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UPSC Prelims 2025, Question 33

The concept being tested: Polar ice redistribution and Earth's rotational axis.

Consider the following statements: Statement I: Scientific studies suggest that a shift is taking place in the Earth's rotation and axis. Statement II: Solar flares and associated coronal mass ejections bombarded the Earth's outermost atmosphere with tremendous amount of energy. Statement III: As the Earth's polar ice melts, the water tends to move towards the equator. Which one of the following is correct in respect of the above statements?

Options

  1. ABoth Statement II and Statement III are correct and both of them explain Statement I
  2. BBoth Statement II and Statement III are correct but only one of them explains Statement ICorrect answer
  3. COnly one of the Statements II and III is correct and that explains Statement I
  4. DNeither Statement II nor Statement III is correct

The answer: Both Statement II and Statement III are correct but only one of them explains Statement I

Earth's rotational axis genuinely drifts over time, a phenomenon geophysicists call polar motion. Satellite gravity data (from missions such as GRACE) has shown this drift accelerating since around 2000, and the leading driver is mass redistribution on the surface: as the Greenland and Antarctic ice sheets melt, the meltwater does not stay put near the poles but migrates towards the equator, following sea-level fingerprint patterns shaped by Earth's oblate form and its own changing gravity field. This shift in mass changes the planet's moment of inertia and nudges the spin axis, which is exactly why the statement about polar ice melt and equatorward water movement is both factually correct and the true explanation for the axial shift. Solar flares and coronal mass ejections are also real and well documented, dumping energy into the thermosphere and ionosphere and heating the upper atmosphere, but this process affects atmospheric drag on satellites, not the solid Earth's rotation axis, so it is correct as a fact but irrelevant as an explanation.

What UPSC was testing

The trap here is assuming that any true supporting statement automatically counts as an explanation. UPSC is testing whether aspirants can separate a factually correct but causally irrelevant statement (solar flares heating the ionosphere) from the one that actually drives the phenomenon in Statement I (mass redistribution from melting polar ice), a distinction that kills naive elimination strategies based only on statement truth-value.

How often this comes up

This concept has appeared 7 times in UPSC Prelims General Studies Paper I between 2015 and 2025 — in 2016, 2020, 2021, 2023 and 2025.

The option-by-option autopsy for this question — why each of the other three is wrong, and which neighbouring concept each one was built from — is in the app.