GVP/USGS Weekly Volcanic Activity Report 16-22 January 2008

Kimberly Genareau <kgenarea@xxxxxxx> · Wed, 23 Jan 2008 13:25:51 -0700

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GVP/USGS Weekly Volcanic Activity Report
16-22 January 2008
Sally Kuhn Sennert - Weekly Report Editor
kuhns@xxxxxx
URL: http://www.volcano.si.edu/reports/usgs/
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New Activity/Unrest: | Galeras, Colombia | Llaima, Central Chile |
Nevado del Huila, Colombia

New Activity/Unrest

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

INGEOMINAS issued a report at 1000 on 17 January, noting that the
seismic pattern from Galeras observed during the previous 24 hours was
similar to patterns noted before past eruptions. Later that day, at
2006, an explosive eruption was registered by the seismic network and
prompted INGEOMINAS to raise the Alert Level from 3 ("changes in the
behavior of volcanic activity have been noted") to 1 ("imminent
eruption or in course"), on a scale of 4-1.

Based on observations of satellite imagery and information from
INGEOMINAS, the Washington VAAC reported that an ash plume rose to an
altitude of 11 km (36,000 ft) a.s.l. at 2216 and drifted W on 17
January.

On 19 January, INGEOMINAS lowered the Alert Level to 2 ("likely
eruption in days or weeks") because seismic events decreased in
occurrence and energy. On 21 January, INGEOMINAS further lowered the
Alert Level to 3 and reported that the initial ash plume from the
eruption drifted SW, then W. Fine Ashfall was collected in Túquerres
(about 32 km to the SW) and very fine ash was observed in
neighborhoods of Ricaurte (about 71 km to the W). About 2 km away,
military personnel reported that blocks 1.5 m in diameter were noted
on a highway.

According to a news article, small settlements to the N were ordered
to evacuate; about 100 people moved to shelters.

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.

Sources: Instituto Colombiano de Geología y Minería
http://www.ingeominas.gov.co/

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

Associated Press
http://www.univision.com/contentroot/wirefeeds/50noticias/7382530.html#

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

SERNAGEOMIN reported that eruptive activity at Llaima continued from
the main crater and from two craters and a fissure on the E flank
during 16-21 January. Based on observations during an overflight on 16
January, three nested pyroclastic cones within the main crater were
active. The larger cone produced weak ash emissions that rose about
500 m. Ash emissions were also noted from a crater on the E flank.
Glaciers on the NE slope and W flank were fractured and dislocated.
Ash emissions from a NE-SW-trending fissure about 80 m in length and
10 m wide were observed. Also noted were incandescent rocks that
rolled from the NE end of the fissure and ash plumes generated from
rolling rocks in multiple areas during 16-17 January. On 17 January,
ash emissions rose from the main crater to an altitude of 3.5 km
(11,500 ft) a.s.l and drifted E. Weak Strombolian activity was seen
from the main crater during aerial observation.

At 0732 on 18 January, a lateral explosion from the E side produced an
ash plume that rose to an altitude of 9.1 km (29,900 ft) a.s.l. and
quickly dispersed NE. Later that day, a small lateral explosion from
the same area and ash-and-gas emissions from several points and new
fissures were noted.

On 19 January, an explosion from the E flank produced an ash plume
that rose to an altitude of 4.1 km (13,500 ft) a.s.l. An overflight
revealed Strombolian activity in the main crater from a pyroclastic
cone that was 120 m in diameter and 100 m high. The cone was not
present during the overflight on 17 January. A second crater to the SW
emitted gas. Sporadic ash emissions were noted from the E sector and
an explosion produced a pyroclastic flow and an ash plume that quickly
dissipated. On 20 January, another explosion produced an ash plume
that rose to an altitude of 4.1 km (13,500 ft) a.s.l. Gas and ash
emissions were again noted from multiple areas. On 21 January, cloud
cover inhibited visual observations; one small ash emission was noted
at the end of the day.

Geologic Summary. Llaima, one of Chile's largest and most active
volcanoes, contains two 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/

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

Based on aerial observations from a commercial flight on 19 January,
INGEOMINAS reported that ash deposits from Nevado del Huila were seen
on the W sector of a summit glacier, confirming the seismic
interpretation from the previous month.

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//

Ongoing Activity

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

The USGS reported that on several days during 12-20 January, sulfur
dioxide plumes from Anatahan were detected by the satellite-based
Ozone Monitoring Instrument (OMI). Seismic tremor increased on 16
January and remained elevated on 20 January. The Volcanic Alert Level
remained at Advisory and the Aviation Color Code remained at Yellow.

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.

Source: 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

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

Based on overflights and web camera views when weather permitted, HVO
reported that during 16-22 January activity from Kilauea's fissure
segment D was concentrated at the Thanksgiving Eve Breakout (TEB)
shield and satellitic shields to the SE. Lava flows from the tops and
flanks of the shields traveled S and E. During 16-19 January,
incandescence was observed in Pu'u 'O'o crater for less than 10
minutes at a time. During 18-19 January, the summit tiltmeter network
recorded the first DI (deflation-inflation) tilt event since October
2007. A few small earthquakes were located beneath the summit,
Halema'uma'u crater, and Pulama pali, and along the upper and lower E
rift zones and S-flank fault.

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
http://volcano.wr.usgs.gov/hvostatus.php

KRAKATAU Indonesia 6.102°S, 105.423°E; summit elev. 813 m

According to a news article, incandescent rocks erupted and plumes
from Anak Krakatau rose to altitudes of 2.8-3.3 km (9,200-10,800 ft)
a.s.l. on 20 January. Eruptions reportedly had a "deafening sound" and
could be seen from Sertung and Rakata islands.

Geologic Summary. Renowned Krakatau volcano lies in the Sunda Strait
between Java and Sumatra. Collapse of the ancestral Krakatau edifice,
perhaps in 416 AD, resulted in a 7-km-wide caldera. Remnants of this
volcano formed Verlaten and Lang Islands; subsequently Rakata, Danan
and Perbuwatan volcanoes were formed, coalescing to create the
pre-1883 Krakatau Island. Caldera collapse during the catastrophic
1883 eruption destroyed Danan and Perbuwatan volcanoes, and left only
a remnant of Rakata volcano. The post-collapse cone of Anak Krakatau
(Child of Krakatau), constructed within the 1883 caldera at a point
between the former cones of Danan and Perbuwatan, has been the site of
frequent eruptions since 1927.

Source: Antara News
http://www.antara.co.id/en/arc/2008/1/21/red-hot-rocks-hurled-from-anak-krakatau-reach-25-km-high/

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

A visitor to Ol Doinyo Lengai reported that it erupted on 14 January.
A "shower of stones" fell at their location about 50 m from the summit
and a lava flow went another direction.

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: Frederick Belton's Ol Doinyo Lengai website
http://www.mtsu.edu/~fbelton/lengai.html

POAS Costa Rica 10.20°N, 84.233°W; summit elev. 2708 m

According to a news article, an eruption of volcanic material and
gases from Poás rose to an altitude of 2.9 km (9,500 ft) a.s.l. on 13
January. The article also stated that a report from OVSICORI-UNA on 22
January revealed that an eruption of gas propelled material that did
not fall beyond the cone. Authorities evacuated 20 people in the
vicinity of the eruption.

Geologic Summary. The broad, well-vegetated edifice of Poás, one of
the most active volcanoes of Costa Rica, contains three craters along
a N-S line. The frequently visited multi-hued summit crater lakes of
the basaltic-to-dacitic volcano, which is one of Costa Rica's most
prominent natural landmarks, are easily accessible by vehicle from the
nearby capital city of San José. A N-S-trending fissure cutting the
2,708-m-high complex stratovolcano extends to the lower northern
flank, where it has produced the Congo stratovolcano and several
lake-filled maars. The southernmost of the two summit crater lakes,
Botos, is cold and clear and last erupted about 7,500 years ago. The
more prominent geothermally heated northern lake, Laguna Caliente, is
one of the world's most acidic natural lakes, with a pH of near zero.
It has been the site of frequent phreatic and phreatomagmatic
eruptions since the first historical eruption was reported in 1828.
Poás eruptions often include geyser-like ejection of crater-lake
water.

Source: Nacion.com http://www.nacion.com/ln_ee/2008/enero/22/sucesos1394799.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 0.8-1 km (2,600-3,300 ft) a.s.l. and drifted E and SE
during 17-20 and 22-23 January. On 17 January ashfall was reported in
Tokua, about 20 km SE, prompting Air Niugini to cancel some flights.
During 18-20 January, the ash plumes were released at 10-20 minute
intervals. White plumes were emitted on 21 and 22 January.
Incandescence from the center of the crater was visible at night
during 17-22 January.

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: Steve Saunders and Herman Patia, Rabaul Volcano Observatory

SHIVELUCH Sredinny Range 56.653°N, 161.360°E; summit elev. 3283 m

KVERT reported that seismic activity at Shiveluch was above background
levels during 11-18 January. Based on seismic interpretation, ash
plumes rose to an altitude of 4.1 km (13,500 ft) a.s.l. on 12 and 16
January. Ash plumes at an altitude of 4.5 km (14,800 ft) a.s.l. were
visible on the Shiveluch web camera on 16 January. Strong fumarolic
activity was noted during 15-17 January. Based on observations of
satellite imagery, a thermal anomaly was present in the crater every
day. 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/updates.shtml

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

MVO reported that during 15-22 January the lava dome at Soufrière
Hills changed very little, based on visual observations. Seismic
activity was very low and low-level rockfall activity continued.
Fumarolic activity on the N and E flanks continued. Active fumaroles
were also noted in the Galway's area to the S of the dome and W in the
Gages Wall area. 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 http://www.mvo.ms/

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

Data from deformation-monitoring instruments indicated that during
16-22 January lava-dome growth at Mount St. Helens continued.
Seismicity persisted at low levels, punctuated by M 1.5-2.5 and
occasionally larger earthquakes. Clouds occasionally inhibited visual
observations.

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
http://volcano.wr.usgs.gov/cvo/current_updates.php

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

IG reported that although visual observations were occasionally
limited due to cloud cover, ash plumes were spotted and rose to
altitudes of 5.5-9 km (18,000-29,500 ft) a.s.l. during 16-22 January.
Ashfall was reported daily in areas mainly to the W, SW, and NW, and
was heavy on 20 January. Roaring noises and "cannon shots" were heard
frequently and windows and floors vibrated on 15, 20, and 21 January,
as far away as the Tungurahua Observatory (OVT) in Guadalupe, about 13
km NW. On 16 January, incandescent blocks were propelled 200 m above
the crater during a Strombolian eruption phase and blocks rolled 1 km
down the flank. Three explosions produced blocks that rolled 2 km down
the flanks. A small pyroclastic flow traveled 400 m down the NW side
of the crater. Incandescence at the crater was again noted on 17 and
21 January.

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
http://www.igepn.edu.ec/

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