Question 42 from UPSC CSE 2025 - Environme nt & Ecology

Question

Consider the following statements:
1. Scientific studies suggest that a shift is taking place in the Earth's rotation and axis.
2. Solar flares and associated coronal mass ejections bombarded the Earth's outermost atmosphere with a tremendous amount of energy.
3. 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?

IASCODEX · Accepted Answer

Correct Option: B. Both Statements II and III are correct but only one of them explains Statement I

Strategy: Evaluate which statements are factually correct by linking them to established scientific knowledge. Recognize that solar flares (II) do indeed impact Earth's outer atmosphere, while melting polar ice (III) causes mass redistribution, shifting Earth's axis and affecting its rotation. Both II and III are factually correct. However, only the process described in III—mass redistribution from melting ice—directly explains observed shifts in Earth's rotation and axis. Hence, select the option where both are correct, but only one explains Statement I.

Key Info: Earth's rotation and its axis are not fixed; they exhibit gradual changes over time due to redistribution of mass within the planet. This shift in the planet's rotation axis, or 'polar motion,' results from processes such as glacial melting and movement of water masses.

- Scientific Findings: Studies using satellite and geodetic observations show that melting of polar ice—especially in Greenland and Antarctica—redistributes water from the poles to equatorial regions and oceans, causing measurable shifts in Earth's spin axis and a gradual increase in the length of the day. This is a documented outcome of climate change-driven ice loss and groundwater depletion. Polar motion has shifted by approximately 10 meters over the last 120 years, as per NASA and international geophysical measurements.

- Solar Flares and Coronal Mass Ejections (CMEs): Solar flares and CMEs expel vast amounts of charged particles and energy, impacting Earth's magnetosphere and upper atmosphere (thermosphere and ionosphere). This can cause temporary atmospheric expansion, affect satellite orbits, disrupt radio and GPS communications, and trigger auroras. However, these do not impart a sustained force or mass redistribution sufficient to alter Earth's rotation or axial orientation at a measurable scale. The energy from such events is largely shielded by Earth's magnetic field and does not directly influence polar motion or overall planetary rotation.

- Melting Polar Ice and Mass Redistribution: When ice at the poles melts, the resulting water is redistributed mainly toward lower latitudes (closer to the equator) via ocean currents. This mass movement alters the Earth's moment of inertia, leading to a wobble or drift in the axis of rotation—a phenomenon comparable to the behavior of a slowing figure skater extending arms. This phenomenon is rooted in the principles of conservation of angular momentum.

- Earth's Axis and Rotation: The geographic North-South axis about which the Earth spins is subject to natural and anthropogenic changes. Redistribution of mass—whether from mantle convection, atmospheric, hydrological, or cryospheric changes—can result in observable movements of the axis (Chandler wobble) and changes in the length of the day.

IASCODEX · Answer

Option A: Both Statements II and III are correct and both of them explain Statement I

IASCODEX · Answer

Option C: Only one of Statements II and III is correct and that explains Statement I

IASCODEX · Answer

Option D: Neither Statement II nor Statement III is correct