(ORDO NEWS) — American scientists have suggested that the lower layer of the upper mantle is a very fluid rock.
Experts managed to draw such a conclusion when studying a deep earthquake that occurred in 2018 near Fiji.
The structure of the Earth is quite difficult to study. The deepest well made it possible to descend 12 km underground.
However, at such a depth, the temperature is so high that it is impossible to move further, as the drill begins to melt.
Therefore, scientists began to study the propagation of seismic waves in order to draw conclusions about the earth’s crust, mantle and core. Although the mantle makes up most of the Earth, not much is known about it.
For example, it is still difficult for scientists to tell how viscous it is. This is important to understand in order to draw conclusions about the evolution of the entire Earth.
Scientists have suggested that the mantle can be studied by deep earthquakes. Most of the earthquakes that are reported in the news are considered superficial, since their sources are located in the earth’s crust.
But there are earthquakes, the sources of which can be located at a depth of up to 725 km. Such earthquakes are less often studied, since the consequences of them are less destructive.
In their work, the researchers focused on the earthquake that occurred in 2018 in the Pacific Ocean near Fiji.
Although the magnitude of the earthquake was 8.2, it did not have destructive consequences, since its source was at a depth of 563 km.
Scientists analyzed data from GPS sensors and found that even years after the earthquake, the Earth does not stop moving. So, even now, the island of Tonga continues to slowly move at a speed of 1 cm / year.
The scientists compared these movements after deformation to viscous honey, which slowly returns to its original shape after being scooped up with a spoon.
Researchers have recorded such an effect from deep earthquakes for the first time.
By studying how the Earth deformed over time after deep earthquakes, the researchers concluded that the lower layer of the upper mantle is rock that has low viscosity. On the contrary, it is quite fluid.
This layer can spread all over the planet.
The presence of such a fluid layer in the mantle may explain some of the phenomena that scientists have recorded before, but could not substantiate using the models available at that time.
Experts believe that the presence of a fluid layer in the mantle may affect how heat is transferred in the Earth, as well as how materials move between the crust, core and mantle over time.
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