The United States contains 84,000 miles of coastline, including the Atlantic, Gulf, and Pacific coasts, the Great Lakes, Alaska, Hawaii and Caribbean islands. Throughout this vast amount of territory, great variations exist between the coasts due to differences in climate, sediment supply, geology and wave energy.
Some coasts are characterized by small pockets of rocky sediments, such as those in northern New England and the Pacific Northwest. Sand-filled beaches dominate the mid-Atlantic coast and parts of the Gulf coast. Still other coasts are composed primarily of marshes and mudflats, particularly in the Mississippi River delta, while volcanic activity controls the geomorphology of Hawaii's coasts. Differences exist even between similar sections of the coast in a given area.
All coastal areas are dynamic places where land and water continually interact and affect each other. An understanding of coastal diversity is crucial for the formation and implementation of effective management alternatives in the coastal zone.