📘 IAS Prelims 2025 — GS-I Q.33 | Classroom Explanation

(Environment & Ecology)

📌 Question

Q.33) 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?

(a) Both Statements II and III are correct and both of them explain Statement I
(b) Both Statement II and Statement III are correct but only one of them explains Statement I
(c) Only one of the Statement II and III is correct and that explains Statement I
(d) Neither Statement II nor Statement III is correct

✅ Correct Answer: (b)

🧑‍🏫 Classroom Explanation

This question tests understanding of Earth system science, particularly planetary rotation, axis shift (polar motion), and climate-induced mass redistribution, a rising UPSC area.

🔍 Key Concept: Why Earth’s Axis and Rotation Are Changing

Recent NASA-funded studies using over 120 years of data show that:

• Earth’s spin axis is shifting
• Earth’s rotation is slowing slightly
• Days are becoming marginally longer

These changes are primarily linked to redistribution of mass on Earth.

🔍 Statement-wise Analysis

✅ Statement I: Correct

• Scientific studies confirm:

• Earth’s axis has shifted by ~10 metres (30 feet) since 1900
• Length of day is increasing slightly

• Causes include:

• Melting ice sheets
• Groundwater depletion
• Rising sea levels

➡️ Statement I is correct.

❌ Statement II: Correct but NOT explanatory

• Solar flares and coronal mass ejections:

• Release large amounts of energy
• Affect thermosphere, satellites, radio communication, power grids
• Cause auroras

• However:

• Earth’s magnetic field deflects most energy
• They do not significantly alter Earth’s rotation or axis

➡️ Statement II is correct factually, but does not explain Statement I.

✅ Statement III: Correct and explanatory

• As polar ice melts:

• Mass shifts from poles toward equator
• This redistributes Earth’s mass

• Physics analogy:

• Like an ice skater spreading arms → rotation slows
• Earth’s moment of inertia increases

• Consequences:

• Polar motion (axis wobble)
• Lengthening of the day

➡️ Statement III directly explains Statement I.

🔗 Cause–Effect Logic (UPSC Core)

• Statement I → Observed phenomenon
• Statement II → Unrelated driver (space weather)
• Statement III → Actual causal mechanism

➡️ Both II and III are correct, but only one explains Statement I.

🧮 Logical Elimination (UPSC Style)

• II → Correct, but non-causal ❌
• III → Correct and causal ✅

➡️ Correct option: (b)

🎯 Final Answer

✅ Correct Answer: (b)

📦 Info Box — Extra Points (Prelims Value Add)

• The phenomenon is called Polar Motion
• Related concepts:

• Length of Day (LOD) variation
• Moment of Inertia
• Glacial Isostatic Adjustment

• Major contributors:

• Greenland ice sheet melt
• Antarctic ice loss
• Groundwater extraction

• UPSC Trap Alert:

• Solar activity affects atmosphere, not Earth’s spin
• Climate-induced mass redistribution is the key driver

📍 GS Mapping

GS Paper III
Theme: Environment, Climate Change, Earth System Science
Nature: Conceptual + Current Scientific Studies