Hydrosphere — Oceans, Tides and Currents — GK Questions with Answers

1. Which of these seas/gulfs has the highest salinity?
   1. Persian Gulf
   2. Red Sea
   3. Mediterranean Sea
   4. Caribbean Sea
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   Answer: (B) Red Sea

   Strong evaporation and almost no rivers make the Red Sea the saltiest (up to about 40‰).

2. Choose the correct statements about tides — 1. Tides result from the combined pull of the Sun and Moon and the forces arising on the Earth. 2. In the hemisphere facing the Moon, the Moon’s pull exceeds the centrifugal force.
   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither
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   Answer: (C) Both 1 and 2

   On the far side the centrifugal force wins — that is why two opposite high tides form.

3. The eastward flow of the Equatorial Counter-current is explained by — (IAS 2015)
   1. The Earth’s rotation on its axis
   2. Convergence of the two equatorial currents
   3. Difference in water salinity
   4. The belt of calm (doldrums) near the equator
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   Answer: (B) Convergence of the two equatorial currents

   The two equatorial currents pile water in the west; it flows back east between them.

4. Choose the correct statements — 1. The temperature and salinity differences that start the deep-sea thermohaline circulation arise at the surface in the low-latitude wind belts. 2. The deep currents of the Indian Ocean originate in the seas around Antarctica.
   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither
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   Answer: (B) 2 only

   Thermohaline circulation starts where cold, salty high-latitude water sinks — statement 1 is wrong; cold bottom water formed near Antarctica spreads into the Indian Ocean — statement 2 is right.

5. Choose the correct statements — 1. A neap tide occurs when the Moon, Earth and Sun are in a line. 2. If a strong storm passes near the coast during a spring tide, destructive waves rise at high tide.
   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither
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   Answer: (B) 2 only

   Alignment gives a spring tide, not a neap tide.

6. Choose the correct statements — 1. The Red Sea is warmer than the Persian Gulf. 2. The Baltic Sea is saltier than the Black Sea.
   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither
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   Answer: (D) Neither

   The Persian Gulf is warmer; the Baltic (≈ 7‰) is less salty than the Black Sea (≈ 18‰).

7. Choose the correct statements — 1. The Benguela is the only cold current of the South Atlantic. 2. The Agulhas is a warm current running south from below Madagascar along the African coast. 3. The Brazil Current is warm and flows southward off the Brazilian coast.
   1. 1 only
   2. 1 and 2
   3. 2 and 3
   4. None
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   Answer: (C) 2 and 3

   The Falkland is also a cold current in the South Atlantic, so statement 1 is wrong.

8. The world’s most important fishing grounds lie where — (IAS 2015)
   1. Warm and cold atmospheric currents meet
   2. Rivers bring large volumes of water
   3. Warm and cold ocean currents meet
   4. The continental shelf is undulating
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   Answer: (C) Warm and cold ocean currents meet

   E.g. the Grand Bank (Gulf Stream + Labrador) and Japan (Kuroshio + Oyashio).

9. Choose the correct statements — 1. Fresh water available for use is less than about 1% of all water on Earth. 2. 95% of all fresh water is in polar ice and glaciers. (IAS 2010)
   1. 1 only
   2. 2 only
   3. Both 1 and 2
   4. Neither
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   Answer: (A) 1 only

   Ice and glaciers hold about 68.7% of fresh water (USGS), not 95%.

10. Which strait is nearest to the International Date Line? (IAS 2008)
    1. Bering
    2. Florida
    3. Dover
    4. Gibraltar
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    Answer: (A) Bering

    The Date Line passes through the Bering Strait.

11. Choose the correct statements — 1. The annual range of temperature is greater in the Pacific than in the Atlantic. 2. The annual range of temperature is greater in the Northern Hemisphere than in the Southern. (IAS 2007)
    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither
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    Answer: (B) 2 only

    The Atlantic is more enclosed by land, so its range is larger; the Northern Hemisphere has more land, so its range is larger.

12. In which ocean is the Diamantina Trench? (IAS 2006)
    1. Pacific
    2. Atlantic
    3. Indian
    4. Arctic
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    Answer: (C) Indian

    It lies in the Indian Ocean, south-west of Australia.

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