Coastal landscapes and processes Flashcards
1
Q
What are the three types of weathering?
A
- Mechanical weathering
- Biological weathering
- Chemical weathering
2
Q
What is mechanical weathering?
A
- Mechanical weathering is the breakdown of rock without changing its chemical composition.
3
Q
Example of mechanical weathering?
A
- Salt weathering on the coasts.
- Seawater gets into cracks in the rock.
- When the water evaporates, salt crystals form. As the salt crystals form they expand, which puts pressure on the rock.
- Repeated evaporation of saltwater and the forming of salt crystals widens the cracks an causes the rock to break up.
4
Q
What is chemical weathering?
A
- Chemical weathering is the breakdown of rock by changing its chemical composition.
5
Q
Example of chemical weathering?
A
- Carbonation is a type of chemical weathering that happens in warm and wet conditions.
- Rainwater has carbon dioxide dissolved in it, which makes it a weak carbonic acid.
- Carbonic acid reacts with rock that contains calcium carbonate, e.g. chalk, so the rocks are dissolved by the rainwater.
6
Q
What is biological weathering?
A
- The breakdown of rock by living things.
7
Q
Example of biological weathering?
A
- Animals, such as rabbits, burrow into soil on cliff tops.
- Plant roots break down rocks by growing into cracks on their surfaces.
8
Q
What is mass movement?
A
- Mass movement is the downward movement of material under the influence of gravity.
9
Q
What are the four processes of erosion?
A
- Hydraulic action
- Abrasion
- Atrittion
- Solution
10
Q
What is hydraulic action?
A
- Hydraulic action is when waves crash against rock and compress the air in the cracks, putting pressure on the rock.
- Repeated compression widens the cracks and makes bit of rock break off.
11
Q
What is abrasion?
A
- Abrasion is when eroded particles in the water scrape and rub against rock, removing small pieces.
12
Q
What is attrition?
A
- Attrition is when eroded particles in the water smash into each other and break into smaller fragments.
- Their edges also get rounded off as they rub together.
13
Q
What is solution?
A
- Solution is basically just chemical weathering.
14
Q
What are destructive waves?
A
- Destructive waves are the waves that carry out erosional processes.
- They have a high frequency.
- They are steep and high.
- Their backwash is more powerful than their swash.
15
Q
What are constructive waves?
A
- Constructive waves deposit more material than they erode.
- They have a low frequency.
- They are low and long.
- The swash is powerful and carries material up the coast.
- The backwash is weaker and doesn’t take a lot of material back down the coast.
- This means material is deposited on the coast, building up beaches.
16
Q
What is transportation?
A
- Transportation is the movement of material.
17
Q
How does longshore drift work?
A
- Waves follow the direction of the prevailing wind.
- They usually hit the cost at an oblique angle.
- The swash carries material up the beach, in the same direction as the waves.
- The backwash carries material down the beach at right angles, back toward the sea.
- Over time, material zig-zags along the coast.
18
Q
What are the four processes of transportation?
A
- Traction
- Saltation
- Suspension
- Solution
19
Q
What is traction?
A
- Traction is large particles like boulders being rolled along the sea bed by the force of the water.
20
Q
What is saltation?
A
- Saltation is pebble-sized particles being bounced along the seabed by the force of the water.
21
Q
What is suspension?
A
- Suspension is small particles like silt and clay being carried along in the water.
22
Q
What is solution?
A
- Solution is soluble materials being dissolved in the water and carried along.
23
Q
What is deposition?
A
- Deposition is when material being carried by the seawater is dropped on the coast.
- It occurs when water carrying sediment slows down so that it doesn’t have enough energy to carry on carrying the sediment.
24
Q
What is a concordant coastline?
A
- In concordant coastlines, the alternating bands of hard and soft rock are parallel to the coast.
25
Q
What is a discordant coastline?
A
- In discordant coastlines, the alternating bands of hard and soft rock are at right angles to the coast.
26
Q
What erosional landforms are more common on discordant coastlines?
A
- Headlands and bays
27
Q
How is a wave-cut platform formed?
A
- Waves cause most erosion at the foot of a cliff.
- This forms a wave-cut notch, which is enlarged as erosion continues.
- The rock above the notch becomes unstable and eventually collapses.
- The collapsed material is washed away and a new wave-cut notch starts to form.
- Repeated collapsing results in the cliff retreating.
- A wave-cut platform is the platform that’s left behind as the cliff retreats.
28
Q
How is a spit formed?
A
- Spits form when the coastline suddenly changes direction.
- Longshore drift will continue to deposit sand and shingle past the bend and deposit it into the sea.
- Over time the layer of sediment deposited will be above sea level where it is visible as a spit.
- Strong winds and waves can curve the end of a spit forming a recurved end.
- The sheltered area behind the spit is a low energy environment - it is protected from waves. Lots of material accumulates in this area, which means plants can grow here.
- Over time, the sheltered area can become can become a mud flat or salt marsh.
29
Q
How is a bar formed?
A
- A bar is formed when a spit joins two headlands together.
- The bar cuts off the bay between the headlands from the sea.
- This means a lagoon is formed behind the bar.
30
Q
How does industry affect coastal landscapes?
A
- Coastal quarries expose large areas of rock, making them more vulnerable to chemical weathering and erosion.
- Gravel has been extracted from some beaches for use in the construction industry. This has increased the risk of erosion because there’s less material to protect cliffs.
- Industrial growth at ports has led to increased pressure to build on salt marshes. These areas provide flat land and sheltered water, which are ideal for ports and industry, but are also natural flood barriers. Building on them leaves the land more vulnerable for erosion.
31
Q
How does agriculture affect coastal landscapes?
A
- Clearing vegetation to make room for crops near the coast can expose the soil and underlying rock on clifftops, leaving them vulnerable to weathering.
- Marshland is sometimes reclaimed and drained for agricultural use. This reduces the natural flood barrier that marshland provides.
- Agriculture land has a low economic value which means it’s often left unprotected and vulnerable to erosion.
32
Q
How does urbanisation affect coastal landscapes?
A
- Coastal areas are popular places to live and work, so they often have lots of development and infrastructure.
- Coasts with lots of settlement may have more coastal defences than other areas because people want to protect their homes and businesses. This means the land is better protected against erosion.
- However, building on coastal lowlands can restirct sediment supply to beaches, making them narrower. Narrow beaches don’t protect the coast as well, which means the land is more vulnerable to erosion.
33
Q
How does coastal retreat affect people?
A
- Homes and businesses in low-lying coastal areas are vulnerable to flooding. Coastal recession means that the sea is closer to settlements, so they are less protected by beaches and cliffs during storms and high tides, increasing the risk of flooding.
- Coastal industries may be shut down because of flood damage to equipment and buildings.
- There’s a risk of damage to infrastructure like roads and rail networks from flooding and coastal recession.
- There is a booming tourist industry in coastal areas. Flooding and erosion can put people off visiting. Businesses that rely on tourism may close, leading to a loss of livelihood.
- In places with rapid coatal recession, e.g Happisburgh in Norfolk, houses, businesses and farmland can be lost to the sea as cliffs collapse.
