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GEO1020 > Coastal Zone Processes and Forms > Flashcards

Coastal Zone Processes and Forms Flashcards

1
Q

What percentage of the world’s population live within 2km of the coastline?

A

50%

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2
Q

What does the coastal change exhibit change over?

A

A range of timescales

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3
Q

What does the coastal zone adjust to?

A

Wave, tide and current processes

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4
Q

What is the coastal zone an important buffer between?

A

The marine and terrestrial environments

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5
Q

What 4 things does the coastal zone act as?

A

Important ecological reserve
Economic resource
Communication corridor
Recreational playground

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6
Q

What are the 4 areas of the coastal zone?

A

Coastal plain
Shore
Nearshore
Offshore

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7
Q

What is the shore composed of?

A

Foreshore and backshore

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8
Q

Where do waves break?

A

In the surf zone

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9
Q

Where does swash and backwash occur?

A

The shoreline

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10
Q

What are sea waves produced by?

A

Localised storm activity at sea

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11
Q

How do swell waves form?

A

Once the waves have left the generation area, they lose height and energy to become swell waves

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12
Q

What is the wave form?

A

Sinusoidal form

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13
Q

What are 6 definable components of waves?

A 
Wave crest
Trough
Height
Steepness
Frequency
Period
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14
Q

What does wave height increase with?

A

Wind speed, duration and fetch distance

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15
Q

What was the largest wave ever recorded?

A

34m in february 1933 in the Pacific

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16
Q

What type of wave moves fast?

A

Long waves

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17
Q

What type of wave dissipates a lot of its energy along its journey?

A

Short waves

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18
Q

What type of wave moves slow?

A

Short waves

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19
Q

What type of wave doesn’t lose much energy?

A

Long waves

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20
Q

What waves do coasts facing the open ocean experience?

A

Long waves that have overwhelmed short waves

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21
Q

What waves are deflected by the Coriolis effect?

A

Deep water waves

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22
Q

Why can small ripples evolve into full sea waves?

A

Due to wind duration and frictional drag on the sea surface

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23
Q

What can a ripple increase?

A

Sea surface area

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24
Q

What is a result of increasing the sea surface area?

A

Air mass has more frictional drag which increases wave amplitude

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25
Q

What pulls up the ascending limb?

A

The push of the air mass

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26
Q

What pulls down the descending limb?

A

The force of gravity

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27
Q

What is the height of the wave proportional to?

A

The height of the wave is DIRECTLY proportional to the strength and duration of the wind passing over the surface

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28
Q

Why do wave fields occur?

A

Waves produced at different times and places and vary in magnitude, direction and speed meet together

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29
Q

What happens when two waves meet to form a wave field?

A

They become superimposed on each other and produce complex wave fields

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30
Q

What are the patterns of wave fields?

A

Cyclic-surf-beat

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31
Q

What happens with waves on short fetch coastlines?

A

They arrive at the same time as choppy conditions

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32
Q

Why do waves on short fetch coastlines arrive at the same time as choppy conditions?

A

They have insufficient time to separate

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33
Q

What happens to the waves on long fetch coastlines?

A

Long waves dominate and surf beat develops

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34
Q

What does a wave perturb when it approaches the coastline?

A

A wave perturbs the water depth equal to 1/2 wavelength to the wave base

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35
Q

Where does schoaling occur?

A

When the wave depth is greater than the water depth

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36
Q

What happens to waves in shallow water?

A

Frictional drag of bed causes the wave to slow
Wave length decreases but wave height increases
Steepens until unstable and breaks

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37
Q

What is the critical ratio of water depth to wave height when waves are in shallow water?

A

0.6=1.2

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38
Q

What type of wave travels further coastward before breaking?

A

Low waves travel further coastward before breaking

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39
Q

What does shoaling cause?

A

The orbital wave motion to become distorted

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40
Q

Why is the angle of the shore important?

A

Steep- waves break close to the shoreline

Flat- waves break further offshore

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41
Q

What are the 4 things waves can do when they reach the coastline?

A

Spill, plunge, surge or collapse

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42
Q

What 3 things does the interaction of the wave with near shore topography cause?

A

Refraction
Reflection
Diffraction

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43
Q

What are tides?

A

Waves generated by the gravitational pull of astronomical bodies

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44
Q

What does the gravitational force of the moon cause?

A

Reduction in the Earth’s centrifugal force which affects the oceanic surface mass

45
Q

What are the two main features of spring tides?

A

Greater magnitude tides during new and full moon

Sun and moon pull along the same vector

46
Q

What are the two main features of neap tides?

A

Less magnitude tides during half moon phases

Sun and moon pull in opposite direction

47
Q

Which type of tide (spring or neap) has stronger tides?

A

Spring tides are stronger

48
Q

Which type of tide (spring or neap) has a higher tidal range?

A

Spring

49
Q

What is the rate of the longshore currents?

A

0.1-0.2ms-1 to 1ms-1 if wind direction is along shore

50
Q

Explain longshore currents

A

Water moves along the beach and gets trapped between breaking waves and beach slope

51
Q

Why are rip currents dangerous?

A

They develop a strong circulation cell

52
Q

How are rip currents formed?

A

Water forced up the beach forces its way back down the slope against breaking waves along the line of least resilience

53
Q

What are tidal currents due to?

A

The rise and fall of the tide

54
Q

What are swash and backwash mechanisms for?

A

Movement of sediment up and down the beach

55
Q

What is longshore drift?

A

Sediment movement along the beach in swash and backwash at an angle.

56
Q

What is net erosion?

A

Longshore drift with no sediment supply from the coast

57
Q

What is a pocket beach?

A

A crescent shaped beach

58
Q

How do pocket beaches form?

A

Sediment from eroding cliffs is transported by littoral drift along the sides of the bay. This then converges on the head of the bay

59
Q

What is erosion a function of?

A

Wave environment, local geology and coastal morphology

60
Q

List 7 marine processes

A 
Wave quarrying
Abrasion
Wetting-drying
Salt crystallisation
Thermal expansion and contraction
Biological activity
61
Q

Give 3 examples of sub aerial processes

A

Landslides
Rotational slumps
Mudflows

62
Q

What is coastal retreat?

A

The cyclical removal of fallen sediment from a cliff base

63
Q

What are developed as a result of coastal retreat? (5)

A

Wave cut notches, caves, arches, stacks and blowholes

64
Q

What complex feedback occurs at coasts?

A

Between the cliff erosion, platform width and wave energy potential

65
Q

What are 3 types of cliff and shore platform morphology?

A

Sloping shore platform
Horizontal shore platform
Plunging cliff

66
Q

What is an example of a depositional landform?

A

A beach

67
Q

What is a beach?

A

Accumulation of unconsolidated material

68
Q

Why is dynamic equilibrium maintained at beaches?

A

Sediment is highly mobile

69
Q

What is a beach profile a function of?

A

Coastal processes and sediment type

70
Q

What are three topographical features found on beach profiles?

A

Cusps, berms and ripples

71
Q

What can often be found above high tide?

A

A coastal dune system

72
Q

Why are there curved features on beach planforms?

A

Due to refraction

73
Q

What 5 things can be found on a beach planform?

A 
Spits
Barrier islands
Barrier beaches
Tombolos
Lagoons
74
Q

What are the 3 models for barrier beach formation?

A

Emerged-transgressive model
Submerged-transgressive model
Emerged-standstill model

75
Q

Explain the emerged-transgressive model

A

Offshore bars formed during last glacial low SL period

Bars develop vertically and sediment accumulates as sea level rises

76
Q

Explain the submerged-transgressive model

A

Coastal dunes during the lower sea levels

Become isolation from mainland upon submergence

77
Q

Explain the emerged-standstill model

A

Barrier islands formed since post-glacial sea level stabilised 4000 years ago

78
Q

What evidence is against the emerged standstill model

A

Many barrier island deposits are older than 4000 years old

79
Q

What are estuaries?

A

Coastal embayments from which rivers flow

80
Q

What can shift the estuaries in tide dominated coasts?

A

Tidal currents shift inlet channels

81
Q

Where do estuaries receive sediment from?

A

The sea and river

82
Q

When do estuaries form and what is this opposite to?

A

They form when net sediment movement is landwards and this is opposite to deltas

83
Q

What are the 3 subdivided spatial facets of tide dominated estuaries?

A

Upper estuary
Lower estuary
Middle estuary

84
Q

What dominates the upper estuary in tide dominated coastlines?

A

Fluvial

85
Q

What dominates the middle estuary in tide dominated coastlines?

A

Well mixed

86
Q

What dominates the lower estuary in tide dominated coastlines?

A

Tidal

87
Q

What are the two types of estuary?

A

Tide dominated

Wave dominated

88
Q

What is salt-fresh water mixing a result of in estuaries?

A

Diffusion and advection

89
Q

What happens to the form of estuaries overtime?

A

They become more and more similar

90
Q

On what type of coast can deltas be found?

A

River dominated coasts

91
Q

Where do deltas form?

A

At the mouth of sediment rich fluvial channels

92
Q

What are the 3 main groups of deltas?

A

Cuspate
Elongate
Estuarine

93
Q

What do some deltas resemble?

A

A bird’s foot with branching distributaries carrying river water and sediment to the ocean

94
Q

What are short term sea level changes due to?

A

Tidal

Meteorological

95
Q

What are longer term changes in sea level due to?

A

Isostacy and eustacy

96
Q

Give 3 types of evidence for sea level change

A

Erosional and depositional landforms
Biological indicators
Archaeological remains and historical records

97
Q

Give two examples of erosional and depostional landforms that are evidence of sea level change

A

Tidal flats and wave cut notches

98
Q

Give an example of a biological indicator of sea level change

A

Fossils

99
Q

What does falling sea level cause?

A

Abandonment of coastal features

100
Q

What does rising sea level cause? (3)

A

Drowning of coastal features
Migration of mobile features
Increased erosion

101
Q

What is the orbit of a wave?

A

Circular movement of water

102
Q

What are waves produced by?

A

Wind

103
Q

What are waves a source of?

A

Energy

104
Q

What type of wave lengths are associated with tsunamis?

A

Long wave lengths

105
Q

When do waves start to show?

A

When the wave base hits the shore

106
Q

How does the wave shape change when the wave base hits the shore?

A

Changes from orbital to elliptical

107
Q

What type of wave fronts do steeper beaches tend to have?

A

Steeper beaches tend to have smaller wave fronts

108
Q

What two cycles are tides dominated by?

A

Lunar and solar

GEO1020 (16 decks)

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