SSC Geography Sample Paper NCERT Sample Paper-5

  • question_answer
    Consider the following statements:
    1. Most magma is a combination of liquid, solid and gas
    2. Water vapour and carbon dioxide are the principal gases dissolved in magma
    3. Basaltic magma is hotter than the silicic magma
    4. The magma solidified between sedimentary rocks in a horizontal position is known as dyke. Which of these statements are correct?

    A)  1, 2 and 3        

    B)  2, 3 and 4

    C)  1 and 4

    D)  1, 2 and 4

    Correct Answer: A

    Solution :

    [a] The term Magma is applied to natural, predominantly silicate melts saturated with gases that are dissolved in them. The composition of magma is characterized by the predominance of exactly the same chemical elements which, in the main, constitute the earth's crust viz. Oxygen, Silicon, aluminium, Iron, Calcium, Magnesium, Potassium and aluminium. However, as compared with rocks, magmas are distinguished by a marked quantity of easily volatile compound e.g. water vapours, sulphurous compounds, \[C{{O}_{2}},HCL\], Fluoric hydrogen. Ammonium chloride,\[~{{N}_{2}}\] and others. It exists in high pressure in deep earth, the volatile compounds are found in a dissolved state within magma thus diminishing its viscosity, increases the degree of its mobility and chemical activity with respect to enclosing rocks. It is a molten rock material under the earth's surface at a very high temperature. Magma can be acidic or basic depending on its constituents. Magma solidified between sedimentary rocks in horizontal position is known as sill and vertical position is called dyke.

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