Geology
Portions of Iowa, Wisconsin, Minnesota and Illinois contain unusual geology. The karst region, referred to as the "Driftless Area", escaped the last glaciers leaving the Paleozoic-age bedrock subject to erosion. In addition to the curious topography of steep slopes and cliffs, there are unique habitats. Certain slopes, usually north facing, are covered with a talus layer that allows ice-cooled air to exit from underground cracks and fissures. Upland sinkholes contribute to the air flow regime and are an important component of a unique system called an algific talus slopes, meaning a cold producing rocky slope. Even on a midsummer day when the outside air temperature is 90 °F (32 °C), ground temperatures on these slopes range from 42 °F (6 °C) to about 55 °F (13 °C). Although the slopes will freeze in winter, the temperatures are moderated. These slopes remain cool throughout the year and are home to rare species of plants and animals.
Read more about this topic: Driftless Area National Wildlife Refuge