GVP/USGS Weekly Volcanic Activity Report 20-26 February 2008

Kimberly Genareau <kgenarea@xxxxxxx> · Wed, 27 Feb 2008 16:57:55 -0400

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GVP/USGS Weekly Volcanic Activity Report
20-26 February 2008
Sally Kuhn Sennert - Weekly Report Editor
kuhns@xxxxxx
URL: http://www.volcano.si.edu/reports/usgs/
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New Activity/Unrest: | Lopevi, Vanuatu (SW Pacific) | Veniaminof,
Alaska Peninsula

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

LOPEVI Vanuatu (SW Pacific) 16.507°S, 168.346°E; summit elev. 1413 m

Based on a pilot report, the Wellington VAAC reported that an ash
plume from Lopevi rose to an altitude of below 3 km (10,000 ft) a.s.l.
on 24 February.

Geologic Summary. The small 7-km-wide conical island of Lopevi is one
of Vanuatu's most active volcanoes. A small summit crater containing a
cinder cone is breached to the NW and tops an older cone that is
rimmed by the remnant of a larger crater. The basaltic-to-andesitic
volcano has been active during historical time at both summit and
flank vents, primarily on the NW and SE sides, producing moderate
explosive eruptions and lava flows that reached the coast. Historical
eruptions at the 1,413-m-high volcano date back to the mid-19th
century. The island was evacuated following eruptions in 1939 and
1960. The latter eruption, from a NW-flank fissure vent, produced a
pyroclastic flow that swept to the sea and a lava flow that formed a
new peninsula on the western coast.

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

VENIAMINOF Alaska Peninsula 56.17°N, 159.38°W; summit elev. 2507 m

AVO reported that on 22 February several minor ash bursts from
Veniaminof were recorded by the seismic network and observed on web
camera footage. The bursts rose to an altitude of below 2.7 km (9,000
ft) a.s.l. but fallout was confined to the crater. Sporadic increases
in seismic activity were noted since 11 February, including tremor
episodes that lasted 1-2 minutes and occurred several times per hour.
The Aviation color code was raised to Yellow and the Alert Level was
raised to Advisory. Steam plumes emitted from the intra-caldera cinder
cone were seen on video footage during 23-25 February and seismic
levels were elevated during 23-26 February.

Geologic Summary. Massive Veniaminof volcano, one of the highest and
largest volcanoes on the Alaska Peninsula, is truncated by a
steep-walled, 8 x 11 km, glacier-filled caldera that formed around
3,700 years ago. The caldera rim is up to 520 m high on the N, is
deeply notched on the W by Cone Glacier, and is covered by an ice
sheet on the S. Post-caldera vents are located along a NW-SE zone
bisecting the caldera that extends 55 km from near the Bering Sea
coast, across the caldera, and down the Pacific flank. Historical
eruptions probably all originated from the westernmost and most
prominent of two intra-caldera cones, which reaches an elevation of
2,156 m and rises about 300 m above the surrounding icefield. The
other cone is larger, and has a summit crater or caldera that may
reach 2.5 km in diameter, but is more subdued and barely rises above
the glacier surface.

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

Ongoing Activity

ANATAHAN Mariana Islands (Central Pacific) 16.35°N, 145.67°E; summit elev. 790 m

The USGS reported that emissions of sulfur dioxide from Anatahan were
detected by the satellite-based Ozone Monitoring Instrument (OMI)
during 20-25 February. Seismicity was elevated during 20-26 February,
though levels varied greatly during 23-25 February. The Washington
VAAC reported that plumes possibly containing some ash were visible on
satellite imagery drifting WSW, SW, E, W, and SE during 20 and 23-24
February. A Volcanic Haze Advisory was issued by the Emergency
Management Office (EMO) on 25 February for Tinian, Saipan, and Rota
because of elevated sulfur dioxide levels. This advisory was cancelled
on 26 February. The Volcanic Alert Level remained at Watch and the
Aviation Color Code remained at Orange.

Geologic Summary. The elongate, 9-km-long island of Anatahan in the
central Mariana Islands consists of large stratovolcano with a 2.3 x 5
km, E-W-trending compound summit caldera. The larger western caldera
is 2.3 x 3 km wide, and its western rim forms the island's 790-m high
point. Ponded lava flows overlain by pyroclastic deposits fill the
floor of the western caldera, whose SW side is cut by a fresh-looking
smaller crater. The 2-km-wide eastern caldera contained a steep-walled
inner crater whose floor prior to the 2003 eruption was only 68 m
above sea level. Sparseness of vegetation on the most recent lava
flows on Anatahan had indicated that they were of Holocene age, but
the first historical eruption of Anatahan did not occur until May
2003, when a large explosive eruption took place forming a new crater
inside the eastern caldera.

Sources: Emergency Management Office of the Commonwealth of the
Mariana Islands and the US Geological Survey Hawaiian Volcano
Observatory http://volcano.wr.usgs.gov/cnmistatus.php

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

Saipan Tribune http://www.saipantribune.com/newsstory.aspx?newsID=77395&cat=1

CLEVELAND Chuginadak Island 52.825°N, 169.944°W; summit elev. 1730 m

AVO reported that a low-level ash plume from Cleveland was visible on
satellite imagery and drifted about 300 km SE on 22 February. The
Volcanic Alert Level remained at Advisory and the Aviation Color Code
remained at Yellow.

Geologic Summary. Symmetrical Mount Cleveland stratovolcano is
situated at the western end of the uninhabited dumbbell-shaped
Chuginadak Island in the east-central Aleutians. The 1,730-m-high
stratovolcano is the highest of the Islands of Four Mountains group
and is one of the most active in the Aleutians. Numerous large lava
flows descend its flanks. It is possible that some 18th to 19th
century eruptions attributed to Carlisle (a volcano located across the
Carlisle Pass Strait to the NW) should be ascribed to Cleveland. In
1944 Cleveland produced the only known fatality from an Aleutian
eruption. Recent eruptions from Mt. Cleveland have been characterized
by short-lived explosive ash emissions, at times accompanied by lava
fountaining and lava flows down the flanks.

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

KERINCI Sumatra (Indonesia) 1.697°S, 101.264°E; summit elev. 3800 m

CVGHM reported that white plumes from Kerinci rose to altitudes of
4.1-4.3 km (13,500-14,100 ft) a.s.l. during 14-18 February. The Alert
Status remained at 2 (on a scale of 1-4). Residents and visitors were
advised not to enter an area within 1 km of the summit.

Geologic Summary. The summit of 3800-m-high Kerinci, Indonesia's
highest volcano, contains a deep 600-m-wide crater often partially
filled by a small crater lake. The massive 13 x 25 km wide volcano
towers 2,400-3,300 m above surrounding plains. Kerinci is elongated in
a N-S direction and is capped by an unvegetated young summit cone
constructed NE of an older crater remnant. One of Sumatra's most
active volcanoes, Gunung Kerinci has produced a series of moderate
explosive eruptions during the 19th and 20th centuries.

Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)
http://portal.vsi.esdm.go.id/joomla/

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

Based on observations during overflights, and web camera views when
weather permitted, HVO reported that during 20-26 February activity
from Kilauea's fissure segment D was concentrated at the Thanksgiving
Eve Breakout (TEB) shield and satellitic shields to the E and SE. A
lava flow from the shields traveled E towards Kalalua. A pahoehoe lava
flow from the SE rootless shield was observed 250 m S of the northern
boundary of the Royal Gardens subdivision during an overflight on 20
February. During 25-26 February, lava flows advanced through the
subdivision. Diffuse incandescence was observed in Pu'u 'O'o crater
through the fume during 20-22 February. Earthquakes were located E of
and beneath Halema'uma'u crater, along the S-flank faults, beneath the
summit, N of the summit, and along the SW rift zones.

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

SERNAGEOMIN reported that weak steam plumes were observed from
Llaima's main crater on 20 February. The 'a'a lava flow that traveled
2.5 km during 2-13 February varied in width between 30-40 m and was 10
m thick. On 21 February small ash plumes rose from the E and SE
flanks. Pyroclastic flows descended the E flank and possibly down the
W flank. Sulfur dioxide plumes that rose from two craters within the
main crater were visible during an overflight. On 22 February, a
seismic signal pattern similar to that observed during a previous
pyroclastic flow was noted. Ash-and-gas plumes rose from the E flank.
On 23 February, an ash-and-gas plume rose from the SE flank.

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

OL DOINYO LENGAI Tanzania 2.764°S, 35.914°E; summit elev. 2962 m

The Toulouse VAAC reported that a plume from Ol Doinyo Lengai was
observed by pilots on 21 February and rose to an altitude of 18.3 km
(60,000 ft) a.s.l. Based on a Significant Meteorological Information
(SIGMET) report, an ash plume rose to an altitude of 14 km (46,000 ft)
a.s.l. on 24 February.

Geologic Summary. The symmetrical Ol Doinyo Lengai stratovolcano is
the only volcano known to have erupted carbonatite tephras and lavas
in historical time. The prominent volcano, known as "The Mountain of
God," rises abruptly above the broad plain S of Lake Natron. The
cone-building stage of the volcano ended about 15,000 years ago and
was followed by periodic ejection of natrocarbonatite and nephelinite
tephra during the Holocene. Historical eruptions have consisted of
smaller tephra eruptions and emission of numerous natrocarbonatitic
lava flows on the floor of the summit crater. Petrologists first
observed the eruption of carbonatitic lava flows in the 1960s.
Subsequent more frequent visits have documented long-term lava
effusion in the summit crater that would not have been seen from the
foot of the volcano.

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

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

CENAPRED reported that emissions of steam and gas from Popocatépetl
were visible during 20-26 February. The plumes occasionally contained
slight amounts of ash. Explosions on 21 and 22 February resulted in
ash plumes that rose to an altitude of 7.4 km (24,300 ft) a.s.l. and
drifted NE. Incandescent fragments were ejected from the crater and
fell on the flanks. On 22 February, the ejected fragments fell on the
SE flank.

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.

Sources: Centro Nacional de Prevencion de Desastres (CENAPRED)
http://www.cenapred.unam.mx/es/

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

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 rose
to altitudes of 1.7-2.7 km (5,600-8,900 ft) a.s.l. and drifted E, SE,
S, and SW during 20-27 February. Roaring noises were occasionally
heard. Ashfall was reported in areas mainly downwind, including Kokopo
Town (SE), Takubar (SW), and Tokua (SE), during 21-25 February.
Incandescence at the summit was noted during 22-24 February. On 25
February an explosion showered the flanks with lava fragments. On 26
February a large explosion was accompanied by a thick billowing ash
plume that rose to an altitude of 3.7 km (12,100 ft) a.s.l. and
drifted SE and E. The flanks were again showered with lava fragments.
Ashfall was reported in Kokopo and surrounding areas.

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: Herman Patia and Steve Saunders, 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 slightly above
background levels during 15-22 February. Based on seismic
interpretation, ash plumes possibly rose to an altitude of 3 km
(10,000 ft) a.s.l. on 17 and 20 February. During the reporting period
strong fumarolic activity was seen daily on video footage and a
thermal anomaly was present in the crater on satellite imagery. 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

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

MVO reported that that during 20-26 February the lava dome at
Soufrière Hills changed very little, based on limited visual
observations during an over flight on 21 February and from ground
locations. The E talus flank continued to erode and both fresh and
older material accumulated in the Tar River Valley to the E. Active
fumaroles around the lava dome were observed during the overflight.
Seismic activity was very low and low-level rockfall activity
continued. The Alert Level remained elevated at 4 (on a scale of 0-5).

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/

ST. HELENS Washington (USA) 46.20°N, 122.18°W; summit elev. 2549 m

On 21 February, CVO lowered the Alert Level for Mount St. Helens from
Watch to Advisory and the Aviation Color Code from Orange to Yellow.
Comparison of photographs taken by remote cameras during late January
to mid-February 2008 showed no evidence of extrusion. In addition,
very few earthquakes were recorded since late January, gas emissions
were barely detectable, and daily ground-tilt events stopped.

Geologic Summary. Prior to 1980, Mount St. Helens formed a conical,
youthful volcano sometimes known as the Fuji-san of America. During
the 1980 eruption the upper 400 m of the summit was removed by slope
failure, leaving a 2 x 3.5 km horseshoe-shaped crater now partially
filled by a lava dome. Mount St. Helens was formed during nine
eruptive periods beginning about 40-50,000 years ago, and has been the
most active volcano in the Cascade Range during the Holocene. The
modern edifice was constructed during the last 2,200 years, when the
volcano produced basaltic as well as andesitic and dacitic products
from summit and flank vents. Historical eruptions in the 19th century
originated from the Goat Rocks area on the N flank, and were witnessed
by early settlers.

Source: Cascades Volcano Observatory (CVO) http://vulcan.wr.usgs.gov/

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

IG reported that although visual observations were very limited due to
storm cloud cover, gas-and-steam and ash-and-steam plumes from
Tungurahua were spotted and rose to altitudes of 5.5-7 km
(18,000-23,000 ft) a.s.l. during 20-26 February. Ash plumes drifted
mainly W and SW and ashfall was reported in areas downwind on 19, 23,
and 26 February. Lahars or mudflows affected roads in the Pampas
sector to the S on 19, 20, and 25 February.

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 pilot reports, the Buenos Aires VAAC reported that ash plumes
from Ubinas rose to altitudes of 5.5-8.5 km (18,000-28,000 ft) a.s.l.
and drifted SE on 23 February.

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

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