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.
For several weeks, she personally monitored thousands of quakes via an automated alert system that pinged her phone at all hours. Occasionally, she had to wake a colleague in the middle of the night to make sure the shaking pattern didn't point to rising magma.
California is famous for its catastrophic earthquakes and wildfires, but they are not the state's only natural hazards. As head of the observatory, or CalVO, Mangan has drawn attention to the state's more overlooked threats: a dozen restive volcanoes that stretch from Medicine Lake near the Oregon border to the Salton Buttes in the Coachella Valley.
"Most people are surprised that there are any volcanoes in California," said Kari Cooper, a geologist at the University of California, Davis. "It's just really not on people's radar."
It should be. According to a report Mangan and her colleagues released this year, the risk of a small-to-moderate eruption somewhere in the state over the next 30 years is 16% -- about the same as for a magnitude 6.7 or greater earthquake along the San Andreas Fault.
Those odds are "not something to ignore," she said.
For Mangan, the threat of a volcanic crisis is not merely hypothetical.
She began her career at the USGS' Hawaii Volcano Observatory in 1990, just as Mount Kilauea began to pave over the town of Kalapana on the Big Island. It was the first time she had seen an eruption with her own eyes.
"For a volcanologist," she said, it was "almost a religious experience."