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Physical geography > Coastal landscapes > Flashcards

Coastal landscapes Flashcards

(55 cards)

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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

Study These Flashcards
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

Study These Flashcards
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
How do waves erode the coastline?
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
Transportation - moving of eroded material
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
What is longshore drift?
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
What is deposition?
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
sub-aerial weathering
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
What is mass movement?
the shifting of material downhill due gravity - when cliffs are undercut by wave action (unsupported overhang)
31
3 types of mass movement
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
Why does mass movement occur
unconsolidated rocks - little friction to hold together heavy rain - saturate rocks, further reducing friction runoff - erode fine particles - transport downhill
33
cliffs and wave-cut platforms
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
Headlands and bays
form - bands of alternating hard and soft rock soft rock is eroded faster- leaving harder rock as a headland Swanage Bay - Dorset
35
Caves, arches and stacks
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
Beaches
constructive waves deposit sediment (store in coastal system) shingle (steep and narrow) - large particles sand (wide and flat) - smaller particles
37
Spits
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
offshore bars and tombolos
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
barrier beaches
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
Sand dunes
sand deposited by longshore drift - moves up beach trapped by objects on beach (stabilising sand encouraging more to build up) - embryo dunes
41
estuarine mudflats and saltmarshes
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
What is eustatic sea level change
caused by a change in volume of water (or shape of ocean basin)
43
causes of eustatic sea level change
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
What is isostatic sea level change?
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
effects of isostatic sea level change
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
How have sea levels risen in the last 10,000 years? (temporary)
sea levels vary due to the tidal cycle, onshore winds and low atmospheric pressure systems (temporary)
47
How have sea levels risen on a longer time scale?
. 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
how has climate change affected sea levels?
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
climate change and its impacts on coastal areas
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
sea level rising; impacts on coastal areas
. 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
how can the fall in sea level result in emerging coastlines?
. 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
how does the rise in sea level result in the submergence of coastlines, what landforms are created?
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
what are the four options for coastal management?
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
hard engineering
defences built by man to protect coastlines
55
soft engineering
defences involving coaxing natural processes along

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