How are erosion and deposition involved in forming a beach?

A beach typically has a source of insoluble inorganic materials, such as an offshore coral reef that provides abraded calcareous debris (sea shells, coral skeletons, hard body parts), a river, stream, or estuary that outflows suspended sediments, or an outcrop of rock that is eroded by strong waves.

The particles are carried and pushed along the shore from the source of the sediments to where they are eventually deposited by the waves; this process of swash and backwash, in which incoming waves alternately suspend and then deposit the sediment while moving it parallel to the shoreline, is known as "longshore drift." Depending on the energy state of the moving water, the beach could have large or small sediments. High-energy beaches (strong waves) have cobbles, pebbles, and granules, while low-energy beaches (small or no waves) have sand, mud, silt, or clay.

Heavy debris may be carried higher up the beach during high tide and piled up as thick berms; debris that does not make it high on the beach eventually gets re-suspended or washed out to sea again.

Erosion removes sediment from coastal areas, and deposition occurs when sediments are deposited onto the beach, forming sandbars, dunes, and beaches. Over time, the continual cycle of erosion and deposition shapes the coastline and creates beaches.

Erosion is involved in the formation of a beach through the process of wearing away rock, soil, or other materials from the coastline. Deposition, on the other hand, is the process by which sediment, carried by waves and currents, is deposited or laid down along the shoreline. Over time, the continuous cycle of erosion and deposition results in the accumulation of sand and other sediments, forming a beach.