Tide is defined as a ‘cyclical deformation of one astronomical body caused by the gravitational forces extended by the other’. Although there are many forms of tides demonstrable in the earth’s atmosphere, the periodical changes in the sea level is the most notable on the earth’s surface. In relation to the tides of the sea, the astronomical bodies, which exert the gravitational pull, would be the moon and the sun. Out of the two, the moon exerts a gravitational pull, which is 2.2 times greater than that of the sun purely because of its closeness to the earth. When both the sun and the moon exert its effects together at its maximum intensity, a phenomenon known as a ‘spring tide’ take place.
The gravitational pull exerted on the earth’s water changes as the moon rotates around the earth as well as due to the earth’s movement around its own axis. In addition, both the earth and the moon orbits around the sun and thereby forming a complex interrelation between each other’s gravitational pull at different times of the year. However, the changes in the gravitational pull that is exerted within 24 hours is enough to cause the vertical height of the sea waves to reach two peaks (high tides) and two lows (low tides). The duration between each of these tides is around 12 hours and 25 minutes. However, the time at which these waves occur each day can change from one day to another although there is a possibility of predicting the timing based on certain factors.
There are two instances where the gravitational pull of both the sun and the moon augment each other and is at its highest. One such instance is the time of ‘new moon’, in which case both the sun and the moon aligns with the earth on the same side. The second instance is the time of ‘full moon’ where the sun and the moon align on the opposite sides of the earth. In both these instances, the force of the gravitational pull would be enough to form two extremes of the tide, which is known as the ‘spring tide’. However, it should be remembered that ‘spring tide’ is not related to the ‘spring season’ as its name implies. Such alignments usually take place every two weeks and the spring tide that results from these alignments is usually 20% higher or lower than that of a normal tide.
Although all spring tides are usually the same, there are rare instances in which the tides are extremely high. This occurs when the moon is at its closest to the earth. The name given to describe such positioning is ‘proxigee’ and the resulting spring waves are given the name ‘proxigean spring tide’. It should be remembered that this type of event takes place once every 1.5 years during a new moon phase. In some instances, these tides have caused devastation to both human lives and property and even at present, the ability to predict the enormity of such a tide is minimal.
