2. Tides

3. Tides The rise and fall in sea level is called a tide. The rise and fall in sea level is called a tide. Caused by a giant wave. Caused by a giant wave. One low-tide/high-tide cycle takes about 12 hrs and 25 min. One low-tide/high-tide cycle takes about 12 hrs and 25 min.

4. Tides Tides are caused mainly by the gravitational pull of the moon. Tides are caused mainly by the gravitational pull of the moon.

5. Other Things That Influence Tides The gravitational pull of the sun. The gravitational pull of the sun. The distance of the sun and the moon from earth. The distance of the sun and the moon from earth. Winds and other factors. Winds and other factors.

6. Tides (cont’d.) Tides tend to be high where the gravitational force between the earth and the moon are the strongest, along with the opposite side of the earth where the centrifugal force is strongest. Tides tend to be high where the gravitational force between the earth and the moon are the strongest, along with the opposite side of the earth where the centrifugal force is strongest.

7. Tidal Range The difference in ocean level between high tide and low tide is called the tidal range

8. What is the Tidal Range? HT = 30 ftLT = 20 ft HT = 30 ftLT = 20 ft HT = 20 ftLT = 12 ft HT = 20 ftLT = 12 ft HT = 50 ftLT = 20 ft HT = 50 ftLT = 20 ft

9. Spring Tides Spring Tides have the greatest range Spring Tides have the greatest range –High Tides are higher and Low Tides are lower than normal Occurs during the new and full moons. Occurs during the new and full moons. Earth, Moon, and Sun are lined up Earth, Moon, and Sun are lined up

10. Neap Tides Neap Tides have the least amount of range. Neap Tides have the least amount of range. High Tides are lower and Low Tides are higher than normal High Tides are lower and Low Tides are higher than normal Occurs during the first and third quarters. Occurs during the first and third quarters. Earth, Moon, and Sun form right angles Earth, Moon, and Sun form right angles

11. Gravitational Effect of the Moon Two big bulges of water form on the Earth: Two big bulges of water form on the Earth: –one directly under the moon –another on the exact opposite side As the Earth spins, the bulges follow the moon. As the Earth spins, the bulges follow the moon.

16. Waves

17. Waves A Wave is a rhythmic movement that carries energy through matter or space. A Wave is a rhythmic movement that carries energy through matter or space. In oceans, waves move through seawater In oceans, waves move through seawater

18. Waves Caused by: Wind Wind Earthquakes Earthquakes Gravitational force of the Moon and Sun. Gravitational force of the Moon and Sun.

19. Waves On The Beach Most of the waves we see are at the beach. Most of the waves we see are at the beach.

20. Waves On The Beach As the wave travels in shallower water it slows and eventually falls forward as a breaker. As the wave travels in shallower water it slows and eventually falls forward as a breaker.

21. Wind or Storm Waves The most familiar waves are wind generated. The most familiar waves are wind generated.

22. Wind or Storm Waves Three things determine how large these waves can become. Three things determine how large these waves can become.

23. 1. Wind Speed This is the speed that the wind is blowing. This is the speed that the wind is blowing. This is usually measured in knots or nautical miles per hour. This is usually measured in knots or nautical miles per hour.

24. 2. Duration Duration refers to the time over which the wind blows. Duration refers to the time over which the wind blows. Winds in some areas may blow strong for long periods of time which can produce large waves. Winds in some areas may blow strong for long periods of time which can produce large waves.

25. 3. Fetch Fetch refers to the distance over which the wind blows. Fetch refers to the distance over which the wind blows. If a wind blows over thousands of miles the waves can get much larger than blowing across a small pond. If a wind blows over thousands of miles the waves can get much larger than blowing across a small pond.

26. Parts of a Wave Crest – highest point of a wave Crest – highest point of a wave Trough – lowest point of a wave Trough – lowest point of a wave Wave Height – vertical distance between the crest and the trough Wave Height – vertical distance between the crest and the trough Wavelength – horizontal distance between two crests or two troughs Wavelength – horizontal distance between two crests or two troughs

27. Wavelength Wave Height Crest Trough Still Water Wave Parts

28. Wave Movement When a wave passes through the ocean, individual water molecules move up and down but they do not move forward or backward. When a wave passes through the ocean, individual water molecules move up and down but they do not move forward or backward.

30. Wave Movement When a wave breaks against the shore, the crest outruns the trough and the crest collapses. When a wave breaks against the shore, the crest outruns the trough and the crest collapses. Called a breaker. Called a breaker. In this case, water does move forward and backward. In this case, water does move forward and backward.

32. Waves Caused by Wind When wind blows across a body of water, friction causes the water to move along with the wind. When wind blows across a body of water, friction causes the water to move along with the wind.

33. Waves Caused by Wind Wave Height depends on – Wave Height depends on – –Wind speed –Distance over which the wind blows –Length of time the wind blows

37. Tsunamis Tsunamis were once called Tidal waves, but they have nothing to do with the tides. Tsunamis were once called Tidal waves, but they have nothing to do with the tides.

38. Tsunamis They are produced by earthquakes and other seismic disturbances. That’s why they’re also called They are produced by earthquakes and other seismic disturbances. That’s why they’re also called seismic sea seismic sea waves. waves.

39. Tsunamis They are very long, fast moving waves. They are very long, fast moving waves. They can have wavelengths of 150 miles. They can have wavelengths of 150 miles. They can travel at over 450 miles per hour! As fast as a jet! They can travel at over 450 miles per hour! As fast as a jet!

40. The Danger of Tsunamis In the open ocean, a tsunami may only have a wave height of a few feet. In the open ocean, a tsunami may only have a wave height of a few feet.

41. The Danger of Tsunamis As the wave approaches shallow water, it builds to heights that can reach greater than 100 feet. As the wave approaches shallow water, it builds to heights that can reach greater than 100 feet.