Mystery Valley Sinkhole

GPS: 45.21225, -83.73243

Mystery Valley is a unit of the Thunder Bay Karst Preserve, along with Stevens Twins Sinks and Bruski Sink. The 76-acre Mystery Valley Karst Preserve and Nature Sanctuary is located in Presque Isle County just a few miles north of the Thunder Bay Karst Preserve. It contains one of the largest karst collapse valleys in the Great Lakes region, several dramatic earth cracks and a lake that rises and falls, and sometimes disappears! Visitors to the preserve can follow two self-guided trails: Earthcrack Trail and Valley Trail. Earthcrack Trail passes a series of cracks, including two that converge into one that’s several hundred feet long and nearly 15 feet deep. Following the Valley Trail, visitors can see fossils of marine invertebrates such as brachiopods, bryzoa and crinoids that lived some 350 million to 400 million years ago. Unlike a valley carved by a river, Mystery Valley was formed by the collapse of the surface into a labyrinth of subterranean chambers created by the water erosion of rock below. Mystery Valley is 1.5 miles long, 500 yards wide at its widest point and about 150 deep, making it one of the largest known collapse valleys in the Great Lakes region.

More information is available at the Alpena Visitor Welcome Center located at 420 N. Second Ave., Alpena, Mi