Cape Cod National Seashore: A Coast Left by the Ice

Cape Cod National Seashore runs along the Atlantic-facing eastern shore of Cape Cod in Barnstable County, Massachusetts. Its coastline is geologically new, about 15,000 years old, and it is still changing.

A beach at Cape Cod National Seashore. Image from the National Park Service's page.

The seashore

Established on June 1, 1966, the seashore protects about 17,647 hectares (43,607 acres) of sandy beaches, dunes, woodlands, freshwater ponds and salt marshes, stretching nearly 64 km (40 mi) from Chatham to Provincetown.

Its cultural resources include archeological sites, lighthouses, cultural landscapes, the Old Harbor Life-Saving Station Museum, and the Marconi Station Site, where transatlantic wireless communication was achieved in 1903. Visitors swim, fish, hike, bicycle, canoe, snorkel and sightsee.

Built by glaciers

The seashore's ground is made of loose and partly consolidated gravel, sand, silt and mud laid down by ice sheets of Wisconsinan age, roughly 75,000 to 11,000 years ago.

Since the last glaciers retreated, climate-driven sea level rise has drowned much of the old coast, which once reached about 6.4 km (4.0 mi) seaward of today's shoreline.

Today's landforms are only a temporary holding pattern. Wind, waves and human activity will inevitably keep changing them.

Sand dunes at Cape Cod National Seashore. Image from the National Park Service's page.

The seashore belongs to the Coastal Plain physiographic province and shares its geologic history, and some of its characteristic formations, with a region reaching far beyond the park.

Maps and inventories

The Park Service's Geologic Resources Inventory, which produces digital geologic maps and reports for more than 270 natural resource parks, has products for the seashore, and a Soil Resources Inventory has been completed. Both are on the NPS DataStore.

Sources

Based on "NPS Geodiversity Atlas—Cape Cod National Seashore, Massachusetts," National Park Service Geologic Resources Inventory, which cites Anderson (2017) and Giese et al. (2015); a work of the United States government in the public domain.

The atlas gives the global sea level rise since the last glacial retreat as "approximately 400 m (120 m)," two figures that do not agree; this page gives neither.