New activity/unrest was observed at 3 volcanoes from September 9 – 15, 2015. During the same period, ongoing activity was observed at 12 volcanoes.
New activity/unrest: Asosan, Kyushu (Japan) | Cotopaxi, Ecuador | Nevado del Ruiz, Colombia.
Ongoing activity: Batu Tara, Komba Island (Indonesia) | Cleveland, Chuginadak Island (USA) | Colima, Mexico | Dempo, Indonesia | Dukono, Halmahera (Indonesia) | Karangetang, Siau Island (Indonesia) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Sheveluch, Central Kamchatka (Russia) | Shishaldin, Fox Islands (USA) | Sinabung, Indonesia | Suwanosejima, Ryukyu Islands (Japan).
Asosan, Kyushu (Japan)
32.884°N, 131.104°E, Summit elev. 1592 m
JMA reported that during 10-11 September a small-scale eruption from Asosan’s Nakadake Crater generated a plume that rose 500 m above the crater and drifted S and SW. During fieldwork on 11 September, volcanologists observed a grayish-white plume rising from the vent and sediment deposits around the vent. On 14 September an explosion produced an ash plume that rose 2 km, prompting JMA to raise the Alert Level to 3 (on a scale of 1-5). During an overflight later that day scientists observed ashfall in the crater area, on the N flank as far as 1 km, and on the SE flank as far as 1.3 km. Ashfall was reported over a wide area including Tamana, Kumamoto City, and Yamaga (W flank). According to a news article about 30 tourists in the area were evacuated, and some flights were either canceled or re-routed. Areas within 4 km of the craters were closed. An off-white plume rose 300 m above the crater on 15 September.
Geologic summary: The 24-km-wide Asosan caldera was formed during four major explosive eruptions from 300,000 to 90,000 years ago. These produced voluminous pyroclastic flows that covered much of Kyushu. The last of these, the Aso-4 eruption, produced more than 600 cu km of airfall tephra and pyroclastic-flow deposits. A group of 17 central cones was constructed in the middle of the caldera, one of which, Nakadake, is one of Japan's most active volcanoes. It was the location of Japan's first documented historical eruption in 553 AD. The Nakadake complex has remained active throughout the Holocene. Several other cones have been active during the Holocene, including the Kometsuka scoria cone as recently as about 210 CE. Historical eruptions have largely consisted of basaltic to basaltic-andesite ash emission with periodic strombolian and phreatomagmatic activity. The summit crater of Nakadake is accessible by toll road and cable car, and is one of Kyushu's most popular tourist destinations.
0.677°S, 78.436°W, Summit elev. 5911 m
During 1-8 September IG reported that a large number of seismic events were located between 2 and 11 km below Cotopaxi's summit; seismicity consisted of long-period events, very-long-period events, tremor, and volcano-tectonic events. During 5-10 September seismic energy decreased along with the size and ash content of emissions. Analysis of ash samples showed an increase in the proportion of juvenile fragments. During an overflight on 9 September, IG scientists observed an ash plume rising 200-300 m above the crater and drifting W. Infrared measurements revealed that temperatures were well below those measured on 3 September. Glacial melting on the upper flanks continued to produce streams of meltwater on the N flank. Several new cracks in the glaciers were noted. On 11 September tremor was low; gas-and-ash emissions rose 500 m and drifted W. On 12 September gas-and-ash plumes rose 1.5 km and drifted W to NW, causing ashfall in Machachi and El Chaupi. During 14-15 September ash emissions rose 1 km. A news article from 14 September noted that area flights had been re-routed around Cotopaxi to avoid ash plumes; the most affected route was between Quito and Guayaquil.
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.
Nevado del Ruiz, Colombia
4.892°N, 75.324°W, Summit elev. 5279 m
On 14 September Servicio Geológico Colombiano’s (SGC) Observatorio Vulcanológico y Sismológico de Manizales reported continuing volcanic tremor at Nevado del Ruiz associated with gas-and-ash emissions. At 0725 an ash emission was also recorded by the webcam. 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.
Batu Tara, Komba Island (Indonesia)
7.792°S, 123.579°E, Summit elev. 748 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 15 September ash plumes from Batu Tara rose to an altitude of 1.5 km (5,000 ft) a.s.l. and drifted 185 km NW.
Geologic summary: The small isolated island of Batu Tara in the Flores Sea about 50 km N of Lembata (fomerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy's Stromboli volcano. Vegetation covers the flanks to within 50 m of the 748-m-high summit. Batu Tara lies north of the main volcanic arc and is noted for its potassic leucite-bearing basanitic and tephritic rocks. The first historical eruption, during 1847-52, produced explosions and a lava flow.
Cleveland, Chuginadak Island (USA)
52.825°N, 169.944°W, Summit elev. 1730 m
AVO reported that during 9-15 September elevated surface temperatures at Cleveland were occasionally detected in satellite images. A robust steam plume was visible on 9 September. The Aviation Color Code remained at Orange and the Volcano Alert Level remained at Watch.
Geologic summary: Beautifully symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited, dumbbell-shaped Chuginadak Island. It lies SE across Carlisle Pass strait from Carlisle volcano and NE across Chuginadak Pass strait from Herbert volcano. Cleveland is joined to the rest of Chuginadak Island by a low isthmus. The 1730-m-high Mount Cleveland is the highest of the Islands of the Four Mountains group and is one of the most active of the Aleutian Islands. The native name for Mount Cleveland, Chuginadak, refers to the Aleut goddess of fire, who was thought to reside on the volcano. Numerous large lava flows descend the steep-sided flanks. It is possible that some 18th-to-19th century eruptions attributed to Carlisle should be ascribed to Cleveland (Miller et al., 1998). In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.
19.514°N, 103.62°W, Summit elev. 3850 m
Based on satellite images, the Washington VAAC reported that during 9-10 and 12 September a gas-and-ash plume from Colima rose to altitudes of 4.6-6.7 km (15,000-22,000 ft) a.s.l. and drifted NW, WSW, and SW.
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.
4.03°S, 103.13°E, Summit elev. 3173 m
Observers at the PVMBG Dempo observation post reported that during 1 June-9 September no plumes rose from Dempo's crater and seismicity was low. On 10 September the Alert Level was lowered to 1 (on a scale from 1-4). Visitors and residents were advised not to approach the craters.
Geologic summary: Dempo is a prominent 3173-m-high stratovolcano that rises above the Pasumah Plain of SE Sumatra. The andesitic Dempo volcanic complex has two main peaks, Gunung Dempo and Gunung Marapi, constructed near the SE rim of a 3 x 5 km caldera breached to the north. The one called Dempo is slightly lower, with an elevation of 3049 m and lies at the SE end of the summit complex. The taller Marapi cone, with a summit elevation 3173 m, was constructed within a crater cutting the older Gunung Dempo edifice. Remnants of 7 craters are found at or near the summit of the complex, with volcanism migrating to the WNW with time. The large, 800 x 1100 m wide historically active summit crater cuts the NW side of Gunung Marapi (not to be confused with Marapi volcano 500 km to the NW in Sumatra) and contains a 400-m-wide lake located at the far NW end of the crater complex. Historical eruptions have been restricted to small-to-moderate explosive activity that produced ashfall near the volcano.
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 9-15 September ash plumes from Dukono rose to altitudes of 1.8-2.1 km (6,000-7,000 ft) a.s.l. and drifted 35-90 km N, NE, 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.
Karangetang, Siau Island (Indonesia)
2.78°N, 125.4°E, Summit elev. 1784 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that during 10-15 September ash plumes from Karangetang rose to altitudes of 1.8-3 km (6,000-10,000 ft) a.s.l. and drifted 35-130 km SE and NE.
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 4-11 September. Satellite images detected a thermal anomaly on the volcano on 10 September. 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 9-15 September. The lava lake continued to circulate and spatter in the Overlook vent. Webcams recorded multiple incandescent outgassing vents within Pu'u 'O'o. The June 27th NE-trending lava flow continued to be active within 4-8 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.
Sheveluch, Central Kamchatka (Russia)
56.653°N, 161.36°E, Summit elev. 3283 m
KVERT reported that during 4-11 September lava-dome extrusion onto Sheveluch’s N flank was accompanied by fumarolic activity, dome incandescence, and hot avalanches. Satellite images detected an almost 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.
Shishaldin, Fox Islands (USA)
54.756°N, 163.97°W, Summit elev. 2857 m
AVO reported that seismicity at Shishaldin continued to be elevated over background levels during 9-15 September, 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.
3.17°N, 98.392°E, Summit elev. 2460 m
PVMBG reported that during 2-9 September foggy weather sometimes prevented visual observations of Sinabung and the growing lava dome in the summit crater. Lava flows on the flanks were incandescent as far as 2 km ESE to SSE. The daily number of pyroclastic flows usually ranged from one to seven, although 11 were observed on 4 September; none were detected on 8 September. The pyroclastic flows traveled as far as 3.5 km E to SE and generated ash plumes that rose as high as 2.5 km. Seismicity consisted of avalanche signals, low-frequency and hybrid events, tremor, tectonic events, and volcanic earthquakes. The Alert Level remained at 4 (on a scale of 1-4), indicating that people within 7 km of the volcano on the SSE sector, and within 6 km in the ESE sector, should evacuate. BNPB reported that on 15 September pyroclastic flows traveled as far as 4 km ESE. Ash plumes rose as high as 3 km and drifted E, causing thick ashfall deposits in Berastagi, Kabanjahe, and surrounding areas. The number of displaced people totaled 2,572.
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.
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 on 13 September ash plumes from Suwanosejima rose to an altitude of 1.8 km (6,000 ft) a.s.l. and drifted 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 persons live on the island.
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