Coastal Erosion - Processes And Landforms Flashcards
What are the types of cliff foot erosion?
Abrasion
Hydraulic action
Corrosion
Attrition
What is abrasion?
When waves advances, they pick up sand and pebbles from the seabed. Then, when they break at the base of the cliff, the transported material is hurled at the cliff foot.
What determines the importance of abrasion as a erosive process?
Size and amount of sediment, along with the types of wave experienced.
What is hydraulic action?
When a wave advances, air can be trapped and compressed (either in joints or between the wave and cliff).
Then, when the wave retreats, the compressed air expands again.
This continuous process can weaken joints and cracks in the cliff - causing pieces of rock to break off.
What is corrosion?
When cliffs are formed from alkaline rock (chalk/limestone), or an alkaline cement bonds the rock particles together, solution by weak acids in seawater can dissolve them.
What is attrition?
Gradual wearing down of rock particles by impact and abrasion, as the pieces of rock are moved by waves, tides and currents.
This process gradually reduces the particle size and makes stones rounder and smoother.
What can cliff-foot erosion do?
Cause cliffs to become undercut and unstable, which leads to their eventual collapse and retreat.
What are the landforms created by coastal erosion?
Headlands and bays
Cliffs
Stacks and stumps
Wave-cut platforms
What are stacks and stumps?
Isolated pillars of rock that lie just off the coast and are surrounded by water.
Stumps are completely covered at high tide.
What are wave-cut platforms?
Flat rocky platforms that extend out from the coast and surround the isolated stacks and stumps.
How are wave-cut platforms created?
Erosion against the base of the cliff creates a wave-cut notch, which begins to undercut the cliff.
As the wave-cut notch gets bigger, the rock above it becomes unstable and eventually the upper part of the cliff collapses.
As these erosional processes are repeated, the notch migrates inland and the cliff retreats - leaving a remnant behind as a wave-cut platform.
Why are wave-cut platforms useful?
They cause waves to break earlier, therefore reducing their energy before they get to the cliff, so erosion is slowed down.
What’s the sequence of a cave, arch, stack and stump?
When joints and faults are eroded by hydraulic action and abrasion, this can then create caves.
When the cave erodes through a headland, an arch is formed.
Eventually the top of the arch will become unstable and collapse - leaving a stack.
The stack itself will continue to be eroded by the sea and will collapse forming a stump.
What influences the rate and type of erosion?
The size and type of waves
Lithology
How do the size and type of waves influence erosion?
Most erosion happens during winter storms when destructive waves are at their largest and most powerful.
