A beach is a narrow, gently sloping strip of land that lies along a body of water, usually an ocean or a lake. Most beaches are covered with organic sediments, including sand, pebbles, rocks, and seashell fragments. These materials are deposited on the beach by wave action, wind, and other natural processes. Beaches also grow in size as waves erode the land near them and carry some of that material away into the ocean.
Many beaches are polluted, with debris, waste from inland sources, and raw sewage washing ashore after storms or through drainage pipes. Beach erosion is also accelerated by animals that eat coral and work it into small pieces in their digestive tracts.
Beaches are constantly changing, with new materials being brought to the surface and old materials being washed away. The sand at some beaches, for example, is made up mainly of quartz, while in others it is more feldspars or even heavier minerals such as micas. Beaches that are lined with coral reefs have a different type of sand – primarily calcium carbonate, formed by the skeletons of dead marine organisms.
Sand is the most common beach material, but rock and pebbles may also form parts of a beach. A beach may be covered by other organic matter as well, such as algae and seaweed. Beaches are also home to a wide variety of plants, animals, and insects. Birds and fish lay their eggs on ocean beaches, while crabs, shellfish, and other marine creatures live and feed in the sand and water.
Most beaches are a result of erosion, which slowly wears away at the land near the water’s edge. Erosion is accelerated by wave and wind action, as well as the movement of the seafloor beneath the beach. Beach erosion may also be aided by the presence of dense vegetation. Established plant species tend to absorb rainfall reducing the speed of erosion and holding particles in suspension for longer periods of time. Clearing or destroying such vegetation increases the speed of erosion and allows particles to be carried further ashore.
The overall effect of beach erosion is that the sand that originally covered a stretch of coastline moves south along the coast, sometimes to distances far from where it began. This process is called longshore drift. Beach erosion is less pronounced on the Pacific than on the Atlantic coast of North America, because the swells that reach these shores come from the west.
A sandbar is an isolated island of sand that rises out of the water and is separated from the surrounding coastline by a gulf or cove. It can be formed by ocean currents, sand transport by water, or the collapse of a cliff or other geologic feature. Many sandbars are used for recreational activities, such as fishing and swimming. Some are protected because of their delicate ecosystems. Other sandbars are popular spots for boating. In such cases, it is important to follow rules and regulations for boating safety, including never drinking while driving, and not littering.