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Physical Geography > Coast Landscapes and Change > Flashcards

Coast Landscapes and Change Flashcards

1
Q

How is a wave created

2B.4

A

created through friction between the wind surface, transferring energy from the wind into the water

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2
Q

what is a wave

2B.4A

A

transfer of energy from one water particle to its neighbour with individual water

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3
Q

what is wave height

2B.4A

A

vertical distance from the peak to trough

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4
Q

how is wave height determined

2B.4A

A

energy transfer from the wind and water depth

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5
Q

what is wave length

2B.4A

A

horizontal distance from crest to crest

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6
Q

what is wave frequency

2B.4A

A

number of waves passing a particular point over given period of time

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7
Q

waves in a open sea

2B.4A

A
  • waves are simply energy moving through water
  • water itself only moves up and down not horizontal
  • there is some obital water particle motion within the wave but no net forward water particle motion
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8
Q

what does wave size depend on

2B.4A

A

wave fetch -
wave depth
strength of wind
duration of wind blows

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9
Q

how does a wave break

2B.4A

A

waves reaching shore reach a wave depth 1/2 their wavelength the internal orbital motion of water within the wave touches the sea bed
Wave particle is distorted due to friction between the sea bed, this slows down the wave
- wave depth decreases further, wave velocity slows wavelength shortens and wave height increases.
- wave crest begins to moe forwards much faster than the wave trough
- wave crest outruns the trough and wave topples forwards
wave breaks in the nearshore zone and water flows up the beach as swash
wave losses energy and gravity pulls the water back down the beach as backwash

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10
Q

Constructive Waves

2B.4A

A 
low energy waves 
low flat wave height 
long wavelength 
low wave frequency (6-9 per minute)
strong swash - pushes sediment up the beach but weaker backwash can't transport all particles back 
- backwash into beach material
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11
Q

Destructive Waves

2B.4A

A

high energy waves
large wave height
short wavelength
high wave frequency
strong backwash weak swash due to steep angle of impact = energy directed downwards and backwards
strong backwash erodes material from top of beach

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12
Q

what is beach morphology

2B.4A

A

shape of the beach

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13
Q

what is a beach sediment profile

2B.4A

A

pattern of distribution of different sized or shaped deposited material

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14
Q

how do constructive waves effect beach morphology

2B.4A

A

net movement of sediment up the beach steeping the beach profile
Produce berms at the point where swash reaches high tide line
swash carries sediment of all sizes up the beach but weaker backwash can only transport smaller particles down the beach = larger heavier shingle at back of beach and sand closer to ocean -> backwash flows down beach loses energy through friction = sediment further sorted = fine sands closest to sea - coarser sands deposited in middle of beach

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15
Q

what is a berm

2B.4A

A

ridge of material across the bridge

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16
Q

how do destructive waves effect beach morphology

2B.4A

A
  • beach gradient reduced due to weak swash and powerful backwash which produces sediment down the beach
  • some sediment thrown forwards by strong waves
  • large pebble sized sediment dragged down the beach by backwash to form wide ridge of material below
  • friction could cause backwash to down some sediment on middle or lower beach = deposited size sediment decreasing towards sea
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17
Q

Decadal Variation - Beach Morpholgy

2B.4A

A

Climate change is expected to produce more extreme
weather events in the uk
winter profiles may be present for longer time over course of year
more frequent powerful destructive waves reduce beach size = high tides to reach inland = rate of erosion increase

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18
Q

Monthly Variation - Beach Morphology

2B.4A

A

Highest tide occurs every 2 months at spring tide - two very low high. tides
As months progress from spring down to neap tides - lower high tides produce series of berms at lower and lower points down the beach
Berms destroyed as material pushed further up beach - once a neap tide passes and moves towards next spring tide

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19
Q

Daily Variation

2B.4A

A

Destructive waves from storms in summer reshape beach
Constructive waves = calm conditions in winter
Wind Drops = destructive waves -> constructive waves
Storm beaches = result from high energy deposition of sediment from sever storms

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20
Q

what does energy transferred from the wind depend on

2B.4A

A

wind strength
wind fetch
uninterrupted distance upon water over which wind blows over
wind duration

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21
Q

how are sea waves produced

2B.4A

A

winds currently blowing in local area - vary in height and direction

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22
Q

what happens when the wind drops

2B.4A

A

wave energy continues to be transfers across ocean in the form of swell waves

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23
Q

Swell Waves

2B.4A

A

absorb smaller sea waves and gain energy and height as they travel
travel long distances before they lose energy
produce waves at coast even with no wind
can form periodically larger waves amongst smaller

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24
Q

Name the 4 erosion processes

A

Hydraulic Action
Corossion
Abrasion
Attrition

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25
Q

Effect of Erosion

A

Boudle clay of the Holderness coast retreated by 120cm in last 100 years
Granite of Lands End in Cornwall has retreated by only 10cm in last 100 years

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26
Q

How the 4 erosions are influences by wave type, size and lithology

A

Most effective during storms events with large destructive waves
Coastlines of soft sediment experience little erosion under normal conditions
Most erosion in UK in winter high energy storms

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27
Q

what does hydraulic action do and where it occurs

A

force of water itself breaks up rock

occurs through direct impact of the water itself

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28
Q

Hydraulic Action and Destructive waves

A

plunging destuctive waves can exert a force of 50KG

sufficer tor break off material from unconsolidated material - boulder clay

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29
Q

Process of Hydraulic Acton

A

force of breaking waves compresses air into crack \
wave energy exhausted, the compressed air explodes outwards = fractures in rocks
over time small fragments of rock break away or main rock is weak enough too all

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30
Q

Hydraulic action is igneous rock

A

hydraulic action attacking its cooling joints only effective wave erosion process

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31
Q

What is abrasion

A

wave picks up sediment - throws load item against the rock - repeated impact chips away at the rock face until small fragments break away

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32
Q

When is abrasion most effective

A

high energy destructive waves with large wave height hurf load items with greater force = faster rates of erosion by abrasion

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33
Q

what rock erode quickly from abrasion

A

soft sedimentary rock such as chalk mudstones and clays. Unconsolidated material - boulder clay

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34
Q

What is Corrosion

A

Water dissolves rock minerals, minerals carried away by wave in solution - vulernable to erosion by rainwater and sea spray

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35
Q

Most effective waves of Corrosion

A

Constructive

Slow with long wave length (longer the better) prolongs the contact of rock with water

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36
Q

what rocks erode quickly from Corrosion

A

Carbnate rocks like limestones (chalk, jurassic limestone)

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37
Q

what is attrition

A

material transported by wave edged through collision with other low items.

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38
Q

how does attrition break down sediment

A

into smaller sized particles and repeated cousin blunts any of the sharp edges

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39
Q

where does attrition occur

A

in foreshore and nearshore zones, where sediment is moved by swash and backwash

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40
Q

what rocks erode quickly from attrition

A

soft rocks - chalk and clay

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41
Q

how is a wave cut notch formed

2.4BC

A

between hide tide and low tide marks - destructive waves impact against the cliffs

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42
Q

how is wave cut notch eroded

A

hydraulic action and arbasion, sometimes corrosion

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43
Q

wave cut notch example

A

Kimmeridge bay

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44
Q

what is a wave cut platform

A

flat rock surface exposed at low tide - extends from the sea and base of cliff

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45
Q

Formatio of Wave cut platform

A
  • abrasion and hydraulic action erode between high and low tide, which forms notch at the base
  • notch depends by further erosion until material collapses due to gravity, forming a cliff
  • Process is repeated - until coastal recession
  • rock below low tide is always submerged, never exposed to wave impact
  • overlying material eroded , uneroded rock left flat = wave cut platform
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46
Q

wave cut platform extra info

A

slope seaward at 4 degrees
rock pools created by weathering attacking weaknesses at low tide
platform rarely extend more. than hundred metres

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47
Q

Cliffs - Coastal landscapes produced by erosion

Formation of a cliff

A

steep slopes usually unvegetated
hydraulic action dn abrasion forms a wave cut notch
notch deepens until rock collapses due to force of gravity
exposed face forms a cliff

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48
Q

Cave -> Arch -> Stack -> Stump sequence

A
  • joints and faults or dipping bedding planes in rocks are eroded rapidly (hydraulic action)( forms a sea cave)
  • wave refraction concentrates energy on the sides of the headland, producing destructive waves with large wave height
  • A line of weakness extends right through the headland caves form on both sides

marine erosion = cave deepens until they connect up = complete tunnel through the headland and forming an arch

Hydraulic action and abrasion forms wave cut. notches from attacking the side of the arch

mass movement = undercutting of the sides and widening of the arch

Weathering attack the arch roof = roof the arch collapses = leaving seaward end of the headland detached = called a stack

Marine erosion at base stack forms notch on all sides until stack collapses

remnants of the stack base from stump, small projection of rock exposed only low tide

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49
Q

what does cliff slope angle depend on

A

the rip of the rock strata
Horizontal, vertical or landward dip produces steep cliffs
Seaward dip produces a shallower slope angle - can be produced when lithology is unconsolidated

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50
Q

what is traction, and examples

A

where large, heavy load items are rolled along the sea bed

Boulders and cobbles and pebbles

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51
Q

what is saltation, and examples

A

lighter sediment bounces along, sand particles are usually transported this way. Sand can be saltated by wind as well as waves - dry windy day there can be a layer of salivating sand 2-10cm above this beach

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52
Q

what is suspension and examples

A

very light sediment is carried aloft within body of water or air
Silt or Clay particles
Suspended clay particles give sea cloudy, muddy brown colour on soft rock coasts - Holderness

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53
Q

Solution

A

sediment is carried dissolved within the water

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54
Q

Direction of the Wave Attack

A

Main determinant of the direction of the sediment transport
Wind is blowing directly onshore the incoming swash transport the material direction up the beach 90 degrees to the coastline
backwash then transport perpendicularly back down to the beach so its original starting position
Sediment is moved up and down the beach, but there is no lateral

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55
Q

What is longshore drift

A

net lateral transport of material along the coastline when waves approach the coast at an angle

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56
Q

Process of Longshore drift

A

swash transports sediment up the beach
Gradational backwash then transport sediment back down the beach 90 coastline
Sediment particle rests some distance along the beach due to no net lateral movement
Particles moves in zig zag along the beach with the wave

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57
Q

what wave angle produces strongest Longshore drift

A

30 to the coastline, on most coastline their is dominant prevailing wind = over time dominant direction of wind

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58
Q

what is current

A

flow of water in particular direction and can transport sediment in the nearshore and offshore zones

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59
Q

what is current driven by

A

winds, initiated by differences in water density temperature or salinity

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60
Q

global thermohaline - Currents

A

global thermohaline circulation connects four ocean and takes 5000 years for one complete circuit

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61
Q

What is a rip current

A

currents on the beach transport sediment few metres out to sea for a few hours when the wind is blowing directly onshore with the right strength

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62
Q

Tides

A

Incoming and ebbing tide can create tidal currents in the nearshore and offshore zones that transport sediment

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63
Q

prevailing wind

A

most common direction

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64
Q

domaint wind

A

strongest wind direction

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65
Q

where is the dominant wind in the UK

A

North East

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66
Q

UK south coast wind

A

wind from the south west is both dominant and prevaling

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67
Q

what is tidal range

A

distance between high tide and low tide

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68
Q

what does a large tidal range produce

A

strong tidal current - may create tidal bore which produces wave that can transport sediment

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69
Q

2B.5B

Depositon

A

occurs when waves no longer have energy to transport its material

70
Q

Why could waves lose energy 2B.5B

A

wind is dropping, removing an energy source
resistance by obstruction - groyne or headland
dissipation of energy through refraction
Friction from extended transport across shallow angled nearshore an foreshore zone

71
Q

Two ways deposition occurs 2B.5B

A

gravity settling when energy transporting water becomes to low to move sediment. Large sediment is deposited first followed by smaller
Pebbles -> Sand -> silt

Flocculation is important for small particles - clay, so small that they will suspend in water = clay particles clump together through chemical attrition and become large enough to sink

72
Q

how are beaches produced 2B.5B

A

material deposited by constructive waves - swash carries material up beach but backwash only has enough energy to transport material back down = remainder deposited

73
Q

What are bay-head beaches 2B.5B

A

curved beaches found at the back of bay

74
Q

where are bay head beaches common 2B.5B

A

swash aligned coastlines, wave refraction disperses wave energy around bay perimeter

75
Q

how are bay head beaches formed 2B.5B

A

waves break at 90 degrees to shoreline, move sediment into bay and beach forms
wave refraction erosion is concentrated at headlands and bay is an area of deposition

76
Q

what are spits 2B.5B

A

linear ridges of sand or shingle beach, connected to land at one end

77
Q

how do spits form 2B.5B

A

drift aligned coastlines, coastlines changes direction by more than 30 degrees. bay or river mouth

78
Q

how are the lengths of spits determined 2B.5B

A

existence of secondary currents causing erosion, either the flow of river or wave action which limits length

79
Q

Process of Spits 2B.5B

A

energy from longshore drift is dispersed, wave refracts and currents spreads leading to deposition on sea bed.
Sediment is deposited txobreak surface extending the each into the sea as spit

process continues until equilibrium is reached at the distal end of the spit, between deposition and erosion by waves or the existing river currents

80
Q

Hooked and Recurved spits 2B.5B

A

end of the spit is curved landwards into a bay or inlet

Hook or a recurve may form at the end of the spit

81
Q

Why do recurve spits happen 2B.5B

A

Wave refraction round the distal end transports and deposits sediment for a short distance in the landward direction

Wind and wave front are an opposing angle to the prevailing wind = short periods of longshore driftrs in landward direction

strong tidal current

82
Q

Double spits 2B.5B

A

twon spits extend out in opposite directions from both sides of the bay towards the middle

83
Q

how do double spits form 2B.5B

A

Longshore drift is operating in different directions on opposite bays

rising sea levels drive ridges of material onshore from the offshore zone

Barrier beach driven across a bay forms a bar - strong existing river current may breach the bar and form a double spit

84
Q

Poole Harbour 2B.5B

A

main longshore drift is SW - NE driven round Studland Bay by prevailing wind producing spit from the south,
HoweverWave refraction produces wave fronts from NW-SW along coastline towards north spit of Poole = north spit

85
Q

Breakpoint Bars (Offshore Bars) 2B.5B

A

Ridges of sand or shingle running parcel to the coast in an offshore zone

86
Q

how do breakpoint bars form 2B.5B

A

sediment eroded by destructive waves and carried seawards by backwash, sediment deposited at boundary offshore and nearshore zone, where orbit of water particles cases to reach seabed

87
Q

what tide can expose breakpoint bars 2B.5B

A

Neap Tide

88
Q

what are breakpoint bars used for 2B.5B

A

construct wind farms - Scroby Sands Norfolk

Source of sand for beach nourishment

Shingle dredging for construction material

89
Q

Bars 2B.5B

A

linear ridges of sand extending across a bay connected to land on both sides, traps body of seawater behind it forming. a lagoon

90
Q

two ways bays form 2B.5B

A

rising sea level = constructive waves to drive sediment onshore to coastlines (9KM Barrier beach across Start Bay in Devon - Slapton Ley lagoon behind it

Drift aligned coastlines, Longshore drift extends two spit across the entire with of the bay

91
Q

Tombolos 2B.5B

A

linear ridges of sand and shingle connecting offshore island to the coastlines of the mainland

92
Q

ways tombolos form 2B.5B

A

drift aligned coastlines, Longshore drift builds spit out from land until it contacts with offshore island

Wave refraction around both sides of the island on swash aligned coast

93
Q

examples of tombolos 2B.5B

A

St Ninain on Shetland Islands

Tombolo connecting Portland Oil to Dorset

94
Q

Cupsate Forelands 2B.5B

A

low lying traingular shaped headlands extending our from shoreline, formed from deposited sediment

95
Q

how do cupstate forelands form 2B.5B

A

Longshore drift currents from opposing directions converge at the boundary of two sediment cells

Sediment is deposited out into the sea by both currents creating triangular shaped area of deposited material

96
Q

example of cuspate foreland 2B.5B

A

Dungeness in Kent, extends 11km south east, where main west east longshore drift meets north south longshore currents produced by swell waves travelling down North Sea into English channel

97
Q

why are depositional landforms unstable 2B.5B

A

made of unconsolidated material

dynamic as they loose material transported by waves, tides, currents and wind

98
Q

why can plants stables unconsolidated material 2B.5B

A

roots hold sediment together

leaves/stems slow water and wind flow reducing erosion and encouraging further deposition

99
Q

what is plant succession 2B.5B

A

binds the loose sediment together and encourages further deposition

100
Q

factors of swash aligned coastline 2B.5B

A
  • directly faces prevailing wind
  • wave fronts approach it aligned parallel to coast
  • swash aligned beaches exhibit well defined berms
101
Q

drift aligned coastline factors 2B.5B

A

aligned at an angle to the prevailing wind
- wave fronts approach coast at angle = transport from Longshore drift
Exhibit sorting sediment with smaller, rounded sediment due to more frequent movement leads to greater rounding attriton

102
Q

drift aligned beaches 2B.5B

A

part of sediment cell
they’re dynamic as material moved in constant motion due to Longshore drift
- linear beaches along drift aligned coastline
- need consent input of sediment from river mouth or coastal erosion

103
Q

2B.5C

Sediment Cell explanation

A

concept (sources, transfers and sinks) is important in understanding the coast as a system with both positive and negative feedback, example of dynamic equilibrium

104
Q

what is a sediment cell

A

(littoral cell) linked system of sources, transfers and sinks of sediment along a section of coastline

105
Q

Example of sediment cell

A

Flanbourough Head - source Region
Holdernes Coast - transfer zone
Spurn Head - sink region

106
Q

how does a sediment operate

A

closed system with no inputs or outputs sediment from the cell, system contains inputs and transfers and outputs

107
Q

what are inputs

A

sources are places where sediment is generated, cliffs or eroding sand dunes. some sources are offshore bars and river systems are an important source if sediment for the coast

108
Q

examples of sediment inputs

A 
cliff erosion
onshore currents
river transport
wind blown 
subaerial proceses
marine organisms
109
Q

what are transfers

A

places where sediment is moving alongshore through Longshore drift and offshore currents (drift aligned) beaches and parts of dunes and salt marshes perform this function

110
Q

examples of sediment transfers

A 
longshore drift
swash
backwash
tidal currents
sea/ocean currents
wind (onshore, offshore,along shore)
111
Q

outputs

A

sinks are location where the dominant process is deposition and depositional landforms are created including spits and offshore bars

112
Q

outputs/sinks examples

A

backshore deposiitonal landforms - Sand Dunes
Foreshore depositional landforms - Beaches
Nearshore Deposiitonal Landforms - Bars
Offshore Depositional Landforms - Barrier Island

113
Q

Why are sediment cells dynamic

A

sediment is constantly generated in source region transported through the transfer regions and deposited in the sink regions

114
Q

how is dynamic equilibrium reached

A

inputs of sediment from the source region is balanced by the amount deposited in sinks

115
Q

dynamic equilibrium and changing

A

climate change creating more frequent storm or erosion of the cliff line to a more resistant rock type
System equilibrium may be interrupted (during storm event) tend to return to balance on average over time due to negative feedback

Seasonal Change - storms strong wind during winter) change dynamic equilibrium

116
Q

how does coastal management reduce sediment supply

A

sea walls preventing cliff erosion

management in transport may reduce or halt sediment supply eg gryones trapping sediment to encourage beach out building

117
Q

What is negative feedback

A

when the change produced creates effects that operate to reduce or work against the original change

118
Q

Examples of negative feedback

A

when erosion leads to blockfall mass movement. Collapsed debris act as a barrier protecting the cliff base, slowing or preventing erosion for a period of time

Major erosion of sand dunes could lead to excessive deposition offshore, creating an offshore bar = reduces energy = dunes time to recover

119
Q

What is positive feedback

A

changed produces an effect that operates to increase the original change

120
Q

example of positive feedback

A

wind erosion of a dune section high velocity storms may removing stabilising vegetation = further wind erosion now occurs later low velocity wind conditions = depletion dune sand increase

121
Q

2B.6A

what is weathering

A

breakdown of rock on the earths surface

122
Q

Weathering Infomation

A

Weathering and mass movement are subaerial processes

Weathering attacks the back shore and foreshore parts of the littoral zone

Weathering creates rock fragments that form sediment

Most active in the source zone of the sediment cell

123
Q

What is Mechanical weathering

A

application of force to physically fragment rock into smaller pieces called clasts. Break downs rock by exertion of physical force = no chemical change

124
Q

Examples of Mechanical Weathering

A

Freeze Thaw
Wetting and Drying
Salt Crystal Growth

125
Q

Process of Freeze Thaw

A

water seeps into cracks in rocks
water freezes, expands in volume, exerting tensional force that widens rock
thawing allows more water to enter crack, process repeats cracks forced open
cabble, boulder sized fragments loosened off
water in pores may freeze, prising off individual rock grains and producing sand sized fragments

rock with cracks are vulnerable to it. high on cliffs away from sea spray
freezing uncommon In uk coast

126
Q

Process of Salt Crystal Growth

A

common on coast as sea is salty
breaking force less than freeze thaw
fractured rocks are vulnerable to it
effect is greater in hot and dry climate, promoting evaportation of salt crystal
attacks foreshore zone and back shore zone that’s reached by destructive wave spray

127
Q

Process of Wetting and Drying

A

Rock containing clay mineral such as clay and shales
High tide minerals on the roc surface are soaked with sea water and expand in volume
low tie minerals dry and shrink
repeated cycles expansion and contraction eventually cause the rock to fragment and crumble

128
Q

What is chemical weathering

A

chemical reactions attack individual minerals in the rock breaking bonds and producing new chemical compounds

129
Q

Examples of Chemical Weathering

A

Carbonation
Hydrolysis
Oxidation

130
Q

Process of Carbonation

A

Attacks calcium carbonate in limestone, other carbonate rocks and sedimentary rocks with calcite sediment

Rainwater mixed with carbon dioxide from the air to form weak carbonic acid

Acidic rain mixed with calcium carbonate to form soluble calcium bicarbonate solution

Rock disappears as new minerals dissolve into solution

Sediment left from limestone is clay particles that had formed impurities in original rock

Calcite sediment is weathered previously cemented clasts are released to form sediment

131
Q

Process of Hydrolysis

A

Breakdown of minerals to form new clay minerals, plus materials in solution due to effect of water and dissolved carbon dioxide

132
Q

what rocks are vulnerable to hydrolysis

A

igneous and metamorphic rocks as their contain feldspar and silicate minerals

133
Q

Oxidation Process

A

addition of oxygen to minerals in iron compounds produces iron oxide and increases volume contributing to mechanical breakdown

134
Q

what rocks are vulnerable to oxidation

A

sandsone slitstones and shales

135
Q

when is oxidation effectivee

A

seawater or water with impurities than pure water

136
Q

What is Biological Weathring

A

break down of rock in situ by living or once living organisms, often speeds up mechanical or chemical weathering through actions of plants bacteria or animals

137
Q

Examples of Biological Weathering

A

Treet Rot Weathering
Rock Boring
Seaweed Acid

138
Q

What is seaweed acid

A

kelp contains pockets of sulphuric acid
cell breaks sulphuric acid arracks rock minerals like calcium carbonate leading to chemical reaction similar to carbonation

139
Q

Process of Rock Boring

A

Piddocks drill depression into soft rocks by rotating their shell equipped with sharp edges
Piddocks live in circular depressions, filter feeding whilst protected from high energy waves
Attack soft rock like clay and shales, vulnerable rocks ar sedimentary rocks = limestones.

140
Q

Where does Tree Root weathering occur

A

back shore zone away from reach of spray from destructive waves

141
Q

Process of Tree Root weathering

A

seeds fall into rock cracks, Evan germinate, nourished from rainwater
plant grows roots expand = rock widneing
tree roots exert sufficient tensional force to widen rocks
fragments break away as cobble or boulder sized sediment

142
Q

How does weathering increase rate of recession

A

weakens rock making them vulnerable to mass movement and cliff retreat

143
Q

Weathering and the climate

A

rates of weathering are slow

hot, wet, climate, igneous rocks weathers at 1-2mm every 1000 years

hot wet climate encourages chemical and biological weathering
carbonation increases in winter as calcium bicarbonate is more soluble in cold conditions

144
Q

when are rocks eroded more rapidly? With example

A

in the foreshore zone between high and low tide
by marine erosion hydraulic action
Vulernable wave cutch notch forms and deepens more rapidly in weathered rocks, leading to faster recession and undercutting and mass movement collapse

145
Q

2B.B6

What is mass movement

A

downslope movement of rock and soil under force of gravity

146
Q

when does mass movement occur

A

downslope gravitational force exceeds the resisting forces of friction and internal rock cohesion

147
Q

Type of mass movement depends upon lithology

A 
unconsolidated material (boulder clay) - slumping
consolidated rock (limestone, granite) - sliding
148
Q

How is rockfall initatied - weathering

A

mechanical weathering
freeze thaw
salt crystal growth

149
Q

how is rockfall intimated

erosion

A

marine erosion
hydraulic action
abrasion
undercutting cliff creating wave cut notch = notch removed supporting material that supplied resistive force holding up rock

150
Q

Cliff prone to block fall have..

A

steep, near vertical drip of stata
often also in earthquake prone area
geological structure with many joints faults or bedding planes

151
Q

how quick is blockfall

A

rapid, few seconds

152
Q

BlockFall case study

A

April 2013
Large Blockfall in St Oswald Bay on South Dorset Coast

80m section of Chalk detached overnight

153
Q

what is rotational slumping

A

involves rock failure and movement along a curved rock plane

154
Q

where does rotational slumping occur

A

weak rocks
unconsolidated material - boulder clay sands and gravels
permeable rock strata overlie impermeable beds

155
Q

how is slumping faciliatated

A

presence of water = adds weight = increasing gradational force as well s lubricating it reducing friction

156
Q

Example of rotational slumping

A

Christchurch Bay

Unconsolidated sand overlie clay

157
Q

Slumping process

A

funnelling water into permeable sand in dry weather sand cracks
water pressure form lines of weakness in the sand

water goes into lower sand as unable to percolate in impermale clay, water pressure lubrcating the bedding plane which makes sand move

weight of water adds to downslope force = wave erosion created notch at the cliff foot removing support

158
Q

how is landslide made

A

marine erosion of a cliff foot undercutting blocks weakened by jointing

159
Q

how is landslides encouraged

A

rainstorms = lubricating the slip plane reducing resistance

160
Q

when do landslides occur

A

consolidated rocks with joints or bedding planes sloping seawards

161
Q

ways to classify mass movement

A

speed of movement
water content
type of sediment

162
Q

when do flows occur

A

uncolsidated rocks fine grained sediment (clays) mixi with large volumes of water

163
Q

where are flows common

A

weak rocks such a clay or unconsolidated rocks - become saturated low their cohesion and flow downslope

164
Q

how is saturation contributed to = flow

A

heavy rainfall with high waves and tides

165
Q

types of flows

A

earthflows, mud flows

earth flows more viscous than mudflows and contain larger sediment

166
Q

earth flows and environment

A

cold environment - solifluction occur in unfrozen layer between permafrost and tundra vegetation turf

167
Q

how can mass movement be classified

A

type of sediment
water content
speed of movement

168
Q

what distinctive landforms can be created by mass movement

A

rotational scars, talus scree slopes, terraced cliff profiles

169
Q

what is a rotational scar

A

fresh, curved, unweathered and unvegetated rock surface on the cliff face

170
Q

what does a detached slope section form

A

beach or terraced cliff profile

171
Q

what can undercutting of cliffs result in, and how are they undeructted

A

wave cut notches.

this can lead to large falls of talus scree slopes are their base

172
Q

how is a talus scree slope formed

A

angular blockfall debris accumulates at the cliff foot

Physical Geography (5 decks)

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