A beach is a narrow strip of land that stretches along the shoreline of a body of water. It usually consists of materials such as sand, gravel, pebbles, rock, and shells. A beach can also contain biological material such as the skeletal remains of marine organisms. The term beach is often used to refer only to ocean beaches, but the concept is more generally applicable to any sandy shoreline near a large body of water. Beaches are constantly changing as materials accumulate during periods of accretion and move away during periods of erosion.
A sandbar is an island of sand that forms offshore from a beach. It may be partly submerged under still water, or it may be exposed at low tide when a beach’s crest is at its lowest level. A sandbar is usually the result of the swirling turbulence of breaking waves creating an underwater trough in the beach’s sandy bottom. The trough is then filled with sand carried offshore by backwash and in rip currents, and with sand moved seaward from deeper water.
Coastal erosion is the gradual loss of land by wave action and wind. It is a natural process that occurs over long periods of time, although freak wave events such as tsunamis and tidal surges can significantly alter the shape and location of a beach within hours. Beaches that are protected by man-made structures such as seawalls tend to accrete, while those that are exposed to the full force of the waves and winds erode.
The surface of a beach is made of various materials, but sand is the most common. The sand on most beaches is of quartz origin, although some of the sand at tropical beaches contains feldspars and other minerals. In addition to sand, rocks and even bits of coral may be present on some beaches.
Beaches are often popular places for recreation, and they provide good swimming conditions when the water is warm. They can also serve as a boat landing site, and specialized boats called “beach craft” are designed to facilitate this purpose. Beaches are home to a variety of plants, and birds often gather on them to rest or roost.
Beaches are important habitats for crabs and other marine organisms. They are also a source of food for fish and other animals that feed on the sand and other materials that collect there. In addition, many species of molluscs lay their eggs on ocean beaches. Beaches are also a significant economic resource, providing employment for local residents and tourism opportunities for visitors. Beaches are especially attractive when they have fine white sand and clear water.