Barrier island

Barrier islands are the mainland offshore islands that separate one part of the sea from the open sea. They lie parallel to the coast and have a long, narrow shape. Toward the sea dunes often form the surface, to the land side they are flat. They were created by deposits of waves, currents and wind. Their formation requires a shallow coastal waters, a sufficiently large sediment supply and a weak to moderate tidal range. If the tide is too weak, arise only spits, the tide is higher than 4 m, arise only sandbanks.

Examples of barrier islands are the West and the East Frisian islands. Outer Banks off North Carolina on the East Coast or Virginia Key, Key Biscayne or St. George Iceland off the coasts of Florida