Transverse dunes, linear to scalloped in shape, are believed to have formed in shallow bays along the edge of the glaciers. They are 30 or 60 feet high and are surrounded by shallow peatlands.
The original surveyors’ notes from the mid-1800s described vast peatlands, often flooded by beaver dams, and broken by narrow white pine- and red pine-capped ridges. While white pine and red pine were common dominant trees, the surveyors also made reference to aspen and jack pine.
The peatlands surrounding the transverse dunes form an intriguing, diverse habitat. At the margins of many peatlands, there is typically a zone with groundwater influx, where a narrow band of northern white-cedar grows. Cedar quickly gives way to black spruce and tamarack, sometimes followed by stunted jack pine in the center of the peatland. Tree growth is slow because of the harsh, frost prone micro-climate and low nutrient availability.
These dune complexes are extremely important for maintaining Michigan’s plant and animal diversity. Animals using the peatlands include loons, black terns, sharp-tailed grouse, yellow rails, and moose.