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Physical Geography 🌋 > Coasts 🌊 > Flashcards

Coasts 🌊 Flashcards

1
Q

outline a coastal system

A

open system

inputs - sediment and energy
outputs - sediment washed to sea or another cell
stores - landforms
flows - wind and water transport

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2
Q

inputs in a costal system

A

sediment
- rivers
- cliff erosion
- longshore drift
- wind

energy
- wind
- waves
- currents
- tides

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3
Q

outputs in a coastal system

A

sediment
- washed out to sea, deposited further along shore

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4
Q

flows and transfers in a coastal system

A

erosion
transportation
deposition
wind
LSD
weathering

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5
Q

stores in a coastal system

A

landforms
- beaches, dunes, spits

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6
Q

negative feedback in coastal system

A
  • beach eroded
  • cliffs exposed to wave attack
  • sediment eroded
  • eroded sediment deposited on beach
  • beach grows again

or
- cliff being eroded
- leads to mass movement
- collects at bottom of cliff
- protect base from wave energy
- reduced erosion

or
- cliff eroded
- wave cut platform created
- cliff retreats
- eventually out of reach of waves
- reduced erosion

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7
Q

positive feedback in a coastal system

A
  • beach forms
  • slows down waves
  • more sediment is deposited (not enough energy)
  • beach grows more
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8
Q

sources of energy

A
  • wind
  • waves
  • tides
  • currents
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9
Q

wind

A

air moving from high to low pressure
responsible for waves and some currents
prevailing wind (consistantly same direction) creates higher energy waves
(than changing winds)

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10
Q

role of wind

A

source of energy

creates waves and currents

can transport material

agent in erosion - abrasion

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11
Q

waves

A

created by friction as wind blows over surface of sea
creates circular motion

wave height depends of wind speech and fetch

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12
Q

what is wave refraction?

A

where waves bend as they approach an indented coastline
- eg a headland
waves approaching headland reach shallower water before waves approaching bay
wave energy becomes concentrated around the headland
waves in bay spread out - less frequent

results in energy concentrated around headland, creates erosional landforms
and constructive impacts in bays, beaches

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13
Q

why do waves break

A

break as they get close to shore
friction with seabed slows down bottom of waves
motion becomes more elliptical
crest rises and collapses

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14
Q

constructive waves

A

low frequency
- 6-8 per minutes

long wavelength
low wave height

powerful swash and weak backwash

deposition

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15
Q

destructive waves

A

higher frequency
10-14 per minute

short wavelength
high and steep height

strong backwash weak swash

erosion

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16
Q

factors affecting wave energy

A

wind:
- strength
- duration
- fetch (distance)

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17
Q

tides

A

periodic rise and fall of ocean surface
due to gravitational pull of sun and moon

affects position waves break on beach

high tidal range = energy less concentrated, position wave break varies
low tide range = energy more concentrated on certain areas

NOT caused by wind

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18
Q

spring tides

A

highest tides
sun and moon in line with earth - stronger gravitational pull

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19
Q

neap tides

A

lower tides
sun and moon at right angles to earth - weaker pull

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20
Q

currents

A

general flow of water in one direction
caused by WIND, change in water temperature or salinity

move material along coast
- localised

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21
Q

sources of energy importance

A

wind most important
creates waves and currents
- localised impacts

tides not generated by wind
- global impacts

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22
Q

low energy coasts

A

low inputs of energy
small, gentle waves
- light winds (sheltered area)
- short fetch

rate of deposition higher than erosion

creates salt marshes and mudflats

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23
Q

high energy coasts

A

high inputs of energy
large, powerful waves
- strong winds
- long fetches

rate of erosion higher than deposition

creates rocky landforms, caves, arches etc

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24
Q

sources of sediment (inputs)

A
  • rivers
  • cliff erosion
  • longshore drift
  • wind
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25
Q

sediment budgets

A

the balance between inputs and outputs of sediment in a system
(difference between them)

can be positive (more enters, beach builds)
or negative (more leaves, beach retreats)
when balanced = dynamic equilibirum

disturbed by climate change and human intervention

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26
Q

sediment cells

A

lengths of coastline (between 2 headlands or estuaries) that are closed coastal systems
Mostly self contained movements of sediment

(Sediment may move in strong waves)

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27
Q

how does climate change impact sediment cells?

A

rising sea levels and more frequent storms = more erosion
more inputs of sediment

glacial melt = more inputs

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28
Q

how does traditional management impact sediment cells?

A

hard engineering prevent natural processes of erosion

reduce outputs of sediment - traps it to build up beaches
therefore reduces inputs of sediment down coast
eg groynes in Happisburgh

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29
Q

how do SMPs impact sediment cells?

A

focus on individual cells
however advance and hold the line can impact inputs and outputs

managed retreat and do noting can restore dynamic equilibrium

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30
Q

processes of erosion

A

corrasion
solution
hydraulic action
cavitation
attrition
wave quarrying

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31
Q

corrasion

A

sediment transported by waves thrown against cliffs
smash and rind against rock

32
Q

solution

A

soluble rocks get dissolved in seawater
eg limestone

33
Q

hydraulic action

A

air in cracks in cliffs compressed by waves crashing
pressure caused bits to break off, crack widens

34
Q

cavitation

A

waves receed, compressed air expands violently
creates pressure
bits break off, crack widens

35
Q

attrition

A

rock and sediment in water smash against each other
make smaller particles

36
Q

wave quarrying

A

energy of wave breaking on cliff
breaks bits off

37
Q

how does lithology affect cliff erosion?

A

seaward dipping bedding planes
- means loose material can slide down the bedding planes
= less stable so more vulnerable

landward dipping bedding planes
= relatively steep and stable, less vulnerable

38
Q

transportation

A

solution
saltation
traction
suspension

39
Q

solution

A

substances are dissolved and carried in water
eg limestone

40
Q

suspension

A

very fine material carried along in water (above seabed)
eg silt and clay

41
Q

saltation

A

larger particles (can’t be suspended) bounce along seabed by force of water
eg pebbles and gravel

42
Q

traction

A

very large particles pushed along seabed (rolled) by force of water
eg boulders

43
Q

what is deposition

A

when material being transported is dropped on the coast

44
Q

causes of deposition

A

happens when sediment load exceed the ability of the water to carry it

due to
sediment load increases eg landslide
water loses energy
- friction increases, shallow water, slows
- conflicting currents, slows

45
Q

sub aerial weathering

A

gradual breakdown of rocks in situ
weakens cliffs, more vulnerable to erosion

  • chemical
  • biological
  • mechanical. freeze thaw, wetting and drying
46
Q

chemical weathering

A

breakdown of rocks by changing its chemical composition

carbonation
- carbon dioxide dissolves in rain to form acid rain
- dissolves rocks containing calcium carbonate eg limestone

solution
- dissolved

oxidation - iron minerals in rock react with oxygen and rust = breakdown

47
Q

biological weathering

A

plant roots growing into cracks, widens
animals building burrows

48
Q

mechanical weathering

A

freeze thaw
- happens where temperatures fluctuate around 0
- water enters cracks
- freezes as it expands
- overtime, weakens and breaks off

wetting and drying
- rocks that contain clay
- gets wet, expands
- creates pressure causing bits to break off

Salt crystallisation
- water collects in cracks
- sun causes water to evaporate, leaves crystals
- salt crystals bigger and grow = pressure in cracks so break up

49
Q

what is mass movement?

A

movement of material downhill due to gravity

unconsolidated rocks prone to collapse, less friction to hold together
heavy rainfall saturates rocks, reduces friction
runoff can also move fine sediment

  • creep
  • slide
  • slump
  • rockfall
  • mudflow
50
Q

creep

A

soil particles get wet
less friction
slowly move downslope

51
Q

landslide

A

happens when wet, less friction
downhill movement of material ‘en masse’
moves rapidly

52
Q

slump

A

softer material overlies more resistant
material moves downhill
creates a curved indented surface

53
Q

rockfall

A

rocks on a vertical cliff face
mechanical weathering, weaken and dislodge rocks
large parts breaks off and collect at bottom as scree

54
Q

mudflow

A

mud on a hill slope
rainfall saturated soil, increases pressure and particles heavier
sediment flows downhill

55
Q

longshore drift

A

moves sediment along shore

  • swash carries sediment up beach at similar angle to prevailing wind
  • backwash moves sediment back down beach at right angles to shoreline
    = zig zag movement
56
Q

marine processes

A

transportation
Erosion
Deposition

57
Q

sub aerial processes

A

weathering
mass movement

58
Q

eustatic sea level change

A

rise or fall in sea level
caused by a change in the volume of water in ocean basin
- global effects

59
Q

causes of eustatic sea level change

A

climate change/ice melt
- increase in temperature
- ice sheets melt
- increases volume - levels rise

  • decrease in temperature
  • more precipitation falls as snow
  • increased storage in cryosphere
  • decreased volume - levels fall

thermal expansion of water
- warmer water expands - levels rise

tectonic movements
- alters shape of basin
- mid ocean ridges, new land formed
- displaces water - levels rise

60
Q

isostatic sea level change

A

rise or fall in sea level
caused by vertical movements of the land relative to the sea
- effects are local

61
Q

causes of isostatic sea level change

A

glaciation causing depression of crust
- weight of glaciers and ice presses down crust into asthenosphere - levels rise

post glacial readjustment
- uplift of earths crust as glaciers melt, asthenosphere rebounds - levels fall

tectonic activity
- causes land to move up or down

62
Q

coastline of emergence

A

when sea levels fall relative to coast = emergent landforms

raised beaches - beach above high tide mark, over time become vegetated

marine platforms - exposed wave cut platforms

relict cliffs - cliffs above raised beaches, no longer eroded by sea, exposed to weathering

63
Q

coastline of submergence

A

when sea levels rise relative to coast = submergent landform

rias
fjords
Dalmation Coastine

64
Q

formation of a ria

A

river valleys are partially submerged

wide and deep at mouth, shallower inand
much wider than natural river mouth

eg Exemouth, River Exe

65
Q

formation of a fjord

A

drowned glacial valleys
eroded by glaciers in glacial times

straight and narrow with steep sides
very deep

eg Sognefjorden, Norway

66
Q

formation of a Dalmatian Coastline

A

islands parallel to coastline

caused by flooded valleys lying parallel to coast
ridges at different heights, lower areas flooded and higher left exposed

eg Dalmatian Coast, Croatia

67
Q

sea levels over 10,000 years

A

glacial period, max 18,000 ya
- more water stored in cryosphere
- sea levels lower

temperature increased, started 12,000 ya
- ice melted
- sea levels rose to current
about 130m higher now

since 1930, levels rising more
- climate change

68
Q

impacts of climate change on sea levels

A

global warming - human activities, more greenhouse gases

increased temperature
- more thermal expansion
- more ice melt
(eustatic)

69
Q

impacts of climate change on coastal areas

A

warmer tempertures = more frequent and intense storms
- damage to coastal ecosystems and settlements

rising SLs = more frequent and severe flooding
- contamination of bodies of freshwater
- damage to settlements
- salinisation of soils, crop damage

submergence of low lying islands

70
Q

how does feedback help with management?

A

ICZM aims to restore equilibrium

climate change = + feedback
needs to be managed

71
Q

chi squared

A

if critical smaller than calculated
= null rejected
(there is a significant difference)

if calculated smaller
= null excepted
(no significant difference)

72
Q

impacts of geology on coastal processes

A

erosion
- hard rock (granite) more resistant than soft
= discordant coastlines

weathering
- softer rock/ certain types more vulnerable to weathering
- eg limestone and chemical

mass movement
- soft = more unconsolidated so more saturated when it rains
= heavier so mass movement more likely

transportation
- more sediment to move

deposition
- more sediment = increased load
= more deposition
- scree at base of cliffs slows erosion to create deposition

73
Q

impacts of energy on coastal processes

A

erosion
- high energy = more erosion as creates destructive waves
- compared to more deposition at low energy

weathering
- more erosion = more cracks so more vulnerable to weathering

mass movement
- high energy = more vulnerable as material losened by erosion and weathering

transportation
- high energy = more movement of sediment

deposition
- high energy = less deposition, strong backwash
- low energy = more deposition as less energy to carry

74
Q

impacts of management on coastal processes

A

erosion
- absorbs wave energy to reduce rates
- can increase rates down coast

weathering
- protected from mechanical
- but exposed to chemical and biological

mass movement
- cliffs more stable as eroded less, reduced risk
- but still vulnerable after heavy rainfall, saturation

transportation
- groynes reduce movement by offshore drift

deposition
- some forms encourage deposition to protect cliffs and absorb energy
- eg beach nourishment

75
Q

impacts of erosion on coastal processes

A

weathering
- creates cracks so more vulnerable

mass movement
- weakens and loosens material

transportation
- creates more sediment to move

depostion
- more sediment removed by destructive waves

76
Q

impacts of weathering on coastal processes

A

erosion
- more weathering = weaker and unconsolidated rocks = more vulnerable

mass movement
- less consolidated = more likely
- means water can infiltrate

transportation
- create more lose material to be transported

deposition
- material collects at base of cliffs, slows waves = deposition

Physical Geography 🌋 (21 decks)

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