Coastal Erosion Features
There are 3 main groups of coastal features which result from coastal erosion:
1. Headlands and Bays
2. Caves, Arches, Stacks and Sumps
3. Cliffs and Wave-cut platforms
Before you revise the formation of these landforms, have a look at this video and make sure you are able to identify the landforms from their distinctive features.
1. HEADLANDS AND BAYS
Headlands are resistant outcrops of rock sticking out into the sea, whilst bays are indents in the coastline between two headlands.
So how do headlands form?
- Headlands form along discordant coastlines in which bands of soft and hard rock outcrop at right angles to the coastline.
- Due to the presence of soft and hard rock, differential erosion occurs, with the soft, less resistant rock (e.g. shale), eroding quicker than the hard, resistant rock (e.g. chalk)
- Where the erosion of the soft rock is rapid, bays are formed
- Where there is more resistant rock, erosion is slower and the hard rock is left sticking out into the sea as a headland.
- The exposed headland now becomes vulnerable to the force of destructive waves but shelters the adjacent bays from further erosion.
Named Examples of Headlands and Bays: (LEARN!)
The Dorset coast has excellent examples of Headlands and Bays
e.g. Swanage Bay and the Foreland (a headland)
2. CAVES, ARCHES, STACKS and STUMPS
Once a headland has formed it is then exposed to the full force of destructive waves and it gradually begins to erode. you need to be able to describe the erosion of a headland and the features that form.
For the sequence of formation see the animation below:
So how does a headland erode and caves, arches, stacks and stumps form?
- Firstly, the sea attacks the foot of the cliff and begins to erode areas of weakness such as joints and cracks, through processes of erosion such as hydraulic action, wave pounding, abrasion and solution;
- Gradually these cracks get larger, developing into small caves;
- Further erosion widens the cave and where the fault lines runs through the headland, two caves will eventually erode into the back of each other forming an arch, passing right through the headland.
- A combination of wave attack at the base of the arch, and weathering of the roof of the arch (by frost, wind and rain), weakens the structure until eventually the roof of the arch collapses inwards leaving a stack, a stack is a column of rock which stands separate from the rest of the headland.
- The stack will continue to erode, eventually collapsing to form a stump which will be covered by water at high tide.
The Foreland (Dorset Coastline) is a great example of a headland which shows these features - there is a distinctive stack called Old Harry and a stump known as Old Harry's Wife.
A good example of a distinctive arch, also found on the Dorset Coast is Durdle Door.
3. CLIFFS AND WAVE-CUT PLATFORMS
Cliffs are steep rock faces along the coastline, they tend form along concordant coastlines with resistant rocks parallel to the coast.
So how do cliffs and wave-cut platforms form?
- The erosion of a cliff is greatest at its base where large waves break - here hydraulic action, scouring and wave pounding actively undercut the foot of the cliff forming an indent called a wave-cut notch whilst the cliff face is also affected by abrasion as rock fragments are hurled against the cliff by the breaking waves.
- This undercutting continues and eventually the overhanging cliff collapses downwards - this process continues and the cliff gradually retreats and becomes steeper.
- As the cliff retreats, a gently-sloping rocky platform is left at the base, this is known as a wave-cut platform which is exposed at low tide.
Good examples of cliffs and wave-cut platforms can be found at Hunstanton (North Norfolk) and Flamborough Head (Yorkshire)
REVISING COASTAL EROSION FEATURES
Remember - for each erosion feature try and learn a labelled diagram to show its formation, make sure that you also mention examples of erosion processes when describing how the features are actually formed. Finally to access the highest marks remember to name and locate examples of each feature.
- Swanage Bay (Dorset Coast)
- The Foreland (Headland) (Dorset Coast)
- Old Harry (Stack) (Dorset Coast - off of the Foreland)
- Old Harry's Wife (Stump) (Dorset Coast - off of the Foreland)
- Durdle Door (South Dorset Coast)
- Cliffs and Wave-cut platforms - Hunstanton (N Norfolk) and Flamborough Head (Yorkshire)
Click here for examples of 6 mark answers on the formation of coastal erosion features
Follow up Links:
Erosion of a Headland
Animations of Cliff formation
Cliff Features and Arch Animation
Podcast: Coastal Defences
You can listen to a podcast of this post below - to download a copy to listen to on your .mp3 player click here.