Michigan is the only state in the nation to border four of the five Great Lakes--giving it the nickname， the Great Lakes State。 This abundance of shoreline translates to a multitude of rock exposed by waves and currents。 Nearly the entire history of Earth is on display in Michigan， from 3。6-billion-year-old gneisses to potholes drilled by modern rivers。 Michigan Rocks！ guides you to 56 world-class geologic sites scattered from Isle Royale and the Upper Peninsula to Lower Michigan， including Michigan's Thumb， where carvings in sandstone are preserved at Sanilac Petroglyph State Historic Park。 Many of the well-chosen sites are two-fers; you get a good look at ancient features in a rock from time immemorial and see the damage wrought on that same rock by recent glacial ice and erosion。 The author's explanations of the geologic processes at work， along with photographs， illustrations， and informative figures and maps， make this the perfect field guide for amateur and expert geologists alike--and everyone in between！