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Smithsonian / USGS Weekly Volcanic Activity Report 30 April-6 May 2014
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Smithsonian / USGS Weekly Volcanic Activity Report
30 April-6 May 2014
Sally Kuhn Sennert - Weekly Report Editor (kuhns@si.edu)
URL: http://www.volcano.si.edu/reports_weekly.cfm
New Activity/Unrest: Ahyi, Mariana Islands (USA) | Merapi, Central Java (Indonesia) | Slamet, Central Java (Indonesia) | Soputan, Sulawesi (Indonesia)
Ongoing Activity: Aira, Kyushu (Japan) | Bagana, Bougainville (Papua New Guinea) | Chirinkotan, Kuril Islands (Russia) | Chirpoi, Kuril Islands (Russia) | Dukono, Halmahera (Indonesia) | Etna, Sicily (Italy) | Karymsky, Eastern Kamchatka (Russia) | Kilauea, Hawaiian Islands (USA) | Reventador, Ecuador | Semeru, Eastern Java (Indonesia) | Shishaldin, Fox Islands (USA) | Shiveluch, Central Kamchatka (Russia) | Ubinas, Peru
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
Ahyi | Mariana Islands (USA) | 20.42°N, 145.03°E | Summit elev. -137 m
Seismic stations on Pagan, Sarigan, Anatahan, and Saipan started recording signals on 24 April that continued at least through 2 May. The source had not been confirmed, but is thought to be at or near the Ahyi seamount. During 4-5 May a helicorder plot from a station on Pagan showed explosive signals at a rate of 20 per hour.
Geologic Summary. Ahyi seamount is a large conical submarine volcano that rises to within 137 m of the sea surface about 18 km SE of the island of Farallon de Pajaros (Uracas) in the northern Marianas. Water discoloration has been observed over the submarine volcano, and in 1979 the crew of a fishing boat felt shocks over the summit area of the seamount followed by upwelling of sulfur-bearing water. On April 24-25, 2001 an explosive submarine eruption was detected seismically from a seismic station on Rangiroa Atoll, Tuamotu Archipelago. The event was well constrained (+/- 15 km) at a location near the southern base of Ahyi; the summit of the seamount lies within the location uncertainty.
Sources: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program http://volcanoes.usgs.gov/nmi/activity/index.php;
Matthew Haney, Alaska Volcano Observatory via Bill Chadwick, Oregon State University's Marine Science Center and NOAA/PMEL EOI Program, personal communication
Merapi | Central Java (Indonesia) | 7.542°S, 110.442°E | Summit elev. 2968 m
PVMBG reported that during 20-29 April seismicity at Merapi increased and thumping sounds were heard within an 8 km radius. On 25 April white fumarolic plumes rose 450 m and drifted W. The Alert Level was raised to 2 (on a scale of 1-4) on 29 April.
Geologic Summary. Merapi, one of Indonesia's most active volcanoes, lies in one of the world's most densely populated areas and dominates the landscape immediately north of the major city of Yogyakarta. Merapi is the youngest and southernmost of a volcanic chain extending NNW to Ungaran volcano. Growth of Old Merapi volcano beginning during the Pleistocene ended with major edifice collapse perhaps about 2000 years ago, leaving a large arcuate scarp cutting the eroded older Batulawang volcano. Subsequently growth of the steep-sided Young Merapi edifice, its upper part unvegetated due to frequent eruptive activity, began SW of the earlier collapse scarp. Pyroclastic flows and lahars accompanying growth and collapse of the steep-sided active summit lava dome have devastated cultivated lands on the volcano's western-to-southern flanks and caused many fatalities during historical time. The volcano is the object of extensive monitoring efforts by the Merapi Volcano Observatory.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) also known CVGHM http://www.vsi.esdm.go.id/
Slamet | Central Java (Indonesia) | 7.242°S, 109.208°E | Summit elev. 3428 m
PVMBG reported that during 29 March-30 April seismicity at Slamet increased and inflation was detected. Observers noted that white plumes rose as high as 800 m above the crater, and dense gray ash plumes rose as high as 2 km and drifted E and W. During 19-25 April the plumes were gray to brown, and ejected material was deposited on the flanks 300 m from the crater. Crater incandescence was noted. During 26-30 April the ash plumes continued to have a brownish component, and material fell in areas within 1.5 km W. The crater was again incandescent. Rumbling noises were reported and windows at the Slamet observation post rattled during 27-29 April. The Alert Level was raised to 3 (on a scale of 1-4) on 30 April. Residents and tourists were warned not approach the crater within a radius of 4 km.
Geologic Summary. Slamet, Java's second highest volcano at 3428 m and one of its most active, has a cluster of about three dozen cinder cones on its lower SE-NE flanks and a single cinder cone on the western flank. Slamet is composed of two overlapping edifices, an older basaltic-andesite to andesitic volcano on the west and a younger basaltic to basaltic-andesite one on the east. Gunung Malang II cinder cone on the upper eastern flank on the younger edifice fed a lava flow that extends 6 km to the east. Four craters occur at the summit of Gunung Slamet, with activity migrating to the SW over time. Historical eruptions, recorded since the 18th century, have originated from a 150-m-deep, 450-m-wide, steep-walled crater at the western part of the summit and have consisted of explosive eruptions generally lasting a few days to a few weeks.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) also known CVGHM http://www.vsi.esdm.go.id/
Soputan | Sulawesi (Indonesia) | 1.108°N, 124.73°E | Summit elev. 1784 m
PVMBG reported that during April diffuse white plumes from Soputan rose at most 100 m. During 30 April-1 May seismic activity significantly increased, characterized by signals indicating deep volcanic earthquakes and avalanches. On 1 May the Alert Level was raised to 3 (on a scale of 1-4). Residents and tourists were advised not to approach the craters within a radius of 6.5 km.
Geologic Summary. The small Soputan stratovolcano on the southern rim of the Quaternary Tondano caldera on the northern arm of Sulawesi Island is one of Sulawesi's most active volcanoes. The youthful, largely unvegetated volcano rises to 1784 m and is located SW of Sempu volcano. It was constructed at the southern end of a SSW-NNE trending line of vents. During historical time the locus of eruptions has included both the summit crater and Aeseput, a prominent NE-flank vent that formed in 1906 and was the source of intermittent major lava flows until 1924.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) also known 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 during 28 April-2 May four explosions from Showa Crater at Aira Caldera€™s Sakurajima volcano ejected tephra as far as 500 m. Incandescence from the crater was detected at night during 28-30 April. The Alert Level remained at 3 (on a scale of 1-5). The Tokyo VAAC reported that during 30 April-3 May and on 5 May plumes rose to altitudes of 1.8-3 km (6,000-10,000 ft) a.s.l. and drifted E, SE, and SW. On 30 April a pilot observed an ash plume that rose to an altitude of 2.7 km (9,000 ft) a.s.l.
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.
Sources: Tokyo Volcanic Ash Advisory Center (VAAC) http://ds.data.jma.go.jp/svd/vaac/data/vaac_list.html;
Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/
Bagana | Bougainville (Papua New Guinea) | 6.14°S, 155.195°E | Summit elev. 1750 m
Based on analyses of satellite imagery and wind data, the Darwin VAAC reported that on 1 May an ash plume from Bagana rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted over 45 km SSE.
Geologic Summary. Bagana volcano, occupying a remote portion of central Bougainville Island, is one of Melanesia's youngest and most active volcanoes. Bagana is a massive symmetrical, roughly 1750-m-high lava cone largely constructed by an accumulation of viscous andesitic lava flows. The entire lava cone could have been constructed in about 300 years at its present rate of lava production. Eruptive activity at Bagana is frequent and is 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.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
Chirinkotan | Kuril Islands (Russia) | 48.98°N, 153.48°E | Summit elev. 724 m
SVERT reported that satellite images of Chirinkotan showed a thermal anomaly on 29 April. Cloud cover obscured views during 30 April-5 May. The Aviation Color Code remained at Yellow.
Geologic Summary. The small, mostly unvegetated 3-km-wide island of Chirinkotan occupies the far end of an E-W-trending volcanic chain that extends nearly 50 km west of the central part of the main Kuril Islands arc. Chirinkotan is the emergent summit of a volcano that rises 3000 m from the floor of the Kuril Basin. A small 1-km-wide caldera about 300-400 m deep is open to the SE. Lava flows from a cone within the breached crater reached the north shore of the island. Historical eruptions have been recorded at Chirinkotan since the 18th century. Fresh lava flows also descended the SE flank of Chirinkotan during an eruption in the 1880s that was observed by the English fur trader Captain Snow.
Source: Sakhalin Volcanic Eruption Response Team (SVERT) http://www.imgg.ru/?id_d=659
Chirpoi | Kuril Islands (Russia) | 46.525°N, 150.875°E | Summit elev. 742 m
SVERT reported that satellite images over Snow, a volcano of Chirpoi, detected a thermal anomaly during 29-30 April. Cloud cover obscured views during 1-5 May. 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. Two volcanoes on Chirpoi Island have been historically active. 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
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 30 April-6 May ash plumes from Dukono rose to altitudes of 2.4-3 km (8,000-10,000 ft) a.s.l. The plumes drifted 35-185 km SE, E, SW, and W on 30 April and during 3-6 May but stayed in the vicinity of the volcano on the other days.
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. 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.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) ftp://ftp.bom.gov.au/anon/gen/vaac/
Etna | Sicily (Italy) | 37.734°N, 15.004°E | Summit elev. 3330 m
INGV reported that during the morning of 22 April sporadic and weak Strombolian activity resumed at Etna's New Southeast Crater (NSEC) and continued for the next few days. Some explosions ejected incandescent pyroclastic material out of the crater and onto the upper S and SE flanks of the cone. A few small collapses occurred on the cone's unstable E flank. The frequency and intensity of Strombolian explosions slightly increased late in the evening on 30 April. Degassing at the Northeast Crater also increased and thermal anomalies were detected by a camera.
Weak Strombolian activity continued to be detected through 1 May. During the night of 2-3 May incandescence was caused by weak high-temperature gas emissions and/or Strombolian explosions. The activity intensified on 4 May and some of the explosions ejected incandescent pyroclastic material onto the high S and SE parts of the NSEC cone.
Geologic Summary. Mount Etna, towering above Catania, Sicily's second largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy. The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km horseshoe-shaped caldera open to the east. Two styles of eruptive activity typically occur at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater (the latter formed in 1978). Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by strombolian eruptions at the upper end). Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank.
Source: Sezione di Catania - Osservatorio Etneo (INGV) http://www.ct.ingv.it/
Karymsky | Eastern Kamchatka (Russia) | 54.05°N, 159.45°E | Summit elev. 1536 m
KVERT reported that Vulcanian and Strombolian activity continued at Karymsky during 25 April-2 May. Satellite images detected a thermal anomaly on the volcano on 27 and 30 April and 1 May; cloud cover obscure views on the other days. 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, which is located immediately south of Karymsky volcano. The caldera enclosing Karymsky volcano formed about 7600-7700 radiocarbon years ago; construction of the Karymsky stratovolcano began about 2000 years later. The latest eruptive period began about 500 years ago, following a 2300-year quiescence. Much of the cone is mantled by lava flows less than 200 years old. Historical eruptions have been vulcanian or vulcanian-strombolian with moderate explosive activity and occasional lava flows from the summit crater.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
Kilauea | Hawaiian Islands (USA) | 19.421°N, 155.287°W | Summit elev. 1222 m
During 30 April-6 May HVO reported that the circulating lava lake occasionally rose and fell in the deep pit within Kilauea's Halema'uma'u Crater. Gas emissions remained elevated. The plume from the vent continued to deposit variable amounts of ash, spatter, and Pele's hair onto nearby areas; smaller particles may have been dropped several kilometers away.
At Pu'u 'O'o Crater, glow emanated from spatter cones on the N and S portions of the crater floor, and from the lava pond in the NE spatter cone. The S spatter cone periodically erupted lava flows that traveled N and SE beyond the crater rim. During 5-6 May the N cone ejected spatter and a small lava flow. The Kahauale€™a 2 lava flow continued to advance, with breakouts from the main stalled lobe, and burned adjoining forest. On 5 May geologists mapped the farthest point of activity, 8.6 km NE of Pu€™u 'O'o.
Geologic Summary. Kilauea volcano, which overlaps the east flank of the massive Mauna Loa shield volcano, has been Hawaii's most active volcano during historical time. Eruptions of Kilauea are prominent in Polynesian legends; written documentation extending back to only 1820 records frequent summit and flank lava flow eruptions that were interspersed with periods of long-term lava lake activity that lasted until 1924 at Halemaumau crater, within the summit caldera. The 3 x 5 km caldera was formed in several stages about 1500 years ago and during the 18th century; eruptions have also originated from the lengthy East and SW rift zones, which extend to the sea on both sides of the volcano. About 90% of the surface of the basaltic shield volcano is formed of lava flows less than about 1100 years old; 70% of the volcano's surface is younger than 600 years. A long-term eruption from the East rift zone that began in 1983 has produced lava flows covering more than 100 sq km, destroying nearly 200 houses and adding new coastline to the island.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO) http://hvo.wr.usgs.gov/
Reventador | Ecuador | 0.077°S, 77.656°W | Summit elev. 3562 m
IG reported that a small pyroclastic flow traveled a few meters below Reventador€™s crater on 29 April. Cloud cover occasionally prevented visual observations during 30 April-6 May. An ash plume rose 3-4 km and drifted W on 1 May, and a steam plume with some ash rose less than 1 km the next day. People in Camp San Rafael (8 km ESE) reported that an explosion at 2040 on 4 May ejected a large amount of incandescent material onto the flanks, and generated an ash plume that rose 4-5 km above the crater and drifted NW. Explosions on 5 May produced ash plumes that rose 4 km. At 0925 an explosion vibrated windows in the camp. On 6 May explosions again rattled windows in the camp and a gas plume was observed rising 1 km and drifted W.
Geologic Summary. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well east of the principal volcanic axis. The forested, dominantly andesitic Volcán El Reventador stratovolcano rises to 3562 m above the jungles of the western Amazon basin. A 4-km-wide caldera widely breached to the east was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1300 m above the caldera floor to a height comparable to the caldera rim. Reventador has been the source of numerous lava flows as well as explosive eruptions that were visible from Quito in historical time. Frequent lahars in this region of heavy rainfall have constructed a debris plain on the eastern floor of the caldera. The largest historical eruption at Reventador took place in 2002, producing a 17-km-high eruption column, pyroclastic flows that traveled up to 8 km, and lava flows from summit and flank vents.
Source: Instituto GeofÃsico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/
Semeru | Eastern Java (Indonesia) | 8.108°S, 112.92°E | Summit elev. 3676 m
PVMBG reported that during 1 March-27 April white-and-gray plumes rose 100-400 m above Semeru€™s Jongring Seloko crater and drifted W; during April eight €œeruption€ plumes rose 300-500 m. On 26 April at 1852 and 1934, and on 27 April at 0500, incandescent rockslides from the lava dome traveled as far as 300 m down the S flank. As of 28 April the Alert Level remained at 2 (on a scale of 1-4) and the public was reminded not to approach the crater within a 4-km radius.
Geologic Summary. Semeru, the highest volcano on Java, and one of its most active, lies at the southern end of a volcanic massif extending north to the Tengger caldera. The steep-sided volcano, also referred to as Mahameru (Great Mountain), rises abruptly to 3676 m above coastal plains to the south. Gunung Semeru was constructed south of the overlapping Ajek-ajek and Jambangan calderas. A line of lake-filled maars was constructed along a N-S trend cutting through the summit, and cinder cones and lava domes occupy the eastern and NE flanks. Summit topography is complicated by the shifting of craters from NW to SE. Frequent 19th and 20th century eruptions were dominated by small-to-moderate explosions from the summit crater, with occasional lava flows and larger explosive eruptions accompanied by pyroclastic flows that have reached the lower flanks of the volcano. Semeru has been in almost continuous eruption since 1967.
Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) also known CVGHM http://www.vsi.esdm.go.id/
Shishaldin | Fox Islands (USA) | 54.756°N, 163.97°W | Summit elev. 2857 m
AVO reported that although cloud cover occasionally prevented web-cam and satellite observations of Shishaldin's summit area during 30 April-6 May, periods of elevated surface temperatures and minor steaming were observed. 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, Shishaldin 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. Shishaldin contains 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.
Source: US Geological Survey Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/
Shiveluch | Central Kamchatka (Russia) | 56.653°N, 161.36°E | Summit elev. 3283 m
KVERT reported that during 25 April-2 May lava-dome extrusion onto Shiveluch€™s SE flank was accompanied by ash explosions, incandescence, hot avalanches, and fumarolic activity. Satellite images showed a bright thermal anomaly daily. The Aviation Color Code remained at Orange.
Geologic Summary. The high, isolated massif of Shiveluch volcano (also spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya volcano group. The 1300 cu km Shiveluch 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 of Shiveluch have occurred during the Holocene, making it the most vigorous andesitic volcano of the Kuril-Kamchatka arc. Widespread tephra layers from these eruptions have provided valuable time markers for dating volcanic events in Kamchatka. Frequent collapses of dome complexes, most recently in 1964, have produced debris avalanches whose deposits cover much of the floor of the breached caldera.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
Ubinas | Peru | 16.355°S, 70.903°W | Summit elev. 5672 m
IGP's Observatorio Volcanologico de Arequipa (IGP-OVA) and Observatorio Vulcanológico del INGEMMET (OVI) reported that during 30 April-1 May seismic activity at Ubinas increased significantly, and then declined through 6 May. Explosions generated ash plumes that rose 0.2-3 km above the crater and drifted in multiple directions, especially to the S, SE, E, and NE. Ash fell in various towns downwind of the plumes including Querapi (4 km S), Ubinas (6.5 km SSE), Escacha, Anascapa, San Miguel, and Lloque. On 4 May minor amounts of ash fell throughout the Ubinas valley, more than 15 km away. Although sulfur dioxide emissions had been declining since the peak on 15 April (4,873 tons per day) they continued to be high at more than 1,000 tons per day; villages downwind reported strong sulfur odors.
Geologic Summary. A small, 1.4-km-wide caldera cuts the top of Ubinas, Peru's most active volcano, giving it a truncated appearance. Ubinas is the northernmost of three young volcanoes located along a regional structural lineament about 50 km behind the main volcanic front of Perú. The growth and destruction of Ubinas I volcano was followed by construction of Ubinas II volcano beginning in the mid-Pleistocene. The upper slopes of the andesitic-to-rhyolitic Ubinas II stratovolcano are composed primarily of andesitic and trachyandesitic lava flows and steepen to nearly 45 degrees. The steep-walled, 150-m-deep summit caldera contains an ash cone with a 500-m-wide funnel-shaped vent that is 200 m deep. Debris-avalanche deposits from the collapse of the SE flank of Ubinas about 3700 years ago extend 10 km from the volcano. Widespread plinian pumice-fall deposits from Ubinas include one of Holocene age about 1000 years ago. Holocene lava flows are visible on the volcano's flanks, but historical activity, documented since the 16th century, has consisted of intermittent minor-to-moderate explosive eruptions.
Sources: Instituto GeofÃsico del Perú (IGP) http://www.igp.gob.pe/;
Instituto Geológico Minero y Metalúrgico (INGEMMET) http://www.ingemmet.gob.pe/
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Sally Kuhn Sennert
SI/USGS Weekly Volcanic Activity Report Editor
Global Volcanism Program
http://www.volcano.si.edu/reports/usgs/
Smithsonian Institution, National Museum of Natural History
Department of Mineral Sciences, MRC-119
Washington, D.C., 20560
Phone: 202.633.1805
Fax: 202.357.2476
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