Beach

A beach is a landform that lies alongside a body of water and is made of loose particles. The material is usually rock fragments such as sand, gravel, shingle or pebbles, though it can also come from living sources such as mollusc shells or coralline algae. Sediment settles according to its density and the local wave action and weather, which gives each beach its own texture, colour and slope. Most beaches lie on coasts, where waves and currents deposit and rework sediment, but beaches also form beside lakes and rivers. Where wind conditions allow, a beach may be backed by coastal dunes that protect and renew it. Sandy beaches occupy about one third of the world coastlines, and they matter for recreation, tourism and wildlife such as nesting turtles and seabirds. Beaches are changed by erosion, storms, sea level rise and human activity, and are sometimes restored by beach nourishment.