GVP/USGS Weekly Volcanic Activity Report 9-15 January 2008

Kimberly Genareau <kgenarea@xxxxxxx> · Wed, 16 Jan 2008 15:55:42 -0700

*************************************************************
GVP/USGS Weekly Volcanic Activity Report
9-15 January 2008
Sally Kuhn Sennert - Weekly Report Editor
kuhns@xxxxxx
URL: http://www.volcano.si.edu/reports/usgs/
************************************************************

New Activity/Unrest: | Llaima, Chile | Nevado del Huila, Colombia |
Popocatépetl, México | Tungurahua, Ecuador

New Activity/Unrest

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

SERNAGEOMIN reported that seismicity from Llaima decreased in energy,
but the number of events increased during 10-14 January. Based on
seismic interpretation, weak explosions produced plumes of gas and
ash. On 11 January, lava flows on the W flank that were observed
during an overflight were cooled and snow-covered near the crater but
snow-free, and therefore still hot, about 500 m further down on the
flank. Blocks of incandescent material rolled about 1.5 km and caused
steam emissions at several points where they contacted the glacier.
Ash plumes drifted NE. Abundant cracks in glaciers to the SW of the
crater were noted. Based on observations of satellite imagery and
pilot reports, the Buenos Aires VAAC reported that ash plumes rose to
an altitude of 5.5-6.7 km (18,000-22,000 ft) a.s.l. and drifted NE and
SW on 11 and 13 January, respectively.

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.

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

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

Based on seismic interpretation, INGEOMINAS reported ash emissions
from Nevado del Huila on 2, 7, and 12 January.

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//

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 9-14 January. The plumes occasionally contained
slight amounts of ash during 9-12 January. On 14 January,
high-frequency seismic tremor was followed by an explosion that
produced ash emissions and propelled fragments from the crater.

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 (CENEPRED)
http://www.cenapred.unam.mx/es/

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

IG released a special report on 9 January noting that increased
seismic activity at Tungurahua was comparable to that of the few days
prior to the eruption of 14 July, 2006.

IG reported that although visual observations were occasionally
limited due to cloud cover, ash-and-steam and ash plumes were observed
and rose to altitudes of 6-9 km (19,700-29,500 ft) a.s.l. during 9-15
January. Ashfall was reported almost daily in areas to the NE, N, NW,
W, and SW. Roaring noises and "cannon shots" were heard daily and
windows and floors vibrated on 9, 10, 12, and 15 January, as far away
as the Tungurahua Observatory (OVT) in Guadalupe, about 13 km NW.
Incandescence at the summit was observed and incandescent blocks
rolled 0.5-1 km down the flanks. On 11 January, Strombolian activity
at the summit crater was observed and blocks rolled 600 m down the
flank.

According to news articles, residents from two provinces continued to
evacuate at night and about 20,000 health masks were distributed to
residents from Baños and Quero.

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.

Sources: Instituto Geofísico-Escuela Politécnica Nacional
http://www.igepn.edu.ec/,

Pan American Health Organization
http://www.reliefweb.int/rw/RWB.NSF/db900SID/LSGZ-7AVJ95?OpenDocument

Ongoing Activity

ARENAL Costa Rica 10.463°N, 84.703°W; summit elev. 1670 m

In December, activity originating from Arenal's Crater C consisted of
gas emissions, sporadic Strombolian eruptions, and occasional
avalanches from lava-flow fronts that traveled down the SW flank.
Volcanic activity was at relatively low levels and few eruptions
occurred. Acid rain and small amounts of ejected pyroclastic material
affected the NE and SE flanks. Eruptions produced ash plumes that rose
about 2.2 km (7,100 ft) a.s.l. Small avalanches of volcanic material
traveled down several ravines. Crater D showed only fumarolic
activity.

Geologic Summary. Conical Volcan Arenal is the youngest stratovolcano
in Costa Rica and one of its most active. The 1,657-m-high andesitic
volcano towers above the eastern shores of Lake Arenal, which has been
enlarged by a hydroelectric project. The earliest known eruptions of
Arenal took place about 7,000 years ago. Growth of Arenal has been
characterized by periodic major explosive eruptions at
several-hundred-year intervals and periods of lava effusion that armor
the cone. Arenal's most recent eruptive period began with a major
explosive eruption in 1968. Continuous explosive activity accompanied
by slow lava effusion and the occasional emission of pyroclastic flows
has occurred since then from vents at the summit and on the upper
western flank.

Source: Observatorio Vulcanologico y Sismologico de Costa
Rica-Universidad Nacional (OVSICORI-UNA)

http://www.ovsicori.una.ac.cr/

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

INSIVUMEH reported on 11 January that weak explosions from Fuego
produced ash plumes that rose to altitudes of 4.1-4.3 km
(13,500-14,100 ft) a.s.l. CONRED reiterated that the Alert Level
remained at Yellow.

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

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

Coordinadora Nacional para la Reducción de Desastres (CONRED)

http://www.conred.org/principal.php

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

INGEOMINAS reported that steam-and-gas plumes from Galeras rose to an
altitude of 6.3 km (20,700 ft) a.s.l. on 12 January. The emissions
occasionally contained ash and were associated with episodes of
spasmodic volcanic tremor.

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
http://www.ingeominas.gov.co//

GORELY Russia 52.558°N, 158.03°E; summit elev. 1829 m

KVERT reported on 11 January that seismic activity in the area of
Gorely and Mutnovsky volcanoes was slightly elevated above background
levels during the previous three weeks, but increasing activity was
not confirmed. There is only one seismic station in the area of the
two volcanoes so the source of the seismicity cannot be determined.
Activity was not observed on satellite imagery. The level of Concern
Color Code was lowered to Green.

Geologic Summary. Gorely volcano, one of the most active in southern
Kamchatka, consists of five small overlapping stratovolcanoes
constructed along a WNW-ESE line within a large 9 x 13.5 km
late-Pleistocene caldera. The massive Gorely complex contains 11
summit and 30 flank craters. During the early Holocene, activity was
characterized by frequent mild eruptions with occasional larger
explosions and lava flows that filled in the caldera. Quiescent
periods became longer between 6,000 and 2,000 years ago, after which
the activity was mainly explosive. About 600-650 years ago
intermittent strong explosions and lava flow effusion accompanied
frequent mild eruptions. Historical eruptions have consisted of
vulcanian and phreatic explosions of moderate volume.

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

KILAUEA United States 19.421°N, 155.287°W; summit elev. 1222 m

Based on overflights and web camera views when weather permitted, HVO
reported that during 2-8 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 were noted from
the tops and flanks of the shields and traveled S and E. On 8 January,
the SE-most shield breached on the SE flank and issued a vigorous and
channelized 'a'a lava flow. The 'a'a flow advanced SE during 8-10
January and stalled approximately 480-650 m from the upper reaches of
the Royal Gardens subdivision on 10 January. On 13 January, one of
four narrow and secondary lava flows initiated from the 8 January 'a'a
flow, advancing along the E margin to 180 m N of the subdivision.

According to a news article, most of the upper portion of the Royal
Gardens subdivision was abandoned after lava flows cut the highway
that provided access to the subdivision during Kilauea's ongoing
25-year eruption. County officials later cleared a path through the
cooled lava for a few remaining residents.

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.

Sources: US Geological Survey Hawaiian Volcano Observatory
http://hvo.wr.usgs.gov/,

The Honolulu Advertiser
http://the.honoluluadvertiser.com/article/2008/Jan/10/br/br2605398741.html

MUTNOVSKY Russia 52.453°N, 158.195°E; summit elev. 2322 m

KVERT reported on 11 January that seismic activity in the area of
Mutnovsky and Gorely volcanoes was slightly elevated above background
levels during the previous three weeks, but increasing activity was
not confirmed. There is only one seismic station in the area of the
two volcanoes so the source of the seismicity cannot be determined.
Activity was not observed on satellite imagery. The level of Concern
Color Code was lowered to Green.

Geologic Summary. Massive Mutnovsky, one of the most active volcanoes
of southern Kamchatka, is formed of four coalescing stratovolcanoes of
predominately basaltic composition. Multiple summit craters cap the
volcanic complex. Growth of Mutnovsky IV, the youngest cone, began
during the early Holocene. An intracrater cone was constructed along
the northern wall of the 1.3-km-wide summit crater. Abundant flank
cinder cones were concentrated on the SW side. Holocene activity was
characterized by mild-to-moderate phreatic and phreatomagmatic
eruptions from the summit crater. Historical eruptions have been
explosive, with lava flows produced only during the 1904 eruption.
Geothermal development is planned at Mutnovsky, which has the highest
heat capacity of any volcano in the Kuril-Kamchatka arc.

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

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

INSIVUMEH reported on 11 January that continuous effusion of lava on
Pacaya's W flank resulted in a 150-200 m-long lava flow. Fumaroles
produced white and blue plumes that drifted S, and incandescence at
night was observed from the summit. CONRED reiterated that the Alert
Level remained at Yellow.

Geologic Summary. Eruptions from Pacaya, one of Guatemala's most
active volcanoes, are frequently visible from Guatemala City, the
nation's capital. Pacaya is a complex volcano constructed on the
southern rim of the 14 x 16 km Pleistocene Amatitlan caldera. A
cluster of dacitic lava domes occupies the caldera floor. The Pacaya
massif includes the Cerro Grande lava dome and a younger volcano to
the SW. Collapse of Pacaya volcano about 1,100 years ago produced a
debris-avalanche deposit that extends 25 km onto the Pacific coastal
plain and left an arcuate somma rim inside which the modern Pacaya
volcano (MacKenney cone) grew. During the past several decades,
activity at Pacaya has consisted of frequent Strombolian eruptions
with intermittent lava flow extrusion on the flanks of MacKenney cone,
punctuated by occasional larger explosive eruptions.

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

Coordinadora Nacional para la Reducción de Desastres (CONRED)

http://www.conred.org/principal.php

PAPANDAYAN Indonesia 7.32°S, 107.73°E; summit elev. 2665 m

On 7 January, CVGHM lowered the Alert Level at Papandayan from 2 to 1
(on a scale of 1-4) due to a decrease in activity over approximately
four months. Seismic events decreased in number after 2 August 2007,
and earthquake tremor was not recorded since 14 November 2007. Data
from deformation-monitoring instruments indicated deflation. White
fumarolic plumes rose to an altitude of 2.9 km (9,500 ft) a.s.l.

Geologic Summary. Papandayan is a complex stratovolcano with four
large summit craters, the youngest of which was breached to the NE by
collapse during a brief eruption in 1772 and contains active fumarole
fields. The broad 1.1-km-wide, flat-floored Alun-Alun crater truncates
the summit of Papandayan, and Gunung Puntang to the N gives the
volcano a twin-peaked appearance. Several episodes of collapse have
given the volcano an irregular profile and produced debris avalanches
that have impacted lowland areas beyond the volcano. Since its first
historical eruption in 1772, in which a catastrophic debris avalanche
destroyed 40 villages, only two small phreatic eruptions have occurred
from vents in the NE-flank fumarole field, Kawah Mas.

Source: Center of Volcanology and Geological Hazard Mitigation (CVGHM)

http://portal.vsi.esdm.go.id/joomla/

RABAUL Papua New Guinea 4.271°S, 152.203°E; summit elev. 688 m

RVO reported that intermittent ash and vapor plumes from Rabaul
caldera's Tavurvur cone were observed during 8-15 January. On 11
January, a small explosion produced an ash plume that rose to
altitudes of 1.2-1.5 km (3,900-4,900 ft) a.s.l. and drifted SE. During
11-15 January, ash and vapor plumes rose to altitudes of 0.9-1.2 km
(3,000-3,900 ft) a.s.l. and drifted SE, E, NE, N, and W. Slight
ashfall was reported about 20 km SE in Tokua on 11 and 12 January.
Data from deformation-monitoring instruments indicated no deformation.
Incandescence from the lava dome on the crater floor was occasionally
visible at night.

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

SANTA MARIA Guatemala 14.756°N, 91.552°W; summit elev. 3772 m

INSIVUMEH reported on 11 January that constant avalanches on the W and
SW flanks of Santa María's Santiaguito lava dome complex were noted.
Explosions produced ash plumes that rose to altitudes of 4.1-4.5 km
(13,500-14,800 ft) a.s.l. and drifted SW.

Geologic Summary. Symmetrical, forest-covered Santa María volcano is
one of a chain of large stratovolcanoes that rises dramatically above
the Pacific coastal plain of Guatemala. The stratovolcano has a
sharp-topped, conical profile that is cut on the SW flank by a large,
1-km-wide crater, which formed during a catastrophic eruption in 1902
and extends from just below the summit to the lower flank. The
renowned Plinian eruption of 1902 followed a long repose period and
devastated much of SW Guatemala. The large dacitic Santiaguito
lava-dome complex has been growing at the base of the 1902 crater
since 1922. Compound dome growth at Santiaguito has occurred
episodically from four westward-younging vents, accompanied by almost
continuous minor explosions and periodic lava extrusion, larger
explosions, pyroclastic flows, and lahars.

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

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

KVERT reported that seismic activity at Shiveluch was above background
levels during 4-11 January. Based on seismic interpretation, ash
plumes rose to an altitude of 6.3 km (20,700 ft) a.s.l. during 3-4, 6,
and 9 January. Strong fumarolic activity was noted during 7-9 January.
Based on observations of satellite imagery, a gas-and-steam plume
drifted NW on 3 January and a thermal anomaly was present in the
crater every day during the reporting period. The Level of Concern
Color Code remained at Orange.

Based on information from the KEMSD, the Tokyo VAAC reported that
eruption plumes rose to altitudes of 4.9 and 4.6 km (16,000 and 15,000
ft) a.s.l. on 10 and 16 January, respectively.

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 United Kingdom 16.72°N, 62.18°W; summit elev. 915 m

MVO reported that fumarolic activity on the N and E flanks of the
Soufrière Hills lava dome continued during 28 December-15 January.
Active fumaroles were also noted in the Galway's area to the S of the
dome and W in the Gages Wall area. Occasional rockfalls occurred; one
produced a small ash plume on 7 January. Observations during an
overflight on 9 January confirmed that the lava dome morphology had
not changed since 3 January. The Alert Level remained elevated at 4
(on a scale of 0-5).

Based on pilot reports, information from MVO, and observations of
satellite imagery, the Washington VAAC reported that a steam-and-gas
plume with light ash content drifted S and SW on 10 January.

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 http://www.mvo.ms/,

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

ST. HELENS United States 46.20°N, 122.18°W; summit elev. 2549 m

Data from deformation-monitoring instruments indicated that during
9-15 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://vulcan.wr.usgs.gov/

TURRIALBA Costa Rica 10.025°N, 83.767°W; summit elev. 3340 m

OVSICORI-UNA reported that fumarolic activity and gas discharge in and
to the W of Turrialba's central crater continued throughout December.
Some fumaroles were 278 degrees C and exhibited sulfur sublimate
deposition. Fumarolic plumes were visible from many kilometers away.
Gases were emitted from cracks on the S external wall and burned
vegetation was noted. Vegetation on the internal walls to the SW and
towards the E was withered.

Geologic Summary. Turrialba, the easternmost of Costa Rica's Holocene
volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano
located across a broad saddle NE of Irazú volcano overlooking the city
of Cartago. The massive 3340-m-high Turrialba is exceeded in height
only by Irazú, covers an area of 500 sq km, and is one of Costa Rica's
most voluminous volcanoes. Three well-defined craters occur at the
upper SW end of a broad 800 x 2200 m wide summit depression that is
breached to the NE. Most activity at Turrialba originated from the
summit vent complex, but two pyroclastic cones are located on the SW
flank. Five major explosive eruptions have occurred at Turrialba
during the past 3500 years. Turrialba has been quiescent since a
series of explosive eruptions during the 19th century that were
sometimes accompanied by pyroclastic flows. Fumarolic activity
continues at the central and SW summit craters.

Source: Observatorio Vulcanológico y Sismológico de Costa
Rica-Universidad Nacional (OVSICORI-UNA)

http://www.ovsicori.una.ac.cr/

+++++++++++++++++++++++++++++++++++++
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.
==============================================================