The Wisconsin Glaciation

Conveniently, the most recent widespread glaciation of North America is known as the Wisconsin Glaciation. It started about 100,000 years ago (ya), but only reached Wisconsin about 31,000 ya. It later extended into Illinois and Indiana. By 11,000 ya, it finally retreated, having shaped almost every geological feature in the state, even in the Driftless. The maps below show the extent of the advances and retreats. Note that Glacial Lake Wisconsin waxes and wanes, before draining suddenly 19,000 years ago.

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