The Pictured Rocks, which tower above Lake Superior east of Munising, are likely the most photographed natural feature of the Upper Peninsula of Michigan. These scenic cliffs anchor the west end of the Pictured Rocks National Lakeshore, which extends eastward to Grand Marias. Composed of Cambrian sandstone, deposited in a broad river delta about 550 million years ago, these rocks lie in the outermost band of the Michigan Basin and are some 400 million years older than the Jurassic sediments at the Basin's center.
This morning, my wife and I took a boat tour along the base of the Pictured Rocks; conducted by a private company in cooperation with the National Park Service, the tour provided a unique and up-close view of the spectacular cliffs that were exposed by Pleistocene glaciers and are now molded by the erosive forces of Lake Superior and the region's harsh northern climate. Rock falls are a common occurrence along this majestic wall, producing recessed caves, natural arches and varied rock formations that evoke images in the eyes of human visitors (hence the name of Pictured Rocks). The boat officers and an onboard Park ranger introduced us to both the natural and the human history of this region, including the story behind many of the shipwrecks that have occurred along this storm-ridden coast.
Later in the day, we hiked out to Chapel Rock, where a pine tree grows from the top of a rock pedestal, its roots dangling between the pedestal cap and the adjacent cliff; those roots formerly ran through the soil of a rock arch before the latter collapsed into the lake. On our loop hike to and from this popular site we passed through a karst landscape which included Chapel Falls and numerous sinkholes; this topography reflects the layer of Ordovician dolomite that overlies the Permian sandstone south and east of Pictured Rocks (i.e. toward the center of the Michigan Basin). Tomorrow, we'll head westward to the Keweenaw Peninsula and thence to the Porcupine Mountains.
