Coastal Zone Processes and Forms Flashcards
1
Q
What percentage of the world’s population live within 2km of the coastline?
A
50%
2
Q
What does the coastal change exhibit change over?
A
A range of timescales
3
Q
What does the coastal zone adjust to?
A
Wave, tide and current processes
4
Q
What is the coastal zone an important buffer between?
A
The marine and terrestrial environments
5
Q
What 4 things does the coastal zone act as?
A
Important ecological reserve
Economic resource
Communication corridor
Recreational playground
6
Q
What are the 4 areas of the coastal zone?
A
Coastal plain
Shore
Nearshore
Offshore
7
Q
What is the shore composed of?
A
Foreshore and backshore
8
Q
Where do waves break?
A
In the surf zone
9
Q
Where does swash and backwash occur?
A
The shoreline
10
Q
What are sea waves produced by?
A
Localised storm activity at sea
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
12
Q
What is the wave form?
A
Sinusoidal form
13
Q
What are 6 definable components of waves?
A
Wave crest Trough Height Steepness Frequency Period
14
Q
What does wave height increase with?
A
Wind speed, duration and fetch distance
15
Q
What was the largest wave ever recorded?
A
34m in february 1933 in the Pacific
16
Q
What type of wave moves fast?
A
Long waves
17
Q
What type of wave dissipates a lot of its energy along its journey?
A
Short waves
18
Q
What type of wave moves slow?
A
Short waves
19
Q
What type of wave doesn’t lose much energy?
A
Long waves
20
Q
What waves do coasts facing the open ocean experience?
A
Long waves that have overwhelmed short waves
21
Q
What waves are deflected by the Coriolis effect?
A
Deep water waves
22
Q
Why can small ripples evolve into full sea waves?
A
Due to wind duration and frictional drag on the sea surface
23
Q
What can a ripple increase?
A
Sea surface area
24
Q
What is a result of increasing the sea surface area?
A
Air mass has more frictional drag which increases wave amplitude
25
What pulls up the ascending limb?
The push of the air mass
26
What pulls down the descending limb?
The force of gravity
27
What is the height of the wave proportional to?
The height of the wave is DIRECTLY proportional to the strength and duration of the wind passing over the surface
28
Why do wave fields occur?
Waves produced at different times and places and vary in magnitude, direction and speed meet together
29
What happens when two waves meet to form a wave field?
They become superimposed on each other and produce complex wave fields
30
What are the patterns of wave fields?
Cyclic-surf-beat
31
What happens with waves on short fetch coastlines?
They arrive at the same time as choppy conditions
32
Why do waves on short fetch coastlines arrive at the same time as choppy conditions?
They have insufficient time to separate
33
What happens to the waves on long fetch coastlines?
Long waves dominate and surf beat develops
34
What does a wave perturb when it approaches the coastline?
A wave perturbs the water depth equal to 1/2 wavelength to the wave base
35
Where does schoaling occur?
When the wave depth is greater than the water depth
36
What happens to waves in shallow water?
Frictional drag of bed causes the wave to slow
Wave length decreases but wave height increases
Steepens until unstable and breaks
37
What is the critical ratio of water depth to wave height when waves are in shallow water?
0.6=1.2
38
What type of wave travels further coastward before breaking?
Low waves travel further coastward before breaking
39
What does shoaling cause?
The orbital wave motion to become distorted
40
Why is the angle of the shore important?
Steep- waves break close to the shoreline
| Flat- waves break further offshore
41
What are the 4 things waves can do when they reach the coastline?
Spill, plunge, surge or collapse
42
What 3 things does the interaction of the wave with near shore topography cause?
Refraction
Reflection
Diffraction
43
What are tides?
Waves generated by the gravitational pull of astronomical bodies
44
What does the gravitational force of the moon cause?
Reduction in the Earth's centrifugal force which affects the oceanic surface mass
45
What are the two main features of spring tides?
Greater magnitude tides during new and full moon
| Sun and moon pull along the same vector
46
What are the two main features of neap tides?
Less magnitude tides during half moon phases
| Sun and moon pull in opposite direction
47
Which type of tide (spring or neap) has stronger tides?
Spring tides are stronger
48
Which type of tide (spring or neap) has a higher tidal range?
Spring
49
What is the rate of the longshore currents?
0.1-0.2ms-1 to 1ms-1 if wind direction is along shore
50
Explain longshore currents
Water moves along the beach and gets trapped between breaking waves and beach slope
51
Why are rip currents dangerous?
They develop a strong circulation cell
52
How are rip currents formed?
Water forced up the beach forces its way back down the slope against breaking waves along the line of least resilience
53
What are tidal currents due to?
The rise and fall of the tide
54
What are swash and backwash mechanisms for?
Movement of sediment up and down the beach
55
What is longshore drift?
Sediment movement along the beach in swash and backwash at an angle.
56
What is net erosion?
Longshore drift with no sediment supply from the coast
57
What is a pocket beach?
A crescent shaped beach
58
How do pocket beaches form?
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
What is erosion a function of?
Wave environment, local geology and coastal morphology
60
List 7 marine processes
```
Wave quarrying
Abrasion
Wetting-drying
Salt crystallisation
Thermal expansion and contraction
Biological activity
```
61
Give 3 examples of sub aerial processes
Landslides
Rotational slumps
Mudflows
62
What is coastal retreat?
The cyclical removal of fallen sediment from a cliff base
63
What are developed as a result of coastal retreat? (5)
Wave cut notches, caves, arches, stacks and blowholes
64
What complex feedback occurs at coasts?
Between the cliff erosion, platform width and wave energy potential
65
What are 3 types of cliff and shore platform morphology?
Sloping shore platform
Horizontal shore platform
Plunging cliff
66
What is an example of a depositional landform?
A beach
67
What is a beach?
Accumulation of unconsolidated material
68
Why is dynamic equilibrium maintained at beaches?
Sediment is highly mobile
69
What is a beach profile a function of?
Coastal processes and sediment type
70
What are three topographical features found on beach profiles?
Cusps, berms and ripples
71
What can often be found above high tide?
A coastal dune system
72
Why are there curved features on beach planforms?
Due to refraction
73
What 5 things can be found on a beach planform?
```
Spits
Barrier islands
Barrier beaches
Tombolos
Lagoons
```
74
What are the 3 models for barrier beach formation?
Emerged-transgressive model
Submerged-transgressive model
Emerged-standstill model
75
Explain the emerged-transgressive model
Offshore bars formed during last glacial low SL period
| Bars develop vertically and sediment accumulates as sea level rises
76
Explain the submerged-transgressive model
Coastal dunes during the lower sea levels
| Become isolation from mainland upon submergence
77
Explain the emerged-standstill model
Barrier islands formed since post-glacial sea level stabilised 4000 years ago
78
What evidence is against the emerged standstill model
Many barrier island deposits are older than 4000 years old
79
What are estuaries?
Coastal embayments from which rivers flow
80
What can shift the estuaries in tide dominated coasts?
Tidal currents shift inlet channels
81
Where do estuaries receive sediment from?
The sea and river
82
When do estuaries form and what is this opposite to?
They form when net sediment movement is landwards and this is opposite to deltas
83
What are the 3 subdivided spatial facets of tide dominated estuaries?
Upper estuary
Lower estuary
Middle estuary
84
What dominates the upper estuary in tide dominated coastlines?
Fluvial
85
What dominates the middle estuary in tide dominated coastlines?
Well mixed
86
What dominates the lower estuary in tide dominated coastlines?
Tidal
87
What are the two types of estuary?
Tide dominated
| Wave dominated
88
What is salt-fresh water mixing a result of in estuaries?
Diffusion and advection
89
What happens to the form of estuaries overtime?
They become more and more similar
90
On what type of coast can deltas be found?
River dominated coasts
91
Where do deltas form?
At the mouth of sediment rich fluvial channels
92
What are the 3 main groups of deltas?
Cuspate
Elongate
Estuarine
93
What do some deltas resemble?
A bird's foot with branching distributaries carrying river water and sediment to the ocean
94
What are short term sea level changes due to?
Tidal
| Meteorological
95
What are longer term changes in sea level due to?
Isostacy and eustacy
96
Give 3 types of evidence for sea level change
Erosional and depositional landforms
Biological indicators
Archaeological remains and historical records
97
Give two examples of erosional and depostional landforms that are evidence of sea level change
Tidal flats and wave cut notches
98
Give an example of a biological indicator of sea level change
Fossils
99
What does falling sea level cause?
Abandonment of coastal features
100
What does rising sea level cause? (3)
Drowning of coastal features
Migration of mobile features
Increased erosion
101
What is the orbit of a wave?
Circular movement of water
102
What are waves produced by?
Wind
103
What are waves a source of?
Energy
104
What type of wave lengths are associated with tsunamis?
Long wave lengths
105
When do waves start to show?
When the wave base hits the shore
106
How does the wave shape change when the wave base hits the shore?
Changes from orbital to elliptical
107
What type of wave fronts do steeper beaches tend to have?
Steeper beaches tend to have smaller wave fronts
108
What two cycles are tides dominated by?
Lunar and solar
