Earth's inner core is slowing down and changing shape 🌍

The Earth's inner core, long considered a solid and stable sphere, may be quite different. A recent study suggests that its surface is undergoing structural transformations, challenging our understanding of this mysterious region.


By analyzing decades of seismic data, researchers from the University of Southern California have discovered that the surface of the inner core appears to deform under the influence of the outer core. These changes, observed for the first time, could explain some variations in the rotation of the inner core and even influence the length of days on Earth.

A moving inner core

The inner core, located about 3,100 miles (5,000 km) below the surface, is traditionally described as a solid ball of iron and nickel. However, new data shows that its outer layer may be more malleable than expected. This discovery is based on the analysis of seismic waves from repeated earthquakes near the South Sandwich Islands.

The researchers used enhanced resolution techniques to study seismic signals. They observed anomalies in the waves, suggesting deformations on the surface of the inner core. These deformations could be caused by turbulent interactions with the molten outer core.

The influence of the outer core

The outer core, composed of liquid iron and nickel, is known for its role in generating Earth's magnetic field. Until now, its impact on the inner core was poorly understood. The study reveals that the turbulent movements of the outer core could disrupt the surface of the inner core, causing changes in shape.

These disturbances could also explain the gradual slowdown in the rotation of the inner core observed since 2010. Although these changes are imperceptible on the surface, they could influence Earth's overall rotation and the length of days.

Towards a better understanding of Earth's core

This study opens new perspectives for understanding the deep dynamics of Earth. Researchers hope that these findings will allow for a better grasp of the interactions between the inner and outer core, as well as their impact on Earth's magnetic field and geodynamics.

The results, published in Nature Geoscience, highlight the need for further research to explore these phenomena. Additional data could reveal other unexpected aspects of this still largely unknown region.

To go further: How do we study Earth's core?

Direct observation of Earth's core being impossible, scientists use indirect methods. The analysis of seismic waves allows us to deduce its structure and composition. As these waves pass through different layers, they are deflected or stopped, providing clues about the nature of the materials encountered.

Laboratory experiments complement these observations. By reproducing the extreme pressures and temperatures of the core, researchers study the behavior of iron-nickel alloys. Sophisticated instruments, such as diamond anvil cells, allow exploration of these extreme conditions.

Studies on meteorites also enrich our knowledge. Some come from differentiated asteroids with a metallic core, similar to Earth's. Their chemical composition provides clues about the elements present in Earth's depths.

Numerical models play an essential role. By combining seismic, experimental, and geochemical data, they simulate the internal dynamics of the core. These simulations help refine our understanding of its role in generating Earth's magnetic field.