Thursday, October 24, 2013

[ Volcano ] Smithsonian/USGS Weekly Volcanic Activity Report 12-18 June 2013



************************************************************************************************
Smithsonian/USGS Weekly Volcanic Activity Report 12-18 June 2013

************************************************************************************************

Smithsonian/USGS Weekly Volcanic Activity Report

12-18 June 2013

 

Sally Kuhn Sennert - Weekly Report Editor

kuhns@si.edu

URL: http://www.volcano.si.edu/reports/usgs/

 

 

New Activity/Unrest: | Chirinkotan, Kuril Islands | Pavlof, Alaska Peninsula | Sangeang Api, Lesser Sunda Islands (Indonesia) | Veniaminof, Alaska Peninsula

 

Ongoing Activity: | Bagana, Bougainville | Copahue, Central Chile-Argentina border | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaii (USA) | Kizimen, Eastern Kamchatka (Russia) | Manam, Northeast of New Guinea (SW Pacific) | Popocatépetl, México | Rabaul, New Britain | Sakura-jima, Kyushu | Shiveluch, Central Kamchatka (Russia) | Soputan, Sulawesi | Tolbachik, Central Kamchatka (Russia)

 

 

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

 

 

CHIRINKOTAN Kuril Islands 48.980°N, 153.480°E; summit elev. 724 m

 

Based on analysis of satellite images, SVERT reported that dense steam-and-gas emissions, possibly containing ash, rose from Chirinkotan on 11 June. A thermal anomaly was detected on 13 June, and diffuse steam-and-gas emissions were observed on 16 June.

 

Geologic Summary. The small, mostly unvegetated 3-km-wide island of Chirinkotan occupies the far end of an E-W-trending volcanic chain that extends nearly 50 km west of the central part of the main Kuril Islands arc. Chirinkotan is the emergent summit of a volcano that rises 3000 m from the floor of the Kuril Basin. A small 1-km-wide caldera about 300-400 m deep is open to the SE. Lava flows from a cone within the breached crater reached the north shore of the island. Historical eruptions have been recorded at Chirinkotan since the 18th century. Fresh lava flows also descended the SE flank of Chirinkotan during an eruption in the 1880s that was observed by the English fur trader Captain Snow.

 

Source: Sakhalin Volcanic Eruption Response Team (SVERT) http://www.imgg.ru/en/home.html

 

 

PAVLOF Alaska Peninsula 55.42°N, 161.887°W; summit elev. 2519 m

 

AVO reported that ash emissions from Pavlof were intermittent and minor during 12-14 June; ash plumes below an altitude of 6.1 km (20,000 ft) a.s.l. mostly drifted SE. Elevated surface temperatures consistent with lava effusion persisted until 1620 on 14 June. Seismicity decreased during 14-15 June. Minor emissions likely stopped, but web-camera views were cloudy. On 17 June no plumes were visible in satellite images, and web camera views showed mostly cloudy conditions. During 17-18 June seismic tremor amplitude increased slightly, and elevated surface temperatures consistent with lava effusion were detected in satellite images. A small ash plume rose from the crater. The Volcanic Alert Level remained at Watch and the Aviation Color Code remained at Orange.

 

Geologic Summary. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavolf, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing strombolian to vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption of Pavlof took place in 1911, at the end of a 5-year-long eruptive episode; a fissure opened on the northern flank of the volcano, ejecting large blocks and issuing lava flows.

 

Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/

 

 

SANGEANG API Lesser Sunda Islands (Indonesia) 8.20°S, 119.07°E; summit elev. 1949 m

 

CVGHM reported that during May through 13 June diffuse white plumes rose 10 m above Sangeang Api's crater. Both the lava dome and surrounding areas showed no changes since November 2012. The Alert Level had been increased to 3 (on a scale of 1-4) on 19 May due to a trend of increasing seismicity; as many as 77 shallow earthquakes and 66 deep earthquakes had been detected daily. Residents and tourists were advised to stay away from the craters within a radius of 5 km. Since then seismicity decreased; 15 shallow earthquakes and three deep earthquakes were recorded on 13 June. The Alert Level was lowered to 2 on 14 June. The public were advised not to approach the craters within a radius of 1.5 km.

 

Geologic Summary. Sangeang Api volcano, one of the most active in the Lesser Sunda Islands, forms a small 13-km-wide island off the NE coast of Sumbawa Island. Two large trachybasaltic-to-tranchyandesitic volcanic cones, 1949-m-high Doro Api and 1795-m-high Doro Mantoi, were constructed in the center and on the eastern rim, respectively, of an older, largely obscured caldera. Flank vents occur on the south side of Doro Mantoi and near the northern coast. Intermittent historical eruptions have been recorded since 1512.

 

Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://proxy.vsi.esdm.go.id/

 

 

VENIAMINOF Alaska Peninsula 56.17°N, 159.38°W; summit elev. 2507 m

 

AVO reported that seismic tremor was detected at Veniaminof on 12 June. Elevated surface temperatures were detected in satellite images at 0525 on 13 June, likely indicating an intra-caldera eruption. In response, AVO raised the Volcano Alert Level to Watch and the Aviation Color code to Orange. Seismic tremor continued that day, indicative of low-level effusive activity and small explosions. At 2323 a pilot observed ash at an altitude of 3.7 km (12,000 ft) a.s.l. and a lava flow effusing from the intra-caldera cinder cone. Residents in Perryville (32 km SSE) and Port Moller (77 km WSW) also observed ash emissions at about 2330. During 15-18 June satellite images showed very high elevated surface temperatures at the intra-caldera cinder cone consistent with continued lava effusion. No plumes were observed in satellite images nor reported by pilots or local observers. Volcanic tremor continued to be detected.

 

Geologic Summary. Massive Veniaminof volcano, one of the highest and largest volcanoes on the Alaska Peninsula, is truncated by a steep-walled, 8 x 11 km, glacier-filled caldera that formed around 3,700 years ago. The caldera rim is up to 520 m high on the N, is deeply notched on the W by Cone Glacier, and is covered by an ice sheet on the S. Post-caldera vents are located along a NW-SE zone bisecting the caldera that extends 55 km from near the Bering Sea coast, across the caldera, and down the Pacific flank. Historical eruptions probably all originated from the westernmost and most prominent of two intra-caldera cones, which reaches an elevation of 2,156 m and rises about 300 m above the surrounding icefield. The other cone is larger, and has a summit crater or caldera that may reach 2.5 km in diameter, but is more subdued and barely rises above the glacier surface.

 

Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/

 

 

Ongoing Activity

 

 

BAGANA Bougainville 6.140°S, 155.195°E; summit elev. 1750 m

 

Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 17 June an ash plume from Bagana rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted over 35 km NW.

 

Geologic Summary. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. Bagana is a massive symmetrical lava cone largely constructed by an accumulation of viscous andesitic lava flows. The entire lava cone could have been constructed in about 300 years at its present rate of lava production. Eruptive activity at Bagana is characterized by non-explosive effusion of viscous lava that maintains a small lava dome in the summit crater, although explosive activity occasionally producing pyroclastic flows also occurs. Lava flows form dramatic, freshly preserved tongue-shaped lobes up to 50-m-thick with prominent levees that descend the volcano's flanks on all sides.

 

Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/

 

 

COPAHUE Central Chile-Argentina border 37.85°S, 71.17°W; summit elev. 2997 m

 

OVDAS-SERNAGEOMIN reported that during 11-12 June seismicity at Copahue had significantly decreased with respect to the previous 24-hour period; the majority of the signals were low-magnitude hybrid events, detected at an average rate of one per hour. White plumes recorded by a web camera rose at most 100 m and drifted E. Seismicity remained low during 12-13 June; an average of one event per hour continued to be detected. Meteorological cloud cover prevented views of the crater. The Alert Level remained at Orange.

 

Geologic Summary. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded at Copahue since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.

 

Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN) http://www.sernageomin.cl/index.php

 

 

KARYMSKY Eastern Kamchatka (Russia) 54.05°N, 159.45°E; summit elev. 1536 m

 

KVERT reported that technical problems prevented seismic data collection at Karymsky during 7-14 June. A thermal anomaly over the volcano was detected in satellite images during 8 and 12-13 June. The Aviation 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 12-18 June HVO reported that the circulating lava lake occasionally rose and fell in the deep pit within Kilauea's Halema'uma'u Crater. The plume from the vent continued to deposit variable amounts of ash, spatter, and Pele's hair onto nearby areas. The lake level was about 45 m below the Halema'uma'u crater floor during 14-15 and 17-18 June.

 

At Pu'u 'O'o Crater, glow emanated from three spatter cones and a small lava pond on the E part of the crater floor. The Kahauale'a II lava flows, fed by the NE spatter cone, were active as far N as 2.5 km and as far NNW as 1.9 km, and burned forest in both areas. Peace Day activity, fed by lava tubes extending from Pu'u 'O'o, consisted of some breakout activity on the pali and coastal plain, and ocean entries at locations inside and outside the National Park boundary.

 

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/

 

 

KIZIMEN Eastern Kamchatka (Russia) 55.130°N, 160.32°E; summit elev. 2376 m

 

KVERT reported that during 7-14 June moderate seismic activity continued at Kizimen. Video and satellite data showed that lava continued to extrude from the summit, producing incandescence, strong gas-and-steam activity, and hot avalanches on the W and E flanks. A thermal anomaly was detected in satellite images during 8, 10, and 12-13 June. The Aviation Color Code remained at Orange.

 

Geologic Summary. Kizimen is an isolated, conical stratovolcano that is morphologically similar to Mount St. Helens prior to its 1980 eruption. The summit of Kizimen consists of overlapping lava domes, and blocky lava flows descend the flanks of the volcano, which is the westernmost of a volcanic chain north of Kronotsky volcano. The 2,376-m-high Kizimen was formed during four eruptive cycles beginning about 12,000 years ago and lasting 2,000-3,500 years. The largest eruptions took place about 10,000 and 8300-8400 years ago, and three periods of longterm lava-dome growth have occurred. The latest eruptive cycle began about 3,000 years ago with a large explosion and was followed by lava-dome growth lasting intermittently about 1,000 years. An explosive eruption about 1,100 years ago produced a lateral blast and created a 1.0 x 0.7 km wide crater breached to the NE, inside which a small lava dome (the fourth at Kizimen) has grown. A single explosive eruption, during 1927-28, has been recorded in historical time.

 

Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php

 

 

MANAM Northeast of New Guinea (SW Pacific) 4.080°S, 145.037°E; summit elev. 1807 m

 

RVO reported that during 1-12 June activity at Manam was low, characterized by white vapor emissions from Southern Crater. On 13 June diffuse gray emissions were observed, and two explosions at midnight were heard in Bogia, 25-30 km SSW of Manam on the N coast of the mainland. During 14-15 June gray-to-brown ash plumes rose 100 m above the crater and incandescent fragment ejections from the crater were observed at night. Residents on the W part of the island heard explosions on 15 June. Diffuse brown-to-black ash clouds rose 600-700 m above the crater on 17 June, and then changed to dense white clouds later that day. Strombolian activity observed at night was accompanied by roaring, rumbling, and explosion noises. Shock waves were occasionally felt. Strombolian activity increased on 18 June, generating plumes that rose 800 m above the crater. At 0635 a small-to-moderate sized pyroclastic flow traveled down the SE valley and stopped 400 m a.s.l. Ash plumes from the pyroclastic flow rose 900 m above the crater. Roaring, rumbling, and explosion noises were accompanied by occasional shock waves. Plumes drifted NW.

 

Main Crater emitted white vapor plumes during 1-12 June. Weak but steady incandescence emanated from the crater at night on 2 and 17 June.

 

Geologic Summary. The 10-km-wide island of Manam, lying 13 km off the northern coast of mainland Papua New Guinea, is one of the country's most active volcanoes. Four large radial valleys extend from the unvegetated summit of the conical 1807-m-high basaltic-andesitic 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. Two summit craters are present; both are active, although most historical eruptions have originated from the southern crater, concentrating eruptive products during much of the past century into the SE avalanche valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded at Manam since 1616. Occasional larger eruptions have produced pyroclastic flows and lava flows that reached flat-lying coastal areas and entered the sea, sometimes impacting populated areas.

 

Source: Rabaul Volcano Observatory (RVO)

 

 

POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m

 

CENAPRED reported that during 12-18 June seismicity at Popocatépetl indicated continuing gas-and-steam emissions that sometimes contained small amounts of ash; cloud cover often prevented visual confirmation. During 12-13 June a total of about 45 minutes of low-amplitude harmonic and high frequency tremors were detected. An explosion at 1716 on 14 June produced an ash plume that rose 1.5 km above the crater. Another explosion at 1727 produced an ash plume that rose almost 3 km. The next day an explosion at 0716 generated an ash plume that rose 2 km. Explosions were also detected at 1610 and 1813.

 

During 14-17 June periods of low-amplitude harmonic tremor and high-frequency tremor continued to be detected. On 16 June an explosion at 0611 ejected incandescent tephra 500 m onto the N flank.  An explosion on 17 June produced an ash plume that rose more than 4 km, and ejected incandescent tephra up to 2 km from the crater. Some of the high-temperature fallout caused small fires in grasslands on the flanks. Ashfall was reported in Tetela del Volcán (20 km SW), Ocuituco (24 km SW), Yecapixtla (31 km SW), Atlatlahucan (30 km WSW), Cuautla (43 km SW), Tlayacapan (40 km WSW), Yautepec (50 km WSW), Jiutepec (60 km WSW), and Xochitepec (70 km WSW) in Morelos state. Ash also fell in Ecatzingo (15 km SW), Atlautla (17 km W), and Ozumba (18 km W) in México state.  The Alert Level remained at Yellow, Phase Two.

 

Source: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.gob.mx/es/

 

 

RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m

 

RVO reported that during 1-15 June white vapor plumes sometimes containing fine ash rose at most 800 m from Rabaul caldera's Tavurvur cone and drifted NW and SE. Ashfall was reported in areas downwind including Rabaul town (3-5 km NW). Roaring and rumbling noises also continued, and seismicity was low. Photographers observed a 1-m-high lava dome on the crater floor on 12 June. 

 

Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the E, where its floor is flooded by Blanche Bay. Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.

 

Source: Rabaul Volcano Observatory (RVO)

 

 

SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m

 

JMA reported that during 10-14 June Sakura-jima's Showa Crater had four explosions, ejecting tephra that fell at most 1.3 km from the crater. Crater incandescence was occasionally detected at night. One of the explosions on 13 June generated an ash plume that rose 3.3 km above the crater rim. Based on information from JMA, the Tokyo VAAC reported that on 16 June plumes rose to an altitude of 2.7 km (9,000 ft) a.s.l.

 

Geologic Summary. Sakura-jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow was associated with the formation of the 17 x 23-km-wide Aira caldera about 22,000 years ago. The construction of Sakura-jima began about 13,000 years ago and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kita-dake summit cone ended about 4,850 years ago, after which eruptions took place at Minami-dake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu's largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76.

 

Sources: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/index.html,

Tokyo Volcanic Ash Advisory Center (VAAC) http://ds.data.jma.go.jp/svd/vaac/data/vaac_list.html

 

 

SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m

 

Based on visual observations and analyses of satellite data, KVERT reported that during 7-14 June a viscous lava flow effused on the N flank of Shiveluch's lava dome, accompanied by hot avalanches, incandescence, and fumarolic activity. Satellite imagery showed a daily thermal anomaly on the lava dome. Based on notices from Yelizovo Airport (UHPP), the Tokyo VAAC reported that on 14 and 16 June ash plumes rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted E. The Aviation 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. Intermittent explosive eruptions began in the 1990s from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964.

 

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://ds.data.jma.go.jp/svd/vaac/data/vaac_list.html,

Tokyo Volcanic Ash Advisory Center (VAAC) http://ds.data.jma.go.jp/svd/vaac/data/vaac_list.html

 

 

SOPUTAN Sulawesi 1.108°N, 124.73°E; summit elev. 1784 m

 

On 14 June CVGHM reported that, after the Alert Level at Soputan was raised to 3 (on a scale of 1-4) on 19 April due to a trend of increased seismicity, the number of various types of earthquakes decreased, except for events signaling avalanches, which fluctuated during the period. No changes were observed in emissions; white plumes continued to rise at most 50 m above the crater. On 14 June the Alert Level was lowered to 2. Residents and tourists were advised not to approach the craters within a radius of 4 km.

 

Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://www.vsi.esdm.go.id/

 

 

TOLBACHIK Central Kamchatka (Russia) 55.830°N, 160.330°E; summit elev. 3682 m

 

KVERT reported that the S fissure along the W side of Tolbachinsky Dol, a lava plateau on the SW side of Tolbachik, continued to produce very fluid lava flows during 7-14 June that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure and weak gas-and-steam plumes were observed. A large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. The Aviation Color Code remained at Orange.

 

Geologic Summary. The massive Tolbachik basaltic volcano is located at the southern end of the dominantly andesitic Kliuchevskaya volcano group. The Tolbachik massif is composed of two overlapping, but morphologically dissimilar volcanoes. The flat-topped Plosky Tolbachik shield volcano with its nested Holocene Hawaiian-type calderas up to 3 km in diameter is located east of the older and higher sharp-topped Ostry Tolbachik stratovolcano. The summit caldera at Plosky Tolbachik was formed in association with major lava effusion about 6500 years ago and simultaneously with a major southward-directed sector collapse of Ostry Tolbachik volcano. Lengthy rift zones extending NE and SSW of the volcano have erupted voluminous basaltic lava flows during the Holocene, with activity during the past two thousand years being confined to the narrow axial zone of the rifts. The 1975-76 eruption originating from the SSW-flank fissure system and the summit was the largest historical basaltic eruption in Kamchatka.

 

Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php

 

 

+++++++++++++++++++++++++++++++++++++

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




__._,_.___


[ Volcano ]





Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe

__,_._,___

No comments:

Post a Comment