Changing the level of the water

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Animation of Tidal Elevations in the Pacific
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Tides and Tsunamis

• Gravitational forces of moon and sun
• Equilibrium theory of Tides
• Dynamic theory of Tides (Reality) tidal
  patterns, confined basins
• Tsunamis generating forces
• Effects of tsunamis
• Warning systems, defenses

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Equilibrium Theory
Assumption
Tides are always in equilibrium with the
gravitational pull of the moon and Earth is a
planet covered in water.
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Gravity and centrifugal force(also called
tractive forces)
Equilibrium theory of tides
TogetherThe earth-moon system
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Tides The moon and the sun together
Spring tide
Neap tide
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semidiurnal

diurnal

composite
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Dynamic Theory
Needs to account for
Waves travel at a fixed waves speed There are
continents and rotation
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See video
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Tidal circulation

• Tides progress around basins, counterclockwise in
  S hemisphere and clockwise in N hemisphere

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Animation of Tidal Elevations in the Pacific
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Inertia continents cause the tidal motion on
the planet to differ markedly from the motion
of the forces.
We can calculate the water motion knowing the
forces, but we cannot say that the shape of the
water is the same as the shape of the forces.
For this reason tides must not be visualized as
bulges standing under the sun and moon. But
rather as very long waves over the sea forced by
the gravitational-centrifugal forces associated
with the moon-sun-earth system.
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Tides in confined basins

• Increase tidal range (the difference between high
  and low tide)
• Examples
• --Bay of Fundy, Canada
• --Northern Gulf of California, Mexico
• Tidal bores - wave of water moving upstream -
  result of high-tide crest entering confined inlet

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Bay of Fundy tides

• Extreme tides (10m or more) found where small
  marine basin adjoins large ocean
• Bay of Fundy, Nova Scotia
• Gulf of California
• (in most places, tides are 1 to a few meters in
  range)

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Tidal bore Severn River, England

• 2.452