Geography Marine processes 10.3

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  • Created by: jodie.g
  • Created on: 23-05-18 19:09
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  • Marine processes
    • Coastal erosion
      • Hydraulic action
        • Destructive waves pound base of cliffs
        • causes repeated changes in air pressure as water is forced in and out of joints
        • Forward surge of water compresses air in he cracks and, as the wave retreats, there is an explosive effect
      • Abrasion
        • Destructive waves hurl sand and shingle at cliffs
        • the scratching and scraping of the rock surface is called abrasion
      • Attrition
        • Grinding down of load particles
        • pebbles collide during transport
        • wears away jagged edges to make rounded pebbles
      • Corrosion
        • dissolving of rocks such as chalk and limestone
    • Rate of erosion affected by...
      • Larger fetch-higher rate
      • Stronger wind-destructive waves-higher rate
      • No beach between the sea and cliffs-higher rate
      • headland juts out to sea-waves gain height-wave refraction-higher rate
      • Softer rocks-higher rate
      • Rock has more joints-higher rate
    • Material transported by waves
      • Transport onto beach
        • Larger and heavier the load, greater velocity needed for transport
        • Load is transported by waves
        • Lightest load is carried by suspension or saltated
        • Heavier load moved by traction
      • Transport along beach parallel to shore
        • Transported by longshore drift
        • Direction determined by prevailing wind
        • Swash surges up beach and backwash goes back down at right angle to the shore
    • Conditions causing deposition
      • Low energy sheltered bays where constructive waves are dominant
      • Large source of sediment updrift
      • Large expanses of flat beach so swash spread out over large area
      • Tidal material is trapped behind a spit
      • Engineered structures like groynes trap sediment on the updrift side

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