******************************************************** SI/USGS Weekly Volcanic Activity Report 5-11 November 2008 ******************************************************** Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Dalaffilla, Northeastern Africa | Machín, Colombia | Nevado del Huila, Colombia | Redoubt, Southwestern Alaska | Reventador, Ecuador Ongoing Activity: | Batu Tara, Komba Island (Indonesia) | Chaitén, Southern Chile | Dukono, Halmahera (Indonesia) | Galeras, Colombia | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Kliuchevskoi, Central Kamchatka (Russia) | Popocatépetl, México | Rabaul, New Britain (SW Pacific) | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Suwanose-jima, Ryukyu Islands (Japan) | Tungurahua, Ecuador 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 DALAFFILLA Northeastern Africa 13.792°N, 40.55°E; summit elev. 613 m An eruption of a volcano NW of Erta Ale in Ethiopia's Afar region began on 3 November. Satellite imagery showed a large sulfur dioxide cloud that drifted E over the Arabian Peninsula. According to news articles, observers reported ground shaking, hearing loud noises and explosions from a distance, and seeing smoke. Widespread lava flows were also noted. Extensive thermal anomalies near Dalafilla and Alu volcanoes were detected, consistent with lava effusion, although the source of the lava flows was not known. Thermal anomalies continued to be detected during 3-11 November. Geologic Summary. Dalaffilla, also referred to as Gabuli, is a small, but steep-sided conical stratovolcano that rises 300 m above surrounding lava fields SE of Alu volcano. This morphology, unusual for the Erta Ale Range volcanoes, results from the extrusion of viscous, silicic lava flows with primary slopes up to about 35 degrees. These silicic flows extend primarily to the east; on the west they are blocked by walls of a horst structure along the crest of the Erta Ale range. Other basaltic lava flows from regional fissures surround the 613-m-high volcano. Fumarolic activity occurs in the 100-m-wide summit crater and has weathered surrounding lava flows. Sources: OMI Sulfur Dioxide Group http://so2.umbc.edu/omi/, Hawai'i Institute of Geophysics and Planetology (HIGP) Thermal Alerts System http://hotspot.higp.hawaii.edu, Bloomberg http://www.bloomberg.com/apps/news?pid=20601116&sid=ac6MyrqEVR0M MACHIN Colombia 4.48°N, 75.392°W; summit elev. 2650+ m Observatory Vulcanológico and Sismológico de Manizales reported a seismic crisis at Cerro Machín on 9 November. The majority of the earthquakes occurred underneath the central and E parts of the lava dome complex in the summit caldera, at depths of 2.5-5 km. Fumarolic activity in the area increased, and cracks in the ground and damage to houses were reported. Seismicity decreased the next day. According to news articles, approximately 400-450 people evacuated to shelters or other safe areas and landslides blocked a highway. Geologic Summary. The small Cerro Machín stratovolcano lies at the southern end of the Ruiz-Tolima massif about 20 km WNW of the city of Ibagué. A 3-km-wide caldera is breached to the S and contains three forested lava domes. Voluminous pyroclastic flows traveled up to 40 km from the volcano during eruptions in the mid-to-late Holocene perhaps associated with formation of the caldera. Late-Holocene eruptions produced block-and-ash flows that traveled through the breach in the caldera rim to the W and S. The latest known eruption of Volcán Cerro Machín took place about 800 years ago. Sources: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co//, Caracol http://www.caracol.com.co/nota.aspx?id=707620, El Tiempo http://www.eltiempo.com/colombia/tolima/actividad-sismica-del-volcan-machin-desplaza-a-mas-de-400-personas-de-sus-tierras_4657403-1, Portafolio http://www.portafolio.com.co/economia/pais/2008-11-11/ARTICULO-WEB-NOTA_INTERIOR_PORTA-4657023.html NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5365 m On 7 November, INGEOMINAS raised the Alert Level for Nevado del Huila to Orange (on a 4-color scale where Orange is the second highest) due to increased seismicity and the probability of ash and gas emissions. During an overflight on 9 November, scientists observed continuous emissions of ash and gas from Pico Central, including from new areas to the S. Resultant plumes drifted SW and W, and ash deposits were seen on the summit. Fissures were evident on the S and SW parts of Pico Central. Evidence of ash and flowing water that originated from the SW fissure was possibly the cause of the Páez river turning grayish during the previous few days. Based on analysis of satellite imagery and information from INGEOMINAS, the Washington VAAC reported that on 10 November a plume drifted W and WSW. Ashfall was noted in towns 20 km NW. According to news articles, ash and sulfur dioxide plumes impacted local livestock, rural aqueducts, infrastructure, and rivers. On 11 November, about 20 families living near the Símbola River evacuated because of increased fumarolic 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. Sources: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co//, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html, El Pais http://www.elpais.com.co/paisonline/notas/Noviembre072008/nal6.html, La Patria http://www.lapatria.com/Noticias/ver_noticia.aspx?CODNOT=52550&CODSEC=5 REDOUBT Southwestern Alaska 60.485°N, 152.742°W; summit elev. 3108 m On 5 November, AVO raised the Aviation Color Code for Redoubt to Yellow and the Volcano Alert Level to Advisory because of significant changes in gas emission and heat output during the previous several months. The changes were a departure from the long-observed background activity. ASTER satellite images from 13 October detected warming near the summit craters; evidence of warming had been directly observed in July 2008. Fumarolic activity and water flowing beneath Drift Glacier on the N flank had produced a 45-m-wide melt or collapse hole at an elevation of about 1,700 m (5,600 ft) on the Drift Glacier. On 2 November, a slushy debris-flow deposit originated from about the location of the 1966-68 vent. During 6-11 November, no activity was observed on satellite imagery and seismicity remained low. Geologic Summary. Redoubt is a 3108-m-high glacier-covered stratovolcano with a breached summit crater in Lake Clark National Park about 170 km SW of Anchorage. Next to Mount Spurr, Redoubt has been the most active Holocene volcano in the upper Cook Inlet. Collapse of the summit of Redoubt 10,500-13,000 years ago produced a major debris avalanche that reached Cook Inlet. Holocene activity has included the emplacement of a large debris avalanche and clay-rich lahars that dammed Lake Crescent on the south side and reached Cook Inlet about 3500 years ago. Eruptions during the past few centuries have affected only the Drift River drainage on the north. Historical eruptions have originated from a vent at the north end of the 1.8-km-wide breached summit crater. The 1989-90 eruption of Redoubt had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano. Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/ REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m The IG reported that SOTE (Sistema de Oleoducto Transecuatoriano) personnel and residents near Reventador observed incandescence in the crater on 7 November. The reports were confirmed by the presence of thermal anomalies in satellite imagery. The next day, seismicity increased and a steam-and-ash plume rose to an approximate altitude of 5.6 km (18,400 ft) a.s.l. and drifted SW. Incandescent blocks were ejected from the inner crater to the S. Residents in El Chaco (about 35 km SE) and in the Quijos area heard strong explosions and saw steam plumes with low ash content. A pilot reported that a steam plume with little ash content at an altitude of 7.6 km (25,000 ft) a.s.l. drifted NW. On 9 November incandescent blocks were ejected 100 m into the air, and roaring and "cannon shot" sounds were reported. Strombolian activity and two lava flows that descended the N and S flanks of the central cone were observed using a permanent camera. Slight ashfall was noted in Cayambe, about 55 km WNW. A thermal anomaly was detected by satellite imagery on 9 and 10 November. On 10 November, seismicity considerably decreased and gas emissions continued. The lava flows continued to advance. According to a news article, officials suspended flights into Quito airport due to ash plumes on 10 November for three hours as a preventative measure. Geologic Summary. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well E of the principal volcanic axis. It is a forested stratovolcano that rises above the remote jungles of the western Amazon basin. A 3-km-wide caldera breached to the E was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1,300 m above the caldera floor. Reventador has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html, Associated Press http://ap.google.com/article/ALeqM5gwl-oHY3etHDNcWqnkELet3RFMDgD94C87UO0 Ongoing Activity BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m Based on analysis of satellite imagery, the Darwin VAAC reported that during 9-10 November ash plumes from Batu Tara rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted 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 CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m SERNAGEOMIN reported that on 5 November the S bank of the Chaitén River (locally known as the Blanco) had overflowed and flooded local houses due to intense rains a few days before. Based on observations of satellite imagery and web camera views, the Buenos Aires VAAC reported that during 9-11 November ash plumes from Chaitén rose to altitudes 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted ESE, E, and NE. A thermal anomaly was present on 10 November. 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. 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 DUKONO Halmahera (Indonesia) 1.68°N, 127.88°E; summit elev. 1335 m Based on analysis of satellite imagery, the Darwin VAAC reported that during 6-7 November ash plumes from Dukono rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted WNW. 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 GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m On 11 November, INGEOMINAS reported that during the previous week pulsating white plumes, occasionally tinged gray, rose from Galeras to altitudes of 4.5-5.7 km (14,800-18,700 ft) a.s.l. and drifted W. 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// KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m KVERT reported that seismic activity at Karymsky was above background levels during 31 October and 2-3 November and at background levels on the other days during 1-7 November. Possible explosions on 31 October, and 2 and 3 November may have generated ash plumes to an altitude of 3.8 km (12,500 ft) a.s.l. Analysis of satellite imagery revealed a thermal anomaly in the crater on 31 October, and 2 and 6 November; clouds prevented observations on the other days. The Level of Concern Color Code remained at Orange. Based on analysis of satellite imagery and information from KEMSD, the Tokyo VAAC reported that an eruption generated a plume to an altitude of 3.7 km (12,000 ft) a.s.l. on 11 November. 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. 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 KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m HVO reported that during 5-11 November lava flowed SE through a tube system from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex, reaching the Waikupanaha ocean entry. Thermal anomalies detected on satellite imagery indicated active surface flows. The sulfur dioxide emission rate at Pu'u 'O'o was 2,000 tonnes per day on 7 November, near the 2005-2007 average background rate of 1,700 tonnes per day. During the reporting period, Kilauea earthquakes were variously located beneath and to the S of the caldera and along the S-flank fault. Beneath Halema'uma'u crater earthquakes ranged from 40 to 60 (background is about 40), but were too small to be located more precisely. The vent in Halema'uma'u crater continued to produce a white plume that occasionally turned brown and drifted mainly SW. Night-time incandescence was intermittently seen at the base of the plume, and sounds resembling distant surf and rock clattering were heard in the vicinity of the crater. The sulfur dioxide emission rate was 900 tonnes per day on 7 November. The 2003-2007 rate average was 140 tonnes per day. 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 seismic activity at Kliuchevskoi was above background levels during 31 October-7 November. Video and visual observations showed that during 31 October, and 1-2 and 5-6 November, gas-and-steam plumes that contained a small amount of ash rose to an altitude of 5.2 km (17,100 ft) a.s.l. On 3 and 4 November, "bursting" sounds from the volcano were heard in Klyuchi, about 30 km to the NE. Analysis of satellite imagery revealed a daily thermal anomaly in the crater. The Level of Concern Color Code remained 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 POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m CENAPRED reported that emissions of steam and gas from Popocatépetl were visible during 5-11 November. The plumes occasionally contained slight amounts of ash on 5 November. 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/ RABAUL New Britain (SW Pacific) 4.271°S, 152.203°E; summit elev. 688 m RVO reported that during 3-6 November ash plumes from Rabaul caldera's Tavurvur cone rose to altitudes of 1.7-2.2 km (5,600-7,200 ft) a.s.l. and drifted NW. Ashfall was reported in areas downwind. Sub-continuous incandescence from the vent was observed, and rumbling and roaring noises were reported on some days. Explosions or forceful emissions sometimes ejected incandescent lava fragments. Based on analysis of satellite imagery, the Darwin VAAC reported that during 7 and 9-12 November ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted N and NW. 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: Herman Patia, Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m KVERT reported that seismic activity at Shiveluch was above background levels during 31 October-7 November. Based on interpretations of seismic data, ash plumes rose to an altitude of 5.2 km (17,100 ft) a.s.l. A large number of daily hot avalanches were observed descending the lava dome and producing ash plumes on 2, 3, and 5 November that rose to an altitude of 3.5 km (11,500 ft) a.s.l. Fumarolic activity was visible on the web camera during 2-3 and 5-6 November. Analysis of satellite imagery revealed a thermal anomaly on the lava dome on 31 October and 1, 2, 3, and 6 November. The Level of Concern Color Code remained at Orange. Based on information from KEMSD and analysis of satellite imagery, the Tokyo VAAC reported that during 8-10 November eruptions produced plumes to altitudes of 4.9-5.8 km (16,000-19,000 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. During the 1990s, intermittent explosive eruptions took place 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 31 October-7 November the activity level at the Soufrière Hills lava dome was low and there was no evidence of lava extrusion. Photographs taken during an aerial inspection of the dome confirmed that the SE side was a very high (150-200 m) free-standing cliff not supported by talus. Erosion continued on the NE side and at the E and SE bases of the dome, further deepening the moat in the talus around the dome. The morphology of the top of the dome was complex and highly irregular with multiple steep lava protrusions separated by areas of lower elevation. Several spines and a bulbous shear lobe were visible. 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 SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m Based on pilot observations and analysis of satellite imagery, the Tokyo VAAC reported that on 5 November an ash plume from Suwanose-jima rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted NE. The JMA indicated that during 7-8 November explosion or eruption plumes rose to altitudes of 1.2-1.8 km (4,000-6,000 ft) a.s.l. and drifted E. An explosion was reported on 12 November. 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 TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m The IG reported little observed activity from Tungurahua during 5-11 November. Light ashfall was reported in Pillate (8 km W) and part of Riobamba (about 30 km S) on 4 November. Fumarolic activity was weak on 7 November and present on the NW edge of the crater on 8 November. 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/ +++++++++++++++++++++++++++++++++++++ Sally Kuhn Sennert SI/USGS Weekly Volcanic Activity Report Editor Global Volcanism Program http://www.volcano.si.edu/reports/usgs/ Smithsonian Institution, National Museum of Natural History Department of Mineral Sciences, MRC-119 Washington, D.C., 20560 Phone: 202.633.1805 Fax: 202.357.2476 ============================================================== 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. ==============================================================
