Tides In addition to seasons and moon phases, students need to know the effects resulting from cyclical movements of the Sun, Earth, and Moon as they relate to tides. Students will be able to relate the position of the Moon and Sun to their effect on ocean tides on Earth.

On the beach…

What are tides and what causes them? Tides are the rise and fall of the ocean water, due to the gravitational interaction between the sun, moon and Earth. The moon’s gravitational pull, more than the sun’s, causes the oceans to bulge and the Earth rotates through those tidal bulges.

Two Kinds of Tides: Neap Tides & Spring Tides Both kinds of tides occur twice a month, depending on the alignment of the sun, moon and earth or during certain phases of the moon.

Neap Tides Occur when the moon is in the first and third quarter phases when its position is at right angles to that of the sun. So the sun and moon play a little celestial tug of war. Of course, the moon always wins, and the tides obediently follow, but the sun does weaken the moon's pull, and the range of these tides is a great deal less than usual. These tides are what we call Neap Tides.

Neap tide

Spring Tides Occur during the New moon and Full moon phases, when the earth, sun and moon are in line. In this case, the sun actually helps the moon, and adds to the moon's ability to pull the tides. The range is greater with the tides rising higher and falling lower than usual. These are what we call Spring Tides. The word Spring comes from the anglosaxon word, springen, which means to leap. These tides are also referred to as Leap Tides.

Spring tide

?Questions? What causes tides?

How often do Spring tides and Neap tides each occur?

Explain the alignment of the sun, moon and Earth during spring tides.

Explain the alignment of the sun, moon and Earth during neap tides.