Ensuing dune formation then occurs on the seaward side, where another offshore submarine bar is formed which subsequently rises above the sea. The intervening area between the two dunes is filled with sand by the wind, resulting in a typical cross section: Beginning with the ocean there is the intertidal zone, the beach and the primary dune (primary in defense, but secondary in time); behind this is a trough, which rises to the inland dune, which in turn falls from the backdune to the flat zone, terminating in te bayshore and the bay.