Explosive Eruption at Okmok Volcano [Update #1]

Click link for: Okmok Eruption & Cleveland Volcano [Update #2]

A strong explosive eruption is underway at Okmok Volcano

AVO/USGS Volcanic Activity Notice

2008-07-14 16:26:51 – [2008-07-15 00:26:51UTC]

Information Statement
Summary

A strong explosive eruption is underway at Okmok Volcano on Umnak Island in the eastern Aleutians.The volcano is currently at aviation color code RED and alert level WARNING. All areas immediately around the volcano are considered hazardous. Airborne ash and gas continues to drift with the wind and pose a hazard to aviation in the area. Additional ash fall will occur on Umnak Island and possibly adjacent islands as long as the eruption continues.

Image of the eruption of Okmok, taken Sunday, July 13, 2008, by flight attendant Kelly Reeves during Alaska Airlines flights 160 and 161. Picture Date: July 13, 2008 Image Creator: Kelly Reeves – Image courtesy of Alaska Airlines.

Latest OKMOK VOLCANO Status Report

Alaska Volcano Observatory
Current Status Report
Monday, July 14, 2008 12:39 PM AKDT (20:39 UTC)

OKMOK VOLCANO (CAVW #1101-29-)
53°23’49” N 168°9’58” W, Summit Elevation 3520 ft (1073 m)
Current Aviation Color Code: RED
Current Volcano Alert Level: WARNING

The eruption at Okmok continues based on ongoing seismic activity. Satellite observations indicate ash emissions continue reaching altitudes of 30,000 – 35,000 ft asl. Satellite observations also indicate a thermal anomaly in the western portion of the caldera (in the vicinity of Cone D.). There is currently an NWS ash fall advisory in effect for the Eastern Aleutian zone, including Nikolski and Unalaska/Dutch Harbor.

Satellite data shows an ash plume extending towards the southeast at an estimated height of 30,000 – 35,000 ft (~9 – 11 km) above sea level.

Okmok Caldera as viewed from an Alaska Airlines jet in early June, 2007. Okmok caldera is a nearly circular, 500- to 800-m-deep, 8- to 10-km-diameter collapse crater that truncates an older volcanic edifice. The current caldera formed about 2000 years ago. Since then, numerous eruptions from vents on the floor of the caldera have produced a variety of cones, craters, lava flows, and other volcanic features. As of March, 2008, Okmok last erupted in 1997 and is one of the most active of volcanoes in the Aleutians. Picture Date: June 07, 2007 – Image Creator: Cyrus Read – Image courtesy of AVO/USGS.

Reports indicate no ash fall in Unalaska/Dutch Harbor since Saturday, July 12. There is currently an NWS ash fall advisory in effect for the Eastern Aleutian zone, including Nikolski and Unalaska/Dutch Harbor.
Ash fall is expected to continue downwind of the volcano including over marine areas in the North Pacific. Areas in the immediate vicinity of the volcano on Umnak Island should be avoided, particularly the Crater Creek drainage northeast of the caldera.

Ash clouds are drifting southeast of the volcano and poses a risk to aircraft in the vicinity. The current estimated ash cloud height for the ash is 30,000 – 35,000 ft asl (~9 – 11 km) above sea level.
Ballistics may impact the areas around the caldera rim.

Historical eruptions of Okmok have typically produced lava flows, however at this time we cannot confirm that a lava flow has been produced.

Okmok Volcano is located on the northeast end of Umnak Island in the eastern Aleutians about 65 miles southwest of Unalaska/Dutch Harbor. The volcano consists of a 6-mile-wide circular caldera or crater about 1600 feet deep that formed about 2000 years ago. Okmok has been frequently active in historical times producing ash clouds often accompanied by lava flows within the caldera. The most recent eruption occurred in 1997 and produced ash clouds and a lava flow that traveled about 5 miles across the caldera floor.

See http://www.avo.alaska.edu/activity/Okmok.php for more information.

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