ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, December 23, 2011, 12:45 PM AKST (Friday, December 23, 2011, 21:45 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
During the past week, several clear satellite images of Cleveland showed no sign of significant volcanic unrest. Without ground-based instrumentation, it is difficult to determine if the volcano has returned to a state of quiet following intermittent lava eruption from late July through early October. Renewed lava production and related explosive, ash-producing activity could occur suddenly. Small explosions in the summit crater can also occur while the lava dome continues to cool.
For these reasons, AVO will continue to assign aviation color code YELLOW and alert level ADVISORY. We will, however, cease daily reporting on Cleveland until a significant change occurs or sufficient time has passed without activity to warrant a return to UNASSIGNED/NORMAL.
Whether eruptive activity at Cleveland has ceased or has merely paused is not certain. Effusion could resume and send lava over the crater rim and down the steep flanks of the volcano. Such lava flows might collapse and produce avalanches of hot debris that reach the sea and may be accompanied by small ash clouds.
Sudden explosions of blocks and ash could also 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. There is no real-time seismic monitoring network at Cleveland.
Additional information on Cleveland Volcano and the current activity may be found at this link:
Please see http://www.avo.alaska.edu/color_codes.php for complete definitions of Aviation color codes and Volcano alert levels.
John Power, Scientist-in-Charge, USGS
email@example.com (907) 786-7497
Chris Nye, Acting Coordinating Scientist
firstname.lastname@example.org (907) 474-7430
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.