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ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, November 4, 2011, 12:42 PM AKDT (Friday, November 4, 2011, 20:42 UTC)
52°49'20" N 169°56'42" W,
Summit Elevation 5676 ft (1730 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
Cloud cover has obscured the summit of Cleveland Volcano for much of the past week and satellite observations have indicated no unusual behavior or signs of unrest except for a thermal signal briefly detected early Wednesday morning Nov. 2. Satellite data obtained over the past three weeks indicate that the lava dome in the summit crater has not significantly changed in size. Thus it appears that the eruption of lava in the summit crater may have paused or stopped. Based on these observations and no reports of explosive activity or ash emission, AVO lowered the Aviation Color Code and Volcano Alert Level to YELLOW/ADVISORY on Thursday, Nov. 3.
The lava dome that began growing in late July 2011 now fills most of the roughly 200 m diameter summit crater. The surface of the dome reached to about 10 m below the top of the crater rim but did not overtop the rim. 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 that resulted in a dome-shaped accumulation of lava in the summit crater of the volcano. 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 the eruption of lava in the summit crater does resume, 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:
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
Steve McNutt, Coordinating Scientist, UAF
email@example.com (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.