A beach (also called a shoreline or strand) is where the ocean or any other body of water meets land. A beach can be made of any number of materials including sand, gravel, cobbles, rock or shells. A beach is never stationary for long as it moves back and forth along the coastline during periods of accretion or erosion.
The sand on a beach can come from geological sources or it may be biological in origin such as the break down of coral skeletons and shells from marine plants and animals. Often beaches contain both types of sand. Beaches can vary in size from a few meters to hundreds of kilometers in length. Some have a steep slope while others are very flat and sandy in nature. The sand on a beach is usually rounded from being rolled about by waves, but it can also have a rough texture or be quite dark in color depending upon the mineral content of the sand.
Many people are familiar with beaches as they are one of the most visible intersections of the terrestrial and marine environments. They are a place where people can play and relax and they are an important habitat for marine wildlife. Beaches are home to sea gulls, birds and mammals that lay their eggs and fish that feed on the plants that live in the sand. Beaches are also a very popular destination for human recreation such as walking, swimming, jogging, playing sports and sunbathing.
The ocean is a very large body of water that covers 70% of the Earth’s surface. It is salty and has a high mineral content. Beaches occur where any body of water, fresh or salt, meets land. Even lakes and ponds have beaches. Beaches are made of sand, rocks, dirt (mud) or man-made materials.
Beaches form in places where the prevailing wind and wave conditions are favorable for sedimentation. There is generally a lack of strong currents in the water which keeps the sand from being carried away by the prevailing winds and waves. Beaches are often characterized by the presence of a large tidal range which contributes to the formation of dunes.
The structure of a beach is determined by the shape and structure of the sand, the prevailing winds and wave conditions, and the amount of runoff from the surrounding land. A beach that is constantly changing can be characterized by the presence of sand dunes that are moving back and forth, a line of surf with breaking waves at its point, and a low-tide zone.
A well-stabilized beach reflects the fact that its foreshore area has been deposited by a period of accretion. Conversely, a poorly-stabilized beach is often characterized by an eroded coastline. Freak events such as tsunamis, tidal surges and storm surges can dramatically alter the shape and profile of a beach within hours or days. In order to stabilize a beach it is necessary to build structures such as groynes, breakwaters and sand traps. Beach nourishment activities must be carefully controlled so that the new sediments are able to compact and stabilize before the aggressive effects of wind and wave action can cause scouring or erosion. Beach pollution such as trash, litter and discarded shells can have negative impacts on marine life. Birds can choke on plastic debris and marine mammals can become entangled in ropes or twine. The removal of marine vegetation from a beach can prevent algae and sea plants from being able to grow and animals that live in the tide pools, such as sea anemones and sea stars, from finding food.