Coasts Flashcards
1
Q
The UK Physical Landscape
A
- Upland areas mainly in the North and West. These areas are forced of hard, igneous and metamorphic rocks that are resistant to erosion.
- The lowland areas are in the South and the East, formed of softer, sedimentary rocks that erode easier.
- Most cities are in lowland areas and on the UK main rivers.
2
Q
Mechanical Weathering
A
Breakdown of rock without changing its chemical composition
3
Q
Freeze-thaw weathering (mechanical weathering)
A
- When the temp alternates above and below 0.
- Water enters a rock with cracks
- When water freezes, it expands, which puts pressure on the rock.
- When water thaws it contracts, which releases pressure on the rock.
- Repeated process widens the cracks and causes the rock to break up
4
Q
Chemical weathering
A
The breakdown of rock by changing its chemical composition
5
Q
Carbonation (chemical)
A
- Rainwater has co2 dissolved in it, which makes it a weak carbonic acid.
- Carbonic acid reacts with rock that contains calcium carbonate e.g Carboniferous limestone, so rocks are dissolved by the rainwater.
6
Q
Mass Movement - definition
A
The shifting of rocks and loose material down a slope.
7
Q
Mass Movement - process
A
- The shifting of rocks and loose material down a slope.
- It causes coasts to retreat rapidly.
- It’s more likely to happen when the material is full of water - water acts as a lubricant, and makes the material heavier.
- When material shifts, it can create a scarp (a deep cut) in the side of the slope.
8
Q
Sliding
A
Material shifts in a straight line along a side plate
9
Q
Slumps
A
Material rotates along a curved slip plane
10
Q
Rockfalls
A
Material breaks up, often along bedding planes, and falls down a slope.
11
Q
The greater the fetch…
A
The greater the power of the wave
12
Q
Destructive waves
A
- High frequency, high and steep
- Strong backwash, weak swash > material is removed from beaches
13
Q
Constructive waves
A
- Low frequency, low and long.
- Powerful swash, weak backwash > material is deposited
14
Q
Hydraulic action
A
Waves crash against the rock and compress the air in the rocks > puts pressure on the rock > bits fall off
15
Q
Abrasion
A
Eroded particles in the water scrape and rub against rock, removing small pieces
16
Q
Attrition
A
Eroded particles and the water collide, break into smaller pieces and become more rounded
17
Q
Longshore drift
A
- Waves follow the direction of the prevailing wind.
- They hit the coast at an angle.
- The swash carries material up the beach, in the same direction as the waves.
- The backwash then carries material down the beach at right angles, back towards the sea.
- Over time, material zigzags along the coast
18
Q
Traction
A
Large particles like boulders are pushed along the sea bed by the force of the water
19
Q
Suspension
A
Small particles like silt and clay are carried along in the water
20
Q
Saltation
A
Pebble-sized particles are bounced along the sea bed by the force of the water
21
Q
Solution
A
Soluble materials dissolve in the water and are carried along
22
Q
Deposition - where does it occur?
A
- When water carrying sediment loses energy and slows down.
- Coasts build up when the amount of deposition is greater than the amount of erosion.
- The amount of material that’s deposited on an area of coast is increased when there’s lots of erosion elsewhere on the coast or lots of material is transported into the area.
- Constructive waves deposit more than erode
23
Q
How are wave cut platforms formed?
A
- Waves cause most erosion in the area between low tide and high tide (zone of erosion). In this zone, a wave cut notch forms.
- This enlarges over time and repeated erosion causes the rock above to become unstable and eventually collapse.
- The collapsed material is washed away and a new wave-cut notch starts to form.
- After repeated collapses, the cliff retreats, leaving a wave-cut platform
24
Q
Beaches
A
Are found on coasts between high and low water marks. They’re formed by constructive waves depositing material.
25
Sand beaches are formed -
Low energy waves, flat and wide
26
Shingle beaches are made
By high energy waves, steep and narrow
27
How are spits formed?
1. Form at sharp bends in the coastline.
2. LSD transports sand and shingle past the bend and deposits it in the sea.
3. Strong winds and waves can curve the end of the spit forming a recurved end.
4. The area behind the spit is sheltered from waves, so material accumulates and plants can grow.
5. Over time, the sheltered area becomes a mud flat or salt marsh.
28
How are bars formed?
1. When a spit joins two headlands together.
2. The bay between the headlands gets cut off from sea.
3. This means a lagoon can form behind the bar.
4. Offshore bars can form if the coast has a gentle slope - friction with the sea bed causes waves to slow down and deposit sediment offshore, creating a bar that isn’t connected to the coast.
29
How are sand dunes formed?
1. When sand is deposited by LSD and moved up the beach by the wind.
2. Obstacles (drift sand) decrease wind speed to sand is deposited, forming small embryo dunes.
3. These are colonised by plants (marram grass). The roots of the vegetation stabilise the sand, encouraging more sand to accumulate there. This forms foredunes, and eventually mature dunes. New embryo dunes form in front of stabilised dunes.
4. Dune slacks can forms in hollows between dunes.
30
Discordant coastline
Made up of alternating bands of hr and sr at right angles to the coast
31
Concordant coastline
Alternating bands of hr and sr parallel to the coast.
32
How do headlands and bays form?
1. Where there are alternating bands of hr and sr along a coast.
2. Sr eroded faster, forming a bay with a gentle slope.
3. HR erodes slower so it sticks out and forms a headland with steep sides
33
Crack, Cave, Arch, Stack, Stump
1. Resistant rock can have cracks.
2. Waves crash into the headlands and enlarge the cracks (HA and abrasion).
3. Repeated erosion and enlargement of cracks causes a cave to form.
4. Erosion deepens through the cable until it breaks through the headland to form an arch (durdle door).
5. Erosion wears away the rock supporting the arch, until it collapses.
6. Forms a stack - an isolated rock that’s separate from the headland (Old Harry)
34
Case Study places
Durdle door (arch), lulworth cove (bay), Chesil beach (tombolo - a type of bar), swanage bay
35
Sea Walls
A wall made out of a hard concrete that reflects waves back to sea. It prevents erosion and acts as a barrier to prevent flooding. However, it creates a strong backwash that erodes under the wall. Expensive to build + maintain
36
Gabions
A wall of wire cages filled with rocks, usually built at the foot of the cliffs. Gabions absorb wave energy and so reduce erosion. They’re cheap and easy to build. They’re ugly and wire cages can corrode.
37
Rock Armour
Boulders that are piled up along the coast. It absorbs wave energy, reducing Erosion and flooding. Cheap. Boulders can be moved so they need to be replaced.
38
Groynes
Wooden or stone fences that are built at right angles to the coast. They trap material transported by LSD. Create wider beaches which slow the waves. Gives greater protection from flooding and erosion. Cheap. However, they starve beaches further down the coast of sand, making the narrower. Narrow beaches don’t protect the coast as well, leading to greater erosion.
39
Beach Nourishment/Replenishing
Sand and shingle from elsewhere or from lower down the beach that’s added to the upper part of beaches. It creates wider beaches which slow the waves. Gives greater protection from flooding and erosion. Can kill organisms taking material from the seabed. Expensive and has to be repeated
40
Dune Regeneration
Creating or restoring sand dunes by nourishment, or by planting vegetation to stabilise the sand. Create a barrier between land and sea, absorb wave energy, preventing flooding and erosion. Stabilisation is cheap. The protection is limited to a small area. Nourishment is very expensive.
41
Managed retreat
Removing defences and allowing sea to flood the land. The land will become marshland, which then protects the land behind it from erosion and flooding. Cheap and easy, doesn’t need maintaining. Marshland can create new habitats for plants and animals. Can cause conflicts e.g flooding farmland affects livelihood of farmers and saltwater an have a negative effect on ecosystems.
