My mom said it was a jetty. Jetties are built to prevent waves from eroding the beach by making the area more protected. I saw similar jetties and a wall at Morgan Park, a park along the coast of Glen Cove. The barrier islands, such as Fire Island, are gradually moving toward the South Shore. Fire Island is moving toward the shore at about 42 centimeters per year.
Storms are another big factor in shaping the landforms of Long Island.
Shinnecock Inlet was formed by a hurricane on September 21, 1938. There had been other inlets there in the past, but it took the storm to make it permanent. There are other inlets that have disappeared, such as Zacks, Gilgo, and Muncie Island. Only 0.5 billion years ago, the land that is now Long Island was actually part of a chain of volcanic islands. Millions of years ago, the east side of North America was facing south.