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Chapter: Oceans

Table of Contents. Chapter: Oceans. Section 1: Ocean Water. Section 2: Ocean Currents and Climate. Section 3: Waves. Section 4: Life in the Oceans. Waves. 2. Whenever wind. blows across a body of water, friction pushes the water along with the wind. 3. A. Waves Caused by Wind.

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Chapter: Oceans

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  1. Table of Contents Chapter: Oceans Section 1: Ocean Water Section 2: Ocean Currents and Climate Section 3: Waves Section 4: Life in the Oceans

  2. Waves 2. Whenever wind blows across a body of water, friction pushes the water along with the wind. 3 A. Waves Caused by Wind 1. A wave in water is a rhythmic movement that carries energy through the water.

  3. Waves 3 A. Waves Caused by Wind 3. When wind speed is great enough, the water begins piling up, forming a wave.

  4. Waves 3 A. Waves Caused by Wind 4. Three things affect the height of a wave: the speed of the wind, the length of time the wind blows, and the distance over which the wind blows. 5. A fast wind that blows over a long distance for a long time creates huge waves.

  5. Waves 2. Wave height is the vertical distance between the crest and trough. The wavelength is the horizontal distance between the crests or troughs of two successive waves. 3 B. Parts of a Wave 1. Each wave has a crest, its highest point, and a trough, its lowest point.

  6. Waves 3 C. Wave Motion • When you observe an ocean wave, it looks as though the water is moving forward. But unless the wave is breaking onto shore, the water does not move forward. • Each molecule of water returns to its original position when a wave passes.

  7. Waves 3 C. Wave Motion 3. The molecule may be pushed forward by the next wave, but it will return to its original position when the wave passes. 4. Water molecules move in circular patterns within a wave.

  8. Waves 3 D. Breakers • A breaker is a collapsing wave. As a wave approaches a shore, it changes shape. • The bottom of a wave hits the shallow floor of the ocean and causes friction. This friction slows the bottom of the wave.

  9. Waves 3 D. Breakers 3. Because the top of the wave is not slowed by friction, it moves faster than the bottom. 4. However, the wave’s crest keeps moving at the same speed. Eventually the bottom of the wave moves too slowly to support the top of the wave. 5. The crest outruns the trough, and the wave collapses. Water tumbles over on itself, and the wave breaks onto the shore. After a wave crashes, gravity pulls the water back to sea.

  10. Waves 3 D. Breakers 6. Waves usually approach a shore at slight angles. This creates a longshore current of water, which runs parallel to the shore. 7. As a result, beach sediments are moved sideways. Longshore currents carry many metric tons of loose sediment from one beach to another.

  11. Waves 3 E. Tides 1. Throughout a day, the water level at the ocean’s edge changes. This rise and fall in sea level is called a tide. 2. A tide is a giant wave that can be thousands of kilometers long but only 1 m to 2 m high in the open ocean. 3. The difference between sea level at high tide and low tide is the tidal range.

  12. Waves 3 F. Causes of Tides • Tides are created by the gravitational attraction of Earth and the Moon and of Earth and the Sun. • Because the Moon is much closer to Earth, it has a stronger pull. The Moon’s gravity pulls at Earth, including its bodies of water. This forms two bulges of water.

  13. Waves 3 F. Causes of Tides 3. One bulge forms directly under the Moon and one on the opposite side of Earth. 4. The crests of these bulges are high tides. Between these bulges are troughs that create low tides.

  14. Waves 3 F. Causes of Tides 5. As Earth rotates, the bulges follow the Moon. This results in high tide happening around the world at different times.

  15. Waves 6. When the Moon, Earth, and Sun line up together, the high tides are higher and the low tides are lower than normal, creating spring tides. 3 F. Causes of Tides

  16. Waves 7. When the Sun, Earth, and Moon form a right angle, high tides are lower and low tides are higher than normal, creating neap tides. 3 F. Causes of Tides

  17. Waves 3 G. Wave Erosion • Waves can erode many meters of land in a single season. They wear away rock at the base of rocky shorelines. • Then overhanging rocks fall into the water, leaving a steep cliff.

  18. Waves 2. Large storms and hurricanes can produce waves that move much of the sand from the beach and can destroy large parts of some near shore islands. 3 H. Beach Erosion 1. Sandy shorelines also can be eroded by waves. 3. Longshore currents also can erode beaches.

  19. Section Check 3 Question 1 A rhythmic movement that carries energy through the water is called a _______. A. current B. tide C. upwelling D. wave

  20. Section Check 3 Question 2 Explain how the Moon affects ocean tides.

  21. Section Check 3 Question 3 Why is it NOT a good idea to build a home along the shore?

  22. Help To advance to the next item or next page click on any of the following keys: mouse, space bar, enter, down or forward arrow. Click on this icon to return to the table of contents Click on this icon to return to the previous slide Click on this icon to move to the next slide Click on this icon to open the resources file. Click on this icon to go to the end of the presentation.

  23. End of Chapter Summary File

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