What the Heck is a Glacial Drumlin, Anyway?

Q: Just exactly what is a “glacial drumlin,” and where can I see one in the wild?

A: A drumlin is a geological formation left behind by the ancient glaciers, and finding them along the Glacial Drumlin State Trail is pretty easy!

Until about ten thousand years ago, much of Wisconsin was covered by vast sheets of ice, slowly moving across the landscape. As these glaciers moved, they pushed rock and soil around, pulverized large rocks into small ones, carved small valleys, and ground hills down to nubs.

Drumlins are often the highest point around, so you’ll sometimes see a cell-phone or data tower installed on the top of the hill.

When the glaciers melted away, they left behind the relatively flat landscape we see today. But they also left some mysteries and clues …

Drumlins are rounded, elongated hills, shaped like half an egg. They are made of the jumbled rocks, gravel, and soil left behind by moving glaciers. They are often covered with trees, because their soil is too rocky and steep for plowing and farming.

In fact, as you hike or bike the Trail, be on the lookout for glacial drumlins. If you see a rounded hill covered with forest, there’s a good chance it’s a drumlin, formed by the glaciers.

Drumlins are kind of like animal tracks in the snow: by looking at which way their footprints point, you can tell which way the critter went. And by looking at which way a drumlin points, you can tell which way the glacier was moving: the higher, larger end of the drumlin indicates the direction from which the glacier came, while the lower tapered end of the drumlin shows where the glacier went.

One of the largest portions of the last Wisconsin glacier was in the broad shallow valley that would later become Lake Michigan. As the glacier slowly spilled up and out of that valley, it spread out in all directions. So, the drumlins left behind near the eastern end of the Glacial Drumlin Trail near Waukesha are oriented east-to-west. On the other end of the Trail, near Cottage Grove, that portion of the glacier left drumlins which point north-to-south.

Where can I see a Glacial Drumlin?

Fortunately, finding a drumlin is quite easy, and you can see many right from the Trail!

1. At the trailhead in Cottage Grove, there is a drumlin just southeast of the parking lot. There is now a large assisted living residence built on top of it. In fact, almost as soon as you head out, the Trail swings in a gentle “S” curve to skirt around the northern end of the drumlin.

2. About 2.1 miles from the Cottage Grove trailhead, the Trail crosses Ridge Road. This road is built right along the top of a long narrow glacial drumlin which runs north-to-south.

3. At about Mile 6.3, just west of Deerfield, the Trail crosses North Nelson Street. Stop here and look to the north. Just to the right of the large farm and silos as a large wooded drumlin.

4. From the Trail parking area in Deerfield, look to the southeast. Much of the eastern half of the small village of Deerfield is built on four or five tall glacial drumlins.

5. One mile east of Helenville, the Trail crosses Duck Creek Road; turn south here for one of the Trail’s best picnic spots, Pohlmann County Park. Just southwest of the intersection of Duck Creek Road and US Hwy 18, visible from the Park, is a heavily wooded glacial drumlin.

6. The Trail crosses Pioneer Drive about 1.7 miles west of Sullivan. From here, look to the northeast about a half mile, for a forested glacial drumlin with a communications tower on top of it.

7. Just west of Sunset Park near Waukesha, the Trail makes a long sweeping “S” turn. Look to the southwest about a quarter mile to see a neighborhood of homes built atop a grouping of glacial drumlins oriented east-west.

The glaciers and other natural forces have made the landscape of Wisconsin the way it is today, and the observant eye can begin to see some of the mysteries and clues left behind …

Enjoy your visit!

You can learn more about glacial drumlins here:

Drumlins, From Wikipedia, the free encyclopedia

Glacier Landforms: Drumlins

Drumlins, The University of Sheffield

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