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ALASKA VOLCANO OBSERVATORY
Friday, May 21, 2004 11:30 AM ADT (19:30 UTC)
MOUNT VENIAMINOF VOLCANO (CAVW #1102-07)
56°10'N 159°23'W, Summit Cone Elevation 7,073 ft (2,156 m)
Current Level of Concern Color Code: YELLOW
Unrest continues at Mount Veniaminof volcano, characterized by intermittent
volcanic tremor. These data are similar to the seismic signals recorded
last month in association with small ash plumes, suggesting that ash bursts
continue. A pilot report on May 18 indicated the presence of an ash plume
rising to heights of 1000-3000 ft (300-900 m) above the volcano's summit
(8000-10,000 ft or 2400-3000 m above sea level) and extending approximately
20 miles (32 km) northeast. Cloudy conditions have obscured observation of
Veniaminof by satellite. There are no indications that more vigorous
activity is imminent or even likely. However, activity at Veniaminof could
increase rapidly, and steam and ash emissions may pose a hazard to people
and low-flying aircraft in the vicinity of the caldera. AVO will continue
to monitor activity at Mount Veniaminof using seismic data, satellite
images, and observer reports.
Mount Veniaminof volcano is an andesitic stratovolcano with an ice-filled
10-km diameter summit caldera located on the Alaska Peninsula, 775 km (480
mi) southwest of Anchorage and 35 km (22 mi) north of Perryville.
Veniaminof is one of the largest (~ 300 km3) and most active volcanic
centers in the Aleutian Arc and has erupted at least 12 times in the past
200 years. The most recent significant eruption of the volcano occurred in
1993-95 and was a moderate Strombolian eruption from the main intracaldera
cone in the northwest sector of the caldera above Cone Glacier. The
eruption was characterized by intermittent low-level emissions of steam and
ash, and a small lava flow was extruded into the summit caldera ice field
producing an ice pit. Minor explosions producing small ash occurred in 2002
and in recent weeks. Previous historical eruptions have produced ash plumes
that reached 6,000 m (20,000 ft) above sea level and ash fallout that
blanketed areas within about 40 km (25 mi) of the volcano.
SHISHALDIN VOLCANO (CAVW #1101-36)
54°45'N 163°58'W, Summit Cone Elevation 9,373 ft (2,857 m)
Current Level of Concern Color Code: YELLOW
Seismic unrest continues at Shishaldin volcano, characterized by weak
seismic tremor and small explosions. On May 16 a pilot reported an ash
plume rising to 1000 ft (300 m) above Shishaldin's summit (10,400 ft or
3170 m above sea level). Satellite imagery from May 17 shows a vigorous
plume that may contain small amounts of ash emanating from the summit.
Clouds have obscured Shishaldin in satellite images taken since that time.
We see nothing at this time to indicate that more vigorous activity is
imminent. However, activity at Shishaldin could increase rapidly and ash
and gas emissions may pose a hazard to people and low-flying aircraft in
the vicinity of the active cone. AVO will continue to monitor activity at
Shishaldin volcano using seismic data, satellite images, and observer
Shishaldin volcano, located near the center of Unimak Island in the eastern
Aleutian Islands, is a spectacular symmetric cone with base diameter of
approximately 10 miles (16 km). A small summit crater typically emits a
noticeable steam plume with occasional small amounts of ash. Shishaldin is
one of the most active volcanoes in the Aleutian volcanic arc, erupting at
least 28 times since 1775. Most of Shishaldin's eruptions have consisted
of small ash and steam plumes, although the most recent eruption in
April-May 1999 produced an ash column that reached a height of 45,000 ft
above sea level.
OTHER ALASKA VOLCANOES
Seismic activity is monitored in real time at 25 volcanoes in Alaska.
Satellite images of all Alaskan volcanoes are analyzed daily for evidence
of ash plumes and elevated surface temperatures. Some volcanoes may
currently display anomalous behavior but are not considered to be at a
dangerous level of unrest.
Wrangell, Spurr, Redoubt, Iliamna, Augustine, Snowy, Griggs, Katmai,
Novarupta, Trident, Mageik, Martin, Aniakchak, Pavlof, Dutton, Isanotski,
Fisher, Westdahl, Akutan, Makushin, Okmok, Great Sitkin, and Kanaga
volcanoes are in color code GREEN. All are at or near normal levels of
background seismicity. AVO did not detect ash plumes or significant
elevated surface temperatures in the vicinity of any volcano.
ABBREVIATED COLOR CODE KEY (contact AVO for complete description):
GREEN volcano is dormant; normal seismicity and fumarolic activity
YELLOW volcano is restless; eruption may occur
ORANGE volcano is in eruption or eruption may occur at any time
RED significant eruption is occurring or explosive
eruption expected at any time
VOLCANO INFORMATION ON THE INTERNET: http://www.avo.alaska.edu
RECORDING ON THE STATUS OF ALASKA'S VOLCANOES (907) 786-7478
Tom Murray, Scientist-in-Charge, USGS
email@example.com (907) 786-7497
Steve McNutt, Acting Coordinating Scientist, UAF-GI
firstname.lastname@example.org (907) 474-7131
The Alaska Volcano Observatory is a cooperative program of the U.S.
Geological Survey, the University of Alaska Fairbanks Geophysical
Institute, and the Alaska Division of Geological and Geophysical Surveys.