The depth of the viscosity jump may be a more suitable dividing line between the upper and lower mantle than the 660-kilometer-deep region currently used, suggests MIT geophysicist Robert van der Hilst.
From the numerical modelling, the lithosphere of the Central System is weaker because of its lower mantle strength (as a result of the crust thickening) and its higher geotherm (due to the high heat production of granites).
Consistent with predictions of an adaptive evolutionary response in eye numbers driven by the need for visualizing objects in the water column, we found scallops had significantly more eyes on the upper mantle than on the lower mantle.
Previously found only in meteorites, ringwoodite is a form of the mineral peridot, believed to exist in large quantities under high pressures in the so-called transition zone-410-660 kilometres beneath the Earth's surface, between the upper and lower mantle.
The harzburgite and dunite of the lower mantle section have often been referred to as depleted peridotite resulting from large degrees of partial melting from a lherzolite parent and also that they are partly formed by the processes such as magma-mantle interaction.