July 2, 2022
The Earth's core appears to be not completely solid and possibly "mixed"

The Earth’s core appears to be not completely solid and possibly “mixed”

For more than half a century, the scientific community has considered the Earth’s core, which lies about 5100 km below the surface, to be a ball with a solid structure, composed of iron. Now, a new study led by Rhett Butler, a geophysicist at the University of Hawaii, suggests that this may not be the case. The study indicates, in fact, that The inner core It’s a great mix of different textures, which brings together hard, soft and liquid parts in different places.

Despite the importance of the kernel – after all, it is thanks to that Earth has a magnetosphere Protection against particulate matter from the sun – no human or machine has been able to get close to it to study it because of the sheer depth, temperature and pressure of the area. So, to understand what’s going on inside Earth, Butler and Seiji Tsuboi, co-author of the study and a researcher at the Japan Agency for Marine Earth Science and Technology, worked on seismic waves.

These waves are caused by earthquakes, and by measuring them, scientists can use these vibrations to reconstruct the internal properties of the Earth. Butler explained that “Seismology, illuminated by earthquakes in the crust and upper mantle, observed by seismic observatories on the Earth’s surface, provides the only direct means of examining the inner core and its processes.” These waves travel through the layers of the Earth and therefore have differences in the speed of their movement.

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The places where the earthquakes analyzed in the study occurred are indicated in red, and the seismic stations in yellow (Photo: Reproduction/Butler and Tsuboi, 2021)

Differences can indicate that waves are either reflected or refracted depending on the materials, temperatures, and density of the layers they traveled through. So, to infer what’s in the inner core, they used data from seismometers collected in places directly opposite where the earthquakes were detected. then with supercomputer Earth Simulator, they got five matches between locations, covering the inner core area.

Interestingly, the pair realized that the waves that should have passed through a solid metal ball were already being reflected in some areas. Butler realized that the only possible explanation for this discrepancy was that the structure they considered faulty, so they conducted a new analysis of the possibility that the inner core had a completely solid structure.

In the end, they found that the observations worked if they considered that the inner core contained pockets of liquid and semi-solid iron with a fungal texture. “In stark contrast to the homogeneous structures considered in all models of the Earth’s inner core since 1970, our models indicate the presence of hard, soft and liquid contiguous regions in the upper 240 km of the core,” he explained. “This brings new constraints on the formation, thermal history, and evolution of the Earth.”

Seismic energy is reflected in circular patterns that follow the inner core (Photo: Reproduction/Butler, Tsuboi, 2021)

Studies of the inner core and discoveries about its heterogeneous structure may provide important new information about the dynamics of the boundary between Earth’s inner and outer core, with implications for our planet’s magnetic field. “Knowing this state at the frontiers of seismology could allow for better predictive models about the geomagnetic field, which protects life on our planet,” the author said.

The article with the results of the study was published in revista Geophysics and planetary interiors.

Source: Live ScienceAnd University of Hawaii

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