The lower layer of the crust

Douglas Harper's Etymology Dictionary Word definitions in Douglas Harper's Etymology Dictionary
layer of the Earth's upper mantle, 1914, from Greek asthenos (see asthenia ) + sphere .\n

Wikipedia Word definitions in Wikipedia
The asthenosphere (from Greek ἀσθενής asthenḗs 'weak' + "sphere") is the highly viscous, mechanically weak and ductilely deforming region of the upper mantle of the Earth . It lies below the lithosphere , at depths between approximately below the surface. ...

WordNet Word definitions in WordNet
n. the lower layer of the crust

Wiktionary Word definitions in Wiktionary
n. (context geology English) The zone of the Earth's upper mantle, below the lithosphere.

The Collaborative International Dictionary Word definitions in The Collaborative International Dictionary
asthenosphere \asthenosphere\ n. 1. the lower layer of the earth's crust, below the lithosphere. It is estimated as from fifty to several hundred miles thick. It is less rigid than the lithosphere, but still rigid enough to transmit some transverse ...