ANCHORAGE - Mount Redoubt continues to rumble and simmer, prompting geologists to say this Alaska volcano could erupt "within days."
Scientists from the Alaska Volcano Observatory have been monitoring activity round-the-clock since the weekend.
If Mount Redoubt does erupt, it would be the first time this occurred in nearly 20 years. And if won't likely be pretty.
History shows that volcanoes in Alaska, including Redoubt, typically erupt explosively, shooting ash almost eight miles high.
This differs from volcanoes in Hawaii, which usually have slow rolling lava that oozes out.
The difference is gas trying to escape gets blocked, possibly by a lava dome or a viscous magma that increases the power from beneath, said observatory geologist Jennifer Adleman.
"Its pressure keeps building and building," she said.
Depending on the winds, the ash plume could be pushed straight at Anchorage, the state's largest city. This has prompted state and city officials to post bulletins on how to deal with the ash.
Stay inside as much as possible.
Wear a mask or wet bandanna if going outside.
Those who wear contacts should consider wearing goggles.
According to the U.S. Geological Survey, volcanic ash features small, jagged pieces of rock and glass.
The last time this 10,197-foot peak blew was during a five-month stretch starting in December, 1989. It disrupted international air traffic and placed a layer of volcanic dust throughout the Anchorage area.
Concerns over an eruption have state and city officials issuing warnings so area residents can deal with an ash storm.
The mountain is about 100 miles southwest of Anchorage.