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 George (New York) Mountain in the southern quarter of the lake. The northern end of the lake that is located near Ticonderoga is considered the southern end of the Champlain Valley, which includes Lake Champlain, as well as the cities Plattsburgh, New York and Burlington, Vermont. There are six known invasive species in Lake George. The Asian clam first found in 2010 is the biggest threat, along with the Eurasian watermilfoil. Other invasive species are the Chinese mystery snail, curly-leaf pondweed, spiny water flea, and zebra mussel. The lake was originally named the "Andia-ta-roc-te" by local Native Americans. James Fenimore Cooper in his