Geology of Sleeping Bear Dunes National Lakeshore, Michigan

Geodiversity is the full variety of a park's rocks, minerals, sediments, fossils, landforms, soils and the processes that shape them. This summary comes from the NPS Geodiversity Atlas (Geologic Resources Inventory), which supports education, geoconservation and management of a park's living and nonliving resources together.

Pyramid Point Overlook. Photo: NPS.

The park

Sleeping Bear Dunes National Lakeshore lies along the northeastern shore of Lake Michigan, in Benzie and Leelanau Counties, Michigan. Established on October 21, 1970, it covers nearly 28,817 hectares (71,210 acres) in four mainland units and North and South Manitou Islands, with about 105 km (65 miles) of Lake Michigan shoreline and many inland lakes and streams.

It was designated for outstanding natural features — rivers, sandy beaches, beech–maple forests, clear lakes, lakeshore bluffs and its namesake sand dunes, which rise 140 m (460 ft) above the lake — and it also holds an island lighthouse, lifesaving stations, coastal villages and farm landscapes.

A landscape built by glaciers

The park's geology is young Quaternary sediment in a region shaped by Pleistocene glaciations.

• Pyramid Point, Sleeping Bear Plateau and Empire Bluffs are glacial moraines — ridges of loose debris left as glaciers retreated — which steered later ice into Good Harbor and the area's lakes.
• Thousands of years of waves have cut the moraines back into headland bluffs, including the steep sand and gravel faces of Empire Bluffs, Sleeping Bear Bluffs and Pyramid Point.
• The famous dunes sit perched atop the high moraines. They formed as wind and water reworked the moraine deposits: as the moraines eroded, lighter sand was carried up on top of them while heavier stones fell to the beach — a natural sifting that, over long periods, built the dunes.

The park belongs to the Central Lowland physiographic province, sharing its geologic history with a region far beyond its boundaries.

Dune Point Trail. Photo: NPS.

Maps, reports and more

The park's digital geologic map, report, posters and scoping summary are on the NPS DataStore, as is its completed Soil Resources Inventory. More from the park: glaciers and glacial features, sand dunes, beaches and coasts and shorelines.

Sources

Based on "NPS Geodiversity Atlas—Sleeping Bear Dunes National Lakeshore, Michigan," National Park Service; a work of the United States government in the public domain.