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Y12 A Level Geography- Leathers > Systems (Coasts) > Flashcards

Systems (Coasts) Flashcards

1
Q

What type of system are coasts?

A

Coasts are “natural open systems”

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2
Q

Where do inputs of sediment come from?
Where does energy come from?
What are the main flows/ transfers?
What are the stores of sediment?

A

Rivers, flooded river valleys called estuaries, cliff costal erosion, waves wind and tides bringing in offshore deposits.

Wind, Waves, Tides, Currants

Erosion, Weathering, Mass movement, Transportation

Beaches, dunes, spits, offshore bars, tombolo.

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3
Q

Define a sediment cell?

A

A largely self contained stretch of coastline, usually defined by two headlands.
A CLOSED SYSTEM, however can be disturbed during storm events.
Has its own inputs and outputs of sediment. “discrete”
Sediment is sourced, transferred and stored and is away from local wave action and LSD.

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4
Q

Define sediment budget?

A

The relationship between erosion and deposition that can be used to predict the changing shape of the coastline.

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5
Q

What is the effect of a positive and negative sediment budget?

A 
POSITIVE= beach gain 
NEGATIVE= beach loss
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6
Q

Give an example of dynamic equilibrium at the coast?

A

Coasts are generally in dynamic equilibrium.
WAVE TYPE AND BEACH GRADIENT
eg: constructive waves deposit sediment and beach gradient becomes steeper——- encourages destructive waves that plunge instead of surge leading to wave quarrying and h.d.a——- destructive waves erode and remove sediment and beach gradient decreases.

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7
Q

Positive feedback example at the coast?

A

Erosion takes place leading to a need for coastal management implementation——- groynes are put in place to trap sediment and interfere with LSD—— groynes save implementation area, but accelerate and increase costal erosion elsewhere.

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8
Q

Negative feedback example at coast?

A

Rates of cliff erosion increase——- eroded material forms a “scree slope” that slumps down the cliff face and protects it from sub-aerial processes and erosion———- rates of cliff erosion decrease.

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9
Q

Define wind?

How is wind created?

A

Wind is the movement of air from a high pressure to a low pressure.
Created as fluctuating temperatures lead to the formation of “pressure systems”.

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10
Q

What are the prevailing (dominant) winds within the UK?

A

The “westerlies” from the SW. Travel from sub-tropical areas over a vast expanse of the Atlantic Ocean.

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11
Q

What three factors effect wave energy?

A
  1. The strength of the wind (determined by the PRESSURE GRADIENT)
  2. The duration the wind blows for
  3. The FETCH - the distance the wind blows over
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12
Q

Describe the process of wave formation?

A
  1. Air moves over the water and frictional drag is created causing small ripples to form.
  2. Close to the shore, locally, water moves in an orbital motion
  3. Initially a circular orbit of water within the wave is created.
  4. However, due to increased friction and shallower waters a elliptical movement is created.
  5. As the wave reaches the shore, VELOCITY AND WAVELENGTH DECREASES, but WAVE HEIGHT increases.
  6. Swash breaks up the beach and backwash falls back down.
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13
Q

Compare the two types of wave- constructive and destructive?

A

CONSTRUCTIVE DESTRUCTIVE

  • low frequency (6-8/ min) -high frequency (10-14/min)
  • low wave height + velocity -high wh and velocity
  • Circular orbit -Elliptical orbit
  • beach gain -beach loss
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14
Q

Define Tides?

What is the tidal range?

A

Changes in the relative level of seas and oceans caused by the GRAVITATIONAL PULL of the moon and to lesser extent, the sun.

The difference between the high tide and the low tide.

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15
Q

Define neap tides?

Draw a neap tide:

A

Neap tides take place when the sun and moon are at right angles to each other, cancelling out the gravitational pull.
TIDAL BULDGE SMALL TO MOONS

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16
Q

Define spring tides?

A

Spring tides take place when the sun and moon align, causing the gravitational pull to be amplified
Higher high tides can be seen.

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17
Q

What are High Energy coastlines?

A

Environments with high wave power, rocky beaches and EROSIONAL features as erosion exceeds deposition eg: wave cut platforms, headlands.
EG: The West Coast of the British Isles

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18
Q

What are Low Energy coastlines?

A

Environments with low wave power, sandy beaches, and DEPOSITIONAL features as deposition exceeds erosion eg: spit, tombolo.
EG: The East Coast of the British Isles (small fetch across the North Sea)

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19
Q

Define wave refraction?

A

The DISTORTION of wave fronts as they approach the shoreline.

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20
Q

What causes wave refraction and what happens to wave energy?

A
  1. Shallow waters around hard rock headlands leading to friction.
  2. High and low energy stretches and DISCORDANT coastlines.
    - Energy is COCENTRATED at headlands (chalk and limestone) and DISSIPATED at bays (clay and sands).
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21
Q

Define wave frequency?

A

The number of consecutive waves per minute.

22
Q

Refraction definition?

A

The distortion of waves as they approach an IRREGULAR/ UNEVEN coastline.
Reach headlands first and concentrate energy, refracts and bends around bays.

23
Q

Describe the relationship between global wind patters and wave energy?

A

South- westerlies, or Prevailing Winds that travel across the Atlantic ocean have a large fetch and have a lot of wave energy = high energy coastline
EG: Plymouth
North- east winds that travel across the shorter fetch of the North Sea have less wave energy = low energy coastline
EG: the Sunderland Coast

24
Q

Define drift aligned beach?

A
  • Where the waves break at an angle to the coast
  • Swash occurs at an angle and backwash runs back perpendicular (straight) to the beach. (LSD)- due to gravity.

Creates narrow, thin beaches.

25
Q

Define swash aligned beach?

A
  • Waves break in line/ parallel to the coast
  • Influenced by constructive waves

Creates smoothly curved, concave beaches.

26
Q

Describe the placement of the different costal system zones ?

A

Top line- Backshore, Foreshore, Inshore, Offshore
(In foreshore and Inshore) = swash zone, surf zone,
breaker zone
Within all - Nearshore Zone

27
Q

Define storm surge?

A

The pushing of water towards the coast at an abnormally high level- takes place due to:
1. Low pressure 2. High tide.

28
Q

Define ocean current?

A

The large scale movement of water within the oceans.

29
Q

Define tides?

A

The rise and fall of sea levels due to the combined gravitational pull from the sun and moon.

30
Q

What are the two most significant ideas relating to tides?

A
  1. They can GENERATE OCEAN CURRENTS that influence the direction and scale of costal sediment movement.
    2, Their regular rise and fall can be used to create RENEWABLE ENERGY eg: Swansea Bay Tidal Lagoon in Wales.
31
Q

What three factors drive currents?

A
  1. The rise and fall of the tides- usually takes place more locally in bays and estuaries.
  2. Wind
  3. Thermohaline circulation- Variations in the density of water due to differences in heat and salinity
    Drives warm water from equator and cold water from poles around the earth.
32
Q

What three ways do currents affect us?

A

Search and rescue personnel can predict where people may have drifted.
Commercial shipping
Safely undock and sock ships.

33
Q

What are the weathering processes ( m, c, b)?

A

Mechanical:
Freeze- thaw, salt crystallisation, exfoliation, wetting and drying.
Chemical:
Solution, Oxidation- IRON, Carbonation- CARBONIC ACID
Biological:
Tree roots, organisms eg: puffins nesting, limpets.

34
Q

What are the erosional processes?

A

Hydraulic action
Wave quarrying
Attrition
Abrasion
Solution
Cavitation - waves break and throw sediment at rock.
Corrosion- air bubbles trapped in water are compressed.

35
Q

Define mass movement?

4 reasons why mass movement takes place?

A

The movement of regolith downhill mainly due to gravity.

  1. Gradient
  2. Water - saturation increases weight and decreases stability.
  3. Human influence- roads, railway lines.
  4. Vegetation- roots bind together to make more stable.
36
Q

What are the mass movement processes?

A 
Rockfall 
Landslide
Runoff 
Mudflow
Land slump
Solifluction / soil creep- very slow, trees and poles bend towards direction of movement.
37
Q

Discuss factors affecting Coastal Erosion?

Will Lucy Get Pounds? Sometimes Coins

A

Waves- strength and type
Lithology- granite erodes slower than clays
Geology- cracks and joints in rocks can be exploited
Presence/ absence of beach- absorb wave energy
Sub-Ariel processes- weathering and mass movement weaken cliffs.
Coastal management- Groynes

38
Q

Define Concordant coastline?

A

Layers of alternating hard and soft rock run parallel to the coast = COVES = LULWORTH COVE, Dorset.

39
Q

Define Discordant coastline?

A

Layers of alternating hard and soft rock run at right angles to the coast= HEADLANDS AND BAYS- softer rock (clay) erodes faster than hard rock (granite). = SWANAGE BAY and DURLSTON HEAD.

40
Q

Define wave- cut platform?

A

A gently sloping rock ledge that extends from the high water mark due to cliff erosion.

41
Q

Wave cut- platform formation?

A
  1. Over time cliffs retreat due to the action of waves and weathering.
  2. Wave energy and sub-ariel processes will cause a NOTCH to form within the cliff face.
  3. The notch acts as a point of weakness for weathering to exploit, leading to the formation of a CAVE.
  4. Due to the weight of the cave and no support it becomes unstable and collapses.
  5. Sediment is removed by backwash and acts as an input into local sediment cell, process repeats.
    eg: FLAMBOROGH HEAD on Holderness Coast
42
Q

Formation of Crack- Cave - Arch- Stack- Stump

A
  1. Cracks form at the base of the headland within the foreshore zone- H.A= pressurises air
  2. Cracks develop into wave cut notches- HA, wave quarrying turns them into caves.
  3. When two caves align through formations of wave cut platforms an arch is formed. eg: DURDLE DOOR
  4. When an arch collapses it forms a stack. Wave refraction of destructive waves concentrates energy at stack.
  5. Further eroded by attrition= stump. Sediment transported through LSD to sink eg: tombolo
43
Q

Erosional Landforms- Beaches

A
  • A store in the coastal system
    -Shingle beaches- steep, narrow, large particles
    -Sand beaches- flat, wide, small particles.
    Distinctive features of beaches?
    RIDGES- raised areas of sand within the foreshore
    RUNNELS- lowered areas of sand within the fsz
    BERMS- ridges of sand and pebbles (1-2m high) found at high water mark.
    CUSPS- crescent shaped indentations in fsz
44
Q

Erosional Landforms- Spit

A

Spits are long, narrow features made out of sand and shingle that have one end attached to the shore (proximal) and the other extending to the sea (distal)

  • Form on drift aligned beaches
  • Sediment is moved along the shore by LSD, however a change in direction eg: estuary, leads to spit.
  • If prevailing wind direction changes= recurved end
  • Multiple recurved ends = a COMPUND SPIT+ areas behind spit that is sheltered= SALT MARSHES.
45
Q

Erosional Landforms: Tombolo and Bars

A

Bars are formed when a spit joins two headlands together, a lagoon forms behind the bar- sediment sink and can absorb wave energy.
(Offshore Bars) -partly submerged, form as sediment moves towards the coast eg: Slapton Sands, Devon.

Tombolo’s form when a spit attaches to a small, offshore Island.

46
Q

Define Barrier Island?

A

A long, thin island of sediment that runs PARALLEL to the coast and is detached from it.
Either was once a bar that was breeched and eroded or from last ice age as flooded water transported sediment to shallower waters.
An extension of a spit- vegetation stabilises the form in the offshore zone.

47
Q

What factors do sand dunes need to begin?

CASE STUDY: Sefton Coast Dunes - 37% of all rare plants in NW of England

A
  1. Shallow beach gradient to allow good sediment transport.
  2. Persistent onshore winds to dry and move sediment.
  3. Largely sandy beaches with small sand particles.
48
Q

Process of Sand Dune formation?

A
  1. Embryo- obstruction, high pH (alkaline sea water), unstable conditions, less than 1m
  2. Foredunes- marram and Lyme colonise (halophytes and xerophytes) - stabilise, increase height- 5m.
  3. Yellow dunes- plants die and decay adding humus to the dunes, more stable- TRAPS NTNTS, WATER.
  4. Grey Dune- 100% vegetation cover, more stable= more stable plants eg: BRAMBLES.
  5. Dune slack- water table reaches surface, creeping willow and cotton grass.
  6. Mature dune- plant succession through CLIMAX VEG -ash and birch tree. = PSAMMOSERE
49
Q

What can be stated about the system of a sand dune at the mature dunes?

A

The environment and vegetation are in dynamic equilibrium.

50
Q

What are threats to salt marshes/ sand dunes?

A

HUMAN NATURAL
Industrial pollution (oil) Sea levels may rise too quick to
adjust
Agricultural fertilisers Storm events create large
off to ecosystems wave energy

Dredging removes sediment Changing temps
available. and rainfall can affect veg tolerance

51
Q

Process of salt marsh formation?

CASE STUDY: Key Haven Marshes at Hurst Castle Spit

A
  1. Mud and silt accumulates within foreshore zone, usually behind a sheltered area eg: spit.
    Here flocculation also occurs.
  2. Halophytes colonise such as SPARTINA grass and accumulate more mud in their roots.
  3. This stabilises conditions and more plants colonise such as marram grass and sea lavender =SLOW CURRENT AND ADD HUMUS.
  4. Rises higher forming creek systems to allow tides to enter and leave .
  5. Develop more, moisture tolerant plants such as ash and oak complete vegetation succession- halosere.
52
Q

Factors needed for salt marsh production?

A

Sheltered estuary areas behind spits, here wave energy is low
Intertidal mudflats = FLOCCULATION - salt water and clay particles mix, causing heavier silt to then be deposited.

Y12 A Level Geography- Leathers (5 decks)

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