A beach is a landform alongside an ocean, lake or river that consists of loose particles such as sand, gravel, shingle and pebbles. They occur naturally in areas where wave and current action deposits and reworks sediments. The particles that make up a beach are often rock, but may also be biological in origin, such as mollusc shells and coralline algae. Beaches are commonly associated with the ocean, but they can be found along coastal lakes and rivers as well.
Beaches change every day, a result of tides and weather. Each time a wave washes up on the shore it transports a layer of sediment that contains sand, seaweed, shells and marine organisms. These materials are then deposited again when the wave recedes. Over a period of years, a beach builds up as the wave passes repeatedly along the coastline.
In addition to sand and other sediment, beaches may include other materials such as driftwood, rocks and sand dunes. They are also home to a diverse array of wildlife, including sea turtles, crabs and birds. They can also provide habitats for fish, squid and other invertebrates.
While waves are the primary force that shapes beaches, other natural and human activities can have a significant impact as well. For example, erosion of the rocks or coral reefs that form a coastline may reduce the amount of sand and other particles that wash into the water. This reduction can result in a loss of beach width and a steepening of the slope.
Some beaches, especially those near cities, are contaminated by pollutants such as raw sewage, garbage and chemical spills. These pollutants are carried to the coast by river and drainage system runoff, and sometimes by storms.
Beaches are popular recreational and cultural destinations, with many providing facilities such as lifeguards, showers, shacks and bars. However, if beach development is not carefully managed, the ecological value of the beach may be lost as the ecosystem that supports it is disrupted. For this reason, many governments are developing programs to manage beach development and protect the ecosystems they support.