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!