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Tides & the moon

Tides & the moon. An overview…. If you have ever lived near or visited coastal areas, you will know that the level of the water rises and falls. These changes in water levels are called tides. Background….

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Tides & the moon

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  1. Tides & the moon

  2. An overview… If you have ever lived near or visited coastal areas, you will know that the level of the water rises and falls. These changes in water levels are called tides.

  3. Background… • Since the Earth rotates on its axis, the oceans bulge near the equator. Think of the way clothes fling out during spin cycle. • This action creates a bulge of water around Earth. • The oceans do the same thing, but are not flung completely off the Earth, because they are pulled back by the Earth’s gravity.

  4. Tides and the Moon • Tides are mostly caused by the gravitational pull of the moon. • Looking at the diagram to the right, there are always two points of high tides, and two points of low tide at all times. • This means that everywhere on Earth experiences two high tides and two lows tides in a day.

  5. Spring and Neap Tides: • SPRING TIDES • Occurs when the sun, Earth and moon are aligned. • However, because it is further away, its gravity has much less effect than the moon’s. • When the sun is on the same side of the Earth as the moon, or on the opposite side, higher tides than normal are experienced. • These are called SPRING TIDES. http://astro.unl.edu/naap/lps/animations/lps.swf

  6. Spring and Neap Tides: • NEAP TIDES • About seven days after a spring tide, the sun and the moon are no longer in the same line as the Earth. • The gravitational pull of the sun is at right angles to the gravitational pull of the moon. • The pull on the oceans of the sun and the moon are working against each other. • The high tides are not as high as usual. • The low tides are not as low as usual. • These ‘weaker’ tides are called NEAP TIDES. http://astro.unl.edu/naap/lps/animations/lps.swf

  7. QUICK CHECK: True or False 1. Tides are caused by the gravitation pull of Venus. • Earth experiences two high tides and two low tides. • Spring tides occur when the earth, moon and sun are aligned. • Neap tides occur when the Sun and Moon are aligned. • Weaker tides are caused by Neap Tides. • Stronger tides are caused by Spring Tides.

  8. Illustration of a Spring and Neap Tide: http://astro.unl.edu/naap/lps/animations/lps.swf

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