By William Houston III –
Perhaps one of the least discussed but most extraordinary geological features found in northern Michigan are its karst regions. Michigan’s karst regions consist of a series of unique geological features such as sink holes, caves, caverns, intermittent springs, disappearing and reappearing streams and rivers, swallow holes, earthcracks and myriad other other-worldly formations which are created where water has dissolved and eroded soluble bedrock. Unlike video features regularly seen on the Nightly News, these sink holes are not places where you need fear that your Subaru Forester will suddenly disappear. These are places of wonderment where what we see on the surface has far more to do with what’s below.
Few realize that in northern lower Michigan there is a 40 mile-wide karst band running east-west from Lake Huron near Alpena well into Otsego County. El Cajon Bay in the Alpena Township Nature Preserve in northern Alpena County has two sink holes which were formed when bedrock collapsed there after the glaciers retreated. A large sink hole in the bay is the outlet for an underground stream that flows year round. Other sink holes have been found offshore, including one near Middle Island that measures 75′ in depth.
Moving west, more sink holes are found in Presque Isle County. The Michigan Karst Conservancy (MKC) owns and manages the Stevens Twin Sinks and Bruski Sink Karst Preserves there and opens them to the general public. Like many tempting deep holes in the earth in this neck of the woods, the Bruski sink hole was used for decades as a dump site. In 1999, the MKC began cleaning out the trash there. With the help of a 75-ton crane made available by Onaway’s Moran Iron Works, the depth of the sink hole went from 85 feet to 112 feet after 27 feet of refrigerators, old cars, appliances, kitchen sinks and other debris were extracted from the site.
Also found in Presque Isle County is Mystery Valley Karst Preserve and Nature Sanctuary, managed by the MKC and the Michigan Nature Association. This “collapse valley” was created by the collapse of the surface into a labyrinth of subterranean chambers. Water beneath the surface periodically rises up from a sink hole at one end and fills the valley, a phenomenon which just recently occurred. Later this summer, the lake will drain back into the subterranean recesses from which it came, leaving behind a marshy valley.
Just north of the Montmorency/Presque Isle County line is Shoepac Lake and five “dry sinks.” While Shoepac Lake currently holds water (because its swallow holes are plugged by a big, giant cork – okay, with debris), it drained in 1976 and 1994. Rainy Lake nearby has drained at least four times since 1894. Shoepac Lake State Forest Campground is a great jumping off point with its 2.5 mile Sink Hole Pathway. There’s a stairway to the bottom of one of the sinks there that’s 199 steps, down AND up!
Seven sink hole lakes are found in the Otsego County portion of the Pigeon River Country State Forest. Several of the Pigeon River Country sink hole lakes were used as living laboratories by the DNR Fisheries Division over the years, and some are still stocked with brook and brown trout. Others “dry sinks” in Otsego County are found in the Heatherton and Johnson’s Crossing areas on private lands.
Other sinks and swallow holes are found near Trout Lake at the Firborn Quarry in the UP…and who knows where else? There are over 200 sink holes in Michigan’s lower peninsula alone. For more information about the many karst formations here in northeast Michigan, visit MKC’s excellent web site @ http://www.caves.org/conservancy/mkc/index.html, or better yet, come explore these amazing natural wonders yourself.
Editor’s Note: Bill Houston is a tireless conservation volunteer who is active in numerous local, regional and state organizations, including the Michigan Karst Conservancy.