Mount Augustine Volcano erupted early Wednesday, sending an ash plume an estimated 30,000 feet into the Alaska sky.
A pair of explosions at 4:44 a.m. indicated the volcano probably had erupted, said geologist Jennifer Adleman of the Alaska Volcano Observatory said.
Residents of Clam Gulch on the Kenai Peninsula confirmed the eruption and reported seeing ash, Adleman said.
"I don't know if they're seeing it on the ground or in the air," Adleman said.
The observatory after sunrise at 10:03 a.m. planned to make observation flights to get more information about the types of gases emitted from the volcano, Adleman said.
The plume was expected to head north and east.
No flight restrictions
A duty officer at the Federal Aviation Administration operation, who would not give his name, said he had not seen any new restrictions on flights as of 7 a.m.
"It looks like the ash cloud is likely to remain east of Anchorage," he said. "At this time, I have not seen any impact," he said.
The 4,134-foot volcano about 180 miles southwest of Anchorage last erupted in 1986. Ash from a 7-mile-high column drifted over Anchorage and kept flights out of the skies over Cook Inlet.
The explosions, with magnitude 2.6 seismic activity, occurred at 4:44 a.m. Alaska Standard Time, and the observatory upgraded the level of concern from orange to red, meaning a significant eruption was occurring or an explosive eruption was expected at any time.
About eight hours earlier, at 9:05 p.m., the observatory had upgraded the level of concern from yellow, or restless, to orange, meaning an eruption could occur at any time.
For the previous six hours, the observatory had detected that "markedly" increased earthquake activity.
The observatory has a Web cam stationed at the mountain.
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On the Net:
Alaska Volcano Observatory: http://www.avo.alaska.edu