Scientists are on high alert after threat levels rose for three US volcanoes Thursday, suggesting eruptions may be imminent. The US Geological Survey (USGS) placed Alaska's Great Sitkin on 'Watch ...

Mount Spurr has been showing signs of an eruption since last year, but scientists think one is even more imminent.

Mount Spurr is the tallest volcano in the Aleutian Arc ... (That’s the case currently at Great Sitkin, far out in the Aleutian Islands, which is erupting and on “watch” status).