Gulf of St. Lawrence
The gulf lies between the mouth of the St. Lawrence River and the islands of Newfoundland and Cape Breton. The Laurentian Trough, between the two islands, was scoured out by the Laurentide Ice Sheet during the last ice age. It channels sediment from the river over the edge of the continental shelf and onto the Laurentian Fan. The St. Lawrence River is the largest freshwater input to the Atlantic from the North American east coast, and its mouth is the largest estuary of its type in the world. The St. Lawrence Seaway, which was opened in 1959, gives vital shipping access to the Great Lakes.