A beach is a strip of loose sediment, usually sand and sometimes gravel, that borders a rocky or cliffy coast. It forms over time as rocks are eroded and carried down to the shore by waves and currents. Beaches are a natural environment that is home to many species of plants and animals. Beaches are often popular recreation areas where people swim, sunbathe, build sand castles, and play games like volleyball.
The composition of a beach varies according to the types of rocks in the immediate vicinity and how much energy the surrounding sea has. A beach may consist of sand or finer material such as clay, silt, and pebbles. Coastal erosion from storms, slumping of headlands, and deposition from longshore drift can also change the composition of a beach.
Waves, wind, and currents scour the beach to create sand bars, which are submerged ridges of coarse or medium-sized sand. Bars are usually formed by the swirling turbulence of breaking waves that excavates a trough in the sandy beach. The sand then moves offshore and is deposited on the adjacent beach by backwash and rip currents. Sand from a nearby beach or sandbar, and sand suspended in the surf or carried in a current, may also add to the bar.
In addition to sand bars, beaches are characterized by minor relief features such as oscillation ripples, swash or rill furrows, and the well-known beach cusps (convex seaward). Occasionally, beaches are dismembered by the formation of groynes, a type of manmade barrier.
While a beach is typically associated with oceans, it can also occur along the shores of lakes and rivers. These are generally calmer environments and support different marine life than a beach at an ocean.
Humans are also active in the formation of beaches. Many communities use beach nourishment to replenish the sand lost from erosion, and seawalls are constructed to protect coastlines from waves and high tides. However, beach nourishment must be done carefully so that new sand and other materials are able to settle and compact before the intense wave and wind action of a beach erodes them.
The process of beach formation is very complex, and each beach is unique. Some are populated with shells and other marine debris from distant locations, while others are covered in garbage and litter. Reducing the amount of trash on a beach is an important way to protect wildlife. For example, birds can choke on plastic items that wash ashore and sea plants and animals can become tangled in ropes and twine. In addition, humans that leave behind trash on a beach are contaminating the water and soil, which can poison wildlife and damage the flora and fauna of the area. The best way to help protect beaches is to encourage beachgoers to remove trash and leave the animals and vegetation alone.