A beach, also known as a shoreline or a strand, is a narrow strip of land where the sea, or other bodies of water (including freshwater), meets dry land. Most beaches are made of sand but may also contain rocks, pebbles and shell fragments. Beach sand is usually a mixture of quartz, feldspars and some heavier minerals such as micas. Beaches are constantly shifting due to wave action, currents and tidal changes. Freak waves or storm surges can substantially alter the shape and location of a beach within hours.
Sand is a natural resource and beaches are very important for recreation, providing a place where people can play and relax. They are often important habitats for wildlife such as birds, fish and marine mammals. Beaches also provide a wide variety of ecosystem services such as erosion control, dune stabilization and sediment transport. Many people also use beaches for fishing and hunting. Beaches are sometimes lined with residential and commercial development including hotels, restaurants, clubs and bars.
Most beaches are covered by a mixture of sand, pebbles and rock fragments with some areas of coarse, gritty sand and smaller deposits of silt and clay. The fine-grained materials, which are wet sand or mud, are weathered from larger rock formations that lie inland. The coarse-grained sand grains are carried by water and wind to the beach and deposited as a new layer on top of the older layer.
The sand on a beach has a crest and face, the latter being a slope leading to the water at low tide. The ridge of the sand at high tide is called a beach dune. This dune is comprised of a series of sand dunes with an interconnecting trough. The swirling turbulence of the surf excavates the trough and carries sand from deeper water to the beach. This sand is also added to the beach by sand suspended in the backwash and in rip currents.
Sands on tropical beaches tend to be softer and less dense than those in temperate regions. They are characterized by a high proportion of calcium carbonate, which is precipitated from the skeletal remains of marine plants and animals. The sand also contains silica. Beaches are often formed of such sand, and the best surfing spots occur on such sands as well.
Beach pollution includes any material that is deposited on the beach, or washed up onto it from elsewhere. This can include garbage, sewage, and other pollutants. The pollution can be harmful to beach-dwelling wildlife such as birds, sea gulls and marine mammals. It can also prevent sand and sea plants from growing, or interfere with the ability of some algae to get the nutrients they need to grow. People can help reduce beach pollution by not littering and removing trash from the beach. They should also avoid removing coral, seaweed and other living things from the beach. This can harm them, and it is against the law in some places.