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Chapter 11 S3

Chapter 11 S3

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Chapter 11 S3

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  1. Chapter 11 S3 Tides

  2. Ch 11 S3 Essential Questions • What causes tides? • What affects the heights of tides? • How are tides a source of energy?

  3. What Causes Tides? Tides are caused by the interaction of Earth, the moon, and the sun. Tides are the daily rise and fall of Earth’s waters on its coastlines.

  4. As a tide comes in, the level of water rises. High tide is when the water is highest. Then the tide flows out, flowing back toward the sea. Low tide is when the water reaches its lowest point. Gravity causes tides. Gravity is the force an object has that pulls other objects toward it.

  5. The moon’s gravity pulls on Earth’s waters. The moon’s gravity creates a bulge of water on the side of Earth closest to the moon. The water on the other side of Earth forms a second bulge. These are called tidal bulges. In places where there are tidal bulges, high tide occurs.

  6. In many places, there are two high tides and two low tides each day. In other places, one set of tides is so small that it seems like there is only one high tide and one low tide per day. Look on page 368 for question #5, #6, and #7

  7. Changes in the positions of Earth, the moon, and the sun affect the heights of the tides during a month. The sun’s gravity also affects Earth’s tides. The sun pulls the water on Earth’s surface toward it.

  8. When the sun and the moon are lined up, their gravities combine to produce a spring tide. A spring tide is a tide with the greatest difference between high tide and low tide.

  9. When the sun and the moon are at right angles to each other, the sun’s gravity pulls some water away from tidal bulges. The result is a neap tide. A neap tide is a tide with the least difference between high tide and low tide. Look on page 368 and 370 for questions #10 and #11

  10. The movement of huge amounts of water between high and low tide is a source of potential energy—energy that is stored and can be used.

  11. A lot of water moves between high and low tides. In some places, tidal power plants use the energy of tides to produce electricity. Look on page 370 for questions #13 & #14

  12. The energy of tides is used only in places where there is a big difference between high tide and low tide. There are very few places in the world with such a big difference.

  13. Ch 11 S3 Essential Questions • What causes tides? • What affects the heights of tides? • How are tides a source of energy?