What causes the Tides?

6th Grade

Ms. Bridgeland

High Tide vs. Low Tide

High Tide vs. Low Tide

What is a good definition of a TIDE?

• The periodic rise and fall of the water level in the oceans

What are causes of tides?

• Largest force = the gravitational forces from both the sun and the moon

• Other forces: – Wind– Earthquakes– Plate tectonics

Sir Isaac Newton to the Rescue!

• Newton’s Universal Gravitation Theory helped to explain how the gravity of the moon (and the sun) were related to tides.

The moon’s gravity pulls on everything on the Earth

• The pull on liquids is more noticeable than on solids because liquids move more easily than solids

The moon’s pull is strongest on the part of the Earth directly facing the moon

Earth’s rotation through tidal bulges causes most coastlines to experience two high tides and two low tides every 25 hours.

High Tide

• The part of the ocean directly facing the moon bulges toward the moon

• There is a bulge on the opposite side because the water farthest from the moon is pulled toward the moon less strongly than are other parts of Earth

Low Tide

• The places between the bulges of the high tide

• High tide bulges take water away from low tide areas

Spring Tide• During a full moon and new moon (when the

sun, earth, and moon are fully lined up) is the greatest difference between the heights of the high and low tides

• Highest high tide and lowest low tide

Neap Tide

• During the First Quarter and Third Quarter phases of the moon, the low and high tide do not have much of a difference from one another

Which is the Spring Tide, and which is the Neap Tide?