A dune is a rounded hill of drifted sand. Most dunes are found in dry places like a desert and are often barren mounds. Great Lakes sand dunes, however, are home to many forms of life along the shores of an enormous lake. The dunes support many microclimates of plants and animals not found anywhere else in the world.


Dunes are been on the Great Lakes shorelines for thousands of years. The materials of the sand came from hard bedrock which existed for millions of years. Some could even be billions of years old.


A million years of ice ages accelerated the erosion and transported it to the Great Lakes on sheets of ice. When the glaciers began to melt over 10,000 years ago, they washed enormouns amounts of debris through glacial lakes and down rivers. The glaciers left tremendous amounts of water and raw material that tltimately eroded further into the small grains we call sand.


The very old sand served as the main ingredient for the dunes. Quartz became the dominant sand mineral along with small parts of feldspar, magnetite, garnet, calcite, ilmenite, hornblende, and epidote. The Indiana dunes have been here for 3,000 to 4,000 years.


Many seashores and Great Lakes shorelines have the basic ingredients for dune formation (sand, vegetation and geography) but lack one essential factor--a consistent onshore wind. These onshore winds initiate lake currents and move dry sand inland. Prevailing winds have concentrated dunes on the south and east shore of Lake Michigan.


To become a dune of any size, sand which has been blown by the wind must be caught and accumulate. Sand will collect around objects such as driftwood and will easily bury exposed objects, only to move on with the next gust of wind. Without plant life such as the dune-building marram grass, dunes will not grow in height and breadth.