Coastal landforms

(geography) The characteristic features and patterns of land in a coastal zone subject to marine and subaerial processes of erosion and deposition.

The characteristic features and morphology of the land in the coastal zone. They are subject to processes of erosion and deposition as produced by winds, waves, tides, and river discharge. The interactions of these processes and the coastal environments produce a wide variety of landforms. Processes directed seaward from the land are dominated by the transport of sediment by rivers, but also include gravity processes such as landslides, rockfalls, and slumping. The dominant processes on the seaward side are wind, waves, and wave-generated currents. Mixed among these locations are tidal currents which also carry large volumes of sediment.

Subcontinental- to continental-scale coastal landform patterns are related to plate tectonics. The three major tectonic coastal types are leading-edge, trailing-edge, and marginal sea coasts. Leading-edge coasts are associated with colliding plate boundaries where there is considerable tectonic activity. Trailing-edge coasts are on stable continental margins, and marginal seas have fairly stable coasts with plate margins, commonly characterized by island arcs and volcanoes, that form their seaward boundaries. See also Continental margin; Plate tectonics.

The primary characteristics of leading-edge coasts is the rugged and irregular topography, commonly displaying cliffs or bluffs right up to the shoreline. Seaward, the topography reflects this with an irregular bottom and deep water near the shoreline. The geology is generally complex with numerous faults and folds in the strata of the coastal zone. These coasts tend to be dominated by erosion with only local areas of deposition, typically in the form of small beaches or spits between headlands. Waves tend to be large because of the deep nearshore water, and form wave-cut platforms, terraces, notches, sea stacks, and caves. See also Frame of reference.

The most diverse suite of coastal landforms develops along trailing-edge coasts. These coasts are generally developed along the margin of a coastal plain, they are fed by well-developed and large river systems, and they are subjected to a low-to-modest wave energy because of the gently sloping adjacent continental shelf. The overall appearance is little topographic relief dominated by deposition of mud and sand. The spectrum of environments and their associated landforms includes deltas, estuaries, barrier islands, tidal inlets, tidal flats, and salt marshes. See also Barrier islands; Coastal plain; Delta; Floodplain; Salt marsh.

Marginal coastal settings are along a stable continental mass and are protected from open ocean processes, commonly an island arc system or other form of a plate boundary. The consequence is a coastal zone that tends to be subjected to small waves and where considerable mud is allowed to accumulate in the coastal zone. Many coastal landforms are present in much the same fashion as on the trailing-edge coasts. Marginal sea coasts tend to have large river deltas. Examples are the eastern margin of Asia along the Gulf of Korea and the China Sea, the entire Gulf of Mexico, and the Mediterranean Sea. See also Depositional systems and environments; Nearshore processes.