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
Rock River (Lake Champlain) distance in Quebec before returning to the U.S., where it flows into Missisquoi Bay, an arm of Lake Champlain. Rock River (Lake Champlain) The Rock River is a short tributary of Lake Champlain in northern Vermont in the United States and southern Quebec in Canada. Via Lake Champlain and the Richelieu River, it is part of the watershed of the St. Lawrence River. According to the Geographic Names Information System, it is also known as "River Rocher" and "Riviere de La Roche." The Rock River flows for most of its length in Franklin County, Vermont, rising in the town of