Landforms of Deposition

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  • Deposition Landforms
    • Bars
      • 2. Alternatively, a sandbank can develop offshore and be moved towards the coast by wind and waves until it joins the mainland
      • 1.       A spit grows all the way across a bay due to longshore drift running parallel to the shore
      • 3. A lagoon is created behind the bar by the trapped water, and over time can become a salt marsh or infilled by deposition.
    • Dunes
      • 3. Hardy plants (pioneers) such as marram grass grow, stabilising the dunes, resulting in low, hummocky dunes.
      • 2.The sand becomes trapped by obstacles such as pebbles, which develop into small unstable embryo dunes
      • 4. Height increases, making dunes beyond reach of high storm tides. These are initially yellow as they contain little organic matter, but as colonisation increases, humus is added to the sand, turning them grey. Levels of nutrients increases, meaning higher plant growth.
      • 1. Dry sand is blown up onto the beach by saltation and the wind.
      • 5. Dune Slacks develop, which are depressions where the water table is near the surface, creating damp conditions, allowing reeds to grow.
    • Berms, Runnels and Cusps
      • Runnels: Depressions in the sand created by waves breaking, the backwash drags some of the sediment back into the sea.
      • Cusp: Semi-circular depressions formed when waves break directly onto the beach, found when there's a sudden change in gradient caused by sediment change.
      • Berms: formed as a result of constructive waves, and sand and shingle being slowly moved up the beach. This gradually increases the gradient of the beach, and a series of ridges marking the successively lower high tides as the cycle goes from spring to neap.
    • Salt Marshes
      • 1. Mudflats are formed by deposition in the calm water behind a spit, increasing friction and slowing waves down.
      • 2. Pioneer plants colonise the area, known as halophytes e.g glasswort. This allows other plants such as sea aster to colonise the mudflats and contribute humus to the soil.
      • 3. The vegetation slows waves further, leading to higher mudflats, allowing trees and reeds to grow. The land is now rarely covered by the sea.
    • Spits
      • 1. Spits are formed in sheltered and shallow waters created by a headland, meaning sediment is deposited due to low energy transported by longshore drift.
      • 2. Finer material is transported to the end of the spit and begins to block the deep centre while the large material is deposited close to the headland.
      • 3. The end of the spit curves inland due to wave refraction in addition to the dominant wind changing the direction of the longshore drift. Storms can break through the spit, creating a hole, allowing the waves to erode the material away.


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