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Physical Geography A Level > 2.1. Wave, marine and sub-aerial processes > Flashcards

2.1. Wave, marine and sub-aerial processes Flashcards

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1
Q

Define wave

A

Waves are oscillation of the water surface

Water does not move forward

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2
Q

Define wave height/amplitude

A

The distance between the trough and the crest

Indication of wave energy

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3
Q

Define wavelength

A

The distance between successive crests or troughs

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4
Q

Define wave frequency

A

The number of waves per minute

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5
Q

Factors affecting the formation and size of a wave

A
  • Wind velocity
  • Depth of water
  • Fetch - the distance of open water the wave travels over
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6
Q

What are the coastal zones?

A
  • Upper beach/backshore - backed by cliffs or sand dunes
  • Foreshore - periodically exposed by tides
  • Offshore - covered by water
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7
Q

Define wave orbit

A

The shape of the wave. Varies between circular and elliptical. The orbit diameter decreases with depth (roughly equal to wavelength

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8
Q

Define wave base

A

When the orbit diameter decreases to a point there is no further movement related to wind energy

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9
Q

Define swell waves

A

Waves that are characterised by lower height and longer wavelength

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10
Q

Define wave breaker

A

Occurs when waves move further onshore, friction slows down the wave advance causing the shortening of wave

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11
Q

What are the 3 main types of breaker?

A
  • Spilling breakers
  • Plunging breakers
  • Surging breakers
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12
Q

What are spilling breakers?

A
  • are associated with gentle beach gradients and steep waves
  • are characterised by gradual peaking of the wave until the crest becomes unstable => gentle pilling forward of the crest
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13
Q

What are plunging breakers?

A
  • tend to occur on steeper beaches than spilling breakers with waves of intermediate steepness
  • distinguished by the shore ward face of the wave becoming vertical, curling over and plunging forward
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14
Q

What are surging breakers?

A
  • found on steep beaches with low steepness waves
  • the front face and crest of the wave remain relatively smooth
  • a large proportion of the wave energy is reflected at the beach
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15
Q

Define swash, backwash

A
  • Swash: forward movement of water up the beach
  • Backwash: backward movement of water down the beach
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16
Q

Define constructive waves/swell waves

A
  • Swash is greater than backwash
  • Large fetch
  • Long wave length
  • Low height
  • Found on low gradient beaches, low energy waves which deposit materials
  • Associated with spilling breakers
17
Q

Define destructive waves/stom waves

A
  • Backwash is greater than swash
  • Short fetch
  • Short wave length
  • High waves and frequency
  • Steeply sloping beaches
  • High energy waves which erodes
18
Q

Define tide

A

regular movements in the sea’s surface, caused by the gravitational pull of the moon and sun on the oceans

low spring tides occur just after a new moon

high spring tides occur after a full moon

19
Q

Define tidal range

A

The difference between high and low tide

20
Q

3 types of rides coastal areas can be classified into

A
  • Microtidal - <2m
  • Mesotidal - 2-4m
  • Macrotidal - over 4m
21
Q

Define storm surges

A
  • changes in the sea level caused by intense low pressure systems and high wind speeds
  • for every drop in air pressure of 10mb sea water is raised 10 cm
22
Q

Define wave refraction

A
  • is the change in speed and distortion of wave
  • waves are refracted and energy is concentrated around headlands and more dispersed along beaches located in bays
  • headland - converging waves, deeper waters (erosion)
  • bay - diverging waves, shallower waters (deposition)
23
Q

4 types of erosion

A
  • Hydraulic action: water breaks against cliff face, air trapped in cracks and joints => cavitation
  • Corrasion/Abrasion: process whereby breaking wave can hurl pebbles and shingle against a coast and thus abrading it
  • Attrition
  • Solution
24
Q

Mass movements occur in coasts

A
  • Salt weathering
  • Freeze thaw weathering
  • Biological weathering
  • Solution weathering
  • Slaking
25
Q

Salt weathering

A

the process by which sodium and magnesium compounds expand in joints and cracks thereby weakening rock structures

26
Q

Freeze-thaw weathering

A

The process whereby water freezes, expands and degrades jointed rocks

27
Q

Biological weathering

A

carried out by molluscs, sponges and sea urchins that burrow

28
Q

Solution weathering

A

the chemical weathering of calcium by acidic water

29
Q

Slaking

A

materials disintegrate when exposed to water

30
Q

Energy factors affecting the rate of erosion

A
  • Waves - wave steepness (steep destructive waves have more erosive power) and wave breaking point (where wave break at cliff base that cause maximum erosion)
  • Tides
  • Currents
  • Winds - onshore winds erode fine beach material, offshore winds erode dunes
31
Q

Material factors affecting the rate of erosion

A
  • Sediment supply - continual supply -> abrasion. oversupply can protect the coast
  • Beach/rock platform width - absorb wave energy
  • Rock resistance
  • Rock structure - well jointed
32
Q

Shore geometry factors affecting rate of erosion

A
  • Offshore topography - steep seabased creates higher and steeper waves; longshore bars cause waves to break offshore and lose enerfy
  • Orientation of coast - headlands with vertical cliffs tend to concentrate wave energy by refraction
  • Direction of fetch - longer the fetc, greater potential for erosion
33
Q

How is the sediment transport categorised?

A

2 modes:

  • Bedload - grains transported by bedload are moved through continuous traction or discontinuous saltation
  • Suspended load - grains are carried by turbulent flow and held up by water. Strong currents
34
Q

Define sediment cells

A

A section of the coastal zone here the sediment in the nearshore zone is moved by longshore drift

Sediment cells have clear boundaries to define them such as headlands

35
Q

Inputs to sediment cell

A

cliff erosion

offshore bars

river sediment

sand dunes

eroding depositional feature e.g. beach

36
Q

Transportation in a sediment cell

A

longshore drift

saltation/traction/suspension

37
Q

Stores of a sediment cell

A

temporary features - beaches, dunes and spits bars

permanent stores - estuary

38
Q

Notes about sediment cell

A

In reality it is unlikely that sediment cells are fully closed. With variations in wind directions and tidal currents, it is inevitable that some sediment is transferred between cells

39
Q

Define dynamic equilibrium

A

The concept states that any system (sediment cell for example) is the result of the inputs and processes that operate within it. Change to one of the inputs will cause a knock on effect on the process and a resulting change in the landforms. e.g. increase in sediment => beach protetion => stabilisation of cliffs

Physical Geography A Level (12 decks)

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