Plan Your Visit - Ice Age Floods National Geologic Trail (U.S. National Park Service) When the ice dams broke, huge walls of water raced to the Pacific Ocean, cutting new canyons and depositing sediments. The impact of these floods covers thousands of square miles in the Pacific Northwest, too large an area to be fully covered by a single site. Today the efforts of many agencies to tell this phenomenal story are linked together by the creation of the Ice Age Floods National Geologic Trail, the nation's first national geologic trail.