06/08/2026
The divide between the Huron and Erie basins survived multiple Ice Age advances because of a bedrock high beneath Detroit and Windsor.
To the north, glaciers deepened the basin that holds Lake Huron. To the south, they excavated the basin that became Lake Erie. To the west, they carved the much deeper and longer Lake Michigan basin.
Yet the Detroit-Windsor corridor survived multiple glaciations as a relative high between Huron and Erie.
The reason lies in the bedrock below. Resistant limestone and dolostone beneath the land on both sides of the St. Clair and Detroit rivers withstood erosion better than many of the surrounding rocks. As glaciers advanced and retreated across the region multiple times, they deepened the neighboring basins while this area remained comparatively elevated.
You can still see the result today. Water leaving Lake Huron flows through the St. Clair River, Lake St. Clair, and the Detroit River before reaching Lake Erie. Those waterways cross the same bedrock high that separates the two basins.
Despite connecting two Great Lakes, the St. Clair and Detroit rivers were not naturally deep enough for modern oceangoing vessels. Large portions of the shipping channel had to be blasted and/or dredged to create the navigation route used today.
The Great Lakes were shaped by glaciers, but the glaciers were working with a geologic framework that already existed. In the Detroit-Windsor corridor, that framework helped determine where one Great Lake basin ended and another began.
Image: Google Earth
