UPSC General Studies Sample Paper General Studies Sample Paper-8

  • question_answer
    Coastal deserts are generally found on the West coast of continents such as the Namib in Atacama in Chile, the Atlantic Coastal Desert in Morocco or the deserts of Baja in California Which of the following are the reasons for this phenomena?                              
    1. Gravitation of Sun and Moon.              
    2. Global circulation of oceanic currents.   
    3. Sea floor spreading.                       
    4. Coriolis force,                       
    5. Earth's rotation.                                                                
    Select the correct answer using the codes given below.                                

    A)  2 and 3           

    B)  1, 3 and 5         

    C)  1, 2, 4 and 5                

    D)  All of these 

    Correct Answer: C

    Solution :

    [c] The question says that around the mid-latitudinal belt, only the Western side of continents is normally occupied by deserts, while the Eastern side is covered by forests. The reason for this has to do with the global circulation of ocean currents: gravitation from the Sun and the Moon pulls air and water on the Earth's surface and tends to make them lag behind, relative to the Earth's rotational movement. We know that the gravitational drag is greatest in the equator, where the centrifugal speed of the Earth is fastest. Thus, as the Earth turns, ocean currents and winds flow in the equator from East to West, tugged by universal gravitation, forming the equatorial currents and the easterly trade winds. As the West bound surface waters move away from the continents, they pull cold, nutrient rich waters to the surface that generate a cool, stable coastal atmosphere, with little evaporation from the sea and very low rainfall other than morning fogs. In the coasts neighbouring these oceanic upwelling, typical coastal fog deserts tend to develop, forming some of the driest ecosystems on Earth. Thus, the large-scale circulation of the ocean is the main reason why coastal deserts are always found on the West coast.

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