Question

Answer the following question:

What are tides and how are they caused?

Answer 1

Tides are the rhythmic rise and fall of ocean water twice in a day. High tide occurs when ocean water covers much of the shore by rising to its highest level. When ocean waterfalls to its lowest level and recedes from the shore, it is referred to as low tide. Tides are caused by the strong gravitational pull exerted by the Sun and the Moon on the Earth’s surface.

Formation of high and low tides:

The water of the Earth closer to the Moon gets pulled under the influence of Moon’s gravitational force, thereby causing a rise of ocean water towards the Moon. At the same time, the ocean water at the opposite side of the Earth bulges away from the moon. These bulges (or rises in the height of ocean water) are called high tides. When ocean waterfalls back, low tides occur. Say, the point I is a point on Earth that faces the Moon and point IV is at the opposite end of the Earth. Under the gravitational pull of the Moon, the ocean water at the point I move towards the pulling force. At the same time, the ocean water at point IV moves away from the pulling force. Both these movements are high tides as the ocean water rises to its highest level at both these points. Due to the Earth’s rotation on its axis and the Moon’s revolution in its orbit, after a certain time period, the ocean water at both points I and IV recedes to its lowest level, thereby causing low tides. When the moon is directly above point IV, the entire process is repeated, with points I and IV first experiencing high tides, and then, low tides. Hence, in a day, both points I and IV experience two high tides and two low tides.

Formation of spring and neap tides:

When the Sun, the Moon and the Earth are in the same line, the combined gravitational pulls of both the Sun and the Moon cause the highest high tides, i.e., high tides are the highest. These tides are called spring tides.

When the gravitational pull of the Moon on the Earth is perpendicular to the gravitational pull of the Sun on the Earth, the gravitational forces counteract, thereby causing the formation of the lowest low tides, i.e., low tides are the lowest. These tides are called neap tides.