(labeled No. 4)
The lower mantle ( Mesosphere of the Earth ) is the inner layer of the mantle located under the asthenosphere , above the core of the Earth .
Content
General characteristics
From the point of view of tectonics of lithospheric plates, it is a passive and inert layer with respect to tectonic movements. The lower boundary is at a depth of 2900 km and is called the Gutenberg boundary , which is also the boundary of the phase transition of matter.
In the lower mantle there is a layer (layer D), in which the speed of seismic waves is abnormally low and has horizontal and vertical inhomogeneities. It is assumed that it is formed by the upward penetration of Fe and Ni into silicates , which are melted by these flows. This is extremely important, as some researchers believe that parts of the subduction plate accumulate 660 km from the boundary and become exponentially heavier and sink to the core and accumulate in layer D [1] .
Under the lower mantle is the Guttenberg Border - the boundary between the mantle and the outer core, characterized by a jump-like decrease in the velocity of longitudinal waves from 13.6 to 8.1 km / s and the disappearance of transverse waves.
See also '
- The geosphere is the shell of the earth.
- The mesosphere of the atmosphere is the upper layer of the atmosphere.
Notes
- β en: Mesosphere (mantle) # cite_ref-1