the inner core is not fixed!

that the core of the earth occurs from a depth of 2,900 km. Represents approximately 17% of bind of the earthit is located in its central part and is distinguished into two parts: an outer core liquid and an inner core (or seeds) solid.

The outer core consists essentially of about 80 to 85% of iron very hot in fusion. It is stirred by a movement of convection of thermal origin (due to the Earth’s cooling), and it is thanks to this that the Earth’s magnetic field is generated. that inner coreit comes from the gradual crystallization of the outer core and resembles a very hot and dense sphere the size of Plutoalso composed of iron but solid. On the other hand, its exact nature and it movements within it has been the subject of discussion for decades and makes the research fields of geophysics and geochemistry very active.

Techniques for observing and studying the nucleus

One of the problems with studying the Earth’s inner core is that it is not visible, forcing scientists to cheat and use indirect methods to obtain information about its nature and dynamics. With this in mind, researchers Wei Wang and John Vidale – USC Dornsife researchers – used data from Seismic array with large aperture (Lasa), a connected seismometer system from the United States Air Force in Montana, which allows recording and increase the sensitivity of detection of earthquake and explosions.

This type of data is obtained using special signal processing techniques digital such as beamforming, which suppresses noise and thus improves the signal-to-noise ratio.

Using a new beamforming technique developed by Vidale, the two scientists analyzed waves generated by Soviet underground atomic bomb tests at Milrow in 1969 and Cannikin in 1971 under Amchitka Island. They used the same method in the period between 1971 and 1974 in the Arctic archipelago Novaya Zemlya.

How does the Earth’s core behave?

In their latest study, recently published in The progress of science, Wang and Vidale found with these seismic data that the motion of the inner core had changed direction over the six-year period from 1969 to 1974 and had rotated underrotation by at least one tenth of a degree per year. More precisely, observations indicate that the inner core rotated slightly slower from 1969 to 1971, and then began to move in the other direction from 1971 to 1974.

This observation is quite unexpected and first surprised researchers Wang and Vidale. Having an oscillating inner core was a model that had been thought about and existed, but the scientific community was very divided in the viability of this theory. If we go further, some researchers claim that this pattern also explains the observed sharp six-year fluctuation in day length (plus or minus 0.2 seconds over six years), and observed regularly over the last few decades.

It therefore turns out that inner core is not at all fixed, as we have long thought, but that it moves and swings under our feet. But the era of underground nuclear tests is a saga merely, meaning scientists need to use seismic data from Earth’s activity that are relatively less accurate, despite recent advances in instrumentation.

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