ALASKA VOLCANO OBSERVATORY STATUS REPORT
U.S. Geological Survey
Sunday, February 19, 2012, 1:24 PM AKST (Sunday, February 19, 2012, 22:24 UTC)

KANAGA VOLCANO (VNUM #311110)
51°55'27" N 177°9'44" W, Summit Elevation 4288 ft (1307 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Somewhat elevated seismicity continues at Kanaga Volcano. Clouds have obscured the most recent satellite views. AVO has received no reports of further explosive activity or ash clouds.

Following apparent explosive activity and a resultant small ash cloud yesterday, February 18, AVO elevated the Aviation Color Code to YELLOW and the Volcano Alert Level to ADVISORY at 13:12 AST (22:12 UTC). Volcanic tremor had been detected on the local seismic network at Kanaga from 15:23-15:27 UTC (06:23 AKST) followed by numerous small events for about an hour. Short-lived explosive activity was suspected, and the unrest was corroborated by AVHRR satellite data from 15:35 UTC that showed a small--8 km in length--ash plume, detached and of unknown altitude, drifting 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.




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.





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

Satellite images indicate cloudy conditions at Cleveland during the past 24 hours. There have been no indications of explosive ash-producing activity from distant seismic, pressure or lightning sensors.

The new, 60-meter-diameter (200 feet) lava dome occupies only a small portion of the approximately 200 meter (650 foot) diameter summit crater. There have been no observations of ash emissions or explosive activity during this current lava eruption. The lava dome that formed throughout the fall-winter of 2011 was largely removed by the explosive activity on 25 and 29 December, 2011.

It remains possible for intermittent, sudden explosions of blocks and ash to occur at any time, 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. If a large, explosive, ash-producing event occurs, seismic, infrasound, or volcanic lightning may be detected by local and regional monitoring networks. There is no real-time seismic monitoring network on Mount Cleveland.

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.

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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