(AP) -- An Alaska volcano continued to rumble Tuesday amid new concerns that eruptions and mud flows will damage a nearby oil terminal where about 6 million gallons of crude are stored. The 10,200-foot Mount Redoubt volcano, about 100 miles southwest of Anchorage, erupted Sunday night. Since then there have been five more explosions; the latest, on Monday night, shot an ash plume into the air that was 40,000 to 50,000 feet high.
The volcano has been relatively quiet since, but that is not expected to continue, said Stephanie Prejean, a research geologist with the U.S. Geological Survey. The last time Redoubt erupted was in 1989, when there were more than 20 explosions as magma pushed to the surface and formed domes that later collapsed and sent ash plumes into the air.
"This is very typical for volcanoes of this type," Prejean said. "These domes ooze out of the earth. They are very thick, like toothpaste."
She said that when this type of volcano is in the dome-building phase, as it is now, things can happen quickly, making it difficult to warn people about any explosions.
Mud flows from the volcano have downed hundreds of trees and filled the Drift River Valley with debris, said USGS research geologist Kristy Wallace. Ash collected near the volcano is fairly coarse, with some pieces measuring 3 inches across, she said. There is evidence that magma has reached the surface.
On Monday, 11 people were evacuated by helicopter from the Drift River Terminal, a Chevron-owned facility near the base of the volcano. The terminal has been shut down but oil remains in two of its seven tanks.
The Coast Guard is working with the state Department of Environmental Conservation and the Cook Inlet Pipeline Co. to determine if the oil should be removed and how it could be done, said Sara Francis, a Coast Guard spokeswoman.
Francis said a flyover of the facility on Monday afternoon indicated that the storage tanks are not damaged. Earthen berms that surround each tank also appear to be OK, though water appeared to have flowed over a berm that surrounds the tank farm.
"The tank farm is entirely intact, no sheen or spill has been sighted," Francis said. She said all the tanks are "quite distant from any mud or debris."
Cook Inletkeeper, a conservation group, on Tuesday called on Chevron and state and federal agencies to remove the oil from the tanks to protect Cook Inlet's valuable fisheries.
Bob Shavelson, the group's executive director, said there is flooding and a lot of debris moving into the area near the terminal.
"Everything is pretty much in flux," he said. "We feel Chevron has an obligation to protect those fisheries."
A Chevron spokeswoman did not immediately return a call for comment.
Tom Evans, an Alaska Native from the lower Cook Inlet village of Nanwalek, said people depend on inlet fisheries to feed their families.
"It makes no sense to store oil at the base of an erupting volcano," he said.
Alaska Airlines resumed flights to and from Alaska on Tuesday after ash clouds from eruptions this week forced the cancellation of 35 flights.
The airline's jets at the Anchorage airport were wrapped in a protective plastic sealant and unsealed Tuesday morning. The airline says the sealant protects aircraft from abrasive ash particles, which post a significant danger to engines.
Further eruptions could alter scheduled flights.
On the Net:
Alaska Volcano Observatory: http://www.avo.alaska.edu
©2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
Explore further: Improving forecasts for rain-on-snow flooding