Waves

• What is swash?


  Water that washes up the beach
• What is backwash?

  Water that washes back into the sea
• How do waves form?

  • By wind blowing over the sea.
  • Frictional drag exerted by winds causes tiny ripples to form in the water that develop into waves.
• Fetch - the distance that wave-generating winds blow across the water.
• The longer the fetch, the bigger the wave
• Crest - the highest point on a wave
• Wavelength - the horizontal distance between two successive crests
• Trough - the low point on a wave
• Which factors affect the size of waves?

  • Weather on a particular day
  • Strength on the wind - stonger wind means more energy transferred to water, therefore more / larger waves
  • Direction a coastline faces (prevailing winds)
  • The distance that the wind can blow across the sea before it reaches the coast (the fetch)
• Prevailing Winds - A surface wind that blows predominantly from a particular direction.
• Why do cliffs collapse?

  Weathering
• Weathering - the weakening or decay of rock caused by weather, plants, and animals
• Mechanical weathering?


  The disintegration of rock, e.g freeze thaw weathering
• What is freeze thaw weathering?

  A type of mechanical weathering
• Describe the process of freeze thaw weathering

  1. Water collects in cracks of rock
  2. At night, water freezes and expands, making cracks larger
  3. When temperature rises again, ice thaws and water seeps deeper into rock
  4. Repeated freezing and thawing causes rock fragments to break off, collecting at cliff foot as scree
• What is scree?


  Discarded rock fragments that collect at the cliff foot after freeze-thaw weathering
• What is chemical weathering?


  Weathering caused by chemical changes
• Describe the process of carbonation

  1. Rainwater absorbs CO2 from air, becoming slightly acidic.
  2. Contact with alkaline rocks, such as limestone, produces a chemical reaction causing rock to disintegrate
• What is biological weathering?

  Weathering caused by the actions of flora and fauna.
• Describe an example of biological weathering

  • Plant roots growing in the cracks of rocks
  • Animals (e.g rabbit) burrowing into weak rocks
• What is mass movement?

  The downward movement of weathered material and rock under the influence of gravity.
• What is rock fall?

  A type of mass movement where rock breaks away from cliff face (usually by freeze-thaw weathering) and collects at cliff foot as scree
• What is a landslide?

  A type of mass movement where rocks detach and slide downhill.
• What is mudflow?


  A type of mass movement where saturated soil and weak rock flows downhill.
• What is rotational slip?

  A type of mass movement where a slump of saturated soil and weak rock is along a curved surface
• Name the four processes of coastal erosion

  Solution, abrasion, hydraulic action, attrition
• Solution - Dissolving of soluble chemicals in rock, e.g limestone
• Abrasion - where waves throw sediment against base of the cliff and the land is worn away.
• Attrition - Rock fragments carried by the sea knock against eachother becoming more smaller / rounded
• Hydraulic action - The power of waves as they hit a cliff. Trapped air is forced into cracks in the rock eventually causing it to break up
• Name the five ways sediment is transported at a coast

  Traction, suspension, saltation, solution, longshore drift
• Solution (transportation) - dissolved chemicals often derived from limestone or chalk.
• Suspension - particles carried within the water
• Traction - Large pebbles rolled along the seabed
• Saltation - Bouncing motion of particles too heavy to be suspended
• What is transportation?


  Transportation - movemnt of eroded material
• What is longshore drift?

  The zizag movement of sediment along a shore caused by waves going up the beach at an oblique angle and returning at a right angle.
• What factors can influence coastal erosion?

  • Geological structure - the way a rock has been folded or tilted
  • Rock type - some rocks are more resistant to erosion than others.
• What landforms are caused by coastal erosion?

  Headlands and bays, caves, arches, and stacks, cliffs and wavecut platforms
• How are headlands formed?

  At a concordant coastline, tougher, more resistant rocks erode slower than the softer rocks. So, the harder rocks form headlands as the softer rock is eroded to form bays.