Volcanic activity at Mount Redoubt rose sharply Sunday with tremors and small discrete earthquakes recurring as often as twice a minute, the Alaska Volcano Observatory reported.
No eruption occurred, but around noon the clouds parted and AVO Web cams revealed a plume of steam and gas rising near the summit. It marked the second weekend in a row that Redoubt began rumbling anew.
Over one 10-minute span seismometers near the volcano's summit recorded 26 discrete earthquakes, which might reflect the upward movement of magma or gas "breaking rock," AVO geophysicist Rick Wessel said.
"It's definitely a different kind of signal that we haven't seen yet," and one that typically precedes an eruption, he said. "But it could still be days -- it's hard to put a timeline on it."
Redoubt's seismicity has waxed and waned ever since the volcano entered its current state of unrest on Jan. 25.
Located in Lake Clark National Park 100 miles southwest of Anchorage, Redoubt last erupted in the winter of 1989-1990.
Saturday night the observatory staff raised Redoubt's aviation warning level from yellow to orange and its advisory status to "watch," signifying that AVO geologists are again monitoring the volcano around the clock.
"The steam plume seems to have a little bit more puffing to it today," Wessel said Sunday afternoon. "It's got some pulses."
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By GEORGE BRYSON
gbryson@adn.com