Other Factors Influencing Coasts
Geography: Edexcel IGCSE, topic 1.2.8
What Affects the Type of Coastline?
The geological formation of coastlines affects how quickly erosion happens and how at-risk an area is from erosion? The type of rock, number of joints/faults, and whether a coastline is concordant or discordant affects erosion.
Type of rock
- Headlands and bays are formed in areas that have alternate areas of hard and soft rock facing the sea.
- Rock with lots of cracks and joints is called soft rock.
- When the sea hits both the soft and hard rock, more of the soft rock is eroded.
- Amongst soft rocks, talc is the softest rock.
- Clay is a softer rock than chalk, so erodes more quickly.
- Among hard rocks, sandstone is harder than limestone.
Joints and faults
- Rocks that have lots of cracks, faults or joints are softer than rocks with fewer cracks and weaknesses.
- Soft rocks with lots of joints & faults will be eroded more quickly.
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Concordant coastlines
- Concordant coastlines have a layer of soft rock, then a layer of harder rock, then a layer of soft rock next to each other.
- This diagram shows a sand dune on top of a concordant coastline.
- The sea's waves will only hit 1 type of rock when they meet the coast.
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Discordant coastlines
- Discordant coastlines have alternating chunks of hard rock and soft rock at 90o to the coast. The sea's waves will hit both hard rock and soft rock when they meet the coast.
- Bays are usually created where the sea meets the areas of soft rock and headlands are created where the areas of hard rock are.
Test yourself on Other Factors Influencing Coasts
If waves break on both hard and soft rock, what kind of coastline is it?
Which of the following rock types is most resistant to erosion?
Which of the following rock types is most resistant to erosion?
What are the terms given to cracks and weaknesses in rocks?