Redoubt volcano quiets after 2 morning blasts
By RICHARD MAUER
rmauer@adn.com
Published: March 25th, 2009 07:06 AM
Last Modified: March 25th, 2009 02:17 PM
After two small explosions today, Redoubt volcano simmered down to a quieter phase in its eruption cycle, leading scientists with the Alaska Volcano Observatory to lower the alert level from "warning" to "watch" and the color code from red to orange.
"The seismic activity has really declined," said Chris Waythomas, a hydrologist pulling watch duty this afternoon. "Things are very quiet."
The observatory relaxed the alert level at 1:35 p.m.
Waythomas said the volcano may be building a lava dome. At this stage in its cycle, the domes can be expected to collapse, producing ash in the process. Before that happens, seismic activity would likely increase, leading to a higher alert advisory, Waythomas said.
The earlier explosions did not produce significant amounts of ash, the observatory reported earlier.
The most recent event, at 10:17 a.m., was the eighth explosion since Redoubt began erupting Sunday evening, and followed an earlier, similar explosion at 5:12 a.m. today.
The height of the ash cloud from the early-morning blast was estimated to be about 15,000 feet, but it appeared to have dissipated over the volcano, the National Weather Service reported.
"It was such a minor eruption, we almost didn't see it on the radar," Weather Service meteorologist Christian Cassell said.
The 5:12 a.m. event lasted about 10 minutes.
"This is in a different class compared to the other six -- it's quite a bit smaller," Alaska Volcano Observatory geophysicist Peter Cervelli said.
Seismometers positioned around the volcano began sending a stronger signal about 10 minutes before the eruption, he said.
Darkness and bad weather precluded visual observation of the explosion through the AVO webcam, but radar detected the ash cloud, Cervelli said.
"Our best guess is we're extruding a lava dome and we may have had a piece of that dome break off and tumble along and produce an ash cloud," he said.
The plume was visible on the radar for only five minutes and didn't drift away from the volcano, Cassell said.