Why are raised beaches found around the Great Lakes?

Raised beaches are found around the Great Lakes primarily due to the combined effects of glacial retreat and postglacial crustal rebound.

During the Pleistocene Epoch, the immense weight of massive ice sheets depressed the Earth’s crust in the region. As these glaciers melted and retreated, the land—no longer burdened by the weight of the ice—began a slow process of rising, known as isostatic rebound.12

Simultaneously, the drainage patterns of the early, larger glacial lakes shifted as new outlets were exposed and others were closed off by this rising land. As the water levels in these ancient lakes dropped, the former shorelines were left behind at higher elevations. These abandoned shorelines, or strandlines, now stand above the present-day water levels as raised beaches. This ongoing uplift continues to affect the region today, occurring at a rate of approximately 1 foot every 100 years.123