OCR Nationals Spec. B - Coasts

Paper 1 - Coasts Question

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Four Processes of Erosion

  • Hydraulic Action - Force of waves which cause the cliffs to crack, break apart and corrode.
  • Abrasion - Powerful waves pick up stones and throw them against the base of a cliff which attacks the cliff over time.
  • Attrition - Stones smash into each other and break apart as the sea carries them. They slowly get smaller and rounder.
  • Corrosion/Solution - Chemicals in a sea dissolve rocks such as chalk and limestone.
  • 
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Destructive Waves

  • High and steep
  • Backwash> swash (Materials removed from the coast)
  • Factors that affect the size and power:
    • Wind - Strong Wind = large powerful waves
    • Fetch - Strong Fetch = bigger and more powerful waves.
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Constructive Waves

  • Deposit more material than they erode
  • Low and long
  • Swash > backwash
    • swash carries material to a coast
    • Backwash doesn't take a lot of material back down to coast = deposited
  • Weaker winds and shorter fetch than destructive waves.
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Wave Cut Platform

  • Waves attack the base of the cliff
  • Cliff under cot and wave cut notch forms, this enlarges as erosion continues, cliff above notch becomes unstable and collapses.
  • Collapsed material is washed away and a new wave cut notch forms.
  • Repeated collapsing results in cliff retreating.
  • Wave cut platform is the platform left behind as the cliff retreats.
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Rate of retreat

  • soft rock = quick retreat

 

  • More Vegetation = more stable = less erosion = slow retreat

 

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Headlands

·         Resistant rocks with cracks – enlarged by waves crashing

·         Repeated erosion and enlargement of cracks cause a CAVE to form

·         Erosion breaks through the headland forming an ARCH

·         Rock supporting arch wears way forming a STACK

·         Stack worn away to give a STUMP which can be covered by high tides

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Longshore Drift

·         Material is transported along coasts

·     Waves follow the direction of the prevailing wind

·    Hit coast as an oblique angle

·    Swash carries material up the beach in the same direction as the wind

·    Backwash carries material down the beach at right angle, back towards the sea

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Spit

·         Beaches that stick out in the sea. They’re joined to the coast at on end

·         Form at sharp bends in the coastline

·         LSD transports sand past the bend and deposits it in the sea

·         Behind the spit it is a sheltered area which is protected from waves

·         The sheltered area accumulates a lot of material and over time becomes salt marsh

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Bars

·         Spit connects with another bit of mainland

·         Bar cuts off the bay between the headland and the sea

·         Logoon can form behind the bar

·         Bar that connects the shore to an island is called a tombolo

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Economic Reasons to Protect Coastline

·         Loss of tourism

 

·         Businesses near cliff – collapse – damage – money – shut down

 

·         Agricultural land – damage – poor soil fertility

 

·         Property prices – decrease – can’t insure it

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Social Reasons to protect Coastlines

·         Death

 

·         Water supplies polluted

 

·         Loss of homes (homeless)

 

·         Loss of jobs

 

·         Damage of roads

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Enviromental Reasons to protect Coastlines

· High salt content = kill organisms

 

·  Force of flood water = uproots trees and plants

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Coastal Protection

Sea Wall

  • reflects waves
  • Prevents erosion, barrier to flooding
  • Expensive, strong backwash = erosion.

Rip Rap

  • Boulders
  • absorb wave energy
  • Moved around by strong waves

Groynes

  • Right angle, trap materials from LSD
  • wider beaches = slower waves
  • Starve beach as narrow, which means poor protection = erosion
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Coastal Protection

Rip Rap Armour -

  • Foot of Cliff
  • Absorb wave energy
  • Expensive. Strong BW = erosion

Gabions

  • rock filled cages
  • Absorb wave energy
  • Not Attractive

Beach Nourishment

  • Sand added to the beach
  • wider beaches = slower waves
  • Expensive and needs reacting
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Comments

rocky

very good info

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