Smithsonian / USGS Weekly Volcanic Activity Report 24 February-1 March 2016
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Smithsonian / USGS Weekly Volcanic Activity Report
24 February-1 March 2016
Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx)
URL: http://www.volcano.si.edu/reports_weekly.cfm
New Activity/Unrest: Aira, Kyushu (Japan) | Alaid, Kuril Islands (Russia) | Telica, Nicaragua | Tungurahua, Ecuador
Ongoing Activity: Colima, Mexico | Copahue, Central Chile-Argentina border | Dukono, Halmahera (Indonesia) | Karangetang, Siau Island (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Masaya, Nicaragua | Momotombo, Nicaragua | Nevado del Ruiz, Colombia | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Soputan, Sulawesi (Indonesia) | Tengger Caldera, Eastern Java (Indonesia) | 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
Aira | Kyushu (Japan) | 31.593°N, 130.657°E | Summit elev. 1117 m
During 15-22 February JMA reported that six explosions from Showa Crater at Aira Caldera’s Sakurajima volcano ejected tephra as far as 1,300 m. A small-scale eruption occurred from Minamidake summit crater on 20 February. 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.
Source: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/
Alaid | Kuril Islands (Russia) | 50.861°N, 155.565°E | Summit elev. 2285 m
KVERT reported that an intense thermal anomaly was detected in satellite images over Alaid during 0800-1256 on 21 February. Diffuse ash emissions drifted 50 km E. The Aviation Color Code was raised to Yellow (the second lowest level on a four-color scale).
Geologic Summary. The highest and northernmost volcano of the Kuril Islands, 2285-m-high Alaid is a symmetrical stratovolcano when viewed from the north, but has a 1.5-km-wide summit crater that is breached widely to the south. Alaid is the northernmost of a chain of volcanoes constructed west of the main Kuril archipelago and rises 3000 m from the floor of the Sea of Okhotsk. Numerous pyroclastic cones dot the lower flanks of basaltic to basaltic-andesite Alaid volcano, particularly on the NW and SE sides, including an offshore cone formed during the 1933-34 eruption. Strong explosive eruptions have occurred from the summit crater beginning in the 18th century. Reports of eruptions in 1770, 1789, 1821, 1829, 1843, 1848, and 1858 were considered incorrect by Gorshkov (1970). Explosive eruptions in 1790 and 1981 were among the largest in the Kuril Islands during historical time.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
Telica | Nicaragua | 12.602°N, 86.845°W | Summit elev. 1061 m
INETER reported high micro-seismicity at Telica during 20 February-1 March. Incandescence from the vent on the crater floor increased; lava in the vent was first observed on 25 February and persisted through 1 March. Five gas-and-ash explosions were recorded during 19 February-1 March, generating plumes that rose 300 above the crater and drifted W and SW. The strongest event started at 0819 and produced gas-and-ash emissions for 14 minutes.
Geologic Summary. Telica, one of Nicaragua's most active volcanoes, has erupted frequently since the beginning of the Spanish era. This volcano group consists of several interlocking cones and vents with a general NW alignment. Sixteenth-century eruptions were reported at symmetrical Santa Clara volcano at the SW end of the group. However, its eroded and breached crater has been covered by forests throughout historical time, and these eruptions may have originated from Telica, whose upper slopes in contrast are unvegetated. The steep-sided cone of 1061-m-high Telica is truncated by a 700-m-wide double crater; the southern crater, the source of recent eruptions, is 120 m deep. El Liston, immediately SE of Telica, has several nested craters. The fumaroles and boiling mudpots of Hervideros de San Jacinto, SE of Telica, form a prominent geothermal area frequented by tourists, and geothermal exploration has occurred nearby.
Source: Instituto Nicaragüense de Estudios Territoriales (INETER) http://www.ineter.gob.ni/
Tungurahua | Ecuador | 1.467°S, 78.442°W | Summit elev. 5023 m
IG reported that a swarm of volcano-tectonic and long-period earthquakes began at Tungurahua at 1105 on 26 February. At 1211 an explosion produced a plume with high ash content that rose 5 km above the crater and drifted W. Ash fell in Juive (NW), Chico, Choglontús (13 km WSW), El Manzano (8 km SW), and Cahuají (8 km SW). Explosions at 1239, 1247, and 1252 generated ash plumes that rose 6-7 km above the crater. An explosion at 1333 generated a small pyroclastic flow that descended halfway down the W and NW flanks, and an ash plume that rose 8 km. At 1535 another pyroclastic flow, generated from material spilling over the WNW rim, also traveled halfway down the volcano in the Mandur (NW), Hacienda (NW), and Cusua (NW) drainages. Ashfall was noted in El Manzano, Choglontús, Pillate (8 km W), Juive, Ambato (31 km NW), and Quero (20 km NW); reddish, black, gray, and beige tephra up to 3 mm in diameter fell in Pillate and Choglontús. In the evening Strombolian activity ejected incandescent blocks which rolled 1.5 km down the flanks. For a short time around 2200 lava fountains rose 500 m.
Explosions and nighttime crater incandescence continued to be detected during 27 February-1 March, and explosions sometimes vibrated nearby structures. Ashfall was observed daily in areas including El Manzano, Palitahua (6 km SSW), Cotaló (8 km NW), Cahuají, Providencia, Puela (8 km SW), Chazo, Pillate, Choglontús, Mocha (25 km WNW), and areas of Quero. Ash plumes were observed rising 2-4 km above the crater on 27 February and 1 March. During 29 February-1 March pyroclastic flows descended the Juive, Mandur (NW), Achupashal (NW), and Romero drainages; the largest traveled 1.5 km down the Achupashal.
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/
Ongoing Activity
Colima | Mexico | 19.514°N, 103.62°W | Summit elev. 3850 m
Based on satellite and webcam images, and notices from the Mexico City MWO, the Washington VAAC reported that during 24-25 and 27 February ash plumes from Colima rose to altitude of 5.2-5.8 km (17,000-19,000 ft) a.s.l. and drifted as far as 150 km NE and N.
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.
Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html
Copahue | Central Chile-Argentina border | 37.856°S, 71.183°W | Summit elev. 2953 m
Based on satellite and webcam views, the Buenos Aires VAAC reported that during 24-25 and 28 February steam plumes containing minor amounts of ash rose from Copahue and drifted E at altitudes of 3.3-4.3 km (11,000-14,000 ft) a.s.l.
Geologic Summary. Volcán Copahue is an elongated composite cone constructed along the Chile-Argentina border within the 6.5 x 8.5 km wide Trapa-Trapa caldera that formed between 0.6 and 0.4 million years ago near the NW margin of the 20 x 15 km Pliocene Caviahue (Del Agrio) caldera. The eastern summit crater, part of a 2-km-long, ENE-WSW line of nine craters, contains a briny, acidic 300-m-wide crater lake (also referred to as El Agrio or Del Agrio) and displays intense fumarolic activity. Acidic hot springs occur below the eastern outlet of the crater lake, contributing to the acidity of the Río Agrio, and another geothermal zone is located within Caviahue caldera about 7 km NE of the summit. Infrequent mild-to-moderate explosive eruptions have been recorded at Copahue since the 18th century. Twentieth-century eruptions from the crater lake have ejected pyroclastic rocks and chilled liquid sulfur fragments.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.smn.gov.ar/vaac/buenosaires/productos.php
Dukono | Halmahera (Indonesia) | 1.693°N, 127.894°E | Summit elev. 1229 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 24 February-1 March ash plumes from Dukono rose to altitudes of 2.4-3 km (8,000-10,000 ft) a.s.l. and drifted 15-120 km in multiple directions.
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.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
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 that during 17-24 February the lava dome was incandescent at night. Variable amounts of white and blue emissions rose as high as 100 m above Main Crater. RSAM values doubled in January and continued to rise in February due to an increased number of shallow volcanic earthquakes. 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 stratovolcano contains five summit craters along a N-S line. It 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/
Karymsky | Eastern Kamchatka (Russia) | 54.049°N, 159.443°E | Summit elev. 1513 m
KVERT reported that moderate explosive activity at Karymsky continued during 19-26 February. Satellite images detected a thermal anomaly on 22 February. 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
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 24 February-1 March. The lava lake continued to circulate and spatter in the Overlook vent. Webcams recorded multiple incandescent outgassing vents within Pu'u 'O'o Crater and high on the northeast rim. During 24-25 and 29 February lava from at most two vents flowed onto the crater floor. The June 27th NE-trending lava flow continued to be active within 6 km NE of Pu'u 'O'o Crater, burning some areas of forest.
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/
Masaya | Nicaragua | 11.984°N, 86.161°W | Summit elev. 635 m
INETER reported that the lava lakes in three vents on the floor of Masaya's Santiago crater were active during 20 February-1 March. Volcanic tremor remained high and RSAM values were at high to very high levels. On 23 February small explosions ejected spatter onto the crater floor. During fieldwork volcanologists observed active lava lakes in all three vents on the crater floor, and noted that the inner walls of the crater were being eroded due to the lava lake. A new vent was forming on the SE part of the crater floor. During a second visit on 24 February INETER staff noted that the vents had become larger due to landslides on the crater walls. Small streams of lava sporadically originated from the NE vent. By 1 March the two vents in the SW part of the crater had almost merged.
Geologic Summary. Masaya is one of Nicaragua's most unusual and most active volcanoes. It lies within the massive Pleistocene Las Sierras pyroclastic shield volcano and is a broad, 6 x 11 km basaltic caldera with steep-sided walls up to 300 m high. The caldera is filled on its NW end by more than a dozen vents that erupted along a circular, 4-km-diameter fracture system. The twin volcanoes of Nindirí and Masaya, the source of historical eruptions, were constructed at the southern end of the fracture system and contain multiple summit craters, including the currently active Santiago crater. A major basaltic plinian tephra erupted from Masaya about 6500 years ago. Historical lava flows cover much of the caldera floor and have confined a lake to the far eastern end of the caldera. A lava flow from the 1670 eruption overtopped the north caldera rim. Masaya has been frequently active since the time of the Spanish Conquistadors, when an active lava lake prompted attempts to extract the volcano's molten "gold." Periods of long-term vigorous gas emission at roughly quarter-century intervals cause health hazards and crop damage.
Source: Instituto Nicaragüense de Estudios Territoriales (INETER) http://www.ineter.gob.ni/
Momotombo | Nicaragua | 12.422°N, 86.54°W | Summit elev. 1297 m
INETER reported that during 19 February-1 March explosions at Momotombo were detected daily; 88 explosions were detected during 1 December 2015-1 March 2016. Explosions produced ash plumes, and ejected incandescent material onto the N, NE, E, and SE flanks. Ash plumes rose 1.7-2.3 km above the crater and drifted SW during 21-22 February; gas-and-ash plumes rose 1.8 km on 24 February; an ash plume rose 1 km on 25 February; and a small gas-and-ash plume rose 300 m on 26 February. A pyroclastic flow traveled 3.5 km down the N and NW flanks during 23-24 February. Explosions on 27 February ejected tephra 300 m above the crater. At 0646 on 1 March explosions ejected gas and incandescent tephra; an ash plume rose 1.2 km and drifted W and SW. The gas-and-ash emissions lasted 16 minutes, causing the plume to widen and darken the sky.
Geologic Summary. Momotombo is a young, 1297-m-high stratovolcano that rises prominently above the NW shore of Lake Managua, forming one of Nicaragua's most familiar landmarks. Momotombo began growing about 4500 years ago at the SE end of the Marrabios Range and consists of a somma from an older edifice that is surmounted by a symmetrical younger cone with a 150 x 250 m wide summit crater. Young lava flows from Momotombo have flowed down the NW flank into the 4-km-wide Monte Galán caldera. The youthful cone of Momotombito forms a 391-m-high island offshore in Lake Managua. Momotombo has a long record of strombolian eruptions, punctuated by occasional larger explosive activity. The latest eruption, in 1905, produced a lava flow that traveled from the summit to the lower NE base. A small black plume was seen above the crater after an April 10, 1996 earthquake, but later observations noted no significant changes in the crater. A major geothermal field is located on the southern flank of the volcano.
Source: Instituto Nicaragüense de Estudios Territoriales (INETER) http://www.ineter.gob.ni/
Nevado del Ruiz | Colombia | 4.892°N, 75.324°W | Summit elev. 5279 m
Based on notices from the Bogota MWO, pilot observations, and wind data, the Washington VAAC reported that on 24 February an ash plume from Nevado del Ruiz possibly rose to altitudes of 5.5-6.1 km (18,000-20,000 ft) a.s.l. and drifted NW and S. According to the VAAC, SGC reported an ash emission on 29 February.
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.
Source: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html
Sheveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit elev. 3283 m
KVERT reported that during 19-26 February 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. 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
Sinabung | Indonesia | 3.17°N, 98.392°E | Summit elev. 2460 m
Based on satellite images, ground reports, and information from PVMBG, the Darwin VAAC reported that during 24 February-1 March ash plumes from Sinabung rose to altitudes of 3.6-4.3 km (12,000-14,000 ft) a.s.l. and drifted over 45 km in multiple directions.
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.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
Soputan | Sulawesi (Indonesia) | 1.112°N, 124.737°E | Summit elev. 1785 m
PVMBG reported that during 22-29 February diffuse white plumes from Soputan rose as high as 75 m above the crater. Seismicity was dominated by signals indicating avalanches and emissions, though shallow volcanic and low-frequency earthquakes were also detected. The Alert Level remained at 3 (on a scale of 1-4); residents and tourists were advised not to approach the craters within a radius of 6.5 km.
Geologic Summary. The Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano rises to 1784 m and is located SW of Riendengan-Sempu, which some workers have included with Soputan and Manimporok (3.5 km ESE) as a volcanic complex. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://www.vsi.esdm.go.id/
Tengger Caldera | Eastern Java (Indonesia) | 7.942°S, 112.95°E | Summit elev. 2329 m
Based on satellite images, wind data, ground reports, and information from PVMBG, the Darwin VAAC reported that during 17-23 February ash plumes from Tengger Caldera's Bromo cone rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted at most 55 km NW, ESE, and SE.
Geologic Summary. The 16-km-wide Tengger caldera is located at the northern end of a volcanic massif extending from Semeru volcano. The massive volcanic complex dates back to about 820,000 years ago and consists of five overlapping stratovolcanoes, each truncated by a caldera. Lava domes, pyroclastic cones, and a maar occupy the flanks of the massif. The Ngadisari caldera at the NE end of the complex formed about 150,000 years ago and is now drained through the Sapikerep valley. The most recent of the calderas is the 9 x 10 km wide Sandsea caldera at the SW end of the complex, which formed incrementally during the late Pleistocene and early Holocene. An overlapping cluster of post-caldera cones was constructed on the floor of the Sandsea caldera within the past several thousand years. The youngest of these is Bromo, one of Java's most active and most frequently visited volcanoes.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
Zhupanovsky | Eastern Kamchatka (Russia) | 53.589°N, 159.15°E | Summit elev. 2899 m
KVERT reported that moderate gas-and-steam activity at Zhupanovsky continued during 19-26 February. 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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