Wednesday, June 23, 2010

[ Volcano ] SI/USGS Weekly Volcanic Activity Report 16-22 June 2010

SI/USGS Weekly Volcanic Activity Report

16-22 June 2010

Sally Kuhn Sennert - Weekly Report Editor

kuhns@si.edu

URL: http://www.volcano.si.edu/reports/usgs/

New Activity/Unrest: | Etna, Sicily (Italy) | Gorely, Southern Kamchatka
(Russia) | Ioto [Iwo-jima], Volcano Islands (Japan) | Nevado del Huila,
Colombia | Pacaya, Guatemala | Tiatia, Kunashir Island | Tungurahua, Ecuador
| Ulawun, New Britain

Ongoing Activity: | Batu Tara, Komba Island (Indonesia) | Dukono, Halmahera
| Gaua, Banks Islands (SW Pacific) | Karymsky, Eastern Kamchatka (Russia) |
Kilauea, Hawaii (USA) | Kliuchevskoi, Central Kamchatka (Russia) |
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

ETNA Sicily (Italy) 37.734°N, 15.004°E; summit elev. 3330 m

INGV-CT reported a series of landslides on 19 June from the NW rim of the
pit crater located on the lower E side of Etna's Southeast Crater. The
collapses generated small ash clouds that drifted NE, and changed the pit
crater's morphology. Data from a thermal camera showed thermal anomalies
over 180 degrees Celsius indicating that the landslide material was hot.
Fumarolic activity was seen in the landslide area during an inspection the
day before.

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/

GORELY Southern Kamchatka (Russia) 52.558°N, 158.03°E; summit elev. 1829 m

KVERT reported that during 6 and 12-13 June strong steam-and-gas activity
from Gorely was noted, and during 11-18 June seismic activity was above
background levels. A small increase in the size and temperature of a thermal
anomaly over the volcano began on 15 June and was detected through 18 June.
The Level of Concern Color Code remained at Green.

Geologic Summary. Gorely volcano, one of the most active in southern
Kamchatka, consists of five small overlapping stratovolcanoes constructed
along a WNW-ESE line within a large 9 x 13.5 km late-Pleistocene caldera.
The massive Gorely complex contains 11 summit and 30 flank craters. During
the early Holocene, activity was characterized by frequent mild eruptions
with occasional larger explosions and lava flows that filled in the caldera.
Quiescent periods became longer between 6,000 and 2,000 years ago, after
which the activity was mainly explosive. About 600-650 years ago
intermittent strong explosions and lava flow effusion accompanied frequent
mild eruptions. Historical eruptions have consisted of vulcanian and
phreatic explosions of moderate volume.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
http://www.kscnet.ru/ivs/kvert/index_eng.php

IOTO [IWO-JIMA] Volcano Islands (Japan) 24.754°N, 141.290°E; summit elev.
161 m

Based on a pilot observation, the Tokyo VAAC reported that an ash plume from
Ioto (Iwo-jima) drifted more than 35 km N.

Geologic Summary. Ioto (also known as Iwo-jima) in the central Volcano
Islands portion of the Izu-Marianas arc lies within a 9-km-wide submarine
caldera. Ioto, Iwo-jima, and Io-jima are among many transliterations of the
name, which means "Sulfur Island;" the volcano is also known as Ogasawara
Io-jima to distinguish it from several other "Sulfur Island" volcanoes in
Japan. The triangular, low-elevation, 8-km-long island narrows toward its SW
tip and has produced trachyandesitic and trachytic rocks that are more
alkalic than those of other Izu-Marianas arc volcanoes. The island has
undergone dramatic uplift for at least the past 700 years accompanying
resurgent doming of the caldera. A shoreline landed upon by Captain Cook's
surveying crew in 1779 is now 40 m above sea level. The Moto-yama plateau on
the NE half of the island consists of submarine tuffs overlain by coral
deposits and forms the island's high point. Many fumaroles are oriented
along a NE-SW zone cutting through Moto-yama. Numerous historical phreatic
eruptions, many from vents on the west and NW sides of the island, have
accompanied the remarkable uplift.

Source: Tokyo Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html

NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5364 m

INGEOMINAS reported that during 9-15 June sulfur dioxide plumes from Nevado
del Huila were detected by multiple sources. A distinct change in seismicity
was noted on 13 June and was characterized by an increased intensity and a
greater number of hybrid earthquakes. These earthquakes were shallow events
beneath Pico Central. The Alert Level was raised to II (Orange; "probable
eruption in term of days or weeks"). On 16 June two episodes of tremor
possibly indicated ash emissions; this was unconfirmed. However, sulfur
dioxide plumes were again detected. During 20-21 June small white pulsating
fumarolic plumes drifted W.

Geologic Summary. Nevado del Huila, the highest active volcano in Colombia,
is an elongated N-S-trending volcanic chain mantled by a glacier icecap. The
andesitic-dacitic volcano was constructed within a 10-km-wide caldera.
Volcanism at Nevado del Huila has produced six volcanic cones whose ages in
general migrated from south to north. Two glacier-free lava domes lie at the
southern end of the Huila volcanic complex. The first historical eruption
from this little known volcano took place in the 16th century. Two
persistent steam columns rise from the central peak, and hot springs are
also present.

Source: Instituto Colombiano de Geología y Minería (INGEOMINAS)
http://www.ingeominas.gov.co//

PACAYA Guatemala 14.381°N, 90.601°W; summit elev. 2552 m

INSIVUMEH reported that during 16-22 June Pacaya's MacKenney cone emitted
white-and-blue fumarolic plumes that rose 50-400 m high. Ash emissions were
occasionally observed. INSIVUMEH also noted that the lava flows on the SE
flank were advancing more slowly and exhibited fewer areas of incandescence.

Geologic Summary. Eruptions from Pacaya, one of Guatemala's most active
volcanoes, are frequently visible from Guatemala City, the nation's capital.
Pacaya is a complex volcano constructed on the southern rim of the 14 x 16
km Pleistocene Amatitlan caldera. A cluster of dacitic lava domes occupies
the caldera floor. The Pacaya massif includes the Cerro Grande lava dome and
a younger volcano to the SW. Collapse of Pacaya volcano about 1,100 years
ago produced a debris-avalanche deposit that extends 25 km onto the Pacific
coastal plain and left an arcuate somma rim inside which the modern Pacaya
volcano (MacKenney cone) grew. During the past several decades, activity at
Pacaya has consisted of frequent Strombolian eruptions with intermittent
lava flow extrusion on the flanks of MacKenney cone, punctuated by
occasional larger explosive eruptions.

Source: Instituto Nacional de Sismologia, Vulcanologia, Meteorologia, e
Hidrologia (INSIVUMEH) http://www.insivumeh.gob.gt/

TIATIA Kunashir Island 44.351°N, 146.256°E; summit elev. 1819 m

SVERT reported that a thermal anomaly from Tiatia, a volcano on NE Kunashir
Island, was detected by satellite on 19 June. Tiatia does not have a seismic
network; satellite image observations are the primary tool for monitoring
many of the Kuril Islands volcanoes.

Geologic Summary. Tiatia volcano, one of the most impressive of the Kuril
Islands, consists of a beautifully symmetrical cone that rises above the
broad rim of an erosionally furrowed, 2.1 x 2.4 km wide caldera. The
1819-m-high Tiatia (also known as Chacha-dake) occupies the NE tip of
Kunashir Island and morphologically resembles Mount Vesuvius. The
pristine-looking conical central cone, mostly formed by basaltic to
basaltic-andesite strombolian eruptions, rises 400 m above the floor of the
caldera and contains a 400 x 250 m wide crater with two explosion vents
separated by a linear septum. Fresh lava flows cover much of the SW caldera
floor and have overflowed the rim, extending to the foot of the older somma,
which formed during the late Pleistocene or early Holocene. A lava flow from
a flank cone on the northern caldera rim reached the Sea of Okhotsk. A major
explosive eruption in 1973 was the first since Tiatia's initial historical
eruption in 1812.

Source: Sakhalin Volcanic Eruption Response Team (SVERT)
http://www.imgg.ru/rus/labs_vulcan_hazard.php

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

Although storm clouds occasionally prevented observations of Tungurahua's
summit area during 16-18 June, steam-and-ash plumes were seen that rose to
altitudes of 5.5-7 km (18,000-23,000 ft) a.s.l. Daily reports of ashfall
came from multiple areas about 8 km W and SW, but ash was noted as far away
as 15 km SW on 17 June. Ashfall in Cahuají (8 km SW) covered pastureland,
preventing animals from grazing. Roaring noises were occasionally reported.
During 17-18 June, incandescence from the crater was seen at night. An
explosion was followed by roaring noises, sounds resembling blocks rolling
down the flanks, and incandescence.

On 19 June steam-and-ash plumes rose 500 m above the crater and large
windows vibrated after noises were heard. The next day snow covered parts of
the E and S flanks. Steam-and-gas plumes rose 500 m and drifted SSW, E, and
NW during 20-21 June. Lahars in drainages to the SW carried blocks up to 50
cm in diameter. On 21 June ashfall was reported in areas 8 km W.

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 by pyroclastic 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: Instituto Geofísico-Escuela Politécnica Nacional (IG)
http://www.igepn.edu.ec/

ULAWUN New Britain 5.05°S, 151.33°E; summit elev. 2334 m

RVO reported that during 16-17 June white and gray plumes from Ulawun rose 1
km high. Fine ash fell on the SW, W, and NW flanks. Low rumbling noises were
heard from the S and SE flanks, and weak fluctuating incandescence was
observed for a brief period of time. On 18 and 19 June, white-to-gray plumes
rose from the crater, and roaring noises were reported from the NW flank.
Seismicity increased to a high level and was dominated by volcanic tremor.
During 19-20 June continuing white and gray emissions produced plumes that
rose 1 km. Fine ashfall was seen on the NW and SW flanks. Fluctuating
incandescence was seen from the S and SE flanks and occasional low roaring
noises were noted. Seismicity declined to moderate levels on 20 June.

Geologic Summary. The symmetrical basaltic to andesitic Ulawun stratovolcano
is the highest volcano of the Bismarck arc, and one of Papua New Guinea's
most frequently active. Ulawun rises above the N coast of New Britain
opposite Bamus volcano. The upper 1,000 m of the 2,334-m-high volcano is
unvegetated. A steep-walled valley cuts the NW side of the volcano, and a
flank lava-flow complex lies to the S of this valley. Historical eruptions
date back to the beginning of the 18th century. Twentieth-century eruptions
were mildly explosive until 1967, but after 1970 several larger eruptions
produced lava flows and basaltic pyroclastic flows, greatly modifying the
summit crater.

Source: Rabaul Volcano Observatory (RVO)

Ongoing Activity

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
19-20 June ash plumes from Batu Tara rose to an altitude of 3 km (10,000 ft)
a.s.l. and drifted more than 35 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 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

Based on analyses of satellite imagery, the Darwin VAAC reported that during
18-20 June ash plumes from Dukono rose to an altitude of 2.4 km (8,000 ft)
a.s.l. and drifted 120 km W.

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

GAUA Banks Islands (SW Pacific) 14.27°S, 167.50°E; summit elev. 797 m

Based on information from the Vanuatu Geohazards Observatory, the Wellington
VAAC reported that during 16-19 June ash plumes from Gaua rose to an
altitude of 3 km (10,000 ft) a.s.l. On 19 June the plume drifted more than
90 km W.

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.

Source: Wellington Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/UK/messages.html

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

KVERT reported that during 11-18 June seismic activity from Karymsky was
above background levels. Seismic data suggested that possible ash plumes
rose to an altitude of 5.2 km (17,000 ft) a.s.l. during 10-12 June and to an
altitude of 3.9 km (12,800 ft) a.s.l. on 16 June. Satellite imagery analysis
revealed ash plumes that drifted about 195 km E on 10 and 11 June and a
thermal anomaly over the volcano on 11, 15, and 16 June. Small ash clouds
drifted 22 km E on 17 June. 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 16-22 June HVO reported that activity at Kilauea continued from the
summit and the east rift zone. At the summit, the level of a lava-pool
surface in the deep pit inset within the floor of Halema'uma'u crater
remained mostly stable; glow from the vent was also visible at night. A
plume from the vent mainly drifted SW, dropping small amounts of tephra, and
occasionally fresh spatter, downwind.

At the east rift zone, lava flows that broke out of the TEB lava-tube system
built up a number of rootless shields between 580 and 520 m elevation.
Satellite images showed thermal anomalies from minor lava flows originating
from the shields. The Pu'u 'O'o web camera views of a lava pond on the
crater floor, that was an estimated 300 x 150 m in dimension, were often
obscured by fumes. One small lava flow was seen on the crater floor on 18
June. Scientists saw a new gas vent on the E wall of the crater during an
overflight on 21 June that had generated incandescence during the previous
few days.

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 11-18 June seismic activity from Kliuchevskoi was
above background levels and Strombolian activity was observed. Ashfall was
reported in Klyuchi, 30 km NNE on 11 June. Ash plumes occasionally rose to
an altitude of 5.5 km (18,000 ft) a.s.l. during 13-16 June. Satellite
imagery analysis revealed a large daily thermal anomaly from the volcano and
ash plumes that drifted 40 km SE on 13 and 15 June. 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

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

Based on information from JMA, the Tokyo VAAC reported that during 16-22
June explosions from Sakura-jima sometimes produced plumes. Those plumes,
along with ash plumes occasionally seen by pilots, rose to altitudes of
1.2-3 km (4,000-10,000 ft) a.s.l. According to a news article, the JMA noted
that two eruptions on 20 June brought the total number of eruptions in 2010
to 550, setting a new annual record. The total number of eruptions in 2009,
the previous high at Sakura-jima, was 548.

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.

Sources: Tokyo Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html,

Japan Times http://search.japantimes.co.jp/rss/nn20100621a6.html

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

KVERT reported that during 11-18 June seismic activity from Shiveluch was
above background levels and suggested that possible ash plumes rose to an
altitude of 4.9 km (16,100 ft) a.s.l. Strong fumarolic activity and hot
avalanches were seen on most days. Satellite imagery showed a large daily
thermal anomaly over the lava dome, and a small anomaly near the lava dome
on 15 June. 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.

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)
http://www.kscnet.ru/ivs/kvert/index_eng.php

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

MVO reported that pyroclastic flows from the Soufrière Hills lava dome
occurred during 11-18 June. One of the largest pyroclastic flows traveled W
down Gages Valley; others originated from within the collapse scar. A
thermal camera showed several hot areas on the lava dome, likely exposed
from rockfall and pyroclastic flow activity. On 28 June a small lahar
descended the Belham Valley, to the NW. 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/

+++++++++++++++++++++++++++++++++++++

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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