Coastal Erosion
One of the most common features of a coastline is a cliff. Cliffs are shaped through a combination of erosion and weathering - the breakdown of rocks caused by weather conditions.
Soft rock, eg sand and clay, erodes easily to create gently sloping cliffs. Hard rock, eg chalk, is more resistant and erodes slowly to create steep cliffs.
The process of cliff erosion
Soft rock, eg sand and clay, erodes easily to create gently sloping cliffs. Hard rock, eg chalk, is more resistant and erodes slowly to create steep cliffs.
The process of cliff erosion
- Weather weakens the top of the cliff.
- The sea attacks the base of the cliff forming a wave-cut notch.
- The notch increases in size causing the cliff to collapse.
- The backwash carries the rubble towards the sea forming a wave-cut platform.
- The process repeats and the cliff continues to retreat.
Weathering and erosion can create caves, arches, stacks and stumps along a headland.
Caves occur when waves force their way into cracks in the cliff face. The water contains sand and other materials that grind away at the rock until the cracks become a cave. Hydraulic action is the predominant process.
- If the cave is formed in a headland, it may eventually break through to the other side forming an arch.
- The arch will gradually become bigger until it can no longer support the top of the arch. When the arch collapses, it leaves the headland on one side and a stack (a tall column of rock) on the other.
- The stack will be attacked at the base in the same way that a wave-cut notch is formed. This weakens the structure and it will eventually collapse to form a stump.
Wave Cut Platforms
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.
- 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.
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.
HEADLANDS AND BAYS
Headlands are resistant outcrops of rock sticking out into the sea, while bays are indents in the coastline between two headlands.
So how do headlands form?
- Headlands form along 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, different speeds of erosion occurs, with the soft, less resistant rock (e.g. shale, chalk), eroding quicker than the hard, resistant rock (e.g. limestone)
- 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.
So how do headlands form?
- Headlands form along 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, different speeds of erosion occurs, with the soft, less resistant rock (e.g. shale, chalk), eroding quicker than the hard, resistant rock (e.g. limestone)
- 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.
One more time....
So how does a headland erode and caves, arches, stacks and stumps form?
- First, 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.
- First, 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.
Interactive Revision Quizzes:
You must learn your notes but once you have revised from your notes there are some interactive revision quizzes here for you to test yourself.
Coast Key Word Flash Cards (definitions then key words) Coasts Key Word Flash Cards (key words then definitions) Coasts Key Word Test Coastal Features Recognition and Examples Test Coastal Management Quiz Coasts Revision Quiz 1 Coasts Revision Quiz 2 - Penalty Shootout Coasts Revision (Walk the Plank) Coasts Questions - Practice Paper Coasts Downloadable Flashcards Coasts Revision Dominoes Coastal Features Countdown Conundrum Crazy Coasts (Half a min - anagrams) Coasts Dustbin Game - sorting erosion and deposition features Coasts Dustbin Game - Erosion and Deposition Features Case Studies Coasts Podcasts Podcast 1 - Energy at the Coast - waves and wave formation Podcast 2 - Coastal Processes Podcast 3 - Coastal Erosion Features Podcast 4 - Coastal Deposition Features Podcast 5 - A case study of coastal erosion - Dunwich Podcast 6 - Coastal Defence Click HERE to go to a great revision site......and HERE for yet, another good site!Be sure to scroll to the bottom and try the three different forms of revision quizzes.
|
Checklist of key concepts to revise:
1. Energy at the coast - types of waves and basic principles behind wave formation. What factors affect the strength of waves? 2. Coastal Processes - erosion processes (you must be able to describe the processes and how they work); transport processes (you must be able to explain the process of longshore drift and it helps if you are able to draw an good labeled diagram to show the process) and deposition 3. Coastal Erosion Landforms - you must be able to describe both the features and formation of the following landforms: cliffs; wave-cut platforms; headlands and bays; caves, arches, stacks and stumps (in your description and explanation of formation always include some examples of named erosion processes that may be at work). You should also be able to draw annotated diagrams of the features to show how they form. 4. Coastal Deposition Landforms - you must be able to talk through both the features and formation of beaches and spits. You should be able to draw diagrams of the features to show how they form. 5. Case Study of Coastal Erosion - learn (including detail - i.e. location, facts and figures) a case study of coastal erosion - either Dunwich or the Holderness Coast. 6. Coastal Defense - you need to be aware of the options for coastal defense - hard engineering, soft engineering or managed retreat. You should be able to describe coastal management techniques and be able to discuss their advantages and disadvantages. Revision Resources: - make good use of your class notes - make use of posts on Weebly and your textbook |