4c - Coasts

Question 1

Describe constructive waves

Answer 1

Have a stronger swash than backwash resulting in deposition
Low wave amplitudes, long wavelengths, low frequency
Associated with light winds, short fetches
Result in flat, wide beaches

Question 2

Describe destructive waves

Answer 2

Has a stronger backwash than swash resulting in erosion
High amplitudes, short wavelengths, high frequency
Associated with strong winds, long fetches
Results in narrow, steep beaches

Question 3

Describe the three types of weathering

Answer 3

Chemical - chemical reaction between liquids/rain
Physical - exploits cracks/joints in rocks
Biological - microorganisms eat away at inside of rock/ seeds or roots grow in cracks, joints

Question 4

What do cliffs have?

Answer 4

Horizontal bedding planes (strong) & vertical joints and faults (weak)

Question 5

Describe concordant coastlines

Answer 5

Coastlines that have bands of different rock types arranged in parallel to the coastline
Forms landscapes such as notches, cliffs & wave cut platforms, coves can form if sea can get at soft rock behind hard rock
Have same rate of erosions and retreating

Question 6

Describe discordant coastlines and state what landforms are created

Answer 6

Coastlines that have bands of alternating rock types that run perpendicular to the coastline
Forms landscapes such as bays, headlands -> cracks, caves, arches, stacks, stumps
Different rates of erosion

Question 7

Explain how concordant coastline landforms are formed?

Answer 7

The sea attacks the base of a hard rock cliff forming wave cut notches
The notch increases in size causing the cliff to collapse
The backwash carries rubble towards the sea forming a wave-cut platform
Process repeats and cliff continues to retreat

Question 8

Explain how discordant coastline landforms are formed?

Answer 8

Bays are formed due to rapid erosion of less resistant rock
Headlands are formed due to less erosion of more resistant rock
Once formed headlands are vulnerable to erosion as wave energy is concentrated there

In headlands, caves are formed when waves erode a weakness eg fault, joint
Arches are formed when two caves erode from either side of a headland and meet
A stack is formed when an arch collapses
A stump is formed when a stack is eroded by wind & water

Question 9

How does longshore drift occur?

Answer 9

Waves approach beach in the direction of prevailing wind
Swash moves up beach transporting sediment in wave direction
Backwash travels perpendicular to sea (due to gravity), carrying sediment with it
The next wave strikes carrying sediment up beach, causing sediment to move along coastline
If movement is stopped a beach develops

Question 10

Explain the two landforms formed by longshore drift

Answer 10

Depositional landforms: bars, spits
Bars: (often found in small bays)
- sand pushed by LSD forms a bank of sediment that joins the headland
- former bay cut off from sea to form a lagoon

Spits: (often found at river estuaries where coast abruptly changes direction)
- LSD transports sediment into river mouth
which is deposited as a spit
- alluvium builds up behind sandbank causing salt marsh

A tombolo forms when a spit joins an offshore island

Question 11

Describe the 4 processes of erosion and what else speeds up coastal erosion

Answer 11

Abrasion - surface friction smooths rocks
Attrition - rocks collide with each other making smaller rocks
Corrosion - chemical reactions between water and rocks
Hydraulic action - pressure created as air and water squeezed into rock cracks
Destructive waves/ soft, jointed geology

Question 12

Describe the 4 processes of transformation

Answer 12

Traction - large boulders roll along bed which requires energy
Saltation - smaller stones bounce along sea bed
Solution - rock minerals dissolved in sea water and carried
Suspension - small rock is suspended and carried

Question 13

What is mass movement and describe how it occurs?

Answer 13

Mass movement - downhill movement of material under influence of gravity
Slumps - when rock saturated with water and slides down a curved slip plane with a rotation
Sliding - when loosened rock and soil suddenly tumble down a slope in a straight line
Rockfalls - material breaks up and falls down the slope

Question 14

State some pros and cons of hard engineering

Answer 14

+ prevents erosion
+ long lasting
+ can provide opportunities (groynes build beaches)
- expensive
- requires regular maintenance
- ugly, harming tourism
- building closes the beach, less tourism
- interferes with natural processes eg LSD

Question 15

State some pros and cons of soft engineering

Answer 15

+ doesn’t affect natural processes eg LSD
+ cheap
+ natural habitats remain for animals, plants
- can be ineffective in preventing erosion
- people can lose their homes and land value may decrease
- beach nourishment needs regular resupply as its eroded over time

Question 16

State human factors which affect coatlines

Answer 16

Development - weight of building -> mass movement, high value land requires protection
Industry - requires hard engineering to protect, construction industry requires gravel from beaches -> increased erosion
Agriculture - clearing land for farming reduces stabilisation of soil so more prone erosion, low value land often left unprotected
Coastal management - groynes, sea walls etc, can increase erosion further down coastline

Question 17

Describe Lyme Regis

Answer 17

Rain exceeds 8500m annually - adds stress on cliffs
Sea level predicted to rise 55cm by 2100
Town built on unstable, soft clays with poor drainage - perfect for landslides
Population of 5000 living mostly within 1km of coastline
Development led to removal of natural vegetation with impermeable surfaces -> surface runoff increased
Tourist dependant econ with 15000 tourists during summer

Question 18

Describe the coastal management of Lyme Regis

Answer 18

Beach nourishment - sand replenished
Groynes keep the beach, tourism
Rock armour placed in front of sea wall to absorb wave energy and retain beach
Harbour wall (The Cobb)
Quite costly temporarily - proposed cost of £30 mil - resulting in closure of huts, car park access
Protected 5000 residents, tourism, parks re-landscapes

Question 19

How does climate change affect coastlines?

Answer 19

Climate change results in melting glaciers (sea level rise) and thermal expansion (warmer water takes up more space)
Due to warmer oceans -> more frequent and stronger storms
This would increase rate of erosion, risk of mass movement

Question 20

Give examples of hard and soft engineering and give pros and cons

Answer 20

Hard: groynes (builds up beach, starves other areas of coastline), sea walls (expensive, protects building, cliffs)
Soft: beach replenishment (sand reduces wave energy maintaining tourism, expensive), slope stabilisation (reduces slippage, foot of cliff still needs protection from waves)

Question 21

State the pros and cons of ‘doing nothing’ in coastal management

Answer 21

+ costs nothing
+ new natural environments may be created
- expensive to pay for new homes, businesses if damaged
- people may lose their homes, businesses
- visual problems for an unmanaged coast