S U M M A R Y A 3-D finite-element simulation of global electromagnetic induction is used to evaluate satellite responses in geomagnetic dipole coordinates for harmonic ring-current excitation of a threelayer mantle overlain by a realistic near-surface conductance distribution. Induced currents are modelled for lithospheric and asthenospheric upper-mantle conductivities in the range σ = 10−4–0....

The discovery of a phase transition in Mg-rich perovskite (Pv) to a post-perovskite (pPv) phase at lower mantle depths and its relationship to D′′, lower mantle heterogeneity and iron content prompted an investigation of the relative importance of lower mantle compositional and temperature fluctuations in creating topographic undulations on mixed phase regions. Above the transition, Mgrich Pv m...

Computer models of mantle convection constrained by the history of Cenozoic and Mesozoic plate motions explain some deep-mantle structural heterogeneity imaged by seismic tomography, especially those related to subduction. They also reveal a 150-million-year time scale for generating thermal heterogeneity in the mantle, comparable to the record of plate motion reconstructions, so that the probl...

Bends in volcanic hotspot lineaments, best represented by the large elbow in the Hawaiian-Emperor chain, were thought to directly record changes in plate motion. Several lines of geophysical inquiry now suggest that a change in the locus of upwelling in the mantle induced by mantle dynamics causes bends in hotspot tracks. Inverse modeling suggests that although deep flow near the core-mantle bo...

The passive elastic properties of the mantle of the cuttlefish Sepia officinalis have been characterized in experiments on intact mantle and on pieces cut from the mantle. The mantle was found to be very compliant over a wide range of circumferential strains, corresponding to a change in mantle circumferential strain of 0.45. Beyond this range of strain, the mantle was much stiffer, in both the...

Using seismic data from regional earthquakes in Tibet recorded by the Hi-CLIMB experiment, Pn attributes are used to constrain the velocity gradient and attenuation structure of the Tibetan lithosphere under the Hi-CLIMB array. Numerical modeling is performed using the spectral-element method (SEM) for laterally varying upper-mantle velocity and attenuation, and the seismic attributes considere...

Plate subduction continuously transports crustal materials with high-δ(18)O values down to the mantle wedge, where mantle peridotites are expected to achieve the high-δ(18)O features. Elevated δ(18)O values relative to the upper mantle value have been reported for magmas from some subduction zones. However, peridotites with δ(18)O values significantly higher than the well-defined upper mantle v...

[1] Measurements of source‐side splitting in S waves from events within the Tonga slab reveal anisotropy in the upper and mid‐mantle beneath the slab. We observed splitting for events originating at both upper mantle and transition zone depths. Anisotropic fast directions ( ) are trench parallel or sub‐parallel for both upper mantle and transition zone events. Delay times (dt) decrease with dep...

It is well accepted that subduction of the cold lithosphere is a crucial component of the Earth's plate tectonic style of mantle convection. But whether and how subducting plates penetrate into the lower mantle is the subject of continuing debate, which has substantial implications for the chemical and thermal evolution of the mantle. Here we identify lower-mantle slab penetration events by com...