distinctive landscape

Cards (111)

  • 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