*********************************************************** SI/USGS Weekly Volcanic Activity Report 1-7 April 2009 *********************************************************** Sally Kuhn Sennert - Weekly Report Editor kuhns@xxxxxx URL: http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Ebeko, Paramushir Island | Krakatau, Indonesia | Llaima, Central Chile | Nyamuragira, Democratic Republic of Congo | Nyiragongo, Democratic Republic of Congo | Pacaya, Guatemala | Redoubt, Southwestern Alaska Ongoing Activity: | Asama, Honshu | Batu Tara, Komba Island (Indonesia) | Galeras, Colombia | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Koryaksky, Eastern Kamchatka | Popocatépetl, México | Rabaul, New Britain | Sakura-jima, Kyushu | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat | Suwanose-jima, Ryukyu Islands (Japan) | Tungurahua, Ecuador The Weekly Volcanic Activity Report is a cooperative project between the Smithsonian's Global Volcanism Program and the US Geological Survey's Volcano Hazards Program. Updated by 2300 UTC every Wednesday, notices of volcanic activity posted on these pages are preliminary and subject to change as events are studied in more detail. This is not a comprehensive list of all of Earth's volcanoes erupting during the week, but rather a summary of activity at volcanoes that meet criteria discussed in detail in the "Criteria and Disclaimers" section. Carefully reviewed, detailed reports on various volcanoes are published monthly in the Bulletin of the Global Volcanism Network. Note: Many news agencies do not archive the articles they post on the Internet, and therefore the links to some sources may not be active. To obtain information about the cited articles that are no longer available on the Internet contact the source. New Activity/Unrest EBEKO Paramushir Island 50.68°N, 156.02°E; summit elev. 1156 m On 3 April, KVERT reported that the Level of Concern Color Code for Ebeko was raised to Yellow. Observers from Severo-Kurilsk, about 7 km E, reported increased activity; ash-and-gas plumes rose to an altitude of 3.2 km (10,500 ft) a.s.l. and drifted about 20 km NW and E. Ashfall was reported in Severo-Kurilsk on 13, 29, and 31 March up to 0.2 cm thick. Since Ebeko is not monitored by seismic instruments, KVERT relies on visual observations and satellite images for monitoring. 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. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php KRAKATAU Indonesia 6.102°S, 105.423°E; summit elev. 813 m During 27-30 March and 1 April, CVGHM reported that visual observations of Krakatau when the weather was clear revealed that ash plumes rose 200-800 m above the Anak Krakatau crater. On 2 April, an ash eruption was seen on satellite imagery and reported by a pilot. A resultant ash plume drifted more than 60 km S. The Alert Level remained at 2 (on a scale of 1-4). Geologic Summary. Renowned Krakatau volcano lies in the Sunda Strait between Java and Sumatra. Collapse of the ancestral Krakatau edifice, perhaps in 416 AD, resulted in a 7-km-wide caldera. Remnants of this volcano formed Verlaten and Lang Islands; subsequently Rakata, Danan and Perbuwatan volcanoes were formed, coalescing to create the pre-1883 Krakatau Island. Caldera collapse during the catastrophic 1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only a remnant of Rakata volcano. The post-collapse cone of Anak Krakatau (Child of Krakatau), constructed within the 1883 caldera at a point between the former cones of Danan and Perbuwatan, has been the site of frequent eruptions since 1927. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ LLAIMA Central Chile 38.692°S, 71.729°W; summit elev. 3125 m During 2-3 April, SERNAGEOMIN reported that seismicity from Llaima increased in frequency and amplitude and evolved into continuous seismic tremor. Steam plumes with small amounts of ash were emitted. Late in the day on 3 April, observers reported incandescence from the main crater. Weak Strombolian explosions were produced by the N cone inside the crater. On 4 April, Strombolian activity and rhythmic explosions in the main crater originated from two nested pyroclastic cones. Incandescent tephra was ejected 700 m above the crater. The Alert Level was raised to Red. ONEMI reported that fine ash fell in Verde Lake in the Conguillío National Park (a 608 square kilometer park containing Llaima) and a lava flow 1 km long traveled W towards the Calbuco River. Access to local parks was restricted and twelve people self-evacuated. Later that day, authorities ordered an evacuation for people in high-risk areas, mainly due to the potential for lahars along the Calbuco River. According to news articles, 71 people evacuated. SERNAGEOMIN reported that Strombolian activity continued on 5 April. A dark gray ash plume drifted E; heavy ashfall was reported in Lago Verde. A lahar traveled down the Captrén River (NNE) and lava continued to travel down the W flank. On 6 April, poor weather mostly prevented visual observations, but continuous explosions were reported from Melipeuco (about 17 km SSE). Lahars again traveled down the Captrén River. Occasionally, gas-and-ash plumes were seen and drifted E; ash fell in areas E. Heavy ashfall and lapilli up to 1.5 cm in diameter fell in areas between Conguillio Lake (about 10 km ENE, in Conguillío National Park) and the Arcoiris Lake (less than 10 km ENE, in Conguillío National Park). On 7 April, gas and ash emitted from multiple points formed a plume that rose 1 km above the summit and drifted NE. The flanks of the volcano were covered with bombs, lapilli, and ash. 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. Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/index.php, Oficina Nacional de Emergencia - Ministerio del Interior (ONEMI) http://www.onemi.cl/, Reuters http://au.news.yahoo.com/a/-/world/5478911 NYAMURAGIRA Democratic Republic of Congo 1.408°S, 29.20°E; summit elev. 3058 m A recent report from Goma Volcano Observatory (GVO) noted a seismic swarm from Nyamuragira during 23-27 January and increased seismicity along the East African Rift since then. Scientists who visited the Nyiragongo summit crater on 22 and 24 March saw intense fumarolic activity in the summit crater of Nyamuragira through binoculars. The activity was concentrated in the southern area. GVO noted that seismic swarms typically precede eruptions by 3-5 months and that an eruption could occur from the southern side. Geologic Summary. Africa's most active volcano, Nyamuragira (Also spelled Nyamulagira) is a massive basaltic shield volcano N of Lake Kivu and NW of Nyiragongo volcano. Lava flows from Nyamuragira cover 1,500 sq km of the East African Rift. The 3058-m-high summit is truncated by a small 2 x 2.3 km summit caldera that has walls up to about 100 m high. About 40 historical eruptions have occurred since the mid-19th century within the summit caldera and from numerous fissures and cinder cones on the volcano's flanks. A lava lake in the summit crater, active since at least 1921, drained in 1938. Twentieth-century flank lava flows extend more than 30 km from the summit, reaching as far as Lake Kivu. Source: Goma Volcano Observatory (GVO) NYIRAGONGO Democratic Republic of Congo 1.52°S, 29.25°E; summit elev. 3470 m A recent report from Goma Volcano Observatory (GVO) noted a seismic swarm from Nyiragongo and Nyamuragira in January and increased seismicity along the East African Rift since then. Gas plumes from Nyiragongo were frequently emitted and contributed to acid rain that fell on inhabited areas. On 22 March, tremor was detected on nearby seismic networks. Scientists who visited the summit crater on 22 and 24 March observed active fumaroles along a fissure connecting the Shaheru (S flank) and Nyiragongo craters. Strong methane concentrations were detected. The lava lake level had dropped 20 m compared to 27 February. A small area of the lava lake was active and lava fountains were seen. The temperature of some fissures had increased by 4 degrees Celsius since 27 February. Geologic Summary. One of Africa's most notable volcanoes, Nyiragongo contained an active lava lake in its deep summit crater that drained catastrophically through its outer flanks in 1977. In contrast to the low profile of its neighboring shield volcano, Nyamuragira, Nyiragongo displays the steep slopes of a stratovolcano. Benches in the steep-walled, 1.2-km-wide summit crater mark the levels of former lava lakes, which have been observed since the late 19th century. About 100 parasitic cones are located on the volcano's flanks and along a NE-SW zone extending as far as Lake Kivu. Monitoring is done from a small observatory building located in Goma, ~18 km S of the Nyiragongo crater. Source: Goma Volcano Observatory (GVO) PACAYA Guatemala 14.381°N, 90.601°W; summit elev. 2552 m INSIVUMEH reported that explosions in March ejected greater amounts of material that was deposited in the crater, enlarging the cones there. On 23 March, visual and audible changes in Strombolian activity were noted. Vigorous degassing produced sounds resembled airplane engines. In a report issued on 3 April, INSIVUMEH stated that Strombolian explosions from MacKenney cone during the previous few days ejected material 25 m into the air. On 2 April, lava flow volume increased, sending four lava flows W and one SW; the flows traveled 25-200 m. The seismic network detected tremor and explosions. On 6 April, lava flows on the W flank traveled 150-300 m, causing lava to pile up on the SW flank. Activity from MacKenney cone was continuous; one cone emitted gas and explosions about every 5-10 minutes, and a second cone ejected tephra 25 m high. On 7 April, one lava flow traveled 150 m W and one traveled 200 m SW. INSIVUMEH recommended that CONRED coordinate with authorities in Pacaya National Park to restrict visitors from climbing Pacaya. 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/ REDOUBT Southwestern Alaska 60.485°N, 152.742°W; summit elev. 3108 m During 1-3 April, AVO reported that Redoubt continued to emit steam, gases, and minor amounts of ash visible on the Redoubt Hut web camera. On 1 and 2 April, satellite images showed a plume containing some ash extending about 65 km ENE at altitudes of 4.6-7.6 km (15,000-25,000 ft) a.s.l. Thermal anomalies detected in infrared images were most likely due to lava dome extrusion in the summit crater. On 3 April, AVO lowered the Volcanic Alert Level to Watch and the Aviation Color Code to Orange due to a decreased intensity of ash production. AVO overflights and photography confirmed that a lava dome was growing at the summit. Occasional avalanches of hot blocks from the dome traveled a short distance down the N flank. On 4 April, a significant explosion produced an ash plume that rose to an altitude of 15.2 km (50,000 ft) a.s.l. and drifted SE. Seismic data indicated that a lahar traveled down the Drift River valley. AVO raised the Alert Level to Warning and the Aviation Color Code to Red, the highest levels. During 5-6 April, small earthquakes and intermittent tremor continued to be detected. The web camera showed a continuously emitted plume of primarily steam and gas that rose to an altitude of 7.7 km (25,300 ft) a.s.l. and drifted SE. A small, intermittent plume rose from the NW base of the volcano, possibly from the interaction of hot debris with snow, ice, and water. On 6 April, AVO again lowered the Volcanic Alert Level to Watch and the Aviation Color Code to Orange due to seismic patterns and emissions of only very minor ash. A gas-and-steam plume rose to an altitude less than 7.7 km (25,300 ft) a.s.l. and drifted NE. On 7 April, a small steam-and-ash plume was seen on satellite imagery and drifted 16-24 km SE at altitudes of 4.6-6.1 km (15,000-20,000 ft) a.s.l. 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. Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/ Ongoing Activity ASAMA Honshu 36.403°N, 138.526°E; summit elev. 2568 m On 7 April, JMA lowered the Alert Level for Asama from 3 to 2 (on a scale of 1-5). Geologic Summary. Asama, Honshu's most active volcano, is located at the junction of the Izu-Marianas and NE Japan arcs and has an historical record dating back at least to the 11th century. The modern cone of Maekake-yama is situated E of the horseshoe-shaped remnant of an older andesitic volcano, Kurofu-yama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic and rhyolitic lava cone was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 years BP, and by growth of the Ko-Asama-yama lava dome on the E flank. Maekake-yama is probably only a few thousand years old, but has had several major Plinian eruptions, the last two of which occurred in 1108 and 1783 AD. Source: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/indexe.html 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 5-6 April ash plumes from Batu Tara rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 40-210 km 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: Darwin Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m INGEOMINAS reported that pulsating gas plumes from Galeras, sometimes containing ash, were seen when weather allowed during 3-7 April and rose to altitudes less than 6 km (19,700 ft) a.s.l. Overflights on 5, 6, and 7 April revealed that the emissions came from different areas in the main crater. Zones of high temperatures (180 degrees Celsius) were noted; an incandescent area measured 500 degrees Celsius on 7 April. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity"). 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. Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co// KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m KVERT reported that seismic activity at Karymsky was above background levels during 27 March-3 April. A thermal anomaly on the volcano was seen in satellite imagery on 31 March. 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 During 1-7 April, 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. Surface flows on the coastal plain were seen or detected by satellite imagery. Occasional explosions occurred from the Waikupanaha ocean entry. On 2 April, geologists found that the surface lava flow feeding the Kupapa'u entry was 1 km (0.6 m) wide. The vent in Halema'uma'u crater continued to produce a predominantly white plume that drifted mainly SW. Incandescence was intermittently seen from the vent, and sounds resembling rushing gas were sometimes heard in the vicinity of the crater. Variable amounts of tephra including some Pele's hair, Pele's tears, and rock dust were retrieved daily from collection bins placed near the plume. During 31 March and 1 April, geologists utilizing an infrared camera to look into the vent saw a lava pond that rose and fell approximately every 3 minutes. During 2-3 April, the lava pond was replaced by a large hot opening; ejected spatter built up a rim. The sulfur dioxide emission rate at the summit was elevated; measurements were 550, 800, and 700 tonnes per day on 1, 2, and 3 April, 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/ KORYAKSKY Eastern Kamchatka 53.320°N, 158.688°E; summit elev. 3456 m KVERT reported that seismic activity at Koryaksky was at background levels during 27 March-3 April. Gas plumes containing a small amount of ash rose to an altitude of 4 km (13,200 ft) a.s.l. and drifted E, SE, S, and W during the reporting period. During 27-28 and 31 March, and 1-2 April, gas-and-ash plumes were also seen on satellite imagery and drifted 313 km E, in southerly directions. The Level of Concern Color Code remained Orange. Geologic Summary. The large symmetrical Koryaksky stratovolcano is the most prominent landmark of the NW-trending Avachinskaya volcano group, which towers above Kamchatka's largest city, Petropavlovsk. Erosion has produced a ribbed surface on the eastern flanks of the 3456-m-high volcano; the youngest lava flows are found on the upper western flank and below SE-flank cinder cones. No strong explosive eruptions have been documented during the Holocene. Extensive Holocene lava fields on the western flank were primarily fed by summit vents; those on the SW flank originated from flank vents. Lahars associated with a period of lava effusion from south- and SW-flank fissure vents about 3900-3500 years ago reached Avacha Bay. Only a few moderate explosive eruptions have occurred during historical time. Koryaksky's first historical eruption, in 1895, also produced a lava flow. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m CENAPRED reported that on 1 April an ash plume from Popocatépetl rose 1 km above the summit. A small ash emission was seen the next day. Geologic Summary. Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5,426 m 70 km SE of Mexico City and is North America's second-highest volcano. Frequent historical eruptions have been recorded since the beginning of the Spanish colonial era. A small eruption on 21 December 1994 ended five decades of quiescence. Since 1996 small lava domes have incrementally been constructed within the summit crater and destroyed by explosive eruptions. Intermittent small-to-moderate gas-and-ash eruptions have continued, occasionally producing ashfall in neighboring towns and villages. Source: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.unam.mx/ RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m RVO reported that during 27 March-2 April white and occasionally gray or brown plumes from Rabaul caldera's Tavurvur cone rose 1 km above the crater. Plumes drifted SE and NW. Incandescence from the summit crater was seen at night and roaring noises were reported. On 2 April, light ashfall was reported in Rabaul town (3-5 km NW) and surrounding areas. Based on analysis of satellite imagery, the Darwin VAAC reported that on 5 April an ash plume rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted about 37 km NE. On 7 April, ash plumes rose to an altitude of 3 km (10,000 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: Herman Patia, Rabaul Volcano Observatory (RVO), Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m Based on information from JMA, the Tokyo VAAC reported that during 5-7 April explosions and eruptions from Sakura-jima produced plumes that rose to altitude of 2.1-3 km (7,000-10,000 ft) a.s.l. Plumes drifted SE on 5 April and S on 7 April. 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 SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m KVERT reported that seismic activity at Shiveluch was above background levels 27 March-3 April. Based on interpretations of seismic data, ash plumes likely rose to an altitude of 5.5 km (18,000 ft) a.s.l. According to observers, fumaroles were active daily and explosions produced ash plumes that rose to an altitude of 6 km (19,700 ft) a.s.l. on 31 March. Analysis of satellite imagery revealed a daily thermal anomaly on the lava dome and an ash plume that drifted 80 km S on 1 April. 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 SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m MVO reported that during 27 March-3 April activity from the Soufrière Hills lava dome was at a low level. On 1 April, a small pyroclastic flow traveled E down the Tar River Valley. The Hazard Level remained at 3. On 6 April, the Washington VAAC reported that an ash plume drifting at altitudes of 2.7-4.9 km (9,000-16,000 ft) a.s.l. was seen by a pilot flying from Antigua to Beef Island, 200-300 km NW. Ash was not seen on satellite imagery. 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/, Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m Based on information from JMA, the Tokyo VAAC reported explosions from Suwanose-jima on 6 April. 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 During 1-3 and 5 April, IG reported that steam or steam-and-ash plumes from Tungurahua rose a few meters to 1 km above the crater. Plumes drifted S, SW, and NNW. On 6 April, fumarolic plumes rose 500-600 m. Light ashfall was reported about 8 km SW in the town of Manzano. 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. ==============================================================
