Smithsonian/USGS Weekly Volcanic Activity Report 10-16 April 2013
From: "Kuhn, Sally" <KUHNS@xxxxxx>
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Smithsonian/USGS Weekly Volcanic Activity Report
10-16 April 2013
Sally Kuhn Sennert - Weekly Report Editor
URL: http://www.volcano.si.edu/reports/usgs/
New Activity/Unrest: | Galeras, Colombia | Nevado del Ruiz, Colombia
Ongoing Activity: | Bagana, Bougainville | Batu Tara, Komba Island (Indonesia) | Chirpoi, Kuril Islands (Russia) | Etna, Sicily (Italy) | Kilauea, Hawaii (USA) | Kizimen, Eastern Kamchatka (Russia) | Lokon-Empung, Sulawesi | Manam, Northeast of New Guinea (SW Pacific) | Paluweh, Lesser Sunda Islands (Indonesia) | Popocatépetl, México | Rabaul, New Britain | Reventador, Ecuador | Sakura-jima, Kyushu | Sangay, Ecuador | Shiveluch, Central Kamchatka (Russia) | 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
GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m
INGEOMINAS reported that during 10-16 April earthquakes at Galeras were located in various areas as far as 13 km from the crater, at depths no greater than 14 km and with maximum magnitudes of 2. Moderate levels of sulfur dioxide were detected; plumes drifted NW. Cameras recorded ash emissions all week, especially on 9, 11, 12, and 14 April, when pulsating activity produced plumes that drifted W. Plumes rose no more than 1 km above the crater. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").
Geologic Summary. Galeras, a stratovolcano with a large breached caldera located immediately W of the city of Pasto, is one of Colombia's most frequently active volcanoes. The dominantly andesitic Galeras volcanic complex has been active for more than 1 million years, and two major caldera collapse eruptions took place during the late Pleistocene. Longterm extensive hydrothermal alteration has affected the volcano. This has contributed to large-scale edifice collapse that has occurred on at least three occasions, producing debris avalanches that swept to the W and left a large horseshoe-shaped caldera inside which the modern cone has been constructed. Major explosive eruptions since the mid Holocene have produced widespread tephra deposits and pyroclastic flows that swept all but the southern flanks. A central cone slightly lower than the caldera rim has been the site of numerous small-to-moderate historical eruptions since the time of the Spanish conquistadors.
Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co/
NEVADO DEL RUIZ Colombia 4.895°N, 75.322°W; summit elev. 5321 m
INGEOMINAS reported that during 13-14 April seismicity associated with fluid movement beneath Nevado del Ruiz was detected along with volcano-tectonic earthquakes. The earthquakes were located NW of Arenas Crater at depths between 5 and 9 km; the largest was a M 2.6, felt by officials of Los Nevados National Park in the area of Brisas (50 km SW). During the early morning of 14 April webcams recorded a gas-and-ash plume that rose 630 m and drifted NW. On 15 April a M 3 volcano-tectonic earthquake was located NW of Arenas Crater at a depth of 6.6 km. Later that day a M 2.5 volcano-tectonic earthquake was located again NW of Arenas Crater at a depth of 5.78 km. On 16 April at 0714 a M 3.2 earthquake was located in the same area at a depth of 6.22 km. Earthquakes continued to be felt by officials in the National Park. A gas-and-steam plume rose 1 km above the crater and drifted SW. Sulfur dioxide emissions were significant and deformation was detected. The Alert Level remained at III (Yellow; "changes in the behavior of volcanic activity").
Geologic Summary. Nevado del Ruiz is a broad, glacier-covered volcano in central Colombia that covers >200 sq km. Three major edifices, composed of andesitic and dacitic lavas and andesitic pyroclastics, have been constructed since the beginning of the Pleistocene. The modern cone consists of a broad cluster of lava domes built within the summit caldera of an older Ruiz volcano. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. Steep headwalls of massive landslides cut the flanks of Nevado del Ruiz. Melting of its summit icecap during historical eruptions, which date back to the 16th century, has resulted in devastating lahars, including one in 1985 that was South America's deadliest eruption.
Source: Instituto Colombiano de Geología y Minería (INGEOMINAS) http://www.ingeominas.gov.co/
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 during 10-11 April ash plumes from Bagana rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 75 km SW and W. On 15 April an ash plume rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted almost 30 km S and W. The next day ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 65 km SW.
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/
BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m
Based on analyses of satellite imagery and wind data, the Darwin Volcanic Ash Advisory Centre (VAAC) reported that during 13-16 April ash plumes from Batu Tara rose to altitudes of 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted 25-45 km NW, N, NE, and SE.
Geologic Summary. The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks of Batu Tara to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
CHIRPOI Kuril Islands (Russia) 46.525°N, 150.875°E; summit elev. 742 m
SVERT reported that a weak thermal anomaly over Snow, a volcano of Chirpoi, was detected in satellite images during 12-13 April; cloud cover prevented observations of the volcano on other days during 8-15 April.
Geologic Summary. Chirpoi, a small island lying between the larger islands of Simushir and Urup, contains a half dozen volcanic edifices constructed within an 8-9 km wide, partially submerged caldera. The southern rim of the caldera is exposed on nearby Brat Chirpoev Island. Two volcanoes on Chirpoi Island have been historically active. The symmetrical Cherny volcano, which forms the 691 m high point of the island, erupted twice during the 18th and 19th centuries. The youngest volcano, Snow, originated between 1770 and 1810. It is composed almost entirely of lava flows, many of which have reached the sea on the southern coast. No historical eruptions are known from 742-m-high Brat Chirpoev, but its youthful morphology suggests recent strombolian activity.
Source: Sakhalin Volcanic Eruption Response Team (SVERT) http://www.imgg.ru/en/home.html
ETNA Sicily (Italy) 37.734°N, 15.004°E; summit elev. 3330 m
Sezione di Catania - Osservatorio Etneo reported that the tenth eruptive episode of 2013 began at Etna's New Southeast Crater (NSEC) on 8 April with sporadic ash emissions occasionally accompanied by incandescent material. A large explosion at 2252 was heard up to 15 km away. The ash emissions continued for about 48 hours. In the late afternoon on 10 April Strombolian activity began, producing minor ash emissions during some of the explosions. In the morning on 11 April Strombolian explosions occurred about every 2-5 seconds, ejecting incandescent pyroclastics several tens of meters above the crater rim. Strombolian activity increased slowly in intensity and frequency of explosions throughout the day; contemporaneously the volcanic tremor amplitude continued to show a gradual rise. Late in the afternoon frequent and very powerful Strombolian explosions occurred every 1-2 seconds and were widely audible around the volcano. Jets of incandescent pyroclastics often rose 200 m above the crater rim and generally contained minor amounts of ash. Around 1840, a small amount of lava flowed over the deep breach in the SE rim of the crater. In the late evening it stopped and showed evidence of cooling.
Around 0110 on 12 April another small lava flow traveled S then SE from the saddle between the two cones of the Southeast Crater (SEC). Throughout the night powerful explosions alternated with intermittent, low lava fountains. At daybreak on 12 April a dense eruption plume containing relatively minor amounts of pyroclastic material drifted ESE. Until about 1025 on 12 April, all eruptive activity occurred exclusively at one or two closely spaced vents within the NSEC, then lava was emitted from two vents at the NE base of the NSEC cone. At 1024 a flow of hot pyroclastic material from the same area traveled about 2 km NE in less than 1 minute.
In the meantime, eruptive activity continued at the NSEC with frequent, powerful Strombolian explosions and emission of modest quantities of volcanic ash, which was rapidly dispersed. Lava emission from the SSE rim of the NSEC, the saddle, and the NE base of the cone remained active. Shortly before 1200, the eruptive activity changed from low lava fountains to Strombolian explosions and intermittent ash emissions. Vigorous ash emissions resumed at 1214 both from the main vent of the NSEC and from the saddle vent. Expulsion of blocks, bombs and ash from the saddle vent continued until 1234, when the main vent of the NSEC reactivated, and for the next nearly 20 minutes both vents were the source intense ash emissions.
The activity shifted back entirely to NSEC, entering into the true paroxysmal phase of this episode at 1250 with sustained lava fountaining, accompanied by a return to high levels of the volcanic tremor amplitude. During the following 10 minutes, there was a considerable increase in the quantity of pyroclastic material in the plume, which drifted ESE. Tephra fall (ash and small lapilli) affected Fleri, Zafferana Etnea, Milo and S. Maria la Scala, although the quantity of fallout was much smaller compared to those of the previous paroxysms. Sustained lava fountaining continued for about one hour; a few minutes after 1400 the activity switched to sporadic Strombolian explosions and ash emissions, which gradually diminished in vigor. During 1400 and 1410, repeated collapses occurred on the SE flank of the NSEC cone, possibly from new vents at the base of the cone, from which a new lava flow traveled toward the Valle del Bove. The collapses generated avalanches and clouds ash. Explosive activity progressively diminished and completely ceased around 1700.
On the evening of 12 April, the lava flows emitted from the saddle and from the various vents on the flanks of the cone were incandescent and slowly moving; during the night, the surveillance cameras showed the cessation of all lava emission and the cooling of the flows. However, on the morning of 13 April, slow lava effusion resumed from the lower of the vents and a small flow advanced a few hundred meters. This flow ceased in the early morning hours the following day. Once more, on the evening of 14 April, there was a rather weak resumption of effusive activity from this vent, which ceased after a few hours.
Geologic Summary. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BC. Historical lava flows cover much of the surface of this massive basaltic stratovolcano, the highest and most voluminous in Italy. Two styles of eruptive activity typically occur at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater. Flank eruptions, typically with higher effusion rates, occur less frequently and originate from fissures that open progressively downward from near the summit. A period of more intense intermittent explosive eruptions from Etna's summit craters began in 1995. The active volcano is monitored by the Instituto Nazionale di Geofisica e Volcanologia (INGV) in Catania.
Source: Sezione di Catania - Osservatorio Etneo www.ct.ingv.it/
KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m
During 10-16 April HVO reported that the circulating lava lake periodically 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.
At Pu'u 'O'o Crater, glow emanated from four spatter cones on the crater floor. Two lava flows (Peace Day and Kahauale'a) were fed by lava tubes extending from Pu'u 'O'o. Multiple lava flows from the NE spatter cone, collectively called the Kahauale'a flow, traveled across the NE flank of Pu'u 'O'o cone to the cone's base and advanced more than 4.9 km NE over older flows. Peace Day activity consisted of lava flows active above the pali (5 km SE of Pu'u 'O'o), on the pali, and on the coastal plain. Lava also entered the ocean at two main locations spanning 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 5-12 April 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. Satellite images detected a daily thermal anomaly over the volcano. 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
LOKON-EMPUNG Sulawesi 1.358°N, 124.792°E; summit elev. 1580 m
Based on both web-camera views and ground reports, the Darwin VAAC reported that on 11 April an ash plume from Lokon-Empung rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted SW. Ash was not detected in satellite imagery.
Geologic Summary. The twin volcanoes Lokon and Empung, rising about 800 m above the plain of Tondano, are among the most active volcanoes of Sulawesi. Lokon, the higher of the two peaks (whose summits are only 2.2 km apart) has a flat, craterless top. The morphologically younger Empung volcano has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century, but all subsequent eruptions have originated from Tompaluan, a 150 x 250 m wide double crater situated in the saddle between the two peaks. Historical eruptions have primarily produced small-to-moderate ash plumes that have occasionally damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
MANAM Northeast of New Guinea (SW Pacific) 4.080°S, 145.037°E; summit elev. 1807 m
RVO reported that during 1-14 April Strombolian activity was observed from Manam Southern Crater. During 1-7 April ash plumes rose above the crater. Island residents reported incandescent tepha ejections from the crater at night, and roaring and rumbling noises. Activity increased on 8 April. Strombolian activity was sustained for extended periods during 9-11 and 13-14 April. Loud roaring and rumbling noises were reported by residents in Bogia, 25-30 km SSW of Manam on the N coast of the mainland. A few loud banging noises on 13 April rattled bush-material houses at Dugulava village on the SW side of the island. Most fragments from the Strombolian eruptions, including a small volume of lava, were channeled into SW valley. Ash plumes rose as high as 600 m above the summit crater and drifted NW. White vapor plumes rose from Main Crater during the reporting period.
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)
PALUWEH Lesser Sunda Islands (Indonesia) 8.32°S, 121.708°E; summit elev. 875 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 16 April an ash plume from Paluweh rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 37 km E.
Geologic Summary. Paluweh volcano, also known as Rokatenda, forms the 8-km-wide island of Paluweh N of the volcanic arc that cuts across Flores Island. Although the volcano rises about 3,000 m above the sea floor, its summit reaches only 875 m above sea level. The broad irregular summit region contains overlapping craters up to 900 m wide and several lava domes. Several flank vents occur along a NW-trending fissure. The largest historical eruption of Paluweh occurred in 1928, when a strong explosive eruption was accompanied by landslide-induced tsunamis and lava-dome emplacement.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m
CENAPRED reported that during 10-16 April seismicity at Popocatépetl indicated continuing gas-and-steam emissions that sometimes contained ash. Incandescence from the crater was observed at night and sometimes increased in conjunction with emissions. On 10 April gas-and-steam plumes rose 800 m above the crater and drifted ESE, and ash plumes rose 900 m and also drifted ESE. During 11-13 April gas-and-ash plumes rose 500 m and drifted NE. An explosion on 13 April produced a steam-and-ash plume that rose 400 m and drifted NE. Ashfall was reported in the towns of San Nicolas de los Ranchos (15 km ENE) and Huejotzingo (27 km NE), and in the northern part of Puebla (40 km E). On 14 April a period of tremor was accompanied by continuous emissions of dense steam-and-gas plumes with small amounts of ash that rose as high as 1 km and drifted NE. The next day ash plumes rose 1.5 km above the crater, and incandescent tephra ejected from the crater landed 400 m away on the NE flank. On 16 April gas-and-steam plumes rose 1 km and drifted NE. The Alert Level remained at Yellow, Phase Two.
Geologic Summary. Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5,426 m 70 km SE of Mexico City and is North America's second-highest volcano. Frequent historical eruptions have been recorded since the beginning of the Spanish colonial era. A small eruption on 21 December 1994 ended five decades of quiescence. Since 1996 small lava domes have incrementally been constructed within the summit crater and destroyed by explosive eruptions. Intermittent small-to-moderate gas-and-ash eruptions have continued, occasionally producing ashfall in neighboring towns and villages.
Source: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.gob.mx/es/
RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m
RVO reported that roaring and rumbling noises from Rabaul were heard during 1-14 April, especially at night. White vapor plumes with ash rose at most 100 m above the main crater and drifted NW, causing ashfall in Rabaul town (3-5 km NW).
Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the E, where its floor is flooded by Blanche Bay. Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.
Source: Rabaul Volcano Observatory (RVO)
REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m
According to the Washington VAAC, on 12 April an ash plume from Reventador was observed in visible satellite images along with a corresponding thermal anomaly in short wave infrared images.
Geologic Summary. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well E of the principal volcanic axis. It is a forested stratovolcano that rises above the remote jungles of the western Amazon basin. A 3-km-wide caldera breached to the E was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1,300 m above the caldera floor. Reventador has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera.
Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html
SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m
JMA reported that occasional very small eruptions from Sakura-jima's Showa Crater occurred during 8-12 April. Crater incandescence was detected at night. Based on information from JMA, the Tokyo VAAC reported that on 13 April an eruption produced an ash plume that rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted SE.
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
SANGAY Ecuador 2.002°S, 78.341°W; summit elev. 5230 m
Based on analyses of satellite imagery, the Washington VAAC reported that on 11 April an ash plume from Sangay drifted W.
Geologic Summary. The isolated Sangay volcano, located E of the Andean crest, is the southernmost of Ecuador's volcanoes, and its most active. It has been in frequent eruption for the past several centuries. The steep-sided, 5,230-m-high glacier-covered volcano grew within horseshoe-shaped calderas of two previous edifices, which were destroyed by collapse to the E, producing large debris avalanches that reached the Amazonian lowlands. The modern edifice dates back to at least 14,000 years ago. Sangay towers above the tropical jungle on the E side; on the other sides flat plains of ash from the volcano have been sculpted by heavy rains into steep-walled canyons up to 600 m deep. The earliest report of an historical eruption was in 1628. More or less continuous eruptions were reported from 1728 until 1916, and again from 1934 to the present. The more or less constant eruptive activity has caused frequent changes to the morphology of the summit crater complex.
Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.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 5-12 April a viscous lava flow effused on the E 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. 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
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 5-12 April that traveled to the W, S, and E sides of the plateau. Cinder cones continued to grow along the S fissure. Gas-and-ash plumes rose to an altitude of 3.5 km (11,500 ft) a.s.l. and drifted in multiple directions. A very large thermal anomaly on the N part of Tolbachinsky Dol was visible daily in satellite imagery. A weak thermal anomaly was detected over the crater of the volcano on 6 and 9 April. 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
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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
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