The Presque Isle River carves round potholes before flowing into Lake Superior. Porcupine Mountains Wilderness State Park, Michigan, USA. Published in "Light Travel: Photography on the Go" by Tom Demp

The Presque Isle River carves round potholes in Nonesuch Shale rock before flowing into Lake Superior. Porcupine Mountains Wilderness State Park, Michigan, USA. Published in "Light Travel: Photography on the Go" by Tom Dempsey 2009, 2010.