marine tide notes

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Tides are long period waves that move through the oceans as a result of the force exerted by the Sun and the Moon.

High tide occurs when the highest part of the wave, or crest, reaches a particular location.

In contrast, low tide occurs when the lower part of the wave, the trough, reaches a particular location.

Flood – Incoming tide along the coast and into the bays and estuaries

Ebb Currents – Outgoing tide

Strongest for both occur near or before high and low tides.Weakest currents occur between flood and ebb currents, called slack tides.

High Tide

Low Tide

Tidal Range

Flood Current

Ebb Current

The two celestial bodies that create tides are the sun and the moon

Tides are created by the gravitational pull between the two of them on the oceans of the earth

Tidal forces are based on the gravitational attractive force. With regard to tidal forces on the Earth, the distance between two objects usually is more critical than their masses.

The sun is 390 times further from the Earth than the moon.

Therefore the force is 59 million times less than the moon.

Therefore the sun’s force is about half that of the moon

The “near side” of the Earth is pulled by gravity due to the moon’s location. The inertia attempts to counter act this pull, but the gravity exceeds it, and, therefore, creates a “Bulge”.

The time it takes for a specific site on the earth to rotate from one point under the sun to the same point under the sun

24 hour day

The time it takes for a specific site on the Earth to rotate from an exact point under the moon to the same point under the moon

24 hour and 50 minute day The rotation of the earth needs to catch up to

the revolution of the moon, thus the extra 50 minutes

Because the Earth rotates through two tidal “bulges” every lunar day, coastal areas experience two high and two low tides every 24 hours and 50 minutes.

When the moon and the sun line up along the force line of pull, you have larger tides called, Spring Tides

When the moon and the sun are at a ninety degree angle to each other you have smaller tides called, Neap Tides