© Flickr/ NASA's Marshall Space Flight Center
Scientists raised the alert level for a remote Aleutian volcano on Monday after an explosion was detected on the mountain and heard by residents of a tiny village some 45 miles (72 km) away, a monitoring website said.
Cleveland Volcano, a 5,676-foot (1,730-metre) peak on the uninhabited Chuginadak Island, about 940 miles (1,504 km) southwest of Anchorage, was raised to orange from yellow by the Alaska Volcano Observatory.
The orange code, the second-highest on the scale, is issued when a volcano is "exhibiting heightened or escalating unrest with increased potential of eruption," according to the observatory. A red code is issued when an eruption is imminent or under way.
The observatory said that an explosion was detected on Cleveland by both infrasound and seismic data and heard by residents of Nikolski, a settlement of less than 50 people on Umnak Island about 45 miles (72 km) to the east.
Infrasound instruments measure air pressure around the volcano.
Scientists said that cloudy weather obscured Cleveland's peak in satellite images but that no evidence of an eruption cloud had been detected at a height of 28,000 feet (8,534.4 meters).
