Earth's Tides

Lesson 3

Earth's Tides

03

Lesson Goal:

Students can relate the positions of the moon and sun to their effect on ocean tides.

The following are pictures of the same place at different times of day. What differences do you observe?

Picture Set A

Picture Set B

Interactive Question

Interactive Question

High Tide cause by balanced forces.

High tide caused directly by the moon's gravity.

Tidal Bulges

• Tidal bulges stay in place as the Earth rotates beneth it.
• As the Earth rotates, different places on the planet's surface pass through the areas of the tidal bulges and have the change in water levels (tides).
• High Tide = tidal bulge
• Low tide = Between tidal bulges

High and Low Tide Change

Because the Earth is rotating at a different speed than the moon orbits the Earth, the tides shift a little each day.

Interactive Question

The Sun and Tides

Twice a month the Earth, Sun, and Moon are in alignment with one another. This happens during the New Moon and the Full Moon. Although farther away, the Sun's gravitational pull has an effect ont he tides during this time. The Sun's gravitational pull adds to the gravitational pull from the moon making the tidal bulges even larger. These are known as Spring TIdes. The high tides are higher and the low tides are lower. Spring as in "springing forth" and not the season of spring.

Info

Interactive Question

The Sun and Tides

Seven days after a Spring Tide (full or new moon), the sun and moon are at right angles to each other. This cancels out some of the moon's gravitational pull. The high tides are a little lower than normal tides and the low tides are a little higher than normal tides. These are known as Neap Tides. Neap tides occur at the first and third quarters of the moon when the moon appears "half full".

Info

Interactive Question

Spring TIdes = Strong Tides (bigger tidal bulge)Neap Tides = Weak Tides (snakker tidal bulge)

~Proximity Learning

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Summary

What causes tides? Put your answer in chat.

Thank You!

Is the whole world covered in water?

While most pictures that explain the tides show tidal bulges as shields of extra water that the Earth rotates through, this is a little misleading. Think about where you live. Does it have periods of the day where it is under water? Probably not. Instead it is the area of extra influence from the moon that we pass through which affects any water that is around you. In general though only the ocean is the body of water large enough to show a noticable tide.

Spring Tides

And the Great Lakes

In general lakes do not have tides because the entire lake is exposed to the moon's influence at the same time so there is nowhere to pull water from. However, the Great Lakes are an exception.

• During a spring tide the Great Lakes can experience a tidal shift (from low to high) of 5 centimeters.
• Most of the time this is not noticeable, because general weather causes some fluctation in water levels.
• Learn more here

Spring Tides

And the Great Lakes

In general lakes do not have tides because the entire lake is exposed to the moon's influence at the same time so there is nowhere to pull water from. However, the Great Lakes are an exception.

• During a spring tide the Great Lakes can experience a tidal shift (from low to high) of 5 centimeters.
• Most of the time this is not noticeable, because general weather causes some fluctation in water levels.
• Learn more here