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The Watchers – Active volcanoes in the world: May 2 – May 8, 2012

May 10, 2012
This report covers active volcanoes recorded from May 2 – May 8, 2012 based on Smithsonian/USGS criteria. New unrest has been noticed around 5 volcanoes, ongoing activity was reported for 8 volcanoes. BATU TARA Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m Based on analyses of satellite imagery, the Darwin VAAC reported that during 2-4 May ash plumes from Batu Tara rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 37 km NW. Geologic summary: The small isolated...
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This report covers active volcanoes recorded from May 2 – May 8, 2012 based on Smithsonian/USGS criteria. New unrest has been noticed around 5 volcanoes, ongoing activity was reported for 8 volcanoes.

BATU TARA

Komba Island (Indonesia) 7.792°S, 123.579°E; summit elev. 748 m

Based on analyses of satellite imagery, the Darwin VAAC reported that during 2-4 May ash plumes from Batu Tara rose to an altitude of 2.4 km (8,000 ft) a.s.l. and drifted 37 km NW.

Geologic summary: The small isolated island of Batu Tara in the Flores Sea about 50 km north of Lembata (formerly Lomblen) Island contains a scarp on the eastern side similar to the Sciara del Fuoco of Italy’s Stromboli volcano. Vegetation covers the flanks of Batu Tara 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 historicaleruption from Batu Tara, during 1847-52, produced explosions and a lava flow.

CLEVELAND

Chuginadak Island 52.825°N, 169.944°W; summit elev. 1730 m

Based on analyses of satellite images, AVO reported on 4 May that the small lava dome recently emplaced in Cleveland’s summit crater had been destroyed late in the previous week, but the explosion was too small to be detected by distant infrasound and seismic networks. A small new dome was extruded following the explosion and was the fifth dome to be observed in this eruptive episode which began in July 2011. During 4-5 May two small explosions were detected. No ash was observed with the mostly-cloudy conditions. Satellite observations were obscured by clouds during 6-8 May.

Geologic summary: Symmetrical Mount Cleveland stratovolcano is situated at the western end of the uninhabited dumbbell-shaped Chuginadak Island in the east-central Aleutians. The 1,730-m-high stratovolcano is the highest of the Islands of Four Mountains group and is one of the most active in the Aleutians. Numerous large lava flows descend its flanks. It is possible that some 18th to 19th century eruptions attributed to Carlisle (a volcano located across the Carlisle Pass Strait to the NW) should be ascribed to Cleveland. In 1944 Cleveland produced the only known fatality from an Aleutian eruption. Recent eruptions from Mt. Cleveland have been characterized by short-lived explosive ash emissions, at times accompanied by lava fountaining and lava flows down the flanks.

PAGO

New Britain 5.58°S, 150.52°E; summit elev. 742 m

Based on analyses of satellite imagery, the Darwin VAAC reported that ash-and-steam plumes from Pago rose to an altitude of 13.7 km (45,000 ft) a.s.l. and drifted 75 km NE.

Geologic summary: Pago is a young post-caldera cone that was constructed within the 5.5 x 7.5 km Witori caldera. Extensive pyroclastic-flow deposits are associated with formation of the caldera about 3,300 years ago. The gently sloping outer flanks of Witori volcano consist primarily of dacitic pyroclastic-flow and airfall deposits produced during a series of five major explosive eruptions from about 5,600 to 1,200 years ago. The Buru caldera, which may have formed around the same time, cuts the SW flank of Witori volcano. The post-caldera cone of Witori, Mount Pago, may have formed less than 350 years ago and has grown to a height above that of the Witori caldera rim. A series of nine dacitic lava flows from Pago covers much of the caldera floor. The youngest of these was erupted during the 20th century and banks against the eastern caldera wall.

POPOCATEPETL

México 19.023°N, 98.622°W; summit elev. 5426 m

CENAPRED reported that during 2-3 May activity at Popocatépetl increased significantly. Spasmodic tremor was detected along with a dense and continuous plume of gas and ash that drifted W, NW, and NNE. Ash fell in multiple areas, including Amecameca (20 km NW), Atlautla, Ozumba (18 km W), Ecatzingo (15 km SW), Chalco (35 km NW), and some parts of SE México City (70 km NW). On 3 May gas-and-ash plumes rose 1.5 km above the crater and drifted W and NE. Incandescent fragments ejected from the crater landed on the flanks as far as 800 m away. Explosion-generated gas-and-ash plumes the next day rose 2.5 km above the crater and drifted NW. Spasmodic tremor was detected along with a dense and continuous plume of gas and ash that drifted WNW. Later that day gas-and-ash plumes rose 1 km. During 5-6 May gas-and-ash plumes rose 1.5 km above the crater and drifted N, NE, and E. Light ashfall was reported in Atlixco (25 km SE), San Juan Tianguismanalco (22 km SE), Tochimilco (16 km SSE), San Pedro Benito Juárez (10 km SE), and San Nicolás de los Ranchos (16 km ENE). During 5-7 May incandescent fragments ejected from the crater landed on the flanks as far as 500 m away. A gas-and-ash plume drifted ESE on 7 May. The next day activity remained high; seismic events were accompanied by dense and continuous plumes of steam, gas, and ash that drifted mainly ESE. The Alert Level remained at Yellow Phase Three.

Geologic summary: Popocatépetl, whose name is the Aztec word for smoking mountain, towers to 5,426 m 70 km SE of Mexico City and is North America’s second-highest volcano. Frequent historical eruptions have been recorded since the beginning of the Spanish colonial era. A small eruption on 21 December 1994 ended five decades of quiescence. Since 1996 small lava domes have incrementally been constructed within the summit crater and destroyed by explosive eruptions. Intermittent small-to-moderate gas-and-ash eruptions have continued, occasionally producing ashfall in neighboring towns and villages.

SEMERU

Eastern Java (Indonesia) 8.108°S, 112.92°E; summit elev. 3676 m

CVGHM reported that during 1-29 February multiple pyroclastic flows from Semeru traveled 500 and 2,500 m into the Besuk Kembar and Besuk Kobokan rivers (on the S flank), respectively. During 1 February-30 April dense gray-to-white plumes rose 100-500 m above Jongring Seloko crater and drifted W and N. Incandescence was visible up to 50 m above the crater during 1 February-31 March. Seismicity decreased from March to April. Observations indicated that the lava dome grew in April. On 2 May CVGHM lowered the Alert Level to 2 (on a scale of 1-4) and reminded the public not to approach the crater within a 4-km radius.

Geologic summary: Semeru is the highest volcano on Java and one of its most active. The symmetricalstratovolcano rises abruptly to 3,676 m above coastal plains to the S and lies at the southern end of a volcanic massif extending N to the Tengger caldera. Semeru has been in almost continuous eruption since 1967. Frequent small-to-moderate Vulcanian eruptions have accompanied intermittent lava dome extrusion, and periodicpyroclastic flows and lahars have damaged villages below the volcano. A major secondary lahar on 14 May 1981 caused more than 250 deaths and damaged 16 villages.

Ongoing Activity

DUKONO

Halmahera 1.68°N, 127.88°E; summit elev. 1335 m

Based on analyses of satellite imagery, the Darwin VAAC reported that during 8-9 May ash plumes from Dukono rose to an altitude of 3 km (10,000 ft) a.s.l. and drifted 75 km SE.

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 N-flank cone of Gunung Mamuya. Dukono is a complex volcano presenting a broad, low profile with multiple summit peaks and overlapping craters. Malupang Wariang, 1 km SW of Dukono’s summit crater complex, contains a 700 x 570 m crater that has also been active during historical time.

KARYMSKY

Eastern Kamchatka (Russia) 54.05°N, 159.45°E; summit elev. 1536 m

KVERT reported that moderate seismic activity from Karymsky continued to be detected during 27 April-4 May, and indicated that possible ash plumes rose to an altitude of 2.3 km (7,600 ft) a.s.l. during 26-27 April and 2 May. Satellite imagery showed a gas-and-steam plume drifting 65 km SE on 27 April; a thermal anomaly was present during 27, 29, and 30 April and 2-3 May. The Aviation Color Code remained at Orange.

Geologic summary: Karymsky, the most active volcano of Kamchatka’s eastern volcanic zone, is a symmetricalstratovolcano constructed within a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon years ago. Construction of the Karymsky stratovolcano began about 2,000 years later. The latest eruptive period began about 500 years ago, following a 2,300-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. Most seismicity preceding Karymsky eruptions has originated beneath Akademia Nauk caldera, which is located immediately S of Karymsky volcano and erupted simultaneously with Karymsky in 1996.

KILAUEA

Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m

During 2-8 May HVO reported that the circulating lava lake periodically rose and fell in the deep pit within Kilauea’s Halema’uma’u Crater. Frequent measurements indicated that the gas plume from the vent continued to deposit variable amounts of ash, and occasionally fresh spatter from an active source at the SE edge of the lava lake, onto nearby areas. Incandescence was visible from both a lava pond in a small pit on the E edge and a small spatter cone on the SE edge of the Pu’u ‘O’o crater floor. Geologists observed slowly advancing lava flows on 4 May that were about 1.1 km from the coast, not reaching as far as previous flows on the coastal plain over the past month. On 5 May further collapse of the pit on the E edge of the Pu’u ‘O’o crater floor led to much brighter incandescence from that area. Lava flows on the coastal plain stalled while new lava flows high on the pali formed on 5 May, vigorously advancing from the base of the pali to more than halfway across the flow field during 5-8 May.

Geologic summary: Kilauea, one of five coalescing volcanoes that comprise the island of Hawaii, is one of the world’s most active volcanoes. Eruptions at Kilauea originate primarily from the summit caldera or along one of the lengthy E and SW rift zones that extend from the caldera to the sea. About 90% of the surface of Kilauea is formed of lava flows less than about 1,100 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.

NEVADO DEL RUIZ

Colombia 4.895°N, 75.322°W; summit elev. 5321 m

According to INGEOMINAS, the Observatorio Vulcanológico and Sismológico de Manizales reported that during 1-2 May both satellite images and field observers indicated that steam and sulfur dioxide emissions rose from Nevado del Ruiz. Seismicity continued to decrease. On 3 May the Alert Level was lowered to 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 summit caldera of an older Ruiz volcano. The 1-km-wide, 240-m-deep Arenas crater occupies the summit. Steep headwalls of massive landslides cut the flanks of Nevado del Ruiz. 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.

SAKURA-JIMA

Kyushu 31.585°N, 130.657°E; summit elev. 1117 m

JMA reported that during 1-7 May explosive eruptions from Sakura-jima’s Showa Crater occurred 17 times and ejected tephra as far as 1.3 km from the crater. Very small eruptions from Minami-dake Crater occurred on 3 and 5 May. Based on information from JMA, the Tokyo VAAC reported that during 3-4 and 6-8 May explosions produced plumes that rose to altitudes of 1.5-3.7 km (5,000-12,000 ft) a.s.l. and drifted S, SE, and E. Ash was observed in satellite imagery on 3 May. A pilot observed an ash plume on 7 May that rose to an altitude of 2.4 (8,000 ft) a.s.l. and drifted SE.

Geologic summary: Sakura-jima, one of Japan’s most active volcanoes, is a post-caldera cone of the Aira calderaat the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow was associated with the formation of the 17 x 23-km-wide Aira caldera about 22,000 years ago. The construction of Sakura-jima began about 13,000 years ago and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kita-dake summit cone ended about 4,850 years ago, after which eruptions took place at Minami-dake. Frequent historical eruptions, recorded since the 8th century, have depositedash 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.

SHIVELUCH

Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m

KVERT reported that explosive activity at Shiveluch continued during 27 April-4 May. Ground-based observers and satellite imagery indicated that a viscous lava flow continued to effuse in the crater formed during a 2010 eruption and was accompanied by fumarolic activity. Seismic data and visual observations showed that ash plumes rose to altitudes of 4 and 5.4 km (13,200 and 17,800 ft) a.s.l. on 26 April and 1 May, respectively. Satellite imagery showed a weak thermal anomaly on the lava dome during 28-29 April and on 1 and 3 May. Explosions on 1 May produced ash plumes that rose to an altitude of 5 km (16,400 ft) a.s.l.; an ash cloud was observed in satellite imagery drifting 270 km NE that same day.

Geologic summary: The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group and forms one of Kamchatka’s largest and most active volcanoes. The currently active Molodoy Shiveluch lava-dome complex was constructed during the Holocene within a large breached caldera formed by collapse of the massive late-Pleistocene Strary Shiveluch volcano. At least 60 large eruptions of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Frequent collapses of lava-dome complexes, most recently in 1964, have produced large debris avalanches whose deposits cover much of the floor of the breached caldera. Intermittent explosive eruptions began in the 1990s from a new lava dome that began growing in 1980. The largest historical eruptions from Shiveluch occurred in 1854 and 1964.

SOUFRIERE HILLS

Montserrat 16.72°N, 62.18°W; summit elev. 915 m

MVO reported that the cloud cover which often obscures views of the Soufrière Hills lava dome cleared for a short period on 5 May, revealing multiple areas of incandescence, the same ones first observed on 11 November 2011. Some of the areas were visible to the naked eye while more were visible in a long-exposure photograph. Many of the bright areas were related to fumaroles. The Hazard Level remained at 2 (on a scale of 1-5).

Geologic summary: The complex dominantly andesitic Soufrière Hills volcano occupies the southern half of the island of Montserrat. The summit area consists primarily of a series of lava domes emplaced along an ESE-trending zone. English’s Crater, a 1-km-wide crater breached widely to the E, was formed during an eruption about 4,000 years ago in which the summit collapsed, producing a large submarine debris avalanche. Block-and-ash flow and surge deposits associated with dome growth predominate in flank deposits at Soufrière Hills. Non-eruptive seismic swarms occurred at 30-year intervals in the 20th century, but with the exception of a 17th-century eruption that produced the Castle Peak lava dome, no historical eruptions were recorded on Montserrat until 1995. Long-term small-to-moderate ash eruptions beginning in that year were later accompanied by lava-dome growth andpyroclastic flows that forced evacuation of the southern half of the island and ultimately destroyed the capital city of Plymouth, causing major social and economic disruption.

TUNGURAHUA

Ecuador 1.467°S, 78.442°W; summit elev. 5023 m

IG reported that during 2-8 May visual observations of Tungurahua were often limited due to cloud cover. Explosions were heard in Baños on 2 May and ashfall was reported in Pillate (7 km W) the next day. On 4 May steam emissions rose from the crater and an ash plume drifted W. Ashfall was reported in Pillate and Choglontus (SW). On 6 May explosions were detected and roaring was heard. An ash plume rose 1.5 km above the crater and drifted WSW. Ashfall covered houses and pastures in Bilbao (8 km W) and Pillate. Ash also fell in Chacauco. An ash plume drifted W on 7 May; ashfall was reported in Bilbao, Pillate, Mapayacu (SW), Cevallos (23 km NW), Pillate (7 km W), and Chacauco.

Geologic summary: The steep-sided Tungurahua stratovolcano towers more than 3 km above its northern base. It sits ~140 km S of Quito, Ecuador’s capital city, and is one of Ecuador’s most active volcanoes. Historical eruptions have all originated from the summit crater. They have been accompanied by strong explosions and sometimes bypyroclastic flows and lava flows that reached populated areas at the volcano’s base. The last major eruption took place from 1916 to 1918, although minor activity continued until 1925. The latest eruption began in October 1999 and prompted temporary evacuation of the town of Baños on the N side of the volcano.

Source: Global Volcanism Program

Featured image: USGS – Pago, New Britain 2002

The Watchers – Active volcanoes in the world: May 2 – May 8, 2012.

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