Cape Codis a peninsula extending into the Atlantic Ocean from the southeastern corner of mainland Massachusetts, in the northeastern United States. Its historic, maritime character and ample beaches attract heavy tourism during the summer months. The name Cape Cod, coined in 1602 by Bartholomew Gosnold, is the ninth oldest English place-name in the U.S.
As defined by the Cape Cod Commission‘s enabling legislation, Cape Cod is conterminous with Barnstable County, Massachusetts. It extends from Provincetown in the northeast to Woods Hole in the southwest, and is bordered by Plymouth to the northwest. The Cape is divided into fifteen towns, several of which are in turn made up of multiple named villages. Cape Cod forms the southern boundary of the Gulf of Maine, which extends north-eastward to Nova Scotia.
Since 1914, most of Cape Cod has been separated from the mainland by the Cape Cod Canal. The canal cuts 7 miles (11 km) roughly across the base of the peninsula, though small portions of the Cape Cod towns of Bourne and Sandwich lie on the mainland side of the canal. Two highway bridges cross the Cape Cod Canal: the Sagamore Bridge and the Bourne Bridge. In addition, the Cape Cod Canal Railroad Bridge carries railway freight and provides limited passenger service onto the Cape.
The bulk of the land on Cape Cod consists of glacial landforms, formed by terminal moraine and outwash plains. This represents the southernmost extent of glacial coverage in southeast New England; similar glacial formations make up Long Island in New York and Block Island in Rhode Island. Together, these formations are known as the Outer Lands, or more obscurely as the “Isles of Stirling”. Geologically speaking, Cape Cod is quite young, having been laid down some 16,000 to 20,000 years ago.
Most of Cape Cod’s geological history involves the advance and retreat of the Laurentide Ice Sheet in the late Pleistocene geological era and the subsequent changes in sea level. Using radiocarbon dating techniques, researchers have determined that around 23,000 years ago, the ice sheet reached its maximum southward advance over North America, and then started to retreat. Many kettle ponds – clear, cold lakes – were formed and remain on Cape Cod as a result of the receding glacier. By about 18,000 years ago, the ice sheet had retreated past Cape Cod. By roughly 15,000 years ago, it had retreated past southern New England. When so much of Earth’s water was locked up in massive ice sheets, the sea level was lower. Truro’s bayside beaches used to be a petrified forest, before it became a beach.
As the ice began to melt, the sea began to rise. Initially, sea level rose quickly, about 15 metres (49 ft) per 1,000 years, but then the rate declined. On Cape Cod, sea level rose roughly 3 metres (9.8 ft) per millennium between 6,000 and 2,000 years ago. After that, it continued to rise at about 1 metre (3.3 ft) per millennium. By 6,000 years ago, the sea level was high enough to start eroding the glacial deposits that the vanished continental ice sheet had left on Cape Cod. The water transported the eroded deposits north and south along the outer Cape’s shoreline through a process known as longshore drift. Those reworked sediments that moved north went to the tip of Cape Cod. The entire town of Provincetown, at the extreme tip of the Cape, is a spit consisting largely of deposited marine sediment that was eroded and transported from farther south along the shore. Those sediments that instead moved south created the islands and shoals of Monomoy. So while other parts of the Cape have dwindled from the action of the waves, these parts of the Cape have grown through the deposition of sediment in just the last 6,000 years.
This process continues today. Due to their exposure to the open ocean, the Cape and islands are subject to considerable coastal erosion. Geologists say that due to erosion, the Cape will be completely submerged by the sea within several thousand years. This erosion causes the washout of beaches and the destruction of the barrier islands; for example, the ocean broke through the barrier island at Chatham during Hurricane Bob in 1991, allowing waves and storm surges to hit the coast with no obstruction. Consequently, the sediment and sand from the beaches is being washed away and deposited elsewhere. While this destroys land in some places, it creates land elsewhere, most noticeably in marshes where sediment is deposited by flowing water.