ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, October 21, 2011, 11:09 AM AKDT (Friday, October 21, 2011, 19:09 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
Weather conditions have been cloudy at Cleveland volcano since Tuesday of this week preventing satellite observations of the summit. Elevated surface temperatures consistent with a lava dome within the summit crater were detected in satellite images early in the week. AVO has received no other reports of activity.
The edge of the dome is near the level of the crater rim on the southwest and east-northeast sides. Continued growth of the lava dome may result in lava flowing over the crater rim to produce a lava flow, and/or collapse of a flow front or dome flank to produce pyroclastic flows. Although lava could continue to erupt without generating an explosion, the growth of a lava dome in the summit crater increases the possibility of an explosive event. Explosions from the summit vent may produce ash clouds exceeding 20,000 ft above sea level with little to no warning, and could go undetected in satellite imagery for hours. However, lightning associated with significant ash-producing events may be detected sooner using an automated alarm system.
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 rapid 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.
OTHER ALASKA VOLCANOES
Seismic activity is monitored in real time at 30 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. Akutan, Aniakchak, Augustine, Dutton, Fisher, Fourpeaked, Gareloi, Great Sitkin, Griggs, Iliamna, Isanotski, Kanaga, Katmai, Mageik, Makushin, Martin, Novarupta, Okmok, Pavlof, Redoubt, Shishaldin, Snowy, Spurr, Tanaga, Trident, Ugashik-Peulik, Ukinrek Maars, Veniaminof, Westdahl, and Wrangell volcanoes are in color code GREEN
and volcano alert level Normal. 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 of these volcanoes.
Please see http://www.avo.alaska.edu/color_codes.php
for complete definitions of Aviation color codes and Volcano alert levels.
VOLCANO INFORMATION ON THE INTERNET: http://www.avo.alaska.edu
RECORDING ON THE STATUS OF ALASKA'S VOLCANOES (907) 786-7478
John Power, Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Jessica Larsen, Acting Coordinating Scientist, UAF
email@example.com (907) 474-7992
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.