World of Change: Coastline Change

Produced by the Space Telescope Science Institute’s Office of Public Outreach in collaboration with the NASA Earth Observatory (https://earthobservatory.nasa.gov/).

 

Story adapted from Image of the Day post: https://earthobservatory.nasa.gov/world-of-change/cape_cod.php

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Text, World of Change. The Earth spins in space against twinkling stars.

 

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Coastline Change on Cape Cod.

 

An aerial view of Cape Cod Bay, Massachusetts, United States with the Cape Cod National Seashore forming a sickle shaped peninsula. 1984 to 2020. The southeastern elbow of Cape Cod, where the New England coast reaches out into the North Atlantic, is a classic example of a common feature known as a spit or barrier beach. To the south Martha's Vineyard and Nantucket Island. A grassy coastline gives way to a sandy beach as waves break along the shore. US Fish and Wildlife Service. Like all barrier beach systems and much of the Atlantic shore, this part of Cape Cod consists primarily of loose sediment tenuously anchored by vegetation. A massive sandbar stretches to the horizon. Christopher Seufert Photography. The persistent force of winds, waves, and ocean currents move sand slowly from one place to another while violent storms replace the coastline overnight. Islands and other coastal landforms arise, grow, shrink, and migrate as sediment is eroded from one place and deposited in another.

 

Nantucket Sound is separated from the Atlantic Ocean by the barrier islands off the southeast corner of Cape Cod. These images from NASA's Landsat satellites show how the coastline of Catham, Massachusetts changed between 1984 and 2020. Watch how wind and water move sand, replacing the beaches, islands, and spits (light tan), as well as the underwater shoals and sandbars (light green). North Beach is labeled along the main coast and the barrier islands formed to the south are labeled North and South Monomey Island.

 

From 1984 the sands shift.

 

A third island breaks from the north beach main coast in 1990. Then reconnects to the coast and begins to grow larger.

 

In 2001, the new barrier stretches the length of the others.

 

In 2007 a fourth spit breaks off from the north beach farther up.

 

An inlet begins forming in the gap between. And in 2013 the third spit splits in two.

 

By 2013 three barrier islands now guard the coast.

 

By 2018 and 2019 the middle island gradually erodes and recedes west, as the southern barrier stretches far south. In 2020 the new coast is labeled North Beach, North Beach Island split off along the main coast, South Beach, the eroded middle section, and Monomey Island, the large barrier to the south. June 1984 and August 2020 are compared side by side.