Earth’s inner core has a core of its own, researchers find

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A team of scientists from University of Illinois in US and Nanjing University in China have claimed discovery of an inner core within Earth’s core which they say could shed light on how our planet has evolved.

The latest discovery has been attributed to a novel way of using earthquake-reading technology by analysing seismic waves, the researchers gathered data not from the initial shock of an earthquake, but from the waves that resonate in the earthquake’s aftermath.

Equating the earthquake to a hammer striking a bell, researchers say that they analysed the clear tone of that resonates after a bell strike. The researchers revealed that the seismic sensors collect a coherent signal in the earthquake’s coda as it is much clearer than the ring itself.


“The basic idea of the method has been around for a while, and people have used it for other kinds of studies near the surface. But we are looking all the way through the centre of the Earth,” says Xiaodong Song, a professor of geology at the University of Illinois.

Researchers discovered a distinct inner-inner core that is about half the diameter of the whole inner core. According to researchers, the iron crystals in the outer layer of the inner core are aligned directionally, north-south; however, in the inner-inner core, the iron crystals point roughly east-west.

On top of the different alignment, researchers say that the crystals behave differently from their counterparts in the outer-inner core. This means that the inner-inner core could be made of a different type of crystal, or a different phase, researchers said.

“Even though the inner core is small – smaller than the Moon – it has some really interesting features,” says Song. “It may tell us about how our planet formed, its history, and other dynamic processes of the Earth. It shapes our understanding of what’s going on deep inside the Earth,” Song said.

Researchers added that because there are two regions distinctly different from one another, it shows that the inner core has been evolving.

“For example, over the history of the Earth, the inner core might have had a very dramatic change in its deformation regime. It might hold the key to how the planet has evolved,” Song said.

The research is published in the journal Nature Geoscience.