4.3 Coastal Landscapes Flashcards
What is Solution. E.g. Location.
Solution is a form of transport where sediment is dissolved within the water. The sediment has to be very small and either chalk or limestone.
What is Suspension
Suspension is the transport of sediment in the water. The sediment is small enough to be suspended or held in the water, however it is not too small for it to be dissolved into the water. This can occur to any rock except chalk or limestone as they would have dissolved already.
What is Saltation
Saltation is the transport of sediment along the sea floor. The sediment size is too large for the sediment to be suspended in the water; however, it is to small enough for it to ‘hop’ along the seabed as each wave pickups the rock and then the energy is lost and therefore dropped.
What is Traction
Traction is the transport of sediment along the sea floor. The sediment is so large that the waves do not have enough energy to lift the sediment, instead it is rolled along the seabed.
What is Longshore Drift
Longshore Drift is the action of sediment being transported down the beach. The prevailing/dominant wind direction is usually at an angle to the beach and causes the swash to deposit sediment at an angle. The steepest gradient is perpendicular to the beach so the sediment is dragged directly downwards from the backwash. This process repeats and forms a ‘zig-zag’ motion of sediment. Groynes are used to present this.
What is a spit
A spit is formed when:
A longshore drift occurs along a headland. Sediment is then deposited in a long thin strip and large, heavy boulders are deposited on the edge of the apex of the headland. During the summer, the prevailing wind changes. This means that the spit curves, roughly 90°, and continues to grow and curve until there is a barrier- such as the depth of the water being to great. Behind the spit, a marsh land is formed as the energy from the waves is reduced by the spit. Grass and other plants grow and stabilise the spit and marsh land behind.
What is bar
A bar is similar to a spit. Two headlands are at similar lengths. The LSD causes the sediment to be deposited across the headlands. The spit meets the other headland and locks in the water behind it. There would be no or a little stream entering the lagoon, from the main land. The bar will have grass and other plants that help stabilise the bar.
How is a beach formed
- Sediment is eroded off the headland and deposited in the sea. This is because the headland is exposed to the wind from all directions so waves would make contact with the headland more frequently than a bay would and abrasion would also occur more often, however the headland is composed of hard rocks such as granite, limestone and chalk.
- Attrition occurs when larger pieces of sediment smash into each other and solution occurs with the chalk and limestone, which means that it doesn’t form a beach so it is only other hard rocks that can be broken down.
- The sediment is broken up enough for either saltation or suspension so it can be easily deposited on the shore.
- This is deposited on the shore through constructive waves (stronger swash than backwash) and due to the beach being inside a bay so it is more protected by the headlands and from the prevailing winds.
- The dominant or prevailing wind has caused longshore drift to carry the sediment (sand) down the coast and form a beach.
- Groynes have been placed to reduce longshore drift and keep the beach in form.
What is a concordant coastline
A concordant coastline is a coastline that is across one type of rock, typically hard rock. There are multiple layers of rock so concordant coastlines are parallel to the types of rock. Concordant coastlines form coves.
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Hard |
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Soft |
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\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_>concordant coastline
What is a discordant coastline
A discordant coastline is a coastline that is perpendicular to the types of rock. For example, there are three layers of rock that go hard, soft, hard. This coastline travels across all three rock types rather than the concordant coastline where it travels across one type of rock. Discordant coastline forms headlands and bays.
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Hard |
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Soft | ^
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Hard | | Discordant coastline
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What is a joint
A joint is a small crack that is found in the rocks, it is usually vertical
What is a fault
A fault is a large crack that is caused due to past tectonic movement where the rocks have moved.
Hard rocks and soft rocks?
Hard rocks are more resistant to erosion and therefore more likely to form a headland. These include granite, limestone and chalk (limestone and chalk are dissolved by the slightly acidic sea water).
Soft rocks are less resistant to erosion and therefore more likely to form a bay. Soft rocks include sand and clay.
How does a wave cut platform form?
Hydraulic action and abrasion occur. This erodes away part of the cliff. The wave erodes away the cliff between high tide and low tide. The cliff is now unsupported and collapses into the sea. This is then taken out by the backwash and attrition takes place. This is repeated and the wave cut platform increases in width. See Goodnotes for diagrams!
What is the process of stack formation
A fault or crack forms. This becomes a weakness in the headland. Waves erode the base of the crack and form a cave, through the process of hydraulic action and abrasion. The cave is eroded all the way through to form an arch. Chemical and biological weathering cause the roof of the arch to collapse as it is unsupported underneath. The base of the arch is weakened and soon collapses. A stack formation is formed (a single standing piece of rock).
