Geography- Coastal Landforms

• What's water mainly generated by

  • A2: wind
• Friction between wind and water transfers energy from the wind to the water
• Fetch


  The distance of open water the wind blows over
• Strength


  How powerful the wind is, determined by the difference in pressure
• Duration


  How long the wind has been blowing
• Wave height


  The distance from the peak to the wave trough
• Wave length


  Distance from one crest to another
• Wave frequency


  The number of waves that pass over a specific point over a given time
• Constructive waves


  • Low wave height
  • Build up the beach due to strong swash and weak backwash
• Destructive waves


  • High wave height
  • Break down the beach due to strong backwash and weak swash
• 2. Impact on beach morphology

  •Beaches formed from loose material

  • waves alter beach morphology

  (Other factors altering beach morphology) — size and shape of beach material, coastal management

  beach morphology is…

  steeper during summer, gentler during winter

  storm berms- formed when destructive waves travel further up the beach and deposit material there

  offshore ridges- formed when destructive waves erode material and deposit it offshore
• 3.factors affecting erosion

  • wave type

  • lithology

  • size and shape of waves

  Type, size and shape of waves affect seasonal changes in their erosion rates

  more during winter, less during summer.

  lithology influences rate of erosion. more weaknesses in rocks= faster erosion

  more resistant rocks = slower erosion
• 5.Formation of a Spit

  1. Longshore drift

  2. Sediment transported by waves along a coastline at an angle due to prevailing wind in a zig zag movement

  3. Coastline changes direction, waves can no longer carry the sediment due to lack of energy and they deposit it

  4. Build up of deposited sediment out to sea or an estuary results in a spit
• Spit


  • Extended stretch of sand or shingle that extends out to sea from the shore
  • Often have a curve or hooks at the end due to secondary prevailing wind
• When a spit forms

  A salt marsh may develop in the sheltered area behind the spit
• Formation of Tombolo


  1. Spit forms across an estuary

  2. spit stretches until it meets an island and joins it to the mainland
• Bar

  • Raised ridge of sediment away from the shore
  • Forms where sediment level is high, and the sea's shallow
  • Bars that form as spits form at the opposite side of a headland, and extend to join 2 headlands.
  • also known as barrier beaches
• when Barrier beach forms what happens

  Traps water behind the barrier beach - a lagoon
• Sand bars can also form offshore due to the action of breaking waves
• Picture of a Bar

  visual of the formation of a bar

  
• Picture of a tombolo

  Visual of a Tombolo

  
• erosional landforms 


  caves, arches, stacks and stumps:

  • occurs on pinnacle headlands
  • marine erosion widens faults in the base of the headland.
  • wave refraction concentrates wave energy onto the headland, can contribute to their formation
  • joints in the headland are susceptible to erosion by HA
  • overtime, the joints widen forming a cave which is enlarged by HA and AB
  • eventually erosion cuts through headland -> arch
  • roof of cave collapses due to lack of support and gravity-> stack
  • stack erodes via weathering, AB, HA -> stump
  • EXAMPLES: OLD HARRY, OLD HARRY’s WIFE
• Erosional landforms 2


  wave cut notch and platform: