Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R). Assertion (A) : The Himalayas are still rising. Reason (R) : The Indian tectonic plate is colliding with the Eurasian plate. Select the correct answer from the codes given below :
- (a)Both (A) and (R) are true, but (R) is not the correct explanation of (A).
- (b)(A) is false, but (R) is true.
- (c)Both (A) and (R) are true and (R) is the correct explanation of (A).
- (d)(A) is true, but (R) is false.
Correct — C, Both (A) and (R) are true and (R) is the correct explanation of (A). The Assertion is true: the Himalaya is a live, growing range, not a finished one. Satellite geodesy (GPS stations across the arc) records the range being pushed up by a few millimetres a year, the rivers are still cutting gorges faster than the slopes can grade themselves, and the whole belt is India's most earthquake-prone zone precisely because rock is still being shortened there. The Reason is also true, and it is the mechanism, not a coincidence: the Indian plate broke away from Gondwana, drifted north across the Tethys, and began colliding with the Eurasian plate roughly 50 million years ago; India is still driving northward at about 5 cm a year, and a part of that convergence is taken up as crustal shortening and thickening in the Himalaya. Because two continental blocks are of similar low density, neither can be subducted cleanly — so the convergence is absorbed by folding, thrusting and thickening, and thickened crust rises isostatically. Uplift is therefore the direct consequence of collision, which is exactly what (R) being 'the correct explanation of (A)' means.
- (a)Both (A) and (R) are true, but (R) is not the correct explanation of (A). — Both statements are indeed true, but this option denies the causal link, and the causal link is the whole point. There is no other agent lifting the Himalaya — the uplift is the surface expression of continued India–Eurasia convergence, the same convergence that drives the range's earthquakes.
- (b)(A) is false, but (R) is true. — The Assertion is not false. Every standard indicator of a young, actively rising range is present in the Himalaya — deep gorges, abrupt U-turn river courses, steep landslide-prone slopes, several parallel ranges, and a measurable modern uplift rate. Erosion removes a great deal of that uplift, but the range has not stopped growing.
- (d)(A) is true, but (R) is false. — The Reason is not false either. The India–Eurasia collision is one of the best-documented facts in plate tectonics: the suture is traced along the Indus–Tsangpo zone, marine sediments of the vanished Tethys now sit thousands of metres above sea level, and modern GPS measurements show the two plates still converging at roughly 5 cm a year.
The Himalaya is a collision (continent–continent) orogen. About 140 million years ago the Indian plate rifted from Gondwana and drifted north, consuming the floor of the Tethys Sea ahead of it. When the Indian continental block finally met the Eurasian block — the collision is conventionally dated to about 50 million years ago — neither could sink, because continental crust is too buoyant to subduct. The convergence has since been absorbed by folding and by slip on a stack of great north-dipping thrusts, which thickens the crust and pushes the surface up. That process is still running, so the Himalaya is still rising.
Assertion–Reason items are decided in two steps: check each statement on its own, then ask whether the Reason supplies the mechanism for the Assertion. Here both statements are textbook-true, so the only live question is the causal one — and the candidates who lose the mark are those who treat (R) as merely a related fact. It is not: continued convergence IS the cause of continued uplift. A useful cross-check is that both the Assertion and the Reason predict the same third thing — intense seismicity along the arc. Slip on the Main Himalayan Thrust, into which the Main Central Thrust, Main Boundary Thrust and Himalayan Frontal Thrust all sole, is what produced the 1934 Bihar–Nepal and 2015 Gorkha earthquakes; those quakes and the millimetres of annual uplift are two readings of the same collision.
- The Indian plate rifted from Gondwana and drifted north across the Tethys; the collision with Eurasia is conventionally dated to roughly 50 million years ago and the suture is mapped along the Indus–Tsangpo (Indus–Yarlung) zone.
- India continues to converge on Eurasia at about 5 cm a year; a significant part of that is taken up as shortening within the Himalaya itself, which is why the range keeps growing while erosion works against it.
- The Himalayan thrusts, from south to north, are the Himalayan Frontal Thrust, the Main Boundary Thrust and the Main Central Thrust; all of them flatten into the Main Himalayan Thrust at depth, and slip on it caused the 1934 Bihar–Nepal and 2015 Gorkha (M ~7.8) earthquakes.
- Marine sedimentary rocks and ammonite fossils laid down on the floor of the Tethys are now found high in the Tethys (Tibetan) Himalaya — physical evidence that a sea bed was folded and lifted into a mountain range.
- Classic field evidence of youth, which UPSC has asked directly: deep gorges, U-turn river courses, several parallel ranges, and steep gradients that cause frequent landsliding.
- Indian plate rifts from Gondwana (~140 Ma) and drifts north
- Tethys Sea floor consumed; its marine sediments scraped up
- India meets Eurasia (~50 Ma) — neither continental block can subduct
- Convergence continues at ~5 cm/yr — folding + thrusting (MCT, MBT, HFT)
- Crust shortens and thickens → surface uplift of a few mm/yr + major earthquakes
The last box is the Assertion and the box before it is the Reason — the Reason is the mechanism, so the answer is (c).
- Marking option (a) — accepting both statements as true but refusing the causal link. In this topic the collision is the only mechanism on offer, so (R) does explain (A).
- Confusing 'the Himalaya is rising' with 'the Himalaya is getting taller everywhere every year'. Uplift and erosion compete; net elevation change varies from place to place, but tectonic uplift is continuous.
- Assuming the Indian plate is being subducted under Eurasia in the ordinary sense. Continental crust is too buoyant — the convergence is taken up mainly by underthrusting, crustal shortening and thickening.
UPPSC likes this area as Assertion–Reason (the Himalaya, the seismic belt, the thrusts), while UPSC prefers 'which of these features are evidence of X' lists — either way the examiner is testing whether you can name the mechanism, not just the fact.
When you travel in Himalayas, you will see the following : 1. Deep gorges 2. U-turn river courses 3. Parallel mountain ranges 4. Steep gradients causing landsliding Which of the above can be said to be the evidences for Himalayas being young fold mountains?
- (a) 1 and 2 only
- (b) 1, 2 and 4 only
- (c) 3 and 4 only
- (d) 1, 2, 3 and 4
Answer(d) 1, 2, 3 and 4
The same claim from the field side: every feature listed there is surface evidence that the Himalaya is young and still being uplifted by the collision named in this Reason.
Which of the following are the evidences of the phenomenon of continental drift? I. The belt of ancient rocks from Brazil coast matches with those from Western Africa. II. The gold deposits of Ghana are derived from the Brazil plateau when the two continents lay side by side. III. The Gondwana system of sediments from India is known to have its counterparts in six different landmasses of the Southern Hemisphere. Select the correct answer using the code given below.
- (a) I and II only
- (b) I and III only
- (c) I, II and III
- (d) II and III only
Answer(c) I, II and III
The earlier half of the same story — the evidence that India was once part of Gondwana and drifted north, which is what eventually brought it into collision with Eurasia.
Given below are two statements, one is labelled as Assertion (A) and the other as Reason (R). Assertion (A) : The highest concentration of Seismic zones lies in Himalayan region in India. Reason (R) : There are many longitudinal thrust zones in Himalayas. Codes :
- (a) Both (A) and (R) are true and (R) is the correct explanation of (A)
- (b) Both (A) and (R) are true, but (R) is not the correct explanation of (A)
- (c) (A) is true, but (R) is false
- (d) (A) is false, but (R) is true
Answer(a) Both (A) and (R) are true and (R) is the correct explanation of (A)
The same collision seen through its other symptom — the thrust zones that take up the convergence are what make the Himalayan belt India's most seismically active region, and UPPSC framed it as an identical Assertion–Reason item.
With reference to the Himalayan range, which of the statements is/are correct ? 1. The sedimentary rocks of the greater Himalayas were fossil less. 2. Marine livings fossils are found in the sedimentary rocks of lesser Himalayas. 3. Remains of human civilization are found in outer or Shivalik Himalayas. Select the correct answer using the codes given below : Codes :
- (a) 1 and 2 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3 are correct
Answer(d) 1, 2 and 3 are correct
Marine fossils now sitting high in the Himalayan sedimentaries are the fossil record of the collision in this Reason — sea-floor sediment of the Tethys lifted into a mountain range.
- practice — not a real PYQ
The suture zone that marks the join between the Indian and the Eurasian plates in the Himalayan region is known as the:
- (a)Main Central Thrust
- (b)Indus–Tsangpo Suture Zone
- (c)Main Boundary Thrust
- (d)Himalayan Frontal Thrust
Answer(b) Indus–Tsangpo Suture Zone — it traces the closed Tethys ocean; the MCT, MBT and HFT lie south of it and are internal Himalayan thrusts, not the plate join.
- practice — not a real PYQ
Consider the following statements about continent–continent collision: 1. Neither of the colliding plates is subducted completely, because continental crust is too buoyant. 2. The convergence is absorbed mainly by folding, thrusting and crustal thickening. Which of the above statements is/are correct?
- (a)Only 1
- (b)Only 2
- (c)Both 1 and 2
- (d)Neither 1 nor 2
Answer(c) Both 1 and 2 — buoyant continental crust resists subduction, so the shortening goes into folds, thrust sheets and a thickened crust that rises isostatically. This is exactly how the Himalaya formed and is still forming.