that rose to altitudes of 1.2-2.7 km (4,000-9,000 ft) a.s.l. and drifted NE, E, SE, and S. During 31 December-4 January pilots reported that ash plumes rose to altitudes of 2.4-5.5 km (8,000-18,000 ft) a.s.l. and drifted SE and E. 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 SANGAY Ecuador 2.002°S, 78.341°W; summit elev. 5230 m The Washington VAAC reported that during 2-4 January thermal anomalies from Sangay were seen in satellite imagery. On 2 January, a pilot saw an ash plume drifting NW at an altitude of 7 km (23,000 ft) a.s.l. An ash plume was also reported by a pilot the next day. Geologic Summary. The isolated Sangay volcano, located E of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. It has been in frequent eruption for the past several centuries. The steep-sided, 5,230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the E, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. Sangay towers above the tropical jungle on the E side; on the other sides flat plains of ash from the volcano have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The more or less constant eruptive activity has caused frequent changes to the morphology of the summit crater complex. Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m On 30 December and 5 January, INSIVUMEH reported that explosions from Santa María's Santiaguito lava dome complex produced ash plumes that rose to altitudes of 3-3.4 km (10,000-11,200 ft) a.s.l. and drifted W and SW. The Washington VAAC reported that ash plumes seen on satellite imagery drifted more than 30 km WSW. Avalanches occasionally descended the SW flank of the dome. 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. Sources: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/ , Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m KVERT reported that during 24-31 December seismic activity from Shiveluch was above background levels, possibly indicating ash plumes rising to an altitude of 4.9 km (16,000 ft) a.s.l. Fumarolic activity was occasionally seen when the weather was clear. Analyses of satellite imagery revealed a large daily thermal anomaly from the lava dome and an ash plume that drifted 15 km W on 28 December. The Level of Concern Color Code remained at Orange. Based on information from KEMSD and KVERT, the Tokyo VAAC reported that during 30 December-3 January eruptions produced plumes that rose to altitudes of 4.3-7.6 km (14,000-25,000 ft) a.s.l. 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 24-31 December activity from the Soufrière Hills lava dome continued at a high level. Cycles of increased activity associated with vigorous ash venting and pyroclastic flows occurred every six to eight hours. Audible rockfalls, roaring, and occasional thunder were noted during the most intense events. Frequent pyroclastic flows traveled N down Whites Ghaut, Farrells plain, and Tyers Ghaut. Pyroclastic flows also traveled W down Gages Valley into Spring Ghaut, and occasionally to the S in Gingoes Ghaut. On 29 December several pyroclastic flows traveled 2.5 km, reaching Dyers village. A comparison of photographs from 30 December and 2 January revealed that the lava dome morphology had changed rapidly, with a significant addition of lava on the N side. The additional area of growth was approximately 60 m high and 100 m wide. The Hazard Level remained at 4. 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/ SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m Based on information from JMA, the Tokyo VAAC reported explosions from Suwanose-jima during 30 December-2 January and 4-5 January. Plumes rose to altitudes of 1.5-1.8 km (5,000-6,000 ft) a.s.l. on 2 and 4 January, and drifted NE and E on 4 January. Geologic Summary. The 8-km-long, spindle-shaped island of Suwanose-jima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. Only about 50 persons live on the sparsely populated island. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanose-jima, one of Japan's most frequently active volcanoes, was in a state of intermittent Strombolian activity from On-take, the NE summit crater, that began in 1949 and lasted nearly a half century. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, after which the island was uninhabited for about 70 years. The SW crater produced lava flows that reached the western coast in 1813, and lava flows reached the eastern coast of the island in 1884. Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html ============================================================== To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
