Earth Science Lesson: How Glaciers Shape the Land
About 13,000 years ago, this area looked very different than it does today. During the last Ice Age, massive glaciers—thousands of feet thick—slowly moved across northern Illinois. These glaciers acted like giant bulldozers, grinding rock, soil, and sediment beneath them and carrying that material forward as they advanced.
As the climate warmed, the glacier that covered this area began to melt and retreat. When glaciers slow down or stop, they deposit the sediment they were carrying. This deposited material is called glacial till, a mix of clay, sand, gravel, and stones of many sizes. Over time, this material formed the hill you are standing on today.
Unlike hills formed by tectonic forces or erosion, this hill is depositional, meaning it was built up by material left behind rather than carved out. These landforms include moraines, drumlins, eskers, and outwash plains.
What Makes This Site Unique
The hill at Headwaters Conservation Area is an excellent example of a glacial deposit landform, likely part of a ground moraine or low end moraine left behind as the glacier retreated. While Illinois is often thought of as “flat,” features like this hill tell the hidden story of powerful ice shaping the landscape. In adition, from where you are standing, you may be able to see another glacial deposit landform named Johnson's Mound. It is located approximately 3.5 miles to the south.
Logging Tasks (Required)
To log this EarthCache, please send your answers to the following questions:
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Sediment Observation:
Look closely at the ground near the posted coordinates. You should see a mixture of different sediment sizes (fine soil, sand, small stones). Why do you think glaciers leave behind mixed sediments instead of sorted layers.
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Hill Formation Analysis:
From the description above and your own observations, how can you tell this hill was formed by a glacier rather than by erosion from water or wind.
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Slope and Shape:
Describe the shape of the hill (steep, gentle, rounded, irregular). How does this shape support the idea that it was formed by deposited glacial material?
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Optional Photo:
Take a photo of yourself or your GPS at the site (no faces required).
Accessibility & Land Use
Headwaters Conservation Area is open to the public, and visitors are welcome to explore on foot. Please remain on established trails when possible.
Sources:
Glacial History of Northern Illinois
ISM - Illinois Agriculture - Land - Glaciers
Last Glacial Period - Wikipedia