(TNS) - Margaret Mangan didn’t sleep well in the weeks following the Ridgecrest, Calif., earthquakes. The July shaking triggered a swarm of smaller tremors in the nearby Coso Volcanic Field, a cluster of lava domes and cinder cones at the northern end of the Mojave Desert. And it was Mangan’s job to watch for a possible eruption.

“We were pretty much on 24-7 vigilance,” said Mangan, the longtime scientist-in-charge of the U.S. Geological Survey’s California Volcano Observatory.