by Andrew Hinkelman, Jill Burke, Sean Doogan and Casey Grove
Monday, March 23, 2009
ANCHORAGE, Alaska -- Mount Redoubt ended weeks of seismic unrest and suspense with a series of six powerful eruptions late Sunday night and Monday, depositing ash in the Susitna and Kuskokwim valleys.
The eruptions, which began at 10:38 p.m. Sunday, also disrupted air traffic into and out of Ted Stevens Anchorage International Airport.
"These events were very large, explosive eruptions of Redoubt Volcano," geophysicist John Power with the U.S. Geological Survey and Alaska Volcano Observatory said at an early morning press conference.
Reports of ash fall came in from Skwentna, Talkeetna, Wasilla and Trapper Creek throughout Monday morning, ranging from one-eighth to one-quarter of an inch.
Monday afternoon the National Weather Service reported ash fall at Denali National Park headquarters along the eastern Alaska Range, as well as farther south in Cantwell.
Views of the volcano from Kenai, just 50 miles away, were obscured by clouds.
Acting Anchorage Mayor Matt Claman's office issued a release around 9:30 a.m. stating ash fall in Anchorage was not expected. Schools in Anchorage and the Mat-Su remained open Monday and were expected to remain so barring significant changes in ash fall projections.
A flash flood warning was issued for the Drift River near Mount Redoubt immediately after the first eruption, but it has since expired.
A Chevron oil terminal at Drift River just 27 miles from the volcano initiated shutdown procedures early Monday to "both protect the health and safety of its employees and contractors and to safeguard the environment against a possible spill from its crude storage operations at its facility," Cook Inlet Pipe Line Co. said in a press release.
AVO reports that ash plumes were sent as high as 60,000 feet above sea level, but the bulk of the ash volume was between 25,000 and 30,000 feet. Currently there are no reports of ash emission.
In addition to the initial eruption, the Alaska Volcano Observatory reported large explosions at 11:02 p.m., 12:14 a.m., 1:39 a.m., 4:31 a.m. and 7:41 p.m. Each eruption lasted anywhere from four to 30 minutes.
"There's still a great deal of unrest," Power said Monday afternoon. "We are, based on what we know about Redoubt, expecting that we will see perhaps additional ash-producing eruptions over the next 24 to 48 hours."
And this could just be the beginning of a prolonged period of eruptions.
"The eruption we are most familiar with -- which occurred in 1989, 1990 -- explosive activity got going, went on for a period of about a week and then sort of quieted down," Power said. "We had some dome growth occurring, that then proceed to alternate between dome growth and explosive activity for about five months."
Gov. Sarah Palin encouraged Alaskans to follow safety procedures. Government agencies have been formulating response plans over the last several weeks.
"We are working closely with other state and federal agencies to help mitigate the hazards this eruption is currently posing," Power said. "We have been personally assured by Secretary (Ken) Salazar that the safety of people in Alaska is the highest concern of the Department of the Interior."
Local hardware stories are operating with extended hours for the time being and are well-stocked with emergency supplies.
Field crews are scheduled to visit Redoubt, located 106 miles southwest of Anchorage, sometime Monday to conduct observation and repairs.
"The eruption itself has damaged or destroyed some of our sensors," Power said. "We've lost, so far, three seismometers that were operating on the volcano. We're still in a good position, we have seven operating instruments on the volcano.
"We are planning to have a field crew access the volcano via helicopter. Their mission is to perhaps repair some of our instrumentation that is down -- in addition to the seismic stations, we've also lost the feed from our Web cam that is north of the volcano."
The eruption of Redoubt concluded a six-week period of intense, elevated unrest at the volcano, and an even longer period of suspect behavior.
"This activity is something we've been expecting to see at Redoubt," Power said. "We first began tracking unrest at Redoubt in July of 2008."
Seismicity decreased over the last 10 days or so, until Redoubt began rumbling again on Friday.
"What we've seen at Redoubt over the last two days is a very marked buildup in earthquake activity, earthquakes centered directly beneath the summit of the volcano," Power said.
Those earthquakes in the 60 hours preceding Sunday night's eruption likely signaled the upward movement of magma toward the surface.
Channel 2 News and KTUU.com continue to monitor events at the volcano. We will break into programming on TV and send e-mail and text message bulletins as warranted.
Channel 2 News reporters Jason Lamb in Anchorage, Leyla Santiago in Kenai, and Lori Tipton in Petersville contributed to this report. Contact the KTUU newsroom at firstname.lastname@example.org