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Alaska's Mount Redoubt continued its volcanic explosions Friday, sending an ash cloud 50,000 feet above sea level and prompting drivers to head to the auto parts store for new air filters.

The National Weather Service said most of the ash was expected to fall to the north, but trace amounts of ash from Friday morning's eruption and smaller ones overnight could fall on Anchorage itself.

Since the series of eruptions began Sunday night, the volcano has had several bursts. One on Thursday sent ash 65,000 feet high. The last time the volcano had erupted was during a four-month period in late 1989 and early 1990.

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Airborne volcanic ash, even in relatively small amounts, can damage airplane and automobile engines. Because of the eruptions, Alaska Airlines, the state's largest carrier, said there were limited flights in and out of Anchorage.

Cissy Matson, manager for the NAPA Auto Parts store in suburban Eagle River, said dozens of people had come in Thursday asking about air filters and it looked like it would be another busy day Friday.

Early Friday morning, Matson was outside the store giving Becki Ezzell a quick lesson on where to put the new air filter she was buying for her 20-year-old daughter's car.

"I know that ash chokes off the air to the engine and it just stops. That would be very scary for her," Ezzell said.

Jack Jones, co-owner of J&S Auto in Peters Creek about 25 miles north of Anchorage, said a more commonplace product could also help protect an engine: "I would definitely buy some pantyhose to put over the air intake — whatever you can do to keep some of that (ash) out of there."

Ezzell had another worry, too: The eruption had stranded her husband at the Minneapolis airport.

"They were just getting on the plane and it blew," Ezzell said. "He thought he was on his way home."

Still, Ezzell, who has lived in Alaska since 1969, said she's seen far worse when it comes to volcanoes exploding and spewing ash.

"I'm not going to make a big to-do about a little ash," she said.

The largest eruption Thursday caused a mud flow into the Drift River near the base of the volcano.

Before Thursday's eruptions, the volcano had been relatively quiet for more than a day.

"We can have these large explosions pretty much any time," said Stephanie Prejean, an observatory seismologist. "We don't know how long this will continue."

Ash dropped Thursday afternoon on Homer, a tourist and fishing town at the southern tip of the Kenai Peninsula.

Juxia Scarpitta, owner of Halcyon Heights Bed and Breakfast in Homer, said the ash had obliterated her view of the bay and turned the snow into what looked like a carpet covered with gray dots.

"It is falling pretty fast," she said.

Research geologists with the U.S. Geological Survey have said a lot of snow and ice remains on the mountain, increasing the danger from mud flows that already have downed hundreds of trees and carved a huge gouge out of a glacier.

The mud flows also have littered the airport at the Drift River Terminal, a Chevron-operated facility that has been shut down but still has 6.2 million gallons of crude stored in two tanks. Until the airport runway is cleared, it is unusable.

Prejean said it was not known if the mud flow produced Thursday reached the oil storage facility.

Eleven employees were evacuated from the terminal Monday. Lana Johnson, a consultant for Cook Inlet Pipeline Co., said two crews reached the terminal by helicopter on Thursday but were evacuated when the volcano erupted.

Previous flights had indicated that the oil storage tanks were not damaged and surrounding berms and dikes to contain any spilled oil were also OK.

Johnson said there was monitoring equipment at the terminal that could be read remotely, and the system indicated the tanks were holding the oil.

Sara Francis, spokeswoman for the U.S. Coast Guard, said "the safest place for that oil to be right now is in those tanks."

Scarpitta, the B&B owner, said she's expecting the arrival of visitors "from another disaster area" — along North Dakota's Red River, where a historic crest was expected Saturday and thousands of sandbaggers were trying to prevent widespread flooding.

Scarpitta said a family was coming so one of them can celebrate his birthday in Alaska.

"He is still coming right now. I advised him to get trip insurance," she said.