[1] The vertical coherence of mantle structure is of importance for a range of dynamic issues including convective mass transport and the geochemical evolution of Earth. Here, we use seismic data to infer the most likely depth ranges of strong, global changes in the horizontal pattern of mantle heterogeneity. We apply our algorithm to a comprehensive set of measurements, including various shear...

[1] We analyze moment tensor solutions from deep subduction zone earthquakes to determine global slab deformation patterns. Inferred strain rates are compared to predicted deformation patterns from fluid models to help constrain the first‐order radial and lateral viscosity structure of the Earth. While all slabs that reach the lower mantle are compressed at their tip, intermediate depth pattern...

[1] Compositionally layered mantle models have often been invoked in order to explain the geochemistry observed at the Earth’s surface, specifically the discrepancy between ocean island basalt and mid-ocean ridge basalt compositions. One disadvantage of layered models is the reduction in cooling efficiency compared to whole-mantle convection as a direct result of the insulating nature of the th...

3870 Ma to 3760 Ma metadiorites and tonalites, and older mafic inclusions contained within these rocks from southern West Greenland, have a range of initial end values from + 4.5 to --4.5. The extremely positive initial values determined for nine of the fourteen early Archean samples demonstra te that they were derived from a LREE depleted mantle reservoir which had an end value of ~ + 4 prior ...

2. Summary The Earth consists of the crust, mantle (Note #1), outer core and inner core (Note #2). The D" (pronounced “Dee double prime”) layer is the name given to the lowermost several hundred km of the mantle, directly below which is the molten outer core, which is composed primarily of iron. The temperature and chemical composition within D" vary rapidly as the distance to the core-mantle b...

Magma genesis, migration, and eruption have played prominent roles in the chemical differentiation of the Earth. Plate tectonics has provided the framework of tectonic environments for different suites of igneous rocks and the dynamic mechanisms for moving masses of rock into melting regions. Petrology is rooted in geophysics. Petrological and geophysical processes are calibrated by the phase e...

IT H KA SN O T The deepest hole humans have ever dug reaches 12 kilometers below the ground of Russia’s Kola Peninsula. Although we now have a spacecraft on its way to Pluto—about six billion kilometers away from the sun—we still cannot send a probe into the deep earth. For practical purposes, then, the center of the planet, which lies 6,380 kilometers below us, is farther away than the edge of...

The mantle comprises nearly three-quarters of Earth’s volume and through convection connects the deep interior with the lithosphere and atmosphere. The composition of the mantle determines volcanic emissions, which are intimately linked to evolution of the primitive atmosphere. Fundamental questions remain on how and when the proto-Earth mantle became oxidized, and whether redox state is homoge...

Regional body wave and surface wave studies indicate that there is a 1ow-Q Upper mantle layer underlying a high-Q lithosphere. Great circle surface wave attentuation is used to refine the Q structure of the upper mantle and to demonstrate hat these features are consistent with the global data. Body wave results are used to constrain the average Q of various regions of the mantle and core and th...

Unusual physical properties at the core-mantle boundary have been inferred from seismic and geodetic observations in recent years. We show how both types of observations can be explained by a layer of silicate sediments, which accumulate at the top of the core as Earth cools. Compaction of the sediments expels most of the liquid iron but leaves behind a small amount of core material, which is e...