In Maine and parts of Alaska, glaciers have scoured most of the sediment cover from the shore. In the arctic, ice gouging and rafting have removed sand-sized particles from some beaches, leaving cobbles and boulders. Mainland beaches stretch unbroken for many miles along the edges of major land masses. They receive sediment from nearby rivers and eroding bluffs. Examples of mainland beaches include coasts of the Great Lakes, northern New Jersey, and southern California.
Pocket beaches form in small bays surrounded by rocky cliffs or headlands.
The headlands protect the sandy alcoves from erosion by winter storms and strong currents. Pocket beaches are common in New England and the Pacific Northwest. Barrier beaches are found along the Gulf of Mexico, the east coast, and much of Alaska. They are part of complex integrated systems of beaches, dunes, marshes, bays, tidal flats, and inlets. The barrier islands and beaches are constantly migrating, eroding, and building in response to natural processes and human activities.