UPSC Prelims 2001 · General Studies
Question 55: Geography
Consider the following statements: I. Most magmas are a combination of liquid, solid and gas. II. Water vapour and carbon dioxide are the principal gases dissolved in a magma. III. Basaltic magma is hotter than the silicic magma. Which of these statements are correct?
AnswerThe answer is (d).
All three statements are correct. Magma is a mixture of molten rock (liquid), crystals (solid) and dissolved gases. The main gases are water vapour and carbon dioxide. Basaltic magma, low in silica, is hotter and runnier, while silicic (rhyolitic) magma is cooler, thicker and more explosive. Remember that high-silica magma is more viscous and gives explosive eruptions.
- I. Most magmas combine liquid, solid and gas.
- II. Water vapour and carbon dioxide are the principal dissolved gases.
- III. Basaltic magma is hotter than silicic magma.
Why each option is right or wrong
- (a) II and III are also correct.
- (b) III is also correct.
- (c) I is also correct.
- (d) Right: all three are correct.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2001, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.