Northern Prairie Wildlife Research Center
Sandstone cliffs--ochre, tan, brown, sandwiched with layers of white and green--tower 50 to 200 feet above the water. Lake Superior--so vast, so blue--glistens against a cloud-streaked sky. Deep forests--emerald, black, gold--open onto small lakes and waterfalls. The image is reminiscent of a master's painting: a palette of nature's colors, shapes, and textures creates the scene that is Pictured Rocks National Lakeshore.
This place of beauty was authorized as the country's first national lakeshore in 1966 to preserve the shoreline, cliffs, beaches, and dunes, and to provide an extraordinary place for recreation and discovery. Little more than 6 miles across at its widest point, Pictured Rocks National Lakeshore hugs Lake Superior's shore for nearly 40 miles. The park consists of two zones: the Lakeshore Zone, owned and managed by the National Park Service, and the Inland Buffer Zone, a mixture of federal, state, and private ownership. Together these nearly 72,000 acres protect a portion of Lake Superior's shoreline and watershed.
Massive glaciers inched back and forth across this land for a million years, scouring and molding, while the land yielded and took on a new shape. Moving ice ground the volcanic and sedimentary rock of previous eras into rubble and slowly enlarged river valleys into the wide basins that would become the Great Lakes. The last glacier began it retreat about 10,000 years ago. Meltwater from this wasting glacier formed powerful rivers and scattered rubble onto outwash plains and into crevasses. The water scooped out basins and channels that harbor the wetlands found in the park today. Eventually, as the weight of the glacier lessened, the land rose and exposed bedrock to lake erosion. It was this onslaught by the lake--centuries of battering waves and ice--that carved the bedrock into young cliffs. Relentlessly the water continues to pound and sculpt the cliffs, eroding them inland while enlarging the lake.
Solid or liquid, the force of the water profoundly altered the landscape and created the largest freshwater lake system in the world. It is hard to visualize that power, until you examine the evidence. You will soon recognize the clues. Look at the water-sculpted arches and profiles of the cliffs. Observe the inland lakes formed when glacial outwash buried enormous blocks of ice. The ice melted over time, forming depressions that filled with water and became kettle lakes. Examine the stones along Twelvemile Beach--horn coral from an ancient sea, polished granite and quartz rounded like eggs, and disk-shaped fragments of the Jacobsville sandstone.
The name "pictured rocks" comes from the streaks of mineral stain that decorate the face of the sculpted cliffs. The ramparts of the cliffs are composed of 500-million-year-old Cambrian sandstone of the Munising Formation. The Munising Formation makes up much of the angled slopes and formations, such as Miner's Castle. Closest to lake level is the Jacobsville Formation, a late-Precambrian mottled red sandstone that is the oldest exposed rock in the park. Covering all is the 400 million-year-old Ordovician Au Train Formation, a harder limy sandstone that serves as a capstone and protects the underlying sandstone from rapid erosion. The streaks on the cliffs occur when groundwater oozes out of cracks. The dropping water contains iron, manganese, limonite, copper, and other minerals that leave behind a colorful stain as water trickles down the cliff face.