Knowledge of Earth’s past mantle structure is inherently unknown. This lack of knowledge presents problems in many areas of Earth science, including in mantle circulation modelling (MCM). As a mathematical model of mantle convection, MCM’s require boundary and initial conditions. While boundary conditions are readily available from sources such as plate reconstructions for the upper surface, an...

[1] Plate tectonics constitutes our primary framework for understanding how the Earth works over geological timescales. High-resolution mapping of relative plate motions based on marine geophysical data has followed the discovery of geomagnetic reversals, mid-ocean ridges, transform faults, and seafloor spreading, cementing the plate tectonic paradigm. However, so-called ‘‘absolute plate motion...

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...

[1] We present maps of ionospheric precipitation regions, based on 11 years of DMSP particle data, binned by the interplanetary magnetic field (IMF), with superposed SuperDARN convection streamlines gathered under similar conditions. The convection patterns are transformed into an inertial coordinate system. The maps, which include both the nightside and dayside, are created in a fully automate...

The D″ region consists of many different structures on length-scales and here we test whether an inhomogeneous scattering could potentially explain two these seismic observables, namely PKP precursors, which are generated by near the core-mantle boundary, reflections a discontinuity in lowermost mantle. focus this study is modeling precursors lower mantle reflections. Testing heterogeneity mode...

Numerical calculations of fully three-dimensional convection in constant viscosity, compressible spherical shells •re interpreted in terms of possible convective motions in the mantles of Venus mad Mars. The shells are heated both internally and from below to account for radiogenic heating, secular cooling, and heat flow from the core. The lower boundary of each of the shells is isothermal and ...

Layered viscosity, temperature-dependent viscosity, and surface plates have an important effect on the scale and morphology of structure in spherical models of mantle convection. We find that long-wavelength structures can be produced either by a layered viscosity with a weak upper mantle or temperature-dependent viscosity even in the absence of surface plates, corroborating earlier studies. Ho...

[1] We constrain the anisotropy associated with a very low velocity province (VLVP) at the base of the Earth’s mantle using the SKS and SKKS waves sampling the region. Our selected high-quality data sets consist of 415 SKS and 111 SKKS waveforms for 127 deep earthquakes recorded at distances between 90 and 150 by the seismic stations in three temporary broadband PASSCAL seismic arrays: the Kaap...

Roughly 30 years have passed since the last publication of a linear resolution calculation of density inside the Earth. Since that time, the data set of free oscillation degnerate frequencies has been completely re-estimated taking into account the biassing effects of splitting and coupling due to 3D structure. This paper presents a new resolution analysis based on the new data and focuses on t...

[1] The shear velocity structure in the lowermost 500 km of the mantle beneath the Caribbean and surrounding areas is determined by seismic tomography applied to a suite of Sd-SKS, ScS-S, (Scd + Sbc)-S, and ScS-(Scd + Sbc) differential times, where (Scd + Sbc) is a pair of overlapping triplication arrivals produced by shear wave interaction with an abrupt velocity increase at the top of the D00...