Scientists Find Earth's Core Is Growing 'Lopsided' For Reasons Unknown

This strange discovery might have solved a 30-year-old mystery.
Derya Ozdemir

The soil underneath our feet is holding a brewing mystery: Earth's inner core, consisting of solid iron, is growing 'lopsided,' expanding faster on one side than the other for unknown reasons, according to a recent research by seismologists at the University of California, Berkeley.

The Earth may be more than 4 billion years old, but its inner core is far younger, with geologists believing it to have formed between half a billion and 1.5 billion years ago. The inner core holds a widely known, 30-year mystery about it, which can only be seen when monitoring seismic waves flowing through it: Waves move through the core significantly faster when they're traveling between the north and south poles than when they're traveling across the equator, and while that's really interesting, scientists didn't have an explanation as to why that was happening, according to Live Science.

This new revelation, which provides a suitable answer, comes following scientists analyzing the seismic waves traveling through the core. The study, published in the journal Nature Geoscience, examined computer models of the core's growth over the last billion years.

The researchers found that one half of the sphere, the eastern half under Indonesia's Banda Sea, accumulates 60 percent more iron crystals than its western counterpart, which lies underneath Brazil.

"The west side looks different from the east side all the way to the center," said Daniel Frost, a seismologist at the University of California, Berkeley, who co-authored the new study. "The only way we can explain that is by one side growing faster than the other."

The researchers found that heat is getting removed at a faster rate under Indonesia than it is from Brazil in the West, and that faster cooling on one side is likely to speed up the creation of iron crystals and core expansion on that side. So, since the core is losing heat faster under Indonesia than it is under Brazil, this messes with the seismic waves passing through it.

The researchers don't know why iron crystals are developing irregularly in the inner core, but the explanation could be possibly found in the layers above it. 

Furthermore, the team thinks that this "lopsided" characteristic of the core likely began as soon as the core developed. You'd think that after all this time, the inner core's form would be anything but spherical, but that isn't the case. Because of this, researchers believe gravity has been a key player in balancing the situation by directing the newly formed iron crystals towards the western section of the core, thus maintaining the spherical character of the core, which is growing in radius at a rate of 1 mm per year.

Another puzzling factor is whether or not the asymmetrical cooling in the core is affecting Earth's magnetic field, which extends from the Earth's interior out into space and interacts with the solar wind. The current magnetic field is driven by the flow of liquid iron in the outer core, which is in turn driven by heat lost from the inner core.

If the inner core is losing more heat in the east than the west, the outer core will migrate to the east as well, and whether this affects the strength of the magnetic field is a question waiting to be answered. Frost and a group of researchers are now looking into the answer.

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