A beach is a landform that accumulates loose material like sand along the shore of a body of water. The material is usually shaped by the action of waves and currents, making it into a sort of slope that extends along the coastline. Beaches can be found at oceans, seas, rivers, lakes and even some large ponds. They are primarily composed of sand, but they can also contain soil, silt, gravel, cobble, shingle and boulders. Beaches are typically formed where fairly strong wave action deposits sand and there is a lack of strong currents to carry the sand away. The sand may be geological or biological in origin. Geological sand comes from the weathering of rocks; biological sand comes from the breakdown of the skeletons and shells of marine organisms. Most beaches have a mix of both types of sand.
Beaches are a very dynamic environment, capable of changing rapidly over short time periods (such as within a few hours) as a result of the action of waves. They can also change in size, shape and location over a period of decades or longer. The movement of sediment is controlled by the forces of the ocean, changes in sea level and the actions of streams, rivers, tidal inlets and gulfs.
There are three major types of beaches: free, rocky and barrier. The former is the familiar free beach where people swim and sunbathe. The latter is a broad strip of sand bordering a rocky or cliffy coast and often stretching for miles in some directions. The former type of beach has longshore drift, which moves sediment from places near the ocean’s mouth to points farther down the coast.
In addition to the movement of sediment by waves and longshore drift, beaches are shaped by the action of wind and currents. Wind can blow sand back to the beach, creating a dune or small hummocks. This can shift the slope of the beach, either making it more or less steep. The prevailing wind will also influence the movement of waves, determining whether they break or run up on the beach and whether they form ripples or dunes.
Beaches are a very important part of coastal ecosystems, supporting many different forms of life. They are also very popular with human beings and provide a variety of recreational activities, such as swimming, fishing, boating, windsurfing, diving and camping. In addition, they are a source of income and employment for local communities. The economic and social importance of beaches is reflected in the facilities that are provided, such as lifeguards, showers, shacks and food establishments. Beaches are often protected by coastal conservation laws. In some countries, they are also the sites of tourist resorts.