UPSC Prelims 2015 Q14: Geography – Oceanography
What explains the eastward flow of the equatorial counter - current?
- (a) The Earth’s rotation on its axis
- (b) Convergence of the two equatorial currents
- (c) Difference in salinity of water
- (d) Occurrence of the belt of calm near the equator
Answer: (b) Convergence of the two equatorial currents
Explanation
Eastward flow of the equatorial counter-current
The North and South Equatorial Currents are pushed westward by the trade winds.
They converge and pile up water on the western side of the ocean.
This water then flows back eastward along the calm equatorial belt.
| Current | Direction | Driven by |
|---|---|---|
| North Equatorial Current | East to west | North-east trade winds |
| South Equatorial Current | East to west | South-east trade winds |
| Equatorial Counter-Current | West to east | Return flow of piled-up water |
The options checked:
| Option | Verdict |
|---|---|
| (a) The Earth's rotation on its axis | Incorrect; it deflects currents, it does not cause this return flow |
| (b) Convergence of the two equatorial currents | Correct |
| (c) Difference in salinity of water | Incorrect |
| (d) Occurrence of the belt of calm near the equator | Incorrect; the calm belt only allows the flow |
Answer: (b) Convergence of the two equatorial currents.
Why each option is right or wrong
- (a) Incorrect. The Earth's rotation bends currents but does not explain this eastward flow.
- (b) CORRECT. The convergence of the two equatorial currents piles up water that flows back east.
- (c) Incorrect. A difference in salinity drives deep circulation, not this surface current.
- (d) Incorrect. The belt of calm lets the current pass; it is not the cause.
Key point
Equatorial counter-current: eastward return flow of water piled up in the west by the converging North and South Equatorial Currents.
Remember
Counter-current = return flow of the two equatorial currents.
Common mistakes
- Choosing the belt of calm (doldrums), which permits but does not cause the flow.
- Thinking all equatorial currents flow west; the counter-current flows east.
- Confusing surface currents with thermohaline circulation driven by salinity.
Exam tip
Water pushed west must come back east. The counter-current is that return path.
Sources
- NCERT Class XI — Fundamentals of Physical Geography, Ch 14 (Movements of Ocean Water)
- G.C. Leong — Certificate Physical and Human Geography (The Oceans)