Alaska's Mount Redoubt has simmered down after spreading a layer of gritty volcanic ash over scores of communities that include the state's largest city.
The volcano was emitting low-level tremors Sunday but no more eruptions, monitors at the Alaska Volcano Observatory said.
Seismicity increased when a plume rose 25,000 feet above sea level, but scientists said it appeared to be only vapor and they were not counting it among Redoubt's 18 eruptions during the past week.
The calm follows several strong eruptions Saturday that spewed an ash cloud 100 miles northeast to Anchorage, the state's largest city, and beyond.
Ted Stevens Anchorage International Airport shut down because of the ash, which can cause dangerous damage to engines.
Crews there were cleaning up runways, taxiways and passenger gates on Sunday, and one of the airport's three runways opened about 2 p.m., said airport spokeswoman Linda Bustamante. The airport is expected to be in full operations by Tuesday evening.
"The idea is to spread snow on top of the ash, get an ash-and-snow mix, then go out with graders with big blades in front, plow and truck the snow out," she said. "This is quite a cleanup going on."
Alaska Airlines, the state's largest carrier, canceled all flights in and out of Anchorage Saturday after the airport was shut down. The airline resumed flights to and from Anchorage late Sunday afternoon.
Nikiski, about 50 miles from Redoubt, was among the worst hit communities.
Observatory volcanologist Game McGimsey said the ash accumulation there was as thick as a dime, although old-timers there say they've seen much worse.
The ash — with the look and feel of dry, pulverized clay, but much more abrasive — can seep through car filters into the engine, but so far no one has reported any problems to mechanics at Steve's Chevron in Nikiski.
"Some of the hearty locals say, 'We didn't get any ash. Remember when we got three or inches?"' said station attendant Rick Olmsted, who was living in Cusick, Wash., when Mount St. Helens blew with ferocious force in 1980.
Cusick, 285 miles away, got dusted and so did other states.
"Now, that's ash," Olmsted said.
Anchorage's dusting was more than enough for many residents, particularly in the southern sections where the ashfall was heavier, turning snow in yards a dark, dingy gray.
Steve Morris, manager of the city's air quality program, said most of the ash particles are very large and would be difficult to breathe in.
Still, being caught unprepared in the ashfall could be uncomfortable, the particles exuding a hint of sulfur and stinging the eyes, nose and throat.
After the ash began to fall Saturday evening, a neighborhood True Value hardware store quickly sold out of face masks as panicky customers stormed in. People also were snapping up air filters and tarps and, on Sunday, cleaning supplies, said clerk Roger Foraker.
"You really don't clean this," he said. "You let it clean itself off."
Foraker had a more pressing concern. His wife has been stuck in Seattle since Thursday, trying to get a flight home.
"And she was on vacation for three weeks before that," he said.
Redoubt became active a week ago. McGimsey said the eruptions are like "bullets coming out of a gun barrel."
The volcano last erupted in 1989-90. A 1989 eruption sent ash 150 miles away into the path of a KLM flight carrying 231 passengers, flaming out its four engines. Pilots ultimately restarted the engines and landed safely.
The latest activity has caused flooding and mud flows into the Drift River valley, where the Chevron-operated Drift River Terminal is located. The terminal has 6.2 million gallons of oil stored in two tanks.