A recent study revealed that the construction of large dams since 1835 has shifted Earth’s rotational axis by over 1 meter. This phenomenon is referred to as True Polar Wander (TPW).
🔄 What is True Polar Wander (TPW)?
Definition: TPW refers to the rotation of Earth’s solid outer layer (crust and mantle) around its liquid outer core.
It plays a key role in helping Earth maintain rotational balance through mass redistribution.
🌊 Natural Causes of TPW:
TPW has traditionally been associated with natural factors such as:
Glacial melting Ice sheet melt Tectonic plate shifts Ocean swell
🏗️ How Human-Made Dams Drive TPW:
Reservoirs trap massive volumes of water that would otherwise remain in the oceans.
This shifts Earth’s mass inland, altering the balance and slightly changing the planet’s rotation.
The study also found that the shift was not smooth; it depended on the size and location of dams built over time.
⚠️ Effects of Shifting Poles:
Navigation Issues: Shifting poles can impact the accuracy of satellites and space telescopes, which rely on Earth’s stable rotation for precise positioning.
Longer Days: The length of a day on Earth is gradually increasing, and this shift is accelerating due to ongoing changes in mass distribution.
🧪 UPSC Prelims Style MCQ
Q. With reference to True Polar Wander (TPW), which of the following statements is/are correct?
TPW refers to the movement of Earth’s solid mass over its liquid outer core.
Construction of large dams causes mass redistribution that contributes to TPW.
TPW occurs only due to natural phenomena like glacial melting and tectonic activity.
Options:
a) 1 and 2 only
b) 2 and 3 only
c) 1 and 3 only
d) 1, 2 and 3
📝 (Correct Answer: a)
