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Coastal Erosion
Blowholes can be a dramatic feature of a cliff structure.

Coastal Erosion

One of the topics looked at in GCSE Geography is the features that are found on a coastline. This quiz focusses in particular on those features which are caused by coastal erosion.

Over time the sea can wash away an entire coastline, forcing back human uses of that land (such as settlements or farms) and letting the sea encroach ever further inland. But it is this process which has caused so many of the features we recognise as being a part of our coastline to come about. From cliffs to headlands, caves, arches and stacks, rocky beaches and even bays that shelter ships - these are all erosional landforms.

If you are revising for your GCSE Geography exam, it is important that you know about these features as they can often crop up. It’s important to understand, not only the definitions of the process and the landforms, but also the mechanisms that caused them to form and that drive the process.

Climate change is increasing the rate of erosion on many coastlines. Rising sea levels and, more importantly, the increased frequency of high energy storm events are increasing the amount of coastal erosion. This leaves coastal communities at an even greater risk of losing the land their homes and businesses are built on.

A key thing to think about is that coastal erosion is driven for the most part by destructive waves that remove material and transport it away from that location, in the same way that rivers transport material. A destructive wave has a stronger backwash than swash. The underlying geology determines how fast the coast can be eroded and what features are left behind as it is gradually removed. Coastal erosion is often managed, but it is usually a case of moving the problem rather than truly preventing the issue of land loss.

If a cave forms on a headland the waves may erode through to form what sort of feature?
Wave cut platform
Arches allow the waves to pass through and they in turn will further erode the material and increase the size of the arch
An unusual geological feature forms when caves erode inland and, through hydraulic action, create gaps in the rock to the surface. As a wave pushes in the water is forced out of the top, often in a spout. What are these features known as?
Blowholes can be a dramatic feature of a cliff structure. Eventually the cave roof will collapse and allow the sea further in
How are stacks eroded to form stumps?
The rain and sea spray attack the stack from the top, gradually dissolving the rocks
The top-heavy nature of the stack, that may retain a lot of the material from the arch, will break off at the base far below sea level
The waves attack the base of the stack until it collapses under its own weight
Sediment washing along the coastline will build up and absorb the stack back into a larger landform
The stack is exposed on all sides and will be attacked by the waves. As the waves attack the base they can erode through it
Which of the following refers to a coastline made of bands of various types of geology, including hard and soft rock?
Discordant coastline
Concordant coastline
Uncordant coastline
Variable coastline
The layers of hard and soft rock allow bays and headlands to form as the softer rock is eroded away
When waves hit the cliff face they force air deeper into the cracks in the cliff face, which can weaken and lead to the erosion of this material. This form of erosion is known as what?
Hydraulic action
Hydraulic action takes place on rivers as well, but when you are talking about the creation of caves and other similar features this is the main erosive process
Why might a bay form?
On a discordant coastline the softer rock will be rapidly eroded away, leaving the harder rock to form headlands
On a concordant coastline weaknesses allow the water to work its way in and eventually erode a large area
A collapsed volcanic crater is flooded leaving a sheltered area
Former river valleys are flooded and form ports that gradually turn into bays
Discordant coastlines are the ones that form bays due to the different strength of the rocks. Concordant coastlines may have some small bays and headlands due to weakness in the rocks, but for the most part they are formed on discordant coastlines
When the waves attack the base of the cliff they can undercut the overlying rock, forming what sort of feature?
Raised beach
Wave cut notch
As the notch increases in size the cliff face will collapse and retreat further
As a wave undercuts a cliff the cliff retreats. What feature is left behind as the cliff retreats?
Wave cut platform
As the wave cut notch undercuts the cliffs the platforms form. These are flat features that are noticeable if they are raised, due to sea levels falling, into a raised beach
Which type of underlying geology is most likely to be formed into straight cliffs?
Soft rocks like mudstone and siltstone
Hard rocks including granite and basalt
Loose materials like soils and sands
Rocks that are partially soluble
The more resistant rocks will form straighter cliffs. Softer rocks will have a shallower cliff structure as material erodes and collapses faster
'Old Harry Rocks' in Dorset are examples of an erosional feature left behind after an arch collapses. These tall columns of rocks are known as what?
Stacks are commonly tall columns of rock, although some of them may be very large and on their way to being eroded to stumps
You can find more about this topic by visiting BBC Bitesize - Coastal environments

Author:  Ruth M

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