Sandstone Arch in Pictured Rocks National Lakeshore
January 04, 2007
The photo above was taken along Lake Superior while backpacking Pictured Rocks National Lakeshore in Munising, Michigan. These cliffs consist of layers of sandstone that are comprised of Jacobsville (bottom), Munising (middle), and Au Train (top) formations. Their age is late Pre-Cambrian (approximately 680 million years ago) and early Paleozoic (543 to 248 million years ago). The colorful patterns on the rock are due to the presence of the minerals copper, manganese, and iron. In the background, you can see an arch, which formed when waves eroded caves into the sides of the cliffs. Eventually, these caves meet in the middle, forming an arch. When this arch collapses, a stack will be left behind. Photo taken on August 11, 2006.