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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

WEEKLY UPDATE

Friday, February 25, 2005 12:15 PM AST (21:15 UTC)



MOUNT VENIAMINOF VOLCANO (CAVW #1102-07)

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

Current Level of Concern Color Code: YELLOW

Previous Level of Concern Color Code: ORANGE



Seismic activity at Veniaminof Volcano has decreased substantially this

week. Periods of volcanic tremor have diminished, and no discrete events

associated with ash bursts have occurred for several days. Mount Veniaminof

has been occasionally visible in web camera images throughout the week and

only minor emissions of steam have been observed. Satellite views of the

volcano have not been possible this week due to cloudy conditions. AVO has

received no reports of ash emissions from pilots or observers on the

ground. Given the decline of the seismicity it appears that the most recent

episode of Strombolian eruptive activity has ended. The Level of Concern

Color Code for Mount Veniaminof Volcano is thus being downgraded from

orange to YELLOW.



Because of its recent eruptive history, conditions at the volcano can

change quickly and another episode of Strombolian activity may begin with

little or no warning. Thus, explosions of ash and steam could resume and

may pose a hazard to people and low-flying aircraft in the vicinity of the

active cone.



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 ash-producing explosions occurred in 2002,

2004, 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.





MOUNT SPURR VOLCANO (CAVW#1103-04)

6118' N 15215' W, Summit Elevation 11,070 ft (3,374 m)

Current Level of Concern Color Code: YELLOW



Elevated levels of seismicity continue to be recorded at Mount Spurr. No

activity was observed in satellite and web camera images this week. AVO

received a pilot report of vigorous steaming from the vent of Crater Peak

on February 24, 2005, but we have observed no unusual change in the seismic

activity beneath Crater Peak or Mount Spurr. Conditions at Crater Peak and

Mount Spurr do not indicate that an eruption is imminent.



Mount Spurr volcano is an ice- and snow-covered stratovolcano located on

the west side of Cook Inlet. The only known historical eruptions occurred

in 1953 and 1992 from the Crater Peak flank vent located 3.5 km (2 mi)

south of the summit of Mount Spurr. These eruptions were brief, explosive,

and produced columns of ash that rose up to 20 km (65,000 ft) above sea

level and deposited several mm of ash in south-central Alaska, including

approximately 6 mm of ash on Anchorage in 1953. The last known eruption

from the summit of Mount Spurr was more than 5,000 years ago. Primary

hazards during future eruptions include far-traveled ash clouds, ash fall,

pyroclastic flows, and lahars or mudflows that could inundate drainages all

sides of the volcano, but primarily on the south and east flanks.







KOROVIN VOLCANO (ATKA VOLCANIC CENTER CAVW #1101-16)

52.381 N 174.154 W, Summit Cone Elevation 5,029 ft (1,533 m)

Current Level of Concern Color Code: YELLOW



On February 24, 2005, AVO received a report of ash and steam emissions from

Korovin Volcano on Atka Island, that occurred at approximately 7:00 PM

local time (8:00 PM AST) February 23, 2005. According to residents of Atka

village, the initial ash burst reached a height of approximately 8,000 feet

(2440m) above sea level and drifted eastward. Since then, we have received

no new reports of activity at Korovin Volcano. Cloud cover over Atka Island

has prohibited satellite views of the volcano.



It is possible that a minor eruptive episode of Korovin Volcano may be

developing or is in progress. Low-level steam and ash emissions may occur

intermittently and could pose a hazard to people and low- to medium-flying

aircraft in the vicinity of the volcano. If eruptive activity increases,

light ash fall could occur on parts of Atka Island, including the village

of Atka. Residents should take the necessary precautions for dealing with

an episode of ash fall. Information about dealing with an ash fall event is

contained on the following Internet site:

http://vulcan.wr.usgs.gov/Hazards/Safety/what_to_do_during_ashfall.html or

by contacting AVO.



Korovin Volcano presently is not being seismically monitored by a standard

AVO seismic network. However, a seismic station that is part of a regional

seismic network operated by the Alaska Earthquake Information Center is

located in Atka village and provides some monitoring capability.



Korovin Volcano is a 1553 m high stratovolcano on the northern part of Atka

Island in the central Aleutian Islands, about 184 km (110 mi) east of Adak,

538 km (350 mi) west of Dutch Harbor, and 1760 km (1100 mi) southwest of

Anchorage. The volcano has two distinct summit vents about 0.6 km apart,

that have been the sites of eruptive activity as recently as June 1998.

Korovin has erupted several times in the past 200 years, including 1907,

1951, 1953, 1954, 1973, 1976, 1986, 1987, 1996, and 1998. All of these

eruptions produced minor amounts of ash and occasional but small lava

flows. Reports of the height of the ash plume produced by the 1998 eruption

ranged from 4900 to 9200 m (16,000 to 30,000 feet) above sea level.



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, Redoubt, Iliamna, Augustine, Snowy,

Griggs, Katmai, Novarupta, Trident, Mageik, Martin, Aniakchak, Pavlof,

Dutton, Isanotski, Shishaldin, 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



Chris Nye, Acting Coordinating Scientist, UAF-GI

cnye@giseis.alaska.edu; (907) 474-7430



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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