The area is divided into two zones: the Lakeshore Zone, managed by the U.S. National Park Service, and the Inland Buffer Zone, under mixed federal, state, and private ownership. Pictured Rocks was named for the coloured stains on the cliff faces produced by dripping groundwater containing iron and other minerals. The layers of primarily red and brown sandstone consist of Precambrian (Precambrian time), Cambrian (Cambrian Period), and Ordovician (Ordovician Period) bedrock carved into caves, arches, and fortresslike formations by the combined actions of waves and ice. The cliffs rise 50 to 200 feet (15 to 60 metres) above the shoreline. Most of the land is forested with mixed northern hardwoods, fir, spruce, jack pine, and hemlock; stands of white pine were logged to depletion in the early 1900s. Kettle lakes inland are the remains of melted glaciers. Wildlife includes white-tailed deer, black bears, snowshoe hares, grouse, and ducks and geese.