![]() ![]() As sea level rose over the past 10,000 years, the ocean ate at the glacial deposits that lay as far as four miles offshore of the present coast. The landmass was laid down at the end of the last Ice Age as the Laurentide ice sheet retreated and rivers and streams of melt water dropped sediment and carved the landscape. Over the span of 30 years, three major breaches opened in the system and the barrier islands connected to the coastline and to each other.Īccording to Graham Giese, a coastal geologist at the Provincetown Center for Coastal Studies, the patterns of barrier and inlet evolution in this area have been going on for at least the past three hundred years, and perhaps longer. South of the mainland, North and South Monomoy Islands stood apart from each other and from the coast. In 1984, an unbroken barrier spit shielded the Atlantic-facing coast of Chatham and its harbor. The changes to the Nauset-Monomoy barrier system in this part of Cape Cod are sometimes subtle and sometimes dramatic. Visit our longer World of Change time series to see the years in between. Turn on the image comparison tool for an easier view of the changes. They show the shape of the coast off of Chatham, Massachusetts, on June 12, 1984, and July 30, 2013. The images above were acquired by the Operational Land Imager on Landsat 8 (top) and the Thematic Mapper on Landsat 5 (bottom). On the southeastern elbow of Cape Cod, where the New England coast reaches out into the cold and choppy North Atlantic, this natural progression has been taking place in full view of satellites for more than 30 years. This process allows them to naturally move ever upwards as sea levels rise. Hooks form, inlets open and close, and beaches slowly march across their back bays and lagoons toward the mainland. These sandy barriers are constantly raised up, shifted, and torn down by the natural ebb and flow of waves, currents, winds, and tides. In the United States, barrier spits and beaches line up along nearly a quarter of the coast. Sometimes they are islands and other times they are connected to land at one end, a feature dubbed a “spit.” Scientists estimate that there are more than 2,100 barriers fronting nearly 10 percent of the world’s continental shorelines. These strips of land are usually long and narrow, and run parallel to the mainland. Beaches are dynamic, living landscapes, and the prime example of beach evolution is the coastal barrier. ![]()
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