Sunday, Sep 14, 2008
It was reported that during 3-9 September seismic activity from Kasatochi was low. Vigorous steam-and-gas plumes rose above the crater and drifted up to 32 km downwind. On 4 September the Volcano Alert Level was lowered to Advisory and the Aviation Color Code to Yellow. Weak thermal anomalies were detected on 5 and 7 September. [more]
Thursday, Aug 21, 2008
It was reported that during 13-19 August seismic activity from Kasatochi was detected by stations on Great Sitkin, about 40 km W. On 17 August, the smell of sulfur was reported in the town of Adak. [more]
map showing location of Mount Okmok. Image source: Cameron, Cheryl, courtesy of the Alaska Volcano Observatory / Alaska Division of Geological & Geophysical Surveys
Kasatochi volcanoKasatochi is a remote island forming the peak of a mostly submerged stratovolcano rising to 314 m a.s.l. in the Aleutian island chain. It is one of the volcanoes in the world that formed new islands in historic times.
Background:From Miller and others (1998): "Kasatochi Island, like Gareloi, Bogoslof, and several other volcanoes in the western Aleutian arc, represents the emergent summit of a predominantly submarine volcano. The island consists of a single, undissected cone with a central lake-filled crater about 0.75 km in diameter. A maximum height of 314 m is on the southern crater rim; elevation of the lake is less than about 60 m. Kay (1990) reports a lava dome on the northwest side of the cone at an elevation of ~150 m.
"Coats (1956) referred to Kasatochi as one of a group of little-known volcanoes that appear to be stratovolcanoes composed of basaltic and andesitic flows and pyroclastics. The mean slope of the southern flank (about 18 degrees) is considerably less than the mean slope of the northern flank (about 45 degrees). This asymmetry of form may reflect a predominance of lava flows low on the southern flanks, or, it may be due to a higher rate of erosion by wave action from the north. Bathymetry indicated that Kasatochi is at the northern end of a 15-km-long, 6-km-wide submarine ridge that is normal to the trend of the Andreanof Islands. Water depths along the ridge are less than 90 m; if Kasatochi is constructed entirely on the ridge, the total height of the volcanic pile is only a little more than 400 m."
(from AVO's website, Kasatochi information)
- Miller, T. P., McGimsey, R. G., Richter, D. H., Riehle, J. R., Nye, C. J., Yount, M. E., and Dumoulin, J. A., 1998, Catalog of the historically active volcanoes of Alaska: U.S. Geological Survey Open-File Report OF 98-0582, 104 p.
- Coats, R. R., 1956, Reconnaissance geology of some western Aleutian Islands, Alaska: in Investigations of Alaskan volcanoes, U.S. Geological Survey Bulletin B 1028-E, p. 83-100, 1 sheet, scale unknown.