New surprises from the depths of the Earth. For decades we studied at the school that the planet consists of four large concentric envelopes: a crustthe most superficial, followed by mantothen one outer core and finally an inner core. according to a study recent published on Nature Communicationswhat analyzed about 200 earthquakes that occurred in the last ten years, there is a fifth level in the interior of the planet, an inner core of almost pure iron.
This nucleus, with a radius of only 650 kmslightly greater than the distance between Rome and Milan, it’s called in english Inner Core (IC) and would represent less than 1% of the Earth’s volume.
The Earth’s core, more complex than previously thought
The study, carried out by Thanh-Son Pham and Hrvoje Tkalčić, both at the Australian National University in Canberra, sheds some light on an area of our planet that is still shrouded in many shadowsmainly due to the inaccessibility and impossibility of direct observations.
just say that the greatest depth reached by humans through wells dug underground It’s in Kola Well, Russiaand does not reach 13 km.
The depths of the Earth are impossible to directly explore
It was a huge challenge for humanity to go this far, but it is not almost nothing compared to the depth at which the center of the planet is located, just under 6400 km below our feet! After all, it would be impossible and unimaginable to reach these depths, due to the extremely high temperatures (thousands of degrees centigrade in the core) and at a pressure millions of times higher to which we are subject on the surface.
Help comes from earthquakes
There is no technology that can penetrate to these depths and that allows us to determine the structure or composition. The only way to know the interior of the Earth, until now, is through the study of the behavior of seismic waveswhich we can use as a scanner of the depths of the planet.
In fact, the strongest earthquakes produce seismic waves that cross the planet, propagating in all directions with different speeds, depending on the density of the medium traversedwhich allows us to obtain valuable information about what we cannot see, just as X-rays applied to the human body are valuable in the field of medicine for making medical diagnoses.
Some of these waves reach the surface, and unfortunately they are sometimes responsible for serious damage – the last example comes from Turkey and Syria – while others propagate to the depths of the Earth, becoming faster or slower depending on the terrestrial envelope through which they passand are thus conditioned by the physical characteristics of the medium in which they propagate (mainly density).
The behavior of seismic waves varies depending on the physical characteristics of the medium through which they pass: this led to the discovery that the Earth is composed of several concentric layers with very different density characteristics.
It was the Danish seismologist and geophysicist Inge Lehmann who first realized this and laid the foundations for understanding the interior of the planet. The different speeds of seismic waves as they propagate, along with other factors, have made it possible since the last century to understand many things about what the Earth’s interior is like.
It was therefore the great earthquakes of the past that made us realize that there are different layers in depthwith physical and chemical characteristics very different from those found on the surface, separated from each other by discontinuities.
The Earth’s structure is complex, but it can be simplified into a succession of concentric envelopes with homogeneous characteristics, separated by discontinuities.. A crust is separated from the mantle by the so-called discontinuity of Mohorovicic (on average 30 km below). O manto extends thousands of kilometers deep to the discontinuity of Gutenberg (located 2890 km below our feet). There begins the Outer corewhich extends to 5150 km, where the discontinuity of Lehmann marks the beginning of inner core.
A new layer: an almost pure iron core
The study by the Australian researchers revived an idea that had already been proposed some twenty years ago, namely that the inner core of the planet, the one we find after the outer core, is actually made up of two layers. It would be composed of a not very homogeneous outer layer and a very compact inner layer, consisting of practically pure iron and with a radius of only 650 kilometers.
The study opens up very interesting scenarios, as the presence of this additional core would allow us to better understand how our planet was formed.and would also allow us to hypothesize when the Earth will cease to be habitable due to the solidification of the outer core, fundamental in generating the magnetic field, a formidable umbrella that protects us from space radiation.
Not all seismologists agree that these observations prove the existence of an inner core distinct from the others., as related to Scientific Americanwhile everyone agrees that, thanks to the best technologies we have today to detect even weaker seismic signals, new scenarios open up to learn about the depths of the planet.
The publication of this new work comes less than a month after the diffusion of one scientific study carried out by a team of Chinese researchers has revealed a slowdown in the rotation of the inner core of the planet and a possible change of direction from the surface.
