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ALASKA VOLCANO OBSERVATORY
Friday, May 7, 2004 10:30 AM ADT (18:30 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 small,
intermittent ash emissions, low-level volcanic tremor, and small volcanic
earthquakes. During this past week, small ash emissions were observed
during periods of clear weather on May 1-3. Ash clouds rose from 1,000 to
2,000 feet above the active cone (~8,000 to 9,000 feet or ~2,400 to 2,800 m
above sea level). The internet camera system in Perryville was brought down
for repair on May 4, so no systematic visual observations of ash plumes
were made after that time, though residents reported continued activity on
May 5. However, the observed seismicity is similar to that recorded last
week, suggesting that the ash burst activity continues. Satellite imagery
shows ash deposits on the snow to distances of 5 miles (~8 km) from the
vent. A pilot reported ash as far as 20 miles (33 km) from the cone. There
are no indications that more vigorous activity is imminent or even likely.
We expect that steam and ash emissions similar to those observed this week
may continue intermittently and could pose a hazard to people and
low-flying aircraft in the vicinity of the active cone.
AVO will continue to monitor activity at Mount Veniaminof using seismic
data, satellite images, and observer reports. AVO has increased the
frequency of seismic data analysis to provide early warning of increased
activity, should it occur. Public access to archived internet camera images
(collected at Perryville) can be found at www.avo.alaska.edu.
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 clouds very
similar to those observed this past week occurred in 2002. 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 sequences
of volcanic earthquakes and seismic tremor. The number of airwaves
recorded by the seismic network has diminished, but the more sensitive
pressure sensor continues to record weak signals from the volcano. Thermal
anomalies at the summit have been observed in satellite imagery under
optimal viewing conditions. Retrospective analysis confirms that these
data, as well as similar signals observed in January 2004, are the first
thermal anomalies observed at Shishaldin since August 2000. We see nothing
at this time to indicate that an eruption is imminent. However, activity
at Shishaldin could increase rapidly and AVO has increased the frequency of
seismic data analysis. AVO will continue to monitor activity using seismic
data, satellite images, and observer reports.
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,
Shishaldin, 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
firstname.lastname@example.org (907) 786-7497
John Eichelberger, Coordinating Scientist, UAF-GI
email@example.com (907) 474-5530
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.