The Pratt hypothesis posits lateral variations in the density of this rheologically-defined region, while the Airy hypothesis posits lateral variations in its thickness.
The Pratt hypothesis posits lateral variations in the density of this rheologically-defined region, while the Airy hypothesis posits lateral variations in its thickness. Both hypotheses seek to explain its isostatic equilibrium with the layer below it, which is sometimes known as the low seismic velocity zone. The layer below it may contain partial melt or volatile enrichment, explaining the lower layer's plasticity compared with this layer's rigidity. FTP name this solid thermal boundary layer of the Earth broken up into plates that float on the asthenosphere, consisting of the crust and upper mantle.
The Pratt hypothesis posits lateral variations in the density of this rheologically-defined region, while the Airy hypothesis posits lateral variations in its thickness.
{lithosphere} (accept {crust} before “rheologically-defined”)