Previous Year Question
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 a 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?
Correct Answer: B
Detailed Solution
Statement I is correct. Earth’s rotation is not perfectly constant. Redistribution of mass on Earth’s surface and within its interior can produce small changes in its rotational speed and the position of its rotational axis. Melting ice sheets and glaciers, redistribution of ocean water, groundwater depletion and movement within Earth’s mantle can influence these changes.
Statement II is correct, but it does not explain Statement I. Solar flares and coronal mass ejections release energy, magnetic fields and charged particles into space. When directed towards Earth, they can affect the magnetosphere and upper atmosphere, producing space-weather effects such as auroras, radio-communication disturbances and impacts on satellites. However, they do not redistribute Earth’s mass in a manner that explains the changes in rotation and axis mentioned in Statement I.
Statement III is correct and explains Statement I. When polar ice sheets and glaciers melt, water is transferred from high latitudes to the oceans, with a considerable part of this mass being redistributed towards equatorial regions. This changes Earth’s moment of inertia. Just as a rotating skater slows down after extending the arms, movement of mass from the poles towards the equator can cause a minute slowing of Earth’s rotation and a very small increase in the length of the day. Uneven redistribution of mass can also contribute to the movement of the rotational axis, known as polar motion.