Explore Geology
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Indiana Dunes

National Lakeshore


cover of park brochure

park geology subheading
lakeshore of Indiana Dunes
Indiana Dunes National Lakeshore, Indiana

Nature observes an easily remembered rule of thumb here:

Age is a function of distance from the lakeshore.

The closer to Lake Michigan, the younger the feature, whether sand dune, wetland, or forest. There are exceptions, to be sure, but you need not be one of them. Why not shed your age and rejuvenate yourself by approaching the water's edge from inland? This is a good way to gain an understanding of the past and of the reasons why this area was placed in the National Park System. The landscape veils many processes - some still mysterious - that have been at work for eons. And this landscape adjoins a compelling deep, one of our five Great Lakes.

Mt. BaldyPerhaps you have heard that the largest "live" dune here moves away from the lake one giant step each year?
Yes, Mt. Baldy - one look explains the name - moves a short distance away from the lake each year. Mt. Baldy, one of the largest dunes on the southern shore of Lake Michigan is 123 feet tall and is advancing inland at a rate of four- to five-feet per year. Northwest winds move Mt. Baldy inland, slowly burying the forest just south of the dune. Winds pick up sand grains from the beach and blow them inland. The sand grains roll and bounce along in a process referred to as saltation. As the wind speed increases, the sand is picked up and carried. Viewed from a distance, the sand blowing off the top of Mt. Baldy appears as wisps of smoke, thus the term "smoking dune".

Or perhaps you have heard there are fine sandy beaches here and a minimum of hustle and bustle. To test this out, just leave your car or bus and walk off by yourself. Stop, look, and listen. What is not here can be as attractive as what is here. Mystery abounds too. Carnivorous plants can be found here . . . and so can quaking bogs. Perhaps you simply want to test a rumor that grains of beach sand and dune sand are different both in texture and in size. This, too, can be verified.

Certain facts are inescapable. You are here because the dunes have caught people's attention.
Dunes are created when:

  1. a plentiful supply of sand combines with,
  2. wind blowing mostly from one direction, and
  3. a natural trap causes the wind to drop the sand.
At Indiana Dunes, sand is lifted by winds blowing off the lake. A short distance inland plants, dunes, and hills slow the wind so that it drops its cargo, creating shoreline sand dunes. On windy days you can place a stone on the beach and watch the wind create a miniature dune behind it. With patience, you can lie down and watch yourself creating one.

Mapping Glacial Advances and a Shrinking Shoreline
You can stand on a flat bit of earth on which two things have been piled:

  1. sand
  2. and rocky glacial till.
The piles of till, called "moraines", tell the story of advancing glaciers that deposited them in conveyor-belt fashion. The sand piles, called "dunes", tell the story of a lake that shrank by stages after the glaciers disappeared. The glaciers had pushed south; the lake receded northward.

vegetated dune Our major story is the dunes, but you could easily fail to recognize the inland dune ridges because they are now covered with vegetation. But beneath their vegetation and thin soil veneers lie massive sand piles just like today's beachfront dunes.

The dune ridges farthest from the lake are the oldest. They mark former shores of a once larger lake. As the lake shrank back in stages shorelines formed. Farthest inland are the Glenwood Dunes, representing the oldest of three earlier shorelines. These oldest dunes lie between moraine and lake, proving moraines the older features. You easily guess then that the Lake Border Moraine is younger than Valparaiso Moraine. It is also younger than the Tinley Moraine. The next major lake shrinkage produced the Calumet Dunes Ridge; further shrinkage formed the Tolleston Dunes. The present shoreline built the "recent" dunes. Near, the Licokiwe (Ly-co-ki-we) Trail, the Glenwood and Calumet Ridges abut as both finger out west of Route 149. The Glenwood Dunes then disappear completely, at the edge of the disturbed area - gray tint - due north of the Goodfellow Camp label. In this Industrial area modern man flattened the topography and stabilized the shorelines. Gone are old and recent dunes and the dynamics of living shores.

These disturbed areas do convey some psychological sense of the glaciers' stupendous leveling 200' high dunes effects. No "bedrock" features interrupt the general flatness at Indiana Dunes; all interruptions are deposits of sand or rock. There are no "hills" here in the sense of the Rockies or the Alleghenies, not even remnants. As you drive through road cuts you see no bedrock to create the lay of the land; only piles of the glacial till (moraines) or piles of sand (dunes). Ironically, road cuts provide the best glimpses of moraine and old dune ridge compositions. These have become mantled with soil and plants so you do not see old "sandy" dunes and moraines today. Instead you find grass- or tree--covered ridges. On these "blowouts" you find precious few plants struggling to gain a foothold. Such is the wispy life of sandy dunes.

Why Such Strange Combinations of Plants?
Professor Henry Cowles found the Indiana Dunes and Lake Michigan shoreline area a natural laboratory for developing important principles of plant succession. He arrived at the newly founded University of Chicago on a graduate fellowship in 1896 and retired as chairman of its botany department in 1934. Both he and his university students conducted extensive field research in this region. His dedication to understanding this area led to the naming of Cowles Bog in his honor.

Here at Indiana Dunes, thanks to the Ice Age, environments collided and deposited their remnants. The resulting strange combinations of plants attracted Cowles's interest. The arctic bearberry grew next to the pricklypear cactus, and southern dogwoods grew just over a dune from northern jack pines. Something else puzzled Cowles. Plant life differed dramatically from dune ridge to dune ridge. Plants growing near the lakefront were not usually found further inland, and inland forest trees could not be found on exposed dunes near the beach.

Cowles and his students observed that as plants grow on a site they change it. When these pioneer plants have changed the site sufficiently, the way is prepared for other plants. New plants can now be more successful and so they crowd out the pioneer species. Once marram grass becomes established on a dune, for example, that dune changes. Where once there was total sunlight, now there is partial shade; where once only sand, now there is the beginning of soil. As grass blades decompose they begin to build humus. Change sets in. Cowles pieced together the puzzle and formulated basic ecological concepts.

At the close of the Ice Age about 10,000 years ago, the landscape was covered with the spruce and fir forests now found in Canada. As the glaciers moved north, the climate warmed and the forests retreated. Some arctic plants, such as bearberry and jack pine, persisted while plants forced south by the Ice Age reappeared. Dry sand areas with minimal soil - like deserts - now made homes for pricklypear cactus. The red oak and sugar maple found homes in the deep soil and tumid conditions of protected moist areas. All this and more caught Professor Cowles's inquiring eye. You too can sleuth landscape features. On rolling dunes you may find jack pine or black oak, but in moist ravines the dune detective may discover, as did Henry Cowles, red oak and sugar maple. Ponds are scattered among younger dunes. Marshes are found on old lake bottoms between long dune ridges. Sphagnum bogs are found in the moraine. Bogs and marshes are dying ponds, ponds which are filling in and will eventually became meadows, then forests. For the sharp eye nature reveals its secrets, and especially so at Indiana Dunes.

Paul H. Douglas
Indiana Dunes National Lakeshore is dedicated to the late Senator Paul H. Douglas (1892-1976) in grateful recognition of his efforts to protect, preserve, and enhance this park for the use, enjoyment, and edification of present and future generations. The Paul H. Douglas Center for Environmental Education, located in the western part of the Lakeshore, provides an opportunity to acquaint and educate students in the disciplines of ecology and environmental science. The use of the center for such a purpose is a fitting tribute to a man who worked tirelessly in a decade-long effort to establish a national park area at the dunes.

park maps subheading

The General park map handed out at the visitor center is available on the park's map webpage.

For information about topographic maps, geologic maps, and geologic data sets, please see the geologic maps page.

photo album subheading

A geology photo album has not been prepared for this park.

For information on other photo collections featuring National Park geology, please see the Image Sources page.

books, videos, cds subheading

Currently, we do not have a listing for a park-specific geoscience book. The park's geology may be described in regional or state geology texts.

Please visit the Geology Books and Media webpage for additional sources such as text books, theme books, CD ROMs, and technical reports.

Parks and Plates: The Geology of Our National Parks, Monuments & Seashores.
Lillie, Robert J., 2005.
W.W. Norton and Company.
ISBN 0-393-92407-6
9" x 10.75", paperback, 550 pages, full color throughout

The spectacular geology in our national parks provides the answers to many questions about the Earth. The answers can be appreciated through plate tectonics, an exciting way to understand the ongoing natural processes that sculpt our landscape. Parks and Plates is a visual and scientific voyage of discovery!

Ordering from your National Park Cooperative Associations' bookstores helps to support programs in the parks. Please visit the bookstore locator for park books and much more.

geologic research subheading

Information about the park's research program is available on the park's research webpage.

For information about permits that are required for conducting geologic research activities in National Parks, see the Permits Information page.

The NPS maintains a searchable data base of research needs that have been identified by parks.

A bibliography of geologic references is being prepared for each park through the Geologic Resources Evaluation Program (GRE). Please see the GRE website for more information and contacts.

selected links subheading

NPS Geology and Soils Partners

NRCS logoAssociation of American State Geologists
NRCS logoGeological Society of America
NRCS logoNatural Resource Conservation Service - Soils
USGS logo U.S. Geological Survey

teacher feature subheading

Currently, we do not have a listing for any park-specific geology education programs or activities.

General information about the park's education and intrepretive programs is available on the park's education webpage.

For resources and information on teaching geology using National Park examples, see the Students & Teachers pages.
updated on 01/04/2005  I   http://www.nature.nps.gov/geology/parks/indu/index.cfm   I  Email: Webmaster
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