distinctive landscape

• Weathering is the breakdown of rock in situ, with two types:

  • Mechanical weathering: breakdown of rock without changing its chemical composition
  • Chemical weathering: breakdown of rock by changing its chemical composition
• Example of mechanical weathering: Freeze-thaw weathering

  • Water enters rock through a crack, freezes, expands, and puts pressure on the rock
  • When water thaws, it contracts, releasing the pressure and widening cracks, causing rocks to fall and break
• Example of chemical weathering: Carbonation

  • Rainwater with carbon dioxide dissolved in it forms weak carbonic acid
  • Carbonic acid reacts with rock containing calcium carbonate, dissolving the rock
• Mass movement is the shifting of rocks and loose material down a slope, such as a cliff, when gravity's force is greater than the force supporting it
• Three types of mass movement:

  • Sliding: materials shift in a straight line along the side plane
  • Slumping: material rotates along a curved slip plane
  • Rockfall: material breaks up along bedding planes and falls down a slope
• Waves created when wind blows over the sea:

  • Destructive waves erode the coast and destroy the beach
  • Constructive waves deposit material at the coast, building the beach
• In destructive waves, the backswash (water moving down the beach) is more powerful than the swash (water moving up the beach)

  • In constructive waves, the swash is more powerful than the backwash, depositing material
• Three types of erosion:

  • Hydraulic power: waves crash against rock, compress air within cracks, putting pressure on the rock and widening cracks causing bits of rock to break off
  • Abrasion: eroded particles in the water scrape and rub against the rock, removing small pieces of the seabed
  • Attrition: eroded particles in the water collide, break into smaller pieces, and become more rounded
• Longshore drift:

  • Water moves in a specific direction following the prevailing wind direction
  • Waves hit the coast at an angle, shown by arrows of the swash
  • Swash carries material up the beach in the same direction as the waves
  • Backswash carries material down the beach at right angles back towards the sea
  • Over time, material zigzags along the coast
• Five steps to describe longshore drift:

  • Waves hit the coast at an angle
  • Swash carries material up the beach
  • Backswash carries material down the beach
  • Material zigzags along the coast
  • Diagram is helpful for understanding
• Four processes of transportation:

  • Traction: large particles like boulders pushed along the seabed by the force of water
  • Saltation: pebble-sized particles bounce along the seabed by the force of water
  • Suspension: smaller particles like silt and clay carried along in the water
  • Solution: soluble materials dissolve in the water and are carried along
  • Transported materials move in four different ways based on size, from largest to smallest
• Deposition:

  • Happens when water carrying sediment loses energy and slows down
  • Material is let go when the rate of erosion elsewhere provides material and the amount of material transported into the area affects the rate of deposition
• Rock types and geological structures influence the erosional landforms that develop on a coastline
• Discordant coastlines are made of altering bands of hard and soft rock at right angles to the coast
• Concordant coastlines have altering bands of rock that are parallel to the coast
• Headlands and bays form along discordant coastlines
• Headlands and bays form when there are altering bands of resistant and less resistant rock along a coast
• The less resistant rock erodes faster, forming a bay with a gentle slope
• The resistant rock erodes more slowly, jutting out to form a headland with steep sides
• Headlands create caves, stacks, and stumps
• The resistant rock of headlands often has weaknesses like cracks
• Waves crash into the headlands and enlarge these cracks mainly by hydraulic power and abrasion
• Repeated erosion and enlargement of the cracks cause a cave to form
• Continued erosion deepens the cave until it breaks through the headland to form an arch
• Erosion continues to wear away the rock supporting the arch until it collapses, forming a stack - an isolated rock separate from the headland
• Wave cut platforms:

  • Waves cause most erosion at the foot of a cliff, forming a wave cut notch
  • Repeated erosion causes the rock above the notch to become unstable and eventually collapse
  • Collapsed material is washed away, and a new wave cut notch starts to form
  • After repeated collapse, the cliff retreats, leaving a wave cut platform
• Beaches:

  • Found on coasts between high and low water marks
  • Formed via constructive waves depositing material
  • Two types of beaches: sandy and shingle
  • Sandy beaches created by low energy waves, flat and wide with small sand particles
  • Shingle beaches created by high energy waves, steep and narrow with large shingle particles
• Spits:

  • Form at sharp bends in the coastline
  • Longshore drift transports sand and shingle past the bend and deposits it in the sea
  • Strong winds and waves can curve the end of the spit forming a recurved end
  • Sheltered area behind the spit accumulates material and flats are able to grow over time
• Bars:

  • Form when a spit joins two headlands together, cutting off a bay from the sea to form a lagoon
  • Offshore bars can form if the coast has a gentle slope, where waves slow down and deposit sediment offshore
• Sand dunes:

  • Formed when sand deposited by longshore drift is moved up the beach by the wind
  • Obstacles cause wind speed to decrease, leading to sand deposition and formation of small embryo dunes
  • Embryo dunes are colonized by plants, stabilizing the dunes
• Hard engineering:

  • Man-made structures built to control the flow of the sea and reduce flooding and erosion
  • Examples include seawalls, gabions, rock armor, groins
• Soft engineering:

  • Schemes set up using knowledge of the sea and its processes to reduce the effects of flooding and erosion
• Sea wall:

  • Built at the edge of the coastline to protect the base of cliffs, land, and buildings against erosion
  • Aims to prevent coastal flooding
  • Expensive to build
  • Curved sea walls reflect wave energy back onto the sea, maintaining powerful waves over time
  • High cost of maintenance
• Groins:

  • Wooden barriers built at right angles towards the beach to prevent the movement of beach material along the coast (Longshore drift)
  • Allow the build-up of a beach, acting as a natural defense against erosion
  • Can be seen as unattractive and costly to build and maintain
• Rock armor and boulder barriers:

  • Large boulders piled up on the beach to absorb wave energy and allow the build-up of a beach
  • Expensive to obtain and transport
• Beach nourishment:

  • Replaces beach or cliff material removed by erosion or Longshore drift
  • Beaches act as a natural defense against erosion and coastal flooding
  • Relatively inexpensive but requires constant maintenance
• Managed retreat:

  • Areas of the coast allowed to erode and flood naturally, usually low-value areas
  • Encourages the development of beaches, natural defenses, and salt marshes
  • Low cost but requires compensation for loss of buildings and farmland
• The path of a river as it flows downhill is called its course
• Rivers have a steep upper course near the source, a gently sloping middle course, and an almost flat lower course
• The long profile of a river shows how the gradient changes