ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, November 18, 2011, 11:35 AM AKST (Friday, November 18, 2011, 20:35 UTC)

CLEVELAND VOLCANO (VNUM #311240)
52°49'20" N 169°56'42" W, Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

The lava dome in Cleveland's summit crater has stopped growing, or is growing very slowly, according to satellite images. Elevated surface temperatures have been observed in satellite images during periods of clear weather over the past week. There is no evidence of ash emissions or any other eruptive activity.

The lava dome that began growing in late July 2011 now fills most of the roughly 200-m-wide summit crater. The surface of the dome reached to about 10 m below the top of the crater rim but did not overtop it. Since July, AVO has observed slow, steady growth of the lava dome and a thermal signature consistent with hot rock at the surface. We did not observe any deposits or features indicative of explosive activity or ash emission, nor did we receive any reports of explosive activity, ash, or gas emission. The period of unrest from late July to present can be characterized as an effusive lava eruption; at present, the volume of the lava dome is about one million cubic meters.

We are uncertain if the lava eruption has stopped or paused, and it is possible for effusion of lava to resume at any time. If it does, this could lead to the formation of lava flows that overtop the crater rim and flow down the flanks of the volcano. Such lava flows could collapse and produce avalanches of hot debris that reach the sea and may be accompanied by small ash clouds.

It remains possible for sudden explosions and ash emission to occur, and ash clouds exceeding 20,000 feet above sea level may develop. Such explosions and their associated ash clouds may go undetected in satellite imagery for hours. However, in cooperation with the University of Washington, AVO has implemented a lightning alarm system that may detect significant ash-producing events within minutes of onset. If a large explosive event occurs, seismic signals may be recorded on AVO seismic networks at nearby volcanoes; however, there is no real-time seismic monitoring network on Mt. Cleveland.

Additional information on Cleveland Volcano and the current activity may be found at this link:
http://www.avo.alaska.edu/activity/Cleveland.php

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

CONTACT INFORMATION:

John Power, Scientist-in-Charge, USGS
jpower@usgs.gov (907) 786-7497

Steve McNutt, Coordinating Scientist, UAF
steve@giseis.alaska.edu (907) 474-7131

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.

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