A beach is a strip of sedimentary land that extends along the shoreline of an ocean, gulf, lagoon, bay, or estuary. It may consist of rock fragments, sand, or mud (a mixture of sand and clay). The composition of beaches depends on the nature and quantity of sediments upstream of the beach, the speed of flow and turbidity of water and wind, and the coastal processes involved.
A sandbar is a sand ridge that develops in the sand on a beach. It is usually formed when currents from the coast meet currents from the offshore.
Sand bars are not permanent and often disappear at low tide. These sandbars can be a fun place to swim or go for a walk at low tide. They also have their own distinct charm, and are a popular hangout spot for tourists.
Wave action destroys a beach and builds it back up within an hour or so depending on the type of wave and its speed. This is called beach erosion and can cause temporary changes in the size, shape, and density of a beach that are very different from those that occurred when the beach was first formed.
The beach profile varies greatly from one area to another, especially in temperate areas where summer is characterised by calmer seas and longer periods between breaking waves. In these regions, the beach profile is higher in summer and lower in winter. In the winter, sand is pushed further inland by onshore winds and may form dunes.
Several types of beaches exist, including the cliff beach, the free beach, and the barrier beach. The cliff beach occurs at the margin of a rocky or cliffy coast; the free beach consists of the outer margin of a tidal marsh and is separated from the sea by a narrow sand barrier; and the barrier beach is a very rare feature and consists of a series of long tidal barriers that separate lagoons from the open ocean.
Most beaches have a beach terrace, created by the swash of waves that sweep over the shore. This terrace is inclined seaward, and a lower terrace below it may be developed as well. In some coastal areas, a tidal pool forms beneath the terrace. In some areas, the tidal pool is covered by a submarine beach.
Some coastal communities pump sand onto beaches to improve them for the benefit of visitors. These practices are sometimes referred to as beach nourishment, and they can be done in order to protect beaches that are vulnerable to erosion or for commercial purposes.
A beach is an important part of the landscape for many species, as it provides habitat for birds and other small animals. For example, sea turtles lay their eggs on beaches and other marine creatures feed on materials left behind by the waves.
In some parts of the world, beaches are protected by national parks and other protected areas. In others, the beaches are maintained by local governments or private businesses.