Lithospheric mantle

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The lithospheric mantle comprises the outermost part of the upper mantle . It lies above the partially melted asthenosphere and below the earth's crust . Together with the earth's crust, it forms the lithospheric plates, which span the earth's surface and move against each other on the asthenosphere according to various physical laws ( plate tectonics ).

The lithospheric mantle reaches different depths, which under oceanic areas is influenced in particular by the cooling of the newly formed oceanic crust and therefore depends primarily on its age. The transition from the lithosphere to the asthenosphere, the Gutenberg discontinuity , is typically at depths between 60 and 100 km, but becomes increasingly shallower towards the mid-ocean ridges , as more and more material of the liquid asthenosphere grows with the cooling plate. Under the continents, the lithospheric mantle extends on average to a depth of 120 km, under the archaic shields sometimes up to 160 km.

The lithospheric mantle is by no means a continuous mantle around the earth, but is broken through by mid-ocean ridges, subduction zones and hot spots ; in these areas the lighter asthenosphere penetrates close to the earth's surface. The lithospheric mantle is pushed below the asthenosphere at subduction zones and can thus reach areas of the mantle transition zone (about 660 km deep). On the basis of seismological investigations, it is assumed that lithospheric fragments can in some places even be pulled down to the core-mantle boundary .