TIDES Flashcards

1
Q

how are waves classified

A

by their physical characteristics

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2
Q

what kind of force forms waves

A

disturbing force

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3
Q

whats a Restoring force

A

flattens water surface

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4
Q

whats the most useful measure of wave size

A

Wavelength

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5
Q

what is the disturbing and restoring force for tides

A

gravity

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6
Q

what are tides

A

forced shallow-water waves formed by spatial variations in gravity

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7
Q

what does ‘forced’ mean

A

they are never free of the forces that cause them e.g. continuous wind causes waves

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8
Q

whats the equilibrium theory and who proposed it

A

Pytheas
describes how tides are influenced by the gravitational pull of the Moon and Sun on Earth’s oceans
- describes tides on a planet uniformly covered by water

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9
Q

who formalised the idea of the equilibrium theory

A

Isaac Newton - 1687 book - gravitational model of tides

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10
Q

does The Moon or sun have a stronger influence on tides and why

A

moon
- despite the Sun’s larger size, the Moon is much closer to Earth

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11
Q

why doesn’t the moon revolve around the center of Earth

A

Earth is much bigger than the moon - so the common center (barycenter) of mass resides inside the planet

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12
Q

why do tides form

A

differences in gravitational forces across earths surface - results in 2 bulges of water – one on same side of the moon and one on the opposite side

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13
Q

3 forces that generate tides

A
  • Inertial movement - As Earth and the Moon orbit their common barycenter, inertia causes water on the side opposite the Moon to form a second bulge
  • Gravitational attraction - Moon’s gravity pulls on Earth’s oceans, creating a bulge of water on the side facing the Moon
  • Tractive forces - arise from the combination of both
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14
Q

2 complications when it comes to tides

A
  • tidal cycle = 24 hours 50 mins - Lunar day is longer than solar day
  • moon varies position in the sky throughout
    each month – why we can get higher high tides sometimes and lower high tides other times
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15
Q

whats a spring and neap tide

A

spring = sun and moon aligned
neap = sun and moon misaligned

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16
Q

what are Semi-diurnal and diurnal tides

A

Semi-diurnal = 2x high and low tides a day (most common)
Diurnal = 1x high tide and low tide a day

17
Q

whats The Dynamic Theory and who proposed it

A

Pierre-Simon Laplace
improvement on Equilibrium Theory by considering real-world complexities in how tides behave.

18
Q

what 3 things does the Dynamic Theory take into account

A
  • The speed of the long-wavelength tide wave in relatively shallow water
  • The presence of interfering continents
  • The circular movement or back-and-forth rocking of water in ocean basins
19
Q

whats a Tidal datum

A

the reference level to which tidal height is compared

20
Q

whats the mean sea level

A

the height of the ocean’s surface average over a few year’s time

21
Q

whats the tidal range

A

high-water to low-water height differences

22
Q

what is Amphidromic Circulation

A

areas of little to no tidal movement
- don’t develop in confined spaces (like small bays or narrow channels) - no room for the tidal waves to circulate

23
Q

what is a A tidal bore

A

a true tidal wave – tide come very fast in wave like motion

24
Q

how has tidal friction and forces influenced the earth

A
  • gradually slowing the Earth’s rotation by a few hundredths of a second per century
  • Tidal forces have locked the rotation of the moon to that of Earth, resulting in the same side of the moon always facing Earth
25
Q

can tides be predicted

A

yes - There are at least 140 tide-generating and tide-altering forces and factors
- Experience permits predication of tidal height to an accuracy of about 3 centimeters (1.2 inches) for years in advance

26
Q

Factors which can alter predicted tide times

A
  • Storm surge
  • Atmospherically induced seiching of the basin
  • Large scale resonances by a tsunami
  • Strong steady wind on-shore or offshore
27
Q

what are Meteorological tides

A

weather related alterations are sometimes called meteorological tides after their origin

28
Q

what can be used to study tides

A

satellites - variations in magnetic field

29
Q

how can Tidal waves provide electrical power

A

underwater turbines