The Perched Dunes of Lake Michigan

The Sleeping Bear Dunes are not ordinary dunes. They are not the low, shifting mounds you find at most lakeshores, built from sand blown inland from a narrow beach. They are perched dunes, sitting atop glacial bluffs up to four hundred feet above the surface of Lake Michigan, and the combination of height, scale, and the quality of light off the Great Lakes makes them something genuinely unusual in the American landscape.

The story starts with the glaciers. During the last ice age, a massive lobe of glacial ice called the Lake Michigan Lobe advanced from the north, grinding rock and sediment into sand and gravel. When the ice retreated roughly twelve thousand years ago, it left behind enormous piles of that material in irregular ridges called moraines. The bluffs you see along the lakeshore here are glacial moraines, hills of compressed sediment left when the ice gave up and went back north.

Once the moraines were exposed, the second force went to work. Wind picked up sand from the lakeshore below and drove it upward against the bluff face. The sand piled up, and over thousands of years it accumulated into dunes that sit atop the moraine ridge, adding height to height. The result is a bluff that is already four hundred feet high with a dune built on top of it, giving visitors at the overlook a drop that feels more like a sea cliff than a beach.

The dunes are not static. Sand migrates across the bluff surface in the direction of the prevailing winds, and the leading edge of an advancing dune can bury living trees. The dead trunks remain standing upright in the sand for years, creating what geologists sometimes call ghost forests, stands of bleached wood protruding from the dune face like the ruins of something that was caught by surprise.

Sleeping Bear Dunes National Lakeshore was established on October twenty first, nineteen seventy, and encompasses about seventy one thousand acres along thirty five miles of Lake Michigan shoreline in Benzie and Leelanau counties. It includes forests, inland lakes, and two offshore islands in addition to the dunes themselves.