The Driftless Natural Division: Rare Terrain The Glaciers Missed
The large glaciers that moved across much of the world during the last Ice Age began retreating some 13,000 years ago, carving out depressions where water bodies would form and paving the way for fertile prairie soils.
Remarkably, though, the glaciers in that last Ice Age avoided about 15,000 square miles in the Midwest. Known as the driftless area, it is found in Jo Daviess County and part of Carroll County in Illinois as well as adjacent parts of Wisconsin, Minnesota and Iowa. Three sites in the Illinois Driftless Natural Division include Mississippi Palisades State Park, Apple River Canyon State Park and the Upper Mississippi River National Wildlife and Fish Refuge.
Drift refers to gravel, sand, clay and other materials that were deposited by a glacier or glacial meltwater.
“There’s no other place like this in the world,” said Duane Ambroz, Northwest Illinois District Natural Heritage Biologist for the Illinois Department of Natural Resources.
“In the driftless region you can stand next to a high cliff and note the glacier-covered land to the south and east that appears so different,” Ambroz said. “You go from this dramatic hilly variable topography to all of sudden being flat.”
A convergence of several climate zones in the driftless region sustains a variety of habitats including dry upland forests, wet wooded ravines and sand prairies. Large stands of paper birch, normally found farther north, also grow here.
The region contains seven nature preserves and 30 natural areas with forests, bluffs, prairies, rock formations and more than 1,600 miles of rivers, streams and shorelines. It harbors plant and animal species that can be found throughout Illinois as well as species only found here in the state.
The driftless area, where it can get quite hot in summer, also is the coldest place in Illinois. Indeed, on Jan. 31, 2019, the coldest temperature in state history was recorded at minus 38 degrees in Carroll County, according to the State Climate Extremes Committee.
“I think of the driftless region as fractured terrain,” Ambroz said. In a short amount of space, bluffs, ridges and valleys are dissected by streams, rivers and seeps among dolomite bedrock, which is often exposed.
Cold microclimates as well as the fractured terrain provide homes for some of the state’s rarest plants and animals.
“The state-threatened timber rattlesnake prospers well in this fractured habitat,” said Ambroz. “It has plenty of areas that can serve as hibernacula where they overwinter. Different ecosystems within the region provide a variety of thermal-regulated areas and foraging habitats rattlesnakes need.”
The state-endangered bird’s-eye primrose (below), which typically grows on Alaskan tundras, in Canada and along the northern Great Lakes region, was discovered by prominent botanist Herman Pepoon nearly a century ago in an area known as the Apple River Canyon in the state’s driftless region, according to the Illinois Natural History Survey.
In a way the glaciers shaped the canyon that harbors this plant, said Ambroz.
“The Apple River used to drain to the east, but the glaciers dammed that outlet and the water flowed back and cut a canyon through the dolomite that drained into the Mississippi River,” he explained. “The canyons have north facing cliff walls with seepages, and those cold-water seepages create a microclimate where plants like the bird’s-eye primrose can persist.”
Ambroz said those who hike the Apple River Canyon in late April and May might be able to see the blooming primrose along the cliff sides, though the population is dwindling.
Also within the canyon area is a 25-acre nature preserve where several different ecosystems meet, and more than 300 species of plants have been documented.
Another rare plant, the state-threatened cliff goldenrod, which blooms in September, can be seen in some of the rock outcrops at Mississippi Palisades State Park.
In addition, the biggest nesting population of the state-threatened cerulean warbler occurs at the Palisades, according to Ambroz.
“We’ve been doing a fair amount of woodland restoration there, and the restoration seems to be favoring the cerulean,” he said.
Restoration includes reintroducing fire to the landscape and removing invasive trees that would not normally be found in dry open woodlands.
“The driftless region in Illinois is a beautiful place to explore,” Ambroz said. “You have opportunities you won’t get anywhere else in Illinois. In spring, because many wooded areas are still in relatively good health, the region is an incredibly popular place to see wildflowers.”
It is also right along the Mississippi River where birders can watch migratory waterfowl, he said, adding plentiful hunting opportunities exist in the region as well.
“In the driftless region you can walk up rugged terrain to the top of a bluff and get fantastic views of the valley below,” Ambroz said. “You can trek up and down these bluffs to your heart’s content.”
Sheryl DeVore writes environment and nature pieces for regional and national publications and has had several books published, including “Birds of Illinois” co-authored with her husband, Steven D. Bailey.