Madrid. The inner core of the Earth is the most inaccessible place on our planet, under extreme conditions: its temperature can exceed the temperature of the surface of the Sun. It is a solid ball of iron and nickel that rotates, like the rest of the Earth. ground layers. Did this stop dead? The answer is no.
In any case, its speed has decreased and is “out of balance” with the rotational speed of the rest of the planet – minimally.
So says at least a recent article in Nature Geoscience led by Xiaodong Song and Yi Yang of Peking University. Although scientists talk about a “recent stop” in this study and that the core’s rotation could be “reverse,” this does not mean that it stopped suddenly or that it rotates in the opposite direction to Earth’s surface.
There are nuances, one of which concerns relativistic velocities (with respect to another body) and direction reversal, explains Maurizio Mattesini, professor of geophysics at the Complutense University of Madrid and researcher at the Institute of Geophysics. , to EFE. Earth Sciences (IGEO), from the Higher Center for Scientific Research (CSIC), whose “examination of the inner core is important for understanding the dynamics and state of health of the planet.”
What is the inner core?
The Earth is made up of different layers and in the middle, at a depth of 5,000 kilometers, is a ball made almost entirely of iron. It is the inner core, with a radius of 1,220 kilometers – slightly larger than Pluto’s – and surrounded by a 2,260-kilometer-thick layer of the same composition, but in a molten state, a kind of “mattress”.
The inner core was discovered in 1936 by the Danish seismologist Inge Lehmann when analyzing seismic waves.
Convective motions in the liquid outer core, along with Earth’s rotation, generate the magnetic field, which shields Earth from high-energy particles arriving from the sun and from space.Alberto Molina, Marina Puente and Pablo Rivera, also from IGEO, explain in an exhibition.
Around the core is the mantle, which is about 2,900 km thick, and above it is the Earth’s crust.
How do you study the inner core?
It is difficult to analyze the deepest layer of the earth. With drilling to collect samples, it is impossible, says Mattesini, who recalls that the deepest hole made so far is less than 12 kilometres.
CT still suffers from technological limitations, so an alternative is seismology.
Earthquakes generate seismic waves that propagate through the interior of the planet, and some pass through the inner core, where they appear on the Earth’s surface. This is when seismographs register a signal containing information from the center of the Earth.
The planet rotates and it takes about 24 hours to complete one revolution. Until now it was thought that the inner core had continued the same dynamics recorded over the past decade, that is, it was spinning slightly faster than the mantle and crust, a so-called “superrotation”, so that it was moving forward about a tenth of a row each year.
The first investigation talking about super-rotation was from 1996 – Song was also involved -, although later studies said otherwise (there is even a minority asserting that there are no differences in rotation). There is enough data, but the differences are so subtle that they lend themselves to scientific interpretation and discussion.
What does the most recent study of Earth sciences in Nature find? The core, since 2009, may be slowing down to the same rotational speed as the outer layers or even slightly less.
These differences in relative velocities are very small, as the IGEO scientists explain in their forums.
For example, a car at 120 kilometers per hour is ahead of another at 121. “Through the window, we will see that it is slowly overtaking us. If the other car brakes and speeds up to 120 kilometers per hour, we will see it “inanimate” next to our car, Even though she keeps moving, just like us.”
In the same way, the core would have slowed down, and now, rotating at the same speed as the mantle and crust, from the Earth’s surface we would see it stop.
Thanks to the geological record, IGEO explains on Twitter, it is known that years in the geological past lasted more days, that is, the Earth rotated faster and therefore the days were shorter (in the Mesozoic they lasted 23 hours).
This is because the Moon is moving away from us at a rate of 3.82 cm per year and its effect is to slow down its rotation, which is imperceptible on a human level.
The new study discovered that the speed at which the moon was slowing experienced outliers. Through the propagation of seismic waves from earthquakes, it has been observed that it could be due to the differential rotation of the core.
It’s not the first time
This slight shift in the nucleus’s spin isn’t the first time it’s happened; The data shows another similar event in 1970.
This indicates that This phenomenon is repeated periodically from about 2-3 decades to 7 decades (depends on authors) This same frequency appears to appear in other geophysical observations, such as the geomagnetic field, the duration of the day—one thousandth of a second longer or shorter depending on the rotation—or the weather, suggesting that they may be related.
But It’s just a hypothesisMattesini warns; There is no scientific evidence yet.
Obviously, the actual time it takes the Earth to complete one revolution varies slightly – important for adjusting navigation systems – and the days are now getting longer again. To discover what lies behind this and the complex terrestrial dynamics, further investigation is necessary.
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