Term
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Definition
| periodic, short term changes in the height of the ocean surface at a particular place, caused by a combination of the gravitational force of the moon and sun and the motion of Earth. |
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Term
| why are tidal waves shallow water waves? |
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Definition
| the wavelengths are so long that even over the abyssal plain the depth is less than half the wavelength. waves "feel" the frictional effects of the bottom, making them shallow water waves. |
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Definition
| never free from the forces that cause them |
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Term
| Are tidal waves forced waves? |
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Definition
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Term
| distance of the tide-generating object matters |
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Definition
| the forces that generate tides vary inversely with the cube of the distance from Earth's center to the center of the tide-generating object. The sun is 27 million times as massive as the moon, but the sun is about 387 times as far away as the moon. The sun's influence on tides is only 46% that of the moon's |
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Definition
| pulls the Earth and moon/sun toward each other |
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Term
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Definition
| the tendency of moving objects to continue in a straight line, keeps them apart (a.k.a. centrifugal force) |
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Term
| A planet orbits the sun in balance between gravity and inertia. |
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Definition
| If the planet is not moving, gravity will pull it into the sun. If the planet is moving, the inertia of the planet will keep it moving in a straight line. In a stable orbit, gravity and inertia together cause the planet to travel in a fixed path around the sun. |
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Term
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Definition
| the equilibrium theory of tides explains tides by examining the balance of and effects of forces that allow our planet to stay in orbit around the sun, or the moon to orbit Earth. because of its nearness to Earth, our moon has a greater influence on tides than the sun. |
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Definition
| the dynamic theory of tides takes into account depth, seabed contour, water's viscosity, and tide wave inertia. |
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Term
| What allows tides to be predicted years in advance? |
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Definition
| Together, the equilibrium and dynamic theories |
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Term
| The movement of the moon generates strong tractive forces "lunar tides" |
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Definition
| the moon does not revolve around the center of the Earth. The Earth-moon system revolves once a month (27.3 days) around the system's center of mass. The Earth is 81 times as massive as the moon, so the center of mass is located 1,023 miles inside the Earth |
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Term
| the movement of the moon generates strong tractive forces |
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Definition
| the moon's gravity attracts the ocean toward it. the motion of Earth around the center of mass of the Earth-moon system throws up a bulge on the side of Earth opposite the moon. The combination of the two effects creates two tidal bulges. |
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Term
| How do these bulges cause the rise and fall of tides? |
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Definition
| The Earth is spinning on its axis. Imagine an island on the equator: As the Earth turns eastward the island moves in and out of these bulges (the crest and trough of huge waves). As the island moves through the crest, it experiences high tide. As the island moves through the trough, it experiences low tide. |
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Term
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Definition
| a lunar day is longer than a solar day. a lunar day is the time that elapses between the time the moon is highest in the sky and the next time it is highest in the sky. in a 24 hour solar day, the moon moves eastward about 12.2 degrees. Earth must rotate another 12.2 degrees - 50 minutes - to again place the moon at the highest position overhead. A lunar day is therefore 24 hours 50 minutes long. Because Earth must turn an additional 50 minutes for the same tidal alignment, lunar tides usually arrive 50 minutes later each day. |
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Term
| tidal bulges and the moon |
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Definition
| the moon does not stay right over the equator. Each month it moves from a position as high as 28.5 degrees above the equator to 28.5 degrees below. The tidal bulges track the movement of the moon. |
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Term
| the sun also generates tractive forces "solar tides" |
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Definition
| Sun's gravity also affects the ocean's tides, but remember that the sun is much farther away than the moon. Smaller solar bulges follow the sun throughout the day... these are solar tides. The sun also moves above and below the equator by 23.5 degrees. The position of solar bulges changes much more slowly than lunar bulges because the Earth revolves around the sun only once a year. |
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Term
| the sun and moon cause spring tides |
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Definition
| If the Earth, moon, and sun are all in a line, the lunar and solar tides will be additive. Results in higher high tides and lower low tides called "spring tides" (springen: "to move quickly"). These tides occur at two-week intervals corresponding to the new and full moons. |
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Term
| The Sun and Moon cause Neap Tides |
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Definition
| If the moon, Earth, and sun form a right angle, the solar tide will diminish the lunar tide. Results in high tides that are not very high and low tides that are not very low... called neap tides (naepa, "hardly disturbed"). Arrive a week after the spring tide, also at two week intervals. |
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Term
| Distance from the tide-generating force matters |
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Definition
| Because the orbits of the moon and sun are ellpises, they are closer to the Earth at certain times. |
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Term
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Definition
| the moon's greatest distance from the Earth |
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Term
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Definition
| the moon's closest approach to the Earth |
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Definition
| the Earth's greatest distance from the sun |
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Definition
| the Earth's closest approach to the sun |
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Definition
| tides caused by inertia and gravitational force of the sun and moon |
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Definition
| Tidal crests (tidal bulges) move as forced waves, with their velocity determined by ocean depth... they behave as shallow water waves. The continents obstruct tidal crests, diverting, slowing, and otherwise altering their movements. The shape of basins impact patterns and heights of tides. Tides can be affected by other oscillations of the ocean surface (example: meteorological tides). For these reasons some coastlines experience semidiurnal, diurnal, and mixed tides. |
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Definition
| "twice daily" - two high tides and two low tides of nearly equal level each lunar day (Cape Cod) |
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Definition
| "daily" - one high and one low tide each lunar day (Gulf of Mexico) |
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Term
| mixed or semidiurnal mixed tides |
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Definition
| successive high tides and low tides are of significantly different heights throughout the cycle (Pacific coast). Blend of diurnal and semidiurnal tides. |
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Term
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Definition
| Water moving in a tide is under the influence of the Coriolis effect. It will move counterclockwise in the northern hemisphere around a node called a amphidromic point. The height of the tides increase with distance from an amphidromic point. |
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Term
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Definition
| the reference level to which tidal height is compared. Could be mean sea surface level, mean of the lowest tides (mixed tides), or the mean of all low tides (semidiurnal and diurnal tides) |
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Term
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Definition
| height difference between high-water and low-water height. largest tidal ranges occur at the edges of the largest ocean basins, especially in bays or inlets |
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Definition
| a high, often breaking wave generated by a tide crest that advances rapidly up an estuary or river (aka: tidal wave) |
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Term
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Definition
| if a basin is wide and symmetrical, a miniatureamphidromic system develops. If a basin is narrow and restricted, the tide wave crest cannot rotate around an amphidromic point. |
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Term
| Friction due to tides has gradually slowed Earth's rotation by a few hundredths of a second per century!! |
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Definition
| 350 million years ago, a year contained between 400 and 410 days, with each day being 22 hours long! |
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Term
| tidal patterns affect marine organisms |
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Definition
| organisms at the top of the intertidal zone deal with submergence and emergence / dessication. Organisms at the bottom of the intertidal deal with predation. |
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