“UNDERSTANDING ANCIENT SHORELINES IN THE NATIONAL PARKS OF THE GREAT LAKES:” AN INTERPRETATIVE GUIDEBOOK DEVELOPED AS A “GEOSCIENTIST-IN-THE-PARK” AT MICHIGAN'S PICTURED ROCKS NATIONAL LAKESHORE

Relict shoreline features such as beach ridges, wave-cut bluffs, sand spits, sea caves, arches, and stacks are common in the national parklands of the Great Lakes. Understanding these landforms and the complicated sequence of related pro-glacial and post-glacial lakes is an enormous challenge, not only to the average visitor, but also to park interpreters entrusted with educating the general public. Complicating factors include the enormous scale of the features involved, along with visitors' general unfamiliarity with controlling mechanisms such as glacio-isostacy, ice-marginal retreat, and outlet incision. Many visitors also confuse large-scale Pleistocene lake level fluctuations with the much smaller variations caused by shifts in temperature, precipitation, and runoff that characterize the modern Great Lakes from year to year. Accordingly, the National Park Service, through the “Geoscientist-in-the-Park” program at Pictured Rocks National Lakeshore, commissioned the writing of an interpretative guidebook explaining the intricacies of lake-level history using language intelligible to non-scientists. The resulting report will be published in late fall 2006. Besides reviewing the mechanisms of lake level history in detail, this extensively illustrated guidebook also addresses the formation of specific shoreline features in Apostle Islands, Pictured Rocks, Sleeping Bear Dunes, and Indiana Dunes National Lakeshores, as well as Isle Royale National Park.