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AVO VOLCANO ACTIVITY NOTIFICATION

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, July 25, 2008, 1:18 PM AKDT (Friday, July 25, 2008, 21:18 UTC)


OKMOK VOLCANO (VNUM #311290)
53°23'49" N 168°9'58" W, Summit Elevation 3520 ft (1073 m)
Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

The eruption of Okmok Volcano continued throughout this week with persistent ash emissions rising from 15,000 to 25,000 feet. From July 19 to July 20 the color code was increased to red in response to a more vigorous eruptive episode which produced ash to 30,000 feet. Photographs and an overflight by Alaska Volcano Observatory staff on July 20 and 21 confirmed the existence of multiple vigorous vents on the caldera floor.

Seismicity was characterized by intermittent bursts of volcanic tremor early in the week. This changed to continuous mid-level volcanic tremor on July 23, which persists to the current time. Amplitude of tremor has been generally constant since July 21.

Although there has been little change in the eruption in the past several days, stronger explosive activity could resume at any time with little or no warning.


Okmok volcano is a 6-mile-wide caldera that occupies most of the eastern end of Umnak Island, located 75 miles southwest of Dutch Harbor in the eastern Aleutian Islands. Okmok has had several eruptions in historic time typically consisting of ash emissions occasionally to over 30,000 feet ASL but generally much lower; lava flows crossed the caldera floor in 1945, 1958, and 1986. The last eruption occurred in February 1997 and was characterized by lava flows and intermittent ash emissions.

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

The nearest settlements are Nikolski, population about 35, roughly 45 miles west of the volcano, and a small number of people at the abandoned Fort Glenn military base 10 miles east of the volcano.

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

Based on reports from fishing boats Cleveland Volcano began erupting at approximately 12:00 AKDT (20:00 UTC) on July 21, 2008. This eruptive episode is more intense than that observed over the past several years. Pilot reports and satellite data have documented a persistent low level ash emission from 10,000 to 20,000 feet throughout the week when the volcano was visible through clouds. A large thermal anomaly suggests the presence of an ongoing active lava flow.


Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about 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 had 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. This eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emissions were observed in October 2006.

Please see http://www.avo.alaska.edu/activity/Cleveland.php for more information.

OTHER ALASKA VOLCANOES

Seismic activity is monitored in real time at 30 volcanoes in Alaska. Satellite images of all Alaskan volcanoes are analyzed daily for evidence of ash plumes and elevated surface temperatures. Some volcanoes may currently display anomalous behavior but are not considered to be at a dangerous level of unrest. Augustine, Iliamna, Redoubt, Wrangell, Gareloi, Great Sitkin, Makushin, Fisher, Shishaldin, Isanotski, Pavlof, Veniaminof, Ugashik-Peulik, Griggs, Snowy, Fourpeaked, Aniakchak, Tanaga, Kanaga, Akutan, Westdahl, Dutton, Ukinrek Maars, Martin, Mageik, Trident, Katmai, Novarupta, Spurr, and Korovin volcanoes are in color code GREEN and volcano alert level Normal. All are at or near normal levels of background seismicity. AVO did not detect ash plumes or significant elevated surface temperatures in the vicinity of any volcano.

Please see http://www.avo.alaska.edu/color_codes.php for complete definitions of Aviation color codes and Volcano alert levels.

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, Acting Scientist-in-Charge, USGS
jpower@usgs.gov, (907)786-7497

Steve McNutt, Coordinating Scientist, UAFGI
steve@giseis.alaska.edu (907)978-5458

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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URL: www.avo.alaska.edu/activity/report.php
Page modified: December 2, 2016 10:12
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