************************************************************* SI/USGS Weekly Volcanic Activity Report 10-16 June 2009 ************************************************************* Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Rinjani, Lombok Island (Indonesia) | Sangay, Ecuador | Sarychev Peak, Matua Island Ongoing Activity: | Batu Tara, Komba Island (Indonesia) | Chaitén, Southern Chile | Dukono, Halmahera | Ebeko, Paramushir Island | Galeras, Colombia | Kilauea, Hawaii (USA) | Kliuchevskoi, Central Kamchatka (Russia) | Popocatépetl, México | Rabaul, New Britain | Redoubt, Southwestern Alaska | Sakura-jima, Kyushu | Shiveluch, Central Kamchatka (Russia) | Suwanose-jima, Ryukyu Islands (Japan) | Tungurahua, Ecuador | Turrialba, Costa Rica | Ubinas, Perú 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 RINJANI Lombok Island (Indonesia) 8.42°S, 116.47°E; summit elev. 3726 m Base on analysis of satellite imagery, the Darwin VAAC reported that during 11-12 and 16 June ash plumes from Rinjani rose to an altitude of 4 km (13,000 ft) a.s.l. and drifted 15-55 km W and WSW. 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. Map Source: Darwin Volcanic Ash Advisory Center (VAAC) Rinjani Information from the Global Volcanism Program SANGAY Ecuador 2.002°S, 78.341°W; summit elev. 5230 m Based on analysis of satellite imagery, the Washington VAAC reported that on 15 June possible small ash plumes from Sangay drifted WNW. A thermal anomaly was detected. 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. Map Source: Washington Volcanic Ash Advisory Center (VAAC) Sangay Information from the Global Volcanism Program SARYCHEV PEAK Matua Island 48.092°N, 153.20°E; summit elev. 1496 m Based on analysis of satellite imagery, SVERT reported that on 11 June a thermal anomaly from Sarychev Peak and a possible diffuse ash plume were detected. Seismicity was at background levels. The next day, a large thermal anomaly was present and ash emissions were were seen on satellite imagery. On 13 June, ash plumes rose to an altitude of 7.5 km (24,600 ft) a.s.l. and drifted 200 km SW and 105 km SE. On 14 June, a large eruption produced an ash plume that rose to an altitude of 12 km (39,400 ft) a.s.l. A large explosion the next day sent an ash plume to an altitude of 8 km (26,200 ft) a.s.l. Sarychev Peak is not monitored with ground-based instruments. According to news articles, some airlines have re-routed, canceled, or delayed flights. Geologic Summary. Sarychev Peak, one of the most active volcanoes of the Kuril Islands, occupies the NW end of Matua Island in the central Kuriles. The andesitic central cone was constructed within a 3-3.5 km wide caldera, whose rim is exposed only on the SW side. A dramatic 250-m-wide, very steep-walled crater with a jagged rim caps the volcano. The substantially higher SE rim forms the 1496 m high point of the island. Fresh-looking lava flows descend all sides of Sarychev Peak and often form capes along the coast. Much of the lower-angle outer flanks of the volcano are overlain by pyroclastic-flow deposits. Eruptions have been recorded since the 1760's and include both quiet lava effusion and violent explosions. The largest historical eruption of Sarychev Peak in 1946 produced pyroclastic flows that reached the sea. Map Sources: Sakhalin Volcanic Eruption Response Team (SVERT), The Province, Canada.com Sarychev Peak Information from the Global Volcanism Program 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 10-16 June ash plumes from Batu Tara rose to altitudes of 1.5-2.4 km (5,000-8,000 ft) a.s.l. and drifted 25-185 km SW, NW, N, and NE. 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. Map Source: Darwin Volcanic Ash Advisory Center (VAAC) Batu Tara Information from the Global Volcanism Program CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m Based on web camera views, analysis of satellite imagery, and a SIGMET notice, the Buenos Aires VAAC reported that on 11 and 14 June ash plumes from Chaitén's Domo Nuevo 1 and Domo Nuevo 2 lava-dome complex rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted NE and SE. A thermal anomaly was also seen in satellite imagery on 11 June. 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. Map Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) Chaitén Information from the Global Volcanism Program DUKONO Halmahera 1.68°N, 127.88°E; summit elev. 1335 m Based on analysis of satellite imagery, the Darwin VAAC reported that on 16 June an ash plume from Dukono rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted 40 km NE. 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. Map Source: Darwin Volcanic Ash Advisory Center (VAAC) Dukono Information from the Global Volcanism Program EBEKO Paramushir Island 50.68°N, 156.02°E; summit elev. 1156 m KVERT reported that during 9-10 June gas-and-steam plumes from Ebeko rose to an altitude of 2.7 km (8,900 ft) a.s.l. The Level of Concern Color Code remained at Yellow. Based on analysis of satellite imagery and information from Yelizovo Airport, the Tokyo VAAC reported that on 13 June an ash plume rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted SW. Geologic Summary. The flat-topped summit of the central cone of Ebeko volcano, one of the most active in the Kuril Islands, occupies the northern end of Paramushir Island. Three summit craters located along a SSW-NNE line form Ebeko volcano proper, at the northern end of a complex of five volcanic cones. The eastern part of the southern crater of Ebeko contains strong solfataras and a large boiling spring. The central crater of Ebeko is filled by a lake about 20 m deep whose shores are lined with steaming solfataras; the northern crater lies across a narrow, low barrier from the central crater and contains a small, cold crescentic lake. Historical activity, recorded since the late-18th century, has been restricted to small-to-moderate explosive eruptions from the summit craters. Intense fumarolic activity occurs in the summit craters of Ebeko, on the outer flanks of the cone, and in lateral explosion craters. Map Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), Tokyo Volcanic Ash Advisory Center (VAAC) Ebeko Information from the Global Volcanism Program GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m On 10 June, INGEOMINAS reported that the Alert Level for Galeras was lowered to II (Orange; "probable eruption in term of days or weeks"). Pulsating steam plumes rose from the crater and drifted NW. Seismicity remained low. 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. Map Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) Galeras Information from the Global Volcanism Program KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m During 10-16 June, HVO reported that lava flowed SE from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex through a lava tube system, reaching the Waikupanaha and Kupapa'u ocean entries. Thermal anomalies detected in satellite images and visual observations revealed active surface flows on the pali and on the TEB flow field. Explosions from the Waikupanaha ocean entry were reported on 13 June. The vent in Halema'uma'u crater continued to produce a predominantly white plume that drifted mainly SW. Small amounts of tephra, including Pele's hair and fresh spatter, were retrieved from collection bins placed near the plume during the reporting period. A molten lava pool near the base of the cavity, about 100 m below the floor of the crater, produced bright incandescence. The Halema'uma'u Overlook Vent webcam that has a view into the vent cavity showed a draining event from the actively bubbling lava pond on the evening of 12 June. Sounds resembling rushing gas and rockfalls were occasionally heard in the vicinity of the crater. The sulfur dioxide emission rate at the summit remained elevated; measurements were 1,100 and 1,000 tonnes per day on 11 and 12 June, 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. Map Source: US Geological Survey Hawaiian Volcano Observatory (HVO) Kilauea Information from the Global Volcanism Program KLIUCHEVSKOI Central Kamchatka (Russia) 56.057°N, 160.638°E; summit elev. 4835 m On 11 June, KVERT reported that seismic activity from Kliuchevskoi had remained at background levels since 12 May. Weak intermittent volcanic tremor and fumarolic activity continued to be detected. The Level of Concern Color was lowered to Green. 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. Map Source: Kamchatkan Volcanic Eruption Response Team (KVERT) Kliuchevskoi Information from the Global Volcanism Program POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m CENAPRED reported that during 10-16 June emissions of steam and gas from Popocatépetl sometimes 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. Map Source: Centro Nacional de Prevencion de Desastres (CENAPRED) Popocatépetl Information from the Global Volcanism Program RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m RVO reported that during 7-11 June white and occasionally blue plumes from Rabaul caldera's Tavurvur cone rose 1.5 km above the crater. Incandescence from the summit crater was seen at night. Based on analysis of satellite imagery, the Darwin VAAC reported that during 11-12 and 16 June ash plumes rose to altitudes of 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted 25-45 km SE, E, and NE. 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. Map Sources: Ima Itikarai, Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC) Rabaul Information from the Global Volcanism Program REDOUBT Southwestern Alaska 60.485°N, 152.742°W; summit elev. 3108 m AVO reported that during 10-15 June seismicity from Redoubt remained low, but above background levels; small discrete earthquakes in the summit region associated with dome growth and instability were recorded. Clear web camera views on 10, 11, and 16 June showed steaming from the summit region. On 12 June, the lava dome was an estimated 1 km long, 460 m wide, and 200 m high. The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange. 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. Map Source: Alaska Volcano Observatory (AVO) Redoubt Information from the Global Volcanism Program SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m Based on a pilot observation, the Tokyo VAAC reported that on 12 June an ash plume from Sakura-jima rose to an altitude of 1.8 km (6,000 ft) a.s.l. The JMA reported that during 14-16 June eruptions produced plumes that rose to altitudes of 2.4-2.7 km (8,000-9,000 ft) a.s.l. Plumes drifted SE and E on 14 and 15 June. 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. Map Source: Tokyo Volcanic Ash Advisory Center (VAAC) Sakura-jima Information from the Global Volcanism Program SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m KVERT reported that during 5-11 June seismic activity from Shiveluch was above background levels. Based on interpretations of seismic data, diffuse ash plumes were emitted during the reporting period; ash plumes possibly rose to altitudes of 4.8-7.7 km (16,000-25,300 ft) a.s.l. during 6 and 10-11 June. Video camera images showed steam-and-gas emissions. Analysis of satellite imagery revealed a daily thermal anomaly over the lava dome, and ash plumes that drifted 90 km S on 6 and 7 June. The Level of Concern Color Code remained at Orange. Based on analysis of satellite imagery and information from KEMSD, the Tokyo VAAC reported that during 11-12 and 14-15 June eruptions produced plumes that rose to altitudes of 6.1-7.9 km (20,000-26,000 ft) a.s.l. A possible eruption was seen on satellite imagery on 13 June. 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. Map Sources: Kamchatkan Volcanic Eruption Response Team (KVERT), Tokyo Volcanic Ash Advisory Center (VAAC) Shiveluch Information from the Global Volcanism Program 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 explosion from Suwanose-jima on 16 June. Details of a possible resultant ash plume were not reported. 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. Map Source: Tokyo Volcanic Ash Advisory Center (VAAC) Suwanose-jima Information from the Global Volcanism Program TUNGURAHUA Ecuador 1.467°S, 78.442°W; summit elev. 5023 m The IG reported that during 10-15 June tremor and explosions from Tungurahua were detected by the seismic network. Ash plumes rose to a maximum altitude of 7 km (23,000 ft) a.s.l. during 10-11 and 14 June; cloud cover frequently prevented observations during the reporting period. Ashfall was reported almost daily, mostly to the W. Some explosions were accompanied by "cannon shot" sounds or sounds resembling blocks rolling down the flanks. Windows occasionally vibrated. 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. Map Source: Instituto Geofísico-Escuela Politécnica Nacional (IG) Tungurahua Information from the Global Volcanism Program TURRIALBA Costa Rica 10.025°N, 83.767°W; summit elev. 3340 m On 14 June, OVSICORI-UNA reported that fumarolic activity from Turrialba had been observed all around the upper flanks of the active W crater. During the previous two months, the fumarolic activity was accompanied by widening of radial cracks (1.5 cm on average), 1-2 km tall gas-and-vapor plumes, and one sustained discrete seismic swarm. Temperatures of fumarolic vents in the lower parts of the crater were between 120 and 160 degrees Celsius. The temperature of summit cracks was 94 degrees Celsius. Dairy pastures and forests had been burned as far away as 3.5 km NW and W. 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. Map Source: Observatorio Vulcanológico y Sismológico de Costa Rica-Universidad Nacional (OVSICORI-UNA) Turrialba Information from the Global Volcanism Program UBINAS Perú 16.355°S, 70.903°W; summit elev. 5672 m Based on SIGMET notices and analysis of satellite imagery, the Buenos Aires VAAC reported that during 11 and 13-15 June eruptions from Ubinas produced ash plumes that rose to altitudes of 5.5-7.9 km (18,000-26,000 ft) a.s.l. Plumes drifted NE, E, and SE. Ash was not identified on satellite imagery on 13 June. Geologic Summary. A small, 1.2-km-wide caldera that cuts the top of Ubinas, Peru's most active volcano, gives it a truncated appearance. Ubinas is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Peru. The upper slopes of the stratovolcano, composed primarily of Pleistocene andesitic lava flows, steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas extend 10 km from the volcano. Widespread Plinian pumice-fall deposits from Ubinas include some of Holocene age. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor explosive eruptions. Map Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) Ubinas Information from the Global Volcanism Program +++++++++++++++++++++++++++++++++++++ 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. ==============================================================
