geography DPR 3

• Constructive Wave


  • Smaller wave height
  • Less frequent
  • Strong swash moves sediment up the beach
  • Weak backwash carries away little sediment
  • Results in a gentler beach profile
• Destructive Wave


  • Larger wave height
  • More frequent
  • Strong backwash carries away lots of sediment
  • Weak swash moves little sediment up the beach
  • Steep angle of strike scours material away, resulting in steep beaches
• Waves


  Ripples in the sea caused by the transfer of energy from wind blowing over the surface of the sea
• Factors affecting wave size

  • Wind speed
  • Length of time wind has been blowing
  • Fetch (distance over water the wind has blown)
• Coasts are constantly changing due to waves, weathering, erosion, transportation, and deposition
• Harder rocks(like granite and limestone)


  Erode slowly
• Softer rocks (like clay)


  Erode quickly
• Types of Erosion


  • Abrasion: Waves smash rocks against cliff surfaces, wearing them away (the "sandpaper effect")
  • Hydraulic Action: Air trapped in cracks is compressed by waves, enlarging cracks and breaking away cliff pieces
  • Attrition: Rocks transported by the sea knock against each other, becoming smaller and more rounded
  • Solution: Slightly acidic sea water dissolves cliffs like limestone or chalk
• Types of Weathering

  • Chemical Weathering: Rainwater and seawater can be weak acids, dissolving rocks such as limestone or chalk
  • Physical Weathering (Freeze-thaw): Water enters cracks, freezes and expands, widening the crack. Melting ice goes deeper into the crack, repeating the process
  • Biological Weathering: Plant roots enter small cracks in rocks. As plants grow, cracks enlarge, causing the rock to break apart
• Longshore Drift

  1. the prevailing wind brings waves into the beach at an angle
  2. this carries sediment up the beach at an angle (swash)
  3. the sediment is pulled back out to sea at 90 degrees due to gravity (backwash)
  4. this process is repeated and sediment is moved along the beach
  5. eventually there is something meaning that the waves lose energy e.g. groyne or headland
• Formation of a Spit

  1. Material is moved along the beach in a zigzag pattern, by longshore drift, in the direction of the prevailing wind

  2. Coastline changes direction

  3. Material is deposited in shallow, calm water to form a spit

  4. A spit curves with the change of wind direction
• CASS (caves, arches, stacks and stumps)

  1. Large crack opened up by hydraulic action

  2. The crack grows into a cave by hydraulic action and abrasion

  3. The cave becomes larger

  4. The cave breaks through the headland forming a natural arch

  5. The arch is eroded and collapses. talk about weathering process e.g. biological - plant roots grow in small cracks in the rock these plants them grow and the cracks get larger causing rock to break away

  6. This leaves a tall rock stack

  7. The stack is eroded forming a stump
• Headlands and bays are caused by alternating lines of hard rock and soft rock because soft rock erodes faster than hard rock where there is a line of soft rock, it is eroded more so a bay is formed. But when there is a line of hard rock, it erodes slower than soft rock, so it is eroded less forming a headland.
• Formation of a wave-cut platform

  1. The sea attacks a weakness in the base of the cliff. For example, this could be a joint in chalk

  2. A wave-cut notch is created by erosional processes such as hydraulic action and abrasion

  3. As the notch becomes larger, the cliff becomes unstable and collapses as the result of gravity

  4. The cliff retreats inland

  5. The material from the collapsed cliff face is eroded and transported away. This leaves a wave-cut platform

  6. The process repeats over time