lithosphere

The upper shell of the solid Earth, comprising the crust and upper mantle, which deforms in a brittle fashion when subjected to a stress of greater than 100 MPa.

It has a variable depth of around 2 - 3 kilometres at the ocean floor, increasing in thickness to around 180 kilometres underneath old continental crust. Beneath cratonic areas, it is at least 250 kilometres thick, possibly as much as 500 kilometres.

Lith"o*sphere (?), n. [Litho- + sphere.] (Phys. Geog.)

(a)

The solid earth as distinguished from its fluid envelopes, the hydrosphere and atmosphere.

(b)

The outer part of the solid earth, the portion undergoing change through the gradual transfer of material by volcanic eruption, the circulation of underground water, and the process of erosion and deposition. It is, therefore, regarded as a third mobile envelope comparable with the hydrosphere and atmosphere.

 

© Webster 1913