The interior of the Earth could contain ten thousand billion tons of diamonds
Its depth, between 145 and 240 kilometers,
makes unreachable.
It is the most coveted mineral, and also the most resistant on Earth, a symbol of luxury and the power of the most affluent classes.
We know that diamonds are hidden under the surface of the Earth, and also that they exist outside our planet (as in Neptune, where small fragments of diamond rain). What we did not know is that the interior of the Earth would be full of such amount: ten thousand billions of tons of diamonds, that is, 10 raised to 16 tons.
Does this mean that this beloved mineral might not be as special as it was thought, and lose, therefore, its value?
No, since these diamonds are unattainable: they are 145 to 240 kilometers below the surface of the Earth, in the "roots" of the cratons, which are large sections of rock.
Cratons are found beneath most continental tectonic plates and have barely moved since ancient times, as described in an MIT statement.
Those responsible for this discovery belong to several universities around the world, and they noticed the ostentatious hiding place when observing the seismic waves under the Earth.
Because these vibrations can change, depending on the composition, temperature and density of the rocks, researchers can use these recordings to build an image of the interior of the Earth.
This is how they discovered that underground vibrations, produced by natural processes such as earthquakes and tsunamis, tended to accelerate when they passed through cratonic roots; the acceleration was greater than expected due to the fact that the cratons tend to be colder and less dense than the surrounding structures. This was an indicator of a presence that the researchers ignored.
The team created a three-dimensional model of the velocities of seismic waves that traveled through the planet's main skulls. Then, they created "virtual rocks" from various combinations of different minerals and calculated how fast the seismic waves would travel through these rock compositions.
Finally, they came to the conclusion that the best explanation for the speeds observed underground, which differed from those predicted, was that 1 to 2% of the roots of the cratons were made up of diamonds, while the rest was composed of peridotite (the main type of rock in the upper mantle of the Earth) and some rocks of the oceanic crust.
"When waves pass through the Earth, diamonds transmit them faster than other rocks or minerals that are less rigid," explains Joshua Garber, a postdoctoral fellow at UC Santa Barbara and lead author of the study.
Alternative hypotheses
The explanation of diamonds is one of the possible explanations for this mystery, but it is not the only one. Therefore, scientists are not certain that this assumption is true.
Other researchers have suggested alternative, but more unlikely explanations: perhaps, these cratonic rocks are colder than the scientific literature suggests, which means that the rock will be more rigid and, therefore, seismic waves will travel faster through of them, even if they are not diamond.
