ANCHORAGE - Three explosions at Augustine Volcano, an island peak 171 miles (275 km) southwest of Anchorage, sent ash clouds soaring nearly 10 miles (16 km) above sea level on Friday, officials said.
The explosions, lasting 3 1/2 to 11 minutes each, followed two similar events on Wednesday and were part of an eruptive period that could last for months, said Tina Neal, a geologist with the federal-state Alaska Volcano Observatory.
"This is one big eruption period, and it's going to have several sub-events that we might call eruptive pulses," she said.
Alaska Airlines announced the cancellation of 28 flights between Friday afternoon and Saturday morning as a precaution, including routes from Anchorage to Los Angeles and Seattle.
A pilot reported ash from the second explosion as high as 52,000 feet (15,850 metres) above sea level, Neal said.
Ash clouds from the other two explosions reached 30,000 to 36,000 feet (9,145-10,970 metres), according to the observatory.
A "very light dusting" of ash was reported near Homer, a community about 75 miles (120 km) northeast of Augustine, Neal said.
The ash fall was reported by a National Weather Service observer, said Dave Schneider, a US Geological Survey official at the volcano observatory. According to that report, he said, "You can almost taste it in your mouth, but you can't perceive it any other way."
Augustine's previous eruptions were in 1986 and 1976. In both those years, the volcano had several ash- and steam-producing explosions that ran over a prolonged period, according to the Alaska Volcano Observatory.
The current activity, which was preceded by months of small but intensifying earthquakes below the volcano, is similar to that in the past, Neal said.
"This is typical Augustine behavior," she said.
Flight restrictions around Augustine have been in place for the past few days.
Augustine, a conical-shaped peak, rises 4,134 feet (1,260 metres) out of Cook Inlet, forming its own uninhabited island. It is the most active of the Cook Inlet volcanoes, according to the Alaska Volcano Observatory.
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