National Geographic Explorer Erin Pettit studies glaciers to better understand and predict changing climate and rising seas. She is an associate professor of geophysics and glaciology at the University of Alaska Fairbanks and creator of Inspiring Girls Expeditions, which puts on wilderness science experiences for teenage girls. As a field glaciologist, Erin listens, watches, and measures the flow, fracture, advance, and retreat of glaciers and ice sheets. She has traveled from the North Slope of Alaska to the interior of Antarctica for research expeditions. She studies the deep old ice in the interior of Antarctica to understand past climate, and she studies the ways water infiltrates snow and ice, affecting temperature and the movement of the ice. But the boundary where glacial ice flows into the ocean is her favorite place to explore.