Earth’s inner core may have an onion-like layered structure, new study reveals

01/04/2026 / By Kevin Hughes

Earth’s inner core is not uniform but has an onion-like layered structure, with varying chemical compositions at different depths. Silicon and carbon mixed with iron explain long-standing seismic anomalies.
Earthquake waves travel faster along Earth’s rotational axis than across the equator due to crystallized iron alloys aligning in specific directions—a phenomenon confirmed through high-pressure lab experiments.
Using diamond anvil cells and X-ray diffraction, researchers recreated core conditions (over 1 million atmospheres, 820°C), proving that iron-silicon-carbon alloys develop lattice-preferred orientation (LPO), matching seismic observations.
The inner core solidified gradually, concentrating lighter elements (silicon, carbon) toward outer layers, preserving a “chemical memory” of Earth’s formation and thermal history.
A chemically stratified core influences heat flow, convection in the outer core and Earth’s magnetic field stability—key factors in planetary habitability compared to Venus and Mars. Future research will explore oxygen and sulfur’s roles.

Scientists have uncovered evidence of chemical stratification in Earth’s core, explaining seismic anomalies and reshaping our understanding of the planet’s deepest layers.

Deep beneath Earth’s surface, the inner core—a solid ball of iron under crushing pressure—may be far more complex than previously thought. A groundbreaking study published in Nature Communications suggests that Earth’s inner core is not a uniform sphere but instead has an onion-like layered structure, with varying chemical compositions at different depths.

Seismic anomalies finally explained

For decades, seismologists have puzzled over why earthquake waves travel at different speeds depending on their direction through the inner core—a phenomenon known as anisotropy. Observations show that compressional waves move 3% to 4% faster along Earth’s rotational axis than across the equatorial plane. Even more perplexing, this anisotropy is stronger in the central region of the inner core and weaker toward the outer edges.

Now, a research team from the University of Münster in Germany may have cracked the mystery. By simulating extreme inner-core conditions in the lab, the researchers found that silicon and carbon mixed with iron could explain these seismic discrepancies. Their study was published in Nature Communications.

Lab experiments mimic the core’s extreme conditions

Since drilling to Earth’s core is impossible, the team recreated its environment using diamond anvil cells, which compress microscopic samples to pressures exceeding one million atmospheres while heating them to 820 C (1,508 F).

Using X-ray diffraction at Germany’s PETRA III synchrotron facility, they analyzed how iron alloys containing silicon and carbon deformed under stress. The key discovery? The alloys developed a lattice-preferred orientation (LPO), meaning their crystal structures aligned in specific directions—just as seismologists had inferred from earthquake data.

“We were able to decode the LPO via X-ray diffraction perpendicular to the compression axis,” said Dr. Efim Kolesnikov, the study’s lead author.

A layered core like an onion

The experiments revealed that pure iron exhibits strong anisotropy, matching seismic observations from the deepest part of the inner core. Meanwhile, iron-silicon-carbon alloys showed weaker anisotropy, aligning with data from the outer layers.

This suggests that Earth’s core crystallized gradually, with lighter elements like silicon and carbon becoming more concentrated toward the outer regions as the core solidified from the center outward. “The depth-dependent anisotropy pattern observed in the Earth’s inner core may result from chemical stratification of silicon and carbon following core crystallization,” the researchers concluded.

BrightU.AI‘s Enoch explains that anisotropy, derived from the Greek words “an” (against) and ‘isos’ (equal), refers to the property of a material or system that exhibits different properties when measured in different directions. This concept is ubiquitous in nature and plays a crucial role in various scientific disciplines, including physics, materials science and biology.

Anisotropic materials or systems exhibit different physical or chemical properties when measured along different axes or directions. This directional dependence is the defining characteristic of anisotropy.

Implications for Earth’s magnetic field and evolution

Understanding the inner core’s structure isn’t just academic—it has real-world consequences. The core plays a crucial role in generating Earth’s magnetic field, which shields the planet from harmful solar radiation. A chemically layered core could influence heat flow and convection patterns in the liquid outer core, affecting the magnetic field’s stability over geological time.

Moreover, these layers act as a hidden archive, preserving clues about Earth’s thermal and chemical evolution over billions of years.

Future research directions

While this study provides compelling evidence for a layered core, questions remain. The inner core likely contains other elements like oxygen and sulfur, which weren’t tested here. Future experiments will need to explore how these additional components affect seismic behavior.

As scientists continue refining seismic models and lab techniques, Earth’s deepest secrets—locked in its iron heart—may soon be fully unlocked.

Watch this video about the Earth stopping and reversing direction.

This video is from the Evolutionary Energy Arts channel on Brighteon.com.

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