TIDES The EBB and FLOW. Tides are affected by... Gravitational pull of the moon Gravitational pull...
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Transcript of TIDES The EBB and FLOW. Tides are affected by... Gravitational pull of the moon Gravitational pull...
TIDESThe EBB and FLOW
Tides are affected by . . .
• Gravitational pull of the moon
• Gravitational pull of the sun
• Centrifugal force of earth as it rotates
• Position of the sun & moon
• Angle of orbit of moon around earth
The Earth . . .•Makes one revolution around the sun per year
•Rotates on its axis about once per day
The Moon. . .•Revolves around the Earth at an angle 28.5o to the Earth’s equator
•Revolves once every 29.53 days
A TIDE is. . .•The alternate rising and falling of sea level as a result of the gravitational forces exerted on the Earth by the sun and moon
Flood Tide:
•A rising tide, moving inward
EbbTide:
•A falling tide, moving outward
Two competing forces produce tides . . .
•Gravitational between moon and Earth
•Centripetal between sun and Earth
Tidal Range:•The difference in height between successive high and low tides
Spring Tides-High Highs & Low Lows
• Spring tides-
during a new and full
moon, when earth, sun
& moon line up-
produces highest of high
and lowest of low tides
Neap TidesMedium Highs & Lows
• Neap tides- during the
1st & 3rd quarter moons,
when the earth, sun, and
moon are at right angles
(work against each other)
- Produces small high
and low tides.
Equatorial & Tropic Tide:
•Caused by angle and pull of moon at different positions to the Earth
Diurnal Tides:•One high and one low per day (one cycle)
DAY ONE DAY TWO
Semidiurnal Tides:•Two highs and two lows per day (two cycles)
DAY ONE DAY TWO
Tides are modified by
•Land•Weather•Coriolis force
Lunitidal Interval:•The lag in time between when you expect the tide and when it actually occurs
Tidal Bore:•A true tidal wave that moves up a river
Tide tables• The moon circles the earth every
24 hours 50 minutes. Tides occur 50 minutes later each day.
• Tides can be easily calculated in order to ensure safe navigation in areas like harbors
Put on your thinking cap!
What can happen to a ship if a seaman
fails to check his tide table?
It could get stuck at low tide!
How can knowing the time of high and low tide aid in fishing?
High tide carries fish in, they get trapped
at low tide.
At which tide level would you have the
best luck beachcombing?
LOW TIDE!
Why are tides important to
estuaries, bays, and marshes?
Tides bring fish in to spawn and for food.
Are tides a source of energy?
They have been harnessed to produce
energy in power plants!