Sally Kuhn Sennert - Weekly Report Editor (kuhns@xxxxxx)
URL: http://www.volcano.si.edu
New Activity/Unrest: Chikurachki, Paramushir Island (Russia) | Chirpoi, Kuril Islands (Russia)
Ongoing Activity: Aira, Kyushu (Japan) | Alaid, Kuril Islands (Russia) | Colima, Mexico | Dukono, Halmahera (Indonesia) | Fuego, Guatemala | Kilauea, Hawaiian Islands (USA) | Klyuchevskoy, Central Kamchatka (Russia) | Masaya, Nicaragua | Popocatepetl, Mexico | Ruapehu, North Island (New Zealand) | Santa Maria, Guatemala | 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
Chikurachki | Paramushir Island (Russia) | 50.324°N, 155.461°E | Summit elev. 1781 m
KVERT reported that no activity was observed after an eruption at Chikurachki during 27-28 July; the Aviation Color Code was lowered to Yellow (the second lowest level on a four-color scale) on 31 July and then to Green (the lowest level) on 4 August.
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/i
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 on 10 August. 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
Ongoing Activity
Aira | Kyushu (Japan) | 31.593°N, 130.657°E | Summit elev. 1117 m
JMA reported that during 10-13 and 15 August small-scale explosions occurred at Minamidake summit 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.
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 moderate activity at Alaid’s summit crater was detected during 5-12 August. Satellite images showed a weak thermal anomaly at the volcano during 6-7 and 11 August. The Aviation Color Code was lowered 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/i
Colima | Mexico | 19.514°N, 103.62°W | Summit elev. 3850 m
Based on satellite and webcam images, the Washington VAAC reported that on 12, 14, and 16 August ash plumes from Colima rose to altitudes of 4.3-5.5 km (14,000-18,000 ft) a.s.l. and drifted NW and W.
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
Dukono | Halmahera (Indonesia) | 1.693°N, 127.894°E | Summit elev. 1229 m
Based on ground reports from PVMBG, satellite data, and model data, the Darwin VAAC reported that during 10-16 August ash plumes from Dukono rose to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. and drifted possibly as far as 270 km E, NE, and N.
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/an
Fuego | Guatemala | 14.473°N, 90.88°W | Summit elev. 3763 m
INSIVUMEH reported that during 13-16 August explosions at Fuego generated ash plumes that rose as high as 1.1 km and drifted 10-12 km W, SW, and SE. Some explosions also ejected incandescent material as high as 150 m that then caused minor avalanches within the crater. Ashfall was reported in Morelia (9 km SW), Santa Sofía (12 km SW), Los Yucales (12 km SW), El Porvenir (8 km ENE), Los Chucales, and Panimaché I and II (8 km SW).
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.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivum
Kilauea | Hawaiian Islands (USA) | 19.421°N, 155.287°W | Summit elev. 1222 m
During 10-16 August HVO reported that 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 multiple areas near Kamokuna. Scattered breakouts were active on the coastal plain and the pali. A small delta collapse during the afternoon of 9 August temporarily darkened the ocean-entry plume.
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/
Klyuchevskoy | Central Kamchatka (Russia) | 56.056°N, 160.642°E | Summit elev. 4754 m
KVERT reported that a Strombolian eruption at Klyuchevskoy continued during 5-12 August. Volcanic bombs that were ejected above the summit crater and the 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 about 370 km SE and W during 9 and 11 August. The Aviation Color Code remained at 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/i
Masaya | Nicaragua | 11.984°N, 86.161°W | Summit elev. 635 m
Based on analysis of satellite imagery, the Washington VAAC reported that on 15 August a possible ash plume from Masaya rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted NW. Elevated seismicity and a thermal anomaly detected in satellite images indicated increased activity. In a report posted later that day the Washington VAAC noted that the webcam recorded minor ash emissions.
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: Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov
Popocatepetl | Mexico | 19.023°N, 98.622°W | Summit elev. 5426 m
Each day during 10-16 August CENAPRED reported 35-133 emissions from Popocatépetl, some of which contained minor amounts of ash, and as many as four explosions. Cloud cover sometimes prevented observations, though gas-and-steam plumes were visible almost daily. Crater incandescence was visible at night. On 11 August there were six landslides detected by the seismic network; the largest one occurred on the NW flank at 0853 and had a volume of 440 m3, and the second largest one, on the N flank, occurred at 1756 and had a volume of 220 m3. An explosion on 12 August generated an ash plume that rose 2.5 km above the crater and drifted WNW, causing ashfall in Ozumba (18 km W) and Atlautla (16 km W). An explosion at 0034 on 13 August ejected incandescent material onto the flanks. Two more explosions that day and one on 14 August produced plumes with low ash content that rose as high as 1 km. The Alert Level remained at Yellow, Phase Two.
Geologic Summary. Volcán Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5426 m 70 km SE of Mexico City to form North America's 2nd-highest volcano. The glacier-clad stratovolcano contains a steep-walled, 400 x 600 m wide crater. The generally symmetrical volcano is modified by the sharp-peaked Ventorrillo on the NW, a remnant of an earlier volcano. At least three previous major cones were destroyed by gravitational failure during the Pleistocene, producing massive debris-avalanche deposits covering broad areas to the south. The modern volcano was constructed south of the late-Pleistocene to Holocene El Fraile cone. Three major plinian eruptions, the most recent of which took place about 800 CE, have occurred from Popocatépetl since the mid Holocene, accompanied by pyroclastic flows and voluminous lahars that swept basins below the volcano. Frequent historical eruptions, first recorded in Aztec codices, have occurred since precolumbian time.
Source: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred
Ruapehu | North Island (New Zealand) | 39.28°S, 175.57°E | Summit elev. 2797 m
GeoNet reported that the temperature of Ruapehu’s summit Crater Lake had been declining since May. During an overflight on 10 August scientists recorded gas emissions at typical low background levels. The next day the lake water temperature was 12.6ºC, one of the lowest temperatures since the 1995/1996 eruptions. The lake was a dark green, overflowing, and sulfur slicks outlined areas of upwelling. A strong sulfur odor was noted near the lake. The level of volcanic tremor which was at moderate levels during May-June had declined to typical background levels. The Volcanic Alert Level was lowered to 1 (minor volcanic unrest) and the Aviation Colour Code was lowered to Green.
Geologic Summary. Ruapehu, one of New Zealand's most active volcanoes, is a complex stratovolcano constructed during at least four cone-building episodes dating back to about 200,000 years ago. The 110 cu km dominantly andesitic volcanic massif is elongated in a NNE-SSW direction and surrounded by another 100 cu km ring plain of volcaniclastic debris, including the Murimoto debris-avalanche deposit on the NW flank. A series of subplinian eruptions took place between about 22,600 and 10,000 years ago, but pyroclastic flows have been infrequent. A single historically active vent, Crater Lake, is located in the broad summit region, but at least five other vents on the summit and flank have been active during the Holocene. Frequent mild-to-moderate explosive eruptions have occurred in historical time from the Crater Lake vent, and tephra characteristics suggest that the crater lake may have formed as early as 3000 years ago. Lahars produced by phreatic eruptions from the summit crater lake are a hazard to a ski area on the upper flanks and to lower river valleys.
Source: GeoNet http://www.geonet.org.n
Santa Maria | Guatemala | 14.756°N, 91.552°W | Summit elev. 3772 m
In a special report, INSIVUMEH stated that a strong explosion at Caliente cone, part of Santa María’s Santiaguito lava-dome complex, occurred at 0629 on 14 August and generated pyroclastic flows that descended the E flank. An ash plume rose about 1.3 km above the complex and drifted S and SW, causing ashfall in San Felipe (15 km SSW), Mazatenango, and Retalhuleu (27 km SW). A moderate explosion on 15 August generated an ash plume that rose 900 m and drifted E. A loud explosion at 0658 on 16 August produced a mushroom-shaped ash cloud that rose 2.5 km and drifted W and SW. Pyroclastic flows traveled 2 km down the San Isidro and Nimá II drainages. Ash fell in San Marcos (10 km SW), Loma Linda (6 km WSW), Palajunoj (18 km SSW), and possibly in multiple fincas including El Faro, La Florida (5 km S), Patzulin (SW flank), and El Patrocinio.
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.
Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e Hidrologia (INSIVUMEH) http://www.insivum
Sheveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit elev. 3283 m
KVERT reported that during 5-12 August 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/i
Sinabung | Indonesia | 3.17°N, 98.392°E | Summit elev. 2460 m
Based on satellite images, model data, ground reports from PVMBG, and the Jakarta MWO, the Darwin VAAC reported that on 15 August ash plumes from Sinabung rose to an altitude of 4.3 km (14,000 ft) a.s.l. and drifted E.
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/an
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 11-12 and 14 August ash plumes from Suwanosejima rose to altitudes of 1.8-2.7 km (6,000-9,000 ft) a.s.l. and drifted W and NW.
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.j
Tengger Caldera | Eastern Java (Indonesia) | 7.942°S, 112.95°E | Summit elev. 2329 m
Based on analyses of satellite images, the Darwin VAAC reported that on 10 August minor gas-and-steam emissions from Tengger Caldera’s Bromo cone remained localized within the caldera.
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/an
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