A beach is a narrow strip of land that extends along the shoreline of a body of water. It is a natural and man-made feature that is always changing. Beaches are made of a variety of materials including sand, gravel, cobbles, rock, and shell fragments. These materials accumulate on the beach during periods of accretion and move away from the beach during periods of erosion.
The formation of beaches depends on the geology of the region. Different rocks can produce beach materials in various colors such as black basalt, white quart, or red coral. Beaches also get their color from organic matter such as kelp or seaweed. Beaches may also contain sediment from eroded headlands or reefs offshore and even from the breakdown of a shipwreck.
A beach is not just a place to relax and enjoy the sun, it is home to many fascinating creatures. From tiny hermit crabs scurrying across the sand to colorful fish swimming in the waves, the beach is full of life. In addition, a visit to the beach is an opportunity to explore tide pools at low tide and discover starfish, sea anemones, and other incredible marine species.
The shape of a beach depends on the energy of wave and wind systems that are constantly moving sediment on the coast. Beaches with energetic systems will have rough and tumble coastlines as the waves break repeatedly against rocky shorelines. Beaches with gentle wave systems will have calmer coastlines with long periods between breaking wave crests that allow finer sediments to settle creating sandy beaches.
Wave and wind action can also erode beaches by undermining coastal headlands, shifting material down the beach and into the shallows. This can result in changes to the habitat as some species such as sea grasses and corals are deprived of light and nutrients. Beach nourishment activities must be carefully planned so that the new sediments can compact and stabilize before aggressive wave and wind action erodes them.
Other features of a beach can include sandbars that stretch out into the sea between waves. These are formed when a shoreward current meets a compensating downward bottom current in a trough or near the break point of waves. Other longshore bars can form further offshore where wave breaks leave a trail of sand behind that is carried by the surf and deposited as it recedes. Beaches are also characterized by spits and dunes that can be created by the accumulation of sediment over time. These features are sometimes used by animals and plants to protect themselves from the harshness of the seafront environment.