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TIDES !!!

TIDES !!!. Oceanography & Astronomy Earth Science Campbell Middle School. 6-3. So what causes tides?.

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TIDES !!!

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  1. TIDES !!! Oceanography & Astronomy Earth Science Campbell Middle School 6-3

  2. So what causes tides? The word "tides" is a basic term used to define the alternating rise and fall in sea level with respect to the land. Tides are produced by the gravitational attraction of the moon and the sun.

  3. But wait there’s more... To a much smaller extent, tides also occur in large lakes, the atmosphere, and even within the solid crust of the earth. Oklahoma rises and falls about 25 cm every day!

  4. High Tide Low Tide

  5. Tidal Bulges... LOW TIDE The liquid at point A is closer to the Moon and experiences a larger gravitational force than the Earth at point B or the ocean at point C. As a result it “bulges” out. But what about the bulge at point C…? HIGH TIDE HIGH TIDE LOW TIDE

  6. The moon at work... • Loosely, we may think of the bulge at point C as arising because the Earth is pulled away from the water on that side. The gravitational force exerted by the Moon at point B is larger than that exerted at point C.

  7. Right…BUT, Since the moon moves around the Earth, it is not always in the same place at the same time each day. So, each day, the times for high and low tides change by 50 minutes. So why are tides not exactly 12 hours apart? After all, it takes the earth 24 hours to rotate once.

  8. The timing of tidal events is related to the Earth's rotation and the revolution of the moon around the Earth. If the moon was stationary in space, the tidal cycle would be 24 hours long. However, the moon is in motion revolving around the Earth. One revolution takes about 27 days and adds about 50 minutes to the tidal cycle. As a result, the tidal period is 24 hours and 50 minutes in length.

  9. O.K. Let’s make it simple… • We get one high tide every 12 hours and 24 minutes .

  10. Spring & Neap Tides The Moon doesn’t work alone. Remember the Sun’s gravity also affects tides. SPRING TIDES The Sun & Moon may work together to produce higher than normal tides. NEAP TIDES The Sun & Moon may work against each other to produce lower than normal tides.

  11. NEAP TIDE SPRING TIDES

  12. Notice Spring & Neap tides only occur at certain phases of the moon.

  13. Uh…I need to see that picture again before I can answer that! I know the answer. Let’s move on. How often do Spring & Neap tides occur?

  14. There are over 400 stellar objects that exert a measurable pull on Earth’s oceans. Almost all are barely noticeable • In fact, the effect of the Sun on Earth’s tides is less than half that of the Moon.

  15. Why are ocean tides so different everywhere?"Because they depend on many factors including the geometry of your local coastline, and exactly where the Sun and Moon are located.

  16. Wanna know more? http://www.wiley.com/college/strahler/0471480533/animations/ch19_animations/animation3.html

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