Coastal Systems And Landscapes (Booklet 1) Flashcards
1
Q
What is the atmosphere?
A
The air that surrounds the earth, made up of gases and water vapour.
2
Q
What is the lithosphere?
A
The crust and uppermost mantle; this constitutes the hard and rigid outer layer of the Earth. This layer is split into a number of tectonic plates.
3
Q
What is the hydrosphere?
A
A discontinuous layer of water at or near the Earth’s surface. It includes all liquid and frozen surface waters, groundwater held in soil and rock, and atmospheric water vapour.
4
Q
What is the biosphere?
A
The total sum of all living matter. The biological component of the Earth’s systems.
5
Q
What is a systems approach?
A
A model used to help explain phenomena such as a coastal environment.
6
Q
What is an isolated system?
A
There is no input or output of energy or matter. Some suggest that the universe is the sole example of this type; others claim the idea is not applicable in geography.
7
Q
What is a closed system?
A
There is input, transfer and output of energy but not of matter (or mass).
8
Q
What is an open system?
A
Most environmental systems are open. There are inputs and outputs of both energy and matter.
9
Q
What is a store/component?
A
A section of a system in which matter can remain, be added to or removed from.
10
Q
What is a flow/transfer?
A
Movements between stores/components in a system.
11
Q
What is a boundary?
A
The edge of a particular system.
12
Q
What is dynamic equilibrium?
A
When the inputs and outputs in a system are balanced and the stores stay the same.
13
Q
What is feedback?
A
Occurs when a system changes because of an outside influence. This will upset the dyanamic equilibrium, or state of balance, and affect other components in the system.
14
Q
What is negative feedback?
A
When a system acts by lessening the effect of the original change and ultimately reversing it.
15
Q
What is positive feedback?
A
Occurs within a system where a change causes a further, or snowball effect, continuing or even accelerating the original change; the effects are amplified.
16
Q
What are some examples of inputs in a coastal system?
A
Energy from:
- waves
- winds
- tides
- sea currents
Sediment
Geology of coastline
Sea level change
17
Q
Name some components of coastal systems?
A
Erosional landforms and landscapes.
Depositions landforms and landscapes.
18
Q
Name some outputs of a coastal system?
A
Dissipation of wave energy
Accumulation of sediment above the total limit
Sediment removed beyond local sediment cells.
19
Q
What is a back shore?
A
The area between the high watermark (HMW) and the landward limit of marine activity. Changes usually take place here only during storm activity.
20
Q
What is the foreshore?
A
The area lying between the HWM and the low water mark (LWM). It is the most important zone for marine processes in times that are not influenced by storm activity.
21
Q
What is inshore?
A
The area between the LWM and the point where the waves cease to have any influence on the land beneath them.
22
Q
What is offshore?
A
The area beyond the point where waves cease to impact upon the seabed and in which activity is limited to deposition of sediments.
23
Q
What is nearshore?
A
The area extending seaward from the HWM to the area where waves begin to break. It includes the:
Swash zone
Surf zone
Breaker zone.
24
Q
What is the swash zone?
A
The area where a turbulent layer of water washes up the beach following the breaking of a wave.
25
What is the surf zone?
The area between the point where waves break, forming a foamy, bubbly surface and where the waves then move up the beach as swash in the swash zone.
26
What is wind?
Within the atmosphere, areas of high and low pressure form. In a low pressure area, the air is rising, which draws air in from higher pressure areas. This movement of air from higher pressure to lower air pressure areas is wind.
27
How are waves formed?
Air moves across the water. Frictional drag causes ripples. As the sea bed shallows, friction causes the base of the wave to slow down. The crest continues to rise, steepen and topple over.
28
What will effect the amount of energy provided by the wind?
The distance the wind has blown for (the fetch)
How strong the wind is
The duration for which the wind is blowing.
29
What is the wave crest?
The high point of a wave.
30
What is the wave trough?
The lowest point of the wave.
31
What is the wave height?
The height difference between the crest and the trough.
32
What is the wavelength?
The difference between successive crests.
33
What is the wave period?
The time in seconds between two successive crests or troughs.
34
What is the wave frequency?
The number of waves per minute.
35
What is the swash?
The movement of waves up the beach.
36
What is the backwash?
The movement of waves back down the beach.
37
What are swell waves?
Waves in open water, characterised by long wavelengths and reduced height. They can reach up to 15m high and can travel huge distances.
38
What are storm waves?
Waves generated by local winds which travel only short distances. (These are the waves you might see near the coast).
39
Describe constructive waves.
Distant weather systems generate these waves in the open ocean.
They are low, surging waves with a long wavelength. They have a stronger swash than backwash, meaning that build up the beach. The form on a gentle beach profile (over time the beach will build up and become steeper = negative feedback). The period between each waves is longer than for destructive waves.
40
Describe destuctive waves.
Local storms are responsible for these waves. The are high, plunging waves with a short wavelength. They have a weak swash but a strong backwash. This means that the beach loses debris. They form on steeper beach profiles (over time the beach will flatten = negative feedback). There are more of these waves per minute, so there is a shorter period between successive waves.
41
Describe what happens during wave refraction.
As the wave front meets a headland, the high energy waves are concentrated here. The waves then bends around and moves toward the headland. This means that the lower energy waves are concentrated at the sides of the headland.
42
Explain the formation of tides.
Where a section of the earth points towards the moon, then a high tide will occur as gravity pulls the ocean towards the moon. There will also be a high tide on the oppsosite side of the earth. This occurs as a result of inertia and and centrifugal force, as the gravitational pull is weaker here and the ocean bulges out as a result.
The areas at a 90 degree angle to the moon at this time will experience low tides. As the Earth spins, different areas of the planet face the moon, and this rotation causes the tides to cycle around the planet.
43
What is a spring tide?
When the moon, earth and sun are in alignment this causes the gravitational pull to increase more than usual and creates a high spring tide.
44
What are neap tides?
These are lower tides and they occur when the moon and sun are at right angles to the earth so the gravitational pull from both has a reduces impact. There are two spring tides each lunar month, and two neap tides.
45
What are marine processes?
They operate upon a coastline and are connected with the sea, such as waves, tides and longshore drift.
46
What are sub-aerial processes?
Includes processes that slowly (usually) break down the coastline, weaken the underlying rocks and allow sudden movements or erosion to happen more easily. Material is broken down in situ, remianing in or near to its original position. These may affect the shape of the coastline and include weathering, mass movement and run-off.
Chemical, mechanical and biological weathering
47
What is weathering?
The breakdown and/or decay of rock at or near the Earth's surface creating regolith that REMAINS IN SITU until it is moved by later erosional processes. Weathering can be mechanical, biological/organic or chemical.
48
What is mass movement?
The downhill movement of material under the influence of gravity. E.g. mud or land slides.
49
What is run-off?
All the water that enters a river channel and eventually flows out of the drainage basin.
50
What is marine erosion?
The wearing away od the coastline by the mechanical action and processes of marine waves.
51
What is marine transportation?
The processes that move material from the site where erosion took place to the site of deposition.
52
What is marine deposition?
Where waves are low energy or where rapid coastal erosion provides an abundant supply of material.
53
What is aeolian deposition?
Refers to the entrainment (pick-up), transport and deposition of sediment by wind.
54
What is mechanical/physical weathering?
```
Involves the break-up of rocks without any chemical changes taking place.
E.g.
frost shattering
salt crystallisation
wetting and drying
```
55
What is frost shattering (free thaw)?
Occurs when water enters a crack or join in the rock when it rains and then freezes in cold weather. This expansion exerts pressure on the rock which forces the crack to widen. With repeated freezing and thawing, fragments of rock break away and collect at the base of the cliff as scree. These fragments are then used to aid marine erosion.
56
What is salt crystallisation?
When salt water evaporates it leaves salt crystals behind. These can grow over time and exert stresses in the rock, causing it to break up. Salt can also corrode rock, particularly if it contains traces of iron.
57
What is wetting and drying?
Frequent cycles of wetting and drying are common on the coast. Rocks rich in clay (such as shale) expand when they get wet and contract as they dry. This causes them to crack and break up.
58
What is biological weathering?
```
The breakdown of rocks by organic activity is biological weathering.
E.g. through:
plants
water
birds and animals
marine organisms
```
59
How do plants cause biological weathering?
Thin plant roots grow into small cracks in the cliff face. These cracks widen as the roots grow, which breaks up the rock.
60
How does water cause bilogical weathering?
Water running through decaying vegetation becomes acidic, which leads to increased chemical weathering.
61
How do birds and animals cause biological weathering?
They dig into cliffs.
62
How do marine organisms cause biological weathering?
They are also capable of burrowing into rocksor secreting acids.
63
What is chemical weathering?
```
Involves a chemical reaction where salts may be dissolved or a clay - like deposit may result which is then easily eroded. Where rocks are exposed to air and moisture so chemical pocesses can breakdown the rocks.
E.g.
carbonation
oxidation
solution/hydrolysis and acid rain
```
64
What is carbonation?
Rainwater absorbs carbon dioxide from the air to form weak carbonic acid. This reacts with calcium carbonate in rocks, such as limestone and chalk, to form calcium bicarbonate, which is easily dissolved. The cooler the temperature of the rainwater the more carbon dioxide is absorbed (so carbonation is more effective in winter).
65
What is oxidation?
The reaction of rock minerals with oxygen, for example iron, to form a rusty red powder leaving rocks more vulnerable to weathering.
Causes rocks to disintegrate when the oxyegn dissolved in water reacts with some rock minerals, forming oxides and hydroxides.
66
What is hydrolysis/solution and acid rain?
Fossil fuels react with rainwater making it mildly acidic (sulphur dioxide). The acid rain then reacts with variour minerals in different rocks weakening or dissolving them.
Solution - the dissolving of rock minerals, such as halite (rock salt).
67
What is soil creep?
An extremly slow movement of individual soil particles downhill. The precise mechanism of movement often involves particles rising towards the ground surface due to wetting or freezing and then returning vertically to the surface in response to gravity and as the soil dries out or thaws. This zig-zag movement is simililar to that of longshore drift.
It cannot be seen but is implied by the formation of shallow terracettes, the bending of tree trunks and build up of soil on the upslope.
68
What are mudflows?
Involves earth and mud flowing downhill, usually over unconsolidated or weak bedrock such as clay, often after heavy rainfall.
Water gets trapped within the rock, increasing pore water pressure, which forces rock particles apart and leads to slope failure.
Pore water pressure is a form of energy within the slope system and is an extremly important factor in determining slope instability.
Often sudden and fast.
69
What is a landslide?
Occur on cliffs made from softer rocks or deposited material, which slip as a result of failure within when lubricated, usually following heavy rainfalls.
Involves a block of rock moving very rapidly downhill along a planar surface (a slide plane), often a bedding plane roughly parallel to the ground surface. The moving material remains largely intact,
Triggered by earthquakes or heavy rainfall, when the slip surface becomes lubricated and friction is reduced.
70
What is rockfall?
Involves the sudden collapse or breaking away of individual rock fragments at a cliff face. Commonly associated with steep or vertical cliffs in heavily jointed and often quite resistant rock.
Often triggered by mechanical weathering (particularly freeze-thaw) or an earthquake.
Rocks fall or bounce down the slope to form scree (talus) at the foot of the slope.
Scree forms an input into the sediment cell.
71
What is a landslip or slump (rotational slumping)?
Differs from a landslide in that the slide surface is curved rather than flat.
Commonly occur in weak and unconsolidated clays and sands, often where permeable rocks overlyimpermeable rocks.
Characterised by a sharp break of the slope and the formation of a scar.
Multiple landslides can result in a terraced appearence of the cliff face.
72
How might runoff contribute affect the sediment budget of a coastal environment?
Create a positive budget as particles/sediment are carried in the water.
73
What is hydraulic action (erosion)?
Occurs when waves attack on a cliff or platform edge exerts tremendous hydraulic pressure and erosive force along lines of weakness, often bedding and joint lines- this involves the compression of air in joints and lines of weakness as the waves break, and sudden expansion as the waves retreat and pressure is released.
Therefore hydraulic action involves "pressuring", with the water trapped in cracks, then becoming compressed by the incoming waves, followed by expansion and eventual cracking of rocks.
74
What is wave quarrying?
Wave quarrying refers to the removal of rocks and other debris on cliff or wave-cut platform from their original position by wave action. Quarrying occurs when gradual widneing and deepening of lines of weakness finally permit material of all sizes to be shifted and eventually transported from their situ position (during major storms).
75
What is cavitation?
Occurs when there is intense erosion due to the surface collapse of air bubbles found in rapid flows of water. In the implosion of the bubble, a micro-jet of water is created that travels with high speeds and great pressure producing extreme stress on a very small area of surface.
76
What is corrasion?
When waves advance, they pick up sand and pebbles from the seabed, a temporary store or sediment sink. When they break at the base of the cliff, the trasnported material is hurled at the cliff foot, chipping away at the rock.
77
What is abrasion?
Involves a 'sandpapering' effect as sediment is dragged up and down or across the shoreline, eroding and smoothing rocky surfaces. It is important in the formation of wave-cut platforms.
78
What is solution (corrosion)?
Weak acids in sea water can dissolve albaline rocks (such as chalk or limestone), or the alkaline cement that bonds rock particles together.
79
What is attrition? (not directly responsible for eroding the coastline)
Refers to the gradual wearing down of rock particles by impact and abraision as the pieces of rock are moved by waves, tides and currents. This process gradually makes stones rounder and smoother.
80
What is suspension?
Very small particles of sand and silt are carried along by moving water. Material is also picked up, mainly through tubulence that exists in the water. It can cause a murky appearence in the water.
81
What is solution?
Dissolved materials are transported within the mass of moving water.
82
What is traction?
Large stones and boulders are rolled and slid along the seabed and beach by moving seawater. This happens in high energy environments.
83
What is saltation?
Small stones bounce or leapfrog along the seabed and beach. This process is asociated with relatively high energy conditions. Small particles may be thrust up from the seabed to fallto the bottom again. As these particles land they dislodge other particles upwards, causing more bouncing movements to take place.
84
What are the two ways that wind moves sand?
surface creep and saltation
85
What is surface creep?
A way in which the wind moves sand. It is a process similar to traction, where wind rolls or slides sand grains along the surface.
86
What is saltation?
Where the wind is strong enough to temporarily lift the grains into the air flow to heights of up tp 1 metre for distances of up to 20-30 meters.
87
What is lithology?
The 'make-up' of each individual rock type.
88
What is igneous rock?
Forms when either magma or lava cools down and turns to from solid to liquid. When this happens, igneous rocks form crystals and are said to be crystalline.
Examples of igneous rocks that form deep within the earth are granite or gabbro - here crystals have more time to grow.
Lava cools down very quickly because the surface of the earth is cold. Therefore, rocks such as basalt and obsideon cool so quickly that you see little or no crystals.
89
What is sedimentary rock?
Sediments often collect at the bottom of lakes and oceans. Over time they are squashed and compacted together to become sedimentary rock such as sandstone, limestone or mudstone. Sedimentary rocks are laid down in layers. They may contain fossils.
90
What is metamorphic rock?
Metamorphic rocks are rocks that have changed over time. Pressure and heat causes metamorphic rocks with different textures and/or minerals to form.
The metamorphic rock you end up with depends on the type of rock you start with, and the amount of heat and pressure the rock is put under.
For example, limestone to marble.
91
What factors affect the rate/differences in rate of erosion in coastal environments?
Hardness of rock type
Permeability
Physical make-up of rocks
Chemical composition.
92
Explain how the chemical composition of rocks effects the rate of weathering.
Some rocks, such as quartzite or most sandstones, are made almost completely from silica which is chemically inert. The very low rate of chemical weathering adds resistance to rocks. Other rocks are more prone to rapid chemical weathering because of their chemical composition. For example, iron compounds oxidise in some sandstones. These 'rotted' zones increase vulnerability to subaerial and marine erosion.
93
What is coastal morphology?
Coastal morphology is related not only to the underlying geology, or rock type, but also to its lithology - its geological structure.
94
What characteristics come under lithology?
Strata - layers of rock
Bedding planes - horizontal, natural breaks in the strata, caused by gaps in time during periods of rock formation.
Joints - vertical features caused either by contraction as sediments dry out, or by earth movements during uplift.
Folds - formed by pressure during tectonic activity, which makes rocks buckle and crumple (e.g. The Lulworth Crumple)
Faults - formed when the stress or pressure to which rock is subjected, exceeds its internal strength (causing it to fracture). The faults then slip or move along fault planes.
Dip - refers to the angle at which rock strata lie (horizontally, vertically, dipping towards the sea or dipping inland.
95
What rocks have a good resistance to weathering?
Granite
Chalk (medium/high)
Limestones (medium)
96
What rocks arent very reistant to weathering?
Clay
| Sand and gravel
97
What factors affect the rate of erosion in the coastal environment?
Coastal management
Waves
Sub-aerial processes - weathering and mass movement will weaken cliffs and create piles of debris that are easily eroded by the sea.
Presence or absence of a beach.
Rock type (rock lithology - its physical strength and chemistry)
Geological structure - cracks, joints, bedding planes and faults create weaknesses in a cliff.
98
How does geological structure affect the rate of erosion at a coastline?
Cracks, joints and bedding planes create weakness in a cliff that can be exploited by erosive processes. Variations in rock type and geological structure can lead to the formations of headlands and bays, as a result of subsequent differential erosion.
