GVP/USGS Weekly Volcanic Activity Report 5-11 December 2007

Kimberly Genareau <kgenarea@xxxxxxx> · Thu, 13 Dec 2007 17:06:51 -0800

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GVP/USGS Weekly Volcanic Activity Report
5 December-11 December 2007
http://www.volcano.si.edu/reports/usgs/
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New Activity/Unrest: | Lokon-Empung, Indonesia | Turrialba, Costa Rica

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

LOKON-EMPUNG Indonesia 1.358°N, 124.792°E; summit elev. 1580 m

CVGHM raised the Alert Level for Lokon-Empung from 2 to 3 (on a scale
of 1-4) on 9 December based on visual observations, inflation detected
by deformation instruments, and an increase in seismicity. The water
in the Tompaluan crater changed color from green to gray and noises
from degassing became stronger. White plumes rose from the crater to
an altitude of 1.6 km (5,200 ft) a.s.l. Visitors and tourists were
advised not to go within a 2-km radius of the crater.

Geologic Summary. The twin volcanoes Lokon and Empung, rising about
800 m above the plain of Tondano, are among the most active volcanoes
of Sulawesi. Lokon, the higher of the two peaks (whose summits are
only 2.2 km apart) has a flat, craterless top. The morphologically
younger Empung volcano has a 400-m-wide, 150-m-deep crater that
erupted last in the 18th century, but all subsequent eruptions have
originated from Tompaluan, a 150 x 250 m wide double crater situated
in the saddle between the two peaks. Historical eruptions have
primarily produced small-to-moderate ash plumes that have occasionally
damaged croplands and houses, but lava-dome growth and pyroclastic
flows have also occurred.

Map

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

Lokon-Empung Information from the Global Volcanism Program

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

OVSICORI-UNA reported that members of the media and local communities
observed a gas-and-steam plume from Turrialba that rose to an altitude
greater than 5.3 km (17,400 ft) a.s.l. on 5 December. Fieldwork
confirmed an unusual output of gas from several fumaroles along the S
outer wall. Areas burned by acute acidification have extended in the
last month. Pastures turned yellowish near the upper areas, and native
and exotic tree species were impacted as well as birch tree patches
along most drainages. Within the W crater, temperatures of fumaroles
reached 280 degrees Celsius and native sulfur was present.

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.

Map

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

Turrialba Information from the Global Volcanism Program

Ongoing Activity

ANATAHAN United States 16.35°N, 145.67°E; summit elev. 790 m

Low-level tremor at Anatahan continued during 30 November-7 December.
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.

Map

Source: Emergency Management Office of the Commonwealth of the Mariana
Islands and the US Geological Survey Hawaiian Volcano Observatory

Anatahan Information from the Global Volcanism Program

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

In November, activity originating from Arenal's Crater C consisted of
gas emissions, sporadic Strombolian eruptions, lava flows traveling
down the S flank, and occasional avalanches from lava-flow fronts.
Blocks from near the edge of the crater rolled down the SE and SW
flanks. 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.

Map

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

Arenal Information from the Global Volcanism Program

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

RVO reported that during 18 October-10 December white vapor plumes
from Bagana were occasionally accompanied by ash plumes generated by
rockfalls from the edges of the lava flow on the SE flank.
Occasionally, booming and roaring noises were heard and incandescence
at the summit was observed. Two explosions were accompanied by ash
plumes on 19 and 27 November. Incandescent lava fragments were ejected
from the summit on 7 and 9 December. On 9 December, an ash plume rose
to an altitude of 2.8 km (9,200 ft) a.s.l. A lava flow became active
and was continuously incandescent down the SE flank.

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.

Map

Source: Herman Patia, Rabaul Volcano Observatory

Bagana Information from the Global Volcanism Program

KARYMSKY Russia 54.05°N, 159.45°E; summit elev. 1536 m

KVERT reported that seismic activity at Karymsky was slightly above
background levels during 30 November-7 December. A decrease in
activity based on observations of satellite imagery during November
and December 2007 prompted KVERT to lower the Level of Concern Color
Code to Yellow on 7 December.

Geologic Summary. Karymsky, the most active volcano of Kamchatka's
eastern volcanic zone, is a symmetrical stratovolcano constructed
within a 5-km-wide caldera that formed about 7,600-7,700 radiocarbon
years ago. Construction of the Karymsky stratovolcano began about
2,000 years later. The latest eruptive period began about 500 years
ago, following a 2,300-year quiescence. Much of the cone is mantled by
lava flows less than 200 years old. Historical eruptions have been
Vulcanian or Vulcanian-Strombolian with moderate explosive activity
and occasional lava flows from the summit crater. Most seismicity
preceding Karymsky eruptions has originated beneath Akademia Nauk
caldera, which is located immediately S of Karymsky volcano and
erupted simultaneously with Karymsky in 1996.

Map

Source: Kamchatkan Volcanic Eruption Response Team (KVERT)

Karymsky Information from the Global Volcanism Program

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

HVO reported that web camera views of fissure D from Kilauea's 21 July
fissure eruption were mostly blocked by fog and fumes during 5-9
December. A brief view on 5 December revealed several overflows on the
W side of Pond 1, a perched lava pond in the eruption channel formed
by fissure D. A pilot report from an overflight on 6 December noted
that all of the activity was close to fissure D and none of the SE
Thanksgiving Eve breakout (TEB) flows traveled beyond 1.5 km. On 8
December, minor incandescence was observed in Pu'u 'O'o crater for the
first time since 31 August, and was accompanied by a possible
inflationary signal. Clear web camera views on 9 and 10 December
revealed that the TEB shield continued to build vertically and was an
estimated 15 m high. A few small earthquakes were located beneath the
summit area and along the upper E rift zone 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. 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.

Map

Source: US Geological Survey Hawaiian Volcano Observatory

Kilauea Information from the Global Volcanism Program

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

RVO reported on 10 December that after five weeks of low-level
activity from Rabaul, ash was emitted from a new vent in the NE crater
during 8-9 December. Resultant ash plumes rose to an altitude of 2.6
km (8,500 ft) a.s.l. and drifted S during 8-10 December. Occasional
roaring noises were heard. Continuous incandescence from the lava dome
on the crater floor was 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.

Map

Source: Herman Patia, Rabaul Volcano Observatory

Rabaul Information from the Global Volcanism Program

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

KVERT reported that seismic activity at Shiveluch was above background
levels during 30 November-7 December. Based on seismic interpretation,
ash plumes rose to an altitude of 5.3 km (17,000 ft) a.s.l. and hot
avalanches occurred. Visual observations and video footage analysis
indicated that gas-and-steam plumes rose to altitudes of 4-5 km
(13,100-16,400 ft) a.s.l. during the reporting period. One ash plume
rose to an altitude of 5.7 km (18,700 ft) a.s.l. on 2 December. Based
on observations of satellite imagery, a thermal anomaly was present in
the crater every day during 30 November-7 December. The Level of
Concern Color Code remained at Orange.

Based on information from the KEMSD, the Tokyo VAAC reported that an
eruption plume rose to an altitude of 5.2 km (17,000 ft) a.s.l. on 10
December.

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.

Map

Sources: Kamchatkan Volcanic Eruption Response Team (KVERT) , Tokyo
Volcanic Ash Advisory Centre (VAAC)

Shiveluch Information from the Global Volcanism Program

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

MVO reported that during 3-7 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.

Map

Source: Montserrat Volcano Observatory

Soufrière Hills Information from the Global Volcanism Program

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

Data from deformation-monitoring instruments indicated that during
5-11 December lava-dome growth at Mount St. Helens continued. Based on
interpretations of flow-monitoring system data, lahars flowed out of
the crater on 4 December, after a weather system passed through the
region. 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.

Map

Source: Cascades Volcano Observatory

St. Helens Information from the Global Volcanism Program

SUWANOSE-JIMA Japan 29.635°N, 129.716°E; summit elev. 799 m

Based on information from JMA, the Tokyo VAAC reported that eruption
plumes from Suwanose-jima rose to altitudes of 1.5-1.8 km (5,000-6,000
ft) a.s.l. on 10 December and drifted W. Ash was not visible on
satellite imagery.

Geologic Summary. The 8-km-long, spindle-shaped island of
Suwanose-jima in the northern Ryukyu Islands consists of an andesitic
stratovolcano with two historically active summit craters. Only about
50 persons live on the sparsely populated island. The summit of the
volcano is truncated by a large breached crater extending to the sea
on the east flank that was formed by edifice collapse. Suwanose-jima,
one of Japan's most frequently active volcanoes, was in a state of
intermittent Strombolian activity from On-take, the NE summit crater,
that began in 1949 and lasted nearly a half century. The largest
historical eruption took place in 1813-14, when thick scoria deposits
blanketed residential areas, after which the island was uninhabited
for about 70 years. The SW crater produced lava flows that reached the
western coast in 1813, and lava flows reached the eastern coast of the
island in 1884.

Map

Source: Tokyo Volcanic Ash Advisory Center (VAAC)

Suwanose-jima Information from the Global Volcanism Program

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 rose to altitudes of 6-8 km (19,700-26,200 ft) a.s.l.
during 5-11 December. Plumes drifted SW, W, and NW. During 5-8
December, incandescence at the summit was observed and roaring noises
and "cannon shots" were heard. During 6-7 December, incandescent
material was propelled out of the crater and rolled about 1 km down
the flanks. Explosions shook the ground and rattled windows in
multiple areas, including at the Tungurahua Observatory (OVT) in
Guadalupe, 11 km N. During 5-8 December, ashfall was reported in areas
to the SW, W, and NW.

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.

Map

Source: Instituto Geofísico-Escuela Politécnica Nacional

Tungurahua Information from the Global Volcanism Program

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

Based on Significant Meteorological Information (SIGMET) advisories
and 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 N and NE during 4-7 and 10 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.

Map

Source: Buenos Aires Volcanic Ash Advisory Center (VAAC)

Ubinas Information from the Global Volcanism Program

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

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