Saint Lawrence River - Geography

Geography

The Saint Lawrence River originates at the outflow of Lake Ontario between Kingston, Ontario, on the north bank, Wolfe Island in mid-stream, and Cape Vincent, New York. From there, it passes Gananoque, Brockville, Morrisburg, Ogdensburg, Massena, Cornwall, Montreal, Trois-Rivières, and Quebec City before draining into the Gulf of Saint Lawrence, one of the largest estuaries in the world. The estuary portion begins at the eastern tip of Île d'Orléans, just downstream from Quebec City. The river becomes tidal in the vicinity of Quebec City.

The river runs 3,058 km (1,900 mi) from the farthest headwater to the mouth and 1,197 km (743.8 mi) from the outflow of Lake Ontario. The farthest headwater is the North River in the Mesabi Range at Hibbing, Minnesota. Its drainage area, which includes the Great Lakes and hence the world's largest system of fresh water lakes, has a size of 1,344,200 km2 (519,000 sq mi), of which 839,200 km2 (324,000 sq mi) is in Canada and 505,000 km2 (195,000 sq mi) is in the United States. The basin covers parts of the provinces of Ontario and Quebec, and the states of Illinois, Indiana, Michigan, Minnesota, New York, Ohio, Pennsylvania, Vermont, and Wisconsin. The average discharge below the Saguenay River is 16,800 m3/s (590,000 cu ft/s). At Quebec City, it is 12,101 m3/s (427,300 cu ft/s). The average discharge at the river's source, the outflow of Lake Ontario, is 7,410 m3/s (262,000 cu ft/s).

The river includes Lake Saint-Louis south of Montreal, Lake Saint Francis at Salaberry-de-Valleyfield and Lac Saint-Pierre east of Montreal. It encompasses four archipelagoes: the Thousand Islands chain near Kingston, Ontario; the Hochelaga Archipelago, including the Island of Montreal and Île Jésus (Laval); the Lake St. Pierre Archipelago (Classified biosphere world reserve by the UNESCO in 2000) and the smaller Mingan Archipelago. Other islands include Île d'Orléans near Quebec City, and Anticosti Island north of the Gaspé. It is the second longest river in Canada.

Lake Champlain and the Ottawa, Richelieu, Saguenay and Saint-François rivers drain into the St. Lawrence.

The Saint Lawrence River is in a seismically active zone where fault reactivation is believed to occur along late Proterozoic to early Palaeozoic normal faults related to the opening of Iapetus Ocean. The faults in the area are rift related, which is called the Saint Lawrence rift system.

The Saint Lawrence Valley is a physiographic province of the larger Appalachian division, containing the Champlain and Northern physiographic section.