Why does deposition occur along the coast

Some eroded material ends up caught up within the waves and is carried by the sea along the coastline in cells known as littoral cells. Material is carried along the shore in a zigzag fashion by waves as they swash material up the beach at an angle and backwash material down the beach at a right angle.

The angle of swash is determined by the prevailing wind the dominant or main direction in which the wind blows. Wherever there is a break in the coastline e. This is because there are often counter currents and a loss in velocity, so material is dropped or deposited. Eventually this material builds up out into sea to form a spit.

As seen in the picture opposite of Spurn Head. The spit often curves inwards towards the land as a result of the prevailing wind directing the waves which push the sediment in towards the shore. The coasts of the United States along the Atlantic and the Gulf of Mexico have not seen significant tectonic activity in a few hundred million years, and except in the northeast, have not experienced post-glacial uplift. These areas have relatively little topographic relief, and there is now minimal erosion of coastal bedrock.

On coasts that are dominated by depositional processes, most of the sediment being deposited typically comes from large rivers. There are no large rivers bringing sandy sediments to the west coast of Vancouver Island, but there are still long and wide sandy beaches there. In this area, most of the sand comes from glaciofluvial sand deposits situated along the shore behind the beach, and some comes from the erosion of the rocks on the headlands.

The components of a typical beach are shown in Figure On a sandy marine beach, the beach face is the area between the low and high tide levels. A berm is a flatter region beyond the reach of high tides; this area stays dry except during large storms. Most beaches go through a seasonal cycle because conditions change from summer to winter. In summer, sea conditions are relatively calm with long-wavelength, low-amplitude waves generated by distant winds.

Winter conditions are rougher, with shorter-wavelength, higher-amplitude waves caused by strong local winds. As shown in Figure The gentler waves of summer gradually push this sand back toward the shore, creating a wider and flatter beach. The evolution of sandy depositional features on sea coasts is primarily influenced by waves and currents, especially longshore currents. As sediment is transported along a shore, either it is deposited on beaches, or it creates other depositional features.

A spit , for example is an elongated sandy deposit that extends out into open water in the direction of a longshore current. Deposition happens when the swash is stronger than the backwash and is associated with constructive waves. Where does coastal deposition happen? Deposition creates a range of landforms. You can find out more on the depositional landform geotopic. Swell Coastal Deposition What is coastal deposition? Online Activities [Online activities]: n Activities related to this topic.

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