The Driftless Area is a 24,000 sq-mile area that lies in the heart of the Upper Mississippi River basin. The Driftless Area encompasses portions of southeast Minnesota, southwest Wisconsin, northeast Iowa, and northwest Illinois. It is bounded on the north by Hastings, Minnesota, on the west by St. Charles, Minnnesota, on the east by Madison, Wisconsin, and on the south by Clinton, Iowa. Approximately 70% of the Driftless Area lies within the state of Wisconsin.
The most recent glacial period known as the Wisconsin glacier began about 110,000 years ago during the Pleistocene epoch and receded from northwest Wisconsin approximately 10,000 years ago. As glaciers advance, melt and recede, debris containing a mixture of vegetation, rock and dirt known as “drift” is usually left behind. The resulting lack of drift from this most recent glacier period led to the current name “Driftless Area.” However, thousands of years of weathering and erosion from previous glacial periods have formed a rugged landscape with steep, narrow river valleys and ridges, and forested hilltops. Elevation in the Driftless can reach approximately 457 meters above mean sea level. The high topographic relief of the Driftless Area is underlain with soluble bedrock, such as limestone and dolomite. This carbonate rock erodes as groundwater seeps or flows through conduits, forming cracks, crevices, tunnels, caves and sinkholes making this region highly vulnerable to erosion and groundwater contamination.
The Driftless Area is dotted with over 600 springs, supplying a high concentration of coldwater streams that interweave across the landscape. Over 3,600 miles of coldwater streams flow throughout the Driftless Area. The beautiful karst landscape is also blanketed with sinkholes, caves and disappearing streams.
Sinkholes are often located in rural areas amidst row crops, pastures, or wooded areas.
A few of the region’s caves have been placed on the national register of natural landmarks by the Department of Interior’s National Park Service. Coldwater Ice cave, located in Winneshiek County near Blufton, Iowa has over 17 miles of passages and extends over the border into southern Minnesota. Cave of the Mounds, near Blue Mounds in Dane County, Wisconsin is decorated with a variety of cave formations called speleotherms and contains an array of colorful mineral deposits.
There are ongoing studies to better understand disappearing streams or losing streams which can sometimes vanish into sinkholes, flow through caves, and reappear as springs miles away. These are just a few geologic examples from the Driftless Area box of jewels.
The Driftless Area is recognized as a nationally important area for biodiversity, possessing some very rare species of plants and wildlife (Chaplin et al. 2000). The Driftless also possess an unusual geological feature, which provides a home to a wide array of plants and animals. Algific (cold producing) talus (loose rock) slopes, a unique habitat type associated with sinkholes, is found only in the four-state Driftless Area and no other place in the world (U.S. Fish and Wildlife Service, 2006). Algific talus slopes are cold air slopes that typically face north. During summer, air is drawn underground from upland sinkholes, cooled as it flows over ice and is emitted through crevices or vents in the bedrock at temperatures at or above freezing (U.S. Fish and Wildlife Service, 2006). During winter this process is reversed. These slopes provide microclimates that support and enable the persistence of "glacial relicts," including globally rare terrestrial snails such as the Endangered Iowa pleistocene snail (Discus macclintocki); found in Iowa and Illinois and no where else in the world (U.S. Fish and Wildlife Service, 2006). This snail is no bigger than the button on a shirt and resides on approximately 37 algific talus slopes. The threatened Northern monkshood plant (Aconitum noveboracense) of the buttercup family also resides in these cool, moist habitats and is found only in the Driftless Area, Ohio, and New York (U.S. Fish and Wildlife Service, 1983). The Driftless Area National Wildlife Refuge was established in 1989 to protect the habitatand the remaining colonies of the Iowa Pleistocene snail and Northern monkshood (Aconitum noveboracense.)
Other relic land snails and plants have made their home here, too. The threatened Leedy’s roseroot (Sedum integrifolium), a rare cliffside flower, is found only in Southeast Minnesota and New York (U.S. Fish and Wildlife Service, 1998) and the uncommon golden saxifrage (Chrysosplenium americanum) is found only in the Driftless Area and the Yukon (U.S. Fish and Wildlife Service, 2006).