Ocean TidesOcean Tides

TidesTides• Changes in the level of ocean water Changes in the level of ocean water

during the course of a dayduring the course of a day• The ocean levels reaches a high and low The ocean levels reaches a high and low

level twice a daylevel twice a day

High and Low TidesHigh and Low Tides• High tide – Water is High tide – Water is

pushed up onto the shorepushed up onto the shore

• Low tide – 6 hours later Low tide – 6 hours later when water is pulled when water is pulled away from shoreaway from shore

What causes the tides?What causes the tides?• The pull of gravity between Earth, the moon, The pull of gravity between Earth, the moon,

and the sunand the sun

• Water in the oceans form a bulge on the side of Water in the oceans form a bulge on the side of Earth facing the moon.Earth facing the moon.

• While on the other side (away from the moon), While on the other side (away from the moon), a bulge forms because the water is thrown a bulge forms because the water is thrown outwardoutward

Causes of tidesCauses of tides• Water in the oceans tries to travel away Water in the oceans tries to travel away

from Earth’s orbit, but Earth’s gravity from Earth’s orbit, but Earth’s gravity keeps the water from flying off into keeps the water from flying off into space.space.

Spring TidesSpring Tides

• Spring tides occur during the full moon Spring tides occur during the full moon and the new moonand the new moon

• The high tides are very high and the low The high tides are very high and the low tides are very lowtides are very low

Neap TidesNeap Tides• Neap tides occur during first and third quarter moonsNeap tides occur during first and third quarter moons• There is a small difference between high and low tides.There is a small difference between high and low tides.• The high tides are not as high and the low tides are not The high tides are not as high and the low tides are not

as low.as low.