Ice Age Trail Landscape and Geology
The Ice Age Trail route will take you through some of Wisconsin's most scenic terrain, highlighting mature forests, expansive prairies and thousands of lakes and rivers. The story of how our modern landscape was sculpted is fascinating. After reading the information below, take time to reflect the next time you are using the Ice Age Trail on the centuries of natural processes that have crafted the places that we enjoy today.
The Ice Age had a profound impact on the world. During the past 2.5 million years, colossal ice sheets repeatedly gripped the globe — perhaps 15 times. Glaciers sculpted, as if by the hand of a potter, about one-third of the earth's landmass. It's hard to imagine the immensity of Ice Age continental glaciers. Sometimes two miles thick, they stretched from today's Long Island, New York, to Montana, and from Ohio to Hudson Bay, Canada. The mountain glaciers we see today in Alaska or the Swiss Alps are tiny by comparison.
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 slowly ended only 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, areas of crater- or kettle-like depressions 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.
The Ice Age further left its mark on the world's plants, animals and even its people. The ranges of all species were compressed toward the equator and then expanded as the great ice sheets melted northward. According to a 1995 Wisconsin Department of Natural Resources report, "The greatest historical event impacting Wisconsin vegetation occurred 10,000-60,000 years ago when Wisconsin was invaded by continental ice sheets." Huge, now-extinct beasts, such as mammoth and mastodon, roamed areas near the glacial ice. Some anthropologists speculate that humans would not have evolved to our present state without the challenges posed during the Wisconsin Glaciation.
The Ice Age Trail courses like a river for a thousand miles through a varied landscape. Walk the Ice Age Trail to witness hundreds of crystal lakes and thriving prairies, productive farmlands, towering white pines and diverse wetlands, ancient Native American effigy mounds, remnant oak savannas, charming cities and many of the world's finest examples of the effects of continental glaciation. The basic features defining the route of the Ice Age Trail are the Kettle Moraine of eastern Wisconsin and extending westward along the most-recent terminal moraine. 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.
For a visual representation of our Ice Age heritage, you can view regional topography and glacial features in the following set of maps (arranged east to west along the Trail's route) showing the Ice Age Trail in various Wisconsin counties:
Door and Kewaunee Counties
Sheboygan and Fond du Lac Counties
Walworth, Jefferson and Rock Counties
Dane and Green Counties
Sauk and Columbia Counties
Adams, Waushara and Marquette Counties
Portage and Waupaca Counties
Rusk, Barron and Washburn Counties
Polk and Burnett Counties
Although the Ice Age Trail primarily interprets the story of continental glaciation, the geologic story of the Trail goes back much farther. As you walk the Ice Age Trail, your footsteps will take you back in time almost two 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.