An Alaska volcano that has erupted periodically since mid-December has sent up its biggest cloud to date, prompting warnings to airliners and a major US fishing port in the Aleutian Islands.
Bogoslof Volcano erupted late on 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 of ash could settle on Dutch Harbour, 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 lightning strikes, she said, and elevated seismic activity that lasted until 1.30am on Wednesday.
"And then it just shut off," Ms Wallace said.
The volcano is 850 miles south-west 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 interfere with electronics of navigation systems.
Huge new lava outbreak at #Kilauea volcano, Hawaii & Large explosive eruption ejects ash 10.6 km (35 000 feet) at #Bogoslof, Alaska pic.twitter.com/FwWuIgOv8N— magaly ferrer (@maga33141) March 8, 2017
Fine ash drifting to cities can cause respiratory problems for people and animals and interfere with electrical equipment.
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 south-east side.