(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:(20110802/2343Z)
(3) Volcano:Cleveland (CAVW# 1101-24-)
(4) Current Color Code:ORANGE
(5) Previous Color Code:yellow
(6) Source:Alaska Volcano Observatory
(7) Notice Number:2011/A3
(8) Volcano Location:N 52 deg 49 min W 169 deg 56 min
(9) Area:Aleutians Alaska
(10) Summit Elevation:5676 ft (1730 m)
(11) Volcanic Activity Summary:Observations of Cleveland Volcano from Friday July 29, 2011 show a small lava dome about 40 meters (131 feet) in diameter in the summit crater. In response, AVO is raising the Aviation Color Code to Orange and the Alert Level to Watch.

The lava dome was extruded sometime after July 7 when the last clear view of the summit area was acquired. The formation of a lava dome is consistent with observed thermal anomalies seen since July 19, 2011 suggesting that the dome extruded since that time.

A weak thermal anomaly persists at the summit and may indicate that the lava dome continues to slowly grow or that dome growth has ceased and the dome is slowly cooling. If dome growth continues, lava flows onto the flanks of the volcano may develop but would not be hazardous to aviation. The presence of the lava dome increases the possibility of an explosive eruption, but does not necessarily indicate that one will occur. Short-lived explosions could produce an ash cloud that exceeds 20,000 ft above sea level. These events can occur without warning and may go undetected in satellite imagery for hours.

Without a real-time seismic network at Cleveland, AVO is unable to track local earthquake activity related to volcanic unrest, provide forecasts of potential eruptions, or confirmation of explosive activity. Low-level ash emissions and elevated surface temperatures such as those observed recently do not necessarily mean a larger eruption is imminent. AVO continues to monitor the volcano using satellite imagery.
(12) Volcanic cloud height:Unknown
(13) Other volcanic cloud information:Unknown
(14) Contacts:John Power, Scientist-in-Charge, USGS
jpower@usgs.gov (907) 786-7497

Steve McNutt, Coordinating Scientist, UAF
steve@giseis.alaska.edu (907) 474-7131
(15) Next Notice:A new VONA will be issued if conditions change significantly or alert levels are modified. While a VONA is in effect, regularly scheduled updates are posted at
http://www.avo.alaska.edu