The Driftless Area
Backstory and Context
When driving on Interstate 90, either from the east or west, as drivers near the Wisconsin-Minnesota border they may begin to notice quite a change in the landscape. At the crest of a hill near Tomah, WI, the horizon ahead displays tall hills that layer themselves one after the other. On the other side, the road descending a hill outside of Nodine, MN travels through steep valleys, hills, and dense forestry with a glimpse of the Mississippi River that lies at the bottom. These new roadside attractions are quite the contrast from the fields and farmland that dominate the rest of the journey on I-90 - and the features of this area are millions of years older, too.
The Driftless Area that encompasses the intersection of Wisconsin, Minnesota, Iowa, and Illinois is a geologically unique region of the United States that has an unusual history as the cause of its numerous bluffs, valleys, hills, and rivers. Over a million years ago, an ice sheet named the Des Moines lobe traveled southward into and over Iowa, carving a border on the western edge of Wisconsin while smoothing the terrain in its path. This ice sheet left behind glacial drift and till, sediments that provides evidence of a glacier moving over the area in the region’s history. Then, a half-million years ago, the Green Bay lobe on the eastern side of Wisconsin traveled southwestward to almost meet the Des Moines lobe in western Illinois. In the following thousands of years, these glaciers shifted and retreated before finally meeting their end a little over ten-thousand years ago, leaving only glacier drift as evidence of their existence. In the millions of years that these glaciers moved and traveled around the Upper Midwest of the United States, the Driftless Area completely eluded all of them.
The reason for this has several possible explanations. Some geologists theorize that the Mississippi River was an entrenched ice stream that heavily influenced the movement of ice sheets, or lack thereof, in the Driftless Area. Other theories include that the Driftless Area is a result of the area’s topography that existed before glacial periods, including that the bedrock of the region is at a higher elevation than the surrounding area and that the natural presence of limestone and sandstone helped prevent the spread of ice. There are also ideas about the high elevation of bedrock in Northern Wisconsin that may have protected the Driftless Area, as well as an influence from the basins of what would become Lake Superior and Lake Michigan.
Whatever the definitive cause of the Driftless Area, the region maintains the ancient evidence of glacial evasion in the cliffs of the bluffs that line up against the Minnesota and Wisconsin borders and the Mississippi River that stretches wide between the two states. While the majority of the Driftless Area lies within Wisconsin, the metropolitan areas that exist in the region include La Crosse, WI, Winona, MN, and Dubuque, IA. Each of these cities feature several universities, healthcare centers, manufacturing companies, and cultural products centered on the uniqueness of this region. The area also thrives on a tourism market, from curious travelers to professional scientists, who are drawn to the bluffs, rivers, and settlement histories of the individual cities. The Driftless Area is not only without equal in the United States - there is no other region on the entire planet with the geological history and features that exist in this corner of the Midwest, making this exceptional area truly one-of-a-kind.
"Des Moines Lobe." Iowa Geological Survey. July 11, 2017. https://www.iihr.uiowa.edu/igs/des-moines-lobe/.
Hobbs, H., 1999. Origin of the Driftless Area by subglacial drainage—a new hypothesis. In: Mickelson, D.M., Attig, J.W. (Eds.), Glacial Processes Past and Present, pp. 93–102. Geological Society of America Special Paper 337.
Jefferson, Anne. "The Driftless Area: Fewer Glaciers but More Topography than the Rest of Minnesota." Highly Allochthonous. November 30, 2010. http://all-geo.org/highlyallochthonous/2010/11/the-driftless-area-fewer-glaciers-but-more-topography-than-the-rest-of-minnesota/.
Knoot, T.g., M.e. Shea, L.a. Schulte, J.c. Tyndall, M.d. Nelson, C.h. Perry, and B.j. Palik. "Forest Change in the Driftless Area of the Midwest: From a Preferred to Undesirable Future." Forest Ecology and Management 341 (January 30, 2015): 110-20. doi:10.1016/j.foreco.2014.12.013.
"Marginal Ridge of the Green Bay Lobe." Wisconsin Geological Natural History Survey. https://wgnhs.uwex.edu/wisconsin-geology/major-landscape-features/green-bay-lobe/.