Five days ago, when the ground around Mount Redoubt began to rumble, federal and state geologists in Anchorage quickly looked at the Cook Inlet volcano's past to venture a prediction about its future.
The past was clear. There wasn't a minute to lose.
Twenty years earlier, when Redoubt last erupted on Dec. 14, 1989, its labor pains were fast and furious, recalls John Power, a veteran geophysicist at the Alaska Volcano Observatory in Anchorage.
One day prior to that eruption, the five seismographs positioned around Redoubt's flanks were quiet -- then, in a matter of minutes, the alarms were screaming. And not a moment too soon. Redoubt quickly erupted.
"It went basically from what we would describe as 'background activity' to full eruption over a 23-hour period ... which is very rapid for a volcano," Power said.
Since that is the only detailed account of a Redoubt eruption in the scientific record, observatory geologists on the night shift last Sunday reacted swiftly when -- at 1 a.m. -- the volcano's seismographs suddenly began to red-line.
After a quick conference, AVO geologists upgraded the aviation color code for Redoubt from yellow to orange and sent out an all-points advisory noting that an eruption was possibly imminent, "perhaps within hours to days."
Since then, earthquakes and seismic readings at Redoubt have waxed and waned but generally remained at a level not seen since 1989, Power said Thursday.
"This particular sequence seems to be playing out a little bit slower. It hasn't resulted in an eruption yet, but we are still seeing these very elevated levels of earthquake activity. ... We still feel the most likely outcome is going to be an eruption."
This is a developing story. Check back later tonight, or see tomorrow's paper for further details.
By GEORGE BRYSON
gbryson@adn.com