Cape Cod Bay is a large bay of the Atlantic Ocean adjacent to the U.S. state of Massachusetts. Measuring below a line drawn from Brant Rock in Marshfield to Race Point in Provincetown, Massachusetts, it is enclosed by Cape Cod to the south and east, and Plymouth County, Massachusetts, to the west. To the north of Cape Cod Bay lie Massachusetts Bay and the Atlantic Ocean. Cape Cod Bay is the southernmost extremity of the Gulf of Maine. Cape Cod Bay is one of the bays adjacent to Massachusetts that give it the name Bay State. The others are Narragansett Bay, Buzzards Bay, and Massachusetts Bay. History In 1524, Italian navigator Giovanni da Verrazzano was the first European to discover Cape Cod Bay, his claim proved by a map of 1529 which clearly outlined Cape Cod. In 1620, the Pilgrims first sheltered in Provincetown Harbor where they signed the Mayflower Compact, the first democratic document signed in the New World. Geology Most of Cape Cod is composed of glacially derived rocks, sands, and gravels. The last glacial period ended about 12,000 years ago. During the end of the last glaciation, Cape Cod Bay was probably a large freshwater lake with drainages across Cape Cod in places like Bass River and Orleans Harbor. The Provincetown Spit, i.e., the land north of High Head in North Truro, was formed by marine deposits over the last 5,000-8,000 years. These deposits created Provincetown Harbor, a large, bowl-shaped section of Cape Cod Bay. Generally, currents in the Bay move in a counter-clockwise fashion, moving south from Boston, to Plymouth then east and then north to Provincetown. Strong tides flow water into the Bay, cleansing the system with nutrient-rich sea water and maintaining a well-mixed marine environment that helps to maintain a generally healthy and productive system by exchanging roughly 9.3% of the total bay water volume on a regular basis. Surface water stratification and mixing have a distinct seasonal cycle in the Bay. In the winter, the density of bay water is nearly the same from top to bottom, allowing it to mix readily and become nutrient-rich all around. Stratification occurs when the surface water becomes warmer and less thick than the deeper water in the spring, summer, and early fall. Because the water is stratified and rich in nutrients in the spring, biological productivity in the bay is at its peak. Since 1914, Cape