An erupting Mount Redoubt exploded again this morning at 4:31 a.m. -- its fifth and strongest discharge yet -- sending an ash cloud to new heights, the Alaska Volcano Observatory reported.
Ash has now been detected at an elevation of 60,000 feet above sea level, the National Weather Service reported.
Winds are still carrying the ash plume north over the Susitna Valley, and minor ash fall has been reported in Skwentna, Trapper Creek and Talkeetna.
Ash is not expected in Anchorage or Wasilla at this time, the Weather Service said.
Northwest of the city, the ashfall is being described as fine gray dust.
"It's coming down," Rita Jackson, 56, said early Monday morning at a 24-hour grocery store in Willow. She slid her fingers across the hood of her car, through a dusting of ash. She said she was taking a sip of coffee when she tasted something funny on her lips — ash. She said she hurried home to get a motorcycle, snowmachine and vehicles under protective blue tarps.
Redoubt began erupting last night, with the first explosion coming at 10:38 p.m. Sunday followed by another at 11:02 p.m., and a third at 12:14 a.m, the AVO reported.
Ted Stevens Anchorage International Airport remains open, although some airlines have canceled or diverted flights. Alaska Airlines reported canceling 19 flights in and out of Anchorage because of the ash.
Elmendorf Air Force Base reported that 60 planes, including fighter jets, cargo aircraft and a 747 commercial plane, are being sheltered.
School is in session in Anchorage and the Matanuska-Susitna Borough.
The 10,200-foot Redoubt Volcano, roughly 100 miles southwest of Anchorage, last erupted during a four-month period from 1989-90.
Observatory staffers notified Federal Aviation Administration officials immediately following the eruption.
An FAA official at the Anchorage airport early Monday said there were no immediate plans to close the airport.
The AVO staff also warned authorities at the Drift River Oil Terminal -- on the western shore of Cook Inlet downriver from the volcano -- that mud flows and flooding from melting glaciers might be headed their way.
Cook Inlet Pipe Line Company, which operates the terminal, said early this morning that it had begun shutting the facility down.
At a 3 a.m. press conference today John Powers of AVO said given the hot material landing on snow, mud and snow slides could be expected and staff would check the Drift River area at first light today.
Protective dikes have been constructed at the terminal since Redoubt last erupted in 1989.
Powers also said looking at the history of Redoubt eruptions the event could be expected to go on for some time, even months. Eruptions in 1989 and 90 lasted about five months as did some prior events, he said.
For two hours, prior to the eruption, AVO scientists reported heightened seismicity at Redoubt and warned there could be a quick escalation to eruptive activity.
The volcano had been on Orange "watch" status for most of Sunday after activity began increasing Saturday, but was changed to Red after the first eruption.
The Associated Press contributed to this story.
By GEORGE BRYSON