************************************************************* GVP/USGS Weekly Volcanic Activity Report 3-9 October 2007 http://www.volcano.si.edu/reports/usgs/ ************************************************************* New Activity/Unrest: | Anatahan, Mariana Islands | Bulusan, Philippines | Jebel at Tair, Yemen | Kelut, Indonesia Ongoing Activity: | Chikurachki, Russia | Galeras, Colombia | Karymsky, Russia | Kilauea, USA | Manam, Papua New Guinea | Rabaul, Papua New Guinea | Shiveluch, Russia | Soufrière Hills, Montserrat | St. Helens, USA | Tungurahua, Ecuador | Ubinas, Perú New Activity/Unrest ANATAHAN Mariana Islands, central Pacific Ocean 16.35°N, 145.67°E; summit elev. 788 m Gas-and-steam plumes from Anatahan were visible on satellite imagery when the island was visible through cloud cover during 18 August-15 September. USGS reported that seismicity increased on 9 September and remained elevated through 15 September. On 15 September, the Volcanic Alert Level was raised to Advisory and the Aviation Color Code was raised to Yellow. Seismic activity remained above background levels during 15 September-3 October. During 21-24 September, elevated levels of sulfur dioxide were reported in Saipan. Geologic Summary. The elongate, 9-km-long island of Anatahan in the central Mariana Islands consists of large stratovolcano with a 2.3 x 5 km, E-W-trending compound summit caldera. The larger western caldera is 2.3 x 3 km wide, and its western rim forms the island's 790-m high point. Ponded lava flows overlain by pyroclastic deposits fill the floor of the western caldera, whose SW side is cut by a fresh-looking smaller crater. The 2-km-wide eastern caldera contained a steep-walled inner crater prior to the 2003 eruption whose floor was only 68 m above sea level. Sparseness of vegetation on the most recent lava flows on Anatahan had indicated that they were of Holocene age, but the first historical eruption of Anatahan did not occur until May 2003, when a large explosive eruption took place forming a new crater inside the eastern caldera. Source: Emergency Management Office of the Commonwealth of the Mariana Islands and the US Geological Survey Hawaiian Volcano Observatory http://hvo.wr.usgs.gov/cnmi/index.html Anatahan Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0804-20= BULUSAN Luzon, Philippines 12.770°N, 124.05°E; summit elev. 1,565 m Based on seismic interpretation, PHIVOLCS reported two explosions from Bulusan on 4 October. Thick clouds obscured observations of the summit. According to news articles, ashfall was reported in several villages. Geologic Summary. Luzon's southernmost volcano, Bulusan, was constructed within the 11-km-diameter dacitic Irosin caldera, which was formed more than 36,000 years ago. A broad, flat moat is located below the prominent SW caldera rim; the NE rim is buried by the andesitic Bulusan complex. Bulusan is flanked by several other large intracaldera lava domes and cones, including the prominent Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit of Bulusan volcano is unvegetated and contains a 300-m-wide, 50-m-deep crater. Three small craters are located on the SE flank. Many moderate explosive eruptions have been recorded at Bulusan since the mid-19th century. Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS) http://www.phivolcs.dost.gov.ph/, Agence France-Presse http://news.yahoo.com/s/afp/20071004/sc_afp/philippinesvolcano_071004174813 Bulusan Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-01= JEBEL AT TAIR Red Sea, Yemen 15.55°N, 41.82°E; summit elev. 244 m According to news reports, the eruption from the Jebel at Tair that began on 30 September continued on 3 October with lava flows noted on the W part of the island. Geologic Summary. The basaltic Jebel at Tair volcano rises from a 1200 m depth in the south-central Red Sea, forming an oval-shaped island about 3 km long. Jebel at Tair (one of many variations of the name, including Djebel Teyr, Jabal al Tayr, and Jibbel Tir ) is the northernmost known Holocene volcano in the Red Sea and lies SW of the Farisan Islands. Youthful basaltic pahoehoe lava flows from the steep-sided central vent, Jebel Duchan, cover most of the island. They drape a circular cliff cut by wave erosion of an older edifice and extend beyond it to form a flat coastal plain. Pyroclastic cones are located along the NW and southern coasts, and fumarolic activity occurs from two uneroded scoria cones at the summit. Radial fissures extend from the summit, some of which were the sources of lava flows. The island is of Holocene age, and explosive eruptions were reported in the 18th and 19th centuries. Sources: Gulf News http://www.gulf-news.com/region/Yemen/10158021.html Jebel at Tair Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0201-01= KELUT Java, Indonesia 7.93°S, 112.31°E; summit elev. 1,731 m According to news articles, carbon dioxide and other gases emitted from Kelut reached 7 times normal levels. Increased seismicity and gas emissions prompted people from villages near the summit to self-evacuate. Villagers and tourists were advised not go within a 5 km radius of the active crater. Geologic Summary. The relatively inconspicuous 1,731-m-high Kelut stratovolcano contains a summit crater lake that has been the source of some of Indonesia's most deadly eruptions. A cluster of summit lava domes cut by numerous craters has given the summit a very irregular profile. More than 30 eruptions have been recorded from Gunung Kelut since 1000 AD. The ejection of water from the crater lake during Kelut's typically short, but violent eruptions has created pyroclastic flows and lahars that have caused widespread fatalities and destruction. After more than 5,000 people were killed during the 1919 eruption, an ambitious engineering project sought to drain the crater lake. This initial effort lowered the lake by more than 50 m, but the 1951 eruption deepened the crater by 70 m, leaving 50 million cubic meters of water after repair of the damaged drainage tunnels. After more than 200 people were killed in the 1966 eruption, a new deeper tunnel was constructed, lowering the lake's volume to only about 1 million cubic meters prior to the 1990 eruption. Sources: Reuters http://news.yahoo.com/s/nm/20071004/sc_nm/indonesia_volcano_dc_1 Kelut Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-28= Ongoing Activity CHIKURACHKI Kuril Islands, Russia 50.325°N, 155.458°E; summit elev. 1,816 m KVERT reported that a gas-and-ash plume from Chikurachki was visible on satellite imagery drifting ESE on 4 October. Chikurachki volcano is not monitored with seismic instruments. The Level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. Geologic Summary. Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized scoria deposits covering the upper part of the young cone give it a distinctive red color. Lava flows from 1,816-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The more erosionally modified Tatarinov group of six volcanic centers is located immediately to the S of Chikurachki. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959. Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml Chikurachki Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0900-036= GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4,276 m INGEOMINAS reported that during 4-5 October, steam plumes from Galeras rose to altitudes of 5.8-6.3 km (19,000-20,700 ft) a.s.l. Occasional pulses of ash accompanied the steam emissions. Plumes drifted N and NW. The Alert Level remained at 3 (changes in the behavior of volcanic activity have been noted) on a scale of 4-1. 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. 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/ Galeras Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1501-08= KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m KVERT reported that seismic activity at Karymsky was above background levels during 28 September-5 October. Based on seismic interpretation, ash plumes may have risen to an altitude of 3.5 km (11,500 ft) a.s.l. during the reporting period. Observations of satellite imagery revealed that a thermal anomaly was present in the crater during 27 and 29-30 September and 1 and 3 October. Ash plumes drifted SE and E on 30 September and 1 and 3 October. The Level of Concern Color Code remained at Orange. Based on information from KEMSD and KVERT, observations in the Petropavlovsk-Kamchatsky Flight Information Region (FIR), and pilot reports, the Tokyo VAAC reported that ash plumes rose to an altitude of 3-3.7 km (10,000-12,000 ft) a.s.l. on 5, 7, and 8 October. Plumes drifted E and NE. 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. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html Karymsky Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-13= KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m HVO reported that during 3-9 October fissure segment D from Kilauea's 21 July fissure eruption continued to feed an advancing 'a'a lava flow that occasionally overflowed its channel edges. Lava flows advanced NE over earlier flows and along the S margin of earlier flows. On 3 October, aerial observations revealed that the lava flow along the S margin burned trees in a kipuka (an "island" of vegetation). A few small earthquakes were located beneath Halema'uma'u crater and the S flank during the reporting period. Geologic Summary. Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world's most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed by lava flows less than about 1,100 years old; 70% of the volcano's surface is younger than 600 years. The latest Kilauea eruption began in January 1983 along the E rift zone. This long-term ongoing eruption from Pu'u 'O'o-Kupaianaha has produced lava flows that have traveled 11-12 km from the vents to the sea, paving broad areas on the S flank of Kilauea and adding new land beyond the former coastline. Source: US Geological Survey Hawaiian Volcano Observatory http://volcano.wr.usgs.gov/hvostatus.php Kilauea Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01- MANAM offshore New Guinea, Papua New Guinea 4.10°S, 145.06°E; summit elev. 1,807 m RVO reported that incandescence was visible at the summit of Manam on 29 September and 1 October. The Main Crater occasionally released diffuse ash plumes during 1-5 October. Plumes drifted SW. White vapor plumes were emitted from South Crater. Based on information from RVO and observations of satellite imagery, the Darwin VAAC reported that an ash plume rose to an altitude of 3.7 km (12,000 ft) a.s.l. and drifted SW. Geologic Summary. The 10-km-wide island of Manam is one of Papua New Guinea's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1,807-m-high stratovolcano to its lower flanks. These "avalanche valleys," regularly spaced 90 degrees apart, channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five satellitic centers are located near the island's shoreline. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during the past century into the SE avalanche valley. Frequent historical eruptions have been recorded since 1616. Sources: Herman Patia, Rabaul Volcano Observatory, Darwin Volcanic Ash Advisory Centre http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html Manam Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0501-02= RABAUL New Britain Island, Papua New Guinea 4.271°S, 152.203°E; summit elev. 688 m RVO reported that ash plumes from Rabaul caldera's Tavurvur cone rose to altitudes of approximately 1.7-2.7 km (5,600-8,900 ft) a.s.l. and drifted NW on 3 October. Ashfall was reported from areas downwind, including Rabaul Town. Ash plumes on 4 October drifted W and resulted in ashfall in Matupit Island, Malaguna. Incandescent fragments were ejected from the summit. On 5 October, vapor plumes with minor ash content were noted. Rumbling noises occasionally accompanied the ash emissions. Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the E, where its floor is flooded by Blanche Bay. Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city. Source: Herman Patia, Rabaul Volcano Observatory, Rabaul Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-14= SHIVELUCH Kamchatka Peninsula, Russia 56.653°N, 161.360°E; summit elev. 3,283 m During 28 September-5 October, KVERT reported that seismic activity at Shiveluch was above background levels. Based on seismic interpretation, ash plumes rose to an altitude of 5.3 km (17,400 ft) a.s.l. and hot avalanches occurred on 27 and 29 September. Ash plumes were visible on satellite imagery drifting WSW and SE. Observations of video footage indicated that gas-and-steam plumes rose up to altitudes of 4.5 km and 3.5 km (14,800 and 11,500 ft) a.s.l. on 27 September and 2 October, respectively. Fumarolic activity was noted on 1 October. A thermal anomaly was present in the crater on satellite imagery during the reporting period. The Level of Concern Color Code remained at Orange <http://www.avo.alaska.edu/color_codes.php>. Based on information from the KEMSD, the Tokyo VAAC reported that an eruption plume rose to an altitude of 5.8 km (19,000 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 horseshoe-shaped caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. During the 1990s, intermittent explosive eruptions took place from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964. Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml, Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html Shiveluch Information from the Global Volcanism Program http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1000-27= SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m MVO reported that during 3-9 October the lava dome at Soufrière Hills changed very little, based on visual observations. Seismic activity was very low and low-level rockfall activity continued. On 3 October, lahars were noted in several drainages, including the Belham river valley to the NW. Steam venting was noted in the upper parts of Belham Valley and in Tyres Ghaut to the NW. The Alert Level remained elevated at 4 (on a scale of 0-5). Geologic Summary. The complex, dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. English's Crater, a 1-km-wide crater breached widely to the east, was formed during an eruption about 4000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufrière Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth and pyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption. Source: Montserrat Volcano Observatory http://www.mvo.ms/ Soufrière Hills Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1600-05= ST. HELENS Washington, USA 46.20°N, 122.18°W; summit elev. 2,549 m Data from deformation-monitoring instruments indicated that during 3-9 October lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels, punctuated by M 1.5-2.5, and occasionally larger, earthquakes. Clouds occasionally inhibited visual observations. Geologic Summary. Prior to 1980, Mount St. Helens formed a conical, youthful volcano sometimes known as the Fuji-san of America. During the 1980 eruption the upper 400 m of the summit was removed by slope failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially filled by a lava dome. Mount St. Helens was formed during nine eruptive periods beginning about 40-50,000 years ago, and has been the most active volcano in the Cascade Range during the Holocene. The modern edifice was constructed during the last 2,200 years, when the volcano produced basaltic as well as andesitic and dacitic products from summit and flank vents. Historical eruptions in the 19th century originated from the Goat Rocks area on the N flank, and were witnessed by early settlers. Source: US Geological Survey Cascades Volcano Observatory http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity/framework.html St. Helens Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05- TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m IG reported that ash plumes from Tungurahua rose to altitudes of 5-8 km (16,400-26,200 ft) a.s.l. during 2-9 October and drifted N, NW, W, E, and NE. Clouds inhibited observations on 7 and 9 October. Ashfall was reported in areas to the SW, NW, and N during 3-7 and 9 October. Noises resembling blocks rolling down the flanks, roars, and "cannon shots" were heard during 3-9 October. On 9 October, a lahar with rocks up to 20 cm in diameter descended the Bilbao river valley. Geologic Summary. The steep-sided Tungurahua stratovolcano towers more than 3 km above its northern base. It sits ~140 km S of Quito, Ecuador's capital city, and is one of Ecuador's most active volcanoes. Historical eruptions have been restricted to the summit crater. They have been accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. The last major eruption took place from 1916 to 1918, although minor activity continued until 1925. The latest eruption began in October 1999 and prompted temporary evacuation of the town of Baños on the N side of the volcano. Source: Instituto Geofísico-Escuela Poltécnica Nacional http://www.igepn.edu.ec/ Tungurahua Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08= UBINAS Perú 16.355°S, 70.903°W; summit elev. 5,672 m Based on pilot reports, the Buenos Aires VAAC reported that ash plumes from Ubinas rose to altitudes of 5.5-6.4 km (18,000-21,000 ft) a.s.l. and drifted E on 12 and 20 September. Ash was not identified on satellite imagery. Geologic Summary. 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 (VAAC) 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. ==============================================================
