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Smithsonian / USGS Weekly Volcanic Activity Report 27 July-2 August 2016
From: "Kuhn, Sally" <KUHNS@xxxxxx>
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Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx)
URL: http://www.volcano.si.edu/
New Activity/Unrest: Bezymianny, Central Kamchatka (Russia) | Chikurachki, Paramushir Island (Russia) | Chirpoi, Kuril Islands (Russia) | Fuego, Guatemala | Kilauea, Hawaiian Islands (USA) | Rinjani, Lombok Island (Indonesia)
Ongoing Activity: Aira, Kyushu (Japan) | Alaid, Kuril Islands (Russia) | Bagana, Bougainville (Papua New Guinea) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Gamalama, Halmahera (Indonesia) | Klyuchevskoy, Central Kamchatka (Russia) | Nevado del Ruiz, Colombia | Nevados de Chillán, Chile | Pavlof, United States | Sheveluch, Central Kamchatka (Russia) | Sinabung, Indonesia | Suwanosejima, Ryukyu Islands (Japan) | Tengger Caldera, Eastern Java (Indonesia)
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
Bezymianny | Central Kamchatka (Russia) | 55.972°N, 160.595°E | Summit elev. 2882 m
Based on information from the Yelizovo Airport (UHPP), the Tokyo VAAC reported that on 30 July an ash plume from Bezymianny rose to an altitude of 3 km (10,000 ft) a.s.l. drifted E. The Aviation Color Code level remained at Yellow.
Geologic Summary. Prior to its noted 1955-56 eruption, Bezymianny had been considered extinct. The modern volcano, much smaller in size than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years ago over a late-Pleistocene lava-dome complex and an ancestral edifice built about 11,000-7000 years ago. Three periods of intensified activity have occurred during the past 3000 years. The latest period, which was preceded by a 1000-year quiescence, began with the dramatic 1955-56 eruption. This eruption, similar to that of St. Helens in 1980, produced a large horseshoe-shaped crater that was formed by collapse of the summit and an associated lateral blast. Subsequent episodic but ongoing lava-dome growth, accompanied by intermittent explosive activity and pyroclastic flows, has largely filled the 1956 crater.
Sources: Tokyo Volcanic Ash Advisory Center (VAAC) http://ds.data.jma.go.jp/svd/
Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/
Chikurachki | Paramushir Island (Russia) | 50.324°N, 155.461°E | Summit elev. 1781 m
KVERT reported that an explosive eruption at Chikurachki''s summit crater continued during 22-29 July. Satellite images showed an ash plume drifting 176 km NE on 27 July. The Aviation Color Code remained at Orange (the second highest level on a four-color scale).
Geologic Summary. Chikurachki, the highest volcano on Paramushir Island in the northern Kuriles, is actually a relatively small cone constructed on a high Pleistocene volcanic edifice. Oxidized basaltic-to-andesitic scoria deposits covering the upper part of the young cone give it a distinctive red color. Frequent basaltic plinian eruptions have occurred during the Holocene. Lava flows from 1781-m-high Chikurachki reached the sea and form capes on the NW coast; several young lava flows also emerge from beneath the scoria blanket on the eastern flank. The Tatarinov group of six volcanic centers is located immediately to the south of Chikurachki, and the Lomonosov cinder cone group, the source of an early Holocene lava flow that reached the saddle between it and Fuss Peak to the west, lies at the southern end of the N-S-trending Chikurachki-Tatarinov complex. In contrast to the frequently active Chikurachki, the Tatarinov volcanoes are extensively modified by erosion and have a more complex structure. Tephrochronology gives evidence of only one eruption in historical time from Tatarinov, although its southern cone contains a sulfur-encrusted crater with fumaroles that were active along the margin of a crater lake until 1959.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/
Chirpoi | Kuril Islands (Russia) | 46.525°N, 150.875°E | Summit elev. 742 m
SVERT reported that a thermal anomaly over Snow, a volcano of Chirpoi, was detected in satellite images during 27-28 and 31 July. The Aviation Color Code remained at Yellow.
Geologic Summary. Chirpoi, a small island lying between the larger islands of Simushir and Urup, contains a half dozen volcanic edifices constructed within an 8-9 km wide, partially submerged caldera. The southern rim of the caldera is exposed on nearby Brat Chirpoev Island. The symmetrical Cherny volcano, which forms the 691 m high point of the island, erupted twice during the 18th and 19th centuries. The youngest volcano, Snow, originated between 1770 and 1810. It is composed almost entirely of lava flows, many of which have reached the sea on the southern coast. No historical eruptions are known from 742-m-high Brat Chirpoev, but its youthful morphology suggests recent strombolian activity.
Source: Sakhalin Volcanic Eruption Response Team (SVERT) http://www.imgg.ru/?id_d=659
Fuego | Guatemala | 14.473°N, 90.88°W | Summit elev. 3763 m
On 28 July CONRED noted that in recent days activity at Fuego was characterized by a high level of explosive activity. At 0545 activity increased further, heralding a shift to Strombolian activity and the beginning of the 12th eruptive episode at Fuego in 2016. Explosions produced ash plumes that rose 1 km and drifted 15 km SW, W, and NW, and caused shock waves detected in nearby areas. Pyroclastic flow descended the Las Lajas (SE) drainage, and ashfall was reported in Sangre de Cristo (8 km WSW) and San Pedro Yepocapa (8 km N). INSIVUMEH reported that during 28-29 July lava was ejected 500 m above the crater; lava flows traveled 3 km down the Santa Teresa (W) and Las Lajas drainages. Pyroclastic flows continued to descend the flanks. Ash plumes rose 1.7 km and drifted 35 km W and SW. Activity declined at 1500 on 29 July; ash plumes rose 800 m. On 30 July there were 3-5 explosions detected per hour, generating gray ash plumes that rose 550-850 m and drifted 10 km W and SW. Incandescent material was ejected as high as 150 m above the crater. Lava flows remained incandescent as far as 1.8 km in the drainages. Ash fell in Morelia (9 km SW), Santa Sofía (12 km SW), El Porvenir (8 km ENE), and Panimaché I and II (8 km SW). INSIVUMEH noted that at 0130 on 30 July the activity ended. Minor explosions generated ash plumes that did not rise higher than 750 m.
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.
Sources: Coordinadora Nacional para la Reducción de Desastres (CONRED) http://conred.gob.gt/;
Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/
Kilauea | Hawaiian Islands (USA) | 19.421°N, 155.287°W | Summit elev. 1222 m
HVO reported that during 27 July-2 August the lava lake continued to rise and fall, circulate, and spatter in Kilauea''s Overlook vent. Several incandescent vents on Pu''u ''O''o Crater''s floor were evident in webcam images. The 61G lava flow, originating from a vent on Pu''u ''O''o Crater''s E flank, continued to enter the ocean at the Kamokuna area; the flow at the ocean entry continued to widen and by 30 July was 240 m across. Nighttime webcam views of the flow field showed incandescent areas mostly on the coastal plain.
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 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/
Rinjani | Lombok Island (Indonesia) | 8.42°S, 116.47°E | Summit elev. 3726 m
Based on satellite and pilot observations, the Darwin VAAC reported that an eruption at Rinjani on 1 August generated an ash plume that rose to an altitude of 9.8 km (32,000 ft) a.s.l. and drifted S. Ash plumes were first visible in satellite images at 1150, and according to PVMBG passengers aboard a plane noted that ash plumes rose 2 km above the crater. BNPB noted that the Lombok International Airport closed at 1655 and was scheduled to reopen at 1000 the next day. Later on 1 August ash plumes rose to altitudes of 4.3-6.1 km (14,000-20,000 ft) a.s.l. and drifted S, SW, and W. No plumes were visible at 1730; conditions had returned to normal levels although BNPB warned that the public should stay at least 1.5 km away from the volcano.
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.
Sources: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/
Badan Nacional Penanggulangan Bencana (BNPB) http://www.bnpb.go.id/;
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 on 26 July an explosive eruption at Showa Crater (at Aira Caldera’s Sakurajima volcano) ejected tephra 800 m away from the crater and generated an ash plume that rose 5 km above the crater rim. Significant amounts of ash fell in the W and SW parts of the island and in multiple areas of Kagoshima (10-12 km W). 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 Strombolian activity at a new cinder cone in Alaid''s summit crater was detected during 22-29 July, with lava flowing down the SW flank. On 26 July satellite images showed a thermal anomaly at the volcano, and a gas-and-steam plume that drifted 155 km NE. The Aviation Color Code remained at Orange (the second highest 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/
Bagana | Bougainville (Papua New Guinea) | 6.137°S, 155.196°E | Summit elev. 1855 m
Based on analyses of satellite imagery and model data, the Darwin VAAC reported that during 29 July-1 August ash plumes from Bagana rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted SW, W, and NW.
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/
Colima | Mexico | 19.514°N, 103.62°W | Summit elev. 3850 m
The Washington VAAC reported that steam-and-gas puffs containing minor amounts of ash rose from Colima on 28 July. The next day an ash plume identified in satellite images and recorded by the webcam rose to an altitude of 5.8 km (19,000 ft) a.s.l. and drifted NW. On 31 July Colima Towers and the Mexico City MWO reported that ash plumes rose to altitudes of 5.2-7.3 km (17,000-24,000 ft) a.s.l. and drifted W and WSW.
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/
Dukono | Halmahera (Indonesia) | 1.693°N, 127.894°E | Summit elev. 1229 m
Based on ground reports from PVMBG and model data, the Darwin VAAC reported that during 27-29 July ash plumes from Dukono rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted N and E.
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/
Gamalama | Halmahera (Indonesia) | 0.8°N, 127.33°E | Summit elev. 1715 m
PVMBG reported that at 0628 on 3 August a weak explosion at Gamalama generated an ash plume that rose 500-600 m above the crater and drifted SE and S. Ash emissions declined at 0655. Ashfall was reported in areas on the SSE flank including Ake Huda. The report also noted a brief airport closing. The Alert Level remained at 2 (on a scale of 1-4); visitors and residents were warned not to approach the crater within a 1.5-km radius.
Geologic Summary. Gamalama is a near-conical stratovolcano that comprises the entire island of Ternate off the western coast of Halmahera, and is one of Indonesia's most active volcanoes. The island was a major regional center in the Portuguese and Dutch spice trade for several centuries, which contributed to the thorough documentation of Gamalama's historical activity. Three cones, progressively younger to the north, form the summit. Several maars and vents define a rift zone, parallel to the Halmahera island arc, that cuts the volcano. Eruptions, recorded frequently since the 16th century, typically originated from the summit craters, although flank eruptions have occurred in 1763, 1770, 1775, and 1962-63.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM) http://www.vsi.esdm.go.id/
Klyuchevskoy | Central Kamchatka (Russia) | 56.056°N, 160.642°E | Summit elev. 4754 m
KVERT reported that a Strombolian eruption at Klyuchevskoy continued during 22-29 July. Volcanic bombs that were ejected 200-300 m above the summit crater and 50 m above a cinder cone landed in the Apakhonchich drainage on the SE flank. A lava flow traveled down the Apakhonchich drainage. Satellite images showed a large and intense daily thermal anomaly at the volcano, and ash plumes drifting over 140 km E during 22-23 and 26 July. The Aviation Color Code was raised to Orange.
Geologic Summary. Klyuchevskoy (also spelled Kliuchevskoi) is Kamchatka's highest and most active volcano. Since its origin about 6000 years ago, the beautifully symmetrical, 4835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. It rises above a saddle NE of sharp-peaked Kamen volcano and lies SE of the broad Ushkovsky massif. More than 100 flank eruptions have occurred during the past roughly 3000 years, with most lateral craters and cones occurring along radial fissures between the unconfined NE-to-SE flanks of the conical volcano between 500 m and 3600 m elevation. The morphology of the 700-m-wide summit crater has been frequently modified by historical eruptions, which have been recorded since the late-17th century. Historical eruptions have originated primarily from the summit crater, but have also included numerous major explosive and effusive eruptions from flank craters.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/
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 26 July-1 August seismicity levels at Nevado del Ruiz slightly increased as compared to the week before. Significant amounts of water vapor and gas rose from the crater. A gas, steam, and ash plume rose 700 m above the crater rim and drifted NW and W on 29 July. The Alert Level remained at III (Yellow; the second lowest level on a four-color scale).
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: Servicio Geológico Colombiano (SGC) http://www.ingeominas.gov.co/
Nevados de Chillán | Chile | 36.863°S, 71.377°W | Summit elev. 3212 m
The Buenos Aires VAAC reported that on 1 August a webcam recorded an ash puff from Nevados de Chillán that rose to an altitude of 3.6 km (12,000 ft) a.s.l., and then emissions of gas and minor amounts of ash at crater level.
Geologic Summary. The compound volcano of Nevados de Chillán is one of the most active of the Central Andes of Chile. Three late-Pleistocene to Holocene stratovolcanoes were constructed along a NNW-SSE line within three nested Pleistocene calderas, which produced ignimbrite sheets extending more than 100 km into the Central Depression of Chile. The largest stratovolcano, dominantly andesitic, 3212-m-high Cerro Blanco (Volcán Nevado), is located at the NW end of the group, and 3089-m-high Volcán Viejo (Volcán Chillán), which was the main active vent during the 17th-19th centuries, occupies the SE end. The new Volcán Nuevo lava-dome complex formed between 1906 and 1945 between the two volcanoes and grew to exceed Volcán Viejo in altitude. The Volcán Arrau dome complex was constructed SE of Volcán Nuevo between 1973 and 1986, eventually exceeding its height by 20 m.
Source: Buenos Aires Volcanic Ash Advisory Center (VAAC) http://www.smn.gov.ar/vaac/
Pavlof | United States | 55.417°N, 161.894°W | Summit elev. 2493 m
AVO reported that on 28 July vigorous steam-rich gas plumes from Pavlof were visible in webcam images from Cold Bay (60 km SW) and Black Hills (35 km NNE). The report also noted that recent satellite images and a pilot observation indicated minor ash emissions associated with degassing which rose to an altitude less that 4.5 km (15,000 ft) a.s.l. The Aviation Color Code was raised to Orange and Volcano Alert Level was raised to Watch. On 29 July seismicity began to decrease. On 30 July minor steam emissions were visible in webcam images from Black Hills, and on 2 August a weak thermal anomaly was detected.
Geologic Summary. The most active volcano of the Aleutian arc, Pavlof is a 2519-m-high Holocene stratovolcano that was constructed along a line of vents extending NE from the Emmons Lake caldera. Pavlof and its twin volcano to the NE, 2142-m-high Pavlof Sister, form a dramatic pair of symmetrical, glacier-covered stratovolcanoes that tower above Pavlof and Volcano bays. A third cone, Little Pavlof, is a smaller volcano on the SW flank of Pavlof volcano, near the rim of Emmons Lake caldera. Unlike Pavlof Sister, Pavlof has been frequently active in historical time, typically producing Strombolian to Vulcanian explosive eruptions from the summit vents and occasional lava flows. The active vents lie near the summit on the north and east sides. The largest historical eruption took place in 1911, at the end of a 5-year-long eruptive episode, when a fissure opened on the N flank, ejecting large blocks and issuing lava flows.
Source: US Geological Survey Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/
Sheveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit elev. 3283 m
KVERT reported that during 22-29 July lava-dome extrusion onto Sheveluch’s N flank was accompanied by strong fumarolic activity, dome incandescence, ash explosions, and hot avalanches. Satellite images showed a daily 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/
Sinabung | Indonesia | 3.17°N, 98.392°E | Summit elev. 2460 m
Based on satellite and webcam images, model data, and ground reports from PVMBG, the Darwin VAAC reported that during 27-28 July and 1 August ash plumes from Sinabung rose to altitudes of 4-4.3 km (13,000-14,000 ft) a.s.l. and drifted NE, E, and SSE.
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/
Suwanosejima | Ryukyu Islands (Japan) | 29.638°N, 129.714°E | Summit elev. 796 m
Based on JMA notices and satellite-image analyses, the Tokyo VAAC reported that during 1-2 August ash plumes from Suwanosejima rose to altitudes of 1.5-3.4 km (5,000-11,000 ft) a.s.l. and drifted W and SE.
Geologic Summary. The 8-km-long, spindle-shaped island of Suwanosejima in the northern Ryukyu Islands consists of an andesitic stratovolcano with two historically active summit craters. The summit of the volcano is truncated by a large breached crater extending to the sea on the east flank that was formed by edifice collapse. Suwanosejima, one of Japan's most frequently active volcanoes, was in a state of intermittent strombolian activity from Otake, the NE summit crater, that began in 1949 and lasted until 1996, after which periods of inactivity lengthened. The largest historical eruption took place in 1813-14, when thick scoria deposits blanketed residential areas, and the SW crater produced two lava flows that reached the western coast. At the end of the eruption the summit of Otake collapsed forming a large debris avalanche and creating the horseshoe-shaped Sakuchi caldera, which extends to the eastern coast. The island remained uninhabited for about 70 years after the 1813-1814 eruption. Lava flows reached the eastern coast of the island in 1884. Only about 50 people live on the island.
Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://ds.data.jma.go.jp/svd/
Tengger Caldera | Eastern Java (Indonesia) | 7.942°S, 112.95°E | Summit elev. 2329 m
Based on analyses of satellite images and information from PVMBG, the Darwin VAAC reported that during 27-31 July and 1 August ash plumes from Tengger Caldera''''s Bromo cone rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted as far as 55 km NW, W, and SW.
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/
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