asthenolithGeol.|æsˈθɛnəʊlɪθ| [f. as next + -lith.] The material in the asthenosphere. 1929B. Willis in Bull.Geol.Soc.Amer. XL. 311 An asthenolith may be defined as a body of magma formed in consequence of a rise of temperature in the asthenosphere because of concentration of heat energy.