************************************************************ SI/USGS Weekly Volcanic Activity Report 19-25 November 2008 ************************************************************ Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Dalaffilla, Northeastern Africa | Dukono, Halmahera (Indonesia) | Kliuchevskoi, Central Kamchatka (Russia) | Manam, Northeast of New Guinea (SW Pacific) | Nevado del Huila, Colombia | Reventador, Ecuador | San Cristóbal, Nicaragua Ongoing Activity: | Bagana, Bougainville Island (SW Pacific) | Chaitén, Southern Chile | Etna, Sicily (Italy) | Fuego, Guatemala | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Pacaya, Guatemala | 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 During 19-24 November, the MODIS satellite continued to detect thermal anomalies over the area near Dalaffilla and Alu volcanoes from the eruption that began on 3 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. Source: Hawai'i Institute of Geophysics and Planetology (HIGP) Moderate Resolution Imaging Spectroradiometer (MODIS) Thermal Alert System http://modis.higp.hawaii.edu/ DUKONO Halmahera (Indonesia) 1.68°N, 127.88°E; summit elev. 1335 m Based on analysis of satellite imagery, the Darwin VAAC reported that on 20 November an ash plume from Dukono rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 110 km NW. 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 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 14-21 November and Strombolian activity continued. Video and visual observations showed that during 13-17 November gas-and-steam plumes containing a small amount of ash rose to an altitude of 5.3 km (17,400 ft) a.s.l. On 17 November, "bursting" sounds from the volcano were heard in Klyuchi, about 30 km to the NE. Analysis of satellite imagery revealed a large daily thermal anomaly in the crater during 14-21 November. On 22 November a lava flow traveled 1.5-1.8 km down the NW flank. 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 MANAM Northeast of New Guinea (SW Pacific) 4.080°S, 145.037°E; summit elev. 1807 m Based on analysis of satellite imagery, the Darwin VAAC reported that on 20 November an ash plume from Manam rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted about 55 km NW. Geologic Summary. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic stratovolcano to its lower flanks. These "avalanche valleys," regularly spaced 90 degrees apart, channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE avalanche valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded at Manam since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas. Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5365 m INGEOMINAS reported an eruption of Nevado del Huila at 2145 on 20 November that destroyed part of a new lava dome that had formed during the previous months. The Alert Level was raised to Red (on a 4-color scale where Red is the highest level). According to the Washington VAAC, two gas-and-ash plumes rose to altitudes of 12.4-15.4 km (40,700-50,500 ft) a.s.l. and drifted W and SE. Hot material erupted at the summit melted areas of the surrounding glacier and caused lahars in the Bellavista and Páez rivers. Lahars in the Páez River damaged infrastructure and destroyed homes, and residents of Taravira, Tóez, and La Estrella reported abundant ashfall and noises associated with both the eruption and the lahar. There may have been as many as 10 fatalities and 10 others were missing, and several populations were left without means of communication. By the time of a report at 0230 on 21 November, the seismicity had decreased. During an overflight, scientists observed a 400-m-dimater crater in the SW area of Pico Central. A lava dome inside the crater was degassing. Intense fumarolic activity was noted from the W end of a crack generated in April 2007. The next day, the Alert Level was lowered back to Orange because seismicity had returned to background levels. INGEOMINAS continued to receive reports of sulfur odors and continuous gas emissions from the summit. According to news reports, the lahars damaged or destroyed about 70 homes and several bridges, and displaced many families. Hundreds of people were evacuated. 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//, Latin America Herald Tribune http://www.laht.com/article.asp?ArticleId=321299&CategoryId=12393, EFE http://www.elperiodicodearagon.com/noticias/noticia.asp?pkid=458207 REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m Inclement weather prevented observations of Reventador during 19-23 November. A seismic station situated on the NE flank of the central cone recorded a high number of rockfall signals that presumably originated from the active lava-flow fronts. 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. Source: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/ SAN CRISTOBAL Nicaragua 12.702°N, 87.004°W; summit elev. 1745 m According to a news article, seismic activity from San Cristóbal increased on 14 and 17 November. The article also noted that INETER reported explosions and subsequent ash-and-gas emissions from the crater on 21 November. Ashfall was reported in areas to the S. Geologic Summary. The San Cristóbal volcanic complex, consisting of five principal volcanic edifices, forms the NW end of the Marrabios Range. The symmetrical 1,745-m-high youngest cone, San Cristóbal itself (also known as El Viejo), is Nicaragua's highest volcano and is capped by a 500 x 600 m wide crater. El Chonco, with several flank lava domes, is located 4 km to the west of San Cristóbal; it and the eroded Moyotepe volcano, 4 km to the NE of San Cristóbal, are of Pleistocene age. Volcán Casita contains an elongated summit crater and lies immediately E of San Cristóbal; Casita was the site of a catastrophic landslide and lahar in 1998. The Plio-Pleistocene La Pelona caldera is located at the eastern end of the San Cristóbal complex. Historical eruptions from San Cristóbal, consisting of small-to-moderate explosive activity, have been reported since the 16th century. Some other 16th-century eruptions attributed to Casita volcano are uncertain and may pertain to other Marrabios Range volcanoes. Source: Agence France-Presse http://www.elnuevodiario.com.ni/nacionales/33078 Ongoing Activity BAGANA Bougainville Island (SW Pacific) 6.140°S, 155.195°E; summit elev. 1750 m Based on analysis of satellite imagery, the Darwin VAAC reported that on 20 November an ash plume from Bagana rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted about 75 km SW. On 26 November a low-level plume drifted W. 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 CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m On 25 November SERNAGEOMIN reported that continuous emissions of gas and ash from Chaitén produced plumes that rose to altitudes of 2.6-3.1 km (8,500-10,200 ft) a.s.l. A lateral explosion was observed on the web camera on 17 November. Based on observations of satellite imagery, SIGMET notices, and web camera views, the Buenos Aires VAAC reported that during 19-21, 23, and 25 November ash plumes continuously rose to altitudes 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted ESE, SE, and S. 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 ETNA Sicily (Italy) 37.734°N, 15.004°E; summit elev. 3330 m INGV-CT reported that an inspection of Etna's summit craters on 19 November revealed degassing from the Northeast Crater and, to a lesser degree, from the Bocca Nuova BN-1 crater. A 100-m-long lava flow was active in mid-November; the lava flow field on the upper Valle del Bove has been active since 13 May. 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: Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania (INGV-CT) http://www.ct.ingv.it/ FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m INSIVUMEH reported that during 20-21 and 25 November explosions from Fuego produced ash plumes that rose to altitudes of 4.1-4.6 km (13,500-15,100 ft) a.s.l. and drifted W and S. The explosions produced rumbling and degassing sounds, and shock waves were detected 10 km away. Lava flowed 150 m W towards the Taniluyá ravine and incandescent material rolled down the flanks. Geologic Summary. Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3,763-m-high Fuego and its twin volcano to the N, Acatenango. Construction of Meseta volcano continued until the late Pleistocene or early Holocene, after which growth of the modern Fuego volcano continued the southward migration of volcanism that began at Acatenango. Frequent vigorous historical eruptions have been recorded at Fuego since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows. The last major explosive eruption from Fuego took place in 1974, producing spectacular pyroclastic flows visible from Antigua. Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/ KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m KVERT reported that seismic activity at Karymsky increased above background levels during 13-17 November; possible explosions may have generated ash plumes to an altitude of 3.3 km (10,800 ft) a.s.l. Analysis of satellite imagery revealed a thermal anomaly in the crater during 13-16 November and an ash plume that drifted 28 km E on 15 November. Clouds prevented observations on the other days during 14-21 November. 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 HVO reported that during 19-25 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. Incandescence and active surface flows were seen on and at the base of the pali (fault scarp), and at the TEB vent. Earthquakes were variously located beneath and to the S of the caldera, and along the S-flank fault. During 20-21 November, tremor levels increased to four times the background level. The vent in Halema'uma'u crater continued to produce a predominantly white plume that drifted mainly SW and deposited small amounts of tephra. Night-time incandescence was occasionally seen at the base of the plume. The sulfur dioxide emission rate at the summit was 1,700 and 700 tonnes per day on 20 and 24 November, respectively; the 2003-2007 average rate 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/ PACAYA Guatemala 14.381°N, 90.601°W; summit elev. 2552 m On 20 November INSIVUMEH reported that fumarolic plumes from Pacaya's MacKenney cone drifted S at a low altitude. Ash occasionally entrained by strong winds drifted S. Multiple lava flows on the S, W, and SW flanks of the cone traveled 50-300 m during 20-21 and 25 November. Geologic Summary. Eruptions from Pacaya, one of Guatemala's most active volcanoes, are frequently visible from Guatemala City, the nation's capital. Pacaya is a complex volcano constructed on the southern rim of the 14 x 16 km Pleistocene Amatitlan caldera. A cluster of dacitic lava domes occupies the caldera floor. The Pacaya massif includes the Cerro Grande lava dome and a younger volcano to the SW. Collapse of Pacaya volcano about 1,100 years ago produced a debris-avalanche deposit that extends 25 km onto the Pacific coastal plain and left an arcuate somma rim inside which the modern Pacaya volcano (MacKenney cone) grew. During the past several decades, activity at Pacaya has consisted of frequent Strombolian eruptions with intermittent lava flow extrusion on the flanks of MacKenney cone, punctuated by occasional larger explosive eruptions. Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/ 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 19-25 November. The plumes occasionally contained slight amounts of ash. 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 Based on analysis of satellite imagery, the Darwin VAAC reported that during 12 and 19-25 November ash plumes from Rabaul caldera's Tavurvur cone rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted mainly N, NW, and W. 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. Source: 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 14-21 November. Based on interpretations of seismic data, ash plumes rose to an altitude of 6 km (19,700 ft) a.s.l. Fumarolic activity was visible on the web camera on 16 and 17 November. Analysis of satellite imagery revealed a daily thermal anomaly on the lava dome and a gas-and-steam plume that drifted about 100 km E on 14 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 22 and 24-25 November eruptions produced plumes to altitudes of 5.2-5.8 km (17,000-19,000 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 14-21 November the activity level at the Soufrière Hills lava dome remained low, and there was no evidence of lava extrusion. Rockfalls were detected by the seismic network. Visual observations were hindered by clouds and vigorous steaming from the dome. Weak ash venting possibly occurred briefly during the reporting period, including on 20 November. 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 information from JMA, the Tokyo VAAC reported an eruption from Suwanose-jima on 21 November. A plume rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted E. An explosion was reported on 25 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 that inclement weather mostly prevented observations of Tungurahua from 19-23 November; small fumarolic plumes were noted on 19 November. Roaring noises were reported on 20 November. On 22 November small lahars traveled down the Juive drainage (NNW flank), and on 25 November small lahars traveled down drainages on the W flank. 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. ==============================================================
