The Alaska Volcano Observatory (AVO) issued a red alert warning this week when the Pavlof Volcano shifted into an intense eruption, sending ash 22,000 feet into the air.
Pavlof is located in an uninhabited region of the Alaska Peninsula, 625 miles southwest of Anchorage.
This is the state's first red alert since 2009, Reuters reports, when Mount Redoubt sent ash flying 50,000 feet into the air, disrupting air traffic.
This week's eruption didn't aggravate airline activity.
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Pavlof's alert level was slightly lowered to Orange by late Tuesday because seismic tremors had decreased for the past 12 hours, but scientists are still watching the volcano closely.
"It can erupt for weeks or months," observatory research geologist Michelle Coombs told Reuters.
The event over the weekend was unusual because scientists did not initially detect elevated seismicity below the mountain. Instead, scientists using satellite signals detected elevated surface temperatures late Friday afternoon.
A lava flow began from a vent on the north side of the mountain a few hundred meters from the peak, and scientists began to see plumes heading to the east and northeast at 9,000 to 10,000 feet.
Around 3 p.m. Monday, there was a considerable uptick in seismicity, according to Game McGimsey, a volcanologist at the observatory, prompting the red warning alert.
Photos posted by the AVO capture the volcanic activity during the event.
Information from the Associated Press was used in this report
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