Offshore bars form when sediment is transported on and off a beach. Destructive waves remove sediment from the beach and form the offshore bar.

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Onshore winds (winds blowing inland from the sea) cause the formation of sand dunes at the back of a beach. Sand is deposited by the wind around an object such as a rock, forming embryo dunes. Over time, vegetation such as marram grass stabilises the sand dunes forming foredunes. As the vegetation around the foredunes decomposes nutrients are released and soil begins to form. A wider range of plants are then able to colonise the dunes.

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A bar is created when there is a gap in the coastland with water in it. This could be a bay or a natural hollow in the coastland. The process of longshore drift occurs and this carries material across the front of the bay. Material is pushed up onto beaches at a 45-degree angle when the swash brings it onto the coastline. The backwash takes it back out towards the sea at a right angle to the coast. Through this process, the material is constantly moved along the coastline. The deposited material eventually joins up with the other side of the bay and a strip of deposited material blocks off the water in the bay. The area behind the newly formed bar is known as a lagoon.

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Beaches, sand dunes, spits and bars.

Find out more about landforms of coastal deposition.

Find out more about landforms of coastal deposition.