UPSC Prelims 2015 GS Paper I · Q14 of 100 Geography medium

What explains the eastward flow of the equatorial counter-current?

  1. (a) The Earth's rotation on its axis
  2. (b) Convergence of the two equatorial currents ✓ UPSC's answer
  3. (c) Difference in salinity of water
  4. (d) Occurrence of the belt of calm near the equator

Why the answer is (b)

• The North and South Equatorial Currents, driven west by the trade winds, pile up water on the western side of ocean basins.

• Between them, in the doldrums where winds are weak, this accumulated water flows back eastward as the Equatorial Counter-Current, driven by the pressure gradient created by the convergence of the two currents — option (b).

• The Earth's rotation (a) deflects currents but does not cause the counter-flow; salinity (c) is not the driver; the calm belt (d) permits but does not explain it.

• Hence option (b).

Why the other options are wrong

(a) The Earth's rotation on its axis
Rotation deflects currents; it does not create the counter-current.
(c) Difference in salinity of water
Salinity differences do not drive the counter-current.
(d) Occurrence of the belt of calm near the equator
The calm belt allows the flow but is not its cause.

Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2015, held on 23 August 2015. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.

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