Question 87 from UPSC CSE 2025 - Geography

Question

Which of the following are the evidences of the phenomenon of continental drift?
I. The belt of ancient rocks from the 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:

Accepted Answer

Correct Option: C. I, II and III

Strategy: To answer correctly, look for classic geological correlations across continents, a hallmark of continental drift evidence. The match of ancient rocks between Brazil and West Africa (Statement I) is a textbook indicator. Gold deposits in Ghana traceable to Brazil's plateau (Statement II) point to continental proximity in the past. The widespread Gondwana sediment systems (Statement III), found across Southern Hemisphere continents, show strong paleogeographic linkage. All three statements directly reference features used historically to support Wegener's theory.

Key Info: Continental Drift Theory, proposed by Alfred Wegener, postulates that continents were once joined as a supercontinent (Pangaea) and later drifted apart. Several geological and paleontological evidences support this:

- Ancient Rock Correlation: The eastern coast of Brazil and the western coast of Africa have rock belts of similar age (~2 billion years), composition, and structure. These 'cratonic belts' provide compelling lithological continuity, supporting previous land connection before the opening of the Atlantic Ocean.

- Gold Deposits of Ghana and Brazil: The coastal placer gold deposits in Ghana lack local source rocks, while Brazil's plateau contains gold-bearing veins. This suggests that when South America and Africa were contiguous, erosion and river systems transported gold-rich sediments from Brazil to the present-day Ghana coastline. Such mineralogical continuity across present oceans indicates continental juxtaposition in the geological past.

- Gondwana Sediments: The Gondwana Supergroup is a sequence of sediments deposited during the late Paleozoic to Mesozoic eras, extensively spanning India, South America (Brazil, Argentina), Africa (South Africa), Antarctica, Australia, and Falkland Islands. These sediments are typified by similar coal formations, glacial tillite (indicative of ancient glaciation), and floral/fossil assemblages, implying connected ecological and climatic conditions before the breakup of Gondwanaland. The glacial deposits (tillite) in these diverse landmasses serve as critical evidence of former physical proximity and a similar paleoclimate.

- Additional Evidences: Other lines include the matching of mountain ranges (e.g., Appalachian and Caledonian chains), fossil distribution (similar extinct species found across now-separated continents), and paleoclimatic indicators such as coal deposits in Antarctica and glacial traces in now-tropical regions.

The continental drift theory is foundational to modern plate tectonics, with the above geological features remaining central to its continued validation.

Answer

Option A: I and III only

Answer

Option B: I and II only

Answer

Option D: II and III only