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Coasts > Coasts part 1 > Flashcards

Coasts part 1 Flashcards

1
Q

define system

A

a system of interrelated objects made up of components and processes that are connected together to form a working unit or unified whole

coastal landscape systems store and transfer energy and material on time scales that can vary

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2
Q

inputs to coastal systems

A 
wave energy (kinetic) 
wind energy (kinetic)
tidal energy (kinetic)
material on slopes (GPE)
material from offshore (GPE)
energy from sun (thermal)
urban planning
coastal management/ defences
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3
Q

outputs of coastal systems

A 
beach erosion by sea
beach erosion by wind
evapouration
erosion of rock surfaces
weathering/ erosion of cliffs
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4
Q

throughputs/ stores in coastal systems

A 
beach
sandbank near shore
sand dunes
longshore drift
river sediments
tidal energy (kinetic)
build up of sand below water's surface
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5
Q

when does equilibrium occur on a beach

A

when sediment added is equal to that being taken away

inputs=outputs

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6
Q

dynamic equilibrium

A

negative feedback
system undergoes self regulationand changes in order to restore the equilibrium
occurs in a constanly changing system

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7
Q

define sediment cell

A

stretch of coastline and its nearshore area within which the movement of sediment is largely confined
generally a closed system
(england and wales)

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8
Q

what factors mean there is sometimes sediment transferred between cells

A

storm events
high tides
dominant winds

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9
Q

what divides up sediment cells

A

headlands (resistant rock)
topography
wind direction
tides

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10
Q

how many sediment cells are there

A

11

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11
Q

what are sediment budgets

A

a coastal management tool used to analyse and describe the different sediment inputs and outputs on the coasts, which is used to predict morphological (shape of coast) change in any particular coastline

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12
Q

do destructive or constructive waves have a bigger input

A

constructive

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13
Q

potential influences on coastal landscape systems of:

A
  • waves
  • winds
  • tides
  • geology
  • global ocean currents
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14
Q

how are waves generated?

A

by the friction of wind dragging across the surface of water
the higher the wind speed and longer fetch then the more energy they have and bigger they are

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15
Q

what type of energy does a wave have?

A

GPE
as a result of its position above the wave trough,

kinetic
caused by the motion of water within the wave

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16
Q

formula for the amount of energy in a wave

A

P= (HxH) x T

P- power - kw/m
H- wave height
T - time between two wave crests (period)

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17
Q

crest

A

top of the wave

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18
Q

trough

A

bottom of the wave

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19
Q

wave length

A

distance between two crests or two troughs

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20
Q

wave height

A

amplitude- distance of crest to trough

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21
Q

what happens when waves reach the shore?

A
  • the bottoms of the circulating molecules come into contact with the sea floor
  • this causes friction which slows the wave down from the bottom
  • this causes the wavelength to decrease and the waves start to bunch up
  • the top of the wave is still travelling fast and the wave begins to steepen as the base lags behind
  • when the depth is 1.3X wave length then the wave topples over, this is when the wave breaks
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22
Q

spilling waves

A

Steep waves breaking onto gently sloping beaches. Water spills gently forward as the wave breaks. As the wave approaches the shore, it slowly releases energy and the crest gradually spills forward.

Why?
•	Bottom of the ocean/beach is fairly flat
•	waves come in and slow down gently
•	steepen gently
•	and so break gently
•	top of the waves spill down the front
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23
Q

plunging waves

A

Moderately steep waves breaking onto steep beaches. The water plunges vertically downwards as the crest curls over and explodes on the trough. The air under the lip of the wave is compressed, and a crashing sound is often heard.

Why?
• When waves travel from deep water to shallow water very quickly
• and they slow down so fast start causes a motion of water that curls over and crashes down violently

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24
Q

surging waves

A

Low angle waves breaking onto steep beaches. The wave slides forward and may not actually break, as a result of the water being very deep beneath them.

Why?
• Don’t have much time to break because the transition from deep-water to shallow water is too fast
• So they end up just surging up onto the beach.
• Typically happens in may areas during high tide

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25
Q

describe backwash

A

after wave broken water moves up beach as swash driven by energy from breaking wave
speed of water slows down through friction until theres no more energy to move forward
then drawn back down beach as backwash
energy to do this comes from gravity and is always perpendicular to the coastline down the steepest slope angle

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26
Q

features of constructive waves

A 
low height
low frequency
spilling wave
strong swash
long wavelength

produce hugh and steep beach profiles- storm beaches

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27
Q

features of destructive waves

A 
high height
high frequency
plunging waves
swash less than backwash
short wavelength

form low, long length beaches forming berms

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28
Q

sources of sediment

A
  • rivers
  • wave erosion
  • longshore drift
  • aeolian processes
  • beach nourishment
  • dredging
  • constructive waves
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29
Q

sub aerial processes

A

the processes of weathering and mass movement

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30
Q

geomorphic

A

the form of the landscape and other natural features on the earth’s surface

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31
Q

mass movement

A

the movement of surface material caused by gravity eg. landslides and rockfalls

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32
Q

rip currents

A

an intermitant strong surface current flowing seaward from the shore

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33
Q

swell

A

a series of mechanical waves that propagate along the interface between water and air and so they are often referred to as surface gravity waves

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34
Q

lithology

A

the study of the general physical characteristics of rocks

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35
Q

abrasion

A

waves armed with rock particles scour the coastline as the bits of rock are rubbed together

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36
Q

attrition

A

rock particles being carried by the water collide and bang together. They progressively get worn away to be smaller and rounder t eventually make sand

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37
Q

hydraulic action

A

when waves break against a cliff face and any trapped air or water becomes compressed (squashed) at high pressure. When it recedes, the air/ water expands again to widen the crack

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38
Q

pounding

A

the mass of breaking wave exerts pressure on the rock to cause it to weaken

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39
Q

solution

A

dissolving of carbonate minerals in coastal rocks which tend to be alkaline. the pH of sea water is usually 7 or 8 so only really happens in small quantities or in scidic polluted areas

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40
Q

open system

A

freely exchanges matter and energy with its surroundings

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41
Q

closed system

A

the boundary permits the exchange of energy but not matter with the surroundings

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42
Q

isolated system

A

no matter or energy can escape or enter

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43
Q

negative feedback

A

the system’s response in the opposite direction to initial output
self regulating

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44
Q

positive feedback

A

an increase in output which leads to a further increase in output

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45
Q

example of cell and sub cell

A

cell- Flamborough Head- The Wash

subcell- Flamborough Head- Humber Estuary

46
Q

still water level

A

the surface of the water if all wave and wind action were to cease

47
Q

period

A

time required between two successive crests or troughs to pass a fixed point

48
Q

frequency

A

number of waves per second that pass a fixed point.

49
Q

velocity

A

speed with which the waves are moving a fixed point

50
Q

ocean waves behave differently depending on…

A

…the depth of water they’re formed in

51
Q

what are tides

A

the periodic variation in sea level that occur primarily because of the Moon’s and the Sun’s gravity

52
Q

How often SHOULD we get high tides?

A

12 hours and 25 minutes due to orbit of the moon

53
Q

we dont always get high tides once a day because:

A
  • varying depths of the oceans
  • continents
  • shape of coastlines
  • interaction of the surface of oceans with atmosphere
54
Q

tidal range

A

the difference in height between successive high and low tides

55
Q

when do spring tides occur?

A

when the sun earth and moon are aligned

56
Q

what happens when there is a spring tide?

A

higher than average high tides and lower than average low tides- increased tidal range

57
Q

how often do spring tides occur

A

once every 2 weeks

58
Q

when does a neap tide occur

A

when the sun and moon are perpendicular to one another

59
Q

what happens when there is a neap tide

A

the height of the high tide is lowered- tidal range reduced

60
Q

ho often do neap tides occur

A

once every two weeks

61
Q

where has the world’s highest tides

A

The Bay of Fundy- east coast of Canada

because of its distance from the continental shelf edge

62
Q

need to do about tides a bit more?

A

to do

63
Q

material is deposited when…

A

…there is a loss of energy caused by a decrease in velocity or amount of water

64
Q

when does marine deposition occur

A
  • when waves slow down after breaking
  • at top of swash when water stops moving for a brief moment
  • during backwash when water sinks into beach
  • in low energy environments sheltered from wind or waves
  • beach nourishment (human) sand lost by LSD or erosino is replaced by humans
65
Q

what does the Hjulstrom Curve show?

A

the relationship between river velocity, processes and sediment size

66
Q

when are rocks “under attack”

A

when it is exposed at the surface it is “under attack” by weathering and erosion

67
Q

two main geological factors:

A

1, lithology

2. structures

68
Q

what is lithology

A

the physical and chemical composition of the rock, which effects the ability of a rock to withstand weathering, erosion and mass movements.

69
Q

what are crystalline rocks

A

have interlocking crystals and are very strong

70
Q

examples of crystalline rocks

A

basalt, granite

71
Q

example of rock with weak bonds

A

clay

72
Q

why is clay soft

A

weak bonds between the particles that make up the rock

73
Q

example of rock with no interlocking particles

A

mudstone

74
Q

what is mudstone composed of

A

grains

75
Q

(lithology)

example of rocks that react with acid

A

limestone and chalk

76
Q

describe carbonation

A

Calcium carbonate is soluble in weak acids so is vulnerable to a type of chemical weathering called carbonation. Rain water contains carbonic acid which, over time, will dissolve limestone and chalk.

77
Q

important properties of individual rock types

A
  • joints
  • faults
  • porosity and permeability
  • beds (eg dip)
  • orientation in relation to the coastline
78
Q

joints

A

vertical cracks/zones of weakness running through rock and are common in rock like limestone. Joints increase the surface area for physical and chemical weathering and are easily enlarged by solution and freeze thaw. Joints increase the permeability of the rock (secondary permeability).

79
Q

what processes enlarge joints and the surface area

A

solution and freeze thaw

80
Q

faults

A

a result of tectonic activity to which there has been movement. They are areas of weakness and may slip again. Faults increase permeability of a rock (secondary permeability) making the rock less resistant to chemical weathering.

81
Q

what is porosity

A

the ability of a rock to hold water

82
Q

what is permeability

A

the degree to which water can pass through a rock

83
Q

what rock is very permeable and porous

A

sandstone

84
Q

why is sandstone both permeable and porous

A

the spacing between grains and the connected pore spaces

85
Q

are crystalline rocks permeable or impermeable

A

impermeable

86
Q

what does permeable mean

A

allowing liquids or gases to pass through it

87
Q

is clay permeable?

A

no, its impermeable

88
Q

what are bedding planes

A

surfaces that separate different layers of rocks. They’re originally deposited horizontally, but may be later tilted

89
Q

what type of cliff does a horizontal bed crreate

A

steep sided cliff

90
Q

when bedding surfaces dip forward, they’re likely to

A

slip due to gravity and lack of supoprt

91
Q

what is a discordant coastline?

A

alternating layers of hard and soft rock are perpendicular to the coastline

92
Q

what are the features of a discordant coastline?

A

bays and headlands

93
Q

what is a concordant coastline?

A

rocks are parallel to the coastline. Hard rock shields the soft rock from erosion

94
Q

features of a concordant coastline?

A

usually a straight coastline

sometimes sea breaks through and forms a cove (a small sheltered bay)

95
Q

what are currents

A

currents reflect the movement/flow of water

96
Q

what effects do currents have on the coast

A

erosion
deposition
transport

97
Q

The ocean is an interconnected system powered by the forces of…

A

… wind, tides, Corolis force, sun and water density differences

98
Q

what drives surface ocean currents?

A

wind

99
Q

surface ocean currents result in what type of movement

A

horizontal and vertical

100
Q

factors affecting the size, shape, speed and direction of ocean currents

A 
forces of-
wind
tides
Corolis force
sun
water density

physical characteristics-
shape of ocean basins
topography

101
Q

describe horizontal ocean currents

A

local and typically short term
eg. rip currents
longshore currents
tidal currents

102
Q

describe vertical ocean currents

A

upwelling currents
vertical water movemt and mixing brings cold water towards the surface while pulling warmer, less dense water downward, where it condenses and sinks
this creates a cycle of upwelling and downwelling

103
Q

reversing or rectilinear currents are…

A

tidal currents that ebb and flow in opposite directions

104
Q

“floods”

A

tidal current moving towards the land away from the sea

105
Q

“ebbs”

A

tidal current moving towards the sea away from the land

106
Q

rectilinear tidal currents are typicall found in…

A

coastal rivers and estuaries

107
Q

slack water period

A

when rectilinear tidal currents have a period of no velocity as they move from the ebbing to flooding stage

108
Q

how do tidal currents occur?

A

Occur in conjunction with the rise and fall of the tide
The vertical motion of the tides near the shore causes the water to move horizontally creating currents
Are affected by the different phases of the moon.

109
Q

Relationship between moon phases and tidal and ocean currents

A

full or new phases– tidal currents velocities are strong – spring tides

first or third phases– tidal current velocities are weak– neap currents

110
Q

The effect of Gyres/Coriolis Force on coasts

A

Warm ocean currents transfer heat energy from LOW LATITUDES towards the poles. In the northern hemisphere they particularly effect WESTERN-FACING coastal areas where they are driven by onshore winds. COLD ocean currents do the OPPOSITE, moving cold water from polar regions towards the equator; these are usually driven by offshore winds, and so tend to have less effect on coastal landscapes. The transfer of heat energy may be significant, as it directly affects air temperature and sub-aerial processes.

111
Q

what is the main source of sediment to the coastal budget

A

rivers

Coasts (3 decks)

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