Earth's inner core may have a hidden layered structure, study reveals

A team from the University of Münster has uncovered new details about Earth’s inner core. Their study suggests the solid centre may have a layered structure. The findings, published in Nature Communications, could explain why some earthquake waves travel faster along the planet’s axis than near the equator. The researchers, led by mineralogist Carmen Sanchez-Valle, focused on how iron crystals behave under extreme conditions. They created alloys of iron mixed with silicon and carbon, then exposed them to high pressure and temperature. These experiments mimicked the environment of Earth’s core, where iron dominates but lighter elements like silicon, carbon, and oxygen are also present.

During compression, the crystals developed a preferred alignment. This orientation was captured using a specialised X-ray technique. The team observed that such alignment could influence how seismic waves move through the core. Earth’s outer core is liquid, while the inner core is solid. For years, scientists have noted that certain earthquake waves travel 3 to 4 percent faster along the planet’s axis than along the equatorial plane. The Münster study proposes that this variation may stem from both the chemical makeup of the core and the way its crystals deform under pressure.

The results suggest that the inner core’s structure is more complex than previously thought. Differences in seismic wave speeds could be linked to the alignment of iron crystals and the presence of lighter elements. This research provides a clearer picture of the forces shaping Earth’s deepest layers.