SI/USGS Weekly Volcanic Activity Report 27 August-2 September 2008

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

 



SI/USGS Weekly Volcanic Activity Report
27 August-2 September 2008

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


New Activity/Unrest: | Kasatochi, Andreanof Islands | Piton de la
Fournaise, Reunion Island | Soufrière Hills, Montserrat

Ongoing Activity: | Batu Tara, Komba Island (Indonesia) | Chaitén,
Southern Chile | Chikurachki, Paramushir Island | Dukono, Halmahera
(Indonesia) | Karymsky, Eastern Kamchatka | Kilauea, Hawaii (USA) |
Llaima, Central Chile | Nevado del Huila, Colombia | Nyiragongo,
Democratic Republic of Congo | Okmok, Fox Islands | Rabaul, New
Britain (SW Pacific) | Semeru, Eastern Java (Indonesia) | Shiveluch,
Central Kamchatka (Russia) | Taal, Luzon | 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


KASATOCHI Andreanof Islands 52.177°N, 175.508°W; summit elev. 314 m

AVO reported that during 27 August-2 September seismic activity from
Kasatochi detected by stations on Great Sitkin, approximately 40 km W,
declined. Clouds prevented satellite image observations. The Volcano
Alert Level remained at Watch and the Aviation Color Code at Orange.

Geologic Summary. Located at the northern end of a shallow submarine
ridge trending perpendicular to the Aleutian arc, Kasatochi is small
2.7 x 3.3 km wide island volcano with a dramatic 750-m-wide summit
crater lake. The summit of Kasatochi reaches only 314 m above sea
level, and the lake surface lies less than about 60 m above the sea. A
lava dome is located on the NW flank at about 150 m elevation. The
asymmetrical island is steeper on the northern side than the southern,
and the volcano's crater lies north of the center of the island.
Reports of activity from the heavily eroded Koniuji volcano to the
east probably refer to eruptions from Kasatochi. A lava flow may have
been emplaced during the first historical eruption in 1760.

Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/


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

OVPDLF reported an increase of seismic activity beneath the summit of
Piton de la Fournaise on 31 August. Deformation was also detected at
the top of Dolomieu and, coupled with the increase in seismicity,
prompted OVPDLF to raise the Alert level to 1. Public access to the
summit was prohibited. On 2 September, the Alert Level was lowered
because seismicity had decreased.

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/


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

MVO reported that during 22-29 August, observations suggested that the
W side of the Soufrière Hills lava dome continued to grow. Lahars
descended numerous river valleys during 25-27 August. Incandescence
originating from a scar on the lava dome created by the 28 July
explosion, and then further expanded by a pyroclastic flow on 25
August, was observed on clear nights. Incandescence was also observed
from an area N of the scar. Rockfalls descended the W side of the
dome. 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/


Ongoing Activity


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
on 2 September a low-level ash plume from Batu Tara 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 clouds obscured camera views of Chaitén's
eruption plume during most of 26-29 August. Glimpses utilizing the web
camera revealed that continuous ash plumes rose to an altitude of 1.5
km (4,900 ft) a.s.l. and drifted SW. They also reported that
seismicity had increased slightly during the previous few days.

Based on web camera views and analysis of satellite imagery, the
Buenos Aires VAAC reported that during 27-29 August ash plumes rose to
altitudes of 1.8-3 km (6,000-10,000 ft) a.s.l. and drifted SE.

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


CHIKURACHKI Paramushir Island 50.325°N, 155.458°E; summit elev. 1816 m

KVERT reported that clouds mostly prevented satellite image views of
Chikurachki during 22-29 August. No ash plumes were observed during
times of clearer weather. The level of seismicity was unknown because
Chikurachki lacks dedicated seismic instruments. The Level of Concern
Color Code was lowered to Yellow.

Geologic Summary. Chikurachki, the highest volcano on Paramushir
Island in the northern Kurils, is actually a relatively small cone
constructed on a high Pleistocene volcanic edifice. Oxidzed scoria
deposits covering the upper part of the young cone give it a
distinctive red color. Lava flows from 1816-m-high Chikurachki reached
the sea and form capes on the NW coast; several young lava flows also
emerge from beneath the scoria blanket on the eastern flank. The more
erosionally modified Tatarinov group of six volcanic centers is
located immediately to the S of Chikurachki. Tephrochronology gives
evidence of only one eruption in historical time from Tatarinov,
although its southern cone contains a sulfur-encrusted crater with
fumaroles that were active along the margin of a crater lake until
1959.

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


DUKONO Halmahera (Indonesia) 1.68°N, 127.88°E; summit elev. 1335 m

Based on analysis of satellite imagery, the Darwin VAAC reported that
on 2 September a low-level ash plume from Dukono drifted WNW.

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 at Karymsky was at background
levels during 21-23 August and above background levels during 24-27
August. Possible explosions may have generated ash plumes to an
altitude of 3.2 km (10,500 ft) a.s.l. Analysis of satellite imagery
revealed a thermal anomaly in the crater during 24 and 26-28 August
and that an ash plumes drifted SE on 27 August. The Level of Concern
Color Code remained at Orange.

Based on analysis of satellite imagery and information from KEMSD, the
Tokyo VAAC reported that on 29 August and 2 September eruption plumes
rose to an approximate altitude of 3 km (10,000 ft) a.s.l.

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.

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


KILAUEA Hawaii (USA) 19.421°N, 155.287°W; summit elev. 1222 m

HVO reported that during 27 August-2 September, lava flowed SE through
a lava tube system from underneath Kilauea's Thanksgiving Eve Breakout
(TEB) and rootless shield complex and reached the Waikupanaha ocean
entry. On 31 August, students from the University of Hawaii at Hilo
reported low-level explosive activity at Waikupanaha.

A high number of Kilauea's earthquakes were centered in various
locations along the Koa'e fault system, beneath the summit, N of
Kupaianaha, along the S-flank faults, and along the E and SW rift
zones. Beneath Halema'uma'u crater, more than 40 and up to 400 small
earthquakes per day (background 40) also occurred but were too small
to be located more precisely. The vent in Halema'uma'u crater
continued to produce a predominantly white plume with minor ash
content that drifted mainly SW. The plume was occasionally tinged
brown. Weak night-time incandescence was intermittently seen at the
base of the plume, and rock impacts and muted rushing sounds were
heard in the vicinity of the crater. During 26-27 August, multiple ash
ejections were observed. On 27 August, the white plume was temporarily
tinged brown and rose to a higher altitude following an explosive
eruption (the fifth in 2008). Glass fragments and tephra up to 5 cm in
diameter burned holes in a collection tarp placed near the overlook.
Analysis of photos captured over the previous month showed that the
vent had lengthened by almost 50 percent along the edge of the crater
floor. On 29 August, the collection bin contained Pele's hair, Pele's
tears, and a variety of other shapes of glass fragments.

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/


LLAIMA Central Chile 38.692°S, 71.729°W; summit elev. 3125 m

On 2 September, SERNAGEOMIN reported that clouds had prevented visual
observations of Llaima during the previous few days. Explosions were
heard during 25-28 August. On 28 August, seismic signals indicated
that gas-and-ash plumes were possibly emitted from the pyroclastic
cones in the main crater. The Volcanic Alert Level remained at Yellow.

Geologic Summary. Llaima, one of Chile's largest and most active
volcanoes, contains two main historically active craters, one at the
summit and the other to the SE. The massive 3,125-m-high,
glacier-covered stratovolcano has a volume of 400 cu km. A Holocene
edifice built primarily of accumulated lava flows was constructed over
an 8-km-wide caldera that formed about 13,200 years ago, following
eruption of the 24 cu km Curacautín Ignimbrite. More than 40 scoria
cones dot the volcano's flanks. Following the end of an explosive
stage about 7,200 years ago, construction of the present edifice
began, characterized by Strombolian, Hawaiian, and infrequent
subplinian eruptions. Frequent moderate explosive eruptions with
occasional lava flows have been recorded since the 17th century.

Source: Servicio Nacional de Geología y Minería (SERNAGEOMIN)
http://www.sernageomin.cl/index.php


NEVADO DEL HUILA Colombia 2.93°N, 76.03°W; summit elev. 5365 m

INGEOMINAS reported that on 2 September a M 4.6 earthquake at Nevado
del Huila was detected 2.2 km NE of Pico Central. The Alert Level
remained at Yellow (on a 4-color scale where Yellow is the second
lowest).

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//


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
that an eruption of unstated character from Nyiragongo occurred before
0300 on 2 September. The activity was not confirmed by ground
observations. Nyiragongo's frequently active lava lake is often
detected on MODIS satellite thermal imagery.

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


OKMOK Fox Islands 53.43°N, 168.13°W; summit elev. 1073 m

On 27 August, AVO lowered the Volcano Alert Level for Okmok to
Advisory and the Aviation Color Code to Yellow because seismicity had
declined steadily during 20-27 August and ash plumes had not been
observed since 19 August. On 28 August, a thermal anomaly and a steam
plume were detected on satellite imagery. Cloud cover prevented
observations on the other days.

Geologic Summary. The broad, basaltic Okmok shield volcano, which
forms the NE end of Umnak Island, has a dramatically different profile
than most other Aleutian volcanoes. The summit of the low, 35-km-wide
volcano is cut by two 10-km-wide calderas formed during eruptions
about 8,250 and 2,400 years ago that produced dacitic pyroclastic
flows that reached the coast. Numerous satellitic cones and lava domes
dot the flanks of the volcano down to the coast. Some of the
post-caldera cones show evidence of wave-cut lake terraces; the more
recent cones, some of which have been active historically, were formed
after the caldera lake disappeared. Hot springs and fumaroles are
found within the caldera and at Hot Springs Cone, 20 km to the SW.
Historical eruptions have occurred since 1805 from cinder cones within
the caldera.

Source: Alaska Volcano Observatory (AVO) http://www.avo.alaska.edu/


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

RVO reported that ash plumes from Rabaul caldera's Tavurvur cone
continued to be emitted during 29-31 August. The plumes drifted NW and
caused ashfall in areas downwind. Continuous incandescence at the
summit was observed and roaring noises were heard. Explosions also
ejected incandescent lava fragments.

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)


SEMERU Eastern Java (Indonesia) 8.108°S, 112.92°E; summit elev. 3676 m

Based on pilot observations, the Darwin VAAC reported that a low-level
plume from Semeru was present on 28 August. A pilot reported that an
ash plume rose to an altitude of 4.6 km (15,000 ft) a.s.l. and drifted
SW on 31 August.

Geologic Summary. Semeru is the highest volcano on Java and one of its
most active. The symmetrical stratovolcano rises abruptly to 3,676 m
above coastal plains to the S and lies at the southern end of a
volcanic massif extending N to the Tengger caldera. Semeru has been in
almost continuous eruption since 1967. Frequent small-to-moderate
Vulcanian eruptions have accompanied intermittent lava dome extrusion,
and periodic pyroclastic flows and lahars have damaged villages below
the volcano. A major secondary lahar on 14 May 1981 caused more than
250 deaths and damaged 16 villages.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)
http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html


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

KVERT reported that seismic activity at Shiveluch was slightly above
background levels during 22-29 August. Gas-and-steam plumes with a
small amount of ash were generated from avalanches during 22 and 25-28
August. Analysis of satellite imagery revealed a daily thermal anomaly
on the lava dome and that steam-and-ash plumes drifted 80 km SE on 26
and 27 August. The Level of Concern Color Code remained at Orange.

Geologic Summary. The high, isolated massif of Shiveluch volcano (also
spelled Sheveluch) rises above the lowlands NNE of the Kliuchevskaya
volcano group 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.

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


TAAL Luzon 14.002°N, 120.993°E; summit elev. 311 m

PHIVOLCS reported ongoing seismic unrest at Taal on 28 August. Ten
earthquakes occurred; two at Intensity II were felt by residents in
the Pira-Piraso village and were accompanied by rumbling sounds. The
earthquakes were located NE of the island near the Daang Kastila area
at estimated depths of 0.6-0.8 km. Surface observations indicated no
change in the main crater lake area. PHIVOLCS warned that the main
crater was off-limits to the general public. The Alert Level remained
at 1 (scale is 0-5, 0 referring to No Alert status).

Geologic Summary. Taal volcano is one of the most active volcanoes in
the Philippines and has produced some of its most powerful historical
eruptions. In contrast to Mayon volcano, Taal is not topographically
prominent, but its prehistorical eruptions have greatly changed the
topography of SW Luzon. The 15 x 20 km Taal caldera is largely filled
by Lake Taal, whose 267 sq km surface lies 700 m below the S caldera
rim and only 3 m above sea level. The maximum depth of the lake is 160
m, and several eruptive centers lie submerged beneath the lake. The
5-km-wide Volcano Island in north-central Lake Taal is the location of
all historical eruptions. The island is a complex volcano composed of
coalescing small stratovolcanoes, tuff rings, and scoria cones that
has grown about 25% in area during historical time. Powerful
pyroclastic flows and surges from historical eruptions of Taal have
caused many fatalities.

Source: Philippine Institute of Volcanology and Seismology (PHIVOLCS)
http://www.phivolcs.dost.gov.ph/


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

Based on SIGMET reports, analysis of satellite imagery, and pilot
observations, the Buenos Aires VAAC reported that during 26-27 August
and on 2 September continuous ash plumes from Ubinas rose to altitudes
of 5.5-6.1 km (18,000-20,000 ft) a.s.l. Plumes drifted N on 27 August
and S on 2 September.

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