The Land Preview

You are now standing in Midewin National Tallgrass Prairie. It is the first National Tallgrass Prairie in the United States. Midewin is the largest contiguous piece of land in northeastern Illinois to be restored to prairie. Midewin is approximately 4 miles long and 8 miles wide, 32 square miles.

Before European settlement, northeastern Illinois was last occupied by the Potawatomi Indians. Various groups of Native Americans have inhabited northeastern Illinois for 10,000 years, … 4,000 years before the prairie arrived. Because of the long occupation of the Potawatomi nation on the landscape, it was thought appropriate, with the approval of Potawatomie tribe, to give the first National Tallgrass Prairie a Potawatomi name.

Midewin is the name of the Grand Medicine Society of the Anishinaabe, a group of native American tribes that inhabited the Great Lakes region of North America, and includes the Potawatomi people who were historic residents of this part of Illinois. As a society of healers and leaders, the Midewin keep the greater Anishinaabe society in balance. These indigenous values are reflected in the current use of the name and represent healing the natural world and providing balance to our urban, technology-filled lives.

It took an act of congress to make Midewin a reality. In February of 1996 the Illinois Land Conservation Act was signed. 19,161 acres of surplus federal lands that were once the Joliet Army Ammunition Plant were now part of the United States Forest Service.

The Illinois Land Conservation Act took a tired expanse of land with the goal of restoring it to magnificent prairie.. The land that served a nation for sixty years as an arsenal and had fed a country for 80 years before that would be brought back to its natural state, prairie. Restoring Midewin prairie is no easy task and will be ongoing.

Midewin staff, partners and volunteers strive to fulfill the primary purposes of Midewin as stated in the Illinois Land Conservation Act:

· to conserve & enhance native wildlife and plants

· to conduct education and research

· the continuation of agricultural uses where appropriate

· to be used for recreation

In 1820, Illinois was covered in 22 million acres of tallgrass prairie. This encompassed the upper 2/3 of the state. The remaining 14 million acres were the forested southern 1/3 of the state. This resulted in one of the nick names for the state of Illinois, “the prairie state”. Some of the first Europeans to arrive in Illinois were French explorers. When they looked out on this vast expanse of grass they said the French word “praierie”, meaning meadow. The name and pronunciation have stuck with only the spelling changing slightly.

Settlers arriving in Illinois believed prairie soil to be poor because no trees grew here. They soon discovered how wrong they were. The plant matter above ground and the extensive roots below ground add important nutrients to the soil especially after a fire.

The invention of the steel plow in 1837 allowed farmers to break through the long prairie roots and cultivate this rich loamy soil. By 1900, most Illinois prairie had disappeared, with only remnants remaining. What was once prairie is now the bread basket of the world, known for its corn, soybeans, and wheat production.

While most prairie areas in the United States receive lower than average amounts of rainfall, Illinois prairie receives enough rainfall to support trees. In the past, frequent fire eliminated trees before they became established. Modern society puts out fires that would naturally occur in Illinois to protect homes, businesses, and crops. Today Midewin still uses fire in a prescribed or controlled manner to help reduce trees and other woody species that were once burned by large prairie fires.

Today, tallgrass prairie ecosystem is more rare than that of the rain forest. Only one tenth of 1% of the vast Illinois prairie remains. You can visualize this by imagining that your whole body is the state of Illinois. The toenail of your little toe is all that would remain of tallgrass prairie in a state known as “The Prairie State”.

Native tallgrass prairie is one the rarest and most endangered ecosystems in the world. Less than 1% of original tallgrass prairie still exists. A typical tallgrass prairie is a mixture of grasses and forbs (flowers). Grasses make up the bulk of plants growing on a prairie while forbs contribute to the diversity. There are six types of prairie in Illinois: black soil, sand, gravel, dolomite, hill prairie, and shrub prairie.

All prairie plants have one thing in common, deep roots. It takes the average prairie plant two to three years to bloom from seed. Plants put great energy into growing roots, often before producing flowers and height. Prairie plants are akin to icebergs. While the plants on the surface appear quite large, 70% of the average prairie plant is found below ground. The eloquence of this root adaptation allows prairie plants to withstand extreme environmental conditions occurring on prairies.

Deep roots increase plant survival of harsh environmental conditions. Extensive root systems, 16 feet or more, create a vast underground storage system for water and food. When nature brings extreme high and low temperatures, drought or flooding, excessive grazing by animals and insects, and fire burning all above ground plant growth, prairie still rebounds. The adaptation of extensive roots provides food and water prairie plants need to survive and thrive.

Deep rooted prairie plants provide important ecosystem services for us. Prairie plants help provide better rainfall and runoff infiltration of water into soil. One acre of established prairie can produce 24,000 lbs. of roots which can absorb 9 inches of rainfall per hour before runoff occurs. Intense rain episodes can be eased by prairie roots. An acre of established prairie will intercept as much as 3 tons of water during a one inch per hour rain event. Underground aquifers can be refilled. Roots open pores into soil and allow water to percolate deeply to fill aquifers and reduce standing water. Prairies and their deep roots deserve a place in our landscape for the beauty as well as the vital services they perform.

The woodland surrounding you consists of black locust trees. Planting of black locust trees was encouraged in the upper Midwest in the early 1900’s to prevent soil erosion. By 1930, the Farm Bureau bulletin #1628 was giving farmers detailed instructions on planting and growing black locust trees. Farmers had great concerns, in this Dust Bowl era of 1930, about losing their soil to the wind. Black locust trees were recommended as one possible solution to soil erosion. They have an extensive root system that spreads with shallow rhizomes to form groves of trees that keep soil in place. The farmer that planted the original black locust trees here was following recommendations from the Soil Conservation Service.

Black locust trees are fast growing medium sized trees. They can reach 25 feet by the end of their second year and top out at around 80 feet in height. The wood of these trees is very dense and slow to rot. This denseness results in a slow burning wood, a great wood choice for keeping a farmhouse warm in the cold months. The strength and durability in and out of soil also make black locust trees a good choice for very strong fence posts, stakes, and poles. Thus, it was a valuable tree to a farmer in the 1900’s.

The leaves of this tree are distinctive, possessing a light and airy feeling. The leaves are 12 inches long with 7 to 21 oval leaflets that grow opposite one another. At night the leaflets fold up and droop. In the spring, beautiful trailing white flowers similar in appearance to wisteria give off a fragrant scent. This enticing scent attracts bees and other insects to sample its nectar. As a member of the legume family, black locust is known for its ability to fix nitrogen in the soil and improve soil fertility. It is the tree that is commonly used to restore soil in areas that have been mined.

The native range for black locust tree is the southern Appalachian and the Ozark Mountains plus two small pockets of trees located in southeastern Indiana and southern Illinois. These trees prefer a humid climate with sandy or rocky soil. Black locust are a sturdy beautiful tree but they are aggressive and can become invasive. In Illinois, black locust trees pose a potential threat to upland natural areas and are a particularly serious management problem on hill prairies, sand prairies, and savannas. Today the black locust is present and has naturalized in all of the lower 48 states. Not many of the seeds from black locust germinate, but it is a clonal colony grower. This means that it sprouts new trees from its network of roots that hold the soil in place.

There is a long history to this tree and the utilitarian purposes it served. It has been sought after for its durability in the ground as fence posts. Black locusts were brought to Europe and became a favorite ornamental landscape tree because of its delicate foliage and fragrant blooms. Stands of trees have been planted for honey production. The roots of these trees stabilized eroding areas and fixed nitrogen in the soil. England used the pollution tolerant root stabilizing black locusts to shore up the rail line embankments. Black locust has the highest beam strength of any North American tree. This strength made it a favored choice by Native Americans for making archery bows. It was also used as trunnels or large wooden pins that held timbers of wooden sailing ships together. For warmth, this slow burning black locust wood was a great choice. One cord of black locust wood, 4 ft. wide by 4 ft. tall by 8 ft. long, provided the same Btu potential as a ton of anthracite coal. This is one of the highest Btu ratings of all American trees.

Poisoning of domestic livestock, sheep, cattle, and horses has occurred from consumption of black locust. Although in Pakistan and New Zealand they grow this same tree to feed domestic goats. It is a food source for wildlife including white-tailed deer, rabbits, ruffed grouse, squirrels, and bob whites, as well as millipedes and the silver-spotted skipper butterfly. Black locusts provide important cover for nesting, roosting, and thermal protection of wildlife. While humans can be poisoned by eating the leafy or woody parts of the tree, they can drink tea made from the flowers and eat honey from its blossoms

At some point a farmer planted black locust here because it was recommended as a way to protect his soil and serve farming needs in many other ways. There are positive and negative aspects to how black locust trees impact the environment. Once black locust are established they prove to be a hard species to remove. The shade provided by these black locust trees does make a nice place to contemplate these issues.

Four generations of European settlers farmed the land destined to become Midewin. This spanned a time period of 80 years. Before the arsenal was built there were 224 farmsteads 14 schools, and 5 cemeteries on what became the arsenal and part of which is now Midewin.

Early settlers to Illinois tallgrass prairie in Illinois had learned there was fertile soil beneath the prairie. Gone was the notion that land only growing grass was infertile. It was once thought that soil without trees would not grow crops. Prairie soil was difficult to till because of the thick prairie roots. All wooded land in Illinois was claimed by 1835, while large tracts of open prairie land were still available for purchase from the government for another 20 years. Once settlers ventured out onto the prairie to farm they still needed timber for building and for heat. In addition to the prairie land, settlers also purchased 10 to 20 acre wooded lots near rivers or streams to supply their timber needs. These timber lots could be as far as 10 to 15 miles from their farm.

There was black gold in the soil locked beneath the roots of prairie plants. Getting to this rich soil was the problem for these early settlers. Cutting through the intertwined roots and massive root stocks was a daunting task. Farmers struggled when using the standard wood plow to cut into the prairie sod. These first settlers were subsistence farming. It took so long to create fields that the fields were small. The crops they grew were just enough to feed their families.

This standard plow was called a moldboard plow. This plow introduced a horizontal cutting blade and moldboard enabling a total rotation of the soil, bringing fresh nutrients to the surface and burying the remains of prairie plants, weeds, or previous year’s crops. The first versions of this style plow were made of wood. Cast iron was added to later moldboard plows to create a sharper edge. This cast iron could be sharpened with a file as needed. The cast iron also helped deal with rocky New England soils. Although adding cast iron created a much heavier plow.

Illinois settlers had to purchase the land they wanted to farm. They had two years to make enough money to pay off their loans. If a settler wanted more acreage plowed sooner and could afford it he hired commercial plowmen to cut the prairie roots. The price per acre for “breaking prairie” varied from $2-$4 per acre. They used a huge double wheeled plow with a 7 to 12 foot beam and 24 to 32 inch moldboard made from cast iron. Three to six yoke or pair of oxen were needed to pull these plows. A crew of 2 to 3 men was needed to drive the oxen team, guide the plow and control the depth of the furrow, and scrape off soil that stuck to the moldboard. Illinois soil is heavy as well as sticky. Prairie soil did not “scour” or fall off the cast iron moldboard like woodland soils.

Not all settlers could afford a hire big crews of men to break prairie for them. They used whatever sized plows they had from 12 to 30 inch. They used oxen if they had them but horses were used, too. Settlers would pooled their resources. One neighbor might own a breaking plow but not enough livestock to pull the plow. While another had the livestock but not the farm equipment. Surviving the prairie meant settlers helped their neighbors. Taming the prairie was back breaking work but made easier with the hand of a neighbor.

Two to three acres could be broken in a day depending on the size of the plow and the number of oxen used. The goal of turning the sod was to cause it to rot. It could take several years for grass roots to rot into a nice loamy soil. Through trial and error settlers found it best to break the prairie sod from early or mid-May to mid-July. A man could break an “eighty” that is eighty acres in two months and plant it with “sod corn” or flax. “Sod corn” could be planted every fourth row. The other option was to cut a slice with an ax into the overturned sod & drop 3 to 4 kernels of corn into each slice and seal the cut by stepping on it. The rotting roots helped grow the “sod corn”. This would yield a half crop of corn in the fall of 15 to 25 bushels per acre.

Several individuals, including John Lane of Will County, Illinois, developed a steel version of the moldboard plow. The key to these new plows was the use of polished steel. Moldboard plows made from this new wrought steel were lighter, cut efficiently and stayed sharp, were not brittle and easily broken like cast iron, and sticky soils of the prairie scoured right off the moldboard. The first man to patent his version of the cast-steel moldboard plow was John Deere of Grand Detour, Illinois in 1837. He then perfected a way to mass manufacture an affordable plow for farmers by the 1850’s.

Ten times the amount of land could now be cultivated or broken by a farmer with just a three horse team and John Deere’s “self-polisher”. This simple invention changed the lives of farmers in the 19th century dramatically. This plow was equal to the prairie sod. It is said that the cutting of the roots of prairie plants sounded like a volley of pistol shots which was further amplified by the tempered steel of the moldboard. Breaking the prairie was a crucial step in unlocking the treasure beneath the sod. The steel plow let farmers plow more acres in fewer hours. Illinois and prairie land to the west were opened to an era of agricultural development. In Illinois, during the 1850’s, the population doubled from 850,000 to more that one and a half million people. Now with this new plow, farmers were no longer subsistence farming. They were growing food on what were once prairies for the growing population.

Look above you. The tree that towers above you now is the Osage orange tree. The straight Line of trees you see were planted to act as a fence. The hedge apple has a vibrant orange inner bark. The fruit of the tree is neon green and the size of a grapefruit with a very bumpy surface. Osage orange tolerates poor soil, extreme heat, strong winds, is easily transplanted, and has relatively few insect or disease problems. Young trees and new growth on trees have sharp ½ to 1 inch thorns. Thorns, its dense growth when pruned, and its ability to survive extreme conditions are the reasons this tree came to the prairie.

Settlers needed to keep their livestock away from their crops and the railroad tracks. On the prairie, trees were scarce and wood was a precious commodity. Building fencing to contain cattle was an expensive proposition. Split rail fences were expensive, $500 per mile. A prairie fire would easily destroy the costly fencing, sending all a farmer’s hard work and money up in smoke. Wire fencing at the time was brittle, not galvanized, causing the wire to rust and easily break. In the 1840’s, a movement to use these thorny trees as fencing began. Illinois was the first of the prairie states that introduced the Osage orange as a living fence. From there it spread to other Midwestern states.

By 1855, 1,000 bushels of Osage orange seed was shipped from Texas and Arkansas to Illinois. Seed cost as much as $50 per bushel. In 1858, in the book “Hedges and Evergreens”, John Warden wrote, “It is no longer a matter of experiment, whether the Osage orange will make a fence or not. It is a proved fact that… a hedge can be grown in four years, so compact that no kind of stock can pass it.” Osage orange trees grown closely together and pruned were considered “bull strong, hog tight, and horse high”. This meant a bull couldn’t push through the thorns, a hog could not get through the tight growth, and a horse could not jump over it.

This living fence needed to be pruned to a height of three to five feet tall annually. Trimming this tough wood was dangerous work. Gangs of hedge cutters traveled the state using sharp scythes to keep the trees short and encourage new growth which is where the thorns occur. This row of trees was pruned by the Shumacher family who farmed the land. By 1870, 70% of Kankakee County, Illinois prairie fencing was Osage orange. Living fencing was popular for about 25 years.

Barbed wire came onto the farming scene at the 1873 DeKalb County Fair in Illinois. Barbed wire required less maintenance. Fencing did not require the yearly pruning of miles of trees. Additionally, precious water for crops was not used by Osage orange trees especially during periods of drought. Where did these living fences go when barbed wire became the rage? Look up at the trees you are standing under. When pruning stopped, trees grew to their mature heights of 40 to 60 feet tall with a crown spread of up to 40 feet. This line of Osage orange trees were once a fence. After barbed wire was introduced, farmers still used these trees as rot resistant fence posts, for wind breaks, and as a heat source because its wood burned hot.

This tree is not native to the tallgrass prairie of Illinois. These trees are native to the Red River Valley of Oklahoma, Texas, and Arkansas. Osage Indians used this strong yet flexible wood to make prized bows. It is recorded that one bow made from the Osage Orange tree was traded for a horse and blanket, showing how great of a value was placed on a bow made from this tree. French trappers called these trees “bois d’arc”(bwă-därk). It means “wood of the bow”.

An Anglicized corruption, of this French name, is bodark(bō-därk) or bodock(bōdŏck). Other common names for this tree are hedge apple, Osage apple, Osage orange, and horse apple. Wazhazhe(wăzhăzhā) is the name given to this tree by the Osage Nation. The wood from this tree was valued by not only the Osage people but by the Comanches, Kiowas, Pawnees, Omahas, Seminoles, and other nations. This thorny tree is a part of the history of the Illinois prairie. This line of Osage orange trees tell a story about the settlers, who struggled to tame the prairie with fences they grew form living trees.

“The secret of farming is dung & drainage.” That was the credo of farming as coined in the 19th century by New York Farmer John Johnston. Before European settlement of Illinois there were 8 million acres of wetland interspersed with prairie. Almost a quarter of Illinois was made up of this prairie-wetland mosaic. It took Illinois farmers one century to reduce 8 million acres of wetland to 1 million acres of wetland as they created their farms.

How do you drain a state? Farmers started by using ditches, hollowed out tree trunks, and stones laid on top of one another. In the mid-1800s, John Johnston, a Scottish born farmer, started using drain tiles. Drain tiles were commonly used in Europe to create farmland that had just the right amount of moisture for farm crops. Most people today think of tile as the flat, square, kitchen tiles. Drain tiles are round pipes made from simple fired red clay ranging from 6 to 24 inches in diameter and 1 to 2 feet in length. Farmers initially made these drain tiles themselves. As demand grew, mass manufacturing began.

Drain tiles work by letting water percolate down through the soil. When water reaches the drain tile it enters through un-cemented joints. The action of water flowing through the tiles pulls more water into the system and eventually deposits the water into ditches, streams, and rivers.

Tile draining was well known in Europe and the Middle East for centuries before it was used in the United States. Placing drain tiles in a grid pattern in a field will remove subsurface water from the soil. This allows roots to grow and oxygen to exist in the soil around plant roots to increase crop yields. John Johnston’s first experiment in tile drainage increased yield in a 10-acre plot from 5 bushels per acre to 50 bushels per acre.

Midewin has an average of 78 feet per acre of field tile. This equals 283 miles of drain tile. It is enough to connect Springfield, Illinois to Fond Du Lac, Wisconsin.

While draining land is good for increasing crop production it has a negative impact on wetland species. To restore Midewin, the tile must first be removed or disabled. This allows the natural hydrologic system to return and native habitats to be restored.

“July 7th – I fell asleep, and when I was awakened at dawn this morning, by my companion, that I might not lose the scene, I started with surprise and delight. I was in the midst of a prairie! A world of grass and flowers stretched around me, rising and falling in gentle undulations, as if an enchanter had struck the ocean swell, and it was at rest forever. Acres of wild flowers of every hue glowed around me, and the sun was arising from the earth where it touched the horizon, ‘kissing with golden face the meadows green.’ What a new and wondrous world of beauty! What a magnificent sight! Those glorious ranks of flowers! Oh that you could have ‘one glance at their array!’ How shall I convey to you an idea of a prairie. I despair, for never yet hath pen brought the scene before my mind. Imagine yourself in the centre of an immense circle of velvet herbage, the sky for its boundary upon every side, the whole clothed with a radiant efflorescence of every brilliant hue. We rode thus through a perfect wilderness of sweets, sending forth perfume, and animated with myriads of glittering birds and butterflies.

It was, in fact, a vast garden, over whose perfumed paths, covered with soil as hard as gravel, our carriage rolled through the whole of that summer day. You will scarcely credit the profusion of flowers upon these prairies. We passed whole acres of blossoms all bearing one hue, as purple, perhaps, or masses of yellow or rose, and then again a carpet of every color intermixed, or narrow bands, as if a rainbow had fallen upon the verdant slopes. When the sun flooded this Mosaic floor with light, and the summer breeze stirred among their leaves, the iridescent glow was beautiful and wondrous beyond any thing I had ever conceived.

The gentle undulating surface of these prairies prevent sameness and add variety to its lights and shades. Occasionally, when a swell is rather higher than the rest, it gives you an extended view over the country, and you may mark a dark green waving line of trees near the distant horizon, which are shading some gentle stream from the sun's shooting rays, and thus, betraying the secret of their silent course. Oak openings also occur, green groves, arranged with the regularity of art, making shady alleys for the heated traveler. What a tender benevolent Father have we, to form for us so bright a world! How filled with glory and beauty must that mind have been, who conceived so much loveliness!

The oasis, or oak openings, upon the prairies are very beautiful. We passed through one this morning. It presented the appearance of a lawn, or park around some gentleman's seat. The trees are generally oak, arranged in pretty clumps or clusters upon the smooth grass - or in long avenues, as if planted thus by man. From their limbs hang pretty vines, as pea vine - lonicera lava, honeysuckle and white convolvalus. While our carriage wound among these clumps, or through the avenues, it was almost impossible to dispel the illusion that we were not driving through the domain of some rich proprietor, and we almost expected to draw up before the door of some lordly mansion.”

It was the summer of 1840, Eliza Steele traveled west from New York. She settled into a stage coach in Chicago on the night of July 7th. She was headed to Peoria, IL. At dawn, near Joliet, IL, she was awoken by a companion. You have just heard the beauty she saw in the tallgrass prairie. Eliza kept a journal of her travels and it was later published by J.S. Taylor & Co. You can read her words in the book, Summer Journey in the West.

People arrived on the land we call Illinois 10,000 years ago. It was a tree filled land. Changes to the land came slowly and 5,500 years after people arrived, tall grass prairie came to dominate this same land. The land was not effected too greatly by man. Unstoppable winds blew across grasses, sun baked the earth, rains soaked the sod, and storms danced through the plains. Humans had little effect on this vast grassland except for the occasional fires they started that would sweep across the horizon. The interaction of creatures that made this prairie web carried on.

In the 1830’s men from the East began to affect the prairie in new ways. They tried to tame a wildness. Settlers said they “broke the prairie.” They plowed the sod, drained the soil, built houses and farms, laid drain tiles, constructed roads, planted crops, divided the land with fencing, and laid railroads for eighty years. Then for sixty years after the farmers, man used the land as a place to manufacture explosives and construct weapons to protect a nation. Even as a munitions plant, farming and grazing domestic animals on some of this land continued. Alien plants from other ecosystems and countries were brought to the prairie accidentally and intentionally. These plants did not fit into the prairie web and grew with abandon. Fire was seen as a danger and no longer scoured the Illinois lands of trees and woody shrubs. Prairie seemed like a distant memory to the land. The land waited.

In the spring of 2009, the land north of the spot where you now stand was given a resuscitating breath of prairie plant and seed. These 50 acres north of this trail had been used agriculturally in row crops for 40 years before the army bought the land. In 2009, 5,000 plugs of prairie plants were put into the ground, 1,000 lbs. of prairie seed were spread over the soil, and one hundred twenty three different plant species for mesic and wet-mesic environments were chosen. Since the long awaited infusion of prairie plants in 2009, more than 20,000 plugs have been planted by volunteers and contractors.

Much of the seed to create this 50 acres of restored prairie came from remnant patches of prairie that grew unseen and unheeded on the cemeteries and along the railroad lines that are part of Midewin. These seeds were planted in huge production beds to create a source of local seed for recreating the prairie mosaic of Midewin. Along with the blend of prairie plants added back to these 50 acres, fire has also taken its rightful place as a nurturer of the prairie land.

Seed for new prairie plantings are gathered from rows of seed beds and other wilder restored areas. Each year 1,500 lbs. are gathered from seed beds and restored areas on this land. At Midewin, seed beds are located at River Road, Turtle Pond, and at the Welcome Center.

Currently 3,000 acres of tallgrass prairie in its many forms, from dolomite to wetland to mesic prairie, have begun the restoration process. This renewed prairie must be managed to add new prairie species and to control invasive plants through mechanical removal, herbicide, and controlled fire. The restoration process continues and will eventually touch all the 19,161 acres of Midewin. It can take a lifetime and more to recreate the prairie mosaic, we unwittingly destroyed. The land is patient. It will wait for us.

Over the past 2 million years, four separate mile high glaciers rolled south from Canada down through Illinois as temperatures alternately plummeted and warmed four times throughout this period. As these glaciers moved at a snail’s pace over Illinois, they scrapped the land clean of vegetation, rocks, and soil. While trapped inside the moving ice, these materials were ground to rounded particles ranging in size from clay to boulder resulting in deposits called till. These greedy glaciers held and moved these eroded materials within the frozen ice until warmer temperatures prevailed causing the glacier to eventually melt back north. The last of these glaciers remained here in Illinois until 18,000 years ago before melting completely. This melting caused the glacier to release its load. Since the melting was not uniform, a hilly terrain was created. The melting ice allowed rocks and soil it was carrying to be deposited as moraines. You are now standing on the Rockdale moraine.

As long as the climate was cold enough to keep the ice frozen, all rocks and soils remained in the glaciers. Eventually, the climate warmed sufficiently for these glaciers to slowly melt back north. A melting glacier deposited the till that once remained in its icy grip. The most recent glacier’s retreat was fairly constant, but sometimes it paused for short periods of time leaving ridges of till called recessional moraines. The Rockdale moraine is an excellent example of a recessional moraine. Many recessional moraines exist from here to central Illinois. This indicates that the glacier experienced many pauses resulting in multiple recessional moraines.

Along the edge of the Iron Bridge Trail near the Bison pasture lies a small boulder of granite that was left behind from the last glacier. This boulder is called an erratic. A glacier carried it here from Canada. We know the bedrock in this region of Illinois is limestone that was formed when subtropical oceans existed here. Canada’s bedrock is granite which crystalized from a molten state in Canada. Granite is not a part of this limestone bedrock in Illinois. So, how did that granite boulder get here? Geologists conclude that it had to have been carried here from Canada by a glacier. The sparkly crystals in granite are quartz and mica making it easy to identify. At some point in its melting stage the glacier dropped this erratic along with the other ingredients in till.

Look to the southeast at the bison pasture. You will see the rolling hills of glacial till called hummocky topography. A glacier left the raw materials of rock and soil during its melting phase. Living things, climate, and topography would induce changes in this raw soil over the centuries until it became extremely fertile. Prairie and farmlands developed on this new rich soil that was now ready for the prosperity of human beings as they migrated into this region setting up homesteads and creating farms for their livelihood.