Noting a swarm of tiny earthquakes beneath volcanic Mount Spurr, scientists have warned that the volcano 80 miles west of Anchorage could erupt in the next few weeks.
Eruptions most often follow a pattern of quakes, said geophysicist John Power of the U.S. Geological Survey, one of three federal and state partners in the Anchorage-based Alaska Volcano Observatory.
Power added, however, that the earthquakes will most likely end without an eruption.
Mount Spurr was last significantly active in 1992. In an August explosion that year, it spread a thin layer of ash over Anchorage.
The mountain's recent activity began slowly in February and intensified July 4, the observatory said this week. An average of 20 small quakes are now occurring daily, a rate higher than at any time since 1992.
The temblors occur as deep as four miles below the surface. The largest recent quake was on July 12 and measured 1.4 in magnitude.
Mount Spurr is one of more than 40 active Alaska volcanoes.