Coastlines are boundaries between land and water that surround Earth's continents and islands. Scientists define the coast, or coastal zone, as a broad swath (belt) of land and sea where fresh water mixes with salt water. Land and sea processes work together to shape features along coastlines. Freshwater lakes do not technically have coastal zones, but many of the processes (waves, tides) and features found along ocean coastlines also exist in large lakes.

Coastal Zone Features

All coastlines include a thin strip of land that is submerged at high tide and exposed at low tide, called the shoreline. The coastal zone, however, extends far inland from the shore, across lowlands called coastal plains, and far seaward to the water depth where ocean waves do not reach the seafloor. The coastal zone includes lagoons, beaches, estuaries, tidal wetlands, tidal inlets, river deltas, barrier bars and islands, sand bars, and...