During Earth's last major Ice Age, the forward motion of the continental ice sheet pushed rock as it advanced; the subsequent retreat of the continental ice sheet scraped rock off Earth's surface and pulled it out to sea. The build-up of this out-wash forms the landmass of Cape Cod.

About a third of Cape Cod National Seashore, which sits between Chatham and Provincetown, is comprised of coastal dune. Exposed bedrock lies 200 to 400 feet beneath the glacial sediments—which is why the image of Cape Cod is that of dunes, marshes, sandy beaches, and mudflats.

Read my blog post on the psychological effects of viewing forms, textures, and patterns of tidal landscapes here.