The Ice Age in Wisconsin

More than 10,000 years ago, great glaciers, sheets of ice over a mile thick, covered much of the northern United States, including most of Wisconsin. As they were forming, the slow-moving glaciers ground bedrock into fine powder and transformed a rough terrain into rolling plains. The ice stopped short of southwestern Wisconsin, leading this part of the state to be known as the “Driftless Area”.

As the glaciers melted, torrents of meltwater tore across the landscape carving gorges and dropping rocks and soil in new locations. Debris that was carried in and on the ice was deposited to form hills called moraines and kames. Drumlins were formed at the base of glaciers and kettles were formed by the melting chunks of ice. Swirling water and rocks wore round potholes in solid bedrock. Most of the lakes and wetlands in Wisconsin were formed by the melting glaciers.

The melting glaciers formed the Dalles of the St. Croix gorge and this pothole on the western end of the Ice Age Trail.
Photo © Wisconsin Department of Tourism

These terrain features are most visible near what was the edge of the glaciers, known as the terminal moraine. This is the boundary where the glaciers stopped and began melting. To preserve these features for the public to learn from and enjoy, the Ice Age National Scenic Trail and Scientific Reserve were established.

The Ice Age Trail Alliance, a nonprofit organization, the Wisconsin and United States governments and numerous volunteers and private landowners continue to help develop and maintain the Ice Age Trail along this moraine boundary.

The Ice Age Trail goes through some of Wisconsin's most interesting glacial terrain, such as these hills near Lodi.
DNR Photo by Bonnie Gruber

Glacial Features along the Ice Age Trail

From Interstate State Park on the St. Croix River, through the forests of northern Wisconsin, central plains and the Kettle Moraine, to Potawatomi State Park on Lake Michigan, the Ice Age Trail preserves some of Wisconsin’s most amazing glacial history and provides some of the best evidence of continental glaciation found anywhere in the world.

Drumlin: Oval teardrop-shaped hills formed under the glacial ice near the advancing front of a glacier.

Erratic: Boulders and large rocks carried by glaciers and deposited on the surface of the land after the ice melted.

Esker: A long, narrow ridge of coarse gravel deposited by a stream flowing in an ice-walled valley or tunnel in a melting glacier.

Kame: A conical-shaped hill of sand and gravel that was formed by glacial meltwater swirling into a vertical shaft in the glacier.

Kettle: A depression formed by the melting of a large block of glacial ice that was partially or completely buried. Some kettles hold water to form kettle lakes.

Moraine: Jumbled hills of unsorted, unstratified glacial debris found at the sides or front of a glacier.

More Information

National Park Service - Ice Age Geology [exit DNR]

For more information, ask Wisconsin State Parks, (608) 266-2181.