Editor’s note: This is the 19th in a series of articles covering the region’s dramatically changing coastline. Click here to see all of the articles.

The Changing Shape of the Cape & Islands: The Atlantic Shoreline, Annual Guide 2018 Cape Cod LIFE | capecodlife.com

Pictured here, the portion of the Atlantic coast of Outer Cape Cod from Truro to Provincetown. Photo by Paul Rifkin

Beginning in April 2015 and spanning 18 articles since then, Cape Cod LIFE has showcased many localities on the Cape and Islands that have been affected by shoreline change. The “Shape of the Cape” series has shined a light on the situation of places such as Town Neck Beach in Sandwich, Lewis Bay, the Monomoy Islands, Great Point on Nantucket, and many more.

If Cape Cod is shaped like an arm, the portion known as the Lower and Outer Cape would extend from the elbow up to the hand. This includes the towns of Chatham, Orleans, Eastham, Wellfleet, Truro and Provincetown. It also includes the entire 43,600-acre Cape Cod National Seashore. The Outer Cape perhaps more than any other area on the peninsula has changed extensively over time.

According to the 2015 “Guide to Coastal Landforms and Processes at the Cape Cod National Seashore, Massachusetts—A Primer” by the USGS, Cape Cod’s history goes back about 15,000 years when the continental ice sheet originating in Eastern Canada retreated and left behind deposits of sand, granite, gravel and silt. In the years following that retreat the sea level rose by about 400 feet, which submerged much of what the ice had left behind. By 10,000 years ago the sea level had risen to such a point that it was beginning to submerge previous land masses. This included Stellwagen Bank, an area stretching 19 miles north-northeast off the coast of Provincetown, and Georges Bank, an area 62 miles off the east coast of Cape Cod that is larger in area than the entire state of Massachusetts.