GVP/USGS Weekly Volcanic Activity Report 19-25 December 2007

Kimberly Genareau <kgenarea@xxxxxxx> · Wed, 26 Dec 2007 17:04:56 -0700

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GVP/USGS Weekly Volcanic Activity Report
19 December-25 December 2007
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Sally Kuhn Sennert - Weekly Report Editor
URL: http://www.volcano.si.edu/reports/usgs/

This page is updated on Wednesdays, please see the GVP Home Page for
news of the latest significant activity.

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

GORELY Russia 52.558°N, 158.03°E; summit elev. 1829 m
On 25 December, KVERT reported that the Alert Level for Gorely was
raised to Yellow due to an increase in seismicity and visual
observations. Seismicity increased on 22 December and remained
slightly elevated above background levels during 22-25 December. A
gas-and-steam plume at an altitude of 2.2 km (7,200 ft) a.s.l. was
observed.

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)

MASAYA Nicaragua 11.984°N, 86.161°W; summit elev. 635 m

Based on observations of satellite imagery, the Washington VAAC
reported that a small and diffuse plume from Masaya, possibly
containing ash, drifted SW on 24 December. Changes in seismic signals
correlated with the emission.

Geologic Summary. Masaya is one of Nicaragua's most unusual and most
active volcanoes. It is a broad, 6 x 11 km basaltic caldera with
steep-sided walls up to 300 m high that is filled on its NW end by
more than a dozen vents erupted along a circular, 4-km-wide fracture
system. The twin volcanoes of Nindiri and Masaya, the source of
historical eruptions, were constructed at the southern end of the
fracture system and contain multiple summit craters. A major basaltic
Plinian tephra was erupted from Masaya about 6,500 years ago.
Historical lava flows cover much of the caldera floor and have
confined a lake to the far eastern end of the caldera. A lava flow
from the 1670 eruption overtopped the N caldera rim. Masaya has been
frequently active since the time of the Spanish Conquistadors, when an
active lava lake prompted several attempts to extract the volcano's
molten "gold."

Source: Washington Volcanic Ash Advisory Center (VAAC)

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

KVERT reported that seismic activity at Shiveluch was above background
levels during 14-21 December. Based on seismic interpretation, a
series of explosions during 18-19 December produced ash plumes that
rose to altitudes of 6.5-8.7 km (21,300-29,000 ft) a.s.l. Ash plumes
were observed on satellite imagery and drifted more than 130 km W on
18 December and 300 km to the NW and SW on 19 December. Ashfall was
reported in the town of Klyuchi, about 30 km SW on 19 December. Large
pyroclastic-flow deposits 8-9 km from the lava dome were observed to
the S. On 20 December, KVERT reported that the Level of Concern Color
Code was raised to Red. On 21 December, the Level of Concern Color
Code was lowered back to 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)

ULAWUN Papua New Guinea 5.05°S, 151.33°E; summit elev. 2334 m
Based on observations of satellite imagery, the Darwin VAAC reported
that an ash-and-steam plume from Ulawun drifted W on 25 December.

Geologic Summary. The symmetrical basaltic to andesitic Ulawun
stratovolcano is the highest volcano of the Bismarck arc, and one of
Papua New Guinea's most frequently active. Ulawun rises above the N
coast of New Britain opposite Bamus volcano. The upper 1,000 m of the
2,334-m-high volcano is unvegetated. A steep-walled valley cuts the NW
side of the volcano, and a flank lava-flow complex lies to the S of
this valley. Historical eruptions date back to the beginning of the
18th century. Twentieth-century eruptions were mildly explosive until
1967, but after 1970 several larger eruptions produced lava flows and
basaltic pyroclastic flows, greatly modifying the summit crater.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)

Ongoing Activity

ANATAHAN United States 16.35°N, 145.67°E; summit elev. 790 m
Low-level tremor at Anatahan continued during 14-21 December. On 14
December, the Washington VAAC reported that a steam plume was visible
on satellite data.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

BAGANA Papua New Guinea 6.140°S, 155.195°E; summit elev. 1750 m

Based on observations of satellite imagery and reports from the RVO,
the Darwin VAAC reported that a plume from Bagana rose to an altitude
of 3 km (10,000 ft) a.s.l. and drifted SW on 21 December. An
ash-and-steam plume was also visible on 26 December and drifted WSW.

Geologic Summary. Bagana volcano, occupying a remote portion of
central Bougainville Island, is one of Melanesia's youngest and most
active volcanoes. Bagana is a massive symmetrical lava cone largely
constructed by an accumulation of viscous andesitic lava flows. The
entire lava cone could have been constructed in about 300 years at its
present rate of lava production. Eruptive activity at Bagana is
characterized by non-explosive effusion of viscous lava that maintains
a small lava dome in the summit crater, although explosive activity
occasionally producing pyroclastic flows also occurs. Lava flows form
dramatic, freshly preserved tongue-shaped lobes up to 50-m-thick with
prominent levees that descend the volcano's flanks on all sides.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)

BARREN ISLAND India 12.278°N, 93.858°E; summit elev. 354 m

Based on observations of satellite imagery, the Darwin VAAC reported
that an ash plume from Barren Island rose to an altitude of 1.5 km
(5,000 ft) a.s.l. and drifted S on 23 December.

Geologic Summary. Barren Island, a possession of India in the Andaman
Sea about 135 km NE of Port Blair in the Andaman Islands, is the only
historically active volcano along the N-S-trending volcanic arc
extending between Sumatra and Burma (Myanmar). The 354-m-high island
is the emergent summit of volcano that rises from a depth of about
2,250 m. The small, uninhabited 3-km-wide island contains a roughly
2-km-wide caldera with walls 250-350 m high. The caldera, which is
open to the sea on the W, was created during a major explosive
eruption in the late Pleistocene that produced pyroclastic-flow and
-surge deposits. The morphology of a fresh pyroclastic cone that was
constructed in the center of the caldera has varied during the course
of historical eruptions. Lava flows fill much of the caldera floor and
have reached the sea along the western coast during historical
eruptions.

Source: Darwin Volcanic Ash Advisory Centre (VAAC)

COLIMA México 19.514°N, 103.62°W; summit elev. 3850 m

Steam and steam-and-ash plumes from Colima were observed rising to
altitudes of 4.3-4.7 km (14,100-15,400 ft) a.s.l. during 20-23 and 25
December. Plumes drifted N on 21 December.

Geologic Summary. The Colima volcanic complex is the most prominent
volcanic center of the western Mexican Volcanic Belt. It consists of
two southward-younging volcanoes, Nevado de Colima (the 4,320 m high
point of the complex) on the N and the historically active Volcán de
Colima on the S. Volcán de Colima (also known as Volcán Fuego) is a
youthful stratovolcano constructed within a 5-km-wide caldera,
breached to the S, that has been the source of large debris
avalanches. Major slope failures have occurred repeatedly from both
the Nevado and Colima cones, and have produced a thick apron of
debris-avalanche deposits on three sides of the complex. Frequent
historical eruptions date back to the 16th century. Occasional major
explosive eruptions (most recently in 1913) have destroyed the summit
and left a deep, steep-sided crater that was slowly refilled and then
overtopped by lava dome growth.

Source: Gobierno del Estado de Colima

CONCEPCION Nicaragua 11.538°N, 85.622°W; summit elev. 1700? m

According to a news article, INETER reported that an explosion from
Concepción on 20 December was followed by gas-and-ash plumes. Ashfall
was reported in nearby communities.

Geologic Summary. Volcán Concepción is one of Nicaragua's highest
volcanoes and is also one of its most active. The symmetrical volcano
forms the NW half of the dumbbell-shaped island of Ometepe in Lake
Nicaragua. Concepción is connected to neighboring Madera volcano by a
narrow isthmus. N-S-trending fractures cutting across the volcano are
associated with spatter cones, cinder cones, and maars located on the
middle N flank and on the lower S flank down to Lake Nicaragua.
Concepción has had frequent moderate explosive eruptions in the past
century, most of which have originated from a small summit crater.

Source: Associated Press

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

Based on observations of satellite imagery, the Washington VAAC
reported that ash plumes from Fuego rose to an altitude of 5.2 km
(17,000 ft) a.s.l. drifted SW on 21 December. Gas or ash plumes were
seen on satellite imagery on 23 December and drifted W. According to
CONRED, INSIVUMEH reported on 24 December that an ash plume drifted
SW. 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: Washington Volcanic Ash Advisory Center (VAAC) , Coordinadora
Nacional para la Reducción de Desastres (CONRED)

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

Based on overflights and web camera views, HVO reported that fissure
segment D from Kilauea's 21 July fissure eruption continued to feed
perched lava ponds within a lava flow that frequently overflowed their
channel edges during 19-25 December. Lava flowed from the base and top
of the Thanksgiving Eve Breakout (TEB) shield, and crust overturned in
multiple lava ponds. An overflight on 20 December revealed that lava
from fissure D built up two more shields SE of the TEB shield. A few
small earthquakes were located beneath the summit and Halema'uma'u
crater, and along 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. The latest Kilauea
eruption began in January 1983 along the E rift zone. This long-term
ongoing eruption from Pu`u `O`o-Kupaianaha has produced lava flows
that have traveled 11-12 km from the vents to the sea, paving about
104 km2 of land on the S flank of Kilauea and building 207 hectares of
new land.

Source: US Geological Survey Hawaiian Volcano Observatory

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

The Toulouse VAAC reported that an ash plume from Ol Doinyo Lengai was
observed by visiting scientists on 20 December and rose to an
unreported altitude.

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)

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

According to CONRED, a 17 December INSIVUMEH report noted changes in
Pacaya's behavior. On 19 December, CONRED issued a bulletin noting
that INSIVUMEH reported observations of white and blue "smoke" plumes.
The plumes rose to an altitude of 2.8 km (9,200 ft) a.s.l. and drifted
S. Lava flows were unchanged from previous days. Based on these
reports, CONRED raised the Alert Level to Yellow in surrounding
communities.

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.

Source: Coordinadora Nacional para la Reducción de Desastres (CONRED)

SAKURA-JIMA Japan 31.585°N, 130.657°E; summit elev. 1117 m

Based on information from JMA, the Tokyo VAAC reported that eruption
plumes from Sakura-jima rose to an altitude of 2.7 km (9,000 ft)
a.s.l. and drifted S during 23-24 December.

Geologic Summary. Sakura-jima, one of Japan's most active volcanoes,
is a post-caldera cone of the Aira caldera at the northern half of
Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow was
associated with the formation of the 17 x 23-km-wide Aira caldera
about 22,000 years ago. The construction of Sakura-jima began about
13,000 years ago and built an island that was finally joined to the
Osumi Peninsula during the major explosive and effusive eruption of
1914. Activity at the Kita-dake summit cone ended about 4,850 years
ago, after which eruptions took place at Minami-dake. Frequent
historical eruptions, recorded since the 8th century, have deposited
ash on Kagoshima, one of Kyushu's largest cities, located across
Kagoshima Bay only 8 km from the summit. The largest historical
eruption took place during 1471-76.

Source: Tokyo Volcanic Ash Advisory Center (VAAC)

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

Based on observations of satellite imagery, the Washington VAAC
reported that an ash plume from Santa María's Santiaguito lava dome
complex rose to an altitude of 5.2 km (17,000 ft) a.s.l. and drifted
SW on 21 December.

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: Washington Volcanic Ash Advisory Center (VAAC)

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

MVO reported that during 17-24 December 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 of the dome 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

ST. HELENS United States 46.20°N, 122.18°W; summit elev. 2549 m
Data from deformation-monitoring instruments indicated that during
19-25 December 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

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-and-steam and ash plumes from
Tungurahua were observed and rose to altitudes of 6-8.5 km
(19,700-28,000 ft) a.s.l. during 19-25 December. Plumes drifted SE,
SW, and WNW. Ashfall was reported in areas to the SW, W, NW, and N.
Roaring noises and "cannon shots" were heard almost daily and windows
and floors vibrated on 19, 21, and 23-24 December. On 19, 22, and 23
December, incandescent blocks were seen rolling hundreds of m down the
flanks. Sounds indicating rolling blocks on the flanks were reported
during 20-22 December, but were not observed due to cloud cover.

According to news articles, nearly 1,200 people in Penipe were
evacuated nightly by security, and specific communities around the
volcano remained at an Orange Alert level.

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 , Associated Press

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 5.5-7 km (18,000-23,000 ft) a.s.l.
and drifted NE and SW during 24-25 December.

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)

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