AQA AS Geography Coasts: Mindmap 4

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  • Physical geography
    • Landforms and landscapes of coastal erosion
      • Cliffs and wave cut platforms
        • Formation: Sea attaks lower part of the cliff, causing a wave cut notch to form. This then causes the rock above to become unstable and collapse.
      • Caves, arches and stacks and stumps
    • Landforms and landscapes of coastal deposition
      • Beaches
        • Formation: material from elsewhere is eroded and is then deposited, gradually forming a beach.
      • Simple and compound spits
        • Formation: Longshore drift moves sediment along coastline. Spit develops a hook as wind direction changes.
      • Tombolos
        • Formation: wave diffraction and refraction. Waves near an island slow down in shallow water, causing them to bend and longshore drift to occur. Eventually, a spit forms which then connects to the mainland to the island,.
      • Offshore bars
        • Formation: When the waves approach a gently sloping coast , friction between the waves and the sea bed causes the waves to break at some distance from the coast.Over time, more materials  are built up parallel to the coast to form ridge of sand called offshore bar.
      • Barrier beaches
        • Formation: Barrier beaches are formed where spits are joined to the mainland at both ends, trapping water behind in a lagoon
      • Barrier islands (long, thin islands that are separated from the mainland by a bay, lagoon or marsh. They're separated from each other by tidal inlets.
        • Formation: there are 3 main theories for their formation:  offshore bar, spit accretion, and submergence.
          • Spit accretion: when spits form and are then cut off from the mainland.
      • Sand dunes
        • Formation: sand gets blown up the beach and trapped in sheltered areas. It then build up, forming sand dunes.
      • Factors affecting formation: Erosion elsewhere on coast, depth of water, constructive waves, wind strength and direction.
      • Inputs: sediment. Processes: longshore drift and deposition Outputs: depositional landforms.
      • Bars
        • Formation: longshore drift moves material along the coastline. A spit forms as the sediment is deposited. The spit then grows across the mouth of the river/bay.
    • Swash aligned beaches: form in areas of low energy such as bays that are influenced by waves arriving parallel to the shore. This leads to little sideways transfer of material.
      • energy decrease; dissipation; deposition.
    • Drift aligned beaches: form when waves approach at an angle. Longshore drift moves the sediment. The sediment is naturally sorted as finer particles are more likely to be carried further down the beach and become more rounded.
      • Waves at an angle; longshore drift; prevailing winds.
    • Beach forms
      • Berms: a ridge or plateau on the beach formed by the deposition of beach material.
      • Cusp: cresecent shaped becah formations with graded sediment.
      • Runnel: dips in foreshore area of beach between ridges.
    • Beach profiles
      • Larger pebbles tend to be nearer top of beach (strong swash). Pebbles at base tend to be more rounded (attrition and abrasion).
      • Profiles are steeper in summer when waves are more constructive.

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