Tide is defined as the periodic rise and fall of the oceans water level due to the pull of the gravity from the sun and the moon. Most ocean fronts experience two low tides and two high tides every day. The low tide is when the ocean water level is at its lowest and the high tide is when the water level is at its highest. Tides may not be visible in the deep ocean but are clearly visible along the coastline.
Although the rise and fall of the sea levels is caused by the gravitational force of both the sun and the moon, the moon has a greater influence on the tides. Although it is smaller than the sun, it is closer to the earth and its gravitational pull on the earth as pertains to tides is very evident in the rise and fall of the waters of the seas.
The tidal cycle is 24 hours and 52 minutes. As the earth rotates on its axis, and the moon revolves around the earth, different parts of the earth face the moon. The part facing the moon experiences high tide because of the gravitational pull of the moon on the earth which causes the water to bulge out. The side of the earth directly opposite the side facing the moon also experiences a similar bulge. As the earth is pulled towards the moon on one side, the water on the opposite side resists the pull causing it to bulge out and thus producing a high tide.
The different phases of the moon affect the intensity of the tides. During a full or a new moon which naturally come around twice every month, the high tides are higher and the low tides are lower. These are called spring tides and are caused by the combined gravitational pull of the sun and the moon. At this time, the sun, the earth and the moon are aligned.
If a full or new moon occurs and the moon is between the earth and the sun, proxigean tides occur. These are the highest and lowest tides that occur from the influence of the moon. At this time the moon is closest to the earth in its orbit. The occurrence is rare and can have devastating results at times.
When the moon is in its first and third quarter phase, neap tides occur. This means that the difference between the high and low tides is minimal. This happens because the sun and moon are at right angles to the earth. The gravitational pull from the moon is countered by the gravitational pull from the sun and the result is that the rise and fall of the water is not very significant.
Tides occur regularly on a daily basis even when the above extremities are not taking place. Each day there are two high and two low tides which occur with respect to the rotation of the earth on its axis, its revolution around the sun, and the revolution of the moon around the earth. The difference in the water levels is usually well noted in the different areas and according to the different phases of the moon, the unusual high and low tides can be anticipated.
Sources:
http://en.wikipedia.org/wiki/Tide
http://www.astonomycafe.net/
http://www.ehow.com/about_5038199_relationship-between-moon-phases-tides.html
