During the past 2.5 million years, colossal ice sheets gripped the globe, perhaps 15 different times. Glaciers sculpted about one-third of the earth’s landmass. Sometimes 2 miles thick, they stretched from present-day New York to Montana, and from Ohio to Hudson Bay, Canada.
Today, the Ice Age Trail takes you through some of Wisconsin’s most scenic terrain – mature forests, expansive prairies and thousands of lakes and rivers. The story of how this landscape was sculpted starts with the glaciers.
The Legacy of the Ice Age in Wisconsin
Wisconsin is the best place to witness many of the landforms created by continental glaciation. Fittingly, the most recent period of the Ice Age, which ended about 10,000 years ago, is known as the Wisconsin Glaciation.
Near the end of the Wisconsin Glaciation, a series of ridges formed between two immense lobes of glacial ice in what is now southeastern Wisconsin. These ridges are 120 miles long. Scattered among them are crater-like depressions that were created by large chunks of melting ice.
Geologists named this region the Kettle Moraine. Studies that began in the Kettle Moraine during the 1870s led to key discoveries and the first map of the extent of continental glaciation in North America.
What You’ll Find on the Trail
The route of the Ice Age Trail generally follows the last outline of the most recent glacier. The basic features defining the route are the Kettle Moraine of eastern Wisconsin and the most recent terminal moraine as it extends west and north.
Geologic features along the route include kames, lakes, drumlins, ice-walled-lake plains, outwash plains, eskers, tunnel channels, unglaciated features of the Driftless Area and other older landforms. Check out the Ice Age Trail Glossary for definitions of these and other features you are likely to encounter while hiking the Ice Age Trail.
The Trail also diverges in some places to include parts of the Driftless Area, the southwestern quarter of the state that was untouched by the glaciers.
Ice Age Trail Timepieces
The Ice Age Trail primarily interprets continental glaciation, but the story of the Trail goes back much farther on the geologic timeline. As you walk the Ice Age Trail, your footsteps will take you back in time almost 2 billion years. Timepieces you will see along the Ice Age Trail:
- Recent glacially deposited soil, gravel and boulders found in areas of almost every county along the Trail: deposited between 10,000 and 25,000 years ago during the late Wisconsin Glaciation.
- Areas along the Trail covered by earlier continental glaciations in Green County and parts of western Rock, southern Dane and Marathon counties: between 25,000 and 2,500,000 years ago.
- Dolomite of the Niagara Escarpment in Door County: between 410 million and 440 million years old.
- Sandstone rock outcrops of Green, Rock, Dane, Columbia, Sauk and Adams counties: between 460 million and 550 million years old.
- Basalt bluffs and exposures of Polk County: 1.1 billion years old.
- Quartzite of the Baraboo Hills (Sauk County) and Blue Hills (Barron and Rusk counties): 1.6 billion years old.
- Rock outcrops at Grandfather Falls, Lincoln County, and Eau Claire Dells (mylonite), Marathon County: 1.8 billion years old.