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AVO VOLCANO ACTIVITY NOTIFICATION

ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, October 17, 2008, 3:34 PM AKDT (Friday, October 17, 2008, 23:34 UTC)


KASATOCHI VOLCANO (VNUM #311130)
52°10'9" N 175°30'41" W, Summit Elevation 1030 ft (314 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

Seismicity at Kasatochi remains low. Clouds obscured views of the volcano by satellite most of the week. During partly clear viewing periods, a weak thermal anomaly was observed, likely from the warm crater lake and/or the slowly cooling, recently erupted volcanic deposits.

Kasatochi Volcano does not have a seismic network, thus AVO depends on networks on neighboring islands to monitor earthquake activity there. For this reason, low-level seismicity may not be detected and renewed volcanic activity is possible at any time with little or no warning.



Kasatochi Island represents the emergent summit of a predominantly submarine volcano composed of basaltic and andesitic lava flows and pyroclastic deposits. The island consists of a single cone with a central circular crater with a diameter of 1.4 km. The maximum height of the crater rim is about 314 m. The volcano's most recent eruption began on August 7, 2008. This eruption produced ash clouds as high as 50,000 ft above sea level and pyroclastic-flow and surge deposits that cover the entire island to a depth of many meters. Prior the 2008 eruption, Kasatochi had no confirmed historical activity, although it is possible that eruptions attributed to nearby Konuiji volcano in 1760, 1827, and 1828 were actually minor eruptions of Kasatochi. Eruptive activity in 1899 may have destroyed a lake within the Kasatochi crater. Kasatochi is 83 km (52 mi) east of the community of Adak, and 90 km (55 mi) west of the community of Atka.

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

Low-level seismicity at Okmok Volcano continues. During partly clear viewing periods, a weak thermal anomaly was observed, likely from the warm summit crater lakes and/or the slowly cooling, recently erupted volcanic deposits.


Although the level of seismicity is relatively low, it is possible for vigorous ash emissions to resume at any time.

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.

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



CONTACT INFORMATION:

Tom Murray, Scientist-in-Charge, USGS
tlmurray@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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