A beach is a landform that forms along the shore of an ocean, sea, lake or river. It consists of sediment, often consisting of sand, gravel or crushed seashells, that is deposited by waves and winds. A beach also may contain a variety of organic material. Beaches are frequently popular for recreation and play important economic roles, especially in coastal areas that have tourist economies.
A beach varies in size, shape and composition depending on the conditions at a specific time and place. For example, beaches subject to strong wind and wave action tend to have higher energy, coarser sediments and steeper slopes, while those that experience low wave activity have flatter surfaces with finer sand. Beaches with different mineral content are distinguished by the size of their particles and their tendency to concentrate heavy minerals between ripple crests.
In addition, the eroding nature of beaches is influenced by the amount of wave energy present. High energy conditions can cause significant erosion in a short period of time. This is why beach profile changes occur rapidly in high energy situations, as well as in storms and tropical cyclones.
On the other hand, sandy beaches that are sheltered from strong wind and wave action may be more stable over longer periods of time. This stability is largely due to the fact that waves do not wear away the surface of sand as quickly in calmer conditions.
Many beaches are important wildlife habitats. For example, piping plovers, black skimmers and roseate terns nest on them. Seals, sea lions and sea turtles also use beaches for resting or foraging. Crabs, clams, scallops, sand dollars and many other marine species live in the tidal zones of beaches. In addition, a wide variety of birds migrate over and around beaches during their annual cycles.
The net movement of sand from a beach is usually to the south. This occurs on both the West Coast and the East Coast, as waves that break in the surf zone push the sand southward toward a sandbank. This movement is called longshore drift.
A sandbar is a large sand accumulation that rises above the level of the surrounding water. A sandbar can be found at the mouth of a river or harbor, in a lagoon, as part of an ocean bank, in the middle of a body of water such as a bay or estuary or as an isolated island. Sandbars are formed when water carries sediments through the waves and currents, where the larger particles sink and build up over a period of time. The resulting sandbank is then visible at low tide. This type of sandbar is sometimes called a barrier bar. This is an excellent place for swimming, boating and fishing. It is also a refuge for birds and other marine life from the open waters.