Coasts - Erosional Landforms


Headland and Bays

1. Hard rock and soft rock are in layers within a cliff.

2. The hard rock e.g. chalk is more resistant of erosion, whereas the soft rock e.g. clay is less resistant of erosion, this therefore means that the soft rock is eroded more rapidly, eventually forming a bay. This leaves the hard rock sticking out as it is not eroded as rapidly, forming a headland. 

3. Once both formed the bays are sheltered by the headlands meaning they are eroded less and the headlands are subject to greater amounts and rates of rapid erosion, which eventually will make the cliff face even again and the process will start all over again.

Due to wave refraction the shallower waves will cause more deposition in the bay, meaning there is a possibility of a beach forming. 

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What is a GEO = where erosion excavates enough material along a vertical line of weakness, forming a narrow, steep sided inlet called a GEO. 


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Blow hole

1. Erosion can exploit lines of weakness in the rock/cliff face, eroding enough material to form a cave.

2. If the erosion continues VERTICALLY, overlying rocks can collapse forming a blow hole. 


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Wave cut notches and platforms

1. A wave cut notch is formed due to erosion, such as abrasion, hydraulic action and solution, undercutting the cliff. 

2. Rapid rates of continuous erosion increases the size of the wave cut notch - this means that the overlying rocks above the wave cut notch become unstable. Also weathering, such as chemical (acid rain) and biological (animals burrowing) weakens the top of the cliff. Over time the cliff becomes weakened, it then collapses and retreats, leaving material at the foot of the cliff which then gets deposited and eroded to form a wave cut platform.

3. The cliff has collapsed and retreated, which has left material (sediment) at the foot of the cliff, which forms a wave cut platform at the original high tide mark on the cliff. Erosion then occurs and begins to form another wave cut notch, weakening the current cliff - the whole process happens over and over again, it is continuous. 


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Caves, arches, stacks and stumps

Caves = they occur when waves force their way into cracks in the cliff face. Hydraulic action increases the size of the cracks, making them increasingly bigger until a cave is formed. 

Arches = If the cave is formed in a headland hydraulic action and abrasion will keep on eroding until it breaks through to the other side forming an arch. 

Stacks = The arch will gradually become bigger, due to erosion, until it can no longer support the top of the arch, it will then collapse, leaving the headland and forming a tall column of rock - a stack.

Stumps = The stack will be attacked at its base, in the same way as a wave cut notch (undercutting). This weakens the stacks structure, it then collapses, leaving behind a small stump of rock (its base). 

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