Strange behaviour of Earth's core reveals a mystery inside our planet

Strange behavior of the Earth's core reveals a secret in our planet
Scientists have discovered a secret in the center of the earth. The massive iron core of our planet cools faster on one side than on the other, and no one knows why.
The interior of the earth is arranged in layers. Moving down from the surface is the rocky crust and mantle, the outer core of liquid nickel-iron and the inner core of solid nickel-iron. Crushed under the full weight of the rest of the planet around it, the inner core is experiencing pressure over 3.5 million times greater than the air pressure we experience here on the surface. This intense pressure is accompanied by strong warming. The temperature of the inner core is around 5,200 ° C - almost as hot as the surface of the sun.
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This artist's impression shows the interior of the earth with its various layers. Credit: Naeblys / Getty Images
As the heat from the solid core radiates outwards, it is absorbed by the liquid outer core, which keeps the metal moving and creates the earth's protective magnetic field. At the same time, the loss of heat from the core causes more iron to solidify around it, causing it to grow by about 1 millimeter every year.
However, there is something unusual about this process.
A research team led by Dr. Daniel Frost, a seismologist at the University of California Berkeley, found that seismic waves behave very strangely when they pass the inner core.
These seismic waves are created by the numerous earthquakes that occur near the surface of the earth. Since the waves are picked up by different seismic monitors around the world, the differences in the time it takes for waves from an earthquake to reach different monitors can tell us two things. First, because these waves move rapidly through the crust, seismologists can triangulate exactly where the earthquake occurred. Second, these waves also travel through the interior of the planet, moving at different speeds depending on the type of material they pass through. Thus they can give us a reasonably accurate picture of the inner structure of the earth.
Seismic waves moving through the earth move at different speeds through the materials they encounter. On their way from the mantle to the liquid outer core, the waves are deflected, creating a "shadow zone" in the seismic data received at the surface. Photo credit: US Geological Survey / Scott Sutherland
Since the inner core is a huge massive metal ball, seismic waves that reach it should pass at the same speed no matter which direction they come from. However, Frost and his colleagues found that this is not the case.
In a new study published in early June, they showed that waves traveling between the poles travel through the core faster than those traveling east to west.
Crystals in the Earth's core - Daniel Frost
A section of the earth's interior shows the solid iron core (red), which slowly grows due to the freezing of the liquid iron core (orange). Seismic waves cross the earth's inner core faster between the north and south poles (blue arrows) than across the equator (green arrow). Photo credit: Daniel Frost
The reason for this seems to be the specific structure of the iron crystals in the core. As shown in the diagram above, they appear to be hexagonal, with the hexagons aligned along the Earth's axis of rotation. However, this is unusual. There is no reason why they should adopt this arrangement. However, after Frost and his team run highly detailed computer simulations showing how the inner core of the earth is growing, they believe they have the answer.
"The simplest model seemed a bit unusual - that the inner core is asymmetrical," Frost said in a press release from UC Berkeley. "The west side looks different from the east side up to the middle, not just at the tip of the inner core, as some have suggested. We can only explain that if one side is growing faster than the other."
Slate Core PressRelase UCBerkeley MarineLasbleis
The new model by Frost and his team suggests that the inner core of the earth grows faster on its east side (left). Gravity keeps the core spherical by pushing newly formed iron crystals in the direction of the north and south poles (arrows), thereby aligning the longitudinal axis of the crystals along the axis of rotation of the planet (dashed line). Photo credit: Marine Lasbleis
This does not mean that the solid core is physically crooked. The strong pull keeps the core spherical by redistributing the newly frozen iron crystals in the relatively "soft" outer part of the inner core. This shows that the core seems to be cooling faster on the one hand under Indonesia than on the other hand under Brazil.
At the moment there is no telling why this is happening. It has apparently been going on since the inner core was formed about 1-1.5 billion years ago. Does it have something to do with the "South Atlantic Anomaly" - a weak point in the Earth's magnetic field under Brazil and the South Atlantic?
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This must be a riddle to be solved in the future.

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