October 2023

2023-10-08 17:15:05
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As of: October 8, 2023, 7:15 p.m

By: Tanja Banner

Split

The earth is made up of different layers. From outside to inside: Earth’s crust, (upper and lower) mantle, outer core and inner core. (Symbolic image) © IMAGO/Zoonar.com/Cigdem Simsek

High temperatures and enormous pressure ensure that the Earth’s inner core is solid – according to the common theory. But apparently that’s only partially true.

Austin – Nowhere else on earth are temperatures and pressures as high as those within it. The pressure presses the iron atoms inside the Earth tightly together, creating a solid inner core. But even under these extreme conditions, there is still room for movement, as a research team is now showing.

The researchers from the USA and China have found that certain groups of iron atoms in the Earth’s inner core can move quickly. They are apparently able to swap positions in a split second while maintaining the iron’s underlying metallic structure. This type of movement is known as “collective movement”. In everyday life you can see them in flocks of birds, herds of animals, but also in crowds or in car traffic.

Atoms in the Earth’s inner core can move surprisingly quickly

Back to the Earth’s core: Researchers cannot study it directly because it is too hot inside the Earth and the pressure is too high. But using laboratory tests and theoretical models, the research team still found evidence that the atoms in the Earth’s inner core move much more than previously thought. These results might help understand a number of intriguing properties of the Earth’s core that have long puzzled scientists – such as how exactly the Earth’s magnetic field is created.

“Now we know the fundamental mechanism that will help us understand the dynamic processes and evolution of the Earth’s interior,” says Jung-Fu Lin (University of Texas), one of the lead authors of the study in the specialist journal Proceedings of the National Academy of Sciences published became.

Miniature version of Earth’s core shows ‘collective movement’ of iron atoms

To come to this conclusion, the American-Chinese team recreated a miniature version of the Earth’s core in the laboratory. The first step was to shoot a small iron plate with a fast-moving projectile. The researchers obtained data on temperature, pressure and speed, which were then entered into a computer model that uses machine learning to simulate atoms in the Earth’s interior.

With the help of artificial intelligence, a “supercell” of around 30,000 atoms was created in the computer, which the research team now used to, among other things, predict the properties of the atoms more precisely. What the team observed was unexpected: groups of atoms moved and swapped places, while the underlying hexagonal structure of the atoms was maintained.

Inside the Earth there is a solid inner core surrounded by a liquid core. (Archive image) © dpa/EUMETSAT

Earth’s inner core is softer and more malleable than research expects

This unexpected movement of atoms might explain why seismic measurements of the Earth’s inner core show that it is much softer and more malleable than would be expected at the high pressure, says the research team. Recently, another research team suggested that liquid iron might be trapped in the Earth’s inner core.

Youjun Zhang (Sichuan University), co-author of the current study, explains: “The big discovery we have made is that solid iron deep within the Earth becomes surprisingly soft because its atoms can move much more than we can ever imagined. This increased movement makes the inner core less rigid and weaker to shear forces.” (tab)

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