Printer friendly versionALASKA VOLCANO OBSERVATORY
Thursday, September 7, 2006 10:00 AM AKDT (1800 UTC)
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
Tom Murray, Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
John Eichelberger, Coordinating Scientist, UAF-GI
email@example.com (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.