UPSC Prelims 2025 Q25: Evidences of Continental Drift — Explained
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.
- I and III only
- I and II only
- I, II and III
- II and III only
Answer: (c) I, II and III
Statement-wise explanation
- I: correct — This is the 'rocks of the same age across the oceans' evidence in NCERT Class XI (Fundamentals of Physical Geography, Ch. 4). Radiometric dating shows a belt of ancient rocks, about 2,000 million years old, on the Brazil coast that matches rocks in Western Africa. NCERT adds that the earliest marine deposits along the coasts of South America and Africa are Jurassic in age, so no ocean separated the two before then.
- II: correct — This is NCERT's 'placer deposits' evidence. The Ghana coast has rich placer deposits of gold but none of the source rock that the gold could have weathered out of. The gold-bearing veins are in Brazil. NCERT concludes that Ghana's gold came from the Brazil plateau when the two continents lay side by side.
- III: correct — This is NCERT's 'tillite' evidence. Tillite is sedimentary rock formed from glacial deposits. NCERT says India's Gondwana system of sediments has counterparts in six landmasses of the Southern Hemisphere and names Africa, the Falkland Islands, Madagascar, Antarctica and Australia. Matching glacial sequences on landmasses that are now far apart, some of them in the tropics, point to old climates and to the continents having drifted.
How to eliminate
Every statement here is a near-verbatim line from the NCERT Class XI list of evidence for continental drift: rocks of the same age across the oceans (I), placer deposits (II) and tillite (III). The statements contain no absolute words to rule them out, and each pair of statements appears in some option, so the option structure tells you nothing. Statement II is the trap. 'Gold in Ghana came from Brazil' sounds far-fetched, and candidates who have not read the chapter tend to drop it. Its logic still follows the drift idea: the gold sits in Ghana, the source rock sits in Brazil, so the two areas must once have been joined. A practical rule: when a statement describes a matching rock, mineral, fossil or glacial deposit on two coasts that now face each other across an ocean, it is almost certainly being offered as drift evidence. In the end this question tests whether you know the NCERT list. Remember five items: jigsaw fit, rocks of the same age, tillite, placer deposits and fossils.
Know more
Continental drift was proposed by the German meteorologist Alfred Wegener in 1912. He argued that all continents once formed a single supercontinent, Pangaea, surrounded by one mega-ocean, Panthalassa. Around 200 million years ago Pangaea split into Laurasia in the north and Gondwanaland in the south, and these later broke into today's continents.
Evidence for drift (NCERT list)
| Evidence | What it shows |
|---|---|
| Jigsaw fit | The shorelines of South America and Africa fit together, and the fit is best at the 1,000-fathom line of the continental shelf |
| Rocks of the same age | Brazil's ~2,000-million-year-old rock belt matches Western Africa's |
| Tillite | India's Gondwana glacial sediments have counterparts across the Southern Hemisphere |
| Placer deposits | Ghana has placer gold but no source rock; the gold veins are in Brazil |
| Fossils | Mesosaurus, a small reptile of shallow brackish water, is found only in South Africa and Brazil. Lemurs occur in India, Madagascar and Africa, which led to the idea of a land called 'Lemuria' |
Why the theory was doubted. Wegener said two forces moved the continents: the pole-fleeing force, linked to Earth's rotation, and a tidal force from the Sun and Moon. Both were far too weak. USGS notes that critics asked what force could push solid continents through the ocean floor.
What came next. Sea-floor spreading, supported by palaeomagnetic striping and young ocean-floor ages, and then plate tectonics in the 1960s supplied the mechanism. Under plate tectonics, whole lithospheric plates move, not just continents. India broke away from Gondwana and drifted north until it collided with Eurasia, which raised the Himalaya.
India link. The Gondwana system of Peninsular India holds most of the country's coal. The coal comes from Permian forests that grew while India was still part of Gondwanaland.
NCERT Concepts to Revise
- Continental drift theory: The question asks which observations count as evidence for Wegener's idea, so you need the theory's core claim first.
- Placer deposits: Statement II is about Ghana's gold. Knowing how placer deposits form and travel from a source rock is the key to judging it.
- Gondwana system: Statement III turns on what India's Gondwana system of sediments is and where its glacial layers came from.
- Gondwanaland: The southern supercontinent that would explain matching Gondwana sediments on several Southern Hemisphere landmasses.
- Pangaea: Pangaea is the starting point of drift. Brazil and West Africa sat side by side within it.
- Fossil evidence for continental drift: Fossils are the other big matching-across-oceans evidence in the same NCERT list, so expect them in a follow-up question.