Smithsonian / USGS Weekly Volcanic Activity Report 17 September-23 September 2014
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Smithsonian / USGS Weekly Volcanic Activity Report
17 September-23 September 2014
Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx)
URL: http://www.volcano.si.edu/reports_weekly.cfm
New Activity/Unrest: Bardarbunga, Iceland | Mayon, Luzon (Philippines) | Rabaul, New Britian (Papua New Guinea) | Rincon de la Vieja, Costa Rica | Sheveluch, Central Kamchatka (Russia) | Slamet, Central Java (Indonesia)
Ongoing Activity: Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Dukono, Halmahera (Indonesia) | Karangetang [Api Siau], Siau Island (Indonesia) | Kilauea, Hawaiian Islands (USA) | Kuchinoerabujima, Ryukyu Islands (Japan) | Lokon-Empung, Sulawesi (Indonesia) | Reventador, Ecuador | Shishaldin, Fox Islands (USA) | Sinabung, Indonesia | Tungurahua, Ecuador | Zhupanovsky, Eastern 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
Bardarbunga | Iceland | 64.63°N, 17.53°W | Summit elev. 2009 m
During 17-23 September, IMO maintained Aviation Colour Code Orange due to continued activity at Bárdarbunga’s Holuhraun eruptive fissure. Chemical analysis and geophysical modeling indicated that the source of the magma was at a depth of more than 10 km. Persistent subsidence was detected from the Bárdarbunga caldera and crustal movements signified that the volume of magma in the dyke slightly increased. On 21 September the lava field measured 37 square kilometers. Field scientists estimated that about 90% of the sulfur dioxide gas from the eruption originated at the active craters and the rest rose from the lava field. Dead birds were also found around the eruption site. A report on 22 September noted that the total volume of the erupted lava was 0.4-0.6 cubic kilometers and the flow rate was 250-350 cubic meters per second. Persistent subsidence was detected from the Bárdarbunga caldera; the volume of the depression was an estimated 0.6 cubic kilometers on 23 September.
Geologic Summary. The large central volcano of Bárdarbunga lies beneath the NW part of the Vatnajökull icecap, NW of Grímsvötn volcano, and contains a subglacial 700-m-deep caldera. Related fissure systems include the Veidivötn and Trollagigar fissures, which extend about 100 km SW to near Torfajökull volcano and 50 km NE to near Askja volcano, respectively. Voluminous fissure eruptions, including one at Thjorsarhraun, which produced the largest known Holocene lava flow on Earth with a volume of more than 21 cu km, have occurred throughout the Holocene into historical time from the Veidivötn fissure system. The last major eruption of Veidivötn, in 1477, also produced a large tephra deposit. The subglacial Loki-Fögrufjöll volcanic system located SW of Bárdarbunga volcano is also part of the Bárdarbunga volcanic system and contains two subglacial ridges extending from the largely subglacial Hamarinn central volcano; the Loki ridge trends to the NE and the Fögrufjöll ridge to the SW. Jökulhlaups (glacier-outburst floods) from eruptions at Bárdarbunga potentially affect drainages in all directions.
Source: Icelandic Met Office http://en.vedur.is/
Mayon | Luzon (Philippines) | 13.257°N, 123.685°E | Summit elev. 2462 m
PHIVOLCS reported that during 16-17 September the seismic network at Mayon recorded 38 volcanic earthquakes and 277 rockfall events. Bright incandescence from the crater was visible at night, and rolling incandescent rocks in the uppermost part of Bonga Gully indicated that the lava dome was breaching the SE part of the crater. The Alert Level was raised to 3 (on a 0-5 scale). PHIVOLCS recommended enforcement of the 6-km radius Permanent Danger Zone (PDZ) around the volcano and the 7-km Extended Danger Zone (EDZ) on the SE flank. On 17 September a news article indicated that almost 24,000 people from villages within an 8-km radius from the crater had been evacuated.
During 17-18 September the network recorded 142 volcanic earthquakes and 251 rockfall events. Although rain clouds prevented visual observations of the crater, white steam plumes drifting SSW were noted. The network recorded 38 volcanic earthquakes and 277 rockfall events during 18-19 September; cloud cover prevented visual observations. During 19-21 September four volcanic earthquakes along with 8-22 rockfall events per day were recorded. White steam plumes drifted ENE and NNE during 20-21 September. During 21-23 September three volcanic earthquakes per day and 13-18 rockfall events per day were recorded; white steam plumes drifted NNE, NE, ENE, and SW.
Geologic Summary. Beautifully symmetrical Mayon volcano, which rises to 2462 m above the Albay Gulf, is the Philippines' most active volcano. The structurally simple volcano has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. Historical eruptions at this basaltic-andesitic volcano date back to 1616 and range from strombolian to basaltic plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. Eruptions occur predominately from the central conduit and have also produced lava flows that travel far down the flanks. Pyroclastic flows and mudflows have commonly swept down many of the approximately 40 ravines that radiate from the summit and have often devastated populated lowland areas. Mayon's most violent eruption, in 1814, killed more than 1200 people and devastated several towns.
Sources: Philippine Institute of Volcanology and Seismology (PHIVOLCS) http://www.phivolcs.dost.gov.ph/;
Associated Press http://news.yahoo.com/philippine-volcano-spews-lava-thousands-evacuated-100604624.html
Rabaul | New Britian (Papua New Guinea) | 4.271°S, 152.203°E | Summit elev. 688 m
RVO reported that Rabaul caldera's Tavurvur cone was mostly quiet during 13-19 September. Variable amounts of white vapor and small amounts of diffuse blue vapor rose from the summit crater. A small explosion at 1242 on 18 September produced a light gray ash plume that rose a few hundred meters above the crater and drifted 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 utilized by what was the island's largest city prior to a major eruption in 1994. 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 east, where its floor is flooded by Blanche Bay and was formed about 1400 years ago. An earlier caldera-forming eruption about 7100 years ago is now considered to have originated from Tavui caldera, offshore to the north. 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)
Rincon de la Vieja | Costa Rica | 10.83°N, 85.324°W | Summit elev. 1916 m
OVSICORI-UNA reported that at 1237 on 17 September a seismic signal indicating a phreatic explosion at Rincón de la Vieja was detected by a station about 5 km S of the volcano. A second phreatic explosion, detected at 2048 and lasting three minutes, was of a larger magnitude and a longer duration that the first explosion. Phreatic explosions were also detected at 1825 on 19 September and at 0304, 0439, and 0634 on 20 September. Residents on the N flank heard the event on 19 September and saw the explosion at 0634 on 20 September. An overflight of the crater lake on 20 September revealed that the temperature of the lake water was about 45 degrees Celsius, an increase from about 30 degrees measured in April.
Geologic Summary. Rincón de la Vieja, the largest volcano in NW Costa Rica, is a remote volcanic complex in the Guanacaste Range. The volcano consists of an elongated, arcuate NW-SE-trending ridge that was constructed within the 15-km-wide early Pleistocene Guachipelín caldera, whose rim is exposed on the south side. Rincón de la Vieja, sometimes known as the "Colossus of Guanacaste," has an estimated volume of 130 cu km and contains at least 9 major eruptive centers. Activity has migrated to the SE, where the youngest-looking craters are located. The twin cone of 1916-m-high Santa María volcano, the highest peak of the Rincón complex, is located at the eastern end of a smaller, 5-km-wide caldera and has a 500-m-wide crater. A plinian eruption producing the 0.25 cu km Río Blanca tephra about 3500 years ago was the last major magmatic eruption from the volcano. All subsequent eruptions, including numerous historical eruptions possibly dating back to the 16th century, have been from the prominent crater containing a 500-m-wide acid lake (known as the Active Crater) located ENE of Von Seebach crater.
Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/
Sheveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit elev. 3283 m
KVERT reported that during 12-19 September lava-dome extrusion onto Shiveluch’s N flank was accompanied by ash explosions, incandescence, hot avalanches, and fumarolic activity. Satellite images detected a daily thermal anomaly over the dome. On 14 September a video camera recorded a short-duration explosion which produced an ash plume that rose 6 km (19,700 ft) a.s.l.; strong gas-and-steam activity was noted afterwards. On 24 September explosions generated ash plumes that rose 11 km (36,000 ft) a.s.l. and drifted N. Ash plumes also drifted E at an altitude of 5 km (16,400 ft) a.s.l. The Aviation Color Code was raised to Red.
Geologic Summary. The high, isolated massif of Sheveluch volcano (also spelled Shiveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 cu km volcano is one of Kamchatka's largest and most active volcanic structures. The summit of roughly 65,000-year-old Stary Shiveluch is truncated by a broad 9-km-wide late-Pleistocene caldera breached to the south. Many lava domes dot its outer flanks. The Molodoy Shiveluch lava dome complex was constructed during the Holocene within the large horseshoe-shaped caldera; Holocene lava dome extrusion also took place on the flanks of Stary Shiveluch. At least 60 large eruptions have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
Slamet | Central Java (Indonesia) | 7.242°S, 109.208°E | Summit elev. 3428 m
PVMBG reported that during 13-16 September white plumes rose 50-200 m above Slamet's crater. An explosion on 17 September produced a dense blackish-gray ash plume that rose as high as 1.2 km and drifted S and SW. Incandescent material was ejected 200-500 m high and booming noises were reported. Ash fell in areas as far as 20 km S. Although white plumes mostly rose from the crater the next day, an explosion generated an ash plume that rose 500 m and drifted W. During 19-20 September white plumes rose 100 m. The Alert Level remained at 3 (on a scale of 1-4).
Geologic Summary. Slamet, Java's second highest volcano at 3428 m and one of its most active, has a cluster of about three dozen cinder cones on its lower SE-NE flanks and a single cinder cone on the western flank. It is composed of two overlapping edifices, an older basaltic-andesite to andesitic volcano on the west and a younger basaltic to basaltic-andesite one on the east. Gunung Malang II cinder cone on the upper E flank on the younger edifice fed a lava flow that extends 6 km E. Four craters occur at the summit of Gunung Slamet, with activity migrating to the SW over time. Historical eruptions, recorded since the 18th century, have originated from a 150-m-deep, 450-m-wide, steep-walled crater at the western part of the summit and have consisted of explosive eruptions generally lasting a few days to a few weeks.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://www.vsi.esdm.go.id/
Ongoing Activity
Aira | Kyushu (Japan) | 31.593°N, 130.657°E | Summit elev. 1117 m
JMA reported that 24 explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 1,300 m during 16-19 September. The Alert Level remained at 3 (on a scale of 1-5). The Tokyo VAAC reported that during 17-23 September plumes rose to altitudes of 1.8-3.4 km (6,000-11,000 ft) a.s.l. and drifted in multiple directions. During 17-18 and 23 September pilots observed ash plumes that rose to altitudes of 2-3 km (7,000-10,000 ft) a.s.l.
Geologic Summary. The Aira caldera in the northern half of Kagoshima Bay contains the post-caldera Sakurajima volcano, one of Japan's most active. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakurajima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kitadake summit cone ended about 4850 years ago, after which eruptions took place at Minamidake. 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/;
Tokyo Volcanic Ash Advisory Center (VAAC) http://ds.data.jma.go.jp/svd/vaac/data/vaac_list.html
Bagana | Bougainville (Papua New Guinea) | 6.137°S, 155.196°E | Summit elev. 1855 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 21 September an ash plume from Bagana rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 55 km W.
Geologic Summary. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. This massive symmetrical, roughly 1850-m-high cone was largely constructed by an accumulation of viscous andesitic lava flows. The entire edifice could have been constructed in about 300 years at its present rate of lava production. Eruptive activity is frequent and 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. Satellite thermal measurements indicate a continuous eruption from before February 2000 through at least late August 2014.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
Dukono | Halmahera (Indonesia) | 1.68°N, 127.88°E | Summit elev. 1335 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 16 and 18 September ash plumes from Dukono rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 35-65 km E and NE.
Geologic Summary. Reports from this remote volcano in northernmost Halmahera are rare, but Dukono has been one of Indonesia's most active volcanoes. More-or-less continuous explosive eruptions, sometimes accompanied by lava flows, occurred from 1933 until at least the mid-1990s, when routine observations were curtailed. During a major eruption in 1550, a lava flow filled in the strait between Halmahera and the north-flank cone of Gunung Mamuya. Dukono is a complex volcano presenting a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of Dukono's summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
Karangetang [Api Siau] | Siau Island (Indonesia) | 2.78°N, 125.4°E | Summit elev. 1784 m
PVMBG reported that although Karangetang was often covered in fog during 7-14 September, observers occasionally noted white plumes rising at most 150 m from the main crater and Crater II. Incandescence from the lava dome was observed at night. Seismicity remained high and was dominated by shallow earthquakes from lava-dome growth and avalanches. The Alert Level remained at 3 (on a scale of 1-4).
Geologic Summary. Karangetang (Api Siau) volcano lies at the northern end of the island of Siau, north of Sulawesi. The 1784-m-high stratovolcano contains five summit craters along a N-S line. Karangetang is one of Indonesia's most active volcanoes, with more than 40 eruptions recorded since 1675 and many additional small eruptions that were not documented in the historical record (Catalog of Active Volcanoes of the World: Neumann van Padang, 1951). Twentieth-century eruptions have included frequent explosive activity sometimes accompanied by pyroclastic flows and lahars. Lava dome growth has occurred in the summit craters; collapse of lava flow fronts has also produced pyroclastic flows.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://www.vsi.esdm.go.id/
Kilauea | Hawaiian Islands (USA) | 19.421°N, 155.287°W | Summit elev. 1222 m
During 17-23 September HVO reported that the circulating lava lake occasionally rose and fell in the deep pit within Kilauea's Halema'uma'u Crater. Gas emissions remained elevated. The plume from the vent continued to deposit variable amounts of ash, spatter, and Pele's hair onto nearby areas; smaller particles may have been dropped several kilometers away. At Pu'u 'O'o Crater, glow emanated from several outgassing openings in the crater floor. Two small lava ponds in the S pit were visible during the earlier part of the week, and small breakout flows near the crater burned adjacent forest.
The NE-trending lava flow had advanced at an average rate of 290 m/day between 15 and 17 September and 190 m/day between 17 and 19 September, and continued to cause localized fires as it spread through the forest. By 22 September the flow extended 16.4 km from the vent (measured in a straight line), placing the active flow front within the NW portion of the Kaohe Homesteads, a vacant forested portion of the subdivision. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Warning.
Geologic Summary. Kilauea volcano, which overlaps the east flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions of Kilauea are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 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/
Kuchinoerabujima | Ryukyu Islands (Japan) | 30.443°N, 130.217°E | Summit elev. 657 m
JMA reported that no eruptions occurred from Kuchinoerabujima during 16-19 September. White plumes rose 600 m above the crater. Low-level seismicity continued and tremor was absent. The Alert Level remained at 3 (on a scale of 1-5).
Geologic Summary. A group of young stratovolcanoes forms the eastern end of the irregularly shaped island of Kuchinoerabujima in the northern Ryukyus, 15 km west of Yakushima. Furutake, Shintake, and Noike were erupted from south to north, respectively, to form a composite cone that is parallel to the trend of the Ryukyu Islands. The highest peak, Furutake, reaches only 657 m above sea level. The youngest cone, 640-m-high Shintake, was formed after the NW side of Furutake was breached by an explosion. All historical eruptions have occurred from Shintake, although a lava flow from the S flank of Furutake that reached the coast has a very fresh morphology. Frequent explosive eruptions have taken place from Shintake since 1840; the largest of these was in December 1933. Several villages on the 4 x 12 km island are located within a few kilometers of the active crater and have suffered damage from eruptions.
Source: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/
Lokon-Empung | Sulawesi (Indonesia) | 1.358°N, 124.792°E | Summit elev. 1580 m
PVMBG reported that during 8-14 September observers of Lokon-Empung noted white plumes rising 25-100 m above Tompaluan Crater. On 13 September three explosions from Tompaluan Crater, at 0300, 1146, and 1229, produced white plumes that rose at most 500 m above the crater. Seismicity decreased sharply after the13 September events but continued to remain high relative to the levels detected prior to 10 September. The Alert Level remained at 3 (on a scale of 1-4).
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: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://www.vsi.esdm.go.id/
Reventador | Ecuador | 0.077°S, 77.656°W | Summit elev. 3562 m
IG reported that vapor plumes with a low ash content rose 1-2 km above Reventador and drifted NW and SW during 17-22 September.
Geologic Summary. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. It 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. The largest historical eruption took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.
Source: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/
Shishaldin | Fox Islands (USA) | 54.756°N, 163.97°W | Summit elev. 2857 m
AVO reported that, although cloud cover sometimes obscured views of Shishaldin during 17-22 September, seismicity indicated that a low-level eruption was possibly continuing. Elevated surface temperatures at the summit were periodically detected in satellite images. Minor steam emissions were recorded by the web cam on 17 September. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geologic Summary. The beautifully symmetrical volcano of Shishaldin is the highest and one of the most active volcanoes of the Aleutian Islands. The 2857-m-high, glacier-covered volcano is the westernmost of three large stratovolcanoes along an E-W line in the eastern half of Unimak Island. The Aleuts named the volcano Sisquk, meaning "mountain which points the way when I am lost." A steady steam plume rises from its small summit crater. Constructed atop an older glacially dissected volcano, it is Holocene in age and largely basaltic in composition. Remnants of an older ancestral volcano are exposed on the west and NE sides at 1500-1800 m elevation. There are over two dozen pyroclastic cones on its NW flank, which is blanketed by massive aa lava flows. Frequent explosive activity, primarily consisting of strombolian ash eruptions from the small summit crater, but sometimes producing lava flows, has been recorded since the 18th century.
Source: US Geological Survey Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/
Sinabung | Indonesia | 3.17°N, 98.392°E | Summit elev. 2460 m
PVMBG reported that RSAM values from Sinabung were low and stable during 12-20 September. Earthquake signals indicating lava-dome instability were recorded and had increased from 96 to 110 events/day since the 5-11 September period. Seismicity also continued to signify growth of the main lava flow on the flanks; incandescent lava was visible at the top, middle, and front of the lava flow. The length of the lava flow was 2.9 km on 6 September. White and sometimes bluish plumes rose as high as 1 km above the lava dome. Pyroclastic flows traveled 2.5 km SE on 15 September and 2 km S on 18 September. The Alert Level remained at 3 (on a scale of 1-4).
Geologic Summary. Gunung Sinabung is a Pleistocene-to-Holocene stratovolcano with many lava flows on its flanks. The migration of summit vents along a N-S line gives the summit crater complex an elongated form. The youngest crater of this conical, 2460-m-high andesitic-to-dacitic volcano is at the southern end of the four overlapping summit craters. An unconfirmed eruption was noted in 1881, and solfataric activity was seen at the summit and upper flanks of Sinabung in 1912. No confirmed historical eruptions were recorded prior to explosive eruptions during August-September 2010 that produced ash plumes to 5 km above the summit.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://www.vsi.esdm.go.id/
Tungurahua | Ecuador | 1.467°S, 78.442°W | Summit elev. 5023 m
IG reported that activity at Tungurahua remained at moderate-to-high levels during 17-22 September. On 18 September ash plumes rose 2 km and drifted mainly NW. Ashfall was reported in Cusúa (8 km NW), Mocha (25 km W), and Chacauco (NW), and windows vibrated at the Tungurahua Observatory (OVT) in Guadalupe (14 km N). An ash plume rose 2 km and drifted NW on 19 September. At night crater incandescence was noted and windows vibrated. A steam plume rose 2 km and drifted W and NW on 20 September, and ashfall was reported in Runtún (6 km NNE). On 21 September ash plumes rose 2.5 km and drifted NW; ashfall was reported in Manzano (8 km SW), Choglontus (13 km WSW), Bilbao (8 km W), Cusúa, Coltaló, and Motilones. Steam-and-ash plumes rose 2.5 km on 22 September and drifted W to NW. Ash fell in Cevallos, Quero, Mocha, and Tizaleo.
Geologic Summary. Tungurahua, a steep-sided andesitic-dacitic stratovolcano that towers more than 3 km above its northern base, is one of Ecuador's most active volcanoes. Three major edifices have been sequentially constructed since the mid-Pleistocene over a basement of metamorphic rocks. Tungurahua II was built within the past 14,000 years following the collapse of the initial edifice. Tungurahua II itself collapsed about 3000 years ago and produced a large debris-avalanche deposit and a horseshoe-shaped caldera open to the west, inside which the modern glacier-capped stratovolcano (Tungurahua III) was constructed. Historical eruptions have all originated from the summit crater, accompanied by strong explosions and sometimes by pyroclastic flows and lava flows that reached populated areas at the volcano's base. Prior to a long-term eruption beginning in 1999 that caused the temporary evacuation of the city of Baños at the foot of the volcano, the last major eruption had occurred from 1916 to 1918, although minor activity continued until 1925.
Source: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/
Zhupanovsky | Eastern Kamchatka (Russia) | 53.589°N, 159.15°E | Summit elev. 2899 m
KVERT reported that an explosive eruption at Zhupanovsky continued during 12-19 September. Volcanologists in Nalychevo Valley observed short-duration explosions on 13 September which generated ash plumes that rose to altitudes of 3.5-4 km (11,500-13,000 ft) a.s.l. and drifted E. Satellite images detected a daily thermal anomaly and ash plumes that rose to altitudes of 3.5-4 km (11,500-13,000 ft) a.s.l. and drifted 220 km SE and S during 13-14 and 16 September. The Aviation Color Code remained at Orange.
Geologic Summary. The Zhupanovsky volcanic massif consists of four overlapping stratovolcanoes along a WNW-trending ridge. The elongated volcanic complex was constructed within a Pliocene-early Pleistocene caldera whose rim is exposed only on the eastern side. Three of the stratovolcanoes were built during the Pleistocene, the fourth is Holocene in age and was the source of all of Zhupanovsky's historical eruptions. An early Holocene stage of frequent moderate and weak eruptions from 7000 to 5000 years before present (BP) was succeeded by a period of infrequent larger eruptions that produced pyroclastic flows. The last major eruption took place about 800-900 years BP. Historical eruptions have consisted of relatively minor explosions from the third cone.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
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