A beach is the land along a body of water, usually made up of loose particles such as sand, gravel, cobbles, pebbles and shells. These particles build up on a beach during periods of accretion and move away from it during periods of erosion. As a result, beaches are never stationary for long. This makes them dynamic, and fascinating to observe.
Beaches are formed by the interaction of many natural and human factors over a long period of time. The process begins with weathering, which is the slow wearing down of rocks by wind and waves. These rocks then may get carried by rivers or streams to the coast, where they are deposited on the beach by flowing water. Beaches are also shaped by wave action, which can erode and deposition of sand on the seafloor.
In addition to forming dunes and beach ridges, beaches can have features such as seagrass beds, lagoons and marshes. The size and shape of a beach can vary dramatically, depending on its location, as well as the underlying geology. For example, beaches in low-energy environments tend to have wider and gentler slopes than beaches in high-energy environments.
The most important feature of a beach is its shoreline, which is the line at which the land meets the water. This line may be the edge of a dune, a rock or cliff, or it may be an artificial feature such as a seawall or breakwater.
A beach also contains a zone called the foreshore and a zone called the backshore. The foreshore is the intertidal seaward portion of the beach. The foreshore is covered by the sea during most of the day and night, except during a storm or extremely high tides. The backshore is the dry land behind the foreshore, which is sometimes covered by a dune or seagrass berm.
Most beaches are composed of quartz sand, but these grains can come from many sources. Some are eroded bits of a rocky reef just offshore, others are from sand that has been washed downstream by a river or sand from a nearby sandbar. Beach sand can also be a mixture of materials, such as carbonate skeletons and shell fragments from coral.
Beaches are a natural habitat for fish, birds, insects and small animals that live in or near the water. They are also home to crabs, sea grasses and many other plants. Beaches are popular for recreation, and many have facilities such as lifeguards, showers, changing rooms and shacks.
Beaches can be a source of income for local communities, particularly in tourist areas. Some governments make all beaches public, while others allow private ownership of some or all of them. Regardless of ownership, however, most jurisdictions have laws governing public access to beaches, and signs often indicate where private beach property ends and the public’s right to use the beach begins. In some places, a public easement allows people to walk across privately owned land on the beach as long as they stay off private structures such as dunes or sandbars.