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physical geo > coastal systems and landscapes > Flashcards

coastal systems and landscapes Flashcards

1
Q

what type of system is the coast?

A

closed

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2
Q

what are sediment cells often bordered by?

A

prominent headlands

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3
Q

what is a sediment cell?

A

largely self contained stretch of coastline

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4
Q

the flows of sediment act in which ways?

A

dynamic equilibrium

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5
Q

what is dynamic equilibrium?

A

maintenance of a balance in a natural system, in constant state change

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6
Q

how does the system keep this balance of equilibrium?

A

inputs and outputs constantly changing to counteract any changes

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7
Q

how can dynamic equilibrium be affected in the long term and short term

A

LT- human intervention

ST- natural variations

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8
Q

what are the smaller areas called within each sediment cells?

A

sub cells

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9
Q

the sub cells are often used for planning what?

A

coastal management projects

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10
Q

what are feedback loops?

A

mechanisms which enhance changes within a system

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11
Q

what is positive feedback? simple

A

taking it away from dynamic equilibrium

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12
Q

what is negative feedback?simple

A

taking system back towards equilibrium

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13
Q

give an example of how a negative feedback loop would work for a storm eroding beach?

A
  • destructive waves loose energy, deposit excess sediment as an offshore bar
  • bar dissipated wave energy protect beach
  • bar eroded instead of beach
  • once bar has gone back to DE
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14
Q

give an example of how positive feedback would work for people trampling on sand dunes?

A
  • people trample of sand dunes destroys veg increases erosion
  • sand dunes completely eroded leaving beach open to erosion taking away from OG state
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15
Q

name 6 sediment sources

A
  • rivers
  • cliff erosion
  • wind
  • glaciers
  • offshore
  • longshore drift
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16
Q

what is most of sediment in the coastal zone a result of?

A

an input from rivers

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17
Q

where is the sediment sometimes deposited? then where does the sediment get transported to?

A

estuaries which are brackish (salty) areas where rivers flow into sea, then sediments flows through coastal systems

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18
Q

erosion is prominent in areas with what type of cliff?

A

unconsolidated (uncompacted and therefore unstable)

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19
Q

how is cliff erosion a sediment source?

A

some areas coasts can retreat up to 10m per year= sed input

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20
Q

how is wind a sediment source?

A

it transports sediment like sand (sand dunes)

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21
Q

how are glaciers a sediment source?

when does this occur?

A

glaciers flow directly into ocean depositing sediment that was stored in ice.
occurs when glaciers calve, ice breaks of glacier

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22
Q

how does offshore become a sediment source?

A

waves erode offshore sediment sink (offshore bars). sed transported to beach.
OR storm surges

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23
Q

how is longshore drift a sediment source?

A

sediment moved along beach, due to prevailing wind

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24
Q

what are sediment budgets?

A

they use data of inputs, outputs, stores and transfers to assess the gains and losses of a sediment within a sediment cell

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25
Q

if sediment cells are supposed to be in dynamic equilibrium why is a sediment budget needed?

A

because human action and natural variation can disrupt the state of equilibrium

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26
Q

what is the littoral zone?

A

the area of land between the cliffs or dunes on the coast and the offshore area that is beyond the influence of waves

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27
Q

why is the littoral zone constantly changing?

short term and long term

A

short term- tides and storm surges

long term- changes in sea level and human intervention

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28
Q

what is the shore/shoreline?

A

boundary between sea and land

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29
Q

what is offshore?

A
  • area beyond the influence of wave
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30
Q

what is onshore?

A

area of land not covered by the sea but close to it

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31
Q

what is the primary source of energy for all natural systems?

A

the sun

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32
Q

what is the main energy source at the coast?

A

wind or less frequently tectonic activity

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33
Q

how are waves formed?

A

-wind moves across surface of the water causing frictional drag creates small ripples, waves circular orbital motion of water particles
- shallow seabed orbit becomes elliptical
= horizontal movement of waves
-wave height ^ length/ velocity decreases

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34
Q

how are waves formed?

A

-wind moves across surface of the water causing frictional drag creates small ripples, waves circular orbital motion of water particles
- shallow seabed orbit becomes elliptical
= horizontal movement of waves
-wave height ^ length/ velocity decreases
-waves break, surges up beach

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35
Q

what is swash and backwash?

A

water up beach

water down to beach

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36
Q

Name three factors that affect wave energy?

A
  • strength of wind (stronger wind=stronger waves)
  • duration of wind (wind is active for longer periods of time energy waves build up and increase)
  • size of fetch (distance over which wind blows, larger it is more powerful waves will be)
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37
Q

what do constructive waves tend to do with material? what do they create?

A

deposit, creates depositional landforms, increases size of beach

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38
Q

what do destructive waves tend to do?

A

remove depositional landforms through erosion, decrease size of beach.

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39
Q

the difference in formation in constructive and destructive waves?

A

con- formed by weather systems in open systems

des- stronger winds closer to coast

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40
Q

different in wave length for constructive and destructive waves?

A

con- long WL

des-short WL

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41
Q

Frequency of con and des waves?

A

6-9 per min

11-16 per min

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42
Q

wave characteristics of con and des waves?

A

low waves, surge up beach

high waves, plunge onto beach

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43
Q

swash characteristics of con and des waves?

A

strong swash/weak backwash

weak swash/strong backwash

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44
Q

what types of beaches do con and des waves fall on?

A

occurs on gently sloped beaches

occurs on steep beaches

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45
Q

what waves dominate in summer and what waves in winter

A

summer- constructive

winter- destructive

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46
Q

negative feedback of beaches and waves

A

deposition
steeper beach profile
steep beaches favour destructive waves, beach is eroded, reducing beach profile leading to constructive waves.

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47
Q

What is a key source of energy in coastal environments responsible for tides?

A

gravity

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48
Q

when do tides occur ?

A

when the gravitational pull of the sun or moon changes the water levels of the seas and oceans

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49
Q

what is the difference in height between the tides known as?

A

tidal range

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50
Q

when do the highest high tide and the lowest low tide occur ?

A

when the sun and moon are in alignment

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51
Q

what is another name for the lowest low tide? what type of tidal range does this create?

A

SPRING TIDE

largest possible tidal ranges

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52
Q

when do the lowest high tide and the highest low tide occur?

A

sun and moon are perpendicular to each other , both of the gravitational forces act against each other so overall pull is minimised

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53
Q

what is another name for this? what type of tide does this create?

A

neap tide creates smallest possible tidal range

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54
Q

what are rip currents? how do they form?

A

powerful underwater currents occurring close to the shoreline
backwash is forced under the surface forming an underwater current.

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55
Q

high energy coastlines are assosiated with what waves?

A

powerful waves (destructive), areas of large fetch

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56
Q

what type of landforms are assosiated with high energy coatslines?

A

rocky headlands and landforms

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57
Q

how does erosion effect these high energy coastlines?

A

erodes quickly as the rate of erosion exceeds the rate of depositon

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58
Q

what waves are associated with low energy coastlines?

A

less powerful waves (constructive)

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59
Q

what type of landforms are associated in these areas of high energy??

A

landforms of deposition (sandy beaches)

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60
Q

effect of erosion?

A

little as the rate of deposition exceeds rates of erosion

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61
Q

what is wave refraction?

A

the process by which waves turn and loose energy around a headland on uneven coastlines

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62
Q

where is the wave energy focused?

A

on the headlands creating erosive features in these areas

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63
Q

where is the energy focused?

A

dissipated in bays leading to formation of features associated with lower energy environments (beaches)

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64
Q

negative feedback of erosion

due to different rock strengths what odes erosion lead to?

A

the formation of headlands where resistant rock exists and bays where unconsolidated rocks and clays are dominant

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65
Q

what does this then increase?

A

the forces of erosion on the headlands and reduced erosion in the bays as wave refraction dissipates wave energy and a beach protects coast behind

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66
Q

what is then worn away?

A

headlands= increases erosion

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67
Q

what what would this then lead to as a result of negative feedback?

A

dynamic equilibrium if conditions stayed constant

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68
Q

name 6 types of erosion (C.A.A.H.C.W)

A 
corrasion 
abrasion 
attrition 
hydraulic action 
corrosion wave quarrying
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69
Q

process of corrasion?

A

sand and pebbles picked up by the sea from an offshore sediment sink and hurled against cliff at high tide= erosion

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70
Q

process of abrasion?

A

sediment is moved along the shoreline, warn down overtime

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71
Q

process of attrition?

A

wave action cause rocks and pebbles to hit against each other, wearing each other down and so becoming round and smaller. has little effect on coastline itself

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72
Q

process of hydraulic action?

A

wave crash against rock or cliff face, air id forced into cracks, joints and faults within rock. high pressure= cracks force apart and widen when wave retreats air expands. bubbles in the water in rock may implode under high pressure creating tiny jets of water= erode rock

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73
Q

process of corrosion

A

mildly acidic seawater cause alkaline rock such as limestone to be eroded. similar to carbonation weathering

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74
Q

what is wave quarrying?

A

when breaking waves that hit the cliff face exert a pressure up to 30 tonnes per m^2. similar to HA but acts with more pressure to directly pul away rocks from a cliff face or remove smaller weathered fragments. force of breaking wave hammers rock surface, weakens it leaving it open to attack from HA and abrasion.

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75
Q

name 4 main factors that affect coastal erosion?

A
  • waves
  • beaches
  • rock type
  • subaerial processes
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76
Q

how do waves affect coastal erosion?

A

erosion occurs mostly in the winter when the waves are more destructive and powerful due to frequent storms

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77
Q

how do beaches affect coastal erosion?

A

if a becah is infrount of a cliff then this will absorb most of the wave energy= reduce erosion rates. if there is coastal management being used there like groins it can increase the rate of erosion elsewhere down the beach.

78
Q

how does the rock type affect the rate of erosion?

A

igneous rocks are made up of interlocking crystals making them more resistant to eroison

79
Q

how do subaerial processes affect erosion?

A

weathering and mass movement like landslides weakens cliffs. rock fragments= increase in corrasion/abrasion

80
Q

IGNEOUS rock

  • example
  • rate of erosion
  • structure
A

-granite
-very slow (<0.1)
interlocking crystals

81
Q

METAMORPHIC rock

  • example
  • rate of erosion
  • structure
A
  • slate
  • slow (0.1-0.3 cm yr)
  • crystal orientated in same direction
82
Q

SEDIMENTARY rock

  • example
  • rate of erosion
  • structure
A
  • limestone
  • very fast (0.5-10cm yr)
  • lots of faults making them weak
83
Q

what is coastal transportation responsible for?

A

transferring sediment within a sediment cell and between other sediment cells

84
Q

what are the main four processes of transportation?

A
  • traction (large heavy sediment rolls along the sea bed pushed by currents)
  • Saltation (smaller sediment bounces along sea bed, pushed by currents)
  • suspension (small sediment is carried within flow of water)
  • solution (dissolved material is carried within the water, potentially in chemical form.)
85
Q

longshore drift, how does it work?

A
  • waves hit beach at an angle determined by direction of Prevailing wind.
  • waves push sediment in this direction and up beach in swash
  • due to gravity wave carries sediment back down beach in backwash
  • moves sediment
86
Q

when does deposition occur?

A

sediment becomes too heavy for the water to carry or if the wave looses energy

87
Q

what are the two types of deposition?

A

gravity setting

flocculation

88
Q

what is gravity setting?

A

waters velocity decreases so begins to be deposited

89
Q

what is flocculation?

A

in salt and tidal marshes. Clay particles clump together due to chemical attraction and then sink due to high density.

90
Q

what is weathering?

A

breakdown of rocks overs time, leading to the transfer of material into the littoral zone, becomes an input to sediment cells

91
Q

positive feedback of weathering?

A

rate removal of the weathered rock form the base of then cliff is higher than the rate of weathering, promote further weathering as increases area of exposed rock

92
Q

negative feedback of weathering?

A

if removal of weatherd rock from base of cliff is slower than the rate of weathering= build-up of debris at the base of the cliff, reducing the exposed cliff area= reduces rate of weathering

93
Q

what is mechanical weathering?

A

breakdown of rocks due to exertion of physical forces without any chemical changes

94
Q

name three types of mechanical weathering?

A
  • freeze thaw
  • salt crystallization
  • wetting and drying
95
Q

explain freeze thaw?

A

water enters cracks in rocks, water freezes overnight in winter. freezes water expands by 10%= cracks in rocks. weakens cliff

96
Q

explain salt crystallisation?

A

seawater evaporates, salt left behind. salt cryst grow= exerting pressure= cracks widen. salt can corrode ferrous rock due to chem reaction

97
Q

What is wetting and drying?

A

rock (clay)expand when wet, contract when dry. cycle= rocks/ cliffs to break up

98
Q

what is chemical weathering?

A

breakdown of rocks through chem reactions

99
Q

name 3 types of chem weathering?

A

carbonation
oxidation
solution

100
Q

what is acrbonation?

A

rainwater absorbs co2= weak carbonic acid, reacts with calcium carbonate in rocks= calcium bicarbonate (easily dissolved) .acid rain reacts with limestone to form calcium bicarbonate

101
Q

what is oxidation?

A

when minerals become exposed to air through cracks and fissures, mineral becomes oxidized= increases volume rocks crumble.

102
Q

what is solution?

A

when rock minerals such as rock salt are dissolved

103
Q

what is biological weathering?

A

the breakdown of rocks by organic activity

104
Q

name 3/5 types of biological weathering?

A
  • rock boring
  • birds
  • decaying vege
105
Q

explain rock boring ?

A

many species of clams secrete chemicals that dissolve rocks and piddocks may burrow into the rock face

106
Q

explain how birds cause weathering?

A

some birds such as PUFFINS dig burrows into cliffs weakening them

107
Q

explain decaying vegetation?

A

water that flows through decaying veg and then over coastal areas, will be acidic= chemical weathering

108
Q

what is mass movement?

A

movement of material down a slope under the influence of gravity

109
Q

Mass movement can be categorized into 4 main areas what are they?

A
  • creeps
  • flows
  • slides
  • falls
110
Q

the type of mass movement can be dependent on what (name 4)

A
  • cliff/slope angle
  • rock type
  • vegetation
  • rock structure
111
Q

what are the 6 types of mass movement?

A
  • soil creep
  • solifluction
  • mudflows
  • rock fall
  • landslide
  • landslip/slump
  • run off
112
Q

what is soil creep?

A

movement o soil particles down a hill.. leads to formation of shallow terraces

113
Q

what is solifluction?

A

occurs mainly in tundra areas where land is frozen (periglacial enviro) as top layers thaw during summer the surface layers flow over the frozen layers. forms solifluction lobes.

114
Q

what are mud flows?

A

increase in water content of soil can reduce friction, leading mud to flow over underlaying bedrock. water can get trapped in rock increasing pore water pressure= weakens slope

115
Q

when does rock fall happen? what is teh cause mostly?

A

occurs when exposed to mechanical weathering. earthquakes, leads to scree

116
Q

what is a landslide ?

A

heavy rainfall leads to water between joints and bedding planes in cliffs, reduce friction and lead to landslide

117
Q

what is land slip?

A

slope is curved, water pressure leads to the land to collapse under its own weight. create a scarred appearance to the cliff face

118
Q

what is run off?

A

water in the form of overland flow may erode the cliff face and coastal area or pick up sediment, that then enters littoral zone, transported in water via suspension

119
Q

what can influence the prominence of weathering?

A

temperature and climate

120
Q

sequence on pinnacle headland

how are small caves created?

A

faults in headlands eroded by hydraulic action and abrasion= small caves

121
Q

how are blow holes created?

A

overlying rock in cave may collapse, forming blowhole.

122
Q

what happens to create a wider cave?

A

marine erosion widens faults in the base of headland= cave

123
Q

the cave will widen more and create what, due to what?

A

-marine erosion and sub-aerial processes, creating an arch

124
Q

the arch continues to widen and what is created and how?

A

arch widens and is unable to support itself, falling under its own weight through mass movement= stack

125
Q

what happens to the stack sue to marine erosion?

A

becomes a stump

126
Q

what is finally left?

A

a wave-cut platform

127
Q

where are steep cliffs most commonly found?

A

where rock is strong and fairly resistant to erosion

128
Q

what rock is most resistant to erosion

A

sedimentary rocks that have vertical strata, create steep cliffs

129
Q

where are gentle cliffs found?

A

areas with weaker rocks, less resisitant to erison

130
Q

rate of retreat is dependant on what?

A

marine factors (fetch, beach, wave and energy) and terrestial factors (subariel processes, geology and rock strengths)

131
Q

what type of cliffs are most likely to retreat?

A

those made of unconsolidated rock

132
Q

wave cut notch and platform? sequence?

A

when cliffs erode concentrated around high tide line.
process of hydraulic action and corrasion create a wave cute notch
notch= deeper cliff becomes unstable falls under weight
leaves behind a platform of unaffected cliff beneath a wave-cut notch

133
Q

negative feedback of a wave-cut notch?

A

length of wave cut platform is limited as waves cannot reach cliff reducing erosion. act of erosion creating the wave-cut platform has acted to directly decrease the rate of erosion in future

134
Q

what type of landform is a beach?

A

depositional

135
Q

when are beaches created?

A

when sediment is deposited near the coastline when waves loose their energy.

136
Q

when does beach accretion occur?

A

when the beach is being built up by constructive waves (summer)

137
Q

when does beach excavation occur?

A

in winter when destructive waves remove sediment from the beach

138
Q

the effectiveness of transportation is dependant on what? and leads to different beaches.

A

angle of prevailing wind

139
Q

what are swash aligned beaches

?

A

-wave approaches perpendicular to coast so there’s limited longshore drift, wave refraction reduces speed of high energy waves= shingle beach

140
Q

what are drift aligned beaches?

A

waves approach at a significant angle, longshore drift= sediment long down beach= spit. generally larger sediment at start of beach and weathered sediment moves further down beach.

141
Q

what are berms?

A

ridges where the high tide line is at different times of the year

142
Q

what are cusps?

A

small curved dips in the beach where swash comes in

143
Q

what are Runnells?

A

smaller ridges often found in smooth wet sand, caused by tides

144
Q

what is a spit?

A

long narrow strip of land which is formed when longshore drift causes beach to extend out to sea.

145
Q

what is a spit usually due to?

A

change in direction of the coastline

146
Q

what can sediment projection create?

A

salt marsh due to the sheltered, saline enviro, allowing deposition of finer sediments

147
Q

what does the length of the spit depend on ?

A

changing currents or rivers, which will prevent sediment from being deposited

148
Q

can a spit extend across an estuary?

A

NO

149
Q

what is a compound spit?

A

spit with multiple recurved tips

150
Q

what is a double spit? what can it lead to?

A

were spits from opposite sides of a bay reach out towards each other, barrier beach

151
Q

what is a barrier beach?

A

when a beach or spit extends across a bay to join two headlands this traps water behind it leading to formation of a lagoon.

152
Q

what else has caused a barrier beach to form?

A

rising sea levels after the last glacial period.

153
Q

what are barrier beaches known as when they become detached from the mainland?

A

barrier island

154
Q

what area are they most common in?

A

low tidal ranges

155
Q

what are tombolo’s?

A

a bar or beach that connects the mainland to an offshore island

156
Q

what are tombolo’s formed due to?

A

formed due to wave refraction off the coastal island wave velocity, leading to deposition of sediment

157
Q

what are offshore bars?

A

an offshore region where sand is deposited, as waves don’t have enough energy to carry sediment to shore

158
Q

when are they formed?

A

when waves break early, instantly depositing its sediment as a loose-sediment offshore bar.

159
Q

waves may pick up sediment from an offshore bar which then provides wha?

A

sediment input in to the coastal zone

160
Q

how else can offshore bars be formed?

A

result of backwash from destructive waves removing sediment from a beach

161
Q

what is a vegetation succession?

A

a plant community that changes over time.

162
Q

on coasts where there are is a supply of sediment and deposition occurs what plants grow?

A

pioneer plants

163
Q

what is the first stage of sand dune succession?

A

embryo dunes are first colonized by pioneer plants, which die and release nutrients into the sand, increasing amount of veg able to grow

164
Q

stage two (enviro conditions)?

A

embryo dunes and pioneer plants alter enviro conditions from harsh to salty, to an eviro in which other plants can survive

165
Q

stage 3 (new species)?

A

new species of plants can now colonise the area, change enviro progressively

166
Q

why is marram grass a very good example of a pioneer plant?

A
  • tough/flexible
  • adapted to reduce water loss through transpiration
  • roots 3m deep tolerate 60c temp
167
Q

what are the 5 stages of salt marsh succession?

A 
1- algal stage 
2- pioneer stage
3- establishment stage 
4- stabilization 
5- climax vege
168
Q

what happens in the algal stage?

A

gut weed and blue green algae establish as they can grow on bare mud, roots bind together

169
Q

what happens in the pioneer stage?

A

cord grass grow, roots begin to stabilise the mud allowing the estuarine to grow

170
Q

what happens in the establishment stage?

A

salt marsh grass grow , creating a carpet of vegetation and height increases

171
Q

what happens in stabilisation?

A

sea thrift, grow and so slat rarely ever gets submerged beneath the marsh

172
Q

what happens in climax vegetation stage?

A

rush, sedge and red fescue grass grow since the salt marsh is only submerged once or twice a year

173
Q

how does vegetation help stabilise coastal sediment?

A
  • roots bind soil=reduce erosion
  • when submerged, plants provide a protective layer for ground
  • plants reduce wind speed at surface
174
Q

when do sand dunes occur?

A

prevailing winds blow sediment to the back of the beach

175
Q

what does the formation of dunes require?

A

large quantities of sand and a large tidal range

176
Q

what types of wind is also required?

A

frequent and strong

177
Q

the dunes develop as a process of a vegetation succession.

-what helps bind dunes together

A

-sea rocket are resistant and able to survive in salty sand, with roots helping bind dunes together

178
Q

-what allows marram grass to grow?

A

decaying organic matter adds nutrients and humus

179
Q

larger plants colonise area, what occurs when the trees are able to colonise the area?

A

climatic climax

180
Q

name 5 different types of dunes?

A
  • embryo dunes
  • yellow dunes
  • grey dunes
  • dune slack
  • heath and woodland
181
Q

what are embryo dunes?

A

upper beach area where sand starts to accumulate around a small obstacle?

182
Q

what are yellow dunes?

A

as sand accumulates and the dunes grow, vegetation may develop on the upper and back dune surfaces, stabilises dune. tallest of dune succession

183
Q

what are grey dunes?

A

sand develops into soil with lots of nutrients, veg dies enabling more varied plant growth

184
Q

what is dune slack?

A

water table rises closer to surface, or water is trapped between hollows between dunes during storms, allowing development of moisture loving plants

185
Q

what is heath and woodland?

A

sandy soils develop as there is a greater nutrients content, allowing less brackish plant to thrive. tree will also grow with coastal woodland becoming a natural windbreak to the mainland behind

186
Q

why does deposition occur in river estuaries?

A

when the flow of water from the river meets with the incoming tides= water flow virtually cease, water can no longer carry sediment suspension

187
Q

as most of the sediment is small what does this lead to a build up of?

A

mud, builds up till it’s above see level

188
Q

deposition occurs as a result of what in salt marshes?

A

flocculation

189
Q

why is a meadow formed

A

sections of the salt marsh rise above the high tide level leading to the climatic climax of the vegetation succession when trees begin to colonise the area

190
Q

depositional landforms consist of what making them vulnerable to change?

A

unconsolidated sediment

191
Q

what happens during major storms?

A

large amounts of sediment can be eroded or transported elsewhere removing any landform from one region of the sediment cell

192
Q

what do depositional landforms rely on to balance erosion?

A

continuous supply of sediment, which may see some landforms changed as their dynamic equilibrium shifts

physical geo (17 decks)

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