************************************************************ GVP/USGS Weekly Volcanic Activity Report 15-21 August 2007 http://www.volcano.si.edu/reports/usgs/ ************************************************************ New Activity/Unrest: | Chikurachki, Russia | Karangetang, Indonesia | Kilauea, USA | Manda Hararo, Ethiopia | Pavlof, USA Ongoing Activity: | Cleveland, USA | Fuego, Guatemala | Karymsky, Russia | Kliuchevskoi, Russia | Manam, Papua New Guinea | Rabaul, Papua New Guinea | Sangay, Ecuador | Shiveluch, Russia | Soufrière Hills, Montserrat | St. Helens, USA | Tungurahua, Ecuador New Activity/Unrest CHIKURACHKI Kuril Islands, Russia 50.325°N, 155.458°E; summit elev. 1,816 m Based on observations of satellite imagery, an ash plume from Chikurachki drifted about 120 km to the SE on 19 August. KVERT raised the Level of Concern Color Code from Green to Orange <http://www.avo.alaska.edu/color_codes.php>. The Tokyo VAAC reported that ash plumes rose to altitudes of 4.3-5.2 km (14,000-17,000 ft) a.s.l. during 20-21 August, based on observations of satellite imagery and information from KVERT. Geologic Summary. Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized scoria deposits covering the upper part of the young cone give it a distinctive red color. Lava flows from 1,816-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The more erosionally modified Tatarinov group of six volcanic centers is located immediately to the S of Chikurachki. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html Chikurachki Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0900-036= KARANGETANG [Api Siau] Siau Island, Indonesia 2.47°N, 125.29°E; summit elev. 1,784 m The Alert Status of Karangetang was raised on 18 August from 3 to 4 (on a scale of 1-4) due to increased eruptive activity, based on visual observation and increased seismicity. According to news articles, lava flowed about 1 km down the S slope and "booming" noises were heard. Thick ashfall covered villages, farms, and trees on the slopes. Geologic Summary. Karangetang (also known as Api Siau) lies at the northern end of the island of Siau, N of Sulawesi. The 1,784-m-high stratovolcano contains five summit craters along a N-S line. One of Indonesia's most active volcanoes, Karangetang has had more than 40 recorded eruptions since 1675. Twentieth-century eruptions have included frequent explosions, sometimes accompanied by pyroclastic flows and lahars. Sources: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/, Jakarta Post http://www.thejakartapost.com/detailheadlines.asp?fileid=20070821.A06&irec=5, Reuters http://news.yahoo.com/s/nm/20070820/wl_nm/indonesia_volcano_dc_2, Agence France-Presse http://news.yahoo.com/s/afp/20070820/sc_afp/indonesiavolcano_070820033601 Karangetang Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0607-02= KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m HVO reported that fissure segment D from Kilauea's 21 July fissure eruption continued to feed an advancing 'a'a lava flow during 15-21 August. Aerial observations on 17 August revealed that the first 'a'a flow had advanced 24 m since 13 August but was inactive. The second 'a'a channel had advanced 2.3 km along the N side of the first flow. Smoke from burning vegetation was visible near the flow front. On 18 August, a new and widening crack was seen on the rim of Pu'u 'O'o crater. A few small earthquakes were located beneath the summit, Halema'uma'u crater, and the S flank. On 14 August, approximately 17.8 hectares (44 acres) of the East Lae'apuki bench collapsed, possibly due to a M 5.4 earthquake, high surf from hurricane Flossie, or a combination of both. 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 by lava flows less than about 1,100 years old; 70% of the volcano's surface is younger than 600 years. The latest Kilauea eruption began in January 1983 along the E rift zone. This long-term ongoing eruption from Pu'u 'O'o-Kupaianaha has produced lava flows that have traveled 11-12 km from the vents to the sea, paving broad areas on the S flank of Kilauea and adding new land beyond the former coastline. Source: US Geological Survey Hawaiian Volcano Observatory http://volcano.wr.usgs.gov/hvostatus.php Kilauea information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01- MANDA HARARO Ethiopia 12.17°N, 40.82°E; summit elev. 600+ m A large sulfur dioxide plume and several thermal anomalies from Manda Hararo were detected in satellite imagery on 13 August. On 16 August, a field team conducted aerial and ground observations of a locality known as Karbahi, a graben area with numerous active faults, fissures, and basalt flows, NW of the center of Manda Hararo. Observations revealed active volcanism, including isolated areas of intense gas emission and visible sulfur deposits. Basaltic lava flowed from long fissures, predominantly to the W of the graben floor. Each fissure was covered by a continuous row of small and closely spaced spatter and scoria cones 2-10 m high. Spatter and scoria deposits ranged in size from coarse lapilli to bombs. Incandescence and occasionally small flames were emitted from the tops of some of the cones. Observed 'a'a and pahoehoe flows traveled a few hundred meters from the vents. The overall thickness of the flows varied but reached several meters in places. Lava channels and lava tubes were abundant. Fault scarps with fresh breaks and rockfalls were noted. The area affected by tectonic and volcanic activity was an estimated 5-7 km long and 1 km wide. According to eye-witness accounts, a cracking sound was heard and a tremor was felt on 12 August. On 13 August, "fire" was seen that lit up a large area. "Fire and smoke" continued with variable intensity until 16 August. No damage to life or property was reported. Geologic Summary. The southernmost axial range of western Afar, the Manda Hararo complex is located in the Kalo plain, SSE of Dabbahu volcano. The massive complex is 105 km long and 20-30 km wide, and represents an uplifted segment of a mid-ocean ridge spreading center. A small basaltic shield volcano is located at the northern end of the complex, south of which is an area of abundant fissure-fed lava flows. Two basaltic shield volcanoes, the largest of which is Unda Hararo, occupy the center of the complex. The dominant part of the complex lies to the south, where the Gumatmali-Gablaytu fissure system is located. Voluminous fluid lava flows issued from these NNW-trending fissures, and solidified lava lakes occupy two large craters. Lava flows from the Gablaytu and Manda shield volcanoes overlie 8000-year-old sediments. Hot springs and fumaroles occur around Daorre lake. Sources: Simon Carn, University of Maryland, Gezahegn Yirgu, Atalay Ayele, Shimeles Fisseha, Tadiwos Chernet and Ato Kifle Damtew, Addis Ababa University, Ethiopia Manda Hararo information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0201-115 PAVLOF Alaska, USA 55.42°N, 161.887°W; summit elev. 2,519 m AVO raised the Volcanic Alert Level to Advisory and the Aviation Color Code to Yellow for Pavlof on 14 August due to an abrupt increase in seismicity. During 14-15 August, a strong thermal anomaly was detected in the crater and prompted AVO to again raise the Volcanic Alert Level/ Aviation Color Code, to Watch/Orange <http://www.avo.alaska.edu/color_codes.php>. According to eye witnesses aboard a ship on 15 August, incandescent blocks rolled down the ESE flank and lava-fountaining occurred on the SE flank. The presence of lava was confirmed using satellite imagery. Pilots reported that the flanks were covered with ash and that an ash plume rose to an altitude of 2.6 km (8,400 ft) a.s.l. and drifted SW. On 16 August, residents of Cold Bay, about 60 km SW, and of Sand Point, about 97 km ESE, saw incandescence at the summit. A strong thermal anomaly was present at the summit on satellite imagery. Seismicity increased in intensity and possibly indicated a lahar on the SE flank. During 17-20 August, seismicity continued at high levels. Explosions were recorded and seismic signals possibly indicated flow events such as lahars. A strong thermal anomaly continued to be present at the summit. Aerial and ground observations revealed a vigorous eruption of lava during 18-20 August. Members of an AVO field party saw a lahar on the SE flank on 20 August. Geologic Summary. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavolf, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing strombolian to vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption of Pavlof took place in 1911, at the end of a 5-year-long eruptive episode; a fissure opened on the northern flank of the volcano, ejecting large blocks and issuing lava flows. Source: Alaska Volcano Observatory http://www.avo.alaska.edu/ Pavlof information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1102-03- Ongoing Activity CLEVELAND Aleutian Islands, USA 52.82°N, 169.95°W; summit elev. 1,730 m Clouds obscured satellite and web camera views of Cleveland volcano during 15-20 August. A clear view of the crater on 20 August revealed a thermal anomaly at the summit. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch <http://www.avo.alaska.edu/color_codes.php>. Geologic Summary. The symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited dumbbell-shaped Chuginadak Island in the east-central Aleutians. The 1,730-m-high stratovolcano is the highest of the Islands of Four Mountains group and is one of the most active in the Aleutians. Numerous large lava flows descend its flanks. It is possible that some 18th to 19th century eruptions attributed to Carlisle (a volcano located across the Carlisle Pass Strait to the NW) should be ascribed to Cleveland. In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mt. Cleveland have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks. Source: Alaska Volcano Observatory http://www.avo.alaska.edu/ Cleveland Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1101-24- FUEGO Guatemala 14.47°N, 90.88°W; summit elev. 3,763 m Based on a Guatemala City surface report, the Washington VAAC reported activity at Fuego. A hotspot was visible on satellite imagery. 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: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html Fuego Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-09= KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m Seismic activity at Karymsky was above background levels during 10-17 August, with 350-600 shallow earthquakes occurring daily. Based on seismic interpretation, ash plumes may have risen to an altitude of 3 km (9,800 ft) a.s.l. The Level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. 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/updates.shtml Karymsky Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-13= KLIUCHEVSKOI Kamchatka Peninsula, Russia 56.06°N, 160.64°E; summit elev. 4,835 m On 17 August, KVERT reported that seismic activity at Kliuchevskoi was at background levels during the past five weeks, and ash plumes had not been noted for the last four weeks. Satellite imagery showed a thermal anomaly on 11 August. The Level of Concern Color Code was lowered from Yellow to Green <http://www.avo.alaska.edu/color_codes.php>. 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 have occurred during the past 3,000 years, mostly on the NE and SE flanks of the conical volcano between 500 m and 3,600 m elevation. 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 eruptions from flank craters. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml Kliuchevskoi Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-26= MANAM offshore New Guinea, Papua New Guinea 4.10°S, 145.06°E; summit elev. 1,807 m Based on satellite image observations and information from RVO, the Darwin VAAC reported that an eruption plume from Manam rose to an altitude of 3 km (10,000 ft) a.s.l. on 10 August and drifted W. On 21 August, an ash plume again rose to an altitude of 3 km (10,000 ft) a.s.l. as indicated by observations of satellite imagery. The plume drifted SW. Geologic Summary. The 10-km-wide island of Manam is one of Papua New Guinea's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1,807-m-high 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. Five satellitic centers are located near the island's shoreline. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during the past century into the SE avalanche valley. Frequent historical eruptions have been recorded since 1616. Source: Darwin Volcanic Ash Advisory Centre http://www.bom.gov.au/products/IDD41300.shtml Manam Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0501-02= RABAUL New Britain Island, Papua New Guinea 4.271°S, 152.203°E; summit elev. 688 m RVO reported that ash plumes from Rabaul caldera's Tavurvur cone rose to an altitude of 1.1 km (3,600 ft) a.s.l. on 15 August and drifted NNW. The ash emissions were accompanied by roaring noises. Ashfall was reported in Rabaul Town and surrounding areas. White vapor plumes noted during 14-20 August were occasionally accompanied by blue vapor plumes. Vapor plumes rose to an altitude of 1.7 km (5,600 ft) a.s.l. on 20 August and drifted WNW. 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: Herman Patia, Rabaul Volcano Observatory Rabaul Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-14= SANGAY Ecuador 2.03°S, 78.34°W; summit elev. 5,188 m Based on pilot observations, the Washington VAAC reported that an ash plume from Sangay drifted SSE on 19 August. Observations using satellite imagery were inhibited due to cloud cover. 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 Sangay Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-09= SHIVELUCH Kamchatka Peninsula, Russia 56.653°N, 161.360°E; summit elev. 3,283 m KVERT reported that seismic activity at Shiveluch was slightly above background levels during 10-17 August. Based on seismic interpretation, avalanches and ash plumes that rose to an altitude of 10 km (32,800 ft) a.s.l. occurred during the reporting period. Growth of the E part of the lava dome, summit incandescence, and incandescent avalanches were visible from the town of Klyuchi, about 50 km SW, during 11-12 August. A diffuse ash plume was visible on satellite imagery drifting SE on 11 August. On 14 August, two avalanches were accompanied by ash plumes that rose to an altitude of 4.5 km (14,800 ft) a.s.l. and drifted NW. Observations of satellite imagery revealed that a thermal anomaly was present in the crater during 10-17 August. The Level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. Based on information reported from KEMSD, the Tokyo VAAC reported that an eruption plume rose to 5.2 km (17,000 ft) a.s.l. on 21 August. Ash was not identified on satellite imagery. 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 horseshoe-shaped 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/updates.shtml, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html Shiveluch Information from the Global Volcanism Program http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1000-27= SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m MVO reported that during 13-21 August the lava dome at Soufrière Hills changed very little, based on visual observations. Seismic activity was very low and low-level rockfall activity continued. The Alert Level remained elevated at 4 (on a scale of 0-5). 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 east, was formed during an eruption about 4000 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 http://www.mvo.ms/ Soufrière Hills Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1600-05= ST. HELENS Washington, USA 46.20°N, 122.18°W; summit elev. 2,549 m Data from deformation-monitoring instruments indicated that during 15-21 August lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels, punctuated by M 1.5-2.5, and occasionally larger, earthquakes. In some instances, clouds inhibited visual observations. Geologic Summary. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago, and has been the most active volcano in the Cascade Range during the Holocene. The modern edifice was constructed during the last 2,200 years, when the volcano produced basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the N flank, and were witnessed by early settlers. Source: US Geological Survey Cascades Volcano Observatory http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity/framework.html St. Helens Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05- TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m Base on seismic interpretation, IG reported explosions and ash emissions from Tungurahua during 15-21 August. During 17-18 August, roaring and "cannon shot" noises were reported and ashfall occurred in areas to the W and SW. On 19 August, "cannon shot" noises were again reported and a gas-and-ash plume rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted W. Explosions on 20 and 21 August rattled windows at the Tungurahua Observatory (OVT) in Guadalupe, 11 km N, and in houses in areas to the W. Ashfall was reported in areas to the SW on 21 August. Inclement weather inhibited visual observations on other days. 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 been restricted to 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 Poltécnica Nacional http://www.igepn.edu.ec/ Tungurahua Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08= +++++++++++++++++++++++++++++++++++++ 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. ==============================================================
