An active island volcano situated in the Pacific Ocean under one of the world's busiest flight paths has barely stopped erupting since Christmas and is nearing its 40th explosion in months.
Bogoslof volcano, nestled in the Aleutian Islands about 98km northwest of Dutch Harbour, Alaska, US, has been in the midst of an "active eruption sequence" since mid-December 2016.
It has erupted more than 37 times since then and sent up another ash cloud as recently as Monday. The Alaska Volcano Observatory said the latest eruption lasted 12 minutes.
The observatory said the magnitude of the eruption was being monitored.
Monday's eruption of the volcano did not immediately prompt an aviation warning for pilots although another explosion the previous week saw authorities issue a warning about ash at elevations that could affect flights.
The recent Bogoslof volcano eruptions have each lasted on average about 30 to 60 minutes with volcanic ash spewed to altitudes exceeding 30,000 feet.
"Eruptive activity has been dominated by a series of explosive events originating from below sea level," according to the US Geological Survey (USGS).
"(That has) resulted in drifting clouds of ash that threaten not only local air traffic, but also wide-body jets flying between North America and Asia.
"The most significant - and common - hazards from Alaska volcanoes are those created by ash clouds and ash fall."
Alaska's volcanoes lie under Pacific aircraft routes and can erupt ash clouds into commercial and recreational airspace.
Bogoslof's periodic eruptions have prompted warnings to airliners and a major US fishing port in the Aleutian Islands.
"Ash and aircraft do not mix, as volcanic ash is abrasive, melts at jet engine temperatures, and can cause engine failure," a US Geological Survey spokesperson said.
"North Pacific and Russian Far East air routes pass over or near more than a hundred potentially active volcanoes. Aircraft flying along these routes, some of the busiest in the world, carry more than 50,000 passengers and millions of dollars of cargo each day to and from Asia, North America, and Europe.
"In the North Pacific region, several explosive eruptions occur every year. Ash from these eruptions, which has caused jet engines to fail, is usually blown to the east and northeast, directly across the air routes."
Ash clouds rising above 20,000 feet are a threat to jets flying between Asia and North America.
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.
It is uncertain how long eruptions of Bogoslof will continue, according to the US Geological Survey. Some volcanoes, including Vanuatu's Mount Yasur and Italy's Mount Etna have continuously erupted for more than a century.
The National Weather Service warned that trace amounts - less than one millimetre - of ash from the recent eruptions could settle on Dutch Harbour, a major port for Bering Sea crab and pollock.
US Geological Survey geologist Kristi Wallace said the 36th eruption was "the most significant event for the entire eruption" and took place earlier this month.
Wallace said the eruption was marked by 200 lighting strikes and elevated seismic activity that lasted for days.
"And then it just shut off," she said.
The current eruptions are from a shallow, underwater vent on the island's southeast side.
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 volcano remains in a heightened state of unrest and could erupt again at any time.
Fine ash drifting to cities can cause respiratory problems for people and animals, interfere with electrical equipment and damage air filters and gasoline engines.
Wallace said the observatory had received reports of light dustings of ash in the Unalaska and Dutch Harbour, Alaska, about 100km southeast of the volcano.
The community is home to about 4500 people but winds have reportedly blown the ash cloud away from the island.
Unalaska Department of Public Safety communication officer Donnie Lane said police had not received any reports of ash falling on the community.