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 Vermont are on the lake's western and eastern shores, respectively, and the village of Ticonderoga, New York is in the region's southern part. The Quebec portion is in the regional county municipalities of Le Haut-Richelieu and Brome-Missisquoi. There are a number of islands in the lake; the largest include Grand Isle, Isle La Motte, and North Hero, all part of Grand Isle County, Vermont. The Champlain Valley is the northernmost unit of a landform system known as the Great Appalachian Valley, which stretches between Quebec, Canada, to the north, and Alabama, US, to the south. The Champlain Valley is a