What explains the eastward flow of the equatorial counter-current?
Answer & explanation
Answer: (b) Convergence of the two equatorial currents
The answer is (b). The trade winds push the North and South Equatorial Currents westward, and together they pile up water in the western part of each ocean basin. Gravity makes this piled-up water flow back east, where the winds are weak along the equator. That return flow is the equatorial counter-current.
- ✓ (b) Both westward equatorial currents carry water to the western side of the ocean basin, where it piles up. Gravity then sends that water back eastward, and this flow is the counter-current.
- ✗ (d) The belt of weak winds near the equator is only the path the return flow takes. The cause of the eastward flow is the water piled up in the west by the two equatorial currents.
- ✗ (a) The Earth's rotation deflects moving water, but it does not explain why this current flows east. The counter-current is water returning east under gravity after the equatorial currents pushed it west.
- ✗ (c) Differences in salinity change the density of water, but they do not drive this current. The eastward flow comes from water piled up in the west by the two equatorial currents.
Remember · Trade winds drive the North and South Equatorial Currents west, and they pile water up in the west. Gravity sends it back east, along the weak-wind belt at the equator, as the equatorial counter-current.
Sources
- NOAA JetStream – JetStream Max: Major Ocean Currents ↗ “The reason for their motion "counter" (opposite) to the wind flow is because the northern and southern equatorial currents, pushed westward by the trade winds, pile up water in the western portion of each ocean basin. … Because of the pile of water, gravity causes it to flow back eastward across the ocean basin in the area where the winds are weak, which is along the equator”
Question: UPSC Civil Services (Preliminary) 2015, General Studies Paper I. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·
