Beaches are fascinating natural features that form through a complex process of many factors over time. They are most often found at the sea’s edge, but they can also occur along lakes and rivers. In addition, beaches can be formed from other materials, such as sand or gravel.
The word beach is often thought to be exclusively associated with the sea, but this is not entirely true. In fact, beaches can be found in many bodies of water. Beaches are usually characterized by the accumulation of loose sediment like sand and pebbles along the shoreline. They are also often popular for recreation and play important economic and cultural roles in the communities that they serve. In addition, beaches can also have a number of infrastructure elements to support the recreational activities that take place there, including lifeguards, changing rooms, showers, shacks and bars.
Sand is the material that most often makes up a beach, but other materials can also be present. These may include gravel, shingle, silt, clay or other finely grained materials. They can be deposited as a result of weathering, which is the breaking down of rocks into smaller particles that can then be eroded by waves or currents. Sand may also be transported and deposited as a result of tidal action, erosion of offshore headlands or slumping, or from coral reefs.
The composition of a beach will vary greatly depending on the material present and the conditions at a site. The sand of a tropical beach is often powdery white because it is made from the skeletons of tiny animals called coral. Other beaches, such as those of islands created by volcanoes, can be black because they are formed from the igneous rock olivine. Beaches can also be a variety of colors, such as green or red, because they can be composed of different minerals.
A beach’s profile is a key factor in how it looks and feels. At low tide, a beach may be flat and broad with a gentle slope and a line of beach ridges or berms running down to the water’s edge. Alternatively, it may be steep and narrow with a sharp frontal beach slope. The profile of a beach may be affected by the tidal action, the amount of material that has been deposited, and the type of sediment present.
Beaches can change dramatically seasonally, as waves erode and transport sand back up the coast or to the inland areas. They can also be influenced by the presence of sandbars, which are narrow areas of sand and other material that extend offshore from a beach. The sandbars of a beach may be gaining sand (accreting) or losing it (eroding). They are usually formed by the swirling turbulence created when waves break off a beach. The sand in the trough of a wave is deposited on the offshore flank of the trough, while sand suspended in the backwash and in rip currents as well as sand moving shoreward from deeper waters are added to the bar.