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Geography > Coastal landscapes > Flashcards

Coastal landscapes Flashcards

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1
Q

A system

A

A set of interrelated objects comprising components and processes that are connected together to form a working unit.

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2
Q

Coastal landscapes

A

They store and transfer energy (kinetic, potential and thermal ) on time scales.

Open system ~ energy and matter can be
transferred from neighbouring systems as an input and transferred to neighbouring systems as an output.

Has 4 components:
- inputs
- stores
- flows
- outputs

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3
Q

input examples

A
  • kinetic energy from wind and waves
  • thermal energy from the heat of the sun
  • potential energy from the position of material on slopes
  • weathering and mass movement from cliffs
  • material from marine deposition
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4
Q

A process

A

Consists of stores and flows.
store e.g ~beach sediment accumulation
flows e.g ~ movement of sediment along a beach by longshore drift.

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5
Q

output examples

A
  • marine erosion
  • wind erosion
  • evaporation
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6
Q

Equilibrium & dynamic equilibrium

A

Equilibrium ~ the inputs and outputs of a system are equal.
If this is disturbed , the system produces its own response to this to self regulate. This is known as dynamic equilibrium and is an example of negative feedback.

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7
Q

sediment cells

A

A stretch of coastline within which the movement of sediment , sand and shingle is largely self contained.

A closed system ~ however not completely due to variations in wind direction and tidal currents , causing sediment to be transferred.

Boundaries ~ determined by the topography and shape of the coastline.

The only inputs into the cell come from the erosion of the land or sea bed.

  • There are also many sub -cells of a smaller scale existing within the major cells.
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8
Q

5 physical factors influencing coastal landscape

A
  • wind
    -waves
    -tides
    -geology
    -currents
  • these vary in terms of their spatial (from place to place) and their temporal (over time)

-they can be interrelated and influence each other.

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9
Q

wind

A
  • wave action is the source of energy for coastal erosion and sediment transport.
  • Generated by the frictional drag of winds moving across the ocean surface.
  • The higher the wind speed , the larger the fetch, the larger the waves and the more energy they possess.

ONSHORE WINDS ~ drive waves towards the coast.

OBLIQUE WINDS ~ cause waves to move obliquely, generating longshore drift.

Fetch ~ the distance over which wind travels over open water

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10
Q

oblique

A

Neither parallel nor at right angles to a specified or implied line ; slanting.

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11
Q

longshore drift

A

A geological process that moves sediment along a coastline in a zig zag pattern.

Generated by waves approaching obliquely due to wind blowing at an oblique angle.

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12
Q

wave development and breaking

A
  • a wave enters shallow water
  • friction with the sea bed increases
  • the wave slows down as it drags along the bottom
  • the wavelength decreases, and successive waves begin to bunch up.
  • the wave increases in height
  • eventually , the wave plunges and breaks onto shoreline.
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13
Q

wave components

A

Crest ~ the highest part of a wave.

Wave height ~ vertical distance between the crest and the trough.

Wavelength ~ horizontal distance between two adjacent troughs or crests.

Trough ~ lowest part of a wave.

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14
Q

wave frequency
&
wave period

A

wave frequency ~ the number of wave crests passing a point each second.

wave period ~ the time required for the wave crest at one point to reach the second point.

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15
Q

Formula to determine the amount of energy in a wave in deep water

A

P=H2T

P ~ power (Kw per metre of wave front)
H ~ height (metres)
T ~ time interval (between wave crests in seconds)

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16
Q

constructive wave

A
  • low wave height
  • long wavelength, therefore a low frequency.
  • strong swash and a weak backwash
  • This is because the backwash returns to the sea before the next wave , meaning the next swash is uninterrupted and retains its energy.
  • leads to the build up of beach material to form depositional landforms
  • waves spread a long way up the gently sloping beach
17
Q

destructive wave

A
  • steep wave front
  • short wavelength , therefore a high frequency.
  • weak swash and a strong backwash
  • leads to the removal of beach material to form erosional landforms
  • wave does not travel far up the steep beach as energy is directed downwards.
18
Q

swash

A
  • the movement of water up a beach
  • movement is driven by the transfer of energy that occurs when the wave breaks
  • the speed of the swash decreases as it travels further up the beach due to friction and the uphill gradient of the beach.
19
Q

back wash

A
  • the movement of water down a beach
  • movement is driven by gravity and always occurs perpendicular to the coastline.
20
Q

Beach gradient and wave type

A

These have and important and complex relationship.

HIGH ENERGY WAVES ~ remove material from the top of the beach to the offshore zone, reducing the beach gradient.

LOW ENERGY WAVES ~ build up the beach face , steepening the profile.

This is due to :
- wave steepness
- angle of waves
- sediment particle size

21
Q

Tides

A

The periodic rise and fall of the sea surface , produced by the gravitational pull of the moon and sun.

  • The moon pulls water towards it
  • This creates a high tide
  • There is a compensating bulge on the opposite side of the earth.
    -At locations between the two bulges there is a low tide.
    -As the moon orbits the earth the high tide follows it.
22
Q

When do the highest and lowest tidal ranges occur

A

HIGHEST TIDES ~
- occur when the moon , Earth and sun are aligned and so the gravitational pull is the strongest.

  • This causes spring tides with a high tidal range

LOWEST TIDES ~
- When the moon and sun are at right angles to each other the gravitational pull is weak.

-Causes neap tide with a low tidal range

23
Q

Tidal range

A

The vertical difference in height between high tide and low tide.

Influences:
- where wave action occurs
- weathering processes
- impact of processes between tides ( e.g scouring)

Enclosed sea ~ tidal ranges are low so wave action is restricted to a narrow area of land.

Funnelled coast ~ tidal range can be as high as 14 metres.

24
Q

Geology

A

Refers to the lithology and structure of the coast line.

25
Q

Lithology

A
  • Describes the chemical and physical structure of rocks.
  • This will impact physical processes such as weathering , mass movement and erosion.

CLAY ~ weak rock which will erode faster.

BASALT ~ MADE of dense interlocking crystals , meaning it is highly resistant and more likely to form prominent coastal features.

CHALK & LIMESTONE ~ susceptible to chemical weathering due to their calcium carbonate content which is soluble in weak acids.

26
Q

Structure

A
  • Refers to features of jointing, faulting and bedding planes in rocks and also to their permeability.

Affects the shape of the coastline :
CONCORDANT ~ rocks lie parallel to the coastline.
DISCORDANT ~ rocks lie at right angles to the coastline.

Affects the dip of rocks towards the coastline :
LANDWARD dipping rock layers ~ steep cliffs.
SEAWARD dipping rock layers ~ cliffs follow the angle of the dip.

27
Q

Rip currents

A

Narrow currents in the surf zone that move quickly away from shore (up to 5mph).

  • play an important role in the transport of coastal sediment.
  • caused by TIDAL MOTION or by waves breaking at RIGHT ANGLES to the shore.
  1. A cellular circulation is generated by differing wave heights parallel to the shore.
  2. water from the top of breaking waves with a large height travels further up the shore and returns returns through the adjacent area where the lower height waves have broken.

3.once rip currents are forms , they modify the shore profile by creating CUSPS ( a point of transition ) which hep perpetuate (sustain) the rip current, channelling flow through a narrow neck.

28
Q

Ocean currents

A
  • the global pattern of ocean currents is generated by the earths rotation and the currents are set in motion by the wind.
  • WARM ocean currents ~ transfer heat from low latitudes (equator) to high latitudes (polar regions).
  • COLD ocean currents ~ transfer heat from high latitudes to low latitudes.
  • Affects air temperature , therefore SUB-AERIAL PROCESSES.

sub-aerial process ~ collective term for weathering and mass movement processes.

29
Q

Sediment budget

A

The balance between the input and removal of sediment.

Total input - total output

Requires the identification of sediment sources and sinks.

Positive budget:
- more material added than removed
- shoreline builds to the sea (advances)

Negative budget:
- more material removed than added
- shoreline recedes landward.

30
Q

Sources of sediment

A
  • rivers/ streams
    -estuaries
    -wave erosion
    -cliff erosion
    -longshore drift
    -erosion of inland areas by water , wind , ice , mass movement and weathering.
31
Q

how humans use beach nourishment to maintain sediment equilibrium.

A
  • sediment brought by a lorry and dumped on the beach before being spread out by bulldozers (machine).
  • sand and water can be pumped onshore by pipeline from offshore sources, low bunds hold the mixture in place while the water drains away and leaves the sediment behind.
32
Q

Low energy coasts

A
  • low wave energy
  • deposition is greater than erosion

Landforms formed:
- beaches
-spits

Examples:
- sheltered bays
- estuaries
- inlets

33
Q

High energy coasts

A
  • high energy waves
  • strong and steady prevailing wind
  • erosion is greater than deposition

Landforms formed :
- headlands
- wave-cut platforms
- cliffs

Examples:
- Atlantic coasts
- Cornish coasts

Geography (7 decks)

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