Barrier Beaches of Long Island, NY
There are many different types of coasts that exist throughout the United States. The south shore of Long Island has a unique types of coast known as a barrier beach. Barrier beaches are long narrow land forms that are composed of sand and other lose sediments. These sediments are brought together by the actions of waves, currents and storm surges. Barrier beaches are subject to constant changes by the same forces. Sand is constantly eroded in one area an deposited in another. Barrier coasts are important for a number of reasons; they protect the mainland of Long Island from the open ocean and flooding during storms, for recreational use and the unique ecosystems which exist on barrier beaches.
Barrier Beaches stretch along the entire east coast of the United States. The barrier beaches from Long Island to Maine are known as Glaciated Coasts because their formation was assisted by glaciers. Eighteen thousands years ago a glacier covered most of the eastern US. This glacier terminated at present day Long Island. About fifteen thousands years ago the glacier began to retreat. As it melted it left behind mounds of rubble, called moraines. This particular glacier left behind two moraines because its final recession was a two part process. These two moraines are the Ronkonkoma Moraine and the Harbor Hill Moraine. The Ronkonkoma Moraine is located in central Long Island and the Harbor Hill Moraine is located on the northern part of Long Island. Besides the two moraines the glaciers deposited great amounts of debris offshore. This debris supplies the sand needed to create and maintain a barrier beach system (Hoel 16-18).
A typical barrier coast consist of the sandy beach, primary dune, secondary dunes and a bay. This is true of the barrier beaches of Long Island. Long Island is famous for its sandy ocean beaches. Between the barrier beach and the main coast is the Great South Bay. The beaches and dunes have very different characteristics. The sandy beach is the junction of land and ocean. The sandy beach consists of two zones, the swash zone and the drift line. The swash zone is the area of wet sand, caused by the incoming wave. The drift line is formed by the dead seaweed and other aquatic plants. Behind the sandy beach is the primary dune. The primary dune's main function is to absorb the force of the ocean and protect the great south bay and the island's main coast. In some cases secondary dunes form. These dunes are behind the primary dune and are therefor protected from the ocean. This provides the stability necessary for plant growth. Many time a maritime forests will form on secondary dunes.
Barrier beaches are not static, they are constantly being changed (Coastal Change ) by the forces that formed them; waves and wind. One change effecting barrier beaches is they are moving closer to the main coast. This movement is caused by the rise in...