The following information should be read before, during, and after our field trip. This
information will give you a better insight to ecological succession and dune formation. There are
three small articles that focus on the history of Illinois State Beach Park, interactions of biology
and geology, and the geology at Illinois State Beach Park. The following are three articles about
the history and geology of the area.
Into The Wild
Larson, Chris (August 2001). Illinois State Beach Park: Into the Wild.
Chicago Wilderness, volume 2.
The park, located near the Wisconsin border in Zion and Winthrop Harbor, was established in the early 1950s; it
now includes over 4,100 acres split into a Southern Unit and a smaller Northern Unit. The Southern Unit is home to
a large beach, 244 camp sites, several miles of hiking trails, and an 800-acre Nature Preserve.
The dunes and ridges that cut across the park are the result of receding lake levels over the past 8,000 years. As
the waters dropped, the wind blew the newly exposed beaches into dunes. (This is the same process that created
the taller Indiana dunes; Illinois dunes rarely grew to more than 10 feet high because the prevailing winds blow
towards the lake.) Over time, as the lake level continued to drop, new dunes were created while the older dunes
were colonized by plants. The result today is long lines of sandy, oak savanna or prairie ridges, interspersed with
Many ecological niches are found in the park. On the beach and foredunes, the harsh wind and blowing sand limit
plant life to the hardiest species like the sea rocket, bearberry, and the Waukegan or horizontal juniper, which grows
just a few inches off the ground.
Not far beyond the dunes is the sand prairie. In winter, depending on snow cover, you can see stalks of Indian grass,
little bluestem, and even prickly pear cactus.
Farther inland are the oak savannas, which occupy much of the higher ground, while the wetlands in the swales host
Kalm's St. Johnswort, sundew, and a wide variety of orchids, including many that are endangered. The Dead River
is a sluggish stream that splits the Nature Preserve into public and off-limits areas. The river is called "dead"
because, much of the year, the river's outlet into the lake is blocked by a sandbar. After heavy rains or snowmelt, the
river rises and breaks through the bar, thus draining the surrounding wetlands. The river is actually quite healthy and
birds are attracted to its wetland plants.
Spring and fall are the best time to see birds, when they migrate through the park in tremendous numbers. Red-tailed
hawks are common throughout the winter, and great horned owls are often heard at night. Many deer, red fox, mink
and beaver live in the park; visitors can catch occasional glimpses of gray fox as well.
Illinois State Beach Park
Pavlovic, Noel (2008). Illinois State Beach Park. Retrieved
June 2008 from , Web site:
Although many Chicagoans think of dunes as north or southeast of the city, Chicago itself was
built upon dunes. The sand dunes formed after the retreat of the Wisconsin glacier, when sand
was abundant and various stages of Lake Chicago, the ancestral Lake Michigan, were created.
Dunes formed when lake levels were low and eroded when lake levels were high. Dunes at
Illinois Beach State Park are less than 5,000 years old, low in height, and often form linear
alternating dunes and wetland depressions called swales.
Dunes in the Chicago region played an important role in the history of ecology. In the late 1890s,
Henry Chandler Cowles discovered the interaction between the geological processes and
vegetation development that produced dunes. He studied the process of dune succession whereby
a series of different plant communities developed over time as dunes built up and became
stabilized. For instance, foredunes, the first low dunes to develop above the beach, are often
stabilized and increase in height as beach grass or cottonwood colonizes the sand. The ability of
beach grass shoots to grow upward and rhizomes to grow sideways in lines allows the capture of
sand and the increase in dune elevation. Likewise, cottonwood can grow upward as it is buried
because new roots can sprout from its buried trunk. After the foredune stabilizes, these pioneer
plants increase the richness of the soil by depositing and trapping litter. In the early 1950s, Jerry
Olson demonstrated that most of the soil development occurs in the first 2,000 years of the dune.
Soil enrichment and disturbances then promote the invasion of little bluestem grass and plants.
Through the process of succession, much of the older and higher dunes are covered with prairie,
oak savanna, woodland, or forest. Dune formation today is limited to where there is abundant
sand supply that has not been interrupted by docks, harbors, or fill that blocks the sand
movement along the lake and where human disturbance does not hinder the growth of
Protecting the Nation’s First State Dedicated Nature Preserve
Illinois Dunesland Preservation Society (2008). Protecting the
Nation's First State Dedicated Nature Preserve. Retrieved June
2008 from, Web site: http://www.illinoisdunesland.org/
To walk along a Lake Michigan beach is to stroll through an open-air museum. And this
museum has works of art dating back over two billion years. These surf-rounded pebbles and
cobbles were transported from tens to hundreds of miles to the north by the latest glacier, then
sorted and smoothed by the agitated water of the lake. Among the rock types show here are
Archean and Proterozoic igneous rocks from northern Wisconsin and the Canadian Shield
(basalt, gabbro, and granite) and Paleozoic sedimentary rocks from eastern Wisconsin and
Michigan's Upper Peninsula (sandstone and dolostone). From Lake Michigan’s extensive
formation of rising and falling waters, much of the rock found in this area consists of limestone.
One of the remarkable features of this area is that beach, dune, marsh, calcareous swale, and
sandy prairie specimens are all within a few hundred yards of each other. Glaciers created an
ancient lake called Lake Chicago by geologists; now known as Lake Michigan. As the ice melted
and the water drained, new channels were opened up and stood at that level for hundreds of
years, forming beach ridges. The geomorphology of Illinois Beach State Park is a dune swale; it
is the only contiguous dune swale left in the Great Lakes, the last remaining Lake Michigan
beach ridge in Illinois. The sandy ridges are crowned by black oak forests with an open, savanna-
like appearance, and several kinds of fragrant pines thrive in the southern area.
*See References for publication information
The following is the list of sand dune succession:
Lower beach – near water’s edge.
Middle beach – usually dry, some plant growth.
Upper beach – conditions less severe, flora richer.
Foredune community – sand binding grasses, beetles, and spiders.
Cottonwood community – first tree bearing zone.
Black Oak community – second tree bearing zone.
Red – White, Oak – Hickory community – climax growing in deep, humus rich soil.
(College of Lake County, 2008)
Some other helpful vocab:
Succession - orderly change from one community type to another community type.
Primary succession - changes of community type where there has been no life before.
Secondary succession - the changes that take place after some sort of disturbance to an
Climax communities - stable communities or there is a change in the climate.
Review of Sand dune Systems:
Conditions needed –
o Supply of sand
o On- shore winds
o Colonizing plants
Processes that happen-
o Sand blown inwards
o Sand trapped by plants
o Plant growth help dunes grow
o System grows seaward, oldest dunes are furthest away from water
o Older dunes stop growing