A beach is a sandy shoreline at the edge of an ocean or another body of water. Most beaches are found along coastlines, but they can also form at lakes, rivers, and ponds. Beaches are built up by the action of waves and currents. Waves carry sand and other sediment from further away, and they deposit it where their energy is low. This continuous process creates long and narrow beaches.
A wide variety of marine life lives on beaches. From tiny hermit crabs scurrying on the sand to sea anemones and starfish hanging out in tide pools at low tide, a beach is teeming with life.
In fact, some beaches are famous for the number of marine species they contain. The beaches of Australia, for example, are home to a variety of colorful fish and even some penguins!
Beaches can be found in many places around the world. Some are very rocky, while others have a lot of sand and gentle waves. Many are also heavily polluted, as sewage and other waste washes up on the shore. Beaches can even be toxic to humans.
The type of sand on a beach is an important factor in determining what types of organisms live there. Sand can be geological or biological in origin. Geological sand results from the weathering of rock, while biological sand is made up of the eroded remains of coral skeletons and shells of other marine plants and animals. Most beaches have a mix of both types of sand.
In addition to the natural processes that shape beaches, human activities can dramatically affect their appearance and character. In particular, buildings and other structures on or near a beach may contribute to erosion and the formation of new dunes.
Freak waves and storm surges can substantially alter a beach’s shape, position, and size within hours. The occurrence of these events makes beaches very dynamic and unpredictable, so they are often subject to intense public interest and concern.
A beach’s surface is covered by a variety of minor relief forms, including oscillation ripples, swash or rill furrows, and the well-known beach cusps (convex to seaward). In addition, sandbars may migrate across the surface of a beach, depending on the direction and intensity of waves. Increasing wave heights will shift the location of a beach bar to deeper water. Conversely, decreasing wave heights will cause a bar to move onshore.