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Physical geography > Coastal landscapes > Flashcards

Coastal landscapes Flashcards

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1
Q

What are inputs?

A

sediment entering a system, energy inputs come from wind, waves tides and currents

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2
Q

What are outputs?

A

sediment washed out to sea, or deposited further along the coast

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3
Q

What are flows/ transfers?

A

processes such as erosion, weathering, transportation and deposition - move within the system

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4
Q

What are stores/ components?

A

landforms - beaches, dunes, spits (stores of sediment)

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5
Q

What is dynamic equilibrium?

A

inputs and outputs are
balanced - a change in either causes negative feedback - restores balance

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6
Q

What is a negative feedback loop, and an example of one?

A

change in a system causes more changes that have opposite effects - eg. a beach is eroded - cliffs behind exposed to wave damage - sediment then is deposited leading to growth of beach

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7
Q

What is a positive feedback loop, and an example of one?

A

change in a system causes more changes that have a similar effect - eg. as a beach begins to form - slows down waves - cause more sediment to be deposited - increasing size of beach - new equilibrium is reached - long-term growth of beach stops

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8
Q

How is wind formed?

A

created by air moving from areas of high pressure to areas of low pressure - storms increase gradient pressure (difference between high and low pressure) - winds become very strong

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9
Q

How does wind affect the sea?

A

strong wind can create powerful waves - consistent wind from one direction (prevailing winds) causes higher-energy waves

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10
Q

How are waves created?

A

wind blowing over the sea, friction creates a circular motion

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11
Q

Effect of waves on the shore

A

depends on the height of the wave
- wave height depends on wind speed and fetch
- high wind speed and large fetch creates powerful waves

. as waves approach the shore they break - friction with sea bed slows them down - crest of wave rises then collapses (water gets flatter as it reaches land)

. swash and backwash

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12
Q

Constructive wave

A

low frequency, low and long (elliptical cross profile) powerful swash carries and deposits material up the beach

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13
Q

Destructive wave

A

high and steep, circular cross profile, higher frequency - strong backwash removes sediment from beach

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14
Q

Tide characteristics

A

. periodic rise and fall of the oceans surface, gravitational pull of the moon and the sun
. affects positions at which waves break
. area of land between max high tide and min low tide - most landforms are destroyed

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15
Q

High energy coastline characteristics

A

high inputs of energy - large powerful waves (strong winds, large fetch, steeply shelving offshore zones)
- sandy coves, rocky landforms
- rate of erosion higher than rate of deposition
(Holderness coast)

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16
Q

Holderness coast case study - key facts

A

. East Yorkshire
. 61 km long
. Flamborough head to Spurn head
. most cliffs - boulder clay - powerful destructive waves (North Sea)

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17
Q

Coastal processes Holderness coast

A

EROSION - soft boulder clay - easily eroded (wave action) eg, Great Cowden - rate of erosion 10 m/ year
MASS MOVEMENT - boulder clay prone to slumping - water makes it heavier (lubricant between particles) - unstable
TRANSPORTATION - prevailing winds (northeast transport material south) - ocean current - transports material (longshore drift) - rapid erosion - lots of sediment
DEPOSITION - ocean current meets outflow of Humber River - flow becomes turbulent - sediment deposited

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18
Q

Landscapes on the Holderness coastline

A

North - steep chalk cliffs, wave-cut platforms & sandy beaches
South - less-steep boulder clay cliffs
Spurn Head - depositional features

Headlands & wave-cut platforms - chalk is less easily eroded - formed a headland (Flamborough Head) -features stacks, caves and arches - wave cut platforms (Sewerby)

Slumping cliffs - slumps have occured not yet eroded - tiered cliffs (Atwick Sands)

Beaches - south of Flamborough Head - sheltered from wind and waves (wide sand beach -Bridlington)

Sand dunes - Spurn Head - material transported (winds) deposited

Spit - erosion & longshore drift - recurved end (Humber Estuary) Spurn Head - landward side - mudflats and saltmarshes formed

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19
Q

Management of Holderness coastline

A

retreated by 4 km (2000 years) - 30 villages have been lost
social, economic & environmental :
. loss of settlements and livelihoods
. loss of infrastructure
. loss of sites of special scientific interest

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20
Q

Hard Engineering at Holderness

A

. 11.4 km is protected by hard engineering
. Bridlington - 4.7km sea wall & timber groynes
. Hornsea - concrete sea wall, timber groynes & riprap
. rock groynes - 500m long revetment (Mappleton) - 1991 (£2 million) - protect the village
. Skipsea - gabions
. Withernsea - groynes & sea wall - riprap placed in front of wall due to storms 1992
. Easington Gas terminal - revetment
. east of Spurn Head - groynes & rip rap

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21
Q

Are existing schemes sustainable - Holderness Coastline

A

Groynes - trap sediment - increase width of beach (protects local area) - increases erosion of cliffs - downdrift
Sediment - washed into Humber estuary (tidal mudflats) - reduction of sediment increases risk of flooding- increases erosion
Protection of local areas - formation of bays - wave pressures on headlands increase - cost of maintaining sea defences may become too high

These make existing schemes unsustainable

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22
Q

challenges for all possible schemes

A
  • SMP - suggest doing nothing - not popular with owners of land
  • Managed realignment - relocating things further inland - more sustainable - causes issues to businesses to relocate
  • Holderness council - stop trying to protect Spurn Head - saves more money - spit functions naturally - overwashing may damage marsh environments
  • Easington Gas Terminal - protected by rock revetments - village of Easington isn’t protected - increase erosion
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23
Q

sediment sources in coastal systems

A

Inputs:
. rivers carry eroded sediment from inland
. sea level rise - flood river valleys (estuaries)
. sediment eroded from cliffs (waves)
. formed from crushed shells of marine organisms
. transport sediment into coastal zone from offshore deposits

24
Q

sediment cells

A

If more sediment enters than leaves (positive sediment budget) - coastline builds outwards

If more sediment leaves than enters (negative sediment budget) - coastline retreats

Lengths of coastline - self-contained for movement of sediment - process going on in one cell (don’t affect the movement of sediment in another cell) - closed coastal system

25
Q

How do waves erode the coastline?

A

Corrasion (abrasion) - sediment transported by waves smashing and grinding against the rocks - breaking bit off and smoothing surfaces

Hydraulic action - air in cracks, compressed - exerting pressure on rock (Pieces break off)

Cavitation - waves recede, compressed air expands violently - pressure on rock - causing rock to break off

Wave Quarrying - energy of wave breaks against cliff enough to detach bits of rock

Solution (corrosion) - soluble rocks gradually dissolve by seawater

Attrition - rock smash against each other break into smaller pieces

26
Q

Transportation - moving of eroded material

A

Solution:
- dissolved carried along in
the water (limestone)
Saltation:
- larger particles (pebbles) too heavy - force of water causes them to bounce along sea bed
Suspension:
- very fine material (clay) whipped up by turbulence carried along in water
Traction:
- very large materials pushed along sea bed

27
Q

What is longshore drift?

A

Swash carries sediment up the beach parallel to prevailing wind - backwash carries sediment back down the beach (right angles) to the shoreline

angle between prevailing wind & shoreline - move the sediment along the shoreline

28
Q

What is deposition?

A

The dropping of eroded material :
marine deposition - carried by seawater and dropped
aeolian deposition - carried by wind and dropped

sediment load exceeds the ability of the water to carry it (sediment load increases) - or water flow slows down

Friction increases - waves enter shallow water or reach land - slows down water or wind

Flow becomes turbulent - encounters obstacles flow becomes rougher overall speed decreases

29
Q

sub-aerial weathering

A

salt weathering:
caused by saline water - enters pores or cracks in rocks (high tide) water evaporates forming salt crystals - expand exerting pressure - causes pieces to fall off

Freeze-thaw weathering :
temperatures fluctuate above and below freezing - water enters cracks, water freezes and expands (weakens rock and breaks)

Wetting and drying:
contain clay - clay expands when wet pressure causes rock to fall off

Chemical weathering:
breakdown of rock by changing its chemical composition

Biological weathering:
plant roots growing into cracks of rock widening and weakening it

30
Q

What is mass movement?

A

the shifting of material downhill due gravity - when cliffs are undercut by wave action (unsupported overhang)

31
Q

3 types of mass movement

A

Landslides, slumping, rockfalls and mudflows (soil creep - gradually moving)

slides - straight line shift
slumps - shifts with rotation
rockfalls - breaks up and falls
mudflows - flows downslope

32
Q

Why does mass movement occur

A

unconsolidated rocks - little friction to hold together
heavy rain - saturate rocks, further reducing friction
runoff - erode fine particles - transport downhill

33
Q

cliffs and wave-cut platforms

A

cliffs retreat due to action of waves and weathering
notch forms (high water mark) - forms a cave
rocks become unstable (nothing below to support)
wave- cut platforms (flat surfaces) left behind

Flamborough - Holderness coast

34
Q

Headlands and bays

A

form - bands of alternating hard and soft rock
soft rock is eroded faster- leaving harder rock as a headland

Swanage Bay - Dorset

35
Q

Caves, arches and stacks

A

cliff profile features - weak areas form into caves - caves form arches as they break through headlands
arch collapse due to weathering and forms a stack
stacks erode and become stumps

Old Harry and his wife - Dorset

36
Q

Beaches

A

constructive waves deposit sediment (store in coastal system)
shingle (steep and narrow) - large particles
sand (wide and flat) - smaller particles

37
Q

Spits

A

when coast suddenly changes direction
- longshore drift - continues - simple spit (straight spit)
recurved end - changes to dominate wind and wave direction curve the end of spit
compound spit - multiple recurved ends
behind the spit mudflats and saltmarshes develop

38
Q

offshore bars and tombolos

A

when a spit joins two headlands together (across a bay or river mouth)
creating a lagoon behind the bar
offshore bars - formed when material moves towards coast (partly submerged)
tombolo - bar that connects shore to an island

Bar - Slapton sands - Torcross (Devon)

39
Q

barrier beaches

A

parallel beaches detached from shore - good supply of sediment, gentle slope offshore, powerful waves and small tidal wave
rapid ice melt - sea levels rise , flooding land behind - transported sediment to shallow water

lagoons or marsh forms behind (sheltered from wave action)

40
Q

Sand dunes

A

sand deposited by longshore drift - moves up beach
trapped by objects on beach (stabilising sand encouraging more to build up) - embryo dunes

41
Q

estuarine mudflats and saltmarshes

A

form in sheltered, low- energy environments
silt and mud deposited (mudflats)
colonised by vegetation - survive high salt levels and submergence
plants - trap more mud and silt - exposed areas
erosion forms channels in surfaces (permanently flooded or dry at low tide)

42
Q

What is eustatic sea level change

A

caused by a change in volume of water (or shape of ocean basin)

43
Q

causes of eustatic sea level change

A
  1. changes in climate -
    . increase in temp (causes melting of ice sheets and expansion of water molecules - increases sea levels)
    . decrease in temp causes precipitation to fall as snow - increases volume of water in glaciers - reduces in sea levels (decreases)
  2. tectonic movement -
    . alter shape of basin (sea floor spreading increases the volume of the basin - decreases sea level)
44
Q

What is isostatic sea level change?

A

caused by vertical movements of the land relative to the sea.
- any downward movement of the land causes rise of sea level - upward movement of land causes fall of sea level

45
Q

effects of isostatic sea level change

A
  1. uplift or depression -
    . earth crust moves due to melting of ice sheets
    . accumulation of sediment can cause depression
  2. subsidence -
    . due to shrinkage after abstraction of groundwater (drainage of marshland)
  3. tectonic -
    . as one plate is forced beneath another at a plate margin
46
Q

How have sea levels risen in the last 10,000 years? (temporary)

A

sea levels vary due to the tidal cycle, onshore winds and low atmospheric pressure systems (temporary)

47
Q

How have sea levels risen on a longer time scale?

A

. last glacial period - water stored in ice sheets (sea level lower than now) (130m lower)
. temps started to increase and sheets melted - sea levels rose dramatically

48
Q

how has climate change affected sea levels?

A

sharp rise in temp due to human activities (increased concentration of greenhouse gases - which absorb outgoing long-wave radiation (less is lost to space) - concentrated increases - more energy is trapped - warms up planet
increases sea levels - melting ice caps & expansion of water molecules

49
Q

climate change and its impacts on coastal areas

A
  1. storms become more frequent and intense due to changes in ocean circulation and wind patterns (damage to ecosystems and settlements)
  2. sea levels rise and increased storminess - increase coastal erosion `
50
Q

sea level rising; impacts on coastal areas

A

. more frequent and more severe coastal flooding (New York - 2005-2014 flooded 160 times)
. submerged of low-lying islands - at risk of disappearing (0.5 rise could submerge Maldives)
. changes in the coastline - islands created - area of land decreases
. contamination of water sources and farmland - salt may enter - damaging ecosystems - enter soils - impossible to farm

51
Q

how can the fall in sea level result in emerging coastlines?

A

. raised beaches - fall in sea level leaves beaches above high tide - sediment becomes vegetated (soil)
. wave-cut platforms - raised above former level
. relict cliffs - cliffs above raised beaches - gradually degraded over time

52
Q

how does the rise in sea level result in the submergence of coastlines, what landforms are created?

A
  1. Rias - river valleys partially submerged - gentle long and cross profile (wide and deep at mouth) - narrower and shallower (further inland)
  2. Fjords - drowned glacial valleys (straight and narrow - steep sides) - shallow mouth (threshold (raised ground)) very deep inland
  3. Dalmatian coastlines - valleys lie parallel, valleys flooded leaving islands
53
Q

what are the four options for coastal management?

A
  1. hold the line - maintain existing defences
  2. advance the line - build further defences further out to sea
  3. do nothing - build no defences, deal with erosion and flooding as it happens
  4. managed realignment - allow shoreline to move, but manage retreat - cause less damage
54
Q

hard engineering

A

defences built by man to protect coastlines

55
Q

soft engineering

A

defences involving coaxing natural processes along

Physical geography (5 decks)

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