Scientists are on high alert after spotting a key sign that a US volcano is about to erupt. Huge plumes of steam have been seen rising from Mount Spurr, one of Alaska's largest active volcanoes ...

Slow magma flows, small chambers, and hot rock all contribute to surprise volcano eruptions that occur without any prior warning.

On March 7 and 11, the AVO flew aircraft over the summit and over Crater Peak to gather samples of gas rising from the volcano. These flights showed that the Mount Spurr summit is now producing ...