Chapt 9_Tides(1).doc - OCE-2001 Exam 3 Study packet Chapter...

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OCE-2001 Exam 3 Study packet 1 Chapter 9 – Tides Rhythmic rise and fall of sea level Very long and regular shallow-water waves May be 1000’s of kilometers and up to 15m high (50ft) Caused by gravitational attraction of Sun, Moon, and Earth Tides govern nautical activity Predictable Earliest tide records – 450 B.C. Important for fishing, navigation, storm preparation etc. Isaac Newton (late 1600’s) developed laws of gravitation Better understanding of how tides worked Cause of tides – combination of gravity and motion between Earth, Sun and Moon Tide-generating Forces Ocean tides are caused by gravitational attractions of the sun and moon acting on the ocean along with centripetal force. Bodies rotate around a center of mass - Barycenter (gravitational balance point) between Moon and Earth Mutual orbit due to gravity and motion The entire Earth follows the motion of center of gravity – barycenter Located 1600 k beneath the crust NOT between both due to Earth’s much larger size and mass Gravitational forces Newton’s Law of Universal Gravity - Every particle attracts every other particle Gravitational force proportional to product of masses Mass increases force increases Inversely proportional to square of separation distance Distance increases force decreases Centripetal force Center-seeking force - force equal at all points, pulling inward Resultant Forces Particles require identical centripetal forces to remain in motion Differences between centripetal and gravitational forces Different than the supplied gravitational force Near moon, gravitational forces are greater Away from moon, centripetal forces are greater horizontal components resulting in “ bulges Maximum value of force at 45 o “latitude” relative to the “equator” “Equator” of the zenith and nadir – no force Small horizontal forces push seawater into two bulges Lunar Tidal Bulges Opposite sides of Earth One bulge faces Moon Other bulge opposite side Earth Ideal Earth covered by ocean Not considering differences in ocean depth, coastline topography etc. Two tidal bulges Two high tides, 12 hours apart High tide - flood tide seawater moves on shore Low tide - ebb tide seawater moves offshore
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OCE-2001 Exam 3 Study packet 2 Lunar Day - How to predict tides : Moon orbits Earth Earth spins around relative to the moon in 24 hours and 50 minutes - lunar day high tides (most locations) are 12 hours and 25 minutes apart tide time alters by 50 minutes per day at any given location depends also on the different coastal currents in operation.
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  • Spring '14
  • Neap Tides, Tide,  Cause of tides,  Bodies

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