lower mantle

Some geochemical and mineralogical evidence suggests that the upper and lower mantle are chemically different, which supports the idea that the two sections don't mix thermally or physically.

(https://www.nature.com/articles/nature25972) The paper on the perovskite diamond appeared online Wednesday in the journal Nature, under the title "CaSiO3 perovskite in diamond indicates the recycling of oceanic crust into the lower mantle." Its lead author was Fabrizio Nestola from the University of Padova, Italy.

In one or both cases, the lower mantle might be acting as an impenetrable lid--inhibiting heat from escaping from the core, stifling vigorous convection and thus preventing a dynamo from revving up.

In the transition zone that separates the upper mantle from the lower mantle, P-waves jump to 11 km/s that is in the range of the second cosmic velocity a rocket must have to escape the Earth gravity acceleration.

(1971) Convection plume in the lower mantle. Nature 230, 42-43.

The additional elevation and, in some species, projection of upper mantle eyes could result in the upper eyes being capable of detecting predators sooner and at greater distances than lower mantle eyes, especially in species occupying soft bottoms, where their lower valves may become buried in the substrate.

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. This sample really provides extremely strong confirmation that there are local wet spots deep in the Earth in this area,' said Graham Pearson of the University of Alberta, who led the study.

Washington, March 13 ( ANI ): Researchers have found the first-ever sample of a mineral called ringwoodite, analysis of which showed that it contained water - 1.5 per cent of its weight - a finding confirming scientific theories about vast volumes of water trapped 410 to 660 kilometres between Earth's upper and lower mantle.

In the lower mantle post perovskite phase modification results with release of FeO down to the core.

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.

Moreover, the predictions are less sensitive to the choice for the upper-mantle viscosity than to the adopted viscosity of the so-called lower mantle, which extends from ~670 km depth to the core-mantle boundary.

Drawing on material from a series of conferences on the Earth's mantle and deep interior held in 2004 and 2005, this book summarizes findings on the newly discovered "post-perovskite phase transition" in the lower mantle and its implications for many fields in solid Earth geophysics, such as mineral physics, seismology, geodynamics, and geochemistry.

Xie and Kerrich (1994) inferred that the trace-element signamres, particularly the ratios of HFSE (Zr, Hf, Nb) to the REE can distinguish between olivine (shallow mantle), majorite (>14 GPa; > ~ 400 km; Herzberg 1995) and perovskite (lower mantle) fractionation.

Or is it layered--with separate convection cells occurring in an "upper mantle" (extending from near the surface to a depth of about 660 kilometers, or 410 miles) and in an underlying "lower mantle" (with denser rocks under higher pressure)?