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ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, September 23, 2011, 2:20 PM AKDT (Friday, September 23, 2011, 22:20 UTC)
52°49'20" N 169°56'42" W,
Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE
Mostly cloudy conditions prevented satellite views of Cleveland during most of the past week. Observations of elevated surface temperatures at the summit on September 18 and a 15 m (49 ft) change in the width of the dome observed on September 20 are indications that the eruption of Cleveland is continuing. As of September 20, the size of the dome was approximately 165 m (541 ft) in diameter compared to 150 m (492 ft) in diameter a week prior (September 9). As of that time, the lava dome was entirely contained within the summit crater, approximately 20 meters below the eastern rim. AVO has received no other reports of activity at this volcano.
A growing lava dome in the crater increases the possibility of an explosive event, but does not necessarily indicate that one will occur. It is possible that explosions from the summit crater vent could produce ash clouds that may exceed 20,000 ft above sea level. These events can occur without warning and may go undetected in satellite imagery for hours. However, lightning associated with significant ash-producing events many be detected within mintues using an automated alarm system. If lava dome growth continues, lava may overflow the crater rim to produce a lava flow and/or collapse to produce pyroclastic flows. Sudden collapse of the effusing lava could result in the generation of a volcanic ash cloud.
AVO does not have a real-time seismic network on the volcano and thus we are unable to track local earthquake activity related to volcanic unrest, provide forecasts of eruptive activity, or confirmation of explosive, ash-producing events. In the event of a large explosive eruption like that in 2001, it is possible that seismic signals may be recorded on AVO seismic networks at nearby volcanoes. AVO will continue to monitor the volcano using multiple sources of satellite lightning detection, and distant seismic data.
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 it produced 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. The 2001 eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emissions were observed in January and June 2009.
Chris Waythomas, Acting Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Scott Stihler, Acting Coordinating Scientist, UAF
email@example.com (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.