What great geological event explains the formation of the great lakes the st Lawrence river system the Columbia snake river system and great salt lake?

During the last ice age, the great weight of the glaciers covering what is now The Great Lakes area actually lowered the land. It has been slowly rising up again since all the glaciers melted.

The melting of the glaciers provided tremendous amounts of water that scoured out pathways to the Pacific. They also filled the Great Lakes and overflowed to make rivers to the Atlantic.

The water flow created a river to The Great Salt Lake but not enough water enters it now to let it overflow to the sea. So the water just evaporates and keeps getting saltier.