French geophysicists from Gustave Eiffel University in Paris have made an intriguing discovery: between 2006 and 2008, an unusual mass shift occurred at the boundary between Earth’s core and mantle, about 3,000 km deep. The finding, described in Geophysical Research Letters, could shed light on the planet’s internal processes and their influence on the magnetic field and seismic activity.

What Did Scientists Find?

The study is based on data from the GRACE (Gravity Recovery and Climate Experiment) satellite mission, carried out by the U.S. and Germany. GRACE measures Earth’s gravitational anomalies, allowing researchers to track mass distribution changes. Scientists found that a mass displacement occurred at the boundary between the liquid outer core and the lower mantle, causing a local change in the gravitational field. The deformation amplitude was estimated at about 10 cm.

This shift is linked to the transformation of perovskite rocks — minerals that form under extreme pressure in the lower mantle. Perovskites, rich in magnesium and iron, are considered a key component of the mantle at depths of 660–2,900 km. Their properties are confirmed by both laboratory experiments and seismic data: the speed of wave propagation in this zone matches perovskite structures.

Why Did This Happen?

The exact reasons for the shift remain unclear. Scientists propose several hypotheses:

  • Core dynamics: movement of the liquid outer core, composed of molten iron and nickel, may have triggered the deformation.
  • Mantle changes: the transformation of perovskites may be linked to local temperature or pressure variations.
  • Geodynamic processes: the shift may be part of larger mantle flows that influence plate tectonics.

The mass displacement may also have affected Earth’s magnetic field, producing anomalies detected by magnetometers. This is significant because the magnetic field shields the planet from solar wind and cosmic radiation.

Why Is the Discovery Important?

The finding is crucial for geoscience because it helps with:

  • Understanding Earth’s structure: refining models of the lower mantle and outer core.
  • Geodynamics: linking mass shifts to processes that cause earthquakes and volcanism.
  • Magnetic field research: explaining the field’s instability, including its weakening in certain regions such as the South Atlantic Anomaly.

Researchers emphasized that this discovery is a step toward understanding how internal processes shape Earth and its magnetic field. GRACE data show that even small shifts at depth can have global consequences.

What’s Next?

Scientists plan to continue analyzing data from GRACE-FO (the follow-up to GRACE) and seismic observations to:

  • Clarify the causes of the mass shift.
  • Assess its impact on tectonic processes.
  • Develop models linking the mantle and core to surface phenomena.

These studies may also help predict magnetic anomalies that affect satellites and navigation systems.

In Short…

A mass shift at the Earth’s core-mantle boundary, detected between 2006 and 2008, has revealed the complexity and dynamism of our planet’s interior. The 10 cm deformation at a depth of 3,000 km, linked to perovskites, may influence both the magnetic field and geodynamics. Based on GRACE mission data, the research opens a new chapter in Earth studies, showing that even deep processes leave a mark at the surface.