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Physical Geo A2 > 2.1. Wave, marine and sub-aerial processes > Flashcards

2.1. Wave, marine and sub-aerial processes Flashcards

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

2 Factors affecting the formation and size of a wave

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

What are the coastal zones? (3)

A
  1. Upper beach/backshore - backed by cliffs or sand dunes
  2. Foreshore - periodically exposed by tides
  3. 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
  1. Spilling breakers
  2. Plunging breakers
  3. 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
  1. Swash: forward movement of water up the beach
  2. Backwash: backward movement of water down the beach
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16
Q

Define constructive waves/swell waves (6)

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 (6)

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
  • Hgh 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
  1. Microtidal
  2. Mesotida: 2-4m
  3. Macrotidal - > 4m
21
Q

Define storm surges ( bão lao tới/ bão dâng lên)

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 (phân tán) along beaches located in:
  • Bays headland - converging waves, deeper waters (erosion)
  • Bay - diverging waves, shallower waters (deposition)
23
Q

4 types of erosion

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

5 Mass movements occur in coasts

A
  1. Salt weathering
  2. Freeze thaw weathering
  3. Biological weathering
  4. Solution weathering
  5. Slaking ( sự dập tắp )
25
Q

Salt weathering

A

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

26
Q

Freeze-thaw weathering

A

The process whereby water freezes, expands and degrades (giảm bớt) jointed rocks

27
Q

Biological weathering

A

Carried out by molluscs, sponges and sea urchins that burrow (đào bới)

28
Q

Solution weathering

A

The chemical weathering of calcium by acidic water

29
Q

Slaking ( làm dãn ra)

A

Materials disintegrate (phân tán) when exposed to water

30
Q

2 Energy factors affecting the rate of erosion

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

4 Material factors affecting the rate of erosion

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

Shore geometry factors affecting rate of erosion (3)

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

How is the sediment transport categorised? (2)

A

2 modes:

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

Define sediment cells (2)

A
  1. A section of the coastal zone here the sediment in the nearshore zone is moved by longshore drift
  2. Sediment cells have clear boundaries to define them such as headlands
35
Q

4 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 (4)

A
  1. Longshore drift
  2. saltation
  3. traction
  4. suspension
37
Q

Stores of a sediment cell (1-3) (2-1)

A
  1. temporary features - beaches, dunes and spits
  2. 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 (2)

A
  1. The concept states that any system (sediment cell for example) is the result of the inputs and processes that operate within it.
  2. Change to one of the inputs will cause a knock on effect on the process and resulting a change in the landforms.

e.g. increase in sediment => beach protetion => stabilisation of cliffs

Physical Geo A2 (8 decks)

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