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Tides
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- changes in elevation of the ocean's surface- caused by gravitational forces (moon, sun)
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Two principal factors influence tides
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- gravitational attraction- centrifugal force- balance b/w these two forces creates tidal bulges
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Equilibrium Theory of Tides Assumptions (3)
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1) Earth is completely covered w/ water2) Water is in equilibrium w/ tide producing forces3) Earth turns beneath these tidal bulges freely
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Lunar tides
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- tidal day = 24 hours 50 min- moon moves from 28.5 N to 28.5 S in a month- tidal bulge follows the moon
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Solar Tides
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- account for 46% of moon tidal force- moves 23.5 N and S of equator in course of year
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Syzygy
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- when earth, sun, and moon are in a line- spring tides
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Perigee
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- moon is closest to the earth
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Apogee
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- moon is farthest from earth
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Perihelion
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Sun is closest to earth
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Aphelion
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Sun is farthest from earth
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Spring Tide
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- syzygy- during new and full moons- gravitational forces added together- especially high and low tides- large daily tidal range
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Neap Tide
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- sun and moon at right angles; quadrature- 1st and 3rd quarters of the moon- gravitational forces are offset- daily tidal range is least
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Factors affecting tidal patterns (3)
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- shape of the coastline- configuration of the ocean basin- water depth
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Barycenter
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- common center of mass that the moon and earth rotate around- located 1600km below Earth's surface- follows a smooth orbit around the sun
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Centripetal force
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- force required to keep planets in their orbits- is provided by the gravitational attraction between each of them and the sun
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