Tides are the rising and falling of the sea. During high tide, the water is deeper and comes further onto the beach. Another name for high tide is flood tide. During low tide, the water is more shallow and does not come as far onto the beach. Another name for low tide is ebb tide.

Photo from Daniel Cornwall at Alaskan Librarian.

Tides are created because the Earth and the moon are attracted to each other, just like magnets are attracted to each other. The moon tries to pull at anything on the Earth to bring it closer. But, the Earth is able to hold onto everything except the water. Since the water is always moving, the Earth cannot hold onto it, and the moon is able to pull at it.

As you have already learned, the Earth makes one complete turn every 24 hours. The side of the Earth that is facing the moon is where it is high tide. That is where the moon is pulling at the water. Since the Earth is spinning, the area that the moon is pulling at changes. That is why the tides change. If you are at the beach, and the moon is pulling on the ocean there, it will be high tide. If the moon is pulling at the ocean somewhere else, then it will be low tide at the beach where you are.

We know that the water nearest to the moon forms a bulge because of the pull from the moon. But, the water also forms a bulge on the other side of the Earth. Click here to see a simple experiment that explains why the Earth forms a second bulge on the other side.

To see how the moon affects the tides, click here.

Each day, there are two high tides and two low tides. The ocean is constantly moving from high tide to low tide, and then back to high tide. There is about 12 hours and 25 minutes between the two high tides.

Since the moon moves around the Earth, it is not always in the same place at the same time each day. So, each day, the times for high and low tides change by 50 minutes. To see a tide table, click here.

The sun also pulls at the Earth, but not as strong as the moon. There are two times when you are able to see the pull from the sun. When the sun, Earth and moon are in a straight line, this causes a spring tide.

Photo taken from Our Oceans.

The spring tides create high tides that are really high and low tides that are really low.

When the sun and the moon are at a right angle to each other, this is called a neap tide.

Photo taken from Our Oceans.

The neap tides create high tides that are very low and low tides that are very high.