Typically, a beach is a long, narrow, gently sloping strip of land that runs along the coastline of a body of water. It may consist of sand, mud, rocks, or other materials. The contour of the beach depends on the type of material, as well as the coastal processes that shape it. Typical beaches are formed by ocean currents, but they can be caused by natural processes as well.
The most important processes for creating a beach are ocean currents and wind. These forces wash away sediment, and move it offshore and onshore. These changes affect both small and large areas of beach. Some materials can travel hundreds of kilometers. These include sand, seashell fragments, and pebbles. Other materials are derived from local bedrock or sediment. Some of these materials can be toxic, and can be ingested by human and marine mammals. They can also cause an upset stomach, and can be a source of meningitis, earaches, and other neurological disorders.
Most beach sand is formed from coral reefs and volcanic rock. This can vary in color, with a sandy brown, black, or pink beach being the most common. Some sand comes from other ocean debris, such as rock or cliffs near the beach. Other sand is derived from bedrock or local sediment, and some is organically derived from biologic components in the nearby ocean. The main sources of beach sand are tropical regions. Occasionally, sand is sourced from rocks in the Gulf of Mexico and Appalachian Mountains.
Beaches are affected by seasonal changes. The slope of the face of the beach changes with the intensity of waves that occur during the different seasons. This makes the beach wider during the summer, and less steep during the winter. In the North Atlantic, big waves come from the North Pacific. In the Mediterranean, beach rock is common.
In the tropics, the main source of beach sand is coral reefs. Some of these reefs are broken and eroded into large boulders or sand-sized pieces. These sand-sized pieces are carried off by the ocean to form sandbars. Some of these sandbars can become buried and create dunes. These dunes may contain plants that are grown in the dunes.
Another process that affects beaches is large cyclonic storms. These storms usually produce high waves and a surge of water. These cyclonic storms can move sediment and debris along the coast and redistribute beach sediment. This can lead to erosion of deep channels and sandbars.
In addition, inland drainage pipes can collect waste from inland areas and deposit it on the beach. This is known as beach nourishment. This process can enhance habitat for selected species of biota and has been effective in combating erosion. It can be done in small increments of sand at one to two year intervals.
Another process is longshore drift. This occurs when waves break on the surf zone, and the sand is swept into the rear of the beach. The beach is moved south along the coast by these currents. This type of drift is important for the long-term existence of beaches.