đ Beck Lake: Glacial Legacy in the Sediments
đ Location
Beck Lake lies in the Forest Preserves of Cook County near Des Plaines, Illinois. Nestled within a tranquil woodland, the lakeâs shorelines provide a valuable glimpse into the regionâs glacial pastâvisible not in the lake itself, but in the materials left behind by the glaciers that once covered this area.
Information for Beck Lake
đ§Â Earth Science Lesson: Glacial Till & Sediment Sorting
About 12,000â14,000 years ago, this region was covered by the Wisconsin Glacier. As it advanced and retreated, it ground down rock and soil, transporting massive amounts of debris with it. When the ice melted, it deposited this mixtureâknown as glacial tillâacross the landscape.
Glacial till is unsorted sediment: a chaotic blend of clay, sand, gravel, and boulders. Unlike rivers, which sort sediments by size and weight, glaciers drop everything at once.
Along the Beck Lake shoreline, you can observe the effects of this process firsthand:
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Scattered rocks of varying size and composition
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Sandy and silty patches alongside coarser gravels
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Occasional rounded stones transported from far-off regions
These materials werenât formed hereâthey were brought here by moving ice.
đ Logging Requirements
To log this EarthCache, visit Beck Lake and complete the following tasks:
Observe the sediment at the edge of the lake.
What types of materials do you see (sand, gravel, silt, clay, rocks)?
Are they sorted by size (like a river might do) or mixed together?
Find and describe two rocks along the shoreline.
What colors, shapes, or textures do they have?
Do they appear rounded (indicating transport) or angular (fresh breakage)?
Can you guess if they are sedimentary, igneous, or metamorphic?
Explain how these observations relate to glacial till.
Why are the materials here a sign of glacial action and not river or wind erosion?
(Optional but appreciated) Post a photo of your visit that includes part of the natural areaâbut no spoilers of the answers, please!
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