****************************************************** GVP/USGS Weekly Volcanic Activity Report 3-9 May 2006 ****************************************************** From: Gari Mayberry <mayberry@xxxxxxxxxxxxxx> GVP/USGS Weekly Volcanic Activity Report 3-9 May 2006 http://www.volcano.si.edu/reports/usgs/ New Activity/Unrest: | Bezymianny, Russia | Merapi, Indonesia Ongoing Activity: | Bagana, Papua New Guinea | Barren Island, Andaman Islands | Cleveland, USA | Galeras, Colombia | Kilauea, USA | Lopevi, Vanuatu | Manam, Papua New Guinea | St. Helens, USA | Tungurahua, Ecuador | Ubinas, Perú New Activity/Unrest BEZYMIANNY Kamchatka Peninsula, Russia 55.98°N, 160.59°E; summit elev. 2,882 m; All times are local (= UTC + 13 hours) During 28 April to 5 May, Bezymianny's lava dome continued to grow. Seismicity was above background levels during 30 April to 3 May. Incandescent avalanches were visible on 4 May. At the lava dome, fumarolic activity occurred and thermal anomalies were visible on satellite imagery. Bezymianny was at Concern Color Code Yellow, which meant an explosive eruption was possible in the following 4 weeks <http://www.avo.alaska.edu/color_codes.php>. On 7 May the Concern Color Code was raised to Orange due to an increase in seismicity and the number of incandescent avalanches (14 occurred on 6 May in comparison to 4-6 during the previous 2 days). Intense fumarolic activity occurred, with occasional small amounts of ash. KVERT reported that an explosive eruption was possible in the next 1 or 2 weeks. On 9 May around 1935, the Concern Color Code was raised to Red, the highest level, due to increased seismicity and incandescent avalanches. A gas plume rose higher than 7 km (23,000 ft) a.s.l. and a strong thermal anomaly was visible on satellite imagery. An explosive eruption was expected in the next 1 or 2 days. An explosive eruption occurred at Bezymianny on 9 May during 2121 to 2145. The explosion produced an ash column that rose to a height of ~15 km (49,200 ft) a.s.l. A co-ignimbrite ash plume was about 40 km in diameter and mainly extended NE of the volcano. On 10 May around 0100, seismicity returned to background levels and the Concern Color Code was reduced to Orange. Small fumarolic plumes were observed during the early morning of the 10th and lava probably began to flow at the lava dome. Background. Prior to its noted 1955-56 eruption, Bezymianny volcano had been considered extinct. The modern Bezymianny volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral volcano that was built between about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of Mount St. Helens in 1980, 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 http://www.kcs.iks.ru/ivs/kvert/updates.shtml Bezymianny Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-25= MERAPI central Java, Indonesia 7.542°S, 110.442°E; summit elev. 2,947 m CVGHM reported that on 6 May, gas plumes rose to 800 m above Merapi (or 12,300 ft a.s.l.) and 18 incandescent avalanches of volcanic material were observed. On 7 May, 26 incandescent avalanches that extended about 100 m were seen during the morning. Incandescence was seen at the summit ten times. On 6 and 7 May, the lava dome continued to grow and seismicity was dominated by multi-phase earthquakes. Shallow volcanic earthquakes and signals from landslides and rockfalls were also recorded. On 8 May, the Darwin VAAC reported that CVGHM warned of a plume rising to ~3.7 km (12,000 ft) a.s.l. No ash was visible on satellite imagery. Merapi remained at Alert Level 3 (on a scale of 1-4), as it has since 12 April. Background. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately N of the major city of Yogyakarta. The steep-sided modern Merapi edifice, its upper part unvegetated due to frequent eruptive activity, was constructed to the SW of an arcuate scarp cutting the eroded older Batulawang volcano. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated and inhabited lands on the volcano's western-to-southern flanks and caused many fatalities during historical time. The volcano is the object of extensive monitoring efforts by the Merapi Volcano Observatory of the Volcanological Survey of Indonesia. Sources: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://www.vsi.esdm.go.id/portal/html/index.php, Darwin Volcanic Ash Advisory Center http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html Merapi Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-25= Ongoing Activity BAGANA Bougainville Island, Papua New Guinea 6.14°S, 155.19°E; summit elev. 1,750 m On 4 May, satellite imagery showed an ash plume from Bagana at a height of ~3 km (10,000 ft) a.s.l. extending 4 km W. Background. 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 Center http://www.bom.gov.au/info/vaac/advisories.shtml Bagana Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0505-02= BARREN ISLAND Andaman Islands, Indian Ocean, India 12.29°N, 93.88°E; summit elev. 354 m On 3 May, low-level ash plumes from Barren Island were visible on satellite imagery extending N. Background. 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 a 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 http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html Barren Island Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0600-01= CLEVELAND Aleutian Islands, USA 52.82°N, 169.95°W; summit elev. 1,730 m; All times are local (= UTC - 8 hours) On the morning of 2 May beginning at 0101, a thermal anomaly and continuous plume from Cleveland were seen on satellite imagery. The plume extended ~50 km SW of the volcano and was visible on satellite imagery for about 6 hours. Satellite data suggested a maximum cloud height of ~1 km (3,500 ft) a.s.l. There was no indication of ash in the observed cloud. No further activity was detected at Cleveland after 2 May. Cleveland was not assigned a Concern Color Code because there is no real-time seismic network at the volcano to monitor seismic changes. Background. 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/activity/avoreport.php?view=update Cleveland Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1101-24- GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4,276 m INGEOMINAS reported that Galeras remained at a critical state during 1-8 May, with a partially solidified lava dome in the main crater and low levels of seismicity. The sulfur-dioxide flux continued at very low levels. Galeras remained at Alert Level 2 (likely eruption in days or weeks). Background. 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. Long-term 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 http://www.ingeominas.gov.co/tmsingeominas/ModuloPublicacionPortal/PublicacionPortal.asp Galeras Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1501-08= KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m During 4-8 May, lava from Kilauea continued to flow off of a lava delta into the ocean at the East Lae`apuki entry. No surface lava flows were visible on the Puluma pali fault scarp, as has been the case since 8 February. Low-level volcanic tremor was recorded at Kilauea's summit, accompanied by a few small earthquakes. Volcanic tremor reached moderate levels at Pu`u `O`o. Small amounts of inflation and deflation occurred at the volcano. Background. 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 about 104 km2 of land on the S flank of Kilauea and building more than 200 hectares of new land. Source: US Geological Survey Hawaiian Volcano Observatory http://volcanoes.usgs.gov/update.html Kilauea information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01- LOPEVI Central Islands, Vanuatu 16.507°S, 168.346°E; summit elev. 1,413 m Based on information from a pilot report, the Wellington VAAC reported that on 7 May a small ash plume from Lopevi was visible below a height of ~3 km (10,000 ft) a.s.l. and an active lava flow was observed at the volcano. Background. The small 7-km-wide conical island of Lopevi is one of Vanuatu's most active volcanoes. A small summit crater containing a cinder cone is breached to the NW and tops an older cone that is rimmed by the remnant of a larger crater. The basaltic-to-andesitic volcano has been active during historical time at both summit and flank vents, primarily on the NW and SE sides, producing moderate explosive eruptions and lava flows that reached the coast. Historical eruptions at the 1,413-m-high volcano date back to the mid-19th century. The island was evacuated following eruptions in 1939 and 1960. The latter eruption, from a NW-flank fissure vent, produced a pyroclastic flow that swept to the sea and a lava flow that formed a new peninsula on the western coast. Source: Wellington Volcanic Ash Advisory Center http://www.ssd.noaa.gov/VAAC/OTH/NZ/messages.html Lopevi Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0507-05= MANAM offshore New Guinea, Papua New Guinea 4.10°S, 145.06°E; summit elev. 1,807 m On 8 May, an ash plume from Manam was visible on satellite imagery at a height of ~3 km (10,000 ft) a.s.l. Background. 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 Center http://www.bom.gov.au/info/vaac/advisories.shtml Manam Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0501-02= ST. HELENS Washington, USA 46.20°N, 122.18°W; summit elev. 2,549 m Growth of the new lava dome inside the crater of Mount St. Helens continued during 4-8 May, accompanied by low rates of seismicity, low emissions of steam and volcanic gases, and minor production of ash. The dome-building eruption that began in October 2004 continued at the same pace as in previous weeks, accompanied by low background levels of seismicity and other eruption indicators. A GPS (Global Positioning System) instrument on the new lava dome W of the vent continued to move W nearly 1 m per day. St. Helens remained at Volcano Advisory (Alert Level 2); aviation color code Orange. Background. 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 During 4-8 May, small-to-moderate explosions at Tungurahua produced plumes composed of gas, steam, and small amounts of ash. Seismicity was at relatively high levels and was dominated by signals from long-period earthquakes and explosions. Background. 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. Sources: Instituto Geofisico-Escuela Poltecnica Nacional http://www.igepn.edu.ec/vulcanologia/tungurahua/actividad/informet.htm, Washington Volcanic Ash Advisory Center http://www.ssd.noaa.gov/VAAC/messages.html Tungurahua Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08= UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m Based on information from significant meteorological advisories (SIGMET), the Buenos Aires VAAC reported that ash emitted from Ubinas during 4-8 May rose to a maximum height of ~6.7 km (22,000 ft) a.s.l. Background. A small, 1.2-km-wide caldera that cuts the top of Ubinas, Peru's most active volcano, gives it a truncated appearance. Ubinas is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Peru. The upper slopes of the stratovolcano, composed primarily of Pleistocene andesitic lava flows, steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas extend 10 km from the volcano. Widespread plinian pumice-fall deposits from Ubinas include some of Holocene age. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor explosive eruptions. Source: Buenos Aires Volcanic Ash Advisory Center http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html Ubinas Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1504-02= ============================================================== 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. ==============================================================
