Big Island, Hawaii
Years on Job: 5
When Mike Poland arrived three months late for his post at the Hawaiian Volcano Observatory, the 30-year-old had a doozy of an excuse: Mount St. Helens, where he'd been stationed, started bellowing steam and ash just before his December 2004 transfer. A volcanic deformation specialist with the U.S. Geological Survey, Poland uses mapping-grade GPS units precise to within a few millimeters -- 1000 times more accurate than recreational models -- to analyze surface changes and gauge activity in magma chambers underground. "By measuring ground movement," he says, "we see signs if a volcano is working toward erupting."