Coastal dunes differ sharply from arid dunes. Due to wave action and vegetation dunes in coastal areas are unique. Some of the most common formations are dune ridges, perched, parabolic and linear dunes.


One of the most famous perched dunes on Lake Michigan rises 450 feet above the lake. It is actually a modest-sized wind-formed dune that is "perched" atop a glacial moraine. Onshore winds have lifted sand up the slope and collected it in these dunes.


Parabolic dunes are U-shaped and found only in humid coastal areas and never in arid regions. The are made when the stabilizing plant cover of a linear dune is destroyed exposing the sand to the wind. A ridge, often referred to as a blowout is then pushed into the dune beyond. The dune appears stacked. The marram grass allows the height to reach 250 to 300 feet.

Linear dunes are ridges generally parallel to the shoreline. They rarely are higher than 30 to 50 feet and the most common dune near the water.

The process of one plant community replacing another over time very visible at the dunes. This process is called succession. Great Lakes coastal dunes can be divided into four distinct areas. The basis for the division is the presence of particular plant and animal species commonly associated with certain land features. Some animals inhabit more than one area depending upon their habits or the season.

Succession in the foredune begins with the pioneer grasses. The fibrous root systems grow rapidly, binding sand together and stabilizing the dune. Plants of the foredune specially adapted to the low fertility and lack of moisture.The pitcher's thistle grows only in undisturbed dunes of the upper Great Lakes. In summer, daytime temperatures can reach as high as 120 degrees which causes may animals to burrow. At night in the cooler temperatures, Fowler's toads, the eastern hognose snake and wolf spiders come out.


The sheltered area between the foredune and the backdune is a low area called a trough or interdunal pond. The water in these depressions is the result of fluctuating lake levels. Ponds may even disappear in years of lower lake levels. In addition to dune plants and animals, interdunal ponds provide a sheltered aquatic habitat for wetland species.


A short distance away from the foredune and the trough is the forested backdune. Shade tolerant plants such as mosses and ferns live on north facing slopes. South facing slopes provide nurishment for spring wildflowers and tree seedlings.


A blowout may occur when dune grass is altered by natural or artificial means. Blowout begin when even a small amount of vegetation is removed. As the wind lifts the sand grain by grain, the grasses and trees are undercut, sometimes all the way to the hardwoods of the backdune. The grasses may soon grow back, but the trees take hundreds of years or more to return.


Sand dunes illustrate the crucial interrelationships of living things to their environment. In the late 1800's Dr. Henry Cowles, professor of biology at the University of Chicago focused on the Indiana Dunes as an outdoor laboratory. Cowles noted how dunes eveolve from sane to ridges of pioneer grasses (marram and sand reed grasses). Over time shrubs like dogwood begin to grow. This is followed by cottonwood trees. Eventually these plants are replaced until the forest reaches maturity and is known as the climax forest.