Researchers affiliated with the University of California, Berkeley, have successfully generated the most comprehensive global map to date detailing the deformations present in Earth’s deepest mantle layer—situated approximately 2,900 kilometers down, right at the boundary with the planet’s core. This study’s findings were featured in the publication The Seismic Record.
The foundation of this research lies in an immense dataset comprising over 16 million seismograms sourced from 24 different global monitoring stations. The scientists focused on tracing how seismic waves generated by earthquakes traveled through the mantle, penetrated the Earth’s core, and subsequently returned. The speed at which these waves travel shifts based on their orientation—a phenomenon known as seismic anisotropy. It is precisely these variations that allow scientists to pinpoint where rock deformation is occurring. Consequently, the investigators were able to cover nearly 75% of the lower mantle in their observations.
Anisotropy was identified in roughly two-thirds of the regions examined. A majority of these anomalies correspond to areas where geodynamic models project ancient tectonic plates descended. Over millions of years, lithospheric plates subducted deep into the Earth, sinking thousands of kilometers until they reached the lower mantle. Deformation proved most significant precisely in these locations where sunken slabs accumulated near the core boundary. “While this finding aligns with predictions from geodynamic models, it’s not entirely unexpected,” acknowledged Jonathan Wolff, the study’s lead author. “However, the sheer magnitude of what we’ve visualized using our methods has never been demonstrated at this scale before.”
The source of this anisotropy could be twofold: either it represents a legacy structure inherited from the Earth’s surface plates, or it stems from intense deformation caused by their interaction with the core boundary under immense pressures and heat. According to the research team, the aggregated data collected will serve as a rich source for novel discoveries regarding our planet’s deep interior for many years to come, as reported by Science XXI.
About the Author
