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GeographyMediumAsked in: NDA · NDA-I 2021, GAT

The process whereby certain minerals absorb water, expand and change is called as

  1. A.Hydration
  2. B.Oxidation
  3. C.Hydrolysis
  4. D.Carbonation

Correct answer

A. Hydration

Explanation

The correct answer is A, Hydration. In hydration, minerals take water into their structure, swell in volume and change into new minerals, which loosens and breaks the rock.

Hydration is a process of chemical weathering. When a mineral absorbs water chemically, it expands, and repeated wetting and drying makes rocks crumble. A common example is anhydrite (calcium sulphate) changing into gypsum by taking up water; the swelling can force rock layers apart. Clay minerals also expand when wet and shrink when dry. Because the volume grows, hydration often works together with physical weathering to break rocks into smaller grains.

B is wrong because oxidation is the reaction of minerals, mostly iron, with oxygen, which gives rocks a red or brown rusty colour. C is wrong because hydrolysis is the reaction of minerals with water in which water's hydrogen and hydroxyl ions break the mineral down; feldspar turning into clay is the standard example, and it is not described by swelling. D is wrong because carbonation is the reaction of rocks such as limestone with carbonic acid in rainwater, which dissolves them and forms caves.

Exam tip: hydration means absorb water and swell; oxidation means rust; carbonation means limestone dissolved.

Practice Questions

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Q2.GeographyAsked in: CDS · CDS-II 2017, GKMedium

Which of the following statements is/are correct? 1. Himalayan rivers have their origin in the snow-covered areas, hence are dry in winter season. 2. Rivers of the Peninsular Plateau have reached maturity. 3. Himalayan rivers depict all the three stages of normal cycle of erosion. Select the correct answer using the code given below.

  1. A.2 only
  2. B.1 and 3 only
  3. C.2 and 3 only
  4. D.1, 2 and 3
Show answer
Correct answer: C. 2 and 3 only

Himalayan rivers are perennial, so statement 1 is wrong, while statements 2 and 3 are correct. Himalayan rivers such as the Ganga, Indus and Brahmaputra rise from glaciers and snowfields and also get monsoon rain, so they flow all year round, including in winter.

Q3.GeographyAsked in: CDS · CDS-II 2017, GKMedium

Which of the following statements related to latitude are true? 1. Rainfall, temperature and vegetation vary with latitude. 2. The difference between the longest day and the shortest day increases with latitude. 3. Indira Point is located approximately at 6°45' N latitude. Select the correct answer using the code given below.

  1. A.1 and 2 only
  2. B.1 and 3 only
  3. C.2 and 3 only
  4. D.1, 2 and 3
Show answer
Correct answer: D. 1, 2 and 3

All three statements about latitude are true. Latitude decides how directly the Sun's rays strike a place, so temperature, rainfall and the type of vegetation change from the equator towards the poles, from hot, wet rainforests to cold tundra.

Q4.GeographyAsked in: CDS · CDS-II 2017, GKMedium

Which of the following lakes is/are situated in Ladakh? 1. Tso Kar 2. Pangong Tso 3. Tsomgo 4. Tso Moriri Select the correct answer using the code given below.

  1. A.1 only
  2. B.2 and 3
  3. C.1, 2 and 4
  4. D.2 and 4 only
Show answer
Correct answer: C. 1, 2 and 4

Tso Kar, Pangong Tso and Tso Moriri are high-altitude lakes of Ladakh, while Tsomgo lies in Sikkim. Pangong Tso, at about 4,350 metres, is a long, narrow lake that stretches from Ladakh into Tibet, and most of its length lies on the Chinese side.