Yfirlit yfir eldvirkni í vikuna 20 – 26 Desember, 2006

Hérna er yfirlit yfir eldvirkni á plánetunni vikuna 20 – 26 Desember, 2006. Þessi listi er fengin frá GVP/USGS. Athugið að listin er birtur eins og ég fæ hann.

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GVP/USGS Weekly Volcanic Activity Report
20-26 December 2006
http://www.volcano.si.edu/
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New Activity/Unrest: | Bezymianny, Russia | Shiveluch, Russia | Soufrière
Hills, Montserrat
Ongoing Activity: | Bagana, Papua New Guinea | Bulusan, Philippines | Dukono,
Indonesia | Karymsky, Russia | Kilauea, USA | Langila, Papua New Guinea |
Popocatépetl, México | Sangay, Ecuador | Semeru, Indonesia | St. Helens, USA |
Suwanose-jima, Japan | Tungurahua, Ecuador | Ulawun, Papua New Guinea

New Activity/Unrest

BEZYMIANNY Kamchatka Peninsula, Russia 55.98°N, 160.59°E; summit elev. 2,882
m

The level of Concern Color Code for Bezymianny was raised from Yellow to Orange
on 24 December due to an increase in incandescent avalanches, seismicity, and
the intensity of a thermal anomaly at the summit. Within a few hours, a series
of ash explosions and „ash avalanches“ produced plumes that rose to altitudes
of 6-10 km (19,700-32,800 ft) a.s.l. and drifted NE. The level of Concern Color
Code was raised to Red. On 25 December, KVERT reported that seismic activity
returned to background levels and explosive activity ceased. The level of
Concern Color Code was returned to Orange.

Geologic Summary. Prior to its noted 1955-56 eruption, Bezymianny volcano had
been considered extinct. The modern Bezymianny volcano, much smaller in size
than its massive neighbors Kamen and Kliuchevskoi, was formed about 4700 years
ago over a late-Pleistocene lava-dome complex and an ancestral volcano that was
built between about 11,000-7000 years ago. Three periods of intensified
activity have occurred during the past 3000 years. The latest period, which was
preceded by a 1,000-year quiescence, began with the dramatic 1955-56 eruption.
This eruption, similar to that of Mount St. Helens in 1980, produced a large
horseshoe-shaped crater that was formed by collapse of the summit and an
associated lateral blast. Subsequent episodic but ongoing lava-dome growth,
accompanied by intermittent explosive activity and pyroclastic flows, has
largely filled the 1956 crater.

Source: Kamchatkan Volcanic Eruption Response Team
http://www.kscnet.ru/ivs/kvert/updates.shtml

Bezymianny Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-25=

SHIVELUCH Kamchatka Peninsula, Russia 56.653°N, 161.360°E; summit elev. 3,283 m

According to observations, video data, and satellite imagery KVERT reported
that ash plumes from Shiveluch rose to 10 km (32,800 ft) a.s.l. and drifted E
on 16-17 and 20 December. Seismic activity was generally at background levels.
Based on satellite imagery, the Tokyo VAAC reported that a possible eruption
plume rose to an altitude of 9.1 km (30,000 ft) a.s.l. and drifted E on 24
December. Seismic and video data on 26 December indicated an ash plume above 10
km (32,800 ft.) a.s.l., extending 150 km NE in satellite imagery. The level of
Concern Color Code was raised from Orange to Red
.

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 horseshoe-shaped 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
http://www.kscnet.ru/ivs/kvert/updates.shtml,
Tokyo Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html

Shiveluch Information from the Global Volcanism Program
http://www.volcano.si.edu/gvp/world/volcano.cfm?vnum=1000-27=

SOUFRIÈRE HILLS Montserrat, West Indies 16.72°N, 62.18°W; summit elev. 1,052 m

During 15-22 December, moderate lava-dome growth at Soufrière Hills continued
and was focused on the SW part of the dome. Rockfalls and pyroclastic flows
occurred on the S side of the dome and in the upper parts of both White’s and
Tuitt’s Ghauts. Based on satellite imagery and pilot reports, the Washington
VAAC reported that steam emissions with variable amounts of ash drifted W on 23
and 24 December. A pilot reported that an ash plume rose to an altitude of 3 km
(10,000 ft) a.s.l. and drifted W on 24 December. The MVO reported that the
emissions originated from a vent on the W side of the dome. A small pyroclastic
flow was visible NW in the upper reaches of Tyre’s Ghaut and venting became
more energetic. The alert level was raised to 4 (on a scale of 0-5). At night,
incandescent rockfalls were visible from the NW and W.

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 east, was
formed during an eruption about 4000 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
http://www.ssd.noaa.gov/VAAC/messages.html

Soufrière Hills Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1600-05=

Ongoing Activity

BAGANA Bougainville Island, Papua New Guinea 6.14°S, 155.19°E; summit elev.
1,750 m

The Darwin VAAC reported that ash-and-steam plumes from Bagana were visible on
satellite imagery during 21-22 December drifting ENE and S.

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
http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html

Bagana Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0505-02=

BULUSAN Luzon, Philippines 12.770°N, 124.05°E; summit elev. 1,565 m

According to a news report, a plume of gas and „white ash“ was emitted from
Bulusan on 22 December.

Geologic Summary. Luzon’s southernmost volcano, Bulusan, was constructed within
the 11-km-diameter dacitic Irosin caldera, which was formed more than 36,000
years ago. A broad, flat moat is located below the prominent SW caldera rim;
the NE rim is buried by the andesitic Bulusan complex. Bulusan is flanked by
several other large intracaldera lava domes and cones, including the prominent
Mount Jormajan lava dome on the SW flank and Sharp Peak to the NE. The summit
of Bulusan volcano is unvegetated and contains a 300-m wide, 50-m-deep crater.
Three small craters are located on the SE flank. Many moderate explosive
eruptions have been recorded at Bulusan since the mid-19th century.

Source: News Balita http://news.balita.ph/html/article.php/20061222122137130

Bulusan Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0703-01=

DUKONO Halmahera, Indonesia 1.70°N, 127.87°E; summit elev. 1,185 m

The Darwin VAAC reported that a diffuse ash plume from Dukono was visible on
satellite imagery on 22 December drifting SE.

Geologic Summary. Reports from this remote volcano in northernmost Halmahera
are rare, but Dukono has been one of Indonesia’s most active volcanoes. More-or-
less continuous explosive eruptions, sometimes accompanied by lava flows,
occurred since 1933 until at least the mid-1990s, when routine observations
were curtailed. During a major eruption in 1550, a lava flow filled in the
strait between Halmahera and the N-flank cone of Gunung Mamuya. Dukono is a
complex volcano presenting a broad, low profile with multiple summit peaks and
overlapping craters. Malupang Wariang, 1 km SW of Dukono’s summit crater
complex, contains a 700 x 570 m crater that has also been active during
historical time.

Source: Darwin Volcanic Ash Advisory Centre
http://www.bom.gov.au/info/vaac/advisories.shtml

Dukono Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0608-01=

KARYMSKY Kamchatka Peninsula, Russia 54.05°N, 159.43°E; summit elev. 1,536 m

Seismic data from Karymsky were not available during 15-22 December. Based on
ground and pilot observations, ash plumes rose to 7 km (23,000 ft) a.s.l. and
drifted E and a thermal anomaly in the crater was detected on satellite imagery
during the reporting period. The Level of Concern Color Code remained at Orange
.

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.

Source: Kamchatkan Volcanic Eruption Response Team
http://www.kscnet.ru/ivs/kvert/updates.shtml

Karymsky Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1000-13=

KILAUEA Hawaii, USA 19.43°N, 155.29°W; summit elev. 1,222 m

During 20-26 December, lava from Kilauea continued to flow off of a lava delta
into the ocean at the East Lae’apuki and East Ka’ili’ili entries. Incandescence
on the pali was visible during the reporting period. Intermittent incandescence
was seen coming from the East Pond and January vents, South Wall complex, and
Drainhole vent in Pu’u ‘O’o’s crater.

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 by 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 broad areas on the S flank of Kilauea and
adding new land beyond the former coastline.

Source: US Geological Survey Hawaiian Volcano Observatory
http://volcano.wr.usgs.gov/hvostatus.php

Kilauea information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1302-01-

LANGILA New Britain Island, Papua New Guinea 5.53°S, 148.42°E; summit elev.
1,330 m

The Darwin VAAC reported that diffuse ash-and-steam plumes from Langila were
visible on satellite imagery on 22 December drifting WNW.

Geologic Summary. Langila, one of the most active volcanoes of New Britain,
consists of a group of four small overlapping composite cones on the lower
eastern flank of the extinct Talawe volcano. Talawe is the highest volcano in
the Cape Gloucester area of NW New Britain. A rectangular, 2.5-km-long crater
is breached widely to the SE; Langila volcano was constructed NE of the
breached crater of Talawe. An extensive lava field reaches the coast on the N
and NE sides of Langila. Frequent mild-to-moderate explosive eruptions,
sometimes accompanied by lava flows, have been recorded since the 19th century
from three active craters at the summit of Langila. The youngest and smallest
crater (no. 3 crater) was formed in 1960 and has a diameter of 150 m.

Source: Darwin Volcanic Ash Advisory Centre
http://www.bom.gov.au/info/vaac/advisories.shtml

Langila Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-01=

POPOCATÉPETL México 19.02°N, 98.62°W; summit elev. 5,426 m

Based on information from the Mexico City MWO, pilot reports, and satellite
imagery, the Washington VAAC reported that an eruption plume from Popocatépetl
rose to an altitude of 7.9 km (26,000 ft) a.s.l. and drifted E on 20 December.
A hotspot was also visible on satellite imagery.

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

Popocatépetl Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1401-09=

SANGAY Ecuador 2.03°S, 78.34°W; summit elev. 5,188 m

Based on a pilot report, the Washington VAAC reported that an ash plume from
Sangay rose to an altitude of 7.6 km (25,000 ft) a.s.l. on 23 December.

Geologic Summary. The isolated Sangay volcano, located E of the Andean crest,
is the southernmost of Ecuador’s volcanoes, and its most active. It has been in
frequent eruption for the past several centuries. The steep-sided, 5,230-m-high
glacier-covered volcano grew within horseshoe-shaped calderas of two previous
edifices, which were destroyed by collapse to the E, producing large debris
avalanches that reached the Amazonian lowlands. The modern edifice dates back
to at least 14,000 years ago. Sangay towers above the tropical jungle on the E
side; on the other sides flat plains of ash from the volcano have been sculpted
by heavy rains into steep-walled canyons up to 600 m deep. The earliest report
of an historical eruption was in 1628. More or less continuous eruptions were
reported from 1728 until 1916, and again from 1934 to the present. The more or
less constant eruptive activity has caused frequent changes to the morphology
of the summit crater complex.

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

Sangay Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-09=

SEMERU Java, Indonesia 8.11°S, 112.92°E; summit elev. 3,676 m

The Darwin VAAC reported that a plume from Semeru was visible on satellite
imagery on 21 December at an altitude of 4.3 (14,000 ft) a.s.l.

Geologic Summary. Semeru is the highest volcano on Java and one of its most
active. The symmetrical stratovolcano rises abruptly to 3,676 m above coastal
plains to the S and lies at the southern end of a volcanic massif extending N
to the Tengger caldera. Semeru has been in almost continuous eruption since
1967. Frequent small-to-moderate Vulcanian eruptions have accompanied
intermittent lava dome extrusion, and periodic pyroclastic flows and lahars
have damaged villages below the volcano. A major secondary lahar on 14 May 1981
caused more than 250 deaths and damaged 16 villages.

Source: Darwin Volcanic Ash Advisory Centre
http://www.bom.gov.au/info/vaac/advisories.shtml

Semeru Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0603-30=

ST. HELENS Washington, USA 46.20°N, 122.18°W; summit elev. 2,549 m

Data from deformation-monitoring instruments showed that during 20-26 December
the lava dome at Mount St. Helens continued to grow. Seismicity continued at
low levels, punctuated by earthquakes of M 1.5-2.5 and occasionally larger
sizes.

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: US Geological Survey Cascades Volcano Observatory
http://vulcan.wr.usgs.gov/Volcanoes/MSH/CurrentActivity/framework.html

St. Helens Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1201-05-

SUWANOSE-JIMA Ryukyu Islands, Japan 29.53°N, 129.72°E; summit elev. 799 m

Based on information from JMA, the Tokyo VAAC reported that an eruption from
Suwanose-jima occurred on 19 December.

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 E 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 around 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.

Source: Tokyo Volcanic Ash Advisory Center
http://www.ssd.noaa.gov/VAAC/OTH/JP/messages.html

Suwanose-jima Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0802-03=

TUNGURAHUA Ecuador 1.47°S, 78.44°W; summit elev. 5,023 m

On 21 December, IG reported that lahars from Tungurahua traveled NW down the
Mandur gorge resulting in a road closing and W down the Bilbao gorge. Gas-and-
steam emissions produced small plumes on 22, 23, and 25 December.

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 been
restricted to 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 Poltécnica Nacional http://www.igepn.edu.ec/

Tungurahua Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=1502-08=

ULAWUN New Britain Island, Papua New Guinea 5.04°S, 151.34°E; summit elev.
2,334 m

The Darwin VAAC reported that ash plumes from Ulawun were visible on satellite
imagery on 21, 22, and 25 December drifting ENE, NW, and SW, respectively.

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
http://www.ssd.noaa.gov/VAAC/OTH/AU/messages.html

Ulawun Information from the Global Volcanism Program
http://www.volcano.si.edu/world/volcano.cfm?vnum=0502-12=

http://www.volcano.si.edu/