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Oceanography > Waves - 8 > Flashcards

Waves - 8 Flashcards

1
Q

What are waves?

A

The undulatory motion of a water surface

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2
Q

What is a capillary wave?

A

A wave with a period less than 1/10th of a second

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3
Q

What is chop?

A

Waves with a period between 1 and 10 seconds

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4
Q

What are seiches?

A

Waves with a period between 10 minutes and 10 hours

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5
Q

What period do tsunamis have?

A

Between 10 and 60 minutes

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6
Q

What period do tides have?

A

12.4 hours to 24.8 hours

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7
Q

What period do internal waves have?

A

Anything from minutes to hours

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8
Q

What is celerity?

A

Velocity of the wave form, not the water

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9
Q

Why is speed an inappropriate measure?

A

It implies that there is a mass moving forward, however in a wave it is energy moving forward

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10
Q

For deep water waves, celerity =

A

wavelength/wave period

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11
Q

What is fetch?

A

The are of contact between the wind and the water

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12
Q

What does the term ‘seas’ refer to?

A

A term applied when the fetch has a chaotic jumble of new waves, which continue to grow until the sea is fully developed

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13
Q

What is wave interference?

A

The momentary interaction between waves as they pass through each other

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14
Q

What is constructive interference?

A

When two like portions of waves convince, creating an additive effect and larger waves

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15
Q

What is destructive interference?

A

When dislike portions of waves coincide, creating a subtractive process with smaller waves

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16
Q

What is a rogue wave?

A

An unusually large breaking wave composed of several large wave that momentarily merge

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17
Q

Why do longer waves travel faster than short waves?

A

Because speed increases as wave length increases

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18
Q

What is dispersion?

A

The sorting of waves by speed and wavelength as they leave the fetch area

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19
Q

What does dispersion generate?

A

Swell (long, low waves) that produce a regular up and down motion of the sea surface

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20
Q

The majority of waves on the surface are …

A

wind-generated

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21
Q

What controls size and type of wave?

A
  • Wind velocity
  • Wind duration
  • Fetch
  • Orignial state of the sea surface
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22
Q

What does the term ‘old seas’ mean?

A

Waves on the surface that are unrelated to current wave generation

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23
Q

When do fully developed seas occur?

A

When wave are as large as possible under current conditions

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24
Q

What is significant wave height?

A

The average wave height of the highest 1/3 of the waves present

25
Q

What is significant wave height good indicator for?

A

Potential wave damage as taller waves have the most eroding power

26
Q

How do water molecules in wave move?

A

In an orbital motion

  • upward and forward with the crest
  • downward and and back with the trough, slightly ahead of their original pattern
27
Q

What is mass transport and where is it significant?

A

The slight forward motion of the water … significant in shallow water as it can create nearshore currents

28
Q

What is wave base determined by in open water?

A

Internal friction and energy loss in the water

29
Q

What is wave based determined by in shallow water?

A

Interaction between the water and the sea bottom

30
Q

If water is deeper than the wave base, orbits are …

A

Circular

31
Q

If water is shallower than the wave base, orbits are …

A

Elliptical

32
Q

What are the three types of waves (based off water depth)?

A
  • Deep water wave
  • Intermediate water wave
  • Shallow water wave
33
Q

What is an intermediate wave?

A

When water depth is between 1/2 and 1/20 of the wavelength

34
Q

What is a shallow water wave?

A

When water depth is less than 1/20th of the wavelength

35
Q

What is wave steepness?

A

A ratio of wave height divided by wavelength (H/L)

36
Q

When does a wave become unstable?

A

When wave steepness is larger than or equal to 1/7

37
Q

When do waves break?

A

When the crest moves forward, whereas the base is half back by friction, causing the wave to increasingly lean forward and eventually collapse

38
Q

What are the 3 types of breakers?

A
  • Spilling breakers
  • Plunging breakers
  • Surging breakers
39
Q

What is a spilling breaker?

A

Waves with crests that continuously spill down the front of the wave, gradually depleting the waves energy

40
Q

What are plunging breakers?

A

Waves that collapse forward and release most of the waves energy at once as it moves across a steeper, narrow surf zone

41
Q

What are surging breakers?

A

Low, flat waves that do no break but smoothly rise and fall against a steep beach face … energy is reflected sea ward

42
Q

What is a storm surge?

A

A rise in sea level resulting from low atmospheric pressure associated with storms and the accumulation of water dragged shoreward by winds.

43
Q

When do storm surges create the most damage?

A

When superimposed on a spring high tide

44
Q

What are wave orthogonals or wave rays?

A

Imaginary lines drawn perpendicular to the wave crest, dividing the wave into a series of equal segments

45
Q

Where do orthogonals converge? What does this result in?

A

At headlands … wave energy is concentrated - larger, more erosive waves

46
Q

Where do orthogonals diverge?

A

In bays … smaller and weaker waves here

47
Q

What is a node?

A

An imaginary line across the surface about which the surface oscillates

48
Q

What is an antinode?

A

Where maximum displacement of the surface occurs as it oscillates

49
Q

Where is the node located in closed basins?

A

In the centre

50
Q

Where is the node located in open basins?

A

At the opening of the bay or estuary

51
Q

What are internal waves?

A

Waves generated due to density differences above and below the pycnocline

52
Q

How do internal waves compare to surface waves?

A
  • speed is slower
  • height can be greater
  • stability is greater (can’t collapse easily)
  • longer wavelength
  • greater period (minutes rather than seconds)
53
Q

What generates internal waves?

A

Disturbances to the pycnocline e.g. tides, flow of water masses past each other, storms, submarine landslides

54
Q

How long are tsunami wavelengths?

A

Up to 100 metres

55
Q

How fast can tsunamis travel?

A

Up to 760 km hr-1

56
Q

What type of waves are tsunamis?

A

Shallow to intermediate water waves

57
Q

How high are tsunamis?

A

Between 10-50 metres

58
Q

Where do tsunamis originate from

A
  • Earthquakes
  • Volcanic eruptions
  • Submarine landslides

Oceanography (13 decks)

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