Chapter 18 section iii


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Chapter 18 section iii

  1. 1. Ocean Waves and Tides
  2. 2. Wave – rhythmic movement that carries energy through matter or space
  3. 3. <ul><li>Waves look like hills and valleys; the crest is the highest point and the trough is the lowest point. </li></ul>
  4. 4. <ul><li>Wavelength is the horizontal distance between crests or troughs of two adjacent waves. </li></ul>
  5. 5. <ul><li>Wave height is the vertical distance between crest and trough. </li></ul>
  6. 6. <ul><li>As a wave passes, energy moves forward; the water molecules remain in about the same place. </li></ul>
  7. 7. <ul><li>A breaker is a collapsing wave. </li></ul>
  8. 8. <ul><li>Friction with the ocean bottom slows water at the bottom of the wave. </li></ul><ul><li>Eventually the top of the wave outruns the bottom and it collapses. </li></ul>
  9. 9. <ul><li>Wind forms waves as water piles up; wave height depends on wind speed, distance over which the wind blows, and the length of time the wind blows. </li></ul>
  10. 10. <ul><li>The rise and fall in sea level, called a tide, is caused by a giant wave produced by the gravitational pull of the Sun and the Moon </li></ul>
  11. 11. <ul><li>High tide – as the crest of this giant wave approaches shore, sea level appears to rise. </li></ul>
  12. 12. <ul><li>Low tide – later, as the trough of the wave approaches, sea level appears to drop. </li></ul>
  13. 13. <ul><li>The tidal range is the difference between the level of the ocean at high tide and low tide. </li></ul>
  14. 14. <ul><li>Tidal range can vary; most shorelines have tidal ranges between 1 and 2 m </li></ul><ul><li>Some have tidal ranges of only about 30 cm </li></ul><ul><li>Other places have tidal ranges as high as 15 m </li></ul>
  15. 15. <ul><li>When a rising tide enters a shallow, narrow river from a wide area of the sea, a wave called a tidal bore forms. </li></ul>
  16. 16. <ul><li>Tides are caused by the interactions of gravity in the Earth-Moon system. </li></ul>
  17. 17. <ul><li>When the Sun, Earth, and the Moon line up in certain ways, the Sun can strengthen or weaken the Moon’s effects. </li></ul><ul><li>Video </li></ul>
  18. 18. <ul><li>Springtides – higher high tides and lower low tides </li></ul><ul><li>Neap tides – lower high tides and higher low tides </li></ul>