Almost 20,000 years ago, Earth's climate began to warm. Because of the changing temperatures, a miles-thick ice sheet started to shift. As the ice sheet moved, it carved deep pits in the land and left water in its wake. This melted ice filled the new cavities. This is the story of America's Great Lakes: Superior, Michigan, Huron, Erie, and Ontario. Enriched with stunning photographs and informative fact boxes and sidebars, this educational book sheds light on the scientific history of some of our nation's most treasured geological features.