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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

WEEKLY UPDATE

Friday, July 30, 2004 11:00 AM ADT (1900 UTC)



ALASKA VOLCANOES



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

volcano. Approximately 10-20 earthquakes have been recorded daily beneath

the summit of Mount Spurr. This level of activity has remained at a

constant rate for the last several weeks. Although this represents a

notable increase over background seismicity levels, there are no

indications that an eruption is imminent. Often this type of seismicity

will decline without producing an eruption.

AVO will continue to monitor activity at Veniaminof using seismic data, satellite

images, internet camera data and observer reports.



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

side of Cook Inlet. The only historical eruptions in 1953 and 1992

occurred at the Crater Peak flank vent located 3.5 km (2 mi) south of the

Spurr summit. These eruptions were explosive, brief in duration, and

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

sea level and deposited several mm of ash on populated areas of

south-central Alaska, including approximately 6 mm of ash in Anchorage in

1953. The summit dome complex of Mount Spurr is largely covered in ice;

its last known eruption was approximately 5,000 years ago. Primary hazards

from future eruptions at Mount Spurr and Crater Peak include far-traveled

ash clouds, ash fall, pyroclastic flows, and lahars or mudflows that could

impact drainages primarily on the south and east sides of the volcano.



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



Episodes of volcanic tremor continue intermittently at Mount Veniaminof

Volcano. No visual observations of ash emissions have been made since July

22, although the observed seismicity is similar to that observed coincident

with ash emissions in the past few months. Most such emissions do not

reach 10,000 ft. above sea level, though a few have been reported to reach

as high as 12,000 ft. Satellite and web camera views of the volcano were

obscured by clouds throughout the week. Activity at Veniaminof could

become more vigorous without warning, and continuing steam and ash

emissions do pose a hazard to people and low-flying aircraft in the

vicinity of the caldera. AVO will continue to monitor activity at

Veniaminof using seismic data, satellite images, internet camera data and

observer reports.



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 similar to those occuring at

present were also detected in late 2002.



SHISHALDIN VOLCANO (CAVW #1101-36)

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

Current Level of Concern Color Code: YELLOW



Low-level seismic tremor continues to be recorded at Shishaldin Volcano.

This level of activity is similar to that observed over the past several

months. On July 24 an AVO field crew observed vigorous steaming at the

summit and what may be ash deposits on the upper slopes. During clear

satellite views of the volcano this week, no unusual activity was noted.

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

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, 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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