# IAS Prelims Exam: Physical Geography NCERT Questions: WATER (Oceans)

Mar 18, 2016 11:45 IST

For the Civil Services IAS Exam Geography has vast and it covers most sections of the General Studies for the IAS Prelims Exam. The geography is scientific in its orientation and hence the IAS Aspirants having Arts background find it very difficult to prepare the geography for the IAS Prelims Exam

Q1. The percentage of water on the earth’s surface is highest in which among the following
a.    Groundwater
b.    Icecaps and Glaciers
c.    Lakes
d.    Streams and rivers

Explanation:
Oceans- 97.25%, Ice Caps and Glaciers- 2.05%, Groundwater- 0.68%, Lakes- 0.01, Soil Moisture- 0.005, Atmosphere- 0.001%, Streams and rivers 0.0001%, Biosphere - 0.00004%

Q2. Consider the following statements
1. 59 per cent of the water that falls on land returns to the atmosphere through evapo-transpiration.
2. Renewable water on the earth is constant

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Explanation:
Nearly 59 per cent of the water that falls on land returns to the atmosphere through evaporation from over the oceans as well as from other places. The remainder runs-off on the surface, infiltrates into the ground or a part of it becomes glacier. It is to be noted that the renewable water on the earth is constant while the demand is increasing tremendously.

Q3. Water stored in oceans undergoes which of the following processes of water cycle?
1. Evaporation
2. Evapo-transpiration
3. Condensation

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Explanation:
Water stored in oceans undergoes Evaporation, Evapo-transpiration, and Sublimation processes of water cycle.

Q4. Consider the following statements
1. The Siberian shelf in the Arctic Ocean, is the largest in the world
2. Continental shelves are the source of fossil fuels.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Explanation:
The shelves are almost absent or very narrow along some of the margins like the coasts of Chile, the west coast of Sumatra, etc. On the contrary, the Siberian shelf in the Arctic Ocean, the largest in the world, stretches to 1,500 km in width. Massive sedimentary deposits received over a long time by the continental shelves, become the source of fossil fuels.

Q5. Consider the following statements
1. The continental slope boundary indicates the end of the continents.
2. Canyons and trenches are observed in deep sea plane.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Explanation:
The continental slope connects the continental shelf and the ocean basins. The slope boundary indicates the end of the continents. Canyons and trenches are observed in this region.

Q6. Which division of ocean floor is significant in the study of plate movements?
a. Deep sea plains
b. Oceanic Deeps or Trenches
c. Continental Slope
d. Continental Shelf

Explanation:
Oceanic Deeps or Trenches occur at the bases of continental slopes and along island
arcs and are associated with active volcanoes and strong earthquakes. That is why they are
very significant in the study of plate movements.

Q7. Consider the following statements
1. Atolls are islands found in tropical regions surrounding central depression.
2. Atolls are also formed enclosing fresh water body.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Explanation:
Atolls are low islands found in the tropical oceans consisting of coral reefs surrounding a central depression. It may be a part of the sea (lagoon), or sometimes form enclosing a body of fresh, brackish, or highly saline water.

Q8. Which of the following factors affect temperature distribution of ocean water?
1. Latitude
2. Prevailing wind
3. Unequal distribution of land and water

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Explanation:
The factors which affect the distribution of temperature of ocean water are Latitude, Unequal distribution of land and water, Prevailing wind, Ocean currents. The oceans in the northern hemisphere receive more heat due to their contact with larger extent of land than the oceans in the southern hemisphere.  The winds blowing from the land towards the oceans drive warm surface water away from the coast resulting in the upwelling of cold water from below. It results into the longitudinal variation in the temperature.

Q9. Consider the following statements
1. All enclosed seas record relatively higher temperature than open seas.
2. Thermocline is boundary region, from where there is a rapid increase of temperature

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Explanation:
The enclosed seas in the low latitudes record relatively higher temperature than the open seas; whereas the enclosed seas in the high latitudes have lower temperature than the open seas.  The boundary region, from where there is a rapid decrease of temperature, is called the thermocline.

Q10. Consider the following statements
1. The temperature structure of oceans over all latitudes can be described as a three-layer system from surface to the bottom.
2. The highest temperature is not recorded at the equator.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Explanation:
The temperature structure of oceans over middle and low latitudes can be described as
a three-layer system from surface to the bottom. The oceans in the northern hemisphere record relatively higher temperature than in the southern hemisphere. The highest temperature is not recorded at the equator but slightly towards north of it.

Q11. Which of the following is/are factors contributing to salinity of ocean?
1. Wind
2. Precipitation
3. Condensation

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Explanation:
The salinity of water in the surface layer of oceans depends mainly on evaporation and precipitation. Surface salinity is greatly influenced in coastal regions by the fresh water flow from rivers, and in Polar Regions by the processes of freezing and thawing of ice.  Wind, also influences salinity of an area by transferring water to other areas.  The ocean currents contribute to the salinity variations.

Q12. Consider the following statements
1. In the Atlantic Ocean, the surface water temperatures are close to 0° C and so the temperature change with the depth is very slight.
2. Salinity, temperature and density of water are interrelated.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Explanation:
In the Arctic and Antarctic circles, the surface water temperatures are close to 0° C and so the temperature change with the depth is very slight. Here, only one layer of cold water exists, which extends from surface to deep ocean floor. Salinity, temperature and density of water are interrelated. Hence, any change in the temperature or density influences the salinity of an area.

Q13.   With reference to salinity of ocean, which of the following is/are true?
1. In the western part of Northern hemisphere salinity decreases.
2.  In Pacific Ocean salinity variation is high.
3. The North Sea, in spite of its location in higher latitudes, records higher salinity.

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Explanation:
The salinity variation in the Pacific Ocean is mainly due to its shape and larger areal extent. Salinity decreases on the western parts of the northern hemisphere because of the influx of melted water from the Arctic region. The North Sea, in spite of its location in higher latitudes, records higher salinity due to more saline water brought by the North Atlantic Drift. Baltic Sea records low salinity due to influx of river waters in large quantity.

Q14. Among the dissolved salts in sea water, which of the following salt is in highest quantity in per kg of sea water?
a.    Calcium
b.    Sulphate
c.    Chlorine
d.    Sodium

Explanation:
Dissolved Salts in Sea Water (gm of Salt per kg of Water) : Chlorine 18.97, Sodium 10.47, Sulphate 2.65, Magnesium 1.28, Calcium 0.41.

Q15. Consider the following statements
1. Salinity of Bay of Bengal is lesser than Arabian Sea.
2. Arabian Sea shows higher salinity due to low evaporation and low influx of fresh water.

Select the correct answer from the following codes
a. Only 1
b. Only 2
c. Both 1 and 2
d. Neither 1 nor 2

Explanation:
The low salinity trend is observed in the Bay of Bengal due to influx of river water by the river Ganga. On the contrary, the Arabian Sea shows higher salinity due to high evaporation and low influx of fresh water.

Q16. With reference to vertical distribution of salinity of oceans, which of the following is/are true?
1. Salinity at the surface waters always increases by the loss of water by evaporation.
2. In a distinct zone called the halocline, salinity decreases sharply.
3. Salinity at depth is very much fixed.

Select the correct answer from the following codes
a.    Only 1
b.    Only 1 and 2
c.    Only 2 and 3
d.    1,2 and 3

Explanation:
Salinity at the surface increases by the loss of water to ice or evaporation, or decreased by the input of fresh waters, such as from the rivers. Salinity at depth is very much fixed, because there is no way that water is ‘lost’, or the salt is ‘added.’ Salinity, generally, increases with depth and there is a distinct zone called the halocline, where salinity increases sharply. Other factors being constant, increasing salinity of seawater causes its density to increase.

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