Tides Chapter 2.5

Those of you who have spent some time on the beach have probably noticed that the water level of the ocean does not stay the same all day long. Although waves continually wash the shore, the actual water level changes as the day passes.

It rises for a period of hours until it reaches its highest level, and then it begins to fall, or recede, to its lowest level. This daily rise and fall of the ocean waters is known as the tide. Its highest and lowest levels are, of course called high and low tides.

High Tide Low Tide

Waves 1. Height = high point to low point 2. Wavelength = crest to crest or trough to trough H E I G T

What causes tides? The dominant force that moves ocean water is the gravitational pull from both the sun and the moon The Moons pull is 2 times greater than that of the Sun…

How often is there a change in tides? Try to figure it out . . . High tides happen on opposite sides of the Earth. The Earth rotates once on its axis every 24 hours. SO… How many high tides would any one place in the ocean experience each day?

The times of tides changes by 50 minutes each day…Why? Answer The periodic rise and fall of the water level in the oceans and other large bodies of water happens . . . Twice each day! The times of tides changes by 50 minutes each day…Why?

Answer Not only is the earth rotating BUT the moon is revolving As earth rotates through its 24 hour day, the Moon makes progress in its 27.3-day journey around Earth. So in 24 hours, the Moon has moved enough so that it takes another 50 minutes for an specific point on Earth to catch up so that the Moon will again be directly “overhead”

High Tide The part of the ocean directly facing the moon, bulges towards the moon. There is a corresponding bulge on the opposite side of the Earth. These bulges are called high tide.

Low Tide When high tides occur, water is drawn away from the area between the high tides, which causes low tides to occur.

Spring Tide A tide with a large tidal range that occurs two times a month Caused by moon being in the new moon and full moon phase Sun, Earth, and the moon are aligned *What moon phase do you see on this slide? Full moon= earth between sun and moon

Spring Tide Because the sun and moon pull together, you get the highest high tides and the lowest low tides *What moon phase do you see on this slide? New moon= moon between sun and earth

*What moon phase do you see on this slide? Neap Tides A tide of minimum range that occurs during the first and third (last) quarters of the moon The sun, Earth, and moon form a 90 degree angle *What moon phase do you see on this slide? Third (Last) Quarter

Neap Tides Why are they weaker? The Sun’s and the moon’s pull are opposing *What moon phase do you see on this slide? First Quarter

Tidal Range The difference between the ocean level of the high and low tide

SPRING OR NEAP TIDE?

SPRING OR NEAP TIDE?

SPRING OR NEAP TIDE?

SPRING OR NEAP TIDE? Tides Video