Champlain Valley southward into the Valley of Vermont. The Vermont Lowlands are primarily underlain by sedimentary rocks, especially limestone and shale, though metamorphic rocks such as marble and slate are also present. Lake Champlain is situated in the Champlain Valley between the Green Mountains of Vermont and the Adirondack Mountains of New York, drained northward by the Richelieu River into the St. Lawrence River at Sorel-Tracy, Quebec (northeast of Montreal). Major tributaries of Lake Champlain include Otter Creek and the Winooski, Missisquoi, and Lamoille rivers in Vermont, and the Ausable, Chazy, Boquet, and Saranac rivers in New York. Lake Champlain also receives
Lake Champlain physiographic section of the larger Saint Lawrence Valley, which in turn is part of the larger Appalachian physiographic division. Lake Champlain is one of numerous large lakes scattered in an arc through Labrador, in Canada, the northern United States, and the Northwest Territories of Canada. Although it is smaller than each of the Great Lakes (Ontario, Erie, Huron, Superior, and Michigan), Lake Champlain is a large body of fresh water. Approximately in area, the lake is long and across at its widest point, and has a maximum depth of approximately . The lake varies seasonally from about above mean sea