VOLCANO: SI/USGS Weekly Volcanic Activity Report 29 September-5 October 2010

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SI/USGS Weekly Volcanic Activity Report 29 September-5 October 2010
From: "Kuhn, Sally" <KUHNS@xxxxxx>
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SI/USGS Weekly Volcanic Activity Report

29 September-5 October 2010



Sally Kuhn Sennert - Weekly Report Editor

kuhns@xxxxxx

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





New Activity/Unrest: | Nevado del Huila, Colombia | Nevado del Ruiz,
Colombia | Piton de la Fournaise, Reunion Island | Planchón-Peteroa,
Central Chile-Argentina border | Reventador, Ecuador



Ongoing Activity: | Bagana, Bougainville | Batu Tara, Komba Island
(Indonesia) | Dukono, Halmahera | Fuego, Guatemala | Karymsky, Eastern
Kamchatka (Russia) | Kilauea, Hawaii (USA) | Kliuchevskoi, Central
Kamchatka (Russia) | Pacaya, Guatemala | Popocatépetl, México |
Sakura-jima, Kyushu | Sarychev Peak, Matua Island | Shiveluch, Central
Kamchatka (Russia) | Soufrière Hills, Montserrat | Suwanose-jima,
Ryukyu Islands (Japan)



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





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



The Popayán Volcano Observatory (INGEOMINAS) reported that during 29
September-5 October gas plumes from Nevado del Huila, observed with
the Tafxnú and Maravillas web cameras, rose 2.5 km above the summit.
Incandescence from the extruding lava dome and collapsing material was
also noted. Based on a SIGMET issued from the Bogota MWO, the
Washington VAAC reported that on 1 October an ash plume rose to an
altitude of 7.6 km (25,000 ft) a.s.l. Later that day, a 10-km-wide
gas-and-ash plume was seen in satellite imagery drifting about 30 km
S. The Alert Level remained at II (Orange; "probable eruption in term
of days or weeks").



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.



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

Washington Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/messages.html





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



INGEOMINAS reported a gradual increase in seismicity from Nevado del
Ruiz on 30 September. Earthquakes were located beneath the Arenas
crater at depths of 0.5-2 km. The largest earthquake was M 1.9. A
plume of white gas rose 700 m above the caldera and a sulfur odor
around the volcano was reported. The Alert Level was raised to III
(Yellow; "changes in the behavior of volcanic activity") on 1 October.
The report also noted changes in deformation and geochemistry during
the previous few months. Seismic levels fluctuated during 2-3 October.



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.



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





PITON DE LA FOURNAISE Reunion Island 21.231°S, 55.713°E; summit elev. 2632 m



OVPDLF reported that on 29 September seismicity from Piton de la
Fournaise remained high. Earthquakes were located at the base of the
volcano, and inflation was noted particularly in the E. A significant
number of landslides were detected in the crater. The Alert level
remained at 1 ("probable or imminent eruption").



Geologic Summary. Massive Piton de la Fournaise shield volcano on the
island of Réunion is one of the world's most active volcanoes. Most
historical eruptions have originated from the summit and flanks of a
400-m-high lava shield, Dolomieu, that has grown within the youngest
of three large calderas. This depression is 8 km wide and is breached
to below sea level on the eastern side. More than 150 eruptions, most
of which have produced fluid basaltic lava flows within the caldera,
have been documented since the 17th century. The volcano is monitored
by the Piton de la Fournaise Volcano Observatory, one of several
operated by the Institut de Physique du Globe de Paris.



Source: Observatoire Volcanologique du Piton de la Fournaise (OVPDLF)
http://www.ipgp.fr/pages/03030810.php





PLANCHON-PETEROA Central Chile-Argentina border 35.240°S, 70.570°W;
summit elev. 4107 m



Based on analyses of satellite imagery, pilot observations, and SIGMET
notices, the Buenos Aires VAAC reported that during 30 September-3
October ash plumes from Planchón-Peteroa rose to altitudes of 3-6.1 km
(10,000-20,000 ft) a.s.l. and drifted NW, NNE, E, and SE.



Geologic Summary. Planchón-Peteroa is an elongated complex volcano
along the Chile-Argentina border with several overlapping calderas.
Activity began in the Pleistocene with construction of the
basaltic-andesite to dacitic Volcán Azufre, followed by formation of
basaltic and basaltic-andesite Volcán Planchón, 6 km to the N. About
11,500 years ago, much of Azufre and part of Planchón collapsed,
forming the massive Río Teno debris avalanche, which reached Chile's
Central Valley. Subsequently, Volcán Planchón II was formed. The
youngest volcano, andesitic and basaltic-andesite Volcá Peteroa,
consists of scattered vents between Azufre and Planchón. Peteroa has
been active into historical time and contains a small steaming crater
lake. Historical eruptions from the Planchón-Peteroa complex have been
dominantly explosive, although lava flows were erupted in 1837 and
1937.



Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html





REVENTADOR Ecuador 0.077°S, 77.656°W; summit elev. 3562 m



According to the Washington VAAC, the IG reported ash over Reventador
on 30 September. The VAAC stated that a diffuse plume was observed in
satellite imagery drifting NW, although ash was not identified.



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.



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





Ongoing Activity





BAGANA Bougainville 6.140°S, 155.195°E; summit elev. 1750 m



Based on analyses of satellite imagery, the Darwin VAAC reported that
on 1 October an ash plume from Bagana rose to an altitude of 2.4 km
(8,000 ft) a.s.l. and drifted 75 km NW.



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 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
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)
http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html





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 29 September-5 October ash plumes from Batu Tara rose to an
altitude of 1.5 km (5,000 ft) a.s.l. and drifted 35-95 km W and 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 1-4 October ash plumes from Dukono rose to an altitude of 2.4
km (8,000 ft) a.s.l. and drifted 55-205 km W and NW.



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





FUEGO Guatemala 14.473°N, 90.880°W; summit elev. 3763 m



INSIVUMEH reported that on 2 October a seismic station near Fuego
recorded some explosions and a possible lahar that traveled SE.
Weather prevented visual observations. During 4-5 October, explosions
ejected incandescent material above the crater and produced ash plumes
that rose 500-700 m above the crater.



Geologic Summary. Volcán Fuego, one of Central America's most active
volcanoes, is one of three large stratovolcanoes overlooking
Guatemala's former capital, Antigua. The scarp of an older edifice,
Meseta, lies between 3,763-m-high Fuego and its twin volcano to the N,
Acatenango. Construction of Meseta volcano continued until the late
Pleistocene or early Holocene, after which growth of the modern Fuego
volcano continued the southward migration of volcanism that began at
Acatenango. Frequent vigorous historical eruptions have been recorded
at Fuego since the onset of the Spanish era in 1524, and have produced
major ashfalls, along with occasional pyroclastic flows and lava
flows. The last major explosive eruption from Fuego took place in
1974, producing spectacular pyroclastic flows visible from Antigua.



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





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



KVERT reported that seismic activity from Karymsky was at background
levels during 22-24 September and above background levels during 25-29
September. The elevated seismicity suggested that ash explosions had
occurred. Ash plumes rose to altitudes of 3-4.5 km (9,800-14,800 ft)
a.s.l. during 25-27 September. Thermal anomalies were seen in
satellite imagery on 23, 25, and 28 September, and ash plumes drifted
83 km SE on 28 September. 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 29 September-5 October, HVO reported that activity at Kilauea
continued from the summit caldera and the east rift zone. At the
summit caldera, the level of the lava-pool surface in the deep pit
within Halema'uma'u crater remained mostly stable at about 150 m below
the crater floor; periodically the lava rose 15-35 m above that level.
Glow from the vent was also visible at night. A plume from the vent
drifted mainly SW and deposited ash nearby.



At the east rift zone, lava that flowed through the TEB lava-tube
system mainly fed the Puhi-o-Kalaikini ocean entry. A lava flow that
broke out of the lava-tube system W of the end of Highway 130 on 26
September produced a flow E toward Kalapana Gardens that stalled on 28
September. Two days later a new breakout lava flow began near the end
of Highway 130, just west of Kalapana Gardens subdivision. The flow
sparked fires in a small, sparsely forested kipuka, and remained
active through 4 October.



During 29 September-4 October, incandescence was visible from a
skylight on the lava tube downslope from the rootless shield complex.
A large skylight on top of a rootless shield, built over the TEB lava
tube mid-way between the top of the pali and the TEB vent, also showed
incandescence. On 29 September, lava began to erupt from a vent on the
NW edge of Pu'u 'O'o crater and flowed E across the floor. The lava
flow in Pu'u 'O'o crater continued to be active through the reporting
period.



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 24 September-1 October seismic activity
from Kliuchevskoi was above background levels and lava from the summit
crater flowed down the SW flank. Satellite imagery analyses showed a
large and intense daily thermal anomaly over the volcano. Ash plumes
were seen rising to altitudes of 6.5-7 km (21,300-23,000 ft) a.s.l. on
22 and 24 September, and Strombolian activity was observed during 23,
25, and 28-29 September. Ash plumes seen in satellite imagery drifted
185 km E on 22 and 28 September and 78 km W on 24 and 25 September.
KVERT noted that eruptive activity from Kliuchevskoi had been
continuous since 1 September 2009. 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





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



INSIVUMEH reported that during 2 and 4-5 October steam-and-gas plumes
rose from Pacaya's MacKenney cone and drifted S.



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/





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



CENAPRED reported that during 30 September-4 October steam-and-gas
emissions from Popocatépetl occasionally contained small 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/





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



Based on a pilot observation, the Tokyo VAAC reported that on 1
October an ash plume from Sakura-jima rose to an altitude of 1.8 km
(6,000 ft) a.s.l.



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





SARYCHEV PEAK Matua Island 48.092°N, 153.20°E; summit elev. 1496 m



SVERT reported that a diffuse ash plume from Sarychev Peak was
detected by satellite on 20 September. Sarychev Peak does not have a
seismic network; satellite image observations are the primary tool for
monitoring many of the Kurile Islands volcanoes.



Geologic Summary. Sarychev Peak, one of the most active volcanoes of
the Kuril Islands, occupies the NW end of Matua Island in the central
Kuriles. The andesitic central cone was constructed within a 3-3.5 km
wide caldera, whose rim is exposed only on the SW side. A dramatic
250-m-wide, very steep-walled crater with a jagged rim caps the
volcano. The substantially higher SE rim forms the 1496 m high point
of the island. Fresh-looking lava flows descend all sides of Sarychev
Peak and often form capes along the coast. Much of the lower-angle
outer flanks of the volcano are overlain by pyroclastic-flow deposits.
Eruptions have been recorded since the 1760's and include both quiet
lava effusion and violent explosions. The largest historical eruption
of Sarychev Peak in 1946 produced pyroclastic flows that reached the
sea.



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





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



KVERT reported that during 24 September-1 October seismic activity
from Shiveluch was above background levels and suggested that possible
ash plumes rose from the volcano. Gas-and-steam plumes were observed
during 23, 25, and 28-29 September. Satellite imagery analyses showed
a daily thermal anomaly on the volcano and gas-and-steam plumes that
drifted 70 km SE on 29 September. Based on analyses of satellite
imagery, the Tokyo VAAC reported a possible eruption on 3 October; a
subsequent notice stated that ash had dissipated. 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 24 September-1 October activity from the
Soufrière Hills lava dome was at a low level. Several pyroclastic
flows originating from the W side of the lava dome moved W down Gages
Valley and into Spring Ghaut. The largest pyroclastic flow traveled
approximately 2 km. 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/





SUWANOSE-JIMA Ryukyu Islands (Japan) 29.635°N, 129.716°E; summit elev. 799 m



Based on information from JMA, the Tokyo VAAC reported explosions from
Suwanose-jima during 3-5 October. A plume drifted E on 5 October.



Geologic Summary. The 8-km-long, spindle-shaped island of
Suwanose-jima in the northern Ryukyu Islands consists of an andesitic
stratovolcano with two historically active summit craters. Only about
50 persons live on the sparsely populated island. The summit of the
volcano is truncated by a large breached crater extending to the sea
on the east flank that was formed by edifice collapse. Suwanose-jima,
one of Japan's most frequently active volcanoes, was in a state of
intermittent Strombolian activity from On-take, the NE summit crater,
that began in 1949 and lasted nearly a half century. The largest
historical eruption took place in 1813-14, when thick scoria deposits
blanketed residential areas, after which the island was uninhabited
for about 70 years. The SW crater produced lava flows that reached the
western coast in 1813, and lava flows reached the eastern coast of the
island in 1884.



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

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