Ice Sheets, Sea Level, Human Migration, and Pluvial Lakes

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At the height of the last Ice Age, large continental ice sheets covered much of North America, transforming the continent far beyond the areas buried beneath the ice. Their growth and retreat changed sea levels, coastlines, climate, and entire landscapes. Understanding those changes is essential to one of the central questions of SAR’s Ice Age in New Mexico series: when and how could people have entered North America and traveled south of the ice sheets?

Geologist Jorie Clark reconstructs this changing continent, from the growth of the ice sheets and the closing of potential migration routes through the Ice-Free Corridor and along the Pacific coast to their retreat after the Last Glacial Maximum, approximately 21,000 years ago. As the ice receded and sea levels changed, coastlines shifted, barriers disappeared, and new possibilities for human movement emerged.

Clark brings the story south to the American Southwest, where the effects of the ice sheets helped create a world almost unrecognizable today including vast lakes across areas that are now desert. Reconstructing that lost landscape gives us critical context for understanding the people who lived here and what they left behind. To understand the earliest human history of North America, we first have to understand the landscapes those people were navigating.

Jorie Clark has a B.S. in Anthropology, a B.A. in Geology, an M.A. in Interdisciplinary Studies, and a Ph.D. in Geology. She is a Courtesy Associate Professor in the College of Earth, Ocean, and Atmospheric Sciences, Oregon State University. Her research interests include paleoclimate, history of Pleistocene ice sheets, sea level change, and risk of climate change to cultural resources. She has conducted field work in Europe, the Canadian Arctic, Greenland, and across the western U.S. and has published widely including in Science, Proceedings of the National Academy of Sciences, Geology, and Climate Risk Management.