***************************************************************** GVP/USGS Weekly Volcanic Activity Report 21-27 November 2007 http://www.volcano.si.edu/reports/usgs/ ***************************************************************** New Activity/Unrest: | Krakatau, Indonesia | Nyiragongo, D.R. of Congo | Ongoing Activity: | Bezymianny, Russia | Chikurachki, Russia | Concepción, Nicaragua | Karangetang, Indonesia | Karymsky, Russia | Kilauea, USA | Manam, Papua New Guinea | Ol Doinyo Lengai, Tanzania | Rabaul, Papua New Guinea | Santa María, Guatemala | Shiveluch, Russia | Soputan, Indonesia | Soufrière Hills, Montserrat | St. Helens, USA | Tungurahua, Ecuador | Ubinas, Perú New Activity/Unrest KRAKATAU Indonesia 6.10°S, 105.43°E; summit elev. 813 m According to a news article on 22 November, seismicity from Anak Krakatau declined in frequency. Based on a pilot report, the Darwin VAAC reported that an ash plume rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted NE on 24 November. Visitors and tourists were advised not to go within a 3-km radius of the summit. The Alert Level remained at 3 (on a scale of 1-4). Geologic Summary. The 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. Sources: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html, Bernama http://www.bernama.com.my/bernama/v3/news_world.php?id=297754 Krakatau Information from the Global Volcanism Program http://www.vsi.esdm.go.id/portal/html/index.php NYIRAGONGO Democratic Republic of the Congo 1.52°S, 29.25°E; summit elev. 3,469 m ; All times are local (= UTC + 2 hours) Based on observations of satellite imagery, the Toulouse VAAC reported that an eruption from Nyiragongo occurred before 0600 on 21 November. 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. Extremely fluid, fast-moving lava flows draining from the summit lava lake in 1977 caused many fatalities, as did lava flows inundating portions of the city of Goma in January 2002. Source: Toulouse Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/FR/messages.html Nyiragongo Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0203-03= Ongoing Activity BEZYMIANNY Kamchatka Peninsula, Russia 55.98°N, 160.59°E; summit elev. 2,882 m KVERT reported that seismic activity at Bezymianny was at background levels during 16-18 and 21-23 November and above background levels on 19 and 20 November. Visual observations and video footage analysis indicated that gas-and-steam plumes were observed on 17 and 18 November. Based on observations of satellite imagery, a thermal anomaly was present in the crater during 16-17 and 21 November. KVERT lowered the level of Concern Color Code to Yellow <http://www.avo.alaska.edu/color_codes.php>. Geologic Summary. 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 (KVERT) http://www.kscnet.ru/ivs/kvert/updates.shtml Bezymianny Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-25= CHIKURACHKI Kuril Islands, Russia 50.325°N, 155.458°E; summit elev. 1,816 m KVERT reported that clouds obscured satellite views of Chikurachki and ash plumes were not observed during 16-23 November. The Level of Concern Color Code was lowered to Green <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= CONCEPCIÓN Nicaragua 11.538°N, 85.622°W; summit elev. 1,700 m According to a news article, an eruption from Concepción on 24 November produced large ash plumes. Ashfall was reported in nearby communities. Geologic Summary. Volcán Concepción is one of Nicaragua's highest volcanoes and is also one of its most active. The symmetrical volcano forms the NW half of the dumbbell-shaped island of Ometepe in Lake Nicaragua. Concepción is connected to neighboring Madera volcano by a narrow isthmus. N-S-trending fractures cutting across the volcano are associated with spatter cones, cinder cones, and maars located on the middle N flank and on the lower S flank down to Lake Nicaragua. Concepción has had frequent moderate explosive eruptions in the past century, most of which have originated from a small summit crater. Source: Associated Press http://www.iht.com/articles/ap/2007/11/25/america/LA-GEN-Nicaragua-Volcano.php Concepción Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1404-12= KARANGETANG [Api Siau] Siau Island, Indonesia 2.47°N, 125.29°E; summit elev. 1,784 m CVGHM reported that the Alert Status of Karangetang was lowered on 23 November from 3 to 2 (on a scale of 1-4) due to a decrease in seismicity and decrease of observed plume height and density. Geologic Summary. Karangetang (also known as Api Siau) lies at the northern end of the island of Siau, N of Sulawesi. The 1,784-m-high stratovolcano contains five summit craters along a N-S line. One of Indonesia's most active volcanoes, Karangetang has had more than 40 recorded eruptions since 1675. Twentieth-century eruptions have included frequent explosions, sometimes accompanied by pyroclastic flows and lahars. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ Karangetang Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0607-02= KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m KVERT reported that seismic activity at Karymsky was at background levels during 16-17 and 19-23 November and above background levels on 18 November. Based on seismic interpretation, possible weak ash explosions occurred on 17 November. The Level of Concern Color Code <http://www.avo.alaska.edu/color_codes.php> 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/updates.shtml 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 Based on overflights and web camera views, HVO reported that on 21 November lava from Kilauea erupted from the S side of the perched channel nearly fed by fissure D. The bypass of lava from the channel to the surface resulted in an estimated 10 m drop in channel levels. Pahoehoe flows E and SE of Pu'u Kia'i continued to advance. The first new lava flows advanced a few hundred meters N and the second flow advanced 1 km SE. During 23-27 November, lava from fissure D built a low shield over the breakout point and fed a single flow that advanced 2 km. Lava flowed back into the uppermost part of the perched channel where lava levels were 6 m below the rim and crust overturned on 24 November. During 24-27 November, lava resumed supplying the perched channel and occasionally overflowed the edges. 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 Manam's Main Crater and occasionally South Crater released white vapor plumes during 16 October-24 November. The emissions were accompanied by ash plumes from Main Crater during 5-8 November and from South Crater during 5-6 November. Roaring noises were heard on 30 October. Incandescence at the summit was visible on 30 October and 4 and 5 November. 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. Source: Herman Patia, Rabaul Volcano Observatory Manam Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0501-02= OL DOINYO LENGAI Tanzania, eastern Africa 2.751°S, 35.902°E; summit elev. 2,890 m Based on information from the Tanzania MVO, the Toulouse VAAC reported that Ol Doinyo Lengai remained active and pilots should avoid flying near the volcano. Ash was not identified on satellite imagery. Geologic Summary. The symmetrical Ol Doinyo Lengai stratovolcano is the only volcano known to have erupted carbonatite tephras and lavas in historical time. The prominent volcano, known as "The Mountain of God," rises abruptly above the broad plain S of Lake Natron. The cone-building stage of the volcano ended about 15,000 years ago and was followed by periodic ejection of natrocarbonatite and nephelinite tephra during the Holocene. Historical eruptions have consisted of smaller tephra eruptions and emission of numerous natrocarbonatitic lava flows on the floor of the summit crater. Petrologists first observed the eruption of carbonatitic lava flows in the 1960s. Subsequent more frequent visits have documented long-term lava effusion in the summit crater that would not have been seen from the foot of the volcano. Source: Toulouse Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/FR/messages.html Ol Doinyo Lengai Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0202-12= RABAUL New Britain Island, Papua New Guinea 4.271°S, 152.203°E; summit elev. 688 m RVO reported that white plumes from Rabaul caldera's Tavurvur cone rose to an altitude of 1.2 km (3,900 ft) a.s.l. and drifted ESE and NNW during 17-28 November. Plumes drifted N, NW, and W. Continuous incandescence at the summit was observed and roaring noises were occasionally heard. A lava dome on the crater floor was seen on video images on 25 November. The dome was an estimated 20 m high and 50 m across, and was strongly degassing. 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= SANTA MARÍA Guatemala 14.756°N, 91.552°W; summit elev. 3,772 m Based on observations of satellite imagery, the Washington VAAC reported that an ash plume from Santa María's Santiaguito lava dome complex was visible on 23 November. On 26 November, a steam-and-ash plume rose to an altitude of 3.7-4.6 km (12,000-15,000 ft) a.s.l. and drifted SW. Geologic Summary. Symmetrical, forest-covered Santa María volcano is one of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1-km-wide crater, which formed during a catastrophic eruption in 1902 and extends from just below the summit to the lower flank. The renowned Plinian eruption of 1902 followed a long repose period and devastated much of SW Guatemala. The large dacitic Santiaguito lava-dome complex has been growing at the base of the 1902 crater since 1922. Compound dome growth at Santiaguito has occurred episodically from four westward-younging vents, accompanied by almost continuous minor explosions and periodic lava extrusion, larger explosions, pyroclastic flows, and lahars. Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html Santa María Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=1402-03= SHIVELUCH Kamchatka Peninsula, Russia 56.653°N, 161.360°E; summit elev. 3,283 m KVERT reported that seismic activity at Shiveluch was above background levels during 16-23 November. Based on seismic interpretation, ash plumes rose to an altitude of 8 km (26,200 ft) a.s.l. and hot avalanches occurred. Visual observations and video footage analysis indicated that ash plumes rose to an altitude of 4 km (13,100 ft) a.s.l. on 17, 18, and 22 November. Based on observations of satellite imagery, ash plumes drifted SE and W on 21 and 22 November and a thermal anomaly was present in the crater every day 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 5.5 km (18,000 ft) a.s.l. on 25 November. 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 Centre (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= SOPUTAN Sulawesi, Indonesia 1.11°N, 124.73°E; summit elev. 1,784 m CVGHM reported that the Alert Status of Soputan was lowered on 23 November from 3 to 2 (on a scale of 1-4) based on a decrease in the number of earthquakes and seismic intensity, deformation measurements, and visual observations. Geologic Summary. The small conical volcano of Soputan on the southern rim of the Quaternary Tondano caldera is one of Sulawesi's most active volcanoes. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924. Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/ Soputan Information from the Global Volcanism Program http://www.volcano.si.edu/world/volcano.cfm?vnum=0606-03= SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m MVO reported that during 16-23 November the lava dome at Soufrière Hills changed very little, based on visual observations. Seismic activity was very low and low-level rockfall activity continued. Fumarolic activity on the N and S flanks of the dome were observed. An overflight on 21 November revealed three fumaroles on the E side of Galways mountain. On 23 November, episodic steaming was seen from a vent located behind Gages Wall. 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 21-27 November lava-dome growth at Mount St. Helens continued. Seismicity persisted at low levels, punctuated by M 1.5-2.5, and occasionally larger, earthquakes. 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 although visual observations were limited due to cloud cover, ash-and-steam and ash plumes from Tungurahua rose to altitudes of 6-8 km (19,700-26,200 ft) a.s.l. during 21-27 November. Plumes mainly drifted W. On 21 November, lahars in S and NNW drainages were reported and reached 4-5 m high in one area. The road between Ambato and Baños was closed. Small lahars were also noted on 24 and 25 November. Roaring noises were heard on 24 and 25 November and ashfall was reported from multiple areas SW during 24-26 November. During 26-27 November, increased activity was characterized by numerous explosions that caused windows to vibrate in nearby areas. Overnight, incandescence at the crater was visible and incandescent blocks rolled about 1 km down the flanks. Steam-and-ash plumes drifted W and ashfall was reported in areas to the SW, W, and NE. 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 Significant Meteorological Information (SIGMET) advisories, the Buenos Aires VAAC reported that ash plumes from Ubinas rose to an altitude of 7.9 km (26,000 ft) a.s.l. and drifted NE on 20 November. During 24-27 November, ash plumes visible on satellite imagery rose to altitudes of 6.1-9.1 km (20,000-30,000 ft) a.s.l. and drifted NE, E, and SW. 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= +++++++++++++++++++++++++++++++++++++ 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. ==============================================================
