The Baraboo Hills, which form an elongated, discontinuous ring in Sauk and Columbia Counties, rise approximately 700 feet above the surrounding landscape. They are composed of near-shore ocean sediment, depoisted about 1.7 billion years ago, which has been metamorphosed, folded, and lifted up. This rock, called quartzite, is distinctively red, extremely hard, and resistant to erosion. During the maximum extent of the most recent glaciation, approximately 20,000 years ago, the Green Bay Lobe of the Laurentide Ice Sheet surrounded the eastern half of the hills. It deposited moraines that block each end of an ancient valley that now contains Devil’s Lake. Today, the Baraboo Hills are one of the largest forested areas in southern Wisconsin and home to Devil’s Lake State Park.
For more information, see The Ice Age Geology of Devils Lake State Park
