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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

INFORMATION RELEASE

Tuesday, October 26 2004 9:30 AM ADT (1730 UTC)



MOUNT VENIAMINOF VOLCANO (CAVW #1102-07)

5610'N 15923'W, Summit Cone Elevation 7,073 ft (2,156 m)

Previous Level of Concern Color Code: YELLOW

Current Level of Concern Color Code: GREEN



AVO is lowering the Level of Concern Color Code for Mount Veniaminof

Volcano from Yellow to Green. Seismicity associated with ash emissions

seen this past summer has decreased to a level that no longer indicates

ash, ash-steam, or steam emissions are occurring on a regular basis. Since

early September, we have observed no ash emissions in web camera views of

the intracaldera cone nor have we seen evidence of ash emissions in

satellite data. AVO has received no recent reports of ash from either

pilots or ground observers. We consider the intermittent, low-level

seismic tremor that continues to be recorded at Veniaminof to be part of

the current background activity at the volcano. Steaming from the

intracaldera cone, possibly associated with very minor ash emissions, may

still occur. AVO continues to monitor Mount Veniaminof for significant

changes in activity.



Mount Veniaminof volcano is a young stratovolcano with an ice-filled 10-km

(6 mi) 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 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

characterized by intermittent, low-level emissions of steam and ash, and a

small lava flow onto the summit caldera ice field producing an ice pit.

Previous historical eruptions have produced ash plumes that reached 6,000 m

(20,000 ft) above sea level and associated ash fall within about 40 km (25

mi) of the volcano. Minor ash emissions were observed in late 2002 and

numerous ash emissions were observed in late spring and summer 2004, with

few rising more than 10,000 ft. above sea level.



SHISHALDIN VOLCANO (CAVW #1101-36)

5445'N 16358'W, Summit Cone Elevation 9,373 ft (2,857 m)

Previous Level of Concern Color Code: YELLOW

Current Level of Concern Color Code: GREEN



AVO is lowering the Level of Concern Color Code for Shishaldin Volcano from

Yellow to Green. Volcanic tremor at the volcano has remained at a

relatively constant and low level for more than a month. No new satellite

observations indicative of significant activity in the summit crater have

been received, and there have been no recent reports of ash emissions or

reports of ash on the snow near the summit. The low-level seismic tremor

that continues to be recorded at the volcano is considered to be

representative of the current background rate of activity at Shishaldin.

AVO continues to monitor the volcano for significant changes in activity.



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



Mount Spurr remains at color code YELLOW.



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, Redoubt, Iliamna, Augustine, Snowy, Griggs, Katmai, Novarupta,

Trident, Mageik, Martin, Aniakchak, Veniaminof, Pavlof, Dutton, Shishaldin,

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

occurring

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



CONTACT INFORMATION:



Tom Murray, Scientist-in-Charge, USGS

tlmurray@usgs.gov (907) 786-7497



John Eichelberger, Coordinating Scientist, UAF-GI

eich@giseis.alaska.edu (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.

VOLCANO ALERT LEVELS
NORMAL
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
ADVISORY
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
WATCH
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.
WARNING
Hazardous eruption is imminent, underway, or suspected.

AVIATION COLOR CODES
GREEN
Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
YELLOW
Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
ORANGE
Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].
RED
Eruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].

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Page modified: May 27, 2014 10:23
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