The Baraboo Range
The Baraboo Range consists of highly eroded precambrian metamorphic rock; and is about 25 miles long and varies from 5 to 10 miles in width.
The range is an example of a buried mountain range exposed through erosion, to once again undergo the forces of surface erosion. The rocks are as much as 1.6 billion years old, among the oldest exposed rocks in North America consisting mainly of pink Baraboo quartzite and red rhyolite.
The Wisconsin River, previously travelling in a north to south direction, turns to the east behind it before making its turn to the west towards the Upper Mississippi River. The eastern end of the range was glaciated during the Wisconsinian glaciation, while the western half was not, and consequently, marks the eastern boundary of Wisconsin's Driftless Area.