How was the great lakes and st lawerence lowland region made?

The Great Lakes and St. Lawrence Lowland region was formed by a series of geological events over millions of years. The region was covered by a shallow sea during the Ordovician period, and over time, the sea level dropped, leaving behind a series of sedimentary rocks. The area was then subjected to several periods of glaciation, which carved out the basins of the Great Lakes and the St. Lawrence River. The most recent glaciation, the Wisconsin glaciation, ended about 10,000 years ago, and the region has since been slowly rebounding from the weight of the ice.