Canada extends from the west coast, across the prairies and central Canada, to the Atlantic provinces. In the north there are three territories, between Alaska and Greenland: the Yukon in the west, then the Northwest Territories, then Nunavut. Four of the five Great Lakes (Superior, Huron, Erie, and Ontario) are shared between Canada and the United States (Lake Michigan is in the USA), and they make up 16% of the Earth's fresh water. The Saint Lawrence Seaway joins the Great Lakes to the Atlantic Ocean, allowing ocean going vessels to travel as far inland as Thunder Bay in Ontario, Canada.