Active volcanoes in the world: October 28 - November 3, 2015

Active volcanoes in the world: October 28 - November 3, 2015

New activity/unrest was observed at 5 volcanoes from October 28 - November 3, 2015. During the same period, ongoing activity was reported for 18 volcanoes.

New activity/unrest: Fuego, Guatemala  | Heard, Kerguelen Plateau  | Lascar, Chile  | Rinjani, Lombok Island (Indonesia)  | Turrialba, Costa Rica.

Ongoing activity: Aira, Kyushu (Japan)  | Bagana, Bougainville (Papua New Guinea)  | Colima, Mexico  | Colo, Sulawesi (Indonesia)  | Cotopaxi, Ecuador  | Dukono, Halmahera (Indonesia)  | Karangetang, Siau Island (Indonesia)  | Karymsky, Eastern Kamchatka (Russia)  | Kilauea, Hawaiian Islands (USA)  | Manam, Papua New Guinea  | Nevado del Ruiz, Colombia  | Piton de la Fournaise, Reunion Island (France)  | Santa Maria, Guatemala  | Sheveluch, Central Kamchatka (Russia)  | Shishaldin, Fox Islands (USA)  | Sinabung, Indonesia  | Tungurahua, Ecuador  | Ubinas, Peru.

New activity/unrest

Fuego, Guatemala
14.473°N, 90.88°W, Summit elev. 3763 m

INSIVUMEH reported that during 30 October-3 November explosions at Fuego generated ash plumes that rose 450-850 m above the crater and drifted as far as 10 km W and SW. Incandescent material was ejected 100 m high. Ashfall was reported in Panimache I and II (8 km SW), Morelia (9 km SW), Santa Sofía (12 km SW), and El Porvenir (8 km ENE) during 2-3 November.

Geologic summary: Volcán Fuego, one of Central America's most active volcanoes, is one of three large stratovolcanoes overlooking Guatemala's former capital, Antigua. The scarp of an older edifice, Meseta, lies between 3763-m-high Fuego and its twin volcano to the north, Acatenango. Construction of Meseta dates back to about 230,000 years and continued until the late Pleistocene or early Holocene. Collapse of Meseta may have produced the massive Escuintla debris-avalanche deposit, which extends about 50 km onto the Pacific coastal plain. Growth of the modern Fuego volcano followed, continuing the southward migration of volcanism that began at Acatenango. In contrast to the mostly andesitic Acatenango, eruptions at Fuego have become more mafic with time, and most historical activity has produced basaltic rocks. Frequent vigorous historical eruptions have been recorded since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

Heard, Kerguelen Plateau
53.106°S, 73.513°E, Summit elev. 2745 m

A plume from Heard was visible in a satellite image drifting SSW on 30 October.

Geologic summary: Heard Island on the Kerguelen Plateau in the southern Indian Ocean consists primarily of the emergent portion of two volcanic structures. The large glacier-covered composite basaltic-to-trachytic cone of Big Ben comprises most of the island, and the smaller Mt. Dixon volcano lies at the NW tip of the island across a narrow isthmus. Little is known about the structure of Big Ben volcano because of its extensive ice cover. The historically active Mawson Peak forms the island's 2745-m high point and lies within a 5-6 km wide caldera breached to the SW side of Big Ben. Small satellitic scoria cones are mostly located on the northern coast. Several subglacial eruptions have been reported in historical time at this isolated volcano, but observations are infrequent and additional activity may have occurred.

Lascar, Chile
23.37°S, 67.73°W, Summit elev. 5592 m

OVDAS-SERNAGEOMIN reported that at 0932 on 30 October the webcam recorded an ash plume rising 2.5 km above Láscar and drifting NE. A low-to-moderate-level seismic signal accompanied the emission. The Alert Level was raised to Yellow (the second lowest level on a four-color scale). ONEMI declared a Yellow Alert for the municipality of San Pedro de Atacama.

Geologic summary: Láscar is the most active volcano of the northern Chilean Andes. The andesitic-to-dacitic stratovolcano contains six overlapping summit craters. Prominent lava flows descend its NW flanks. An older, higher stratovolcano 5 km E, Volcán Aguas Calientes, displays a well-developed summit crater and a probable Holocene lava flow near its summit (de Silva and Francis, 1991). Láscar consists of two major edifices; activity began at the eastern volcano and then shifted to the western cone. The largest eruption took place about 26,500 years ago, and following the eruption of the Tumbres scoria flow about 9000 years ago, activity shifted back to the eastern edifice, where three overlapping craters were formed. Frequent small-to-moderate explosive eruptions have been recorded since the mid-19th century, along with periodic larger eruptions that produced ashfall hundreds of kilometers away. The largest historical eruption took place in 1993, producing pyroclastic flows to 8.5 km NW of the summit and ashfall in Buenos Aires.

Rinjani, Lombok Island (Indonesia)
8.42°S, 116.47°E, Summit elev. 3726 m

Based on satellite observations and information from PVMBG, the Darwin VAAC reported that on 31 October an ash plume from Rinjani rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted W before it detached. During 1-3 November ash plumes rose to altitudes of 2.7-4.3 km (9,000-14,000 ft) a.s.l. and drifted as far as 350 km NW, W, WSW, and SW. BNPB reported that on 3 November ash plumes rose as high as 1 km above Barujari Crater and drifted W; ashfall was reported in seven villages in North Lombok. According to a November news article, ash plumes that drifted W and SW caused three airports to close during 3-4 November: Ngurah Rai (150 km WSW) in Bali, Selaparang Airport (40 km WSW) in Lombok, and Blimbingsari Airport (230 km W) in Banyuwangi, East Java. On 4 November BNPB reported that ash plumes rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted W and SW.

Geologic summary: Rinjani volcano on the island of Lombok rises to 3726 m, second in height among Indonesian volcanoes only to Sumatra's Kerinci volcano. Rinjani has a steep-sided conical profile when viewed from the east, but the west side of the compound volcano is truncated by the 6 x 8.5 km, oval-shaped Segara Anak (Samalas) caldera. The caldera formed during one of the largest Holocene eruptions globally in 1257 CE, which truncated Samalas stratovolcano. The western half of the caldera contains a 230-m-deep lake whose crescentic form results from growth of the post-caldera cone Barujari at the east end of the caldera. Historical eruptions dating back to 1847 have been restricted to Barujari cone and consist of moderate explosive activity and occasional lava flows that have entered Segara Anak lake.

Turrialba, Costa Rica
10.025°N, 83.767°W, Summit elev. 3340 m

OVSICORI-UNA reported that ash plumes from Turrialba rose as high as 300 m and drifted WSW on 30 October.

Geologic summary: Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive 3340-m-high Turrialba is exceeded in height only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's most voluminous volcanoes. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.

Ongoing activity

Aira, Kyushu (Japan)
31.593°N, 130.657°E, Summit elev. 1117 m

JMA reported that on 30 October and 2 November small-scale events occurred at Showa Crater, at Aira Caldera’s Sakurajima volcano. The Alert Level remained at 3 (on a 5-level scale).

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.

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 during 29-30 October ash plumes from Bagana rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted 35-55 km SE, S, SW and 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.

Colima, Mexico
19.514°N, 103.62°W, Summit elev. 3850 m

Based on satellite images, wind data, and notices from the Mexico City MWO, the Washington VAAC reported that during 31 October-1 November ash plumes from Colima rose to altitudes of 6-6.7.3 km (20,000-24,000 ft) a.s.l. and drifted 20-45 km W and E. On 2 November ash emissions drifted NNE.

Geologic summary: The Colima volcanic complex is the most prominent volcanic center of the western Mexican Volcanic Belt. It consists of two southward-younging volcanoes, Nevado de Colima (the 4320 m high point of the complex) on the north and the 3850-m-high historically active Volcán de Colima at the south. A group of cinder cones of late-Pleistocene age is located on the floor of the Colima graben west and east of the Colima complex. Volcán de Colima (also known as Volcán Fuego) is a youthful stratovolcano constructed within a 5-km-wide caldera, breached to the south, that has been the source of large debris avalanches. Major slope failures have occurred repeatedly from both the Nevado and Colima cones, and have produced a thick apron of debris-avalanche deposits on three sides of the complex. Frequent historical eruptions date back to the 16th century. Occasional major explosive eruptions (most recently in 1913) have destroyed the summit and left a deep, steep-sided crater that was slowly refilled and then overtopped by lava dome growth.

Colo, Sulawesi (Indonesia)
0.162°S, 121.601°E, Summit elev. 404 m

PVMBG reported that seismicity at Colo declined during 1 September-25 October; 1-7 shallow-volcanic earthquakes and 1-3 volcanic earthquakes were recorded per day, which were rates similar to those recorded before a seismic increase in June. The Alert Level was lowered to 1 (on a scale of 1-4) on 26 October, and residents and tourists were warned not to approach the crater.

Geologic summary: Colo volcano forms the isolated small island of Una Una in the middle of the Gulf of Tomini in northern Sulawesi. The broad, low volcano contains a 2-km-wide caldera with a small central cone. Only three eruptions have been recorded in historical time, but two of those caused widespread damage over much of the island. The last eruption, in 1983, produced pyroclastic flows that swept over most of the island shortly after all residents had been evacuated.

Cotopaxi, Ecuador
0.677°S, 78.436°W, Summit elev. 5911 m

IG reported that although cloud cover often obscured views of Cotopaxi during 28 October-3 November emissions were observed daily; gas, steam, and ash plumes rose as high as 1.5 km and drifted W, SW, S, and E. A small lahar descended the W flank on 31 October.

Geologic summary: Symmetrical, glacier-clad Cotopaxi stratovolcano is Ecuador's most well-known volcano and one of its most active. The steep-sided cone is capped by nested summit craters, the largest of which is about 550 x 800 m in diameter. Deep valleys scoured by lahars radiate from the summit of the andesitic volcano, and large andesitic lava flows extend as far as the base of Cotopaxi. The modern conical volcano has been constructed since a major edifice collapse sometime prior to about 5000 years ago. Pyroclastic flows (often confused in historical accounts with lava flows) have accompanied many explosive eruptions of Cotopaxi, and lahars have frequently devastated adjacent valleys. The most violent historical eruptions took place in 1744, 1768, and 1877. Pyroclastic flows descended all sides of the volcano in 1877, and lahars traveled more than 100 km into the Pacific Ocean and western Amazon basin. The last significant eruption of Cotopaxi took place in 1904.

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 during 28 October-3 November ash plumes from Dukono rose to altitudes of 2.1-2.4 km (7,000-8,000 ft) a.s.l. and drifted 45-100 km SW, W, NW, N, 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. This complex volcano presents a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of the summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

Karangetang, Siau Island (Indonesia)
2.78°N, 125.4°E, Summit elev. 1784 m

Based on observations conducted at the Karangetang Volcano Observation Post in the village of Salili, PVMBG reported during 15-22 October activity remained stable. The lava dome was incandescent at night and produced a lava flow that traveled 600 m S. Incandescent avalanches from the lava-flow front traveled as far as 2 km E down the Batuawang and Kahetang drainages, 1 km down the Batang (S) drainage, and 1.8 km down the Kali drainage. Seismicity decreased, but continued to be dominated by signals characteristic of avalanches. Harmonic tremor was also detected. The Alert Level remained at 3 (on a scale of 1-4); visitors and residents were warned not to approach Karangetang within a 4-km radius.

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.

Karymsky, Eastern Kamchatka (Russia)
54.049°N, 159.443°E, Summit elev. 1513 m

KVERT reported that moderate explosive activity at Karymsky continued during 23-30 October. Satellite images detected a thermal anomaly over the volcano during 23-24 and 28 October. 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 during the early Holocene. The caldera cuts the south side of the Pleistocene Dvor volcano and is located outside the north margin of the large mid-Pleistocene Polovinka caldera, which contains the smaller Akademia Nauk and Odnoboky calderas. Most seismicity preceding Karymsky eruptions originated beneath Akademia Nauk caldera, located immediately south. The caldera enclosing Karymsky formed about 7600-7700 radiocarbon years ago; construction of the stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-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.

Kilauea, Hawaiian Islands (USA)
19.421°N, 155.287°W, Summit elev. 1222 m

HVO reported that seismicity beneath Kilauea's summit, upper East Rift Zone, and Southwest Rift Zone was at background levels during 28 October-3 November. The lava lake continued to circulate and spatter in the Overlook vent. The June 27th NE-trending lava flow continued to be active within 2.2-6.3 km NE of Pu'u 'O'o Crater.

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.

Manam, Papua New Guinea
4.08°S, 145.037°E, Summit elev. 1807 m

Based on observations of satellite imagery and information from RVO, the Darwin VAAC reported that on 29 October ash plumes from Manam 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: 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" channel lava flows and pyroclastic avalanches that have sometimes reached the coast. Five small satellitic centers are located near the island's shoreline on the northern, southern, and western sides. 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 valley. Frequent historical eruptions, typically of mild-to-moderate scale, have been recorded 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.

Nevado del Ruiz, Colombia
4.892°N, 75.324°W, Summit elev. 5279 m

Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported that during 27 October-2 November seismicity at Nevado del Ruiz was characterized by long-period earthquakes and short-duration volcanic tremor associated with gas-and-ash emissions. Earthquakes occurred at depths between 1.3 and 8.2 km. The largest event was recorded at 1409 on 31 October; it was a local M 1.3, SW of Arenas Crater at a depth of 2.6 km. Significant amounts of water vapor and gas rose from the crater during the week. A gas, steam, and ash plume rose 1.7 km and drifted NW on 30 October. 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 caldera of an older edifice. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. The prominent La Olleta pyroclastic cone located on the SW flank may also have been active in historical time. Steep headwalls of massive landslides cut the flanks. 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.

Piton de la Fournaise, Reunion Island (France)
21.244°S, 55.708°E, Summit elev. 2632 m

OVPDLF reported that on 29 October the seismic network at Piton de la Fournaise detected a clear increase in background noise, interpreted as tremor. At about 0400 the tremor became continuous and relatively strong. Lava fountains were visible in one of the vents.

Geologic summary: The massive Piton de la Fournaise basaltic shield volcano on the French island of Réunion in the western Indian Ocean is one of the world's most active volcanoes. Much of its more than 530,000-year history overlapped with eruptions of the deeply dissected Piton des Neiges shield volcano to the NW. Three calderas formed at about 250,000, 65,000, and less than 5000 years ago by progressive eastward slumping of the volcano. Numerous pyroclastic cones dot the floor of the calderas and their outer flanks. Most historical eruptions have originated from the summit and flanks of Dolomieu, a 400-m-high lava shield that has grown within the youngest caldera, which is 8 km wide and breached to below sea level on the eastern side. More than 150 eruptions, most of which have produced fluid basaltic lava flows, have occurred since the 17th century. Only six eruptions, in 1708, 1774, 1776, 1800, 1977, and 1986, have originated from fissures on the outer flanks of the caldera. The Piton de la Fournaise Volcano Observatory, one of several operated by the Institut de Physique du Globe de Paris, monitors this very active volcano.

Santa Maria, Guatemala
14.756°N, 91.552°W, Summit elev. 3772 m

INSIVUMEH reported that on 30 October heavy rainfall in the area triggered cold lahars which descended Santa María’s Cabello de Ángel (a tributary of Nima I) and San Isidro (tributary of El Tambor) drainages. The lahar in San Isidro carried blocks that were 1-2 m in dimeter. During 30-31 October explosions generated ash plumes that rose 800 m above the crater and drifted SW, causing ashfall in Monte Claro (S). Ash plumes from explosions rose as high as 1.1 km and drifted SE during 2-3 November; ash fell in finca El Faro (SW flank), La Florida (5 km S), San Marcos (10 km SW), and Palajunoj (18 km SSW).

Geologic summary: Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large stratovolcanoes that rises dramatically above the Pacific coastal plain of Guatemala. The 3772-m-high stratovolcano has a sharp-topped, conical profile that is cut on the SW flank by a large, 1.5-km-wide crater. The oval-shaped crater extends from just below the summit to the lower flank and was formed during a catastrophic eruption in 1902. The renowned plinian eruption of 1902 that devastated much of SW Guatemala followed a long repose period after construction of the large basaltic-andesite stratovolcano. The massive 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, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars.

Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m

KVERT reported that during 23-30 October lava-dome extrusion onto Sheveluch’s N flank was accompanied by fumarolic activity, dome incandescence, ash explosions, and hot avalanches. Satellite images detected a daily and intense thermal anomaly over the dome. Explosions and hot avalanches generated ash plumes that rose to an altitude of 5.5 km (18,000 ft) a.s.l. and drifted 80 km E, NE, and NW during 23-24 and 28-29 October. The Aviation Color Code remained at Orange.

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.

Shishaldin, Fox Islands (USA)
54.756°N, 163.97°W, Summit elev. 2857 m

AVO reported that seismicity at Shishaldin continued to be slightly elevated over background levels during 28 October-2 November, indicating that low-level eruptive activity confined to the summit crater continued. 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.

Sinabung, Indonesia
3.17°N, 98.392°E, Summit elev. 2460 m

Based on information from PVMBG, the Darwin VAAC reported that during 30-31 October ash plumes from Sinabung rose to altitudes of 3.4-7.6 km (20,000 ft) a.s.l. Plumes drifted over 35 km W on 31 October.

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 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.

Tungurahua, Ecuador
1.467°S, 78.442°W, Summit elev. 5023 m

IG reported high seismic activity at Tungurahua during 28 October-2 November, characterized by long-period events, volcano-tectonic events, and signals indicating emissions; cloud cover often prevented visual observations. Several minor ash emissions were visible on 29 October, and ashfall was reported in Choglontus (13 km WSW) and Manzanó (8 km SW). Steam, gas, and ash plumes rose as high as 1.5 km above the crater during 30 October-3 November and drifted E, NE, NW, and SW. Minor ashfall was reported in the Runtún sector (NNE) on 2 November.

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.

Ubinas, Peru
16.355°S, 70.903°W, Summit elev. 5672 m

Instituto Geofísico del Perú (IGP) Observatorio Volcanológico del Sur (OVS) reported that during 27 October-2 November seismicity at Ubinas fluctuated; the level of long-period earthquakes remained high and continued to increase, while hybrid and volcano-tectonic signals also increased but remained at low levels. Steam-and-gas plumes with some ash rose from the crater. Thermal anomalies were detected on 30 October and 1 November.

Geologic summary: A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. It is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I was followed by construction of Ubinas II beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and 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 about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.

Source: GVP

Comments

No comments yet. Why don't you post the first comment?

Post a comment

Your name: *

Your email address: *

Comment text: *

The image that appears on your comment is your Gravatar