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lithosphere vs. asthenosphere

lithosphere

[lith-uh-sfeer] / ˈlɪθ əˌsfɪər /

noun

Geology.

the solid portion of the earth (atmosphere,hydrosphere ).
the crust and upper mantle of the earth.

asthenosphere

[as-then-uh-sfeer] / æsˈθɛn əˌsfɪər /

noun

Geology.

the region below the lithosphere, variously estimated as being from fifty to several hundred miles (eighty-five to several hundred kilometers) thick, in which the rock is less rigid than that above and below but rigid enough to transmit transverse seismic waves.