Tides are caused by the gravitational pull of the moon and to some extent the pull of the sun on the earth’s surface.
- The moon exerts a gravitational pull on the earth as it orbits around it. This has little effect on land which is solid and inflexible but it has a great effect on the ocean waters because water is liquid and can freely move about.
- The moon’s attraction causes the water of the earth from one region to pile up in on the side nearest the moon, i.e. at A. This being of water at A is an ordinary high tide. ‘
- At the same time, a counter-bulge occurs on the opposite side of the earth, resulting in a high tide at B. The cause for this high tide is to be found in the ‘centrifugal force’ that is set up by the rotation.
- Between these areas of high tides are areas of lower water at C and D since the moon’s pull draws water from these parts. These are areas of low tides.