(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)
(2) Issued:(20120218/2211Z)
(3) Volcano:Kanaga (CAVW# 1101-11-)
(4) Current Color Code:YELLOW
(5) Previous Color Code:green
(6) Source:Alaska Volcano Observatory
(7) Notice Number:2012/A3
(8) Volcano Location:N 51 deg 55 min W 177 deg 9 min
(9) Area:Aleutians Alaska
(10) Summit Elevation:4288 ft (1307 m)
(11) Volcanic Activity Summary:Possible explosive activity and a likely ash cloud indicate new unrest at Kanaga Volcano. AVO is increasing the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY.

Volcanic tremor was detected from 15:23-15:27 UTC (6:23 AM AKST) followed by numerous small events for about an hour at Kanaga Volcano. A possible weak ash cloud was also detected in AVHRR satellite data from 15:35 UTC about 39 km (24 mi) NE of the volcano.

This new unrest indicates a possibility for sudden explosions of ash to occur at any time, and ash clouds exceeding 20,000 feet above sea level may develop. If a large, explosive, ash-producing event occurs, the local seismic network, satellite ash alarms, infrasound, and volcanic lightning will alert AVO to the new activity.

(12) Volcanic cloud height:Unknown
(13) Other volcanic cloud information:Unknown
(14) Remarks:Kanaga Volcano occupies the northern corner of Kanaga Island, one of the most southerly members of the central Aleutian chain. It is a symmetric composite cone 1307 m high and 4.8 km in diameter at sea level, built of interbedded basaltic and andesitic lava flows, scoria layers, and pyroclastic rocks. Kanaga Volcano last erupted 1994-1995 when observed eruptive plumes were relatively dilute, rising to altitudes of less than 3 km (9,840 ft) and dropping ash onto the flanks of the volcano. At least two significant ash plumes were recorded over the course of this eruption: the first, to ~7.5 km (24,600 ft) occurred on February 21, 1995 and the second on August 18,1995, when an eruption cloud reached ~4.5 km (14,760 ft). A light dusting of ash fell on the community of Adak and air traffic was disrupted due to continuing low-level activity and cloudy conditions which prevented visual approaches to the Adak air field.

(15) 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
(16) 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