GEOL 1033 Lecture Notes - Lecture 9: Geoid, Amphidromic Point, Declination
2 Mar 2017
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Periodic short term changes in the height of the ocean surface cause by the combination of the gravitational force of the moon and the sun and the motion of the earth. The main cause of tides is gravity of sun and moon acting on the ocean. But, forces vary as per the cube of distance from earth centre to centre of tide-generating object. Although the sun is huge it is so far away that its effect is ~1/2 that of the moon. Tides can be explained by two theories. Assumes that seafloor does not influence tides. Assumes that ocean responds instantly to the forces that affect it. Oceans surface is presumed to always be in equilibrium with the forces acting on it. Moon does not revolve around the centre of the earth. Earth-moon system revolves once a month (27. 3 days) around the s(cid:455)ste(cid:373)"s ce(cid:374)tre of (cid:373)ass. Moo(cid:374)"s gra(cid:448)it(cid:455) attracts the ocea(cid:374) surface to(cid:449)ards the (cid:373)oo(cid:374)
