Important factors have been identified as critical for the creation of sand dunes, including:
Within the Great Lakes basin, continental glaciers covered the landscape for over one million years, providing the major source for sand and other sediments. These glacial sediments are concentrated in two sources that provide sand for coastal dunes: rivers and coastal bluffs.
Strong winds blowing in a relatively consistent direction are a second factor critical for dune formation. For the Great Lakes, prevailing winds are typically from the southwest. As a result, the greatest concentration of large dunes is along the eastern and northern shorelines of Lake Michigan, with the largest dunes along the eastern shoreline.
Several recent studies indicate that water-level fluctuations influence dune formation, with dune growth accelerated by high water levels. One such period of intense dune growth was the Nipissing period, occurring about 4000 to 6000 years ago, when Great Lake water levels were considerably higher than today.
A final factor, vegetation, traps and stabilizes sand. Without periodic entrapment, sands cannot accumulate vertically to create high coastal dunes. Marram grass (Ammophila breviligulata), typically the first species to establish on the bare dune sands, is one of the species most adapted to survival on the dunes.