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There might be a core hidden inside the Earth’s core

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A study suggests that our planet’s “seed” – its solid core – could break down into two distinct layers. These conclusions, which still require confirmation, are consistent with the results of previous work.

Traditionally, we have all been taught that the Earth presents itself as a layered cake made up of a solid outer crust, a hot and viscous mantle, a liquid outer core, and a solid inner core. This knowledge has mainly been inferred from information disclosed by volcanic eruptions and other seismic waves. In other words, they were obtained through indirect means. But is it set in stone for all that? Not necessarily.

Again published works by Joanne Stephenson and her team from the Australian National University indeed suggest that the inner core of the Earth could actually have two separate layers.

Two different structural alignments

As part of this study, the team relied on a research algorithm that compared thousands of models of the Earth’s core with data collected from seismic waves over the past decades.

With these data in hand, the researchers focused on analysis of so-called “anisotropic” materials, whose composition changes according to their orientation. Conversely, we speak of isotropy when the physical properties of a material remain invariant, regardless of the direction.

In the study that interests us, variations in the composition of the materials of the inner core modify the properties of seismic waves. We can then study the anisotropy of the nucleus through these waves which then give indications on the internal composition of the Earth. Here, the algorithm developed by the researchers made it possible to highlight a variation in composition within this solid nucleus, and more precisely different structural alignments.

We found evidence that could point to a change in the structure of iron, possibly suggesting two separate cooling events in Earth’s history.“, Explains Joanne Stephenson. “The details of this great event are still a mystery, but we have added another piece to the puzzle of our knowledge of the Earth’s inner core.. It’s very exciting“, She continues. It could mean that we have to rewrite the manuals!“.

Earth is a four or five layer cake? Credits:

These new findings have yet to be confirmed. Unfortunately, “we are still limited by the distribution of earthquakes and global receptors and in particular at the polar antipodes“, Continues the geologist.

However, these conclusions agree with the results of previous work pointing to the strange behavior of certain seismic waves a priori incompatible with our “four-layer cake” model.


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