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ALASKA VOLCANO OBSERVATORY
Friday, June 4, 2004 1:40 PM ADT (2140 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
Bursts of volcanic tremor continue at Mount Veniaminof. The only
significant ash emissions observed this past week occurred the evening of
May 30 into the morning of May 31. These were observed using the web
camera in Perryville (
appear to have exceeded 10,000 ft. (3000 m) above sea level. Clear views
of the volcano by the web camera earlier on May 30 showed steaming from
near the base of the intracaldera cone that rarely rose above the top of
the cone (7073 ft. or 2156 m above sea level). No activity was observed in
satellite data as the volcano was largely obscured by clouds. 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, internet camera data and
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 emissions
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. It is characterized by
weak seismic tremor and occasional discrete low-frequency earthquakes.
Small explosion signals have been recorded by the pressure sensor. Though
clouds largely obscured Shishaldin in satellite data, data acquired at 0823
UTC (0023 ADT) May 29 show the crater to continue to be warmer than
background. 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 summit. AVO will continue to
monitor activity at Shishaldin Volcano 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
The following two volcanoes, Mount Gareloi and Tanaga Volcano, have been
added to our list of seismically-monitored volcanoes. Seismic networks were
installed on the volcanoes in the summer of 2003 and performed well through
this past winter.
MOUNT GARELOI VOLCANO (CAVW #1101-07)
51°47'N 178°48'W, Summit Cone Elevation 5,924 ft (1,573 m)
Current Level of Concern Color Code: GREEN
Mount Gareloi, which makes up most of Gareloi Island, is a
stratovolcano 10 km by 8 km in diameter at its base with two summits,
separated by a narrow saddle. It is located in the Aleutians approximately
160 km west of Adak, AK. Volcanic activity has been frequently reported
from Mount Gareloi since its discovery during the Bering Expedition in
1760. "Smoke" or unspecified activity was noted in 1760, 1828, 1873, and
1927; lava extrusion in 1792; minor explosive eruptions in 1790 and 1791;
and major explosive eruptions in 1922 and 1929-30. The 1929 event is the
most violent on record for Gareloi volcano. Activity was reported several
times in the 1980's, including a report in 1987 of vigorous steaming of the
crater and a narrow flow-like feature that was also steaming extending down
from the north crater rim. A compound lava flow down the south flank also
occurred in the 1980s.
In April of 1929, a phreatic eruption opened an elongate crater 1600
m in maximum diameter just below the southern summit; further explosions
produced 12 smaller craters aligned along a south- to southeast-trending
fissure. Ash layers up to 2 m thick on Ogliuga Island, located about 16 km
southeast, may be attributable at least in part to this eruption and
several centimeters of pyroclastic debris are known to have fallen on Atka
Island (about 300 km eastward) during the event.
The local seismicity at Mount Gareloi consists mainly of
low-frequency or long-period earthquakes typically occurring about 1 every
2 minutes. Approximately 4 events per day are large enough to be located.
The character of this seismicity is indicative of active magmatic or
TANAGA VOLCANO (CAVW #1101-08)
51°53'N 178°08'W, Summit Cone Elevation 5,197 ft (1,806 m)
Current Level of Concern Color Code: GREEN
Tanaga Volcano is the central and highest of three adjacent
stratovolcanoes at the northwest end of Tanaga Island. It is located in the
Aleutians approximately 110 km west of Adak, AK. Tanaga Volcano and the
neighboring cones roughly define an east-west trend across northern Tanaga
Island. At least four cones adjacent to Tanaga Volcano apparently have been
active in the last few thousand years. A blanket of fine ash, as much as 6
m thick covers large areas of Tanaga Island. The ash, stratified and
intercalated with thin soil layers, may have accumulated over a period of
several thousand years.
Few details are available concerning historical activity of Tanaga
Volcano, and some or all of the events attributed to it may have involved
adjacent cones in the northwest part of the island. Tanaga was reported
active throughout the period 1763-1770. Smoke was noted above the island in
1791 and 1829, and a lava flow was observed in 1914.
The local seismicity at Tanaga Volcano consists mainly of
high-frequency or volcano-tectonic earthquakes occurring about one per
week. No volcanic tremor has been observed.
OTHER ALASKA VOLCANOES
Seismic activity is monitored in real time at 27 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, Kanaga, Tanaga,
and Gareloi 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
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
Steve McNutt, Acting Coordinating Scientist, UAF-GI
email@example.com (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.