An Alaska volcano that has erupted periodically since mid-December sent up its biggest cloud to date late Tuesday night and into Wednesday morning, prompting warnings to airliners and a major US fishing port in the Aleutian Islands.
Bogoslof Volcano erupted at 10:36 pm Tuesday, spewing ash for three hours and sending a cloud of it to 35,000 feet, the Alaska Volcano Observatory reported.
The National Weather Service warned that trace amounts — less than 1 millimeter — of ash could settle on Dutch Harbor, a major port for Bering Sea crab and pollock.
It was the 36th eruption for Bogoslof over the last three months, and the first since February 19.
"It was the most significant event for the entire eruption," said US Geological Survey geologist Kristi Wallace.
The eruption was marked by 200 lighting strikes, Wallace said, and elevated seismic activity that lasted until 1:30 am Wednesday.
"And then it just shut off," Wallace said.
The Aleutians Island volcano is 850 miles southwest of Anchorage. The volcano remains in a heightened state of unrest and could erupt again at any time.
Ash clouds rising above 20,000 feet are a threat to jets flying between Asia and North America. Air traffic controllers receive an advisory after eruptions and warn jets to fly around or above ash clouds, which can drift for hundreds of miles.
Volcanic ash can erode jet engine turbine blades. Ash melted by high temperatures in the engines adheres to critical parts and can cause engine failure, according to the observatory. Ash can also scrape cockpit windows and interfere with electronics of navigation systems.
Fine ash drifting to cities can cause respiratory problems for people and animals, interfere with electrical equipment and damage air filters and gasoline engines.
Bogoslof Island is the tip of an underwater volcano that extends down 5,500 feet in a cone shape to the floor of the Bering Sea. The island first appeared after an underwater eruption in 1796. Subsequent explosions and eruptions have caused the island to grow and shrink.
The current eruptions are from a shallow, underwater vent on the island's southeast side.
The city of Unalaska and Dutch Harbor are about 63 miles southeast of the volcano. Donnie Lane, communication officer for the Unalaska Department of Public Safety, said police had not received any reports of ash falling on the community as of Wednesday morning.
Wallace said the observatory had received reports of light dustings of ash in the community of about 4,500 people but that winds may have blown the ash cloud away from the island.