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GeographyMediumAsked in: UPSC CAPF · CAPF 2023, Paper I

Consider the following statements : 1. Many of the world's largest mountain chains exist beneath the sea. 2. Some mountain chains are revealed as island arcs. 3. The mid-oceanic ridges form the longest mountain chains. 4. The mid-Atlantic ridge rises thirty-three metres above the floor of the Atlantic. Which of the statements given above are correct ?

  1. A.1 and 2 only
  2. B.3 and 4 only
  3. C.1, 2 and 4 only
  4. D.1, 2 and 3 only

Correct answer

D. 1, 2 and 3 only

Explanation

The correct answer is D, 1, 2 and 3 only. Statement 4 is wrong: the Mid-Atlantic Ridge rises thousands of metres above the ocean floor, not thirty-three metres.

The ocean floor has relief as varied as the land. The mid-oceanic ridge system winds through all the oceans for about 65,000 km, making it the longest mountain chain on Earth, and most of it lies hidden under the sea. Where ocean plates sink beneath one another, curved chains of volcanic islands called island arcs rise above the water, such as the Aleutians, the Kurils and the islands of Japan. The Mid-Atlantic Ridge, an S-shaped range running down the middle of the Atlantic, rises roughly 2,500–3,000 metres above the floor, and its highest peaks break the surface as islands such as Iceland and the Azores.

A is wrong: it leaves out statement 3, which is correct.

B is wrong: it includes statement 4 and leaves out statements 1 and 2.

C is wrong: it includes statement 4, which is false.

Exam tip: Mid-oceanic ridges: longest mountain system (about 65,000 km), formed where plates move apart; Iceland sits on the Mid-Atlantic Ridge.

Practice Questions

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Q1.GeographyAsked in: CDS · CDS-I 2018, GKHard

Statement I : Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.

Statement II : The Earth rotates from west to east.

  1. A.Both the statements are individually true and Statement II is the correct explanation of Statement I
  2. B.Both the statements are individually true but Statement II is not the correct explanation of Statement I
  3. C.Statement I is true but Statement II is false
  4. D.Statement I is false but Statement II is true
Show answer
Correct answer: B. Both the statements are individually true but Statement II is not the correct explanation of Statement I

Both statements are true, but the direction in which the Earth spins does not explain why tides occur. Tides are caused mainly by the Moon's pull, with the Sun adding a smaller pull; the Moon's tide-raising force is roughly twice the Sun's because it is so much closer.

Q4.GeographyAsked in: UPSC CAPF · CAPF 2023, Paper IMedium

Consider the following statements :

1. The Great Northern Plains are formed by basins of three distinct river systems - the Indus, the Ganga and the Brahmaputra.

2. They are one of the most densely populated areas on Earth.

3. Between the Yamuna at Delhi and the Bay of Bengal, nearly 1600 km away, there is a drop of only 200 metres in elevation.

Which of the statements given above are correct?

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

All three statements correctly describe the Northern Plains of India. The Northern Plains were built from alluvium laid down by the Indus, the Ganga and the Brahmaputra and their tributaries, which together drain the Himalayas.