There's a new lava dome forming on top of Alaska's Cleveland Volcano, and the Alaska Volcano Observatory bumped up its aviation warning level to orange. That means the volcano is "exhibiting heightened or escalating unrest with increased potential of eruption".
It's not clear if the volcano will actually erupt and the observatory says no one has spotted any current ash emissions. It's known as Cleveland Mountain, part of an uninhabited Aleutian Island more than 900 miles southwest of Anchorage, according to USA Today.
Cleveland Mountain formed another lava dome last year, as the observatory reported the crater experienced on-and-off volcanic activity over the summer; it even belched ash clouds into the air, which are hazardous to jet engines.
Although there's nobody to evacuate, scientists report lava could spill over Cleveland's rim and tumble down the mountainside to the Bering sea. The volcano's last big event occurred 11 years ago: three eruptions in February, 2001 sent ash clouds nearly 40,000 feet into the air. As Wired notes, any similar eruption would force airlines to modify routes to avoid the ash.
Last year, Iceland's Grimsvotn volcano erupted, cancelling hundreds of flights; in 2010 the (unpronounceable) Eyjafjallajokull volcano eruption, also in Iceland, diverted thousands of passengers.