A Glacial Erratic in the Krumwiede Forest Preserve

 By Steven Wade Veatch

The immense limestone rock (in figure 1) looks out of place, sitting on a prominent ridge in the Krumwiede Forest Reserve in Leelanau County, Michigan. That's because it is—during the Ice Age an advancing ice sheet plucked this rock from the bedrock it was moving over and absorbed it into its base. The stony mass slowly rode along, inch by inch, in the glacial ice that had grabbed it. When the climate warmed, some 12,000 years ago, the ice began to melt and recede (Hooker, 2014). Finally, the glacier ice released this boulder from its icy grip and dropped it on this spot in the Krumwiede Forest Reserve. 

Figure 1. This weathered erratic, about midway on the Ridgeline Trail, most likely came from Canada. Moving ice transported this large boulder during the Wisconsin glaciation around 12,000 years ago. Photo date October 2022 by Shelly Veatch.

Geoscientists call this rock a “glacial erratic.” These erratic rocks, whose compositions don’t match the local bedrock where they are found, range in size from cobbles to enormous boulders. Melting ice also dropped till, an unsorted and unlayered mixture of sand, gravel, and rocks of varying size and shape, that is scattered throughout the local landscape. Early settlers gathered boulders left by the glacier to build foundations for their homes.  

Figure 2. An ice sheet, about one mile thick, once covered Michigan. Image Credit: Alexandria R. Baszler. Courtesy of the Institute of Water Research at Michigan State University. https://iwr.msu.edu/kht/TrailSites/5_Glacial_Landscapes.html

The Krumwiede Reserve, part of the Leelanau Conservancy, is in the western part of Cleveland Township. A trailhead is located on Wheeler Road, south of M-22 (figure 3). The 1.6-mile Forestry Loop climbs and crosses a hill (a moraine left behind by a retreating glacier nearly 12,000 years ago) and then descends into a beautiful valley on the other side. The Forestry Loop trail then climbs back up onto the moraine to create a loop. There is evidence of glacial till scattered along the old forest road that now serves as the trail. Wheeler Road occupies a valley where a river of melting ice flowed between two high moraines (DuFresne, 2021). 

Figure 3. Tail map of the Krumwiede Forest Reserve. The property is in its natural, forested condition. Courtesy of the Leelanau Conservancy. 

To see the erratic, start on the Forestry Loop trail in the parking area (figure 3). Head south. Near a ridge (after 0.4 miles), take the narrow Ridgeline Trail footpath north (or turn left) to reach the erratic, which is situated halfway along the trail. This rustic path follows the top of the ridge for about .03 miles before reconnecting to the Forestry Loop trail. Turn left at the Forestry Loop trail to return to the parking lot.

Ice sheets from the last Ice Age left their calling cards in the form of boulders on Michigan’s landscapes. Today, these rocks engender wonder when they are encountered.

References and further reading:

DuFresne, J., 2021, The Trails of M-22: Clarkston, Michigan Trail Maps.

Hooker, T.S., 2014, The Last Ice Age and the Leelanau Peninsula: Indianapolis, Dogear Publishing.