2.a. Coastal landforms are inter-related and together make up characteristic landscapes. Flashcards
(118 cards)
1
Q
What are geomorphic processes?
A
Processes that shape coastal landforms.
2
Q
What are the 5 geomorphic processes? Which shape erosion/ depositional landforms?
A
Weathering. (Shape erosion landforms).
Mass Movement. (Shape erosion landforms).
Wave Processes. (Shape erosion landforms).
Aeolian Processes. (Shape deposition landforms).
Fluvial Processes. (Shape deposition landforms).
3
Q
What is weathering?
(Weathering)
A
A process which uses energy (mostly thermal) to produce physically, chemically or biologically altered materials from surface or near surface rock.
4
Q
What are the types of weathering?
A
Physical/ mechanical, biological, and chemical.
5
Q
Physical weathering is the largest contributor to what?
(Physical/ Mechanical Weathering)
A
Rock breakdown.
6
Q
How does physical weathering erode rock?
(Physical/ Mechanical Weathering)
A
By increasing the surface area exposed.
This allows other weathering processes to occur.
7
Q
What can render physical weathering less effective?
(Physical/ Mechanical Weathering)
A
Low air temperatures.
8
Q
When water enters a rock crack and freezes, how much does it expand by?
(Freeze-Thaw)
(Physical/ Mechanical Weathering)
A
Nearly 10%.
9
Q
What is freeze thaw weathering?
(Freeze-Thaw)
(Physical/ Mechanical Weathering)
A
The process by which the expansion of water in a rock (confined spaces) exerts pressure, causing it to split and break off.
10
Q
Does freeze-thaw weathering work only on weak rocks?
(Freeze-Thaw)
(Physical/ Mechanical Weathering)
A
No, the process even works on resistant rocks.
11
Q
Outline the process of salt crystallisation.
(Salt crystallisation)
(Physical/ Mechanical Weathering)
A
Solutions of salt seep into porous rock.
The salts then precipitate forming crystals.
This eventually dissolves the rock from stress.
12
Q
Give an example of a salt solution. By how much does this expand by when in temperatures of around 26-28°C?
(Salt crystallisation)
(Physical/ Mechanical Weathering)
A
Sodium sulphate, sodium carbonate.
Roughly 300%.
13
Q
What is chemical weathering?
(Chemical weathering)
A
The decay of rock which involves chemical reactions between moisture and some minerals within the rock.
It can: reduce stability, reduce the rock to chemical constituents and later chemical composition.
14
Q
What can chemical weathering do to a rock?
(Chemical weathering)
A
Reduce stability.
Reduce the rock to chemical constituents and later, chemical composition.
15
Q
Outline the process of carbonation.
(Carbonation)
(Chemical weathering)
A
Rainwater combines with dissolved CO2 from the atmosphere to produce a weak carbonic acid.
This reacts with calcium carbonate in rocks, e.g. limestone, to produce calcium bicarbonate (soluble).
16
Q
Is carbonation reversible?
(Carbonation)
(Chemical weathering)
A
Yes.
17
Q
The precipitation of calcite happens during what? What does this form?
(Carbonation)
(Chemical weathering)
A
Evaporation of calcium rich water in caves.
This forms stalagmites and stalactites.
18
Q
What is oxidation?
(Oxidation)
(Chemical weathering)
A
The process that causes minerals in rocks to react with oxygen, either in the air or water.
19
Q
What element is especially susceptible to oxidation? Why?
(Oxidation)
(Chemical weathering)
A
Iron.
This is because it becomes very soluble under extreme acidic conditions, in turn destroying its original structures.
20
Q
Oxidation often attacks what combination of rock.
(Oxidation)
(Chemical weathering)
A
Iron-rich cements that bind sand grit together in limestone.
21
Q
What happens to some salts when in water?
(Solution)
(Chemical weathering)
A
They become soluble.
22
Q
Some salts become soluble in water. Give an example of a salt that does not do this. How does it affected instead?
(Solution)
(Chemical weathering)
A
Iron.
It is only affected by very acidic waters (around pH 3).
23
Q
What is solution?
(Solution)
(Chemical weathering)
A
Any process by which a material dissolves in water.
(However, mineral specific processes such as carbonation can be separately identified).
24
Q
State Van’t Hoff’s law.
(Chemical weathering)
A
A 10°C change leads to a x2.5 increased rate of chemical reactions, (up to 600°C).
25
How do tree roots cause stress in rocks?
(Tree roots)
(Biological weathering)
Grow into cracks and joints exerting pressure outwards.
26
How does the falling of trees weather rocks?
(Tree roots)
(Biological weathering)
Their roots can exert leverage on rock and soil.
This exposes them on the surface to furthering weathering processes.
27
Other than falling trees exposing rocks and soils, what else can do this?
(Tree roots)
(Biological weathering)
Burrowing animals.
28
Tree roots can have a significant effect when they are where?
(Tree roots)
(Biological weathering)
On cliff tops and cliff faces.
29
When are organic acids produced?
(Organic acids)
(Biological weathering)
During the decomposition of plant and animal litter.
30
Organic acids are created from the decomposition of litter, but how does this contribute to weathering?
(Organic acids)
(Biological weathering)
Causes soil water to become more acidic.
This then reacts with some minerals (chelation).
31
What is chelation?
(Organic acids)
(Biological weathering)
Where organisms produce organic substances that have the ability to decompose minerals and rocks by the removal of metallic cations.
32
How can blue-green algae produce a weathering effect?
(Organic acids)
(Biological weathering)
By producing a shiny film or iron and manganese oxides onto rocks.
33
Outline how biological weathering may occur on onshore platforms.
(Organic acids)
(Biological weathering)
Through molluscs.
These may secrete acids which produce small surface hollows in the rock.
34
What is mass movement?
(Mass movement)
The process by which forces act on a slope where gravity exceeds friction.
35
Where is mass movement most significant?
(Mass movement)
Cliffs.
36
When mass movement occurs on cliffs, what happens to sediment?
(Mass movement)
Rock and regolith fall and are added to the sediment budget.
37
Rock-falls occur on a cliff of what angle?
(Rock-falls)
(Mass movement)
40° or more.
38
Rock-falls are primarily influenced by what weathering type? How?
(Rock-falls)
(Mass movement)
Physical weathering.
This is done through the exploiting of joints and exposed bedding planes.
39
How do wave process contribute to the mass movement process?
(Rock-falls)
(Mass movement)
They erode the moved material, e.g. fallen from cliffs.
40
When do slides often occur?
(Slides)
(Mass movement)
Often common when waves undercut the cliff base.
41
Slides often move in what way? What do they move along?
(Slides)
(Mass movement)
In a linear motion.
They move along a fault or bedding plane.
42
Rotational slides are also called what?
(Slides)
(Mass movement)
Slumps.
43
When do slumps occur?
(Slides)
(Mass movement)
When there is movement along a curved slip plane.
44
Slumps are common in what rock type?
(Slides)
(Mass movement)
Weak rock types, e.g. clay.
45
Why do slumps occur in weak rock types?
(Slides)
(Mass movement)
This is because the rock becomes heavier as it gets increasingly more wet (gravity influence is stronger).
46
When sand is above a concealed weak rock type, why is it more likely to become wet?
(Slides)
(Mass movement)
Due to the open structure of the sand particles.
47
What is wave erosion?
(Erosion)
(Wave processes)
When breaking waves are able to erode the coastline.
48
Outline abrasion.
(Erosion)
(Wave processes)
Rocks rubbing the coastlines rock.
49
Outline attrition.
(Erosion)
(Wave processes)
Rocks hitting other rocks.
50
Outline hydraulic action.
(Erosion)
(Wave processes)
Waves breaking a cliff face due to water becoming trapped in cracks and being compressed.
51
Outline pounding.
(Erosion)
(Wave processes)
When the mass of a wave breaking against a cliff face exerts large volumes of pressure.
52
Outline solution.
(Erosion)
(Wave processes)
Dissolving materials in coastal rock (only occurs in acidic/ polluted water with rocks containing soluble minerals).
53
What are the 5 wave erosion processes?
(Erosion)
(Wave processes)
Abrasion.
Attrition.
Hydraulic action.
Pounding.
Solution.
54
What is wave transportation?
(Transportation)
(Wave processes)
The process by which waves carry sediment onshore.
55
What are the 4 wave transportation processes?
(Transportation)
(Wave processes)
Solution.
Suspension.
Saltation.
Traction.
(Longshore drift).
56
Outline solution.
(Transportation)
(Wave processes)
Minerals that have been dissolved in the water.
(They remain in solution until evaporated out).
57
Outline suspension.
(Transportation)
(Wave processes)
Small particles of sand, silt and clay carried by currents.
This accounts for the brown appearance.
58
Outline saltation.
(Transportation)
(Wave processes)
A series of irregular movements of material due to turbulent flow (rocks being carried and dropped).
59
Outline traction.
(Transportation)
(Wave processes)
Largest particles are pushed along the sea floor by the force of flow.
60
What is wave deposition?
(Deposition)
(Wave processes)
Marine sediment that is dropped when there is a loss of energy caused by a decrease in velocity and/ or volume of water.
61
State 3 factors in a coastal landscape system that make deposition more likely.
(Deposition)
(Wave processes)
When rate of sediment accumulation exceeds the rate of removal.
When waves slow down immediately after breaking.
At the top of the swash where the wave is briefly stationary.
During the backwash, when water percolates into the beach material.
In low-energy environments, such as those sheltered from winds and waves e.g. estuaries.
62
What sediments are harder to transport?
(Deposition)
(Wave processes)
Larger rock particles.
63
What is settling velocity?
(Deposition)
(Wave processes)
The velocity at which sediment is deposited.
64
What sediments have a high settling velocity?
(Deposition)
(Wave processes)
Rocks.
65
What sediments have a low settling velocity?
(Deposition)
(Wave processes)
Sand/ silt/ clay.
66
What happens when flow velocity decreases?
(Deposition)
(Wave processes)
The largest particles being carried are deposited first and so on, sequentially until the finest particles are deposited.
67
(Erosion)
(Fluvial processes)
68
Where does fluvial erosion normally take place? Give an example.
(Erosion)
(Fluvial processes)
In high catchment areas.
E.g. in steep mountains where lots of material is eroded.
69
How is fluvial erosion similar to wave erosion?
(Erosion)
(Fluvial processes)
They both experience high energy flow and high energy events.
70
What happens to a river's sediment load as its catchment decreases?
(Erosion)
(Fluvial processes)
The sediment load increases.
71
What are the fluvial transportation processes?
(Transportation)
(Fluvial processes)
Traction.
Suspension.
Saltation.
Solution.
(Exactly the same as waves, except longshore drift).
72
When does fluvial deposition often occur? Why is this?
(Deposition)
(Fluvial processes)
When the river meets the sea.
This is because the velocity decreases in waves, currents and tides.
This slows fluvial velocity, and deposits sediment.
73
What is brackish water?
(Deposition)
(Fluvial processes)
Areas where salt and fresh water meet.
74
In brackish water, how is clay deposited?
(Deposition)
(Fluvial processes)
Through flocculation.
75
Why are coastal landforms especially influenced by winds?
(Aeolian processes)
The open sea surfaces expose coastal landforms.
76
What wind type is most significant to the shaping of coasts?
(Aeolian processes)
Onshore winds.
77
Wind is able to pick up sand particles and move them by what process?
(Erosion)
(Aeolian processes)
Deflation.
78
Sand grains are moved by surface rolling and saltation at what speeds?
(Erosion)
(Aeolian processes)
40km/hour.
79
How are silt and clay particles carried? What does this mean for their erosional properties?
(Erosion)
(Aeolian processes)
Suspension.
This restricts abrasion to a height of about 1m and has limited effect on rocky coastlines and cliffs.
80
Why is dry sand easier to move than wet sand?
(Erosion)
(Aeolian processes)
As moisture increases cohesion - thus making it heavier.
81
How does wind move material?
(Transportation)
(Aeolian processes)
By using the same mechanisms as water moving in rivers or waves (except solution and longshore drift).
82
Attrition on land is particularly effective in wind. Why?
(Erosion)
(Aeolian processes)
Particles tend to be carried a greater distance than when in water.
This is because particles are not protected from collisions by the film of water around them.
83
Particles are able to be carried at velocities as low as what?
(Transportation)
(Aeolian processes)
20 km/hour.
84
Saltation requires sediment of what range?
(Transportation)
(Aeolian processes)
0.15 - 0.25 mm.
84
Suspension requires sediment of what range?
(Transportation)
(Aeolian processes)
0.05 - 0.14 mm.
85
Surface rolling/ creep requires sediment of what range?
(Transportation)
(Aeolian processes)
0.26 - 2 mm.
86
Material carried by wind will be deposited when what falls? What is this normally a result of?
(Deposition)
(Aeolian processes)
Wind speed.
This is usually as a result of surface friction.
86
Aeolian deposition usually occurs where? Why?
(Deposition)
(Aeolian processes)
Inland.
This is where friction from vegetation and surface irregularities are much greater than on the open sea.
87
How are cliffs and shore platforms formed?
(Cliffs and shore platforms)
(Coastal landforms)
When destructive waves break repeatedly steep sloping coastlines, undercutting can occur between tide levels forming a wave-cut notch.
Continued undercutting from waves weakens support for the rock strata above, eventually collapsing and producing a steep profile and a cliff.
The removal of debris at the foot of the cliff by wave action ensures that the cliff profile remains steep and that the cliffs retreat inland parallel to the coast.
Weathering processes are also important in development. Solution, freeze-thaw and salt crystallisation may all take place depending on the rock type and the climatic conditions of the location.
88
Give an example of a cliff.
Give an example of a shore platform.
(Cliffs and shore platforms)
(Coastal landforms)
An example of cliffs is 'Flamborough Head' in Yorkshire.
An example of a shore platform is 'Robin Hood's Bay' in Yorkshire.
89
How do headlands and bays form?
(Headlands and bays)
(Coastal landforms)
Typically form adjacent to each other, usually due to the presence of bands of rock of differing resistance to erosion.
If these rock outcrops lie perpendicular to the coastline, the weaker rocks are eroded more rapidly to form bays while the more resistant rock remain between bays as headlands.
This results in a discordant coastline. Rocks lying parallel to the coastline produce a concordant coastline.
The result is a concordant coastline which is quite straight and even; however, even in this situation small bays or coves may occasionally be eroded by wave/ aeolian processes at points of weakness such as fault lines.
90
Give an example of a headland and bay.
(Headlands and bays)
(Coastal landforms)
An example of headlands and bays is 'The Isle of Purbeck' in Dorset.
91
How do geos form?
(Geos and blowholes)
(Coastal landforms)
Wave processes take advantage of lines of weakness, even on coastlines with resistant geology, e.g. joints and faults.
Hydraulic action is particularly important in forcing air and water into the joints and weakening the rock strata.
Geos may initially form as tunnel-like caves running at right angles to the cliff angles to the cliff line, which as they become enlarged by continuing erosion may suffer from roof collapse, creating a geo.
92
Give an example of a geo.
Give an example of a blowhole.
(Geos and blowholes)
(Coastal landforms)
An example of a geo is 'Huntsman's Leap' in Pembrokeshire.
An example of a blowhole is 'Trevone' in Cornwall.
93
How do blowholes form?
(Geos and blowholes)
(Coastal landforms)
When part of a geos roof cave collapses along a master joint forming a vertical shaft that reaches the cliff top.
94
What are geos?
(Geos and blowholes)
(Coastal landforms)
Narrow, steep-sided inlets.
95
How are caves-stumps formed?
(Caves, Arches, Stacks and Stumps)
(Coastal landforms)
Wave refraction means energy is concentrated on the sides of headlands.
Any points of weakness, such as faults or joints, are exploited by erosion process (wave or aeolian) and a small cave may develop on one side, or even both sides, of the headland.
Wave attack is concentrated between high and low tide levels this is where caves form. If the cave enlarges, potentially meeting another cave on the other side, an arch may be formed.
When the top of the arch is eroded by weathering, it will 'stand' alone and become a stack.
As the stack is gently eroded it will shorten to a stump.
96
Give an example of the cave-stump process.
(Caves, Arches, Stacks and Stumps)
(Coastal landforms)
An example of this is 'Old Harry's Rocks' in Dorset.
97
What is a beach?
(Beaches)
(Coastal landforms)
The accumulation of material deposited between the lowest tides and the highest storm waves.
98
What percentage of beach material originates from cliff erosion?
(Beaches)
(Coastal landforms)
Typically around 5%.
99
What percentage of beach material originates from offshore sources?
(Beaches)
(Coastal landforms)
Typically 5%, gathered from seabed
100
What percentage of beach material originates from fluvial sources?
(Beaches)
(Coastal landforms)
90% carried into coastal system as suspended and bed load through river mouth
101
How are storm beaches/ storm ridges formed?
(Beaches)
(Coastal landforms)
Storm waves hurl pebbles and cobbles to the back of the beach.
102
Give an example of a beach.
(Beaches)
(Coastal landforms)
An example of this is 'Sandbanks' in Poole.
103
How are spits formed?
(Spits)
(Coastal landforms)
By longshore drift occurring in one dominant direction, carrying beach material to the end of the beach and then beyond into the open water.
The end of the spit often becomes recurved as a results of wave refraction around the end of the spit and, possibly, the presence of a secondary wind/ wave action direction.
In the sheltered area behind the spit, deposition will occur as wave energy is reduced.
104
If a spit forms across an estuary, what may be limited? By what?
(Spits)
(Coastal landforms)
Its length may be limited by the actions of the river current.
105
Give an example of a spit.
(Spits)
(Coastal landforms)
An example of this is 'Orford Ness' in East Anglia.
106
What are salt marshes?
(Spits)
(Coastal landforms)
Features of low-energy environments, such as estuaries and on the landward side of spits.
They are vegetated areas of deposited slits and clays.
107
What are salt marshes subjected to twice a day?
(Spits)
(Coastal landforms)
Inundation and exposure as tides rise and fall.
108
How are onshore bars formed?
(Onshore bars)
(Coastal landforms)
Develop if a spit continues to grow across an indentation, such as a cove or bay, in the coastline until it joins onto the land at the other end, usually from aeolian processes and longshore drift.
109
Give an example of an onshore bar.
(Onshore bars)
(Coastal landforms)
An example of this is 'Torcross' in Devon.
110
How are tombolos formed?
(Tombolos)
(Coastal landforms)
Formed when a spit connects the mainland coast to an island.
The process of longshore drift occurs, and this moves material along the coastline. (Wave processes and aeolian processes).
111
Give an example of a tombolo.
(Tombolos)
(Coastal landforms)
An example of this is 'Burgh Island (beach)' in Devon.
112
What are deltas?
(Deltas)
(Coastal landforms)
Large areas of sediment found at the mouths of many rivers.
113
Deltaic sediments are deposited by what?
(Deltas)
(Coastal landforms)
Rivers and by tidal currents.
114
Give an example of a delta.
(Deltas)
(Coastal landforms)
An example of this is the 'Rhone Delta' in France.
115
What are the three most common types of deltas?
(Deltas)
(Coastal landforms)
Cuspate, arcuate, and bird’s foot.
115
How do deltas form?
(Deltas)
(Coastal landforms)
When rivers and tidal currents deposit sediment at a faster rate than waves and tides can remove it.
They typically form where: rivers entering the sea are carrying large sediment loads, a broad continental shelf margin exists at the river mouth to provide a platform for sediment accumulation, low-energy environments exist in the coastal area or where tidal ranges are low.
