The Secrets of Earth’s ‘Surprisingly Soft’ Inner Core

By Ehtesham

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When we think of Earth’s core, it’s easy to envision a solid, immovable sphere of iron, unyielding in the face of immense pressure. This longstanding belief was disrupted in 2021 when seismic waves unveiled puzzling inconsistencies within the inner core, transforming our understanding of this hidden world.

Now, a new study takes us on a journey through the core’s mysteries, suggesting that hyperactive atoms may be the key to its surprising softness.

Heart of Our Planet

At the heart of our planet lies the inner core, a massive spherical structure primarily composed of iron that extends approximately 760 miles beneath our feet.

This ancient core, dating back at least 1 billion years, is surrounded by the tumultuous outer core, a dynamic sea of liquid metals. Beyond that, a vast layer of molten rock known as the mantle envelops the core, creating a boundary just below Earth’s solid crust.

The inner core’s position within this geologic layer cake subjects it to immense pressure, leading scientists to initially assume it was a solid entity with iron atoms locked in place, forming a colossal hexagonal lattice.

Mushy Hidden World

However, the seismic revelations of 2021 challenged this conventional wisdom. Earth’s core, once thought of as an unwavering mass, was suddenly described as a “mushy hidden world.” The discrepancies within the inner core puzzled experts. What caused this unexpected softness?

Several theories emerged. One suggested that swirls of liquid iron were entrapped within the core, altering its characteristics. Another intriguing idea was the existence of a “superionic state,” where atoms from elements like carbon and hydrogen constantly moved through the lattice of iron atoms in the core.

Hyperactive Atoms

The latest study, published in the journal Earth, Atmospheric and Planetary Sciences on October 2, introduces a fresh perspective on the inner core’s enigmatic behavior. Instead of liquid iron swirls or a superionic state, it proposes that hyperactive iron atoms might hold the key.

To investigate this hypothesis, the researchers recreated the intense pressure conditions within the inner core in a laboratory setting. They closely observed how iron atoms behaved under these extreme conditions and fed this data into a computer-learning program, which led to the creation of a simulated “supercell.”

This virtual core allowed the team to gain insight into how the iron atoms moved within the ostensibly rigid structure.

The results of the supercell simulations were nothing short of astonishing. They unveiled that the iron atoms within the inner core possess an unexpected degree of mobility.

Jung-Fu Lin, a geophysicist at the University of Texas at Austin and a study co-author, noted that these atoms can “move much more than we ever imagined.”

The supercell simulations displayed a fascinating phenomenon: atoms shifting collectively within the lattice, maintaining the core’s overall structure. Imagine dinner guests at a table who change seats without adding or removing chairs – this is a form of movement known as “collective motion.”

Lin explained that this increased atomic movement has a profound impact on the inner core’s properties. It renders the core “less rigid” and more susceptible to shear forces, ultimately making it “surprisingly soft.”

Earth’s Mysteries

These findings not only challenge our fundamental understanding of the inner core but also promise to shed light on various inner core mysteries. One such enigma is the role of the inner core in generating Earth’s magnetic field, a fundamental aspect of our planet’s geology and its influence on the natural world.

Jung-Fu Lin believes that these discoveries are pivotal for unraveling the dynamic processes and evolution of Earth’s inner core. Our understanding of this hidden realm has taken a remarkable turn, and as we delve deeper into its complexities, we inch closer to unlocking the secrets that lie at the heart of our planet.


What is Earth’s inner core, and what is it composed of?

Earth’s inner core is a massive spherical structure primarily composed of iron. It extends approximately 760 miles beneath the Earth’s surface.

Why was the inner core long believed to be completely solid and unyielding?

The immense pressure at the Earth’s core led experts to believe that the inner core was solid and that iron atoms were held in place within a hexagonal lattice.

What disrupted the conventional understanding of the inner core in 2021?

Seismic waves from earthquakes revealed inconsistencies within the inner core, prompting scientists to reconsider its properties.

What was the previous explanation for the inner core’s softness?

Previous theories suggested that swirls of liquid iron trapped within the core or the existence of a “superionic state” might explain its softness.

How did the recent study propose an alternative explanation for the inner core’s properties?

The study suggested that hyperactive iron atoms moving within their lattice structure might be responsible for the inner core’s surprising softness.