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SI/USGS Weekly Volcanic Activity Report 7-13 April 2010
From: Sally Kuhn Sennert <kuhns@xxxxxx>
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SI/USGS Weekly Volcanic Activity Report
7-13 April 2010
Sally Kuhn Sennert - Weekly Report Editor
kuhns@xxxxxx
URL: http://www.volcano.si.edu/reports/usgs/
New Activity/Unrest: | Egon, Flores Island (Indonesia) | Etna, Sicily (Italy) | Eyjafjöll, Southern Iceland | Gaua, Banks Islands (SW Pacific) | Miyake-jima, Izu Islands (Japan) | Redoubt, Southwestern Alaska | Reventador, Ecuador
Ongoing Activity: | Arenal, Costa Rica | Batu Tara, Komba Island (Indonesia) | Dukono, Halmahera | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) | Kliuchevskoi, Central Kamchatka (Russia) | Popocatépetl, México | Rabaul, New Britain | Sakura-jima, Kyushu | Shiveluch, Central Kamchatka (Russia) | Soufrière Hills, Montserrat
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
EGON Flores Island (Indonesia) 8.67°S, 122.45°E; summit elev. 1703 m
CVGHM reported that on 7 April the Alert Level for Egon was raised from 1 to 2 (on a scale of 1-4) due to a marked increase in seismic activity since 28 March. Small steam plumes normally rose 10 m above the crater.
Geologic Summary. Gunung Egon volcano sits astride the narrow waist of eastern Flores Island. The barren, sparsely vegetated summit region has a 350-m-wide, 200-m-deep crater that sometimes contains a lake. Other small crater lakes occur on the flanks of the 1,703-m-high volcano. A lava dome forms the southern 1,671-m-high summit. Reports of historical eruptive activity are inconclusive. A column of "smoke" was often observed above the summit during 1888-1891 and in 1892. Strong "smoke" emission in 1907 reported by Sapper (1917) was considered by the Catalog of Active Volcanoes of the World (Neumann van Padang, 1951) to be an historical eruption, but Kemmerling (1929) noted that this was likely confused with an eruption on the same date and time from Lewotobi Lakilaki volcano.
Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM) http://portal.vsi.esdm.go.id/joomla/
ETNA Sicily (Italy) 37.734°N, 15.004°E; summit elev. 3330 m
INGV-CT reported that on 8 April a dozen low-frequency events located near the summit of Etna were detected by the seismic network. Concurrently, a dark-colored ash plume rose 1 km from a pit crater located at the E base of the Southeast Crater and drifted NE. Dark emissions from the central crater were also seen a short time later. Ashfall was reported from a few local areas. On 9 April intense gas emissions were noted at the pit crater.
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 BC. Historical lava flows cover much of the surface of this massive basaltic stratovolcano, the highest and most voluminous in Italy. 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. Flank eruptions, typically with higher effusion rates, occur less frequently and originate from fissures that open progressively downward from near the summit. A period of more intense intermittent explosive eruptions from Etna's summit craters began in 1995. The active volcano is monitored by the Instituto Nazionale di Geofisica e Volcanologia (INGV) in Catania.
Source: Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania (INGV-CT) http://www.ct.ingv.it/
EYJAFJOLL Southern Iceland 63.63°N, 19.62°W; summit elev. 1666 m
The Institute of Earth Sciences reported that on 7 April the eruption from Eyjafjöll ceased from the original eruption craters and was limited to the fissure that had opened on 31 March. Lava flows covered an estimated area of 1.3 square kilometers and were on average 10-20 m thick. The largest scoria cone was 82 m high. After minor changes in deformation rates during the eruption, on 9 April deformation returned to pre-eruption levels. Eruptive activity was observed on 11 April, but tremor decreased to baseline the next day. Also on 12 April, according to a new article, the Icelandic Civil Protection Department decided to lower the preparedness level by one point, from emergency to danger because of the decreasing activity. Another article stated that a pilot saw no active lava flows, only steam plumes, during an overflight on 13 April.
At 2300 on 13 April, a seismic swarm was detected below the central part of Eyjafjöll, W of the previous eruption fissures. About an hour later, the onset of seismic tremor heralded an eruption from a new vent on the S rim of the central caldera, capped by Eyjafjallajökull glacier. The eruption was visually confirmed early in the morning on 14 April; an eruption plume rose at least 8 km above the glacier. Meltwater flowed to the N and S. News outlets reported that a circular ice-free area about 200 m in diameter was seen near the summit. Scientists conducting an overflight saw a new 2-km-long, N-S-trending fissure, and ashfall to the E. About 700 people were ordered to evacuate the area, and certain flights were banned from flying N and E of the eruption area. Flooding increased throughout the day, causing road closures and some structural damage.
Geologic Summary. Eyjafjöll (also known as Eyjafjallajökull) is located immediately west of Katla volcano. Eyjafjöll consists of an E-W-trending, elongated ice-covered basaltic-andesite stratovolcano with a 2.5-km-wide summit caldera. Fissure-fed lava flows occur on both the eastern and western flanks of the volcano, but are more prominent on the western side. Although the 1666-m-high volcano has erupted during historical time, it has been less active than other volcanoes of Iceland's eastern volcanic zone, and relatively few Holocene lava flows are known. The sole historical eruption of Eyjafjöll, prior to an eruption in 2010, produced intermediate-to-silicic tephra from the central caldera during December 1821 to January 1823.
Sources: Institute of Earth Sciences http://www.earthice.hi.is/page/ies_forsida,
Icelandic Met Office http://en.vedur.is/,
Iceland Review http://icelandreview.com/icelandreview/
GAUA Banks Islands (SW Pacific) 14.27°S, 167.50°E; summit elev. 797 m
On 7 April, the Vanuatu Geohazards Observatory reported that recent field observations of Gaua confirmed significant changes in activity. Gas plumes were detected daily by satellite images. During the end of March through the beginning of April, ash plumes rose daily to altitudes of 2.1-3 km (7,000-10,000 ft) a.s.l. Explosions were heard in nearby villages. Starting on 3 April villagers living in the N and S parts of the island reported ashfall and saw bombs ejected from Gaua. Based on Vanuatu Geohazards Observatory information, the Wellington VAAC reported that during 8-12 April ash plumes rose to an altitude of 3 km (10,000 ft) a.s.l. Ash plumes were seen on satellite imagery on 11 and 12 April drifting S and SE. The Vanuatu Volcano Alert Level (VVAL) remained at 2 (on a scale of 0-4).
Geologic Summary. The roughly 20-km-diameter Gaua Island, also known as Santa Maria, consists of a basaltic-to-andesitic stratovolcano with an 6 x 9 km wide summit caldera. Small parasitic vents near the caldera rim fed Pleistocene lava flows that reached the coast on several sides of the island; several littoral cones were formed where these lava flows reached the sea. Quiet collapse that formed the roughly 700-m-deep caldera was followed by extensive ash eruptions. Construction of the historically active cone of Mount Garat (Gharat) and other small cinder cones in the SW part of the caldera has left a crescent-shaped caldera lake. The symmetrical, flat-topped Mount Garat cone is topped by three pit craters. The onset of eruptive activity from a vent high on the SE flank of Mount Garat in 1962 ended a long period of dormancy.
Sources: Vanuatu Geohazards Observatory http://www.geohazards.gov.vu/,
Wellington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/NZ/messages.html
MIYAKE-JIMA Izu Islands (Japan) 34.079°N, 139.529°E; summit elev. 815 m
Based on information from JMA, the Tokyo VAAC reported an eruption from Miyake-jima on 11 April. Details of possible resulting plumes were unknown.
Geologic Summary. The circular, 8-km-wide island of Miyake-jima forms a low-angle stratovolcano that rises about 1100 m from the sea floor in the northern Izu Islands about 200 km SSW of Tokyo. Parasitic craters and vents, including maars near the coast and radially oriented fissure vents, dot the flanks of the volcano. Frequent historical eruptions have occurred since 1085 AD at vents ranging from the summit to below sea level, causing much damage on this small populated island. After a three-century-long hiatus ending in 1469, activity has been dominated by flank fissure eruptions sometimes accompanied by minor summit eruptions. A 1.6-km-wide summit caldera was slowly formed by subsidence during an eruption in 2000; by October of that year the crater floor had dropped to only 230 m above sea level.
Source: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
REDOUBT Southwestern Alaska 60.485°N, 152.742°W; summit elev. 3108 m
AVO reported that the rate of small earthquakes in the vicinity of Redoubt's summit approached background levels during 7-11 April. Gas measurements on 8 April were consistent with a passively degassing and cooling lava dome. The Volcano Alert Level was lowered to Normal and the Aviation Color Code was lowered to Green on 12 April.
Geologic Summary. Redoubt is a 3108-m-high glacier-covered stratovolcano with a breached summit crater in Lake Clark National Park about 170 km SW of Anchorage. Next to Mount Spurr, Redoubt has been the most active Holocene volcano in the upper Cook Inlet. Collapse of the summit of Redoubt 10,500-13,000 years ago produced a major debris avalanche that reached Cook Inlet. Holocene activity has included the emplacement of a large debris avalanche and clay-rich lahars that dammed Lake Crescent on the south side and reached Cook Inlet about 3500 years ago. Eruptions during the past few centuries have affected only the Drift River drainage on the north. Historical eruptions have originated from a vent at the north end of the 1.8-km-wide breached summit crater. The 1989-90 eruption of Redoubt had severe economic impact on the Cook Inlet region and affected air traffic far beyond the volcano.
Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/
REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m
The IG reported that during 7-13 April observations of Reventador were not possible because of weather. The Washington VAAC reported that on 8 April an ash plume seen by pilots rose to altitudes of 4.6-6.7 km (15,000-22,000 ft) a.s.l. and drifted W. Cloud cover prevented satellite observations of the area. The VAAC also noted that seismicity was elevated.
Geologic Summary. Reventador is the most frequently active of a chain of Ecuadorian volcanoes in the Cordillera Real, well E of the principal volcanic axis. It is a forested stratovolcano that rises above the remote jungles of the western Amazon basin. A 3-km-wide caldera breached to the E was formed by edifice collapse and is partially filled by a young, unvegetated stratovolcano that rises about 1,300 m above the caldera floor. 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.
Sources: Instituto Geofísico-Escuela Politécnica Nacional (IG) http://www.igepn.edu.ec/,
Washington Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/messages.html
Ongoing Activity
ARENAL Costa Rica 10.463°N, 84.703°W; summit elev. 1670 m
OVSICORI-UNA reported that during March activity originating from Arenal's Crater C consisted of gas emissions, sporadic Strombolian eruptions, and occasional avalanches. A lava flow that began in mid-January remained active on the S flank. Acid rain and small amounts of ejected pyroclastic material affected the NE, E, and SE flanks. Avalanches from the crater and from lava-flow fronts traveled down the SW, S, and SE flanks, occasionally igniting vegetation. Crater D produced only fumarolic activity.
Geologic Summary. Conical Volcan Arenal is the youngest stratovolcano in Costa Rica and one of its most active. The 1,657-m-high andesitic volcano towers above the eastern shores of Lake Arenal, which has been enlarged by a hydroelectric project. The earliest known eruptions of Arenal took place about 7,000 years ago. Growth of Arenal has been characterized by periodic major explosive eruptions at several-hundred-year intervals and periods of lava effusion that armor the cone. Arenal's most recent eruptive period began with a major explosive eruption in 1968. Continuous explosive activity accompanied by slow lava effusion and the occasional emission of pyroclastic flows has occurred since then from vents at the summit and on the upper western flank.
Source: Observatorio Vulcanologico y Sismologico de Costa Rica-Universidad Nacional (OVSICORI-UNA) http://www.ovsicori.una.ac.cr/
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 6-11 April ash plumes from Batu Tara rose to an altitude of 2.1 km (7,000 ft) a.s.l. and drifted 25-75 km NW, NE, E, and SE.
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 historical eruption from Batu Tara, during 1847-52, produced explosions and a lava flow.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
DUKONO Halmahera 1.68°N, 127.88°E; summit elev. 1335 m
The Darwin VAAC reported that on 9 April an ash plume from Dukono was seen on satellite imagery drifting over 220 km NE at an altitude of 3.7 km (12,000 ft) a.s.l. During 10-12 April ash plumes rose to altitudes of 1.5-2.1 km (5,000-7,000 ft) a.s.l. and drifted 20-75 km NE.
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.
Source: Darwin Volcanic Ash Advisory Centre (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html
KARYMSKY Eastern Kamchatka 54.05°N, 159.45°E; summit elev. 1536 m
KVERT reported that seismic activity from Karymsky was above background on 2 and 3 April and at background levels during 4-9 April. Satellite imagery revealed a thermal anomaly from the volcano during 3-4 and 6 April. The Aviation Color Code level 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 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.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m
During 7-13 April, HVO reported incandescence from a 60-m-wide active lava surface about 200 m below a 130-m-wide vent in the floor of Kilauea's Halema'uma'u crater. The lava surface circulated and both rose and drained through a pit in the cavity floor; a few times the level fluctuated between 235 and 260 m below the surface. Rocks from the vent walls fell into the pond, causing spattering. Plumes from the vent drifted mainly SW, dropping small amounts of ash, and occasionally Pele's hair and Pele's tears, downwind. Measurements indicated that the sulfur dioxide emission rate at the summit remained elevated; 600 and 500 tonnes per day were measured on 8 and 9 April, respectively.
Lava from beneath the Thanksgiving Eve Breakout (TEB) and rootless shield complex flowed SE through the upper portion of a lava tube system and broke out onto the surface. Lava flows moved SE down Pulama pali.
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.
Source: US Geological Survey Hawaiian Volcano Observatory (HVO) http://hvo.wr.usgs.gov/
KLIUCHEVSKOI Central Kamchatka (Russia) 56.057°N, 160.638°E; summit elev. 4835 m
KVERT reported that during 2-9 April seismic activity from Kliuchevskoi was above background levels. Strombolian activity periodically ejected material 200 m above the crater and lava continued to flow down the flanks. Satellite imagery revealed a large daily thermal anomaly from the volcano, and gas-and-steam plumes that drifted 30-180 km NNE. On 7 April, gas-and-steam plumes containing small amounts of ash rose to an altitude of 6.3 km (20,700 ft) a.s.l. The next day, a diffuse ash plume drifted 55-60 km NE. The Aviation Color Code level remained at Orange.
Geologic Summary. Kliuchevskoi is Kamchatka's highest and most active volcano. Since its origin about 7,000 years ago, the beautifully symmetrical, 4,835-m-high basaltic stratovolcano has produced frequent moderate-volume explosive and effusive eruptions without major periods of inactivity. More than 100 flank eruptions, mostly on the NE and SE flanks of the conical volcano between 500 m and 3,600 m elevation, have occurred during the past 3,000 years. The morphology of its 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 major explosive and effusive events from flank craters.
Source: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php
POPOCATEPETL México 19.023°N, 98.622°W; summit elev. 5426 m
CENAPRED reported that most days during 7-13 April emissions of steam and gas from Popocatépetl contained minor amounts of ash.
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.
Source: Centro Nacional de Prevencion de Desastres (CENAPRED) http://www.cenapred.unam.mx/es/
RABAUL New Britain 4.271°S, 152.203°E; summit elev. 688 m
RVO reported on 9 April that deformation measurements at Rabaul caldera during the previous 3-4 months showed an inflationary trend with a total of 4 cm of uplift. During 2-8 April seismicity was low and variable amounts of white vapor rose from Tavurvur cone.
Geologic Summary. The low-lying Rabaul caldera on the tip of the Gazelle Peninsula at the NE end of New Britain forms a broad sheltered harbor. The outer flanks of the 688-m-high asymmetrical pyroclastic shield volcano are formed by thick pyroclastic-flow deposits. The 8 x 14 km caldera is widely breached on the E, where its floor is flooded by Blanche Bay. Two major Holocene caldera-forming eruptions at Rabaul took place as recently as 3,500 and 1,400 years ago. Three small stratovolcanoes lie outside the northern and NE caldera rims. Post-caldera eruptions built basaltic-to-dacitic pyroclastic cones on the caldera floor near the NE and western caldera walls. Several of these, including Vulcan cone, which was formed during a large eruption in 1878, have produced major explosive activity during historical time. A powerful explosive eruption in 1994 occurred simultaneously from Vulcan and Tavurvur volcanoes and forced the temporary abandonment of Rabaul city.
Source: Rabaul Volcano Observatory (RVO)
SAKURA-JIMA Kyushu 31.585°N, 130.657°E; summit elev. 1117 m
The Tokyo VAAC reported that during 7-13 April explosions from Sakura-jima sometimes produced plumes identified in satellite imagery. Those plumes, along with ash plumes occasionally seen by pilots, rose to altitudes of 1.5-3 km (5,000-10,000 ft) a.s.l. and sometimes drifted NW, E, and SE.
Geologic Summary. Sakura-jima, one of Japan's most active volcanoes, is a post-caldera cone of the Aira caldera at 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 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: Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
SHIVELUCH Central Kamchatka (Russia) 56.653°N, 161.360°E; summit elev. 3283 m
KVERT reported that during 2-9 April seismic activity from Shiveluch was above background levels. Ash plumes from hot avalanches rose to an altitude of 6.1 km (20,000 ft) a.s.l. on 5 and 8 April. Satellite imagery revealed a large daily thermal anomaly from the lava dome, and ash plumes that drifted about 100 km SE on 5 April. The Tokyo VAAC reported that on 10 April ash plumes were seen in satellite imagery. The Aviation Color Code level 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 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.
Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) http://www.kscnet.ru/ivs/kvert/index_eng.php,
Tokyo Volcanic Ash Advisory Center (VAAC) http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html
SOUFRIERE HILLS Montserrat 16.72°N, 62.18°W; summit elev. 915 m
MVO reported that during 2-9 April activity from the Soufrière Hills lava dome was at a low level. Rockfalls occurred sporadically from several areas of the lava dome. Multiple small areas of incandescence on the dome were visible several nights during the reporting period. Heavy rains on 2 April caused lahars in the Farm River and Trants area (NNE). The Hazard Level remained at 3.
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 and pyroclastic 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.
Source: Montserrat Volcano Observatory (MVO) http://www.mvo.ms/
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