Glaciations and ruminations

The Midwest is not known for its obvious geologic charms- the highest point in Wisconsin, for example, is Timm’s Hill, which only stretches 1,951 feet above sea level. Wisconsin landscapes lack the breathtaking scenery of snow-capped mountains or the alien beauty of sculpted desert sandstones. But poking around in the Midwest’s lush woods and fields allows one to discover some interesting geologic stories that are just as interesting, if not as obvious.
Wisconsin was shaped by ice. The last glacial advances in Wisconsin (roughly 35,000-11,500 years ago), carved out lakes and deposited till throughout much of the state. The city of Madison sits on an isthmus between two glacial lakes in one of the flattest parts of the region. To the southwest is the Driftless Area, left untouched by the last rounds of ice cover and today full of winding rivers and steep hills- known for farms, trout fishing streams, and great back-roads biking. To the east is the Kettle-Moraine, a sprawling state park of potholes and hills, famous for mountain bike trails.
And, to the north of Madison is the Baraboo Range, a metamorphic quartzite string of bluffs that rise up, surprisingly, out of the surrounding flat farmlands. Devil’s Lake State Park preserves some of the ancient range for present-day enjoyment, and while the bluffs themselves are significantly older than the last ice age, remnants of glacial activity survive in the scars scratched into the remaining rocks. Hiking the bluffs gives interested geology students glimpses into various segments of Earth’s past.

The cliffs themselves, popular with rock climbers, probably formed in the Proterozoic (nearly two billion years ago) and are some of the oldest exposed rocks in Wisconsin. Carved by the pre-glacial channel of the Wisconsin River that was then dammed up by glacial moraines creating Devil’s Lake, the hard quartzite survived the scouring and scraping of the rock-filled ice that uncovered them. The glacial remnants atop the cliffs and nestled in the woods alongside them show evidence of some of the most recent geologic history of the area- perhaps lacking the grandeur of the Rockies or the Alps, but certainly an interesting juxtaposition of geologic time. The Baraboo Range and the park are also home to many effigy mounds, created by early residents of Wisconsin that have also shaped the landscape, though certainly with more purpose than the glaciers.

On Sunday, I hiked the bluffs (roughly 3.5 miles round trip) with about a dozen students. We’ll be heading out on a backpacking trip to Great Smoky Mountains National Park, and this was both a pre-trip shakedown hike to see how their gear worked and how it felt to carry a heavy pack along a trail, and also a chance to develop a sense of place. Most of the kids had been to the park before, many of them many times. But I always hope that in the preparation to travel south for a week of hiking in the Appalachians, the students start to absorb the differences in topography, terrain, and ecology. The stories that the rocks tell in North Carolina and Tennessee will be more meaningful when we understand the geologic tales told here. Much as glaciers shaped our current landscapes here, the geology of a region can shape the ecology, the terrain, and the human history of a place as well…

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Erin Parker

About Erin Parker

Erin Parker is still sometimes surprised to find herself in front of a classroom, where she teaches earth sciences to 150 boisterous students each semester in an urban public high school in Wisconsin. She also can’t imagine herself doing anything else, even on the tough days. Erin’s posts explore earth science through the lens of a public educator and advocate for a scientifically-literate world.
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