SI/USGS Weekly Volcanic Activity Report 20-26 August 2008 Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Kasatochi, Andreanof Islands | Kirishima, Kyushu (Japan) | Soufrière Hills, Montserrat Ongoing Activity: | Batu Tara, Komba Island (Indonesia) | Bezymianny, Central Kamchatka (Russia) | Chaitén, Southern Chile | Chikurachki, Paramushir Island | Cleveland, Chuginadak Island | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Llaima, Central Chile | Okmok, Fox Islands | Pacaya, Guatemala | Rabaul, New Britain (SW Pacific) | Sakura-jima, Kyushu (Japan) | Santa María, Guatemala | Semeru, Eastern Java (Indonesia) | Shiveluch, Central Kamchatka (Russia) | 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 KASATOCHI Andreanof Islands 52.177°N, 175.508°W; summit elev. 314 m AVO reported that during 20-26 August seismic activity from Kasatochi was detected by stations on Great Sitkin, approximately 40 km W. Clouds prevented satellite image observations. Active fumaroles and hot pyroclastic flow deposits over much of the volcano were observed on 22 August by a visiting scientist. On 23 August, the smell of sulfur was reported in the town of Adak. The Volcano Alert Level remained at Watch and the Aviation Color Code at Orange. Geologic Summary. Located at the northern end of a shallow submarine ridge trending perpendicular to the Aleutian arc, Kasatochi is small 2.7 x 3.3 km wide island volcano with a dramatic 750-m-wide summit crater lake. The summit of Kasatochi reaches only 314 m above sea level, and the lake surface lies less than about 60 m above the sea. A lava dome is located on the NW flank at about 150 m elevation. The asymmetrical island is steeper on the northern side than the southern, and the volcano's crater lies north of the center of the island. Reports of activity from the heavily eroded Koniuji volcano to the east probably refer to eruptions from Kasatochi. A lava flow may have been emplaced during the first historical eruption in 1760. Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/ KIRISHIMA Kyushu (Japan) 31.931°N, 130.864°E; summit elev. 1700 m Based on reports from JMA, the Tokyo VAAC reported a possible eruption of Kirishima on 22 August. The altitude and direction of a possible resultant plume were not reported. Geologic Summary. Kirishima is a large group of more than 20 Quaternary volcanoes located north of Kagoshima Bay. The late-Pleistocene to Holocene volcano group consists of stratovolcanoes, pyroclastic cones, maars, and underlying shield volcanoes located over an area of 20 x 30 km. The larger stratovolcanoes are scattered throughout the field, with the centrally located, 1,700-m-high Karakuni-dake being the highest. Onami-ike and Mi-ike, the two largest maars, are located SW of Karakuni-dake and at its far eastern end, respectively. Holocene eruptions have been concentrated along an E-W line of vents from Mi-ike to Ohachi, and at Shinmoe-dake to the NE. Frequent small-to-moderate explosive eruptions have been recorded since the 8th century. Source: 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 15-22 August, evidence suggested that the W side of the Soufrière Hills lava dome continued to grow. Cloud cover prevented visual observations. Rockfalls and long-period seismicity increased. Most of the rockfalls occurred on the W side of the lava dome in a new channel that developed below Gages Wall. Ash plumes occasionally generated by the rockfalls were most noticeable on 16 and 17 August. On 19 August a pyroclastic flow descended the Tar River Valley. According to news reports, on 25 August a rainfall-induced pyroclastic flow occurred on the W flank, split into two parts, and caused ashfall and a strong scent of gases in areas N. The event enlarged and steepened the rockfall gully below Gages Wall. 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. Sources: Montserrat Volcano Observatory (MVO) http://www.mvo.ms/, Caribbean Net News http://www.caribbeannetnews.com/news-10080--22-22--.html Ongoing Activity BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m Scientists on a boat passing Batu Tara about 24 km to the N observed six distinct eruptions of ash plumes from the westernmost area of the summit crater during a 45-minute period on 25 August. The plumes rose to an estimated altitude of 1.1-1.5 km (3,600-5,000 ft) a.s.l. and drifted W. 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: Tristram Burley, personal communication BEZYMIANNY Central Kamchatka (Russia) 55.978°N, 160.587°E; summit elev. 2882 m KVERT reported that seismic activity at Bezymianny was slightly above background levels during 14 and 16-18 August and at background levels during 15 and 20-21 August. Analysis of satellite imagery revealed a thermal anomaly over the lava dome during 14-15 and 18-21 August. The thermal anomaly enlarged just before an explosion on 19 August. The explosion produced an ash plume that rose to an altitude of 9 km (29,500 ft) a.s.l. and drifted 1,200 km W. Staff at a seismic station about 50 km W reported ashfall and the smell of volcanic gas. The Level of Concern Color Code was lowered to Yellow. Geologic Summary. Prior to its noted 1955-56 eruption, Bezymianny volcano had been considered extinct. Three periods of intensified activity have occurred during the past 3,000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. That eruption, similar to the 1980 event at Mount St. Helens, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m Based on web camera views, pilot observations, and analysis of satellite imagery, the Buenos Aires VAAC reported that during 20-23 and 26 August ash plumes from Chaitén rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted SE, E, and NE. A thermal anomaly over the lava dome was detected on satellite imagery during 22-23 August. Geologic Summary. Chaitén is a small, glacier-free caldera with a Holocene lava dome located 10 km NE of the town of Chaitén on the Gulf of Corcovado. A pyroclastic-surge and pumice deposit considered to originate from the eruption that formed the elliptical 2.5 x 4 km wide summit caldera was dated at about 9400 years ago. A rhyolitic, 962-m-high obsidian lava dome occupies much of the caldera floor. Obsidian cobbles from this dome found in the Blanco River are the source of prehistorical artifacts from archaeological sites along the Pacific coast as far as 400 km away from the volcano to the north and south. The caldera is breached on the SW side by a river that drains to the bay of Chaitén, and the high point on its southern rim reaches 1122 m. Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html CHIKURACHKI Paramushir Island 50.325°N, 155.458°E; summit elev. 1816 m KVERT reported that clouds prevented satellite image views of Chikurachki during 15-22 August. The level of seismicity was unknown because Chikurachki lacks dedicated seismic instruments. The Level of Concern Color Code remained at Orange. Geologic Summary. Chikurachki, the highest volcano on Paramushir Island in the northern Kurils, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidzed scoria deposits covering the upper part of the young cone give it a distinctive red color. Lava flows from 1816-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. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php CLEVELAND Chuginadak Island 52.825°N, 169.944°W; summit elev. 1730 m AVO reported that cloud cover prevented satellite observations of Cleveland during 20-26 August, although a possible thermal anomaly was present on 24 August. On 25 August the Volcano Alert Level was lowered to Advisory and the Aviation Color Code to Yellow. Geologic Summary. 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 (AVO) http://www.avo.alaska.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 24 August an ash plume from Dukono rose to an altitude of 2.7 km (9,000 ft) a.s.l. and drifted NW. On 26 August, ash plumes rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted W and 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 FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m INSIVUMEH reported that on 20 August lahars descended several rivers to the S and SE of Fuego, carrying fine material as well as blocks up to 1 m in diameter. Strong currents in Río Cenizas and El Jute were noted. During 25-26 August, explosions produced ash plumes that rose to an altitude of 4.1 km (13,500 ft) a.s.l. and drifted SW. Fumarolic plumes rose to an altitude of 4 km (13,100 ft) a.s.l. and also drifted SW. A 300-m-long lava flow traveled W towards the Santa Teresa ravine. 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 was at typical levels during 14-15, 17, and 19-20 August. They also reported possible explosions during 14-15 and 17-20 August. Volcanic tremor was detected on 14 and 20 August. 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 20-26 August, lava flowed SE through a lava tube system from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and rootless shield complex to the Waikupanaha ocean entry. On 20 August, geologists observed bursting lava bubbles from an area E of Waikupanaha that threw molten fragments 10-20 m into the air. The sulfur dioxide emission rate at Pu'u 'O'o was 3,200 and 1,800 tonnes per day on 20 and 22 August, respectively; the average background rate is about 2,000 tonnes per day. Kilauea earthquakes were centered in various locations along the Koa'e fault system, S and W of the caldera, beneath the summit, along the S-flank faults, and along the E and SW rift zones. Beneath Halema'uma'u crater, more than 40 small earthquakes per day (background 40) also occurred but were too small to be located more precisely. About 100 earthquakes were detected on 26 August. The vent in Halema'uma'u crater continued to produce a predominantly white plume with minor ash content that drifted mainly SW. The plume was occasionally tinged brown. Weak night-time incandescence was intermittently seen at the base of the plume, and rock impacts and muted rushing sounds were heard in the vicinity of the crater. On 21 August, an earthquake was accompanied by a 400-m-high jet of mostly gas that rose vertically, then drifted SW. The jet also contained some rock dust and bits of volcanic glass. Several small ash ejections occurred on 25 August. The sulfur dioxide emission rate was 600-1,000 tonnes per day during 20-25 August. The pre-2008 background rate was 150-200 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/ LLAIMA Central Chile 38.692°S, 71.729°W; summit elev. 3125 m SERNAGEOMIN reported that steam plumes from the pyroclastic cones in Llaima's main crater were visible during periods of clear weather on 16 August. Steam plumes rose from the W flank where lava flows were active in February and July. On 17 August, sporadic gas-and-ash emissions were observed. Cloud cover prevented observations during 18-20 August. On 21 August, three explosions produced ash plumes that rose to an altitude of 3.6 km (11,800 ft) a.s.l. and drifted E. Gas and steam was emitted in between explosions; resultant plumes rose to an altitude of 3.4 km (11,200 ft) a.s.l. and drifted 9 km E. During an overflight, scientists observed steam-and-gas plumes being emitted from a small crater in the N sector of the main crater. A larger crater, about 100 m in diameter, in the central sector emitted ash. The ash plumes rose to an altitude of 3.4 km (11,200 ft) a.s.l. and drifted E. A thin layer of ash blanketed the E flank. Ash-and-gas plumes from the main crater drifted W on 22 August. On 23 August, observers reported that incandescent material was ejected less than 1 km above the crater. The next day, an ash plume drifted about 1.5 km SSE. Ash blanketed some areas of the flanks. The Volcanic Alert Level remained at Yellow. Geologic Summary. Llaima, one of Chile's largest and most active volcanoes, contains two main historically active craters, one at the summit and the other to the SE. The massive 3,125-m-high, glacier-covered stratovolcano has a volume of 400 cu km. A Holocene edifice built primarily of accumulated lava flows was constructed over an 8-km-wide caldera that formed about 13,200 years ago, following eruption of the 24 cu km Curacautín Ignimbrite. More than 40 scoria cones dot the volcano's flanks. Following the end of an explosive stage about 7,200 years ago, construction of the present edifice began, characterized by Strombolian, Hawaiian, and infrequent subplinian eruptions. Frequent moderate explosive eruptions with occasional lava flows have been recorded since the 17th century. Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/ OKMOK Fox Islands 53.43°N, 168.13°W; summit elev. 1073 m AVO reported that seismic activity at Okmok decreased on 19 August to near pre-eruption levels and remained low during 20-24 August. Occasional bursts of volcanic tremor were detected. Although satellite views were hindered due to cloud cover, a possible thermal anomaly in the crater was present on 21, 24, and 25 August. The Volcano Alert Level remained at Watch and the Aviation Color Code at Orange. Geologic Summary. The broad, basaltic Okmok shield volcano, which forms the NE end of Umnak Island, has a dramatically different profile than most other Aleutian volcanoes. The summit of the low, 35-km-wide volcano is cut by two 10-km-wide calderas formed during eruptions about 8,250 and 2,400 years ago that produced dacitic pyroclastic flows that reached the coast. Numerous satellitic cones and lava domes dot the flanks of the volcano down to the coast. Some of the post-caldera cones show evidence of wave-cut lake terraces; the more recent cones, some of which have been active historically, were formed after the caldera lake disappeared. Hot springs and fumaroles are found within the caldera and at Hot Springs Cone, 20 km to the SW. Historical eruptions have occurred since 1805 from cinder cones within the caldera. Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/ PACAYA Guatemala 14.381°N, 90.601°W; summit elev. 2552 m INSIVUMEH reported that during 21-26 August, fumarolic plumes from Pacaya's MacKenney cone rose to an altitude of 3.2 km (10,500 ft) a.s.l. and drifted W and SW. Incandescence from the crater was occasionally seen at night. Lava flows on the SW flank branched and traveled a maximum of 300 m; lava continued to fill in the area between MacKenney cone and Cerro Chino crater to the N. Avalanches occurred from the lava-flow fronts on 26 August. 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/ RABAUL New Britain (SW Pacific) 4.271°S, 152.203°E; summit elev. 688 m RVO reported that ash plumes from Rabaul caldera's Tavurvur cone continued to be emitted during 18-22 August, although less so than during 16-18 August. Some prolonged ash-free intervals were immediately followed by explosions that produced ash plumes. The plumes drifted NW and caused ashfall in areas downwind. Occasionally incandescence at the summit was observed and roaring noises were heard. Explosions also ejected incandescent lava fragments. Based on analysis of satellite imagery, the Darwin VAAC reported that on 23 August ash plumes rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 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: Ima Itikarai, Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html SAKURA-JIMA Kyushu (Japan) 31.585°N, 130.657°E; summit elev. 1117 m Based on information from JMA, the Tokyo VAAC reported an explosion from Sakura-jima on 23 August. The altitude and direction of a possible resultant plume were not reported. Geologic Summary. Sakura-jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow was associated with the formation of the 17 x 23-km-wide Aira caldera about 22,000 years ago. The construction of Sakura-jima began about 13,000 years ago and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kita-dake summit cone ended about 4,850 years ago, after which eruptions took place at Minami-dake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76. Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m INSIVUMEH reported that during 21-26 August explosions from Caliente, a unit of Santa María's Santiaguito lava dome complex, produced ash plumes that rose to altitudes of 2.8-3.3 km (9,200-10,800 ft) a.s.l. and drifted S, SW, and W. Constant degassing was noted. Geologic Summary. Symmetrical, forest-covered Santa María volcano is one of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1-km-wide crater, which formed during a catastrophic eruption in 1902 and extends from just below the summit to the lower flank. The renowned Plinian eruption of 1902 followed a long repose period and devastated much of SW Guatemala. The large dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, accompanied by almost continuous minor explosions and periodic lava extrusion, larger explosions, pyroclastic flows, and lahars. Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/ SEMERU Eastern Java (Indonesia) 8.108°S, 112.92°E; summit elev. 3676 m Based on pilot reports and observations of satellite imagery, the Darwin VAAC reported that during 21-22 August ash plumes from Semeru rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted W. Geologic Summary. Semeru is the highest volcano on Java and one of its most active. The symmetrical stratovolcano rises abruptly to 3,676 m above coastal plains to the S and lies at the southern end of a volcanic massif extending N to the Tengger caldera. Semeru has been in almost continuous eruption since 1967. Frequent small-to-moderate Vulcanian eruptions have accompanied intermittent lava dome extrusion, and periodic pyroclastic flows and lahars have damaged villages below the volcano. A major secondary lahar on 14 May 1981 caused more than 250 deaths and damaged 16 villages. 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 slightly above background levels during 15-22 August. Analysis of satellite imagery revealed a thermal anomaly on the lava dome on 15, 18, and 21 August. The Level of Concern Color Code remained at Orange. 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. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m Based on reports from JMA, the Tokyo VAAC reported explosions from Suwanose-jima during 24-26 August. Resultant plumes rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. during 25-26 August. 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 on 19 August fumarolic plumes from Tungurahua rose 20 m above the NE crater and on 20 August, steam-and-ash plumes rose about 50 m above the crater. On 21 August, intense rains prompted the Tungurahua Observatory (OVT) to issue a warning of potential lahars in the Vascún river. A natural dam in the river was previously identified as potentially hazardous. On 23 August, a person in El Salado detected vibrations. The dam ruptured and material descended the Vascún river to the N at speeds of 10-15 m/s, destroying a house, damaging and demolishing bridges, and destroying multiple public swimming pools in the Baños area. Two people were injured and two people were missing. 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. ==============================================================
