Tides

LOW TIDE HIGH TIDE

Tides

• Tides are rises and falls in ocean water that cycle every 12.5 hours.– Rises for about 6 hours– Falls for about 6 hours

Why do you think this happens?

Tides• The force of gravity pulls the moon and

Earth (including the water on Earth’s surface) toward each other.

• Tides occur mainly because of differences in how much the moon pulls on different parts of the Earth.

Tides

• As the Earth rotates, the moon’s gravity pulls water toward a point on Earth’s surface closest to the moon.

• This causes a second high tide on the other side of the Earth.

Tides

• As Earth rotates, tides occur in a 25-hour cycle.

• The shape of bays, inlets, and the ocean floor can affect the flow of water, and cause tides to be irregular in some areas.

SPRING TIDES• Spring Tides occur whenever the Sun, Earth

and Moon are most closely in a line. Spring Tides normally happen two times a month, once during a New and once during a Full Moon. Spring Tides tend to be higher than normal high tides. SPRING TIDE = OLD ENGLISH word meaning “to jump.”

NEAP TIDES• Neap Tides happen when the Sun and Moon are

at right angles to each other. Neap Tides also happen twice a month during Quarter Moons. Neap Tides create lower than normal high tides.

Tides can be used to create electrical energy!

Checkpoint!

1. What objects create the force that gives Earth’s oceans tides?