[b]Alaska volcano erupts five times after 20-year lull[/b]
(CNN) -- Alaska's Mount Redoubt volcano erupted again Monday morning, the fifth eruption since coming back to life, the U.S. Geological Survey reported.
Darkness and snow obscured the eruptions, which started at 10:38 p.m. Sunday (2:38 a.m. ET Monday). Subsequent eruptions occurred at 11:02 p.m., 12:14 a.m., 1:39 a.m. and 4:37 a.m. local time.
Redoubt was last active in 1989, when eruptions lasted for five months, USGS geophysicist John Power said at an early morning news conference Monday.
"We would expect Redoubt to have some level of explosive activity for the next weeks or months," Power said.
The alert level went to red, the highest level, when the eruptions began, according to the Alaska Volcano Observatory web page.
The USGS estimated the height of the eruption cloud at 50,000 feet and warned that mudflows were possible on the Drift and Crescent Rivers and ashfall was likely downwind from the volcano.
Aviation has been affected, Power said.
"I understand a number of commercial flights have been canceled coming in and out of Anchorage International Airport," Power said. "We could see disruptions to air travel to south central Alaska, and Alaska as a whole, for a period of weeks to months."
Ash from the volcano is expected to blow north and pass west of Anchorage, said Dave Schneider, a geophysicist with the Alaska Volcano Observatory. He described the ash as a trace -- meaning if some landed on a windshield, the driver could still see through it.
Power said the ash will be about the thickness of a penny or a dime but warned residents to take precautions.
"It does pose significant problems for mechanical systems, people with respiratory illnesses, and aircraft," he said, adding that residents should be prepared to stay indoors.
Those in range of the ashfall should seal their windows and doors, the National Weather Service said. It also advised that residents protect electronics, minimize driving and cover air intakes and open water supplies.
Early Sunday, researchers had raised the monitoring status for the volcano, which had been showing increased seismic activity. Officials had predicted an eruption was possible "within days to weeks."
Officials have been monitoring Redoubt since July, Power said, and raised the aviation threat level to yellow in November and orange in January. The threat level alternated between orange and yellow until March 21, when it was last raised to orange, Power said.
Bill Burton, a USGS geologist, said there had been increases in seismic activity at Mount Redoubt since January followed by periods of quiet.
The 10,197-foot peak is about 100 miles southwest of Anchorage, the most populous city in Alaska.