A beach is a landform alongside a body of water that consists of loose particles of rock or sediment, such as sand, gravel, shingle and pebbles. The nature of a beach depends on the source of the material, wave action, weather and climate. The particles may come from mechanical erosion of eroded rocks offshore or by saltation (a bouncing movement of large particles). Beach material can also be derived from biological sources, such as fragments of shells, corals and calcified algae. Beaches are most common on rocky coastlines, but they can occur elsewhere, including in lakes, rivers and oceans.
Many beaches play significant social and economic roles, supporting tourism industries and providing recreational opportunities for people in coastal communities. Beaches can be visited for swimming, walking, picnicking and sunbathing. Some are used as launching sites for boats, yachts and windsurfers. Many beaches have associated infrastructure for these activities, such as lifeguarding posts and changing rooms. Some beaches have hotels, restaurants and bars, either on the beach or just a short distance away.
The term beach often refers to the sandy area near the water line, but the surface of a beach can consist of any granular material. Typically, the material is composed of sand but can be of any size, from clay and silt to cobbles and even boulders. Beaches can be very wide or narrow, with steep or gentle slopes. Some are almost flat while others have a considerable amount of shell content. The slope of a beach changes over time due to invisible forces that work on the sand grains.
As a beach forms, the material is arranged into a ridge or berm that rises above the water line at low tide. At the top of this berm is the crest; a little further seaward, there may be a trough or more gently sloping face called the long shore drift. This long-shore drift is caused by the combined effects of ocean currents, wind direction, tidal movements and oblique wave action on the coast.
If the period between wave crests is long, fine sediments that are held in suspension will be compacted and more resistant to erosion than uncompacted particles. Conversely, if the period between wave crests is short, the sand will be swept or carried further out to sea.
Some beaches are fossil beaches, preserved from an ancient sea by a change in the level of the surrounding seabed. These beaches can be seen along parts of the coastline of the United States, Europe and other countries that were once part of an ancient sea. Many of these beaches are now in the vicinity of urban areas, and they have been shaped and reshaped by human activity. One example is the Brighton beach in England, which developed as a resort during the 19th century when the fashionable practice of sea bathing was introduced. The resort received royal patronage from King George IV and became famous for its upper-class leisure activities.