UPSC Prelims 2011 · GS Paper I
Question 94: Geography
What could be the main reason/reasons for the formation of African and Eurasian desert belt ?
- 1.It is located in the sub-tropical high pressure cells.
- 2.It is under the influence of warm ocean currents.
Which of the statements given above is/are correct in this context ?
AnswerThe answer is (a).
The great desert belt from the Sahara through Arabia to Central Asia lies near 20 to 30 degrees north, under the subtropical high-pressure cells, where air descends, warms and dries, so rain is rare. Warm ocean currents would bring moisture and reduce aridity; the deserts on west coasts of continents are in fact lined by cold currents, such as the Canary and Benguela, which cool the air above them and prevent rain.
- 1. Descending dry air in the subtropical highs produces desert belts.
- 2. Cold, not warm, currents run along the desert coasts.
How you could have got this
- If you were sure statement 1 is correct, (b) and (d) go: each of them leaves 1 out.
What you needed to know: Descending dry air in the subtropical highs produces desert belts.
- Then, if you were sure statement 2 is not correct, (c) goes: it includes 2.
What you needed to know: Cold, not warm, currents run along the desert coasts.
Only (a) is left. This one needs every statement.
This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Right: the belt lies under subtropical high pressure cells.
- (b) Warm currents bring moisture; the desert coasts have cold currents.
- (c) Statement 2 is wrong, so 'both' fails.
- (d) Statement 1 is correct, so 'neither' fails.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2011, General Studies Paper I, Series A. The paper on upsc.gov.in.