The coast and beach, where the continents meet the sea, are dynamic environments where agents of erosion vie with processes of deposition to produce a set of features reflecting their complex interplay and the influences of changes in sea level, climate, or sediment supply. "Coast" usually refers to the larger region of a continent or island which is significantly affected by its proximity to the sea, whereas "beach" refers to a much smaller region, usually just the areas directly affected by wave action.

The earth is constantly changing. Mountains are built up by tectonic forces, weathered, and eroded away. The erosional debris is deposited in the sea. In most places these changes occur so slowly that they are barely noticeable, but at the beach we can often watch them progress.

Most features of the beach environment are temporary, steady-state features. To illustrate...