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Geography > Coastal landscapes. > Flashcards

Coastal landscapes. Flashcards

1
Q

What energy is in a coastal system that allows geomorphic processes to take place?

A
  • Kinetic energy
  • Potential energy
  • Thermal energy
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2
Q

What two types of energy does a wave possess?

A
  • Potential energy
    (result of position above wave trough)
  • Kinetic energy
    (motion of water within wave)
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3
Q

What is a sediment cell?

A

A sediment cell is a stretch of coastline and it’s associated nearshore area within which the movement of coarse sediment, sand and shingle is largely self contained.

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4
Q

Is a sediment cell a closed or open system?

A
  • Regarded as closed.
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5
Q

What is meant by weathering?

A

Weathering is the breakdown of rocks near the earths surface in situ. by chemical, physical and biological processes.

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6
Q

How many large scale sediment cells found around England and Wales?

A

11

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7
Q

When is a coastal system in a state of dynamic equilibrium?

A

When the systems inputs and outputs are equal.
For example, when the rate of which sediment is added to a beach equals the rate at which sediment is being removed from a beach - therefore, the beach remains the same size.

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8
Q

What happens when dynamic equilibrium is disturbed?

A

The system undergoes self regulation, either responding with positive feedback or negative feedback to restore equilibrium.

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9
Q

What is a closed system?

A

A closed system is where sediment is unable to be transferred from one cell to another, however energy can be transferred.

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10
Q

What is meant by an open system?

A

An open system is where sediment and energy can be transferred across cells.

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11
Q

What are the components of systems?

A
  • Inputs
  • Outputs
  • Processes (consisting of stores/flows)
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12
Q

Why is it unlikely that sediment cells are completely closed systems?

A
  • Variations in wind speed
  • Presence of tidal currents

These two factors means that there is a possibility that sediment can be transferred between cells.

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13
Q

Define coastal landscape.

A

A series of interrelated components (stores) and processes that form a whole.

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13
Q

Give examples of inputs, processes and outputs in a coastal system.

A
  • Inputs: ENERGY
    Kinetic energy from wind and waves
    Thermal energy from sun
    Potential energy from position of material on slope.
  • Processes
    Erosion
    Transportation
    Deposition
  • Outputs
    Marine and wind erosion.
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14
Q

Is a coastal landscape an open or closed system?

A

An open system.
Energy and sediment and transferred in and out from neighboring systems

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15
Q

Name sources of sediment in a coastal system.

A
  • Material from erosion and weathering
  • Material from mass movement.
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16
Q

What is an example of seasonal dynamic equilibrium?

A
  • In Summer, constructive waves build up beaches (having a strong swash and weaker backwash) which creates a steep gradient.
  • In Winter, the waves become destructive due to the beach gradient weakening the swash, whereas backwash is strengthened. This takes sediment off of the beach.

This is seasonal self regulation.

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17
Q

What is longshore drift?

A

The movement of sediment across a beach.

The waves approach a beach at the angle of the wind, whereas the backwash of the waves (under gravity) creates a ‘zig-zag’ movement along the beach.

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18
Q

Explain energy flows in waves.

A

The energy comes from the wind, then is transferred to the waves that carry it across the ocean.
When the wave breaks, the energy is carried forward - being used for either erosion or transportation.

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19
Q

What is the energy of the wave dependent on?

A
  • Strength of the wind
  • Duration of the wind
  • Length of the fetch
    (the longer the fetch, the greater the energy)
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20
Q

Explain how waves break.

A
  • As the wave moves into shallow water, deepest circling molecules come into contact with the seabed, creating friction which slows the trough.
  • The bottom part of the wave (trough) slows faster than the top (the crest), steepening the wave.
  • Instability is created, the crest advances ahead of the trough and topples over, breaking the wave.
    (This creates a significant forward movement of water and energy)
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21
Q

What are tides?

A

Tides are the periodic rise and fall of the sea surface that are produced by the gravitational pull of the moon (and to a lesser extent, the sun)

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22
Q

How are tides formed?

A

The moon pulls water towards it, creating a high tide, on the other side of the earth, there is a compensatory bulge. At locations between the two bulges, there will be a low tide.

As the moon orbits the earth, high tides follow it.

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23
Q

What is a spring tide and how is it formed?

A

A spring tide is a tide that occurs twice each lunar month that has a high tidal range.

It is formed when the earth, sun and moon are all aligned, making gravitational pull its strongest.

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24
Q

What is a neap tide and how is it formed?

A

A neap tide is a tide that occurs twice each lunar month that has a low tidal range.

It is formed when the Moon and the Sun are at right angles to each other, therefore, making the gravitational pull be at its weakest.

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25
Q

How are tidal ranges significant in developing coastal landscapes?

A

Using examples, the Mediterranean is an enclosed area meaning that tidal ranges are low and so wave action is restricted to a narrow area of land.
In places with funneled coasts, such as the Severn Estuary, tidal range is very high.

Tidal range influences where wave action occurs, contributing to weathering processes that occur when the land is exposed. This also could influence the potential scouring effect of waves along coasts with a high tidal range.

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26
Q

What are the two aspects of geology that influence coastal landscape systems?

A
  • Lithology
  • Structure
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27
Q

What is meant by lithology?

A

Lithology is the physical and chemical composition of rocks.

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28
Q

What is meant by structure in rocks?

A

Structure concerns the properties of individual rock types such as jointing, bedding and faulting - also including rock permeability.

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29
Q

How does rock structure influence the planform of coasts on a regional scale?

A

Rock outcrops that are uniform or run parallel to the coast tend to produce straight coastlines, being known as concordant coasts.

Where rocks lie at right angles to the coast they create a discordant planform: the more resistant rocks form headlands whereas the weaker rocks form bays.

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30
Q

What is the difference between constructive and destructive waves?

A
  • Constructive waves.
    Tend to be low in height
    Have a long wave length
    Have a low frequency (6-8 per minute)
    Break by spilling forwards
    Swash energy exceeds backwash energy
  • Destructive waves
    Greater height
    Shorter wave length
    Higher frequency (12-14 per minute)
    Break by plunging downwards
    Backwash energy exceeds swash energy
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31
Q

What are rip currents?

A

Rip currents are currents that are caused either by tidal motion or waves breaking at right angles to the shore.
Rip currents modify the shore profile by creating cusps which help perpetuate the rip current, channeling flow through a narrow neck.

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32
Q

What are ocean currents?

A

A large scale phenomena, generated by the earths rotation and by convection.
These are set into motion by the movement of winds across the water surface.

Warm ocean currents transfer heat energy from low latitudes towards the poles, also doing the opposite and transferring cold water from polar regions towards the equator.

These are driven by offshore winds and tend to have less effect on coastal landscape systems.

!! Their transfer of heat energy can be significant as it directly affects air temperature, and therefore, sub aerial processes.

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33
Q

List 3 sources of coastal sediment.

A
  • Terrestrial
  • Offshore
  • Human
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34
Q

Explain how terrestrial factors are a source of sediment

A
  • Wave erosion contributes to coastal sediment budgets through eroding weak cliffs in high energy environments - this can comprise of large rocks and boulders from the collapse of undercut cliffs.
  • Longshore drift can supply the coast with sediment through transferring this material from neighboring coasts adjacent to the system.
  • Rivers can contribute fluvial input of sediment by depositing their sediments at the coast intermittently (mostly during floods)
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35
Q

Explain how the offshore acts as a source of sediment.

A

Constructive waves can bring sediment onshore from offshore locations and deposit it (marine deposition).
Tides and currents can do the same.

Wind also blows sediment from other locations, including exposed sand bars, dunes and beaches elsewhere along the coastline.

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36
Q

Explain how humans can act as a source of sediment.

A

We can contribute to the sediment budget through intervention when sediment budget is in deficit.
We do this through beach nourishment, bringing in industrial amounts of sand and spreading it along the beach.

Alternatively, sand and water can be pumped onshore by pipeline from offshore sources.

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37
Q

What are the three types of weathering?

A
  • Mechanical (physical)
  • Biological
  • Chemical
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38
Q

What is the definition of weathering?

A

Weathering is the breakdown of rocks in situ. This occurs to exposed rocks near the land surface by physical, chemical or biological processes.

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39
Q

Name 4 processes involved in physical (mechanical) weathering.

A
  • Freeze-thaw
  • Pressure release
  • Thermal expansion
  • Salt crystallization.
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40
Q

What does chemical weathering entail?

A

The decay of rock, involving chemical reactions between moisture and minerals found within the rock.
This can alter the rocks chemical and mineral composition - leaving weak residues of different material that can then be removed by erosion or transportation.

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41
Q

Name 5 processes involved in chemical weathering

A
  • Oxidation
  • Carbonation
  • Solution
  • Hydrolysis
  • Hydration
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42
Q

Does chemical weathering operate more or less in warm environments.

A

Correlating with Van’t-Hoff’s law, chemical weathering processes occur at higher rates in tropical areas rather than temperate or polar regions.

Despite this, carbonation can be more effective in lower temperatures as carbon dioxide is more soluble in colder waters than in warmer waters.

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43
Q

What human factor can increase chemical weathering.

A

Pollution
Pollution creates weakly acidic water.

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44
Q

What does biological weathering entail?

A

Consists of physical actions such as the growth of plant roots or chemical processes such as chelation by organic acids.

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45
Q

Name the two processes involved in biological weathering

A
  • Organic acid chelation
  • Tree roots
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46
Q

Outline the process of freeze-thaw weathering

A
  • Water enters cracks and expands up to 10% when it freezes.
  • In confined spaces, this exerts pressure on the rock causing it to split or fragments to break off.
  • This occurs even in resistant rocks
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47
Q

Outline the process of pressure release.

A
  • When overlying rocks are removed by weathering and erosion, the underlying rock expands and fractures parallel to the surface.
  • This is called dilatation, especially seen in granite.
  • Parallel fractures are called pseudo-bedding planes
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48
Q

Outline the process of thermal expansion.

A
  • Rocks expand when heated and contract when cooled.
  • If subjected to frequent cycles of temperature change than the outer layers may crack and flake off.
  • This is called insolation weathering.
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49
Q

Outline the process of salt crystallization

A
  • Solutions of salt seep into porous rocks.
  • The salts precipitate and form crystals.
  • The growth of salt crystals create stress in the rock and cause disintegration.
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50
Q

Outline the process of oxidation.

A
  • Some minerals react with oxygen, especially IRON.
  • It becomes soluble under extremely acidic conditions and so the original structure is destroyed.
  • This can effect binding, such as damaging the iron rich cements that bind sand grains together in sandstone.
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51
Q

Outline the process of carbonation.

A
  • Rainwater combines with dissolved carbon dioxide from the atmosphere to produce a weak carbonic acid.
  • This can react with calcium carbonate in rocks such as limestone to produce calcium bicarbonate, which makes the rock soluble.
  • This process, however, is reversible.
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52
Q

Outline the process of solution.

A
  • Some salts are soluble in water.
  • Other minerals, such as iron, are only soluble in very acidic water with a pH surrounding 3.
  • Any process by which a mineral dissolves in water is known as solution, however mineral specific processes such as carbonation still operate.
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53
Q

Outline the process of hydrolysis.

A
  • The chemical reaction between rock minerals and water.
  • Silicates combine with water, producing secondary minerals such as clays.
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54
Q

Outline the process of hydration.

A
  • Water molecules added to rock minerals create new minerals of larger volume.
  • Hydration causes surface flaking in many rocks, partly because some minerals also expand during chemical change as they absorb water.
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55
Q

Outline the influence of tree roots on biological weathering.

A
  • Tree roots grow into cracks or joints in rocks and exert outwards pressure.
  • This operates in a similar way and with similar effects to freeze-thaw.
  • When trees topple, their roots can also exert leverage on rock and soil, bringing them to the surface and exposing them to further weathering (especially physical).
  • Burrowing animals may also have a similar effect, with this being particularly significant on cliff tops and cliff faces.
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56
Q

When does mass movement occur?

A
  • When the forces acting on slope material, mainly the resultant force of gravity, exceed the forces keeping the material on the slope (predominantly friction).
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57
Q

What are the main processes of mass movement?

A
  • Rock fall
  • Slides
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58
Q

How and why does rockfall occur (mass movement)

A
  • On cliffs of 40 degrees or more, especially if the cliff face is bare, rocks may become detached from the slope by physical weathering processes.
  • These then fall to the foot of the cliff under gravity.
  • Wave processes usually remove this material, or it may accumulate as a relatively straight, lower angled scree slope.
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59
Q

What are the two types of slumps and how and why do slides occur (mass movement)

A
  • Slides may be linear, with movement along a straight line slip plane, such as a fault or bedding plane between layers of rock.
  • It can also be rotational with movement taking place along a curved slip plane.
  • Rotational slides, therefore can also be known as slumps.
  • Slides occur due to the undercutting by wave erosion at the base of the cliff, removing support for the materials above.
  • Slumps are common in weak rock such as clay that becomes heavier when it is wet, adding to the downslope force.
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60
Q

What are included in the wave process of erosion?

A
  • Abrasion
  • Attrition
  • Hydraulic action
  • Pounding
  • Solution
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61
Q

Define abrasion (or corrasion).

A

When waves armed with rock particles scour against the coastline, rock rubbing against rock.

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62
Q

Define attrition.

A

When rock particles, transported by wave action, collide with each other and with coastal rocks, progressively wearing them away.
This means that they become smoother and more rounded, as well as smaller, eventually producing sand.

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63
Q

Define hydraulic action.

A

When waves break against a cliff face, and air and water trapped in the cracks and crevices become compressed.
As the wave recedes the pressure is released, with the air and water expanding and widening the crack.

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64
Q

Define pounding.

A

When the mass of a breaking wave exerts pressure on the rock causing it to weaken, mostly occurring in destructive waves.

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65
Q

Define solution (or corrosion).

A

When minerals are dissolved, such as magnesium carbonate, in coastal rock.
If the pH of water varies around 7-8, this process is limited unless the water is locally polluted to lower the pH to become more acidic.
Only if water is acidic, coastal rocks containing soluble material is able to be affected by this.

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66
Q

What is the difference between corrasion and corrosion?

A
  • Corrasion: refers to erosion by rock particles scouring the coastline
  • Corrosion: refers to dissolution of minerals within coastal rock.
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67
Q

Name 4 types of transportation

A
  • Suspension
  • Solution
  • Saltation
  • Traction
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68
Q

What is meant by suspension in transportation?

A

Suspension is where small particles of sand, silt and clay can be carried by currents.
This accounts for the muddy appearance of some seawater.
Larger particles can also be carried this way, most likely during storm events.

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69
Q

What is meant by solution in transportation?

A

Solution is where minerals have been dissolved into the mass of moving water.
This type of load is not visible and the minerals remain in the solution until it is evaporated and they precipitate out of the solution.

70
Q

What is meant by saltation in transportation?

A

Saltation is a series of irregular movements of material which is too heavy to be carried continuously in suspension.
Turbulent flow may enable sand-sized particles to be picked up (ENTRAINED) and be carried for a short distance to drop back down and be deposited again.
Similarly, other particles may be dislodged by the impact, allowing water to get beneath them and cause entrainment.

71
Q

What is meant by traction in transportation?

A

Traction is the largest particles in the load being pushed along the seafloor by the force of the flow.
Although this can be referred to as rolling, again the movement is continuous.
Large boulders may undertake a partial rotation before coming to rest again.

72
Q

How does longshore drift work?

A

Longshore drift occurs when waves approach the coast at an angle due to the direction of the dominant wind.
When the waves have broken, the swash carries particles diagonally up the beach.
Under the influence of gravity, the backwash moves them perpendicularly back down the beach.
As this movement repeats, the net result is a movement of material along the beach.

This also leads to the attrition of beach sediment so particles tend to become smaller and more rounded with increasing distance along beach.

73
Q

When does deposition happen?

A

Deposition happens when there is a loss of energy caused by a decrease in velocity and/or volume of water.

74
Q

Where does deposition take place in a coastal landscape?

A
  • Where rate of sediment accumulation exceeds the rate of removal.
  • When waves slow down immediately after breaking.
  • At the top of the swash, where water briefly no longer moves.
  • During the backwash, when water percolates into beach material.
  • In low energy environments, such as those sheltered from winds and waves.
75
Q

What is the velocity at which sediment particles are deposited called?

A

Settling velocity.

The larger and heavier particles require more energy to transport them.
As flow velocity decreases, the largest particles being carried are deposited first and so on, sequentially until the finest particles are deposited.

76
Q

What are the two explanations into how deposition occurs more at the mouth of a river?

A

As rivers enter the sea, there is a reduction in their velocity as flowing water moving through the channel enters the relatively static seawater.
Tides and currents may be moving in the opposite direction to river flow which causes resistance.
Available energy is reduced and so a large amount of the rivers sediment load is deposited.

In addition, the mixing of freshwater and salt water causes flocculation of clay particles. These fine materials clump together due to electrical charges between them in saline conditions.
The result of this is that they become heavier and sink to the sea bed.

77
Q

Name 3 processes in coasts.

A
  • Subaerial processes (operate on land)
  • Marine processes (operate in the sea)
  • Aeolian processes (driven by the wind)
78
Q

What is meant by deflation in aeolian processes?

A

Deflation is the erosion of clay and silt-sized particles by wind action.

79
Q

When does deposition occur in aeolian processes?

A

When wind speed reduces, usually as a result of surface friction.

80
Q

List erosional landforms

A
  • Headlands and bays
  • Cliffs and shore platforms
  • Geos and blowholes
  • Caves, arches, stacks and stumps.
81
Q

How are shore platforms formed?

A
  • When destructive waves break repeatedly on relatively steeply sloping coastlines, undercutting can occur between high and low tide levels.
    This forms a wave cut notch.
  • Continued undercutting weakens support for the rock strata above, eventually collapsing and producing a steep profile and cliff.
  • Continued erosion means that there will be a gently sloping shore platform due to the effects of abrasion.
82
Q

What is the impact of shore platforms on waves?

A
  • As the shore platform grows, the platform will become so wide that the water becomes shallow.
  • This produces smaller waves, even at high tide.
  • This is because friction, slowing down approaching waves meaning that they break on the platform as opposed to the base of the cliff.
    (this slows undercutting, eventually ceasing it)
83
Q

Why do shore platforms gently slope?

A

Shore platforms gently slope due to the cliff becoming higher, this occurs due to the sequence of undercutting, collapse and retreat continuing.

84
Q

Can weathering processes have an effect on shore platform formation?

A
  • Despite predominantly being formed by erosion, weathering processes are also important in development.
  • Solution, freeze-thaw weathering and salt crystallization may all take place dependent on rock type and climatic conditions of the area.
  • Marine organisms, including algae, can accelerate the weathering process when the platform is exposed at low tide.
    At night, algae released CO2, as photosynthesis is not taking place. This mixes with seawater, creating acidity through the formation of carbonic acid - resulting in higher rates of chemical weathering.
85
Q

Where do bays and headlands form?

A

Bays and headlands form adjacent to each other, usually due to the presence of bands of rock of differing resistance to erosion.
This is seen in discordant coastlines.

86
Q

What is a discordant coastline?

A

A coastline with bands of different geologies lying perpendicular to the shore.

87
Q

How does a discordant coastline impact the shape of the land?

A

If adjacent rocks lie perpendicular to the coastline, the weaker rocks are eroded more rapidly to form bays whilst the more resistant rocks remain between bays as headlands.

88
Q

What are the width of bays determined by?

A

The width of the band of weaker rock.

89
Q

What is a concordant coastline?

A

Where alternating bands of hard and soft rock lie parallel to the shore.

90
Q

How do concordant coastlines impact the shape of the land?

A

If the most resistant rock lies on the seaward side, it protects any weaker rocks inland from erosion. This resultant coastline is quite straight and even.
Despite this, occasional small bays or coves form due to erosion in points of weakness, such as fault lines.

91
Q

What is wave refraction?

A

The reorientation of wave fronts as they enter shallow water so that they approach parallel (or roughly parallel) to the shoreline.

92
Q

What happens when waves approach a discordant irregularly shaped coastline?

A

Wave refraction occurs.
As each wave nears the coastline, it is slowed by friction in the shallower water off the headland.
At the same time, the part of the wave crest in the deeper water approaching the bay moves faster as it is not being slowed by friction.

This means that the wave refracts or bends around the headland and orthogonals converge.
Thus, wave energy is focused on the headland and erosion is concentrated there.

In the bays, orthogonals diverge and energy is dissipated, leading to deposition.

93
Q

What are geos?

A

Narrow steep sided inlets.

94
Q

Why do geos form?

A

Even on coastlines with resistant geology, there may be lines of weakness such as joints or faults.
These weak points are eroded more rapidly by wave action than the more resistant rock around them.
Hydraulic action plays a dominant role in this, forcing air and water into the joints and weakening the strata.

Another way they can form is through initially forming tunnel-like caves running at right angles to the cliff line, they become enlarged via erosion and may suffer from roof collapse, creating a geo.

They can be associated with mining shafts.

95
Q

What is a good example of a geo?

A

Huntsman’s Leap in Pembrokeshire.
It is 35m deep and formed from an eroded large joint of carboniferous limestone.

96
Q

How does a blowhole form?

A

After the formation of a tunnel-like cave, its roof may collapse along a master joint and it can form a vertical shaft that reaches the cliff top.
It can also be associated w/ mining shafts.

97
Q

What is a good example of a blowhole?

A

Trevone, Cornwall.

98
Q

How are caves formed?

A

Caves are formed when, due to wave refraction, energy is concentrated on the side of the headlands.
Any points of weakness such as joints or faults are exploited by erosion processes and a small cave may develop on one side, or both sides of the headland.

99
Q

How is a stack formed?

A

A stack formation begins when continued erosion widens an arch and weakens its support. Aided by weathering processes, the arch may collapse, leaving an isolated stack separated from the headland.

100
Q

How is an arch formed?

A

When a cave enlarges, due to erosion, to such an extent where it extends through the other side of the headland, possibly meeting another cave, an arch is formed.

101
Q

How is a stump formed?

A

Further erosion onto the base of an already formed stack may eventually cause further collapse, leaving a small and flat portion of the original stack as a stump.
These may only be visible at low tide.

102
Q

What is a good example of caves, arches, stacks and stumps?

A

Old Harry Rocks at the seaward end of the Foreland near Swanage, located on the Isle of Purbeck.

103
Q

List depositional landforms.

A
  • Beaches
  • Spits
  • Tombolo
  • Salt marshes
  • Onshore bars
  • Deltas
104
Q

What are the three sources of sediment on beaches?

A
  • Cliff erosion
  • Offshore (combed from the seabed during rising sea level)
  • Rivers
105
Q

What are beaches?

A

The most common depositional landform.
They represent the accumulation of material deposited between the lowest rides and the highest storm waves.
Its material consists of sand, pebbles and cobbles.

106
Q

What type of beach gradient does sand produce and why?

A

Beaches with a gentle gradient.
Small particle size means it becomes compact when wet, allowing little percolation during backwash.
As little energy is lost to friction, and little volume is lost to percolation, material is carried back down the beach rather than being left at the top to form a steep gradient.

! This also leads to the development of ridges and runnels parallel to the shore, occasionally breached by channels draining the water off of the beach.

107
Q

What type of beach gradient does shingle produce and why?

A

Beaches with a steep gradient.
In this environment, swash is stronger than the backwash so there is a net movement of shingle onshore.
Shingle may make up the upper part of the beach where there is rapid percolation due to larger air spaces. This means that little backwash occurs and so material is left on top of the beach.

108
Q

How are storm beaches formed?

A

Storm waves hurl pebbles and cobbles to the back of the beach, forming a storm beach or a storm ridge.

109
Q

What is a cusp?

A

Small, semi-circular depressions which are temporary features formed by a collection of waves reaching the same point and when swash and backwash have similar strengths.

110
Q

How do cusps work?

A

The sides of cusps channel incoming swash into the center of the depression, producing a strong backwash - this drags the material down the beach from the center of the cusp, enlarging the depression.

111
Q

What are berms?

A

Berms are smaller ridges that develop at the position of the mean high tide mark, resulting from deposition at the top of the swash.

112
Q

How do ripples form?

A

Ripples form further down the beach in the sand due to the orbital movement of water in waves.

113
Q

Give an example of a beaches equilibrium profile.

A

The balancing of erosion and deposition.

This occurs when high-energy destructive waves remove sediment offshore and create flatter beach profiles.
This results in shallower water, more friction and a reduction in wave energy.
Low-energy constructive waves transfer sediment in the opposite direction to build up steeper profiles - this produces deeper water, less friction and an increase in wave energy.

114
Q

What is the definition of a spit?

A

Spits are long, narrow beaches of sand or shingle that are attached to the land at one end and extend across a bay, estuary or indentation in a coastline.

115
Q

What process forms spits?

A

Longshore drift.
Spits are formed from longshore drift occurring in one dominant direction which carries sediment to the end of the beach and then beyond into open water.

116
Q

What contributes to making a spit more substantial and permanent?

A

Storms.

117
Q

What happens to the end of a spit?

A

It becomes recurved as a result of wave refraction around the end of the spit, and, possibly a secondary wind/wave direction.

118
Q

What can limit the length of a spit forming over an estuary?

A

Actions of the rivers current.

119
Q

What happens in the sheltered area behind the spit and why?

A

Deposition occurs as wave energy is reduced.

120
Q

How are salt marshes formed?

A

They are formed by silt and mud deposit building up behind a spit and the eventual emergence of salt-tolerant vegetation colonizing this area.

121
Q

How are onshore bars formed?

A

Onshore bars can develop if a spit continues to grow across an indentation, such as a cove or a bay, in the coastline until it joins onto land at the other end - creating a BAR.

122
Q

What do onshore bars indirectly create behind it?

A

Lagoons of brackish water on the landward side.

123
Q

What are tombolos?

A

Tombolos are beaches that connect the mainland to an offshore island.

124
Q

How are tombolos formed?

A

They are often formed from spits that have continued to grow seawards until they reach and join an island.

125
Q

Are spits dynamic?

A

YES!
They only exist if deposition exceeds erosion, storm events can lead to the removal of a vast amount of sediment from the spit.
They are low lying, making them vulnerable.

A BAR IS THE SAME

126
Q

Are tombolos dynamic?

A

YES
They only form when sediment load exceeds tidal current and the ability of waves to remove material.

127
Q

What energy environment are salt marshes?

A

A low energy environment.

128
Q

What are salt marshes?

A

Vegetated areas of deposited silt and clays.

129
Q

How are salt marshes consolidated?

A

Salt marshes are subjected twice daily to inundation and exposure as tides rise and fall.
This saline environment leads to the colonization of salt-tolerant flora which help trap sediment, gradually helping to increase the height of the marsh.

130
Q

How to plant features help to trap sediment in salt marshes?

A
  • The stems and leaves of plants act as baffles and trap sediment swept in by tidal currents.
  • The roots stabilize the sediment.
131
Q

What is the impact of sediment trapping by flora on marshes?

A

It increases the height of the marsh, this means that daily submergence period becomes shorter and conditions, therefore become less saline.

132
Q

What is the gradient of salt marshes like?

A

Shallow gradient which slopes seawards

133
Q

What is the difference between the inland area of the marsh and the lower parts of the marsh.

A
  • Salinity
  • Vegetation diversity
  • Turbidity
134
Q

What drains salt marshes?

A

Extensive networks of small, steep-sided channels, or creeks, drain the marsh at low tide.

135
Q

What is found between creeks in salt marshes and what do they do?

A

Shallow depressions.
These trap water when the tide falls, and these areas of salt water (called SALTPANS) are often devoid of any vegetation.

136
Q

What does the development of salt marshes depend on?

A

The rate of accumulation of sediment.

137
Q

What is meant by flocculation?

A

Tiny clay particles carry an electrical charge and repel each other in fresh water.
When in contact with salt water, the particles charge means that they become attracted to each other, combining together to form flocs.
These become large and heavy so they are unable to be carried in river flow so they settle out of suspension.

138
Q

What are deltas?

A

Deltas are relatively large areas of sediment located at the mouths of many rivers.

139
Q

How do deltas form?

A

Deltas form due to deltaic sediments being deposited by rivers and tidal currents, this occurs when the rate of deposition is acting at a faster rate than waves and tides can remove sediment.

140
Q

In what places do deltas typically form?

A
  • Where rivers enter the sea carrying large sediment loads
  • Where Low-energy environments exist in the coastal area
  • Where tidal ranges are low.
141
Q

What are the three distinctive components of deltas?

A
  • Upper delta plain
  • Lower delta plain
  • Submerged delta plain.
142
Q

What are the shape and features of deltas?

A

Deltas are crisscrossed distributaries.
They are overloaded with sediment

143
Q

What are the three types of deltas?

A
  • Cuspate
  • Arcuate
  • Birds foot.
144
Q

What is a eustatic change?

A

A eustatic change is a change in the volume of water in the global ocean store.

145
Q

What influences eustatic change?

A

Variations in mean global temperatures, effecting both the amount of water in the ocean store and its density.

146
Q

What is meant by isostatic change?

A

Changes in land level, brought on by the vertical movement of earths crust.

147
Q

Name physical factors that can affect changes in global temperature and the volume of water in oceans.

A
  • Variations in earths orbit around the sun
  • Variations in energy produced by the sun
  • Changes in the composition of the atmosphere (such as volcanic eruptions which reduce incident solar radiation)
  • Variations in the earths axis tilt.
148
Q

How does a decrease in temperature affect sea level?

A
  • Decrease in global temperature leads to more precipitation being in the form of snow.
  • Eventually, this snow turns to ice and so water is stored on the land in solid form as opposed to liquid form, not being returned to the ocean store as liquid.
  • This results in a reduction in the volume of water in the ocean store and a worldwide fall in sea level.
149
Q

How does a fall in temperature impact water density?

A

As temperatures fall, water molecules contract, increasing the density and reducing volume.

It is estimated that a one degrees fall in mean global temperature causes sea level to fall around 2m.

150
Q

Name emergent landforms.

A
  • Raised beaches
  • Marine terraces
  • Abandoned cliffs
151
Q

Name submergent landforms.

A
  • Rias
  • Fjords.
152
Q

What are emergent landforms?

A

Landforms shaped by wave processes during times of high sea level that are left exposed when sea level falls.

153
Q

What are raised beaches?

A

Emergent landforms that are areas of former shore platforms, they are left at a higher level than the present sea level.

154
Q

Where are raised beaches usually found?

A

Raised beaches are usually found a distance inland from the present coastline.

155
Q

Where are abandoned cliffs found?

A

Behind the beach among emergent coastlines, they often include wave-cut notches, caves and even stacks and arches.

156
Q

What are marine terraces?

A

Marine terraces are much larger scale landscape features than raised beaches, which are quite small scale and localized at the base of relic cliffs.

Terraces do not necessarily have cliffs above them.

157
Q

How are marine terraces formed?

A

Similar to raised beaches, marine erosion during a previous period of higher sea level contributes to this.
This occurs over a longer time scale than raised beaches, tending to be substantially larger.

158
Q

What is a real life example of a raised beach?

A

Southern tip of the Isle of Portland.

  • It has a height of around 15m above the present day sea level.
  • Thought to have formed around 125000 years ago during the Tyrrhenian inter-glacial period where sea level was much higher.
  • The Portland limestone was eroded via hydraulic wave action, partly through the exploitation of the bedding plane weakness.
159
Q

How are emergent landforms modified?

A

As they are no longer submerged, emergent landforms are no longer affected by wave processes.
They are affected by weathering and mass movement.

160
Q

Using the Isle of Portland as an example, how has this emergent landform been modified?

A

The cliff face has been gradually degraded by frost weathering processes, leading to rockfall from the cliff face.

  • In the post glacial period, warmer and wetter weather has led to an increase in chemical weathering, especially in the form of carbonation on the limestone cliffs and platforms.
    Biological weathering has also been enhanced by climate, increasing colonisation of vegetation and marine organisms.
161
Q

How does an increase in temperature increase sea level?

A

An increase in global temperature leads to higher rates of ice melting that is stored on land in ice sheets, ice caps and glacial valleys.
As a consequence, there is a global increase in the volume of water in the ocean.

162
Q

What was the period of significant sea level rise called?

A

Flandrian Transgression.

163
Q

What is the impact of temperature increase on water density?

A

As temperature rises, water molecules expand - leading to increased volume.
A one degree rise in temperature contributes around 2m to sea level.

164
Q

What are rias?

A

Rias are submerged river valleys, formed as sea level rises.

165
Q

How are rias formed?

A
  • The lowest part of the rivers coal year and the floodplains alongside it may be completely drowned.
  • The higher land forming the tops of the valley sides and the middle and upper part of the rivers course remains exposed.
166
Q

What does the cross section of a ria look like?

A
  • The cross section has relatively shallow water becoming increasingly deep towards the centre.
  • The exposed valley sides gently slope.
167
Q

What is the long section of a ria like?

A
  • They have a smooth profile and water of uniform depth.
168
Q

What are real life examples of rias?

A

The south-coasts of Devon and Cornwall, including those at Salcombe, Knightsbridge and Fowey.

169
Q

When were rias formed?

A

During the Flandrian Transgression.

170
Q

What are fjörds?

A

Fjords are submerged glacial valleys.

171
Q

What are features of fjords?

A
  • Steep, almost cliff like valley sides
  • Water is uniformly deep.
172
Q

What does the cross section of a fjord look like?

A
  • It is U-shaped, reflecting the original shape of the glacial valley itself.

Geography (8 decks)

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