During the summer, waves retrieve sand from sandbars and build the beach back up again.

Sandbars are narrow, exposed areas of sand and sediment just off the beach. This can sometimes erode beaches and create sandbars.

During the winter, storm winds toss sand into the air. Tides and weather can alter beaches every day, bringing new materials and taking away others. Tides and currents are the main way beaches are created, changed, and even destroyed, as the currents move sediment and debris from one place to another. Tides and ocean currents can carry sediment a few meters or hundreds of kilometers away. When the tide goes out, it takes some sediment with it. This sediment may contain sand, shells, seaweed, even marine organisms like crabs or sea anemones. As the tide comes in, for example, it deposits ocean sediment. Beach materials may travel long distances, carried by wind and waves. Huge boulders can be worn town to tiny grains of sand. The continual action of waves beating against a rocky cliff, for example, may cause some rocks to come loose. Over many years, water and wind wear away at the land. Most beach materials are the products of weathering and erosion. Materials such as sand, pebbles, rocks, and seashell fragments cover beaches. A beach is a narrow, gently sloping strip of land that lies along the edge of an ocean, lake, or river.

Dredge definition for kids