1. Earth’s Tides Objectives: Define tides What causes tides
How often tides occur
Types of tides

2. Tides are the vertical movement of water, specifically the alternate rise (flood) and fall (ebb) of water in the ocean. This is mostly noticeable along continental shorelines.
Moon
Earth
Caused by:
The influence of the Moon’s gravitational force acting on the Earth’s oceans and the Earth (the rocky part).

3. Tides are more influenced by the gravitational effect of the Moon than they are by that of the Sun (the Moon's closeness to us outweighs by far the Sun's greater size).
Low Tide
Moon
Earth
High Tide
High Tide
So, as the Earth spins around its axis, how many high and low tides do we have a day?
Low Tide
Sun 2

4. Higher high tides and lower low tides
Spring Tides
The gravitational affects of the moon and sun combine to influence the flow of the oceans on Earth.
Moon
Moon
Moon
Earth
Phase of the moon?
Phase of the moon?
Phase of the moon?
New Moon
Sun
New Moon
Full Moon
Higher high tides and lower low tides

5. Lowest high tides and highest low tides
Neap Tides
The gravitational affects of the moon and sun fight each other with their influence on the flow of the oceans on Earth.
Phase of the moon?
Moon
Moon
Phase of the moon?
Third Quarter
Third Quarter
Earth
Phase of the moon?
Moon
Sun
First Quarter
Lowest high tides and highest low tides

6. Tidal Range:
The difference between high and low tide.

10. Review Q: What are tides?
Tide = the periodic rise and fall of the water level in the oceans and other large bodies of water.
Q: What are the dominant forces causing tides in ocean waters?
The gravitational forces from both the sun and the moon.

11. Review (cont’d)
Q: Which one (the sun or the moon) has a bigger effect on tides?
The moon

12. Review (cont’d)
Q: What is the difference in levels of ocean water at high tide and low tide called?
Tidal Range
Q: Tidal ranges vary greatly due to the combined forces of the _________ and the ________ on the Earth
Sun, moon

13. Review (cont’d)
Which eclipse??
Q: How are the sun, Earth, and moon situated so we experience a spring tide?
Sun, Earth, and the moon are aligned
Which eclipse??

14. Review (cont’d)
Q: How are the sun, Earth, and moon situated so we experience a neap tide?
The sun, Earth, and moon form a 90 degree angle

15. Earth’s Tides

16. Tides & Consequences
This little tidal behavior goes both ways! The Earth rises tides on the Moon.
The Earth "brakes" the Moon's rotation AND the braking is complete! Synchronous Rotation of the Moon and its orbital period! (27.3 days!)
We see a permanent "near" and "far side" of the Moon.
Moon also brakes the Earth's Rotation
The length of the "day" is increasing!
From fossil reef corals of about 4´108 years old - daily growth/annual growth  400 days/year ~ 22 hours a day!
Day is increasing about seconds/century.
Moon's orbit is growing because of all of this interaction.
Therefore, the day is getting longer, Moon looks smaller, and tides are weakening.