ALASKA VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Friday, October 31, 2008, 1:42 PM AKDT (Friday, October 31, 2008, 21:42 UTC)
53°23'49" N 168°9'58" W,
Summit Elevation 3520 ft (1073 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
During the past week, the level of seismic activity at Okmok Volcano has been low with only brief bursts of volcanic tremor recorded on the AVO network. Satellite views of the volcano have been mostly obscured by clouds. Clear images have shown nothing unusual other than a weak thermal anomaly in the vicinity of the intracaldera lake. On October 23, an Alaska Airlines pilot photographed the volcano with a light dusting of snow and no signs of surface activity.
Although the level of seismicity is low, it is possible, but growing increasingly unlikely, that vigorous ash emissions will resume.
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 1997.
The nearest settlement is Nikolski, population about 35, roughly 45 miles west of the volcano. A ranch caretaker family lives at Fort Glenn on the flank of the volcano about 6 miles east of the caldera rim.
52°10'9" N 175°30'41" W,
Summit Elevation 1030 ft (314 m)
Current Volcano Alert Level: UNASSIGNED
Current Aviation Color Code: UNASSIGNED
Yesterday, AVO reduced the Aviation Color Code to UNASSIGNED and Volcanic Alert Level to UNASSIGNED following two months of declining regional seismicity and no sign of continuing volcanic unrest.
Kasatochi Island is the summit of a predominantly submarine volcano composed of basaltic and andesitic lava flows and pyroclastic deposits. The volcanic cone has a circular central crater more than 1 km (3300 ft) across. Prior to the 2008 eruption, the high point of the crater rim was about 314 m (1030 ft) above sea level.
Historical eruptions at Kasatochi are poorly documented, although it is possible that eruptions attributed to nearby Konuiji volcano in 1760, 1827, and 1828 were actually eruptions of Kasatochi. Eruptive activity in 1899 may have destroyed the 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.
OTHER ALASKA VOLCANOES
Seismic activity is monitored in real time at 31 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
Tom Murray, Scientist-in-Charge, USGS
firstname.lastname@example.org (907) 786-7497
Steve McNutt, Coordinating Scientist, UAF
email@example.com (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.