There is a mysterious brewery in the center of Earth..
Scientists can only see it when studying seismic waves (underground tremors generated by earthquakes) that pass through the planet’s solid iron. Earth’s inner coreFor some reason, the waves pass through the core much faster when traveling between the North and South Pole than when traveling across the equator.
Researchers have known this discrepancy, known as seismic anisotropy, for decades, but have not been able to come up with an explanation that matches the available data.Now, using computer simulations of core growth over the last billion years, a new study in the June 3 issue Nature Geoscience We provide a solution that seems to fit in the end.Every year, the Earth’s inner core grows in a “biased” pattern and is new iron Crystals form faster on the east side of the core than on the west side.
Daniel Frost, a seismologist and principal investigator at the University of California, Berkeley, told Live Science: “That means that the outer core is taking more heat from the eastern side. [under Indonesia] From the west [under Brazil]”
To visualize this biased growth of the core, imagine a tree trunk with growth rings radiating from the center point. However, the ring is further away because “the center of the ring is offset from the center of the tree”. It is on the east side of the tree and is approaching the west side.
The cross section of the Earth’s inner core may resemble it. However, this asymmetrical growth does not mean that the inner core itself is at risk of malformation or imbalance, the researchers said.
On average, the radius of the inner core grows evenly by about 0.04 inches (1 millimeter) each year. gravity Correct the eastern biased growth by pushing new crystals to the west. There, the crystals aggregate into a lattice structure that extends along the north-south axis of the core. According to the team’s model, these crystal structures are parallel to the Earth’s poles and are seismic ultra-highways that allow seismic waves to travel quickly in that direction.
Anyway, what is the cause of this inner core imbalance? According to Frost, it’s hard to say that without looking at all the other layers of our planet.
“Every layer of the earth is controlled by what is above it and affects what is below it,” he said. “The inner core freezes slowly from the liquid outer core, much like a snowman adds layers. Then the outer core is cooled by the mantle above it, so why the inner core grows faster than one side. The other may be asking why one side of the mantle is cooler than the other. “
Tectonic plates may be partly responsible, Frost said.When cold tectonic plates dive deep into the surface Subduction zone (Where one plate sinks under another), they cool the mantle below. But whether cooling the mantle can affect the inner core remains a matter of debate, Frost said.
Equally puzzling is whether the unbalanced cooling of the core may be affecting the planet. magnetic fieldThe modern magnetic field is driven by the movement of the molten iron in the outer core. The movement of this liquid is driven in sequence by the heat lost from the inner core. If the inner core loses more heat in the east than in the west, the outer core will also move more in the east, Frost said.
“The question is, does this change the strength of the magnetic field?” He added.
While such a big question goes beyond the team’s new paper, Frost said he has begun working on a new study with a team of geomagnetic scientists to explore some possibilities.
Originally published in Live Science.
The Earth’s core continues to grow “biased” and scientists don’t know why
https://www.livescience.com/earth-inner-core-lopsided-crystal-growth.html The Earth’s core continues to grow “biased” and scientists don’t know why