UPSC CURRENT AFFAIRS – 07th April 2025

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What is the Hadean Protocrust?

Why in News?

A new study has challenged the belief that geochemical signatures associated with plate tectonics originated only after subduction began, suggesting they may have existed in Earth’s Hadean protocrust.

Introduction

A new international study led by Macquarie University, Australia, has challenged the long-held assumption that unique geochemical signatures in Earth’s crust are solely a result of plate tectonic processes.
The study finds that these signatures may have existed even before subduction began, during the Hadean aeon.

What is the Hadean Protocrust?

The Hadean protocrust refers to the earliest form of Earth’s crust that formed during the Hadean aeon, which spans from Earth’s formation (~4.6 billion years ago) to 4 billion years ago. During this time:

The Earth’s surface was partially molten.
Heavy meteorite bombardment and rampant volcanism created a hellish environment.
Cooling of the magma ocean led to the formation of the first crustal fragments, though they were unstable and dynamic.
Over time, thicker and more stable parts of this early crust formed the first continental blocks.

Plate Tectonics and Geochemical Signatures

As the lithosphere cooled and thickened:

These early continental blocks began moving atop the asthenosphere — a semi-fluid layer extending about 400 km beneath the surface.
Interactions like subduction (one plate diving beneath another) and collision generated chemical signatures in rocks, often used to trace the history of tectonic activity.

Traditionally, these chemical markers were believed to have originated only after the onset of modern plate tectonics.

New Findings: Rewriting the Geological Timeline

The new study, combining geochemical modelling and lab-based simulations, has found that:

The geochemical signatures previously attributed to subduction-related processes were already present in the Hadean protocrust.
This suggests that plate tectonic-like processes or their chemical fingerprints may have pre-dated the onset of classical plate tectonics.

Implications and Future Directions

This discovery questions a foundational principle in geology — that subduction-driven plate tectonics are responsible for certain geochemical markers in Earth’s crust.
It may indicate that proto-tectonic or non-subduction processes during the Hadean era could explain early chemical patterns.
The findings need further validation by independent research and peer review before they can be integrated into mainstream geological theory.

Conclusion

If confirmed, this research could significantly reshape our understanding of early Earth dynamics, including the origin of continents and the onset of plate tectonics. The study highlights the evolving nature of scientific inquiry and the importance of revisiting established assumptions with new data and methods.