Coasts Flashcards
1
Q
What type of system is the coast?
A
An open system.
2
Q
What is a sediment cell?
A
An area of the coastline where the sediment is almost contained and a dynamic equilibrium is reached.
3
Q
What is a negative feedback loop?
A
A loop that lessens any change which has occurred within the system.
4
Q
What is an example of a negative feedback system at the coast?
A
1) Destructive waves erode material from a beach during a storm and deposit it as an offshore bar.
2) The bar dissipates the wave energy which protects the beach from further erosion.
3) Over time, the bar gets eroded instead of the beach.
4) Once the bar has gone, normal conditions occur and the system returns to dynamic equilibrium.
5
Q
What is a positive feedback loop?
A
A loop that exaggerates a change which makes the system more unstable and further away from dynamic equilibrium.
6
Q
What is an example of a positive feedback loop at the coast?
A
1) People walking over sand dunes destroys vegetation growing there and causes erosion.
2) As the roots from the plants have been stabilising the sand dune, damaging the plants causes more erosion to occur.
3) Eventually, the sand dunes will be completely eroded which causes more erosion to occur on the beach.
7
Q
Where does most of the sediment in a sediment cell come from?
A
Rivers.
8
Q
What are three sources of sediment?
A
Rivers
Cliff Erosion
Longshore Drift
9
Q
What is a sediment budget?
A
The difference between the amount of sediment that enters the system and the amount that leaves.
10
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 the waves.
11
Q
How do waves form?
A
Winds moving across the surface of water causing frictional drag.
12
Q
How do waves form and break?
A
1) Winds move across the surface of the water and exert frictional drag on the surface of the water. This causes a circular motion of water particles.
2) As the seabed gets shallower, friction on the seabed causes the motion to become more elliptical.
3) This causes the wave height to increase but the wavelength and wave velocity to decrease.
4) This causes water to build up behind the wave until the wave breaks.
13
Q
What are the three factors that affect the size of a wave?
A
Strength of the wind.
Duration of the wind.
Size of the fetch.
14
Q
What is the fetch?
A
The distance over which the wind blows.
15
Q
What are the two different types of wave?
A
Constructive and destructive.
16
Q
What do constructive waves cause?
A
Deposition to occur on the beach.
17
Q
Why do constructive waves deposit sediment?
A
The swash is stronger than the backwash.
18
Q
What do destructive waves cause?
A
Erosion.
19
Q
Why do destructive waves cause erosion?
A
The backwash is stronger than the swash.
20
Q
What are three features of constructive waves?
A
Long wavelength
Low frequency
Strong swash, weak backwash.
21
Q
What are three features of a destructive wave?
A
Short wavelength
High frequency
Weak swash, strong backwash.
22
Q
What is a negative feedback system for a beach?
A
1) Constructive waves cause deposition which causes the beach profile to become steeper.
2) Steeper beaches favour the formation of destructive waves.
3) The destructive waves then erode the beach, reducing the gradient of the beach profile.
4) This causes more constructive waves to occur.
23
Q
What is a tide?
A
Gravitational pull from the sun and moon causes the water level to change.
24
Q
What is the tidal range?
A
The difference in height between high and low tide.
25
What is a spring tide?
When the sun and moon are in alignment, this causes the greatest pull.
Spring tides have the greatest tidal range.
26
What is a neap tide?
When the sun and moon are perpendicular to each other, their gravitational forces act against each other.
Neap tides have the smallest tidal range.
27
What is a high energy coastline?
A coastline that is associated with powerful waves.
Erosion is the favoured process.
28
What is a low energy coastline?
A coastline that is associated with less powerful waves.
Deposition is the dominant process.
29
What is wave refraction?
The process where waves turn towards a headland due to the depths of the ocean floor. The wave energy is focussed on the headland and away from the bays.
30
How does wave refraction cause a negative feedback loop?
1) Wave refraction causes increased energy at the headlands and decreased energy in the bays.
2) Therefore, more erosion occurs and the headlands.
3) Eventually, the headlands are worn away and increased erosion occurs at the bays.
31
What are the four main processes of erosion?
Hydraulic action
Attrition
Abrasion
Corrosion
32
What is hydraulic action?
As a wave crashes into the cliff, air is compressed into cracks in the rock. This pressure causes the cracks to widen.
33
What is attrition?
Wave action causes pebbles to hit against each other which causes them to become smaller and more rounded.
34
What is abrasion?
Where sediment rubs against the coastline causing it to wear down.
Rocks can also be hurled at the cliff and eroded.
35
What is corrosion?
Acidic seawater causes alkaline rocks to be eroded.
36
What is wave quarrying?
Very similar to hydraulic action in that air is compressed but this exerts a much greater force and pulls rocks away from the cliff.
37
What are two factors that affect the rate of erosion?
Energy of the waves.
Rock type.
38
What are the four main processes of transportation?
Traction
Saltation
Suspension
Solution
39
What is traction?
Large, heavy sediment rolls along the sea bed pushed by currents.
40
What is saltation?
Smaller sediment bounces along the seabed, being pushed by currents.
41
What is suspension?
Small sediment is carried with the flow of the water.
42
What is solution?
Dissolved material is carried within the water, potentially in a chemical form.
43
How does longshore drift occur?
1) Waves hit the beach at an angle determined by the direction of the prevailing wind.
2) The waves push sediment in this direction and up the beach in the swash.
3) Due to gravity, the wave carries sediment back down the beach in the backwash.
4) Over time, this moves sediment across a beach.
44
What is deposition?
Where waves drop sediment as they lower in energy.
45
What are the two types of deposition?
Gravity settling
Flocculation
46
What is gravity settling?
The water's velocity decreases so sediment begins to be deposited.
47
What is flocculation?
Clay particles clump together due to chemical attraction and then sink due to their high density.
48
What is weathering?
The breakdown of rocks in situ.
49
How can weathering form a positive feedback cycle?
1) If the rate of removal of weathered rock from the base of the cliff is higher than the rate of weathering, further weathering is promoted.
2) This is because the area of exposed rock is increased.
3) This increases the rate of erosion.
50
How can weathering form a negative feedback cycle?
1) If the removal of weathered rock from the base of the cliff is slower than the rate of weathering, this causes a decrease in weathering.
2) This is because there is a build up of debris at the base of the cliff which reduces the exposed cliff area.
51
What are the three types of weathering?
Mechanical (Physical)
Biological
Chemical
52
What is mechanical (physical) weathering?
The breakdown of rocks due to exertion of physical forces without any chemical changes taking place.
53
What are two types of mechanical (physical) weathering?
Freeze-thaw weathering.
Salt crystallisation.
54
What is freeze-thaw weathering?
1) Water enters cracks in rocks and then freezes.
2) This causes the volume to expand by around 10%.
3) This puts pressure on the rock and causes it to expand.
55
What is salt crystallisation?
1) As seawater evaporates, salt is left behind.
| 2) Salt crystals grow over time which exerts pressure on the rock.
56
What is chemical weathering?
The breakdown of rocks through chemical reactions.
57
What are two types of chemical weathering?
Carbonation
Oxidation
58
What is carbonation?
Rainwater reacts with CO₂ to create carbonic acid which reacts with limestone.
59
What is oxidation?
Where minerals become oxidised and they increase in size.
60
What is biological weathering?
The breakdown of rocks by organic activity.
61
What are two types of biological weathering?
Plant roots
Birds
62
How can plant roots cause weathering?
Roots of plants grow into cracks of rocks which exerts pressure.
63
How can birds cause weathering?
Some birds dig holes into the cliff which weakens them.
64
What is mass movement?
The movement of material down a slope under the influence of gravity.
65
What are the three main types of mass movement?
Slumps
Slides
Rockfalls
66
What is a slump?
Where material moves down a slope with a rotation.
They are usually caused due to heavy rain increasing the mass of the soil.
67
What is a slide?
Where material moves down a slope in a straight line.
68
What is rockfall?
Where material breaks apart due to weathering and rolls down a slope. A scree slope is created at the base of the cliff.
69
What are six coastal landforms of deposition?
Beaches
Spits
Bars and Tombolos
Barrier Beaches
Sand Dunes
Estuarine Mudflats and Salt Marshes
70
How does a beach form?
Constructive waves deposit sediment on the shore.
71
What are the features of a shingle beach?
Steep and narrow.
Made up of larger particles.
72
What are the features of a sandy beach?
Flat and wide.
Made up of smaller particles.
73
What are three features found at a beach?
Berms
Runnels
Cusps
74
What is a berm?
A ridge of sand or pebbles found at high tide marks.
75
What is a runnel?
Grooves in the sand running parallel to the shore.
They are formed by the backwash draining into the sea.
76
What is a cusp?
A crescent-shaped indentation.
They form on beaches made of mixed sand and shingle.
77
What is a spit?
An area of sediment that extends over the coastline. They form where there is a sharp change in the shape of the coastline such as the mouth of a river.
78
How does a spit form?
Longshore drift deposits material across the river mouth leaving a bank of sand and shingle sticking out into the sea.
79
Why can a spit form a recurved end?
Energy from the river can cause a change in direction.
Changes in the prevailing wind/wave direction.
80
What is a bar?
A bar of sediment that connects two headlands together.
This can occur across a bay or river mouth.
81
What is a tombolo?
A bar that connects the shore to an island.
82
What forms behind a bar?
A lagoon.
83
What is a barrier beach?
Long, narrow islands of sediment that run parallel to the shore but are detached from it.
84
How is a sand dune formed?
1) Onshore winds cause sand to move up the beach.
2) The sand is trapped by driftwood or berms.
3) Pioneer species such as marram grass colonise the sand dune and their roots stabilise the dune.
4) This encourages more sand to accumulate.
5) As plants die, the soil becomes richer which allows larger species to stabilise the dune even more.
85
Where are mudflats or saltmarshes formed?
Very low energy environments such as estuaries or behind spits.
86
How does a mudflat/salt marsh form?
1) Behind a spit, the energy is very low.
2) This causes silt and mud to be deposited. Flocculation also causes mud to clump together and be deposited.
3) Halophilic (organisms that live in salt) vegetation colonises the mudflat/saltmarsh.
4) The plants trap more mud and silt and gradually build an area that remains exposed for longer and longer between tides.
5) Erosion by streams causes channels in the surface.
87
What are the two types of sea level change?
Eustatic and isostatic.
88
What is eustatic sea level change?
Global sea level rise.
89
What are the two causes of eustatic sea level change?
Changes in climate
Tectonic movements
90
How can changes in climate affect sea levels?
Higher temperatures mean glaciers and ice sheets melt which increases sea level.
Thermal expansion also occurs.
91
How can tectonic movement affect eustatic sea level?
Tectonic movements change the shape and therefore volume of the oceans.
For example, sea floor spreading increases the volume of the basin and so decreases sea levels.
92
What is isostatic sea level change?
Vertical movements of land relative to the sea cause a change in sea level.
These are local effects.
93
What can cause isostatic sea level change?
Isostatic rebound and depression.
94
What is isostatic depression?
The mass of an ice sheet or glacier causes the crust to sink further into the asthenosphere.
95
What is isostatic rebound?
When a glacier/ice sheet melts and the mass is reduced, the crust rises up slowly.
96
What is the pattern for sea level change in the last 12,000 years?
Sea levels have increased as the Earth comes out of an ice age.
4,000 years ago, sea levels stabilised.
Now, sea levels are increasing.
97
How does climate change affect sea levels?
Climate change causes glaciers to melt and thermal expansion to occur causing eustatic sea level rise.
98
What are some impacts of eustatic sea level rise?
Increased erosion which puts coastal towns at a greater risk.
Increased coastal flooding.
Submergence of low lying areas such as the Maldives.
99
How are coastlines of emergence created?
When sea level falls relative to the coast.
100
What are key features of coastlines of emergence?
Raised beaches
Marine platforms
Relict cliffs
101
How does a raised beach form?
A fall in sea level leaves beaches above the high tide mark. Over time, the sediment becomes vegetated and develops into soil.
102
What is a marine platform?
Where a wave cut platform is raised above the relative sea level.
103
What is a relict cliff?
As the cliffs are no longer eroded by the sea, vegetation covers them. Caves, arches and stacks can be found in relict cliffs.
104
How are coastlines of submergence created?
When sea levels rise relative to the coast.
105
What three features can be found at coastlines of submergence?
Rias
Fjords
Dalmatian Coastlines
106
What is a ria?
A ria is a flooded river valley.
107
How is a ria formed?
The sea level rises over the old river valley and floods it.
108
What is a fjord?
Glacial valleys that have been flooded.
They have very steep sides and are very deep.
109
How are fjords formed?
Sea levels rise over valleys that glaciers existed in.
110
What is a Dalmatian Coastline?
A series of islands that are caused by valleys flooding which are parallel to the coast.
111
What are the four options for coastal management?
Hold the line
Advance the line
Do nothing
Managed realignment.
112
What is hold the line?
Maintain the existing coastal defences.
113
What is advance the line?
Build new coastal defences further out to sea than the existing line of defence.
114
What is do nothing?
Build no coastal defences at all and deal with erosion and flooding as it happens.
115
What is managed realignment?
Allow the shoreline to move, but manage retreat so it causes the least damage.
116
What are the two types of coastal defences?
Hard engineering
Soft engineering
117
What is hard engineering?
Using man-made structures to prevent erosion.
118
What is soft engineering?
Using natural processes to prevent erosion.
119
What is a sea wall?
A curved concrete wall that protects the coastline by absorbing energy and the curvature causes energy to be reflected.
120
What is a revetment?
Slanted structures built at the foot of cliffs. They absorb wave energy to reduce erosion.
121
What are gabions?
Rock filled cages.
They absorb wave energy.
122
What is rip-rap / rock armour?
Boulders piled up along the coast.
They absorb wave energy and so reduce erosion.
123
What are groynes?
Fences built at right angles to the coast which trap beach material transported by longshore drift.
This creates wider beaches which slow the waves down, reducing erosion.
124
What are breakwaters?
Concrete blocks or boulders deposited off the coast.
They cause the waves to break offshore which reduces their energy.
125
What is beach nourishment?
Where sand or shingle is added to beaches from elsewhere.
This creates wide beaches which reduce erosion.
126
What is dune regeneration?
Sand dunes are created or restored by nourishment and stabilisation of the sand.
These absorb wave energy and reduce flooding and erosion.
127
How does creating marshland prevent erosion?
Vegetation in a marshland stabilises the sediment and reduces the speed of the waves.
128
What is a Shoreline Management Plan (SMP)?
A plan that is devised for managing different areas with the aim of protecting important sites without causing problems elsewhere in the sediment cell.
The plan is developed for a single sediment cell and all of the local authorities within the cell devise the plan.
129
What is Integrated Coastal Zone Management (ICZM)?
ICZM considers all elements of the coastal system (land, water, people, the economy) when devising a management strategy. It aims to protect the coastal zone in a relatively natural state.
