2021 GS Paper I, all questions
UPSC Prelims 2021 · GS Paper I
Question 64: Geography
The black cotton soil of India has been formed due to the weathering of
abrown forest soil
bfissure volcanic rock
cgranite and schist
dshale and limestone
AnswerUPSC’s answer is (b).
Black cotton soil, or regur, forms from the weathering of basaltic lava, a fissure volcanic rock, of the Deccan Traps. It covers Maharashtra, Gujarat, Madhya Pradesh and neighbouring areas. Its clay holds moisture well and it swells when wet and cracks when dry. It is rich in lime, iron, calcium and magnesium but poor in nitrogen, phosphorus and organic matter. Remember: regur means Deccan basalt.
Why each option is right or wrong
- (a) Wrong: brown forest soil is a different soil of cooler, forested areas.
- (b) Right: black soil weathers from Deccan basaltic lava.
- (c) Wrong: granite and schist weathering gives red soil.
- (d) Wrong: shale and limestone do not give black cotton soil.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2021, General Studies Paper I, Series A. The paper on upsc.gov.in.