Mountains of sand
You may think of the Indiana Dunes as permanent mountains of sand overlooking the beach along Lake Michigan. Yet their appearance of permanence is an illusion. The dunescape is always changing — altered by the forces of nature and by the hand of man.
A ballet of wind, water and sand created the ancient dunes and continues to shape the Indiana Dunes today. Winter storms — with their northwest winds and water currents — carry sand from the lake bottom to the shore. The winds of spring and summer carry the sand inland where it piles up grain-by-grain.Dune builders
Dunes grow only if plants anchor the sand and it does not blow away. The dunescape would be very different were it not for marram grass. This grass survives in the hostile, nutrient poor foredunes of the Dunes. Marram grass roots may push twenty-feet under the sand in search of moisture and the grass will grow up through sand that buries it.
This grass sends out runners called rhizomes from which new plants spring. This mat of roots and shoots stabilizes a mass of sand. Other plants, grasses, shrubs and trees grow and build the Dunes — little bluestem and sand reed grasses, sand cherry bushes, cottonwood trees.Blowouts
The same fierce winter storms and high water level that bring sand to nourish the Dunes sometimes tear away part of the protective vegetation. The wind and waves sometimes cut through a dune like a knife. The dune may collapse or erode. Without a stabilized dune to block the force of wind and water, a huge natural amphitheater called a “blowout” may form.
The Indiana Dunes State Park is within the national lakeshore boundaries. Trail nine in the state park leads to the spectacular Beach House Blowout. As you stand atop the blowout, look across its quarter-mile bowl and see Lake Michigan. A small dune has grown in the mouth of the blowout and blocks the lake's fury. Marram and little bluestem grasses carpet the leeward slopes of this dune and the blowout itself.
The steep cliffs of Beach House Blowout are still eroding. The grasses are losing the struggle to tame the blowout and the mat of roots and runners are visible. The Furnessville Blowout and Big Blowout are also features of the state park. Grasses, shrubs and trees have tamed the Big Blowout, the largest in the national lakeshore. This blowout may become a forest or a vegetated dunes through the natural succession of plant communities.Wandering dunes
Other dunes, stripped of their vegetation, wander inland burying everything in their path. These wandering dunes have buried forests, summer cottages and roads. No retaining wall or fence can stop a wandering dune that moves as much as 60 feet a year. It is as if a pyramid were grinding inland. A wandering dune may climb another dune and add that dune's bulk to its own.
Mount Baldy in the national lakeshore is the largest wandering dune in the region. From the parking lot, look at the giant dune as it swallows up the forest at its feet. When a wandering dune buries a forest and moves on, it may leave a ghost forest of desiccated trees in its wake. Wandering dunes stop when vegetation has stabilized or slowed them or when the wind and storms have carried away the unanchored sand.Human impacts
People alter the Indiana Dunes. Their beauty attracts about two million visitors a year. Some visitors have eroded dunes or caused blowouts by wandering off the established trails.
The Indiana Dunes is a wilderness in an urban setting surrounded by communities, industry and highways. The population of Lake, Porter and LaPorte Counties grew from about 100,000 in 1900 to about 800,000 in 1990. This growth and development have permanently altered or destroyed large portions of the Dunes.Dunes destroyed
The Central Dunes, for example, were the most scenic dunes and the site of the highest biodiversity in what is now the national lakeshore. The construction of a power plant, a steel mill and a port destroyed the Central Dunes. Yet the national lakeshore still preserves and protects vast expanses of beach and dune within its borders.
Other development threatens the Dunes. Ports, breakwaters, piers, marinas and other structures disrupt the water currents that carry sand to the beaches in winter. Entire beaches have eroded away and some communities have trucked in sand to replenish their beaches. Lake Michigan’s fury has threatened homes along the lakefront.Dunes reborn
The natural forces of wind and water, the succession of plant communities and the impact of development and visitors interact to change the dunescape. Beaches erode. New dunes are born and others die. Blowouts and wandering dunes stabilize while new ones develop. The Indiana Dunes seem everlasting, but the dance of wind, water and sand transforms the dunescape.
Copyright Bud Polk, 1997
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