3.1.3.3 Landforms Of Erosion Flashcards
Outline the difference between a ‘landform’ and a ‘landscape’.
Landforms are individual components of a landscape (e.g., cliffs and beaches) whereas landscapes are a section of the coast made up of a number of landforms.
- The formation of landforms can be studied using a systems approach. List the key inputs, processes and outputs involved:
Inputs=geology,climate,natureofwaves
Processes=marineerosion,weathering,transportation,deposition,mass
movement, wave refraction, climate change (including sea level rise)
Outputs = sediment, landforms
Explain the development of headlands and bays along a discordant coastline.
• A headlands and bay landscape can develop on a discordant coastline with alternate
bands of hard and soft rock.
• Over time marine erosion processes, including wave pounding and corrasion erode the
less resistant, softer bands of rock more quickly creating bays, leaving the harder
bands of rock as headlands jutting out to sea.
• Wave refraction causes erosional energy to be concentrated on the headlands, which
will, in time, erode forming caves, and possibly arches and stacks. Constructive waves in the sheltered bays result in deposition and an accumulation of sediment to form beaches. These protect the coastline behind form further erosion.
Effects of Sub-aerial processes (weathering and mass-movement)
Weathering processes such as freeze-thaw and carbonation help to weaken the exposed rock of the cliff face and over the overhand above the wave-cut notch, making it vulnerable to mass movement processes such as rock falls and landslips, causing cliff collapse and retreat.
Effect of Marineprocesses(erosion,transport,anddeposition):
Wave energy is focused at the cliff base during high tide, with erosion depending on wave energy and rock type. Sedimentary rocks like limestone are vulnerable to hydraulic action, solution, and corrasion. Cliff collapse initially provides temporary protection (negative feedback), but waves eventually transport the debris away.
Wave-cut platforms rarely grow wider than 500m, explain why.
As waves travel over the wave-cut platform their energy is dissipated (reduced) due to friction with the rock beneath. There will reach a point whereby the waves will have lost all energy before their reach the cliffs behind. This is the point at which there will be no further cliff retreat (equilibrium is reached).
Which factors determine the height, shape, and steepness of a cliff?
Erosion and weathering depend on geology, wave energy, and climate. Harder rocks form steep, high cliffs, especially after undercutting and collapse. Softer rocks, like clay, create lower, gentler cliffs due to slumping and mudflows.
Caves, arches, and stacks tend to form on headlands, explain why.
The process of wave refraction (waves ‘bending’ to follow the shape of a coastline) along a discordant coastline means that wave energy is focused on either side of the protruding (jutting out) headland.
What type of rock is often associated with the formation of caves, arches, and stacks and why?
High energy waves at high tide can lead to erosion along lines of weakness in sedimentary rock like limestone such as joints and cracks.
What role do erosion processes play in the formation of caves, arches, and stacks?
Hydraulic action widens cracks in sedimentary rocks like limestone, forming caves. Wave pounding and corrasion enlarge caves, sometimes creating blowholes if the roof collapses. When caves form on opposite sides of a headland, they may break through to form an arch. Continued erosion weakens the arch until it collapses, leaving a stack (e.g., Old Harry, Dorset). Further erosion reduces the stack to a stump, visible only at low tide.
What role do sub-aerial processes play in the formation of caves, arches, and stacks?
Sub-aerial processes, such as weathering play a key role in weakening the roof of an arch which then collapses (mass movement) to form a stack. Weathering of the rock above a cave may weakening it making collapse, forming a blow hole, more likely. Stumps form when the rock above sea level is weakened due to weathering.
Example of Cliff retreat and a wave-cut platform
Robin Hood’s Bay, North Yorkshire
Examples of Caves, arches, and stacks in a headland
The Foreland/Old Harry, Dorset
