UPSC General Studies Sample Paper General Studies Sample Paper-7

  • question_answer
    Consider the following statements regarding Land Tides.
    1. The main causes of land tides are the gravitational fields of the Sun and Moon and the Earth's elasticity.
    2. Like ocean tides, the Moon has the greatest effect on land tides because it is closer to the Earth than the Sun.
    3. The Sun does have an effect on land tides as well because of its very large size and strong gravitational field.
    4. As the Earth rotates around the Sun and the Moon each of their gravitational fields pull on the Earth.
    Because of this pull there are small deformations or bulges on the Earth's surface or land tides.
    Which of the statements] given above is/are correct?

    A)  Only 1 

    B)  1 and 2            

    C)  1, 2 and 3                    

    D)  All of these

    Correct Answer: D

    Solution :

    [d] The Earth is not a completely rigid body and it is made up of several layers with varying consistency. The Earth has a solid inner core that is surrounded by a liquid outer core. The outer core is surrounded by the mantle which consists of molten rock closest to the outer core and stiff rock closer to the Earth's crust, which is its outermost layer. It is because of these flowing liquid and molten rock layers that the Earth has elasticity and thus, land tides. Like ocean tides where water rises in some areas and it is also forced down in others, the same is true of land tides. Land tides are small though and the actual movement of the Earth's surface is usually not greater than 12 inches.

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