Alaska volcano back on eruption watch

Seismic activity at Alaska's Mount Redoubt again has scientists watching for an eruption.
Researchers have raised the alert status at Mount Redoubt, a volcano in southern Alaska, after another increase in seismic activity.

“Shallow earthquake activity under the volcano has been as high as 26 events per 10-minute period,” officials at the Alaska Volcano Observatory said Sunday in a statement announcing that the alert level was raised to “watch” status. Although no eruption has occurred, the scientists said the increase in seismic activity “likely represents either the upward movement of magma or pressurization of the system.” “It is possible for unrest at the volcano to change rapidly, and seismic activity or other signs of unrest could escalate culminating in an eruption within days to weeks,” the statement concluded. An increase in seismic activity at the same volcano prompted a “watch” level last Monday. In the U.S. Geological Survey’s color-coded alert levels, the orange “watch” level means the volcano “is exhibiting heightened or escalating unrest with increased potential of eruption” or that “eruption is underway with no or minor volcanic-ash emissions.” The next level is red, meaning an eruption is imminent or underway.

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Bill Burton, a geologist with the U.S. Geological Survey, said since January there have been increases in seismic activity at Mount Redoubt followed by periods of quiet.

The 10,197-foot peak is about 100 miles southwest of Anchorage, the most populous city in Alaska. Mount Redoubt last erupted nearly 20 years ago, in December 1989. That eruption lasted until April 1990.