Low TideTides are the vertical rising and lowering of sea level, and are greatly controlled by the gravitational pull of the sun and moon. Although the sun has a stronger gravitational attraction than the moon, the moon's relative nearness to the earth makes its gravitational pull more than twice as effective as the sun's.

What Does the Pull of the Moon Do to the Oceans?
The gravitational pull of the moon creates two types of tides: high and low. A tidal bulge occurs in the oceans on the side of the earth nearest the moon; a second tidal bulge occurs on the far side of the earth. These bulges are high tides. The areas between the tidal bulges experience low tide. Usually two high and two low tides occur each 24 hours and 50 minutes.

How the Moon Creates Tides

Spring Tides And Neap Tides
When the moon is full or new, the gravitational pull of the moon and sun are combined. At these times,the high tides are very high and the low tides are very low. This is known as a spring high tide.

Spring Tide--Full Moon Spring Tides--New Moon
During the moon's quarterphases the sun and moon work at right angles, causing the bulges to cancel each other. The result is a smaller difference between high and low tides and is known as a neap tide.
Neap Tide

Tides Around The World
Tidal changes are different in various parts of the world. Near the equator, there is very little noticeable change because a large volume of water is spread out over a wide range.

The highest tides in the world are at the Bay of Fundy in Nova Scotia. The bay is very narrow, so water rushing in from the ocean can rise and fall up to 20 meters a day!

Try a Tide Activity!

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