Get into groups of four. In your group you are going to have a discussions. With your partners you are going to answer these questions.

-How long does it take the earth to rotate on its axis once?

-How long does it take for the moon to orbit the earth once?

-How long does it take the earth to orbit the sun once?

-What are ocean tides?

-What causes ocean tides?

-What are seasons?

-What causes seasons?

-Are seasons the same in all parts of the earth?

We will discuss these answers in class. Make sure that you have your answers and the real answers written in your sketchbook.

The ocean tides are caused by the gravitational force of the moon. (Need Image)

The ocean rises and falls as the earth faces the moon. Since the earth is rotating completely around every 24 hours, the part of the earth that is currently facing the moon is at high tide. Also the part of the earth that is facing the opposite direction of the moon is also at high tide. If all things were even, there would be two high tides and two low tides every day.

When the sun and moon are aligned the tides are at their most extreme. This is called a spring tide. When the sun and moon are at a 90 degree angle the tides are less extreme. This is called a neap tide. (Needs Image)

Phases of the Moon (Needs Image)

Tides also work differently depending where you are in the world (Needs Image)

If the Earth were a perfect sphere without large continents, all areas on the planet would experience two equally proportioned high and low tides every lunar day. The large continents on the planet, however, block the westward passage of the tidal bulges as the Earth rotates. Unable to move freely around the globe, these tides establish complex patterns within each ocean basin that often differ greatly from tidal patterns of adjacent ocean basins or other regions of the same ocean basin (Sumich, J.L., 1996).

Semidiurnal Tides (Needs Image)

Mixed Tides (Needs Image)

Diurnal Tides (Needs Image)

Diurnal tide cycle (upper left). An area has a diurnal tidal cycle if it experiences one high and one low tide every lunar day. Many areas in the Gulf of Mexico experience these types of tides.

Semidiurnal tide cycle (upper right). An area has a semidiurnal tidal cycle if it experiences two high and two low tides of approximately equal size every lunar day. Many areas on the eastern coast of North America experience these tidal cycles.

Mixed Semidiurnal tide cycle (lower middle). An area has a mixed semidiurnal tidal cycle if it experiences two high and two low tides of different size every lunar day. Many areas on the western coast of North America experience these tidal cycles.

Seasons! (Needs Image)