Daily Changes in Tides

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Daily Changes in Tides
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• Tides-
• Caused by gravity from the Sun and the Moon
  pulling on and deforming large bodies of water

Historical Tide Gauge at Anchorage, Alaska
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High Tide vs. Low Tide

• Daily Changes in Tides
• High tides occur on the side of Earth closest to
  the Moon and the side opposite the Moon.
• High tides draw water away from the areas
  between, causing low tides to form.

Low tide near a dock
http//highered.mcgraw-hill.com/sites/0072482621/s
tudent_view0/animations.html
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For most places on Earth, high tides occur every
12 hours (twice a day).High and Low are about 6
hours apart.
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• Some places on Earth have only one high and one
  low tide everyday.
• High and low are about 12 hours apart.

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Monthly Tidal Changes
Spring Tides

• Tides with maximum daily tidal range
• Occur right after the new or full moon, about
  every 14 days.
• When the Sun, the Earth and the Moon are in
  alignment, and their gravities are working
  together to deform Earth.

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Monthly Tidal Changes
Neap Tides

• Tides with minimum daily tidal range
• Occur right after the 1st or 3rd quarter moon,
  about every 14 days
• Occur when the gravitational forces of the sun
  and the moon work against each other
• Occur halfway between spring tides

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Spring Tides High Tide at noon and midnight
Neap Tides High Tide at sunrise and sunset
http//earthsci.terc.edu/content/investigations/es
2406/es2406page03.cfm?chapter_noinvestigation
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The Bay of Fundy Nova Scotia, Canada
Upper picture High tide Lower picture Low
tide (just 6 hours later)
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High Tide
vs.
Low Tide
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Miajima Island, Japan