A beach is a landform that lies along the edge of a body of water, usually an ocean but also lakes and rivers. Its shoreline is comprised of loose materials such as sand, pebbles, rocks and seashell fragments, which are continually eroded and deposited by waves. The resulting landscape creates unique ecosystems that are home to an array of marine species.
Coastal erosion and sediment transport are ongoing processes that shape beaches, which in turn affect the surrounding environment and people’s activities. Beaches can be found all over the world, and are a popular destination for people seeking sun, sand and water. They provide opportunities for recreation such as swimming, surfing and building sand castles. They also support a variety of wildlife and plant communities, as well as provide vital habitat for birds and other organisms.
The most common feature of a beach is the sand that covers it. This material comes from the breakdown of larger rocks and shells by waves, as well as from other sources such as wind-blown drift. Beaches can also be composed of gravel, cobble, shingle and other coarse sediments that have been moved by currents.
Beaches are dynamic, changing with the seasons and often with a particular storm event. Waves erode and deposit sand, creating wide beaches in the summer that are narrower and steeper in the winter. Beaches can also become dotted with sandbars, which are narrow areas of sand and sediment that extend from the beach. These can be caused by longshore drift, wind-blown sand deposition or the movement of sediments from offshore sandbanks.
A sandbar is a landform that extends from the shoreline at low tide. The size of a sandbar depends on the frequency and duration of waves, the strength of the prevailing winds and the amount of material available for erosion. They can range in size from a small island to large marine deposits extending for hundreds of kilometers along a coast, which are sometimes called barrier islands.
Rip currents, which are strong offshore-directed currents, occur when high incident waves break over nearshore sandbars and discharge seawater through narrow gaps between the bars. These currents are dangerous for swimmers.
Beach pollution is a major problem that can harm wildlife, including birds and marine mammals. Plastic waste can choke seabirds and tangle marine mammals in ropes or twine. Leaving trash behind on the beach can prevent algae and sea plants from growing, and it can prevent animals that live in tide pools, such as sea anemones or sea stars, from finding nutrients. Getting involved in beach cleanups and helping to reduce pollution is an important way to protect beaches.