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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

INFORMATION RELEASE

Tuesday, August 3, 2004 2:00 PM ADT (2200 UTC)



MOUNT SPURR VOLCANO (CAVW#1103-04)

61o18' N 152o15' W, Summit Elevation 11,070 ft (3,374 m)

Current Level of Concern Color Code: YELLOW



An overflight of Mount Spurr by AVO scientists yesterday afternoon revealed

a circular depression in the icecap just northeast of the summit. The

depression is approximately 50 meters (165 feet) in diameter and about 25

meters (82 feet) deep. The floor of the depression contains an icy pond,

with small areas of open water. No steam or volcanic emissions were

observed. Depressions of this sort may have existed on Spurr before, but

AVO is not aware of any in recent decades. The depression may have formed

by heat from the volcano melting the ice, or, the release of stored water,

which might account for the minor mudflows observed several weeks ago on

the upper flanks. If due to heat, it is not known if the flow of heat to

the surface has increased and is related to the recent increase in

earthquake activity.



There is no evidence or suggestion of any explosive activity; no fresh ash

was observed anywhere on the mountain. Crater Peak, the vent responsible

for the eruptions in1953 and in the early 1990s, showed no signof any

unusual activity.



Earthquake activity continues beneath Mt. Spurr with no significant change

over the past week.



Based on these observations and our continuing seismic monitoring of the

volcano, there are no signs that an eruption is imminent or even certain.

Ephemeral summit craters have been described before at Mt. Spurr and

temporary increases in earthquake activity below a volcano often decline

without producing an eruption. AVO will continue to monitor activity at

Mount Spurr closely using seismic data, satellite images, and overflights,

and will issue further information releases as appropriate.



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 eruptons 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.



The volcano-hazard assessment for Mount Spurr Volcano is available from the

AVO web site: http://www.avo.alaska.edu/avo4/products/hazard.htm





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



Scott Stihler, Acting Coordinating Scientist, UAF-GI

scott@giseis.alaska.edu; (907)474-5450



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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