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If you ever wondered what the Upper Midwest might have looked like before the advent of ice ages, you might travel to this interesting area of 30,000 square miles (46,000 square kilometers) in southwestern Wisconsin, southeastern Minnesota, northeastern Iowa, and northwestern Illinois.

The area is called "driftless" because there is no evidence on the ground of "drift" (glacial till) from the last few ice ages. It appears that lobes of the ice sheets advanced on all sides to surround the region, but never actually covered it. The Driftless Area is a region of massive limestone and dolomite layers, through which the rivers in the area (including the upper Mississippi River) have carved deep gorges walled with steep-sided bluffs. There are no lakes, but the uplands are a karst landscape, as the underlying limestone and dolomite is filled with caves dissolved by groundwater, some of which have collapsed as sinkholes. The region's soil is primarily loess which blew in from areas in Minnesota and the Dakotas that dried out (desertified) in proximity to the edge of the ice.

By contrast, the surrounding (glaciated) area is much flatter: the land was scoured and ground down by ice, then covered by large amounts of Canadian glacial debris. Tthe land is dotted with lakes. The original Pleistocene vegetation was worn away, and although glacial till in the soil makes it fertile, boulders make it difficult to plow.

The Driftless Area's isolation during the last few Ice Ages would have made for specialized evolutionary conditions under any circumstance ( An endangered species of snail has survived there since the Pleistocene). But in addition, special features of the Driftless Area's topography create unique microclimates that plants must adapt to:

  • North-facing bluffs that have permafrost
  • Cool breezes blowing out of caves

As a result, the region is full of plant species unique to the area. Before European settlement, the Driftless Area was covered by expanses of prairie dotted by oak groves. During the early history of the United States, the Federal govermnent prohibited farming in the area, giving the land to lead mining companies instead. Consequently, much of the Driftless area retains its pre-settlement character; however, the region contains a large number of endangered species and threatened species of plants. Over-logging has made cutting the remaining oak trees unprofitable.

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     *** = Driftless Area

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