Asthenosphere: a layer of the Earth’s mantle located beneath the lithosphere, characterized by a plastic and partially fluid behavior that allows the movement of lithospheric plates. It extends approximately from 100 km to about 300–400 km in depth (it does not encompass the entire upper mantle). It is less rigid than the layers above and below, enabling processes such as convection and subduction. Its chemical composition is similar to that of the upper mantle, predominantly ultramafic, and may include minerals like olivine and pyroxenes under conditions of high pressure and temperature.
