Tides What are they What are they caused

Tides What are they? What are they caused by? Are there different kinds of tides?

• 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 rise and fall of the ocean is known as the tide. Its highest and lowest levels are, of course called high and low tides.

High Tide Low Tide

Tides – What are they? • Tides are daily changes in the level of ocean water. • They are the periodic rise and fall of the water level in the oceans and other large bodies of water.

What causes tides? What moves ocean water? • Wind • Earthquakes • Plate tectonics • The dominant force that moves ocean water is the gravitational forces from both the sun and the moon.

What causes tides? • The gravity of the moon pulls on everything on the Earth. • The moon’s gravitational pull on liquids is much more noticeable than on solids. • Why? Because liquids move more easily than solids.

What causes tides? • How often tides occur and the difference in tidal levels depend on the position of the moon as it revolves around the Earth. • The moon’s pull is strongest on the part of the Earth directly facing the moon.

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.

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. • How many high tides would any one place in the ocean experience each day?

Answer • The periodic rise and fall of the water level in the oceans and other large bodies of water happens. . . • Twice each day!

Spring Tide • A tide with a large tidal range that occurs two times a month (new moon and full moon) • Sun, Earth, and the moon are aligned

Neap Tides • A tide of minimum range that occurs during the first and third quarters of the moon • The sun, Earth, and moon form a 90 degree angle