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Physical Geography (UPSC) (Part-III)

📆 March 8, 2025

Total Questions: 44

11. With reference to agricultural soils, consider the following statements: [2018-I]

  1. A high content of organic matter in soil drastically reduces its water holding capacity.
  2. Soil does not play any role in the Sulphur cycle.
  3. Irrigation over a period of time can contribute to the salinization of some agricultural lands.

 

Which of the statements given above is/are correct?

Correct Answer: (b) 3 only
Solution:The process of decay, added by bacterial action, transforms organic matter into humus. Humus enhances water retention capacity of the soil. So, 1 is wrong. By elimination, we are left with Answer (b): 3 only.

12. Which of the following is/are the possible consequence/s of heavy sand mining in riverbeds? [2018-I]

  1. Decreased salinity in the river
  2. Pollution of groundwater
  3. Lowering of the water-table

 

Select the correct answer using the code given below:

Correct Answer: (b) 2 & 3 only
Solution:Sand Mining wrecks the intertidal area and creates the imminent danger of saline water ingress into fresh water. Meaning salinity will increase, so statement 1 is wrong. By elimination, we've the answer (b) 2 and 3 only.

In this question, the first statement is wrong, and you've to identify the right statements. So in real exam stress, some students may have made an error of reading/ticking, and they'd have ticked the wrong option A: only 1. (You're right that it's a wrong statement, but you're not asked to tick the wrong one.) So, be mindful of ticking in OMR.

13. Consider the following statements: [2018-I]

  1. The Earth's magnetic field has reversed every few hundred thousand years.
  2. When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.
  3. When living organisms originated, they modified the early atmosphere of the Earth.

 

Which of the statements given above is/are correct?

Correct Answer: (c) 1 & 3 only
Solution:"There was no atmosphere on early earth. Water vapour, methane, carbon dioxide, and ammonia released from molten mass covered the surface." So #2 is wrong, CO₂ was present. We are left with (a) or (c). In both options, the first statement is correct but experts were divided over third statement. because early Early atmosphere of earth had no free oxygen, the (life) forms until then could at best be only "anaerobic" So those living organisms did not have capacity to alter the atmosphere, atleast not in a significant manner. UPSC has kept 'c' as the official answer.

14. On 21st June the sun [2019-I]

Correct Answer: (a) Does not set below the horizon at the Arctic circle
Solution:
  • On 21st June, the Northern Hemisphere is tilted towards the sun. The rays of the sun fall directly on the Tropic of Cancer. So, (c) and (d) are wrong.
  • Places beyond the Arctic Circle experience continuous daylight for about six months. So (a) is correct.

15. Why are dewdrops not formed on a cloudy night? [2019-I]

Correct Answer: (b) Clouds reflect back the Earth's radiation.
Solution:The favorable weather elements for dew include clear skies, light wind, and decent soil moisture. Clear skies allow for the maximum release of longwave radiation to space. Cloudy skies will reflect and absorb while re-emitting longwave radiation back to the surface, preventing as much cooling from occurring. So (b) is the most appropriate reason.

16. With reference to Ocean Mean Temperature (OMT), which of the following statements is/are correct? [2020-I]

  1. OMT is measured up to a depth of 26°C isotherm which is 129 meters in the south-western Indian Ocean during January – March.
  2. OMT collected during January – March can be used in assessing whether the amount of rainfall in monsoon will be less or more than a certain long-term mean.

 

Select the correct answer using the code given below:

Correct Answer: (b) 2 only
Solution:
  • OMT is measured up to a depth of 26-degree C isotherm. During January-March, the mean 26-degree C isotherm depth in the Southwestern Indian Ocean is 59 meters. So, #1 is wrong.
  • Sea Surface Temperature (SST) is routinely used for predicting whether the total amount of rainfall that India receives during the monsoon season will be less or more than the long-term mean. However, Ocean Mean Temperature (OMT) has a better ability to predict this than SST. So, #2 is correct.

17. Consider the following statements [2020-I]

  1. Jet streams occur in the Northern Hemisphere only.
  2. Only some cyclones develop an eye.
  3. The temperature inside the eye of a cyclone is nearly 10°C lesser than that of the surroundings.

 

Which of the statements given above is/are correct?

Correct Answer: (c) 2 only
Solution:
  • Jet streams are high-altitude westerly wind systems that blow at a height of 6 to 14 km, with very high speeds up to 450 km/hr in wavy form in both hemispheres. So #1 is wrong.
  • The centre of the cyclone is called the Eye. The eye is a calm region with no rainfall and experiences the highest temperature and lowest pressure within the cyclonic system. So #3 is wrong.
  • By elimination, the answer is (c).

18. Which one of the following is a reason why astronomical distances are measured in light-years? [2021-I]

Correct Answer: (d) Speed of light is always the same.
Solution:Cosmologists use the light-year as a measuring tool because the speed of light in empty space (vacuum) never changes. It remains constant. So, "D" is right.

19. With reference to the water on the planet Earth, consider the following statements: [2021-I]

  1. The amount of water in the rivers and lakes is more than the amount of groundwater.
  2. The amount of water in polar ice caps and glaciers is more than the amount of groundwater.

 

Which of the statements given above is/are correct?

Correct Answer: (b) 2 only
Solution:
  • Out of the total water available on Earth: 97% in oceans 2% in ice caps 0.68% in groundwater 0.009% in lakes 0.0001% in rivers.
  • So, accordingly, statement #1 is wrong but statement #2 is right. Therefore, Correct Answer is (b): 2 Only.

20. Consider the following statements: [2021-I]

  1. Moringa (drumstick tree) is a leguminous evergreen tree.
  2. Tamarind tree is endemic to South Asia.
  3. In India, most of the tamarind is collected as minor forest produce.
  4. India exports tamarind and seeds of moringa.
  5. Seeds of moringa and tamarind can be used in the production of biofuels.

 

Which of the statements given above are correct?

Correct Answer: (b) 3, 4 & 5
Solution:
  • Tamarind (Tamarindus indica) is native to tropical Africa and NOT Asia. So, #2 is wrong, thus A and D are eliminated & We are left 50:50 with Option B or C. In both the remaining options B or C, statements #3 and #4 are common, so we need not check them for validity.
  • Moringa/drumstick tree is a small deciduous tree native to tropical Asia. That means it is not an evergreen tree, so #1 is wrong. Thus, C was eliminated. We are left with the correct answer: "B".
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