SI/USGS Weekly Volcanic Activity Report 15-21 October 2008

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



**************************************************************
SI/USGS Weekly Volcanic Activity Report
15-21 October 2008
**************************************************************

Sally Kuhn Sennert - Weekly Report Editor
kuhns@xxxxxx
URL: http://www.volcano.si.edu/reports/usgs/


New Activity/Unrest: | Kliuchevskoi, Central Kamchatka (Russia) |
Soputan, Sulawesi (Indonesia)

Ongoing Activity: | Akan, Hokkaido (Japan) | Batu Tara, Komba Island
(Indonesia) | Chaitén, Southern Chile | Galeras, Colombia | Karymsky,
Eastern Kamchatka | Kilauea, Hawaii (USA) | Nyiragongo, Democratic
Republic of Congo | Piton de la Fournaise, Reunion Island |
Popocatépetl, México | Rabaul, New Britain (SW Pacific) | Shiveluch,
Central Kamchatka (Russia) | Soufrière Hills, Montserrat |
Suwanose-jima, Ryukyu Islands (Japan) | Tungurahua, Ecuador | Ubinas,
Perú


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


KLIUCHEVSKOI Central Kamchatka (Russia) 56.057°N, 160.638°E; summit elev. 4835 m

KVERT reported that seismic activity at Kliuchevskoi was above
background levels during 10-17 October. Fumarolic activity was noted
during 10-11 and 13-16 October. Observers in Klyuchi, about 30 km to
the NE, reported nighttime incandescence in the crater on 13 and 14
October. Analysis of satellite imagery revealed a thermal anomaly in
the crater during 10-11 and 13-15 October. The Level of Concern Color
Code remained 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


SOPUTAN Sulawesi (Indonesia) 1.108°N, 124.73°E; summit elev. 1784 m

CVGHM reported that the Alert Level for Soputan was lowered from 3 to
2 (on a scale of 1-4) on 21 October. CVGHM reported additional
information describing the eruption that prompted the Alert Level
increase on 6 October. Gray plumes rose to an altitude of 2.8 km
(9,200 ft) a.s.l. and were accompanied by Strombolian activity that
ejected incandescent material 50-150 m above the crater. On 7 October,
white plumes rose to altitudes of 2.3-3.3 km (7,500-10,800 ft) a.s.l.
Incandescent material was again ejected 50-150 m from the crater.
Incandescent rockfalls traveled 500 m W. The next day, plumes rose to
an altitude of 2 km (6,600 ft) a.s.l.

Geologic Summary. The small conical volcano of Soputan on the southern
rim of the Quaternary Tondano caldera is one of Sulawesi's most active
volcanoes. 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: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/


Ongoing Activity


AKAN Hokkaido (Japan) 43.384°N, 144.013°E; summit elev. 1499 m

On 17 October, JMA lowered the Alert level for Me-Akan (also called
Meakan-dake, which means Meakan Peak) of the Akan volcanic complex
from near-crater warning to normal. Seismic tremor was no longer
detected after 30 September, and seismicity had remained low after 3
October.

Geologic Summary. Akan is a 13 x 24 km, elongated caldera that formed
more than 31,500 years ago immediately SW of Kutcharo caldera. Growth
of four post-caldera stratovolcanoes, three at the SW end of the
caldera and the other at the NE side, has restricted the size of the
caldera lake. The 1-km-wide Nakamachineshiri crater was formed during
a major pumice-and-scoria eruption about 13,500 years ago. Of the
Holocene volcanoes of the Akan volcanic complex, only the Me-Akan
group, E of Lake Akan, has been historically active, producing mild
phreatic eruptions since the beginning of the 19th century. Me-Akan is
composed of 9 overlapping cones. The main cone of Me-Akan proper has a
triple crater at its summit. Historical eruptions at Me-Akan have
consisted of minor phreatic explosions, but four major magmatic
eruptions including pyroclastic flows have occurred during the
Holocene.

Source: Japan Meteorological Agency (JMA) http://www.jma.go.jp/jma/indexe.html


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

Based on analysis of satellite imagery, the Darwin VAAC reported that
during 16-20 October ash plumes from Batu Tara rose to altitudes of
1.5-2.4 km (5,000-8,000 ft) a.s.l. and drifted W.

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


CHAITEN Southern Chile 42.833°S, 72.646°W; summit elev. 1122 m

SERNAGEOMIN reported that during 14-20 October a gas-and-ash plume
from Chaitén rose to an altitude of 3.1 km (10,200 ft) a.s.l. The lava
dome continued to grow, especially the E side. The Volcanic Alert
level remained at Red. Based on web camera views, information from the
Puerto Montt Flight Information Region (FIR), analysis of satellite
imagery, and SIGMET reports, the Buenos Aires VAAC reported that
during 14-18 and 21 October continuous ash plumes from Chaitén rose to
altitudes of 2.1-4 km (7,000-13,000 ft) a.s.l. and drifted N, NE, and
ESE.

Geologic Summary. Chaitén is a small, glacier-free caldera with a
Holocene lava dome located 10 km NE of the town of Chaitén on the Gulf
of Corcovado. A pyroclastic-surge and pumice deposit considered to
originate from the eruption that formed the elliptical 2.5 x 4 km wide
summit caldera was dated at about 9400 years ago. A rhyolitic,
962-m-high obsidian lava dome occupies much of the caldera floor.
Obsidian cobbles from this dome found in the Blanco River are the
source of prehistorical artifacts from archaeological sites along the
Pacific coast as far as 400 km away from the volcano to the north and
south. The caldera is breached on the SW side by a river that drains
to the bay of Chaitén, and the high point on its southern rim reaches
1122 m.

Sources: Servicio Nacional de Geología y Minería (SERNAGEOMIN)
http://www.sernageomin.cl/index.php,
Buenos Aires Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/AG/messages.html


GALERAS Colombia 1.22°N, 77.37°W; summit elev. 4276 m

On 21 October, INGEOMINAS reported that during the previous week
pulsating white plumes occasionally tinged gray rose from Galeras to
altitudes of 4.6-7.4 km (15,100-24,300 ft) a.s.l. and drifted S. On 20
October, a M 2.3 earthquake located 600 m SSW of the main crater
occurred at a depth of less than 1 km.

Geologic Summary. Galeras, a stratovolcano with a large breached
caldera located immediately W of the city of Pasto, is one of
Colombia's most frequently active volcanoes. The dominantly andesitic
Galeras volcanic complex has been active for more than 1 million
years, and two major caldera collapse eruptions took place during the
late Pleistocene. Longterm extensive hydrothermal alteration has
affected the volcano. This has contributed to large-scale edifice
collapse that has occurred on at least three occasions, producing
debris avalanches that swept to the W and left a large
horseshoe-shaped caldera inside which the modern cone has been
constructed. Major explosive eruptions since the mid Holocene have
produced widespread tephra deposits and pyroclastic flows that swept
all but the southern flanks. A central cone slightly lower than the
caldera rim has been the site of numerous small-to-moderate historical
eruptions since the time of the Spanish conquistadors.

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


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

KVERT reported that seismic activity at Karymsky was above background
levels during 10-17 October. Possible explosions may have generated
ash plumes to an altitude of 3.1 km (10,200 ft) a.s.l. Analysis of
satellite imagery on 13 October revealed a thermal anomaly in the
crater and an ash plume about 5 km wide that drifted 32 km NNE. The
Level of Concern 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 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

HVO reported that during 15-21 October lava flowed SE through a tube
system from underneath Kilauea's Thanksgiving Eve Breakout (TEB) and
rootless shield complex, reaching the Waikupanaha ocean entry.
Multiple surface lava flows on the pali were noted; on 16 October a
channelized 'a'a flow was active in the Royal Gardens subdivision and
a pahoehoe flow was seen on the W side of the active flow field. Lava
destroyed one of two remaining intermittently occupied structures in
the subdivision. The sulfur dioxide emission rate at Pu'u 'O'o was
1,000 tonnes per day on 17 October, half of the background rate of the
2005-2007 average. Explosions at the ocean entry were reported on 19
October.

During the reporting period, Kilauea earthquakes were variously
located beneath and to the S of the caldera, and along the S-flank
faults. Beneath Halema'uma'u crater earthquakes ranged from 40 per day
to more than 100 (background is about 40), but were too small to be
located more precisely. The vent in Halema'uma'u crater continued to
produce a predominantly white plume, which was occasionally tinged
brown in association with small local earthquakes or vent rim
collapses, that drifted mainly SW. Night-time incandescence was
intermittently seen at the base of the plume. Two vent explosions
occurred on 14 October. The first was initiated by the collapse of a
thin piece of the vent rim. The second explosion ejected molten
spatter that fell within 100 m of the vent and produced an eruption
plume that rose 2 km above the caldera rim. The sulfur dioxide
emission rate was 600 and 900 tonnes per day on 16 and 17 October,
respectively. The 2003-2007 rate average was 140 tonnes per day.

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/


NYIRAGONGO Democratic Republic of Congo 1.52°S, 29.25°E; summit elev. 3470 m

Based on analysis of satellite imagery, the Toulouse VAAC reported a
diffuse sulfur plume from Nyiragongo on 17 October. The plume may have
contained some ash.

Geologic Summary. One of Africa's most notable volcanoes, Nyiragongo
contained an active lava lake in its deep summit crater that drained
catastrophically through its outer flanks in 1977. In contrast to the
low profile of its neighboring shield volcano, Nyamuragira, Nyiragongo
displays the steep slopes of a stratovolcano. Benches in the
steep-walled, 1.2-km-wide summit crater mark the levels of former lava
lakes, which have been observed since the late 19th century. About 100
parasitic cones are located on the volcano's flanks and along a NE-SW
zone extending as far as Lake Kivu. Monitoring is done from a small
observatory building located in Goma, ~18 km S of the Nyiragongo
crater.

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


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

OVPDLF reported that a seismic crisis at Piton de la Fournaise on 20
October was located beneath the summit at an elevation of 700 m a.s.l.
The crisis was accompanied by weak deformation.

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://ovpf.univ-reunion.fr/


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

CENAPRED reported emissions of steam and gas from Popocatépetl during
15-21 October. The plumes occasionally contained slight amounts of ash
on 20 and 21 October.

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 (SW Pacific) 4.271°S, 152.203°E; summit elev. 688 m

RVO reported that during 12-20 October ash plumes from Rabaul
caldera's Tavurvur cone rose to an altitude of 0.9-2.7 km (3,000-8,900
ft) a.s.l. and drifted N, NW, S, and SE. Ashfall was reported in areas
downwind. During 20-21 October, large explosions occurred and ash
plumes rose to altitudes of 1.7-3.7 km (5,600-12,100 ft) a.s.l. A
significant amount of ash fell in the area of Rabaul town (3-5 km NW).
Continuous incandescence from the vent was observed and loud roaring
noises were reported.

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: Ima Itikarai, Rabaul Volcano Observatory (RVO)


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

KVERT reported that seismic activity at Shiveluch was above background
levels during 10-17 October. Based on interpretations of seismic data,
a large number of hot avalanches descended the lava dome and produced
ash plumes that rose to an altitude of 6 km (19,700 ft) a.s.l.
Significant hot avalanches were seen on 13 October. Analysis of
satellite imagery revealed a thermal anomaly on the lava dome during
10-11 and 13-14 October, and steam-and-ash plumes with a small amount
of ash that drifted 30 km NE on 14 October. Fumarolic activity was
visible on the web camera during 10-13 and 16-17 October. The Level of
Concern Color Code remained at Orange.

Based on information from KEMSD and analysis of satellite imagery, the
Tokyo VAAC reported that during 18-20 October eruption plumes rose to
altitudes of 4.9-6.7 km (16,000-22,000 ft) a.s.l.

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. During the 1990s,
intermittent explosive eruptions took place 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 10-17 October the activity level at the
Soufrière Hills lava dome was low and consisted mainly of mudflows.
Mudflows were particularly numerous during 15-16 October due to the
passage of hurricane Omar to the N. Erosion of the talus slope on the
E side of the lava dome also significantly increased and, as a result,
a large gap in the talus was created that exposed the core of the
dome. During an overflight on 17 October the lava dome was seen
vigorously steaming, and thermal imagery revealed that the hottest
temperatures were associated with the new Gages vent formed in August.
The Hazard Level remained at 3.

Based on analysis of satellite imagery and information from MVO, the
Washington VAAC reported that on 20 October a pyroclastic flow or a
rockfall generated a plume that drifted about 45 km W.

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.

Sources: Montserrat Volcano Observatory (MVO) http://www.mvo.ms,
Washington Volcanic Ash Advisory Center (VAAC)
http://www.ssd.noaa.gov/VAAC/messages.html


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

Based on information from JMA, the Tokyo VAAC reported that explosions
from Suwanose-jima during 16 and 18-20 October produced plumes that
rose to altitudes of 1.2-2.4 km (4,000-8,000 ft) a.s.l. and drifted W.

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


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

The IG reported that multiple lahars and mudflows descended drainages
around Tungurahua on 14 October. A majority of the lahars traveled
down drainages in the Pampas sector to the S, carrying blocks an
average of 30-40 cm in diameter and up to 2 m in diameter. Other
lahars and small mudflows descended drainages to the NW and W. On 19
October a small lahar descended the Bilbao drainage to the 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/


UBINAS Perú 16.355°S, 70.903°W; summit elev. 5672 m

Based on SIGMET notices and pilot observations, the Buenos Aires VAAC
reported that on 15, 18, 20, and 21 October ash plumes were
continuously emitted from Ubinas and rose to altitudes of 4.9-7 km
(16,000-23,000 ft) a.s.l. The plumes drifted SE and NW.

Geologic Summary. A small, 1.2-km-wide caldera that cuts the top of
Ubinas, Peru's most active volcano, gives 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 Peru. The upper slopes of the stratovolcano, composed
primarily of Pleistocene andesitic lava flows, 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
extend 10 km from the volcano. Widespread Plinian pumice-fall deposits
from Ubinas include some of Holocene age. Holocene lava flows are
visible on the volcano's flanks, but historical activity, documented
since the 16th century, has consisted of intermittent minor explosive
eruptions.

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


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

==============================================================
To unsubscribe from the volcano list, send the message:
signoff volcano
to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx

To contribute to the volcano list, send your message to:
volcano@xxxxxxxx  Please do not send attachments.
==============================================================

[Index of Archives]     [Yosemite Backpacking]     [Earthquake Notices]     [USGS News]     [Yosemite Campgrounds]     [Steve's Art]     [Hot Springs Forum]

  Powered by Linux