How the Dunes Were Created

The beach at Whitefish Dunes State Park appears calm and unchanging. But in reality, the beach is always a work in progress. It is constantly being constructed and re shaped by strong forces of nature.

• The wind is the major sculptor of the beach. When it blows across the smooth surface of Lake Michigan, there’s little to hinder its momentum. It hits the shore with a fury, picking up grains of sand and pushing them inland. As the wind velocity slows over land, sand drops to the earth, and in time, a pile is formed.
• Gradually, the pile grows into a tall sand dune. Slowly wind blows sand grains up the gently sloping upwind face of the dunes. Once cresting the top, the wind moves down the steeply sloping backside. This creates momentum for the wind to pick up sand grains and continue inland.
• The wind speed slows once again as it heads inland. Sand drops to earth beginning another sand dune and the process starts over.
• The younger dunes on the shore block the wind and allow plants to establish on the older dunes. These plants live and die over hundreds of years, creating real soil, yet the soil remains sandy. Over time the grasses and shrubs make way for the forest.
  

If you’ve ever felt the sting of sand pelting your skin on a windy day at the beach, it’s because you’ve been caught in the middle of this sculpting process.

Sand Moves in Many Ways

Sand on the beach ranges in size from pebbles to very fine sand grains. Wind-formed dunes consist of medium to fine sand grains. As the wind blows, the majority of the sand is moved by a process called saltation. This is a bouncing of the grains across the beach. Coarse sand is too large to be moved by this process and is moved short distances by “surface creep,” rolling the grains along the surface. Fine silt particles are carried in suspension by the wind for long distances.

Sand Stabilizers

Between the edge of the water and the beginning of the dunes, dry sand is constantly in motion--dancing, shifting and floating. This makes the beach a treacherous place for plants to take root. One kind of plant that does live here is marram grass. It spreads its tuberous roots just under the surface of the sand, and forms an underground web that helps hold the sand in place.

Though marram grass stabilizes the sand for its own survival, an inadvertent side effect is that it makes it possible for other kinds of vegetation to begin to take hold. Other plants take advantage of the increased stability of the sand surface and start to colonize areas the marram grass helped make safe.