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No increased earthquake activity has been measured, and the alert level for Redoubt remains at normal and the aviation code remains at green, according to an information statement released by AVO last Friday morning. Redoubt last erupted in the winter of 1989-90, depositing ash over much of the Kenai Peninsula. A Boeing 747 jet flew into an ash cloud on Dec. 18, 1989, causing all four engines to stop. The jet fell about 10,000 feet before the pilot restarted the engines.

In the recent overflight, scientists reported new fractures and circular openings in the upper Drift Glacier on the north side of Redoubt. Fumaroles on the 1968 and 1990 domes also were seen to be steaming more vigorously. A distinct hydrogen sulfide odor also was observed on the overflight, but instruments did not detect sulfur dioxide.

Seismic instruments on Redoubt have not shown increased small earthquakes above normal background levels. However, in a second report released late Friday, AVO noted weak but anomalous volcanic seismicity on Redoubt. Volcanic activity remains very low, but is slightly above background levels. Scientists also are restoring some seismic stations that hadn't been working fully.

In the months before the 1989-1990 eruption of Redoubt, increased activity in fumaroles and higher levels of gasses preceded the eruption but there also was a dramatic increase in earthquakes. AVO said if the current low-level unrest leads to an eruption, an increase in earthquake activity should be noticed. McNutt said that before the 1989 eruption, several thousand small earthquakes at Redoubt were reported in a day, as opposed to just a handful now. In evaluating a volcano's potential to erupt, scientists look at a variety of information, such as seismicity and gassing, and not any one set of data, McNutt said.

"In this business, you don't look at one data stream in isolation," he said.

For more information, visit the AVO Web site at www.avo.alaska.edu, or call (907) 786-7478 for a recorded update. Weekly updates are released every Friday.

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.

Michael Armstrong can be reached at michael.armstrong@homernews.com.