Tides

1. Tides-What are they?

Mont Saint Michel France

Tides

• Tides are the regular rise and fall of ocean water levels.

http://www.youtube.com/watch?v=__UEYLfLL3c

2. What causes tides to occur?

• Tides are due to the gravity of the moon trying to pull the water on Earth closer to it (the moon).

What causes tides to occur?• The sun also pulls on the water, but it is

farther away, so it doesn’t have as much as an effect.

Gravitational Pull

• Gravitational pull depends on the mass of the object and its distance from Earth

What would happen to our high tides if the moon were more

massive (bigger)?

Tides would be higher because the moon would

have a greater gravitational pull on them

What would happen to our tides if the moon were further away?

• Tides would be smaller because of less gravitational pull

Earth rotates every 24 hours, which means that the places on Earth

where high tide and low tide occur are always changing.

http://www.astro.umass.edu/~arny/images/tidemov.gif

Watch the tide change in Africa

https://www.youtube.com/watch?v=gleTUvSjWjA

High Tide to Low Tide takes about 6 ¼ hours

• Knowing this will help you set up your beach chair in the right place!http://www.youtube.com/watch_popup?v=Z0qGvC3vqaA(fishing under ice at low tide)

3. Spring Tide

• When the Earth, Sun, and Moon are in a straight line (new moon and full moon) their gravitational force is combined and you have extra high and extra low tides called “Spring Tides”

4. Neap Tides

• When the Sun, Earth, and Moon are at a right angle (1st and 3rd Quarter) the gravitational pull is not as strong and tides are not as high or low as normal, this is called a “Neap Tide”.

Review Questions

If low tide is at 9am, when will high tide happen?

• Add 6 ¼ hours (6 hours and 15 minutes)

• 3:15pm

If high tide is at 8pm, when would the next high tide occur?

• Add 6 ¼ hours to get to low tide

• Then add another 6 ¼ hours to get back to high tide.

• 8:30am

Which diagram produces the highest tides? Explain

• B; Because the moon is in a new moon phase and the moon and sun’s gravitational pull are combined.

A B

If the moon were closer, what would be the effect on our tides?

• Higher tides because a closer moon would have more gravitational pull

Life as We Knew It

• Summary: A family’s experience with what would happen to our lives on Earth if the moon were hit by a meteorite and pushed closer to Earth.

If the moon were larger, what would be the effect on our tides?

• Higher tides because a larger moon would have a greater gravitational pull.