a thin semifluid layer of the earth (100–200 km thick), below the outer rigid lithosphere, forming part of the mantle and thought to be able to flow vertically and horizontally, enabling sections of lithosphere to subside, rise, and undergo lateral movement
See also isostasy
Word origin
C20: from astheno-, from Greek asthenēs weak + sphere
asthenosphere in American English
(æsˈθɛnəˌsfɪr)
noun
a zone in the upper mantle of the earth, consisting of hot, plastic rock, that underlies the solid lithosphere
Word origin
< Gr asthenēs, weak (see asthenia) + -o- + -sphere