Coastal processes and landforms

Question 1

Onshore coast

Answer 1

60km inland

370km out to sea

Question 2

Constructive waves

Answer 2

longer wavelength
strong swash
weak backwash
shallow gradient waves
beach builds up

Question 3

Destructive waves

Answer 3

short wavelength
weak swash
strong backwash
steep gradient waves
erodes beach

Question 4

attrition

Answer 4

sea carries rocks which knock against each other

the force breaks and chips the rocks so they become smaller and more rounded

Question 5

abrasion

Answer 5

waves pick up stones and hurl them at cliffs

this wears down the rock surface

Question 6

solution

Answer 6

sea water dissolves certain rocks

Question 7

hydraulic action

Answer 7

the force of the waves hitting against the cliff forces pockets of air into the cracks and crevices, weakening the rock

Question 8

biological weathering

Answer 8

animals burrowing or roots growing inside the bedrock of the cliff face, expand and weaken the rock until it breaks off

Question 9

physical weathering

Answer 9

freeze-thaw
- water fills a crack in a rock, freezes and expands 9%. This repeats, the crack widening until scree breaks off

haloclasty
- salt crystals build up in cracks, expanding and weakening the rock until the scree breaks off

Question 10

Chemical weathering

Answer 10

carbonation
- atmospheric CO2 reacts with water to make carbonic acid CO2 + H2O -> H2CO3
This acid rain reacts with calcium carbonate in certain rock(e.g. limestone), dissolving it
H2CO3 + CaCO3 -> Ca(H2CO3)2

Question 11

rock fall

Answer 11

fragments of rock break away from cliff face due to weathering

Question 12

landslide

Answer 12

erosion forms a wave-cut notch at the base of the cliff

the weight of the cliff can’t support itself and collapses

Question 13

mud slide

Answer 13

saturated soil and weak rock flows down a slope

Question 14

slumping

Answer 14

rain infiltrates cliffs made up off soil and boulder clay
the pore pressure is increased
the weight of the saturated cliff causes a rotational movement along a curved slip plane

Question 15

Longshore drift

Answer 15

1. prevailing winds blow in from an oblique angle
2. this causes the swash of waves to move diagonally up the beach, moving sediment as well
3. backwash moves material down the gradient of the beach at a right angle due to gravity
4. process repeats, moving sediment up the coast
5. until sediment is deposited at the river mouth

Question 16

Headlands

Answer 16

1. At discordant coastlines, differential erosion occurs, so less resistant(sand and clay) rock retreats quicker
2. harder rock(chalk) is left protruding as a headland
3. waves refract around the headland, concentrating their orthogonal energy on the sides
4. This further erodes the headland

Question 17

Caves

Answer 17

Erosion on the sides of the headland widen the crack due to the concentrated orthogonal energy after the waves have refracted round

Question 18

Arch

Answer 18

erosion continues, cave becomes larger and breaks through headland

Question 19

Stack

Answer 19

Base of arch widens until the roof becomes too heavy to support itself and collapses into the sea, leaving a pillar of rock

Question 20

Stump

Answer 20

stack is undercut at the base, weakening the structure until it eventually collapses

Question 21

Rjas

Answer 21

drowned river valley

Question 22

Fjords

Answer 22

drowned glacial valleys

Question 23

Spit

Answer 23

deposited material at river mouth created by longshore drift

eg. spurn head

Question 24

Wave-cut platform

Answer 24

Sea erodes at the base of the cliff at high tide to create a wave-cut notch
as notch increases in size, the cliff becomes unstable and collapses, leading to the retreat of the cliff face
backwash carries away the eroded deposit, leaving a wave-cut platform

Question 25

bar

Answer 25

spit formed across a bay

e.g. Slapton

Question 26

tombolo

Answer 26

spit joins the land to and island

e.g. chesil beach

Question 27

Cuspate foreland

Answer 27

deposition in an area where two opposing longshore drifts meet(triangle)

Question 28

4 Hard engineering examples

Answer 28

recurved steel wall(reflects energy)
gabion - steel wire mesh cage filled with small rocks
riprap - large boulders(rock armour)
groyne - traps sediment carried by LSD

Question 29

4 Hard engineering disadvantages

Answer 29

expensive to build and maintain
can’t keep up with pace of rising sea levels
visual pollution
terminal groyne syndrome
- starves beach further down the coast, increasing rate of erosion elsewhere

Question 30

6 Soft engineering examples

Answer 30

beach nourishment
cliff regrading and drainage- reduce mass movement
dune regeneration- marram grass planted to trap sand
salt marsh conservation
reprofiling-sediment moved from lower to upper beach
fencing, hedging and replanting vegetation

Question 31

Reasons for managed retreat

Answer 31

political policy of austerity
- limited funding for engineering
eustatic yearly sea rise of 3mm
- pressure of engineering
isostatic readjustment
- sea taking over combats southeast sinking
creates new salt marshes(carbon sinks)

Question 32

Mass movement

Answer 32

bulk movements of soil and rock debris down slopes in response to the pull of gravity

4 types:
rock fall
slumping
landslide
mudslide