SI/USGS Weekly Volcanic Activity Report 15-21 July 2009
From: Sally Kuhn Sennert kuhns@xxxxxx
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SI/USGS Weekly Volcanic Activity Report
15-21 July 2009
Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx
URL: http://www.volcano.si.edu/reports/usgs/
New Activity/Unrest: | Sakura-jima, Kyushu | San Miguel, El Salvador
Ongoing Activity: | Bagana, Bougainville | Barren Island, Andaman Is | Batu Tara, Komba Island (Indonesia) | Chaitén, Southern Chile | Egon, Flores Island (Indonesia) | Ibu, Halmahera | Kilauea, Hawaii (USA) | Makian, Halmahera | Rabaul, New Britain | Sarychev Peak, Matua Island | Semeru, Eastern Java (Indonesia) | Shiveluch, Central Kamchatka (Russia) | Suwanose-jima, Ryukyu Islands (Japan)
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
SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m
Based on information from JMA, analyses of satellite imagery, and pilot observations, the Tokyo VAAC reported that during 15-21 July explosions from Sakura-jima's Showa crater occasionally produced plumes that rose to altitudes of 1.8-2.7 km (6,000-9,000 ft) a.s.l. Plumes were observed drifting SW, N, and NE. On 19 July, JMA raised the Alert Level from 2 to 3 (on a scale of 1-5). They noted increased frequency of explosive eruptions since late June, and shock waves that were detected on 18 and 19 July.
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.
Sources: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/indexe.html,
Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
SAN MIGUEL El Salvador 13.434°N, 88.269°W; summit elev. 2130 m
On 20 July, Servicio Nacional de Estudios Territoriales (SNET) reported that the amplitude of seismic events from San Miguel had decreased to normal or background levels. Access to areas within a 2-km-radius continued to be restricted.
Geologic Summary. The symmetrical cone of San Miguel volcano, one of the most active in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. A broad, deep crater that has been frequently modified by historical eruptions (recorded since the early 16th century) caps the truncated summit of the towering volcano, which is also known locally as Chaparrastique. Radial fissures on the flanks of the basaltic volcano have fed a series of fresh lava flows, including several erupted during the 17th-19th centuries that reached beyond the base of the volcano on the N, W, and SE sides. The SE-flank lava flows are the largest and form broad sparsely vegetated lava fields.
Source: Servicio Nacional de Estudios Territoriales (SNET) http://www.snet.gob.sv/
Ongoing Activity
BAGANA Bougainville 6.140°S, 155.195°E; summit elev. 1750 m
Based on analyses of satellite imagery, the Darwin VAAC reported that on 19 July an ash plume from Bagana rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted 100 km NW.
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
BARREN ISLAND Andaman Is 12.278°N, 93.858°E; summit elev. 354 m
Based on analysis of satellite imagery, the Darwin VAAC reported that during 19-20 July an ash plume from Barren Island rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted 45-65 km NE.
Geologic Summary. Barren Island, a possession of India in the Andaman Sea about 135 km NE of Port Blair in the Andaman Islands, is the only historically active volcano along the N-S-trending volcanic arc extending between Sumatra and Burma (Myanmar). The 354-m-high island is the emergent summit of volcano that rises from a depth of about 2,250 m. The small, uninhabited 3-km-wide island contains a roughly 2-km-wide caldera with walls 250-350 m high. The caldera, which is open to the sea on the W, was created during a major explosive eruption in the late Pleistocene that produced pyroclastic-flow and -surge deposits. The morphology of a fresh pyroclastic cone that was constructed in the center of the caldera has varied during the course of historical eruptions. Lava flows fill much of the caldera floor and have reached the sea along the western coast during historical eruptions.
Source: Darwin Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m
Based on analyses of satellite imagery, the Darwin VAAC reported that during 15-18 July ash plumes from Batu Tara rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted 20-55 km in multiple directions.
Geologic Summary. The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow.
Source: Darwin Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m
Based on web camera views from the S, SERNAGEOMIN reported that during 8-15 July gas-and-ash plumes rose 1.2 km from Chaitén's growing Domo Nuevo 1 and Domo Nuevo 2 lava-dome complex. Collapses originating from unstable slopes generated block-and-ash flows, particularly in the W area of the complex. The Alert Level remained at Red. Based on web camera views, analyses of satellite imagery, and a SIGMET notice, the Buenos Aires VAAC reported that during 16, 19, and 21 July ash plumes rose to altitudes of 1.8-2.4 km (6,000-8,000 ft) a.s.l. and drifted NNE, SE, and SSW. Thermal anomalies were detected in satellite imagery on 16 and 19 July.
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
EGON Flores Island (Indonesia) 8.67°S, 122.45°E; summit elev. 1703 m
CVGHM reported that the Alert Level for Egon was lowered to 1 (on a scale of 1-4) on 16 July due to the continued decrease in earthquake activity since 12 May. Small steam plumes were occasionally visible when the weather was clear.
Geologic Summary. Gunung Egon volcano sits astride the narrow waist of eastern Flores Island. The barren, sparsely vegetated summit region has a 350-m-wide, 200-m-deep crater that sometimes contains a lake. Other small crater lakes occur on the flanks of the 1,703-m-high volcano. A lava dome forms the southern 1,671-m-high summit. Reports of historical eruptive activity are inconclusive. A column of "smoke" was often observed above the summit during 1888-1891 and in 1892. Strong "smoke" emission in 1907 reported by Sapper (1917) was considered by the Catalog of Active Volcanoes of the World (Neumann van Padang, 1951) to be an historical eruption, but Kemmerling (1929) noted that this was likely confused with an eruption on the same date and time from Lewotobi Lakilaki volcano.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/
IBU Halmahera 1.488°N, 127.63°E; summit elev. 1325 m
CVGHM reported that white and gray plumes from Ibu rose 600 m above the crater rim prior to 11 July and 400 m above the crater afterwards. Ashfall was reported in nearby areas, within a 3-km-radius of Ibu. Based on information from the Gamsungi observation post and seismic data, CVGHM lowered the Alert Level on 16 July from 3 to 2 (on a scale of 1-4). Residents and tourists were not permitted within 2 km of the crater.
Geologic Summary. The truncated summit of Gunung Ibu stratovolcano along the NW coast of Halmahera Island has large nested summit craters. The inner crater, 1 km wide and 400 m deep, contained several small crater lakes through much of historical time. The outer crater, 1.2 km wide, is breached on the north side, creating a steep-walled valley. A large parasitic cone is located ENE of the summit. A smaller one to the WSW has fed a lava flow down the western flank. A group of maars is located below the northern and western flanks of the volcano. Only a few eruptions have been recorded from Ibu in historical time, the first a small explosive eruption from the summit crater in 1911. An eruption producing a lava dome that eventually covered much of the floor of the inner summit crater began in December 1998.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/
KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m
During 15-20 July, 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 at several locations on the pali, and on the TEB flow field. A structure in the abandoned Royal Gardens subdivision was destroyed on 16 July. Explosions from the Waikupanaha ocean entry were reported on 17 July. Lava was not seen entering the ocean on 21 July.
The vent in Halema'uma'u crater continued to produce a diffuse white plume that drifted mainly SW. No lava or incandescence from the crater had been seen since a "deflation-inflation" event on 4 July. Small amounts of ash-sized "rock dust" were retrieved from collection bins placed near the plume during the reporting period. The sulfur dioxide emission rate at the summit remained elevated; measurements were 400 and 1,100 tonnes per day on 17 and 20 July, 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/
MAKIAN Halmahera 0.32°N, 127.40°E; summit elev. 1357 m
CVGHM reported that on 16 July the Alert Level for Makian was lowered from 2 to 1 (on a scale of 1-4) because no visual changes or increased seismicity were noted. Residents and tourists were not permitted to climb Makian.
Geologic Summary. Makian volcano forms a 10-km-wide island near the southern end of a chain of volcanic islands off the W coast of Halmahera and has been the source of infrequent, but violent eruptions that have devastated villages on the island. The large 1.5-km-wide summit crater, containing a small lake on the NE side, gives the peak a flat-topped profile. Two prominent valleys extend to the coast from the summit crater on the N and E sides. Four parasitic cones are found on the western flanks. Eruption have been recorded since about 1550; major eruptions in 1646, 1760-61, 1861-62, 1890, and 1988 caused extensive damage and many fatalities.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/
RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m
RVO reported that during 10-21 July white and occasionally blue tinted plumes from Rabaul caldera's Tavurvur cone rose less than 1 km above the crater. Pale-gray ash accompanied the emissions on 13 and 15 July. Ashfall affected Rabaul town (3-5 km NW), Ratavul (20 km SSE), and Nonga (10 km NW). Incandescence was visible at night and roaring was heard during 14-18 July.
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: Rabaul Volcano Observatory (RVO)
SARYCHEV PEAK Matua Island 48.092°N, 153.20°E; summit elev. 1496 m
Based on analyses of satellite imagery, SVERT reported that gas-and-steam plumes from Sarychev Peak were seen on satellite imagery during 15, 18-19, and 21 July. Plumes drifted 30-50 km W and S. Cloud cover prevented observations during 16-17 and 20 July. Sarychev Peak does not have a seismic network.
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.
Source: Sakhalin Volcanic Eruption Response Team (SVERT) http://www.imgg.ru/rus/labs_vulcan_hazard.php
SEMERU Eastern Java (Indonesia) 8.108°S, 112.92°E; summit elev. 3676 m
CVGHM reported that on 15 March an eruption from Semeru produced a white-and-gray plume that rose 600 m above the crater. White plumes and ash eruptions gradually ceased and seismicity decreased. From 5 May until the end of June, fog prevented visual observations. On 16 July, the Alert Level was lowered to 2 (on a scale of 1-4).
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: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/
SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m
KVERT reported that during 10-17 July seismic activity from Shiveluch was above background levels. On 14 July, a gas-and-steam plume seen on a video camera rose to an altitude of 4 km (13,100 ft) a.s.l. Based on interpretations of seismic data, ash plumes possibly rose to an altitude of 6.5 km (21,300 ft) a.s.l. during 10, 13-14, and 16 July, and steam-and-gas plumes with some ash content were emitted during the reporting period. Analysis of satellite imagery revealed a daily thermal anomaly over the lava dome, and a steam plume that drifted 19 km SW on 13 July. The Level of Concern Color Code remained at Orange. Based on analyses of satellite imagery and information from KEMSD, the Tokyo VAAC reported that on 17 July an eruption produced a plume that rose to an altitude of 5.5 km (18,000 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. 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.
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
SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m
Based on a pilot observation, the Tokyo VAAC reported that on 15 July an ash plume from Suwanose-jima rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted NE. Eruptions reported by the JMA during 16-17 July produced plumes that rose to altitudes of 1.5-1.8 km (5,000-6,000 ft) a.s.l. and drifted NE and W.
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
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