Although everyone studies Geography in elementary and high school, some knowledge ends up going unnoticed, such as the amount of layers that Earth has.
If asked about this, it is possible that most people would answer that the planet we live on has only three layers, namely: crust, mantle and core.
However, this knowledge is not complete, as, in fact, the Earth has all these layers and more.
The Earth’s Layers
Our planet is very well divided when it comes to layers. It actually has six of them, which are known as the lithosphere, asthenosphere, upper mantle, lower mantle, outer core, and inner core. Each of these layers has peculiarities that distinguish them.
Initially, when the first scientists discovered the existence of layers due to the technology available at the time, it was estimated that there were only the three mentioned at the beginning of this text.
However, with technological evolution, it was verified, through seismic shocks detected by precision devices nailed in specific points, that there are divisions between these layers.
This is because the ways in which seismic waves propagate within these layers differed from each other, consequently meaning that they are not all the same.
How are these layers characterized?
Well, if it was estimated that they have differences, then what are these divergent characteristics? Well, in a quick summary, the lithosphere is the ground we walk on, which is composed of rigid and unyielding rocks.
The asthenosphere, in turn, a lesser known layer, is composed of molten rocks, but they are not liquid, having a more plasmatic and less viscous aspect. This layer is responsible for allowing the movement of tectonic plates.
Below the asthenosphere lies the upper mantle, which has physical properties similar to those of the asthenosphere (they are sometimes confused because of this), i.e. plasticity and temperature, but is distinguished by its chemical composition and higher viscosity. .
The lower mantle, on the other hand, is composed of rocks in a liquid state, and this is due to the high depth that greatly increases its temperature, allowing the complete melting of the rocks.
As for the nuclei, it is known that the composition of the outer core consists of iron and nickel, as well as low amounts of oxygen and sulfur.
And the inner core, in turn, is different from all the others and has a temperature higher than the solar surface. Even so, its materials are in a solid state, composed solely of iron and nickel.
Below, see a representation of how all these layers are presented:
Another recent discovery
Despite being forgotten by most of society, the asthenosphere plays an extremely important role in the geology of the planet and is the subject of many studies by scientists.
The most recent discovery regarding this layer was the presence of a deeper zone of it that has a slower moving speed than the rest of its layer.
It is also important to remember that the asthenosphere is characterized by its low viscosity, which allows its movement to occur more quickly, even if it takes thousands of years to complete.
For this reason, scientists seek to understand what leads to this differentiation in relation to the upper mantle, and it was because of this that they found this “slower” zone present in the asthenosphere.
This zone differs from the others due to the fact that its temperature is relatively higher than the rest of the layer, which presents a partial melting of the rocks, something unusual for the depth at which it is found.
As the scientists conclude in the summary of the article:
“These results imply the presence of a globally extensive and partially molten zone embedded in the asthenosphere, but this low asthenospheric viscosity is mainly controlled by gradual variations in pressure and temperature with depth.”
