physical geography

• Erosion

  Processes that wear away the Earth's surface
• Erosional processes

  • Solution (acids in water dissolve certain types of rock)
  • Abrasion (sediment is thrown against the cliff face as waves break, scraping it like sandpaper)
  • Hydraulic power (the force of waves hitting the cliff face, trapping air in the cracks)
• Erosional landforms

  • Wave cut platforms destructive waves erode between high and low tide, creating a wave cut notch. An overhang is formed above the notch due to increased deepness. Biological and chemical weathering occurs above the overhang. Rocks become weaker and fall into the sea and segments of rock collide in the ocean (attrition). Eventually becomes a wave cut platform.
• Groynes are used in coastal management to slow longshore drift
• Location of Isle of Wight

  Island of south England, English channel
• Reasons for rapid erosion in Isle of Wight

  • High energy waves located in the west, moderate north
  • Soft rocks such as clay (unstable coastal creation)
  • Direct direction of prevailing wind to cause destructive waves
• Coastal management techniques in Isle of Wight

  • Stepped sea wall to reduce floods/erosion (dissipates energy)
  • Rock armour to dissipate wave energy / make them low energy
  • Cliff drainage to remove excess water from clay cliffs to reduce landslides
  • Revetments to dissipate wave energy
• Coastal management techniques

  • Groynes (hard, to slow longshore drift)
  • Sea walls (hard, at cliff base/town, may be curved, slows longshore drift, reduces wave impact, expensive, short lifespan)
  • Managed retreat (soft, leaves land to erode, monitored, no structures)
  • Rock armour (hard, large boulders to dissipate wave energy, cheaper than wall, long lasting, specific areas)
  • Gabions (hard, small rocks in mesh cage to dissipate wave energy, dangerous?)
  • Dune regeneration (soft, maram grass holds sand together, attracts wildlife, damaged by people/weather)
  • Beach nourishment (soft, replaces material, not long lasting, expensive)
  • Beach re-profiling (soft, material moved, creates uneven beach, cheap, effective, limited lifespan)
• Mass movement processes

  • Rockfall (due to weathering, piles a scree at base)
  • Landslide (large chunks along bedding planes, susceptible to water)
• Types of weathering

  • Chemical (breaking down with chemical composition)
  • Mechanical (breaking down without chemicals)
  • Biological (nature breaks down material e.g. tree roots)
• sand dunes

  • Sand trapped around obstacles forms embryo dunes
  • Dunes develop and grow, gain organic matter and fix
  • Dunes move up beach and high water line
  • Depressions result in dune slacks
  • Moisture causes vegetation growth
  • Dune heath develops
• Longshore drift

  • Moves material along a beach
  • Direction is because of prevailing wind
  • Swash moves material onto the beach
  • Backwash returns to the ocean at a 90° angle
  • Debris is transported until it reaches a groyne
• Spit formation

  1. Sediment is deposited by longshore drift off the coastline when there is a change in the direction of the headland

  2. A spit is formed, longshore drift continues

  3. A change in wind direction causes a hook

  4. A salt marsh is formed due to sheltered stagnant water
• Headlands and bays: destructive waves erode less resistant rock (clay) to form bays, beaches and strong rock forms headlands.
• 1. Waves continuously break against the rock to cause cracks.
  2. Continuous crashing causes bigger cracks
  3. Repeated enlargement of cracks causes caves to form
  4. Waves cut through the headland to form an arch.
  5. Erosion wears away the rock until it collapses to form a stack.
  6. The stack is undercut and collapses leaving a stump which is covered by high tide).