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ARCHIVED REPORT
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ALASKA VOLCANO OBSERVATORY

Information Release

Thursday, September 7, 2006 10:00 AM AKDT (1800 UTC)




CLEVELAND VOLCANO (CAVW#1101-24-)

52°49'24" N169°56'35" W, Summit Elevation 5676 ft (1730 m)

Current Level of Concern Color Code: YELLOW

Previous Level of Concern Color Code: unassigned



A short-lived explosive eruption of Cleveland Volcano in the Central Aleutians occurred about 7:55 pm local time on August 24. This eruption was first reported by mariners on the evening of August 24; although unable to confirm this eruption using satellite data, the National Weather Service issued a one-time SIGMET to alert the aviation community.



On Monday, AVO received video footage of this eruption showing an ash cloud reaching about 10,000 feet ASL and ash fall occurring from the cloud. Additional video footage shows the volcano to be remarkably quiet within an hour of the explosion, with only minor steaming from the summit vent.



Cleveland Volcano has produced brief, explosive eruptions sending ash clouds to elevations of 10,000 20,000 ft ASL on at least five occasions since February 2006. Satellite images since the explosion on August 24 show a faint thermal anomaly at the summit, suggesting that unrest at the volcano continues, and further ash explosions are possible without warning. As a result, AVO is elevating the level of concern color code at Cleveland Volcano from unassigned to YELLOW. The current level of activity poses a hazard primarily to low-flying aircraft and to people on or within a few kilometers of the island.



Short-lived, low-level ash eruptions (<10,000 feet ASL), like that observed this past week, could continue intermittently for months to years. Frequent cloudy conditions and the small size of these ash clouds make them difficult to detect using satellite images. Larger events (>20,000 feet ASL), such as those in March and May, could also occur but are more likely to be detected by satellite. Cleveland volcano lacks a real-time seismic network and therefore we are unable to monitor seismic changes that reflect eruptive activity.



Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about 75 km (45 mi) west of the community of Nikolski, and 1500 km (940 mi) southwest of Anchorage. The volcano's most recent significant eruption began in February 2001 and included 3 explosive events and ash clouds as high as 12 km (39,000 ft) above sea level. This eruption also produced a rubbly lava flow and hot avalanches that reached the sea. Prior to the August eruption, the most recent ash explosions were observed in May 2006.



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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