Far below our feet is the inner core of the Earth. More than 5,000 kilometers below us. It is made of solid iron, very hot and very dense; It is surrounded by a molten nickel-iron outer core (the flux of which generates Earth’s magnetic field) and a rocky mantle that is practically solid but moves slowly over eons of time. Although it is usually presented to us as a round figure, the truth is that the core of the Earth does not tend to be round.
Each year, the solid iron inner core at the heart of our planet expands by approximately one millimeter as the lower regions of the Earth cool and solidify. A new study suggests that the Earth’s inner core grows asymmetrically , meaning faster on one side than the other, and the fastest growing area of the inner core is under the Banda Sea of Indonesia.
Specifically, the work probed this mystery using new seismic observations combined with geodynamic models and estimates of how iron alloys behave under high pressure. They found that the eastern inner core located under the Banda Sea in Indonesia is growing faster than the western side under Brazil.
Is the core of the Earth twisted?
No, we cannot say that it is crooked, thanks to the effect of Earth’s gravity. Gravitational forces distribute this new growth evenly through a progressive inner flow process, which maintains the spherical shape of the inner core. This means that the Earth is not in danger of tipping over.
But why is this happening?
The scientists focused on one piece of observable data about the Earth’s core: For some reason, seismic waves travel much faster from “north” to “south” through the core than from side to side. In some way, this must also be related to the way the mass accumulates in the core.
For now, the asymmetry itself remains unexplained, but it offers a solution to another long-standing conundrum: why the iron crystals in the inner core line up parallel to Earth’s North-South axis of rotation. Experts say that heat dissipation probably explains why the eastern side of Indonesia is adding more iron crystals much faster. Those crystals form and move rapidly toward the rest of the core, creating horizontally packed structures that account for the slower east-west seismic waves compared to the faster north-south seismic waves.
That is, on Earth, uneven growth is due to the rest of the planet absorbing heat more quickly from some parts of the inner core than others. Thus, it is likely that the dissipated heat is due to Indonesia being covered by a huge mix of islands and an extensive seabed, which is a key place where molten materials spew heat from inside the Earth.
Curiosity:
Did you know that the inner core of the Earth wasn’t discovered until 1936? Almost a century later, we are still trying to answer basic questions about when and how it first formed.
Referencia: Dynamic history of the inner core constrained by seismic anisotropy. Frost, D.A., Lasbleis, M., Chandler, B. et al. Nature Geoscience (2021).DOI:https://doi.org/10.1038/s41561-021-00761-w
