Hike & Read: Rock Picker’s Guide

HikeGeologic change generally happens slowly, but that doesn’t mean it’s necessarily dull. Your geologic contemplation space is an open field in the Johnston Preserve, about 20 minutes north of Harbor Springs. Wander two-tracks at the old farmstead, making your way to the highest point. You are standing on a 600-foot-deep pile of glacial till, what was once part of a large island about 11,000 years ago, when the area was deluged by melting glacial waters. Geologists named that ancient island Brutus Island, and the body of surrounding water Lake Algonquin, which rose about 120 feet higher than today’s Lake Michigan.

Look west, and on a clear day you’ll see the Beaver Island Archipelago floating about 20 miles off shore. In Lake Algonquin times, the only land visible would have been a tiny high point on Beaver. But our lakes are dynamic things – geologically speaking. About 10,000 years ago, the water level dropped about 360 feet – geologists named the low lake Lake Chippewa. In low water, the Beaver Island Archipelago became part of the mainland, and the Mackinac Straits shrank to a river – scuba divers have found pottery shards from earlier man along the ancient river shore.

Get there: From Harbor Springs, follow State Road about 9.5 miles to Robinson Road. Left on Robinson 4 miles to Church Road. Right on Church 1/2 mile; look for preserve signs on the right.

Be a Savvy Picker
The human mind is too feeble to truly grasp the force of glaciers that rose more than a mile high and pulverized mountains as they pushed in a frosty ooze over the earth. But what we can appreciate is the fantastic array of rocks – many from hundreds of miles away – that glaciers dumped in our Great Lakes. Lake Michigan Rock Picker’s Guide will help you move beyond, “Whoa, cool rock,” to “Look Honey, it’s feldspar.” Intellect can be sexy. In bookstores or author Kevin Gauthier’s shop, Korner Gem. 13031 S. Fisherman Cove, Traverse City. 231-929-9175.

Jeff Smith is editor of Traverse. [email protected]

Note: This article was first published in September 2006 and was updated for the web February 2008.

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