Geography paper 1

• Constructive waves

  • Strong swash, weak backwash
  • Low wave height, large wavelength
  • Low frequency
  • Depositional - the waves leave material on the beach, and so build up the material (sand, pebbles, etc) over time

  
• Destructive waves

  • Strong backwash, weak swash
  • High wave height, small wavelength
  • High frequency
  • Erosional - the waves erode the beach and any rocks and take the material away to other locations. Over time, the beach wears away

  
• Factors affecting wave size

  • Strength of the wind
  • How long the wind has been blowing for
  • Water depth
  • Fetch - the distance the waves have travelled from where they originated from

  
• Coastlines hit by constructive waves


  Tend to have depositional landforms such as sandy beaches

  
• Coastlines hit by destructive waves

  Typically have erosional landforms such as rocky headlands and landforms, such as tall cliffs and caves

  
• Coastal processes


  • Erosion
  • Weathering
  • Transportation
  • Mass movement
  • Deposition

  
• Corrasion

  Sand and pebbles are picked up by the sea and hurled against the cliffs at high tide, causing the cliffs to be eroded. The shape, weight and quantity of sediment picked up, as well as the wave speed, affects the rate of erosion

  
• Abrasion


  Sediment scrapes and bangs against the base of a rockface, and so wear away the face gradually (like sandpaper against a piece of wood)
• Attrition


  Wave action causes rocks and pebbles to hit against each other, wearing each other down and so becoming round and eventually smaller

  
• Hydraulic action


  As a wave crashes onto a rock or cliff face, air is forced into cracks within the rock. The high pressure causes the cracks to force apart and widen when the wave retreats and the air expands. Over time this causes the rock to fracture
• Corrosion (Solution)


  The mildly acidic seawater can cause alkaline rock such as limestone to be eroded
• Erosional landforms


  • Caves
  • Arches
  • Stacks
  • Stumps
• Erosional landforms


  • Wave-cut notch
  • Wave-cut platform

  
• Longshore drift


  Sediment is transported along the coast through the process of longshore drift

  
• Longshore drift

  1. Waves hit the beach at an angle determined by the direction of the prevailing wind

  2. The waves push sediment in the direction of the prevailing wind up the beach in the swash

  3. Due to gravity, the wave then carries sediment back down the beach in the backwash

  4. This moves sediment along the beach over time

  
• Deposition


  Occurs when a wave loses energy meaning the sediment becomes too heavy to carry
• Depositional landforms


  • Beaches
  • Spits
  • Bars
  • Sand dunes
• Berm


  Ridges where high tide reaches and deposits a ridge of sand and materials (seaweed, driftwood, etc)

  
• Spit

  A long narrow strip of land which is formed due to deposition. Longshore drift occurs along the coastline but as the waves lose energy (normally due to going into a sheltered area such as behind a headland) they deposit their sediment. Over time this creates a spit

  
• Bar

  Bars can form from spits, but only in certain locations. A bar is a spit that has grown across the mouth of a bay. This cuts off the sea water from the bay, creating a lagoon with still water and over time this will become a freshwater lake
• Sand dunes


  Occur when prevailing winds blow sediment to the back of the beach. There are different types of sand dunes, the name they're given depends on their stage of development and position on the beach

  
• Embryo dunes are found in the upper beach area where sand starts to accumulate around a small obstacle (driftwood, wooden peg, ridge of shingle)
• Yellow dunes are formed as more sand accumulates and the dunes become more vegetated
• Bar


  • Forms from spits, but only in certain locations
  • A spit that has grown across the mouth of a bay, cutting off the sea water and creating a lagoon which over time becomes a freshwater lake
  • Can also form between land and an island, known as a barrier beach
• Sand Dunes

  • Occur when prevailing winds blow sediment to the back of the beach
  • Different types of sand dunes depending on their stage of development and position on the beach
• Weathering


  The breakdown of rocks over time, producing material which creates coastal landforms or sediment taken away through transportation

  
• Types of weathering processes


  • Mechanical (Physical) Weathering
  • Chemical Weathering
  • Biological Weathering
• Mechanical (Physical) Weathering


  The breakdown of rocks due to exertion of physical forces without any chemical changes taking place
• Freeze-thaw

  Water enters cracks in rocks, then freezes overnight, expanding by 10% in volume which increases the pressure acting on the rock, causing cracks to develop over time
• Chemical Weathering

  The breakdown of rocks through chemical reactions, the most common type being carbonation where acid rain reacts with calcium carbonate in rocks
• Biological Weathering


  The breakdown of rocks due to the actions of plants, bacteria and animals
• Types of mass movement

  • Rock falls
  • Landslides
  • Mudflow
  • Rotational Slip
• Rock Fall


  Occur on sloped cliffs (over 40 degrees to the beach floor) when the rock becomes exposed to mechanical weathering (often freeze thaw)
• Landslide

  Water between sheets of rock (called bedding planes) and the rock face reduces friction and allows large chunks of rock to slide down the cliff
• Mudflow

  Saturated (waterlogged) soil flows down the face of a hill like a fluid, bulging at the bottom in a lobe
• Rotational Slip


  Also known as slumps, soil and rock fragments become saturated with water and slip, creating stepped 'heads' down the cliff face
• Coastal management strategies


  • Hard engineering
  • Soft engineering
  • Managed retreat
• Hard engineering


  Uses man-made, artificial structures to reduce or halt erosion, often very effective but high cost and significant environmental impact
• Soft engineering


  Uses more natural materials to reduce erosion, in a more environmentally friendly way, aiming to complement the physical environment
• Managed retreat


  Allows erosion rates to carry on unchanged, monitoring the rate of erosion and putting ways of adapting to this erosion in place for the future