[1] Seismic tomography has revealed two large low shear velocity provinces (LLSVPs) in the lowermost mantle beneath the central Pacific and Africa. The LLSVPs are further shown to be compositionally different from their surroundings. Among several hypotheses put forth in recent years to explain the cause of the LLSVPs, one postulates that they are thermochemical piles caused by accumulation 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...

[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...

New isotopic studies of Nd, the daughter product of the short-lived and now extinct isotope Sm, have revealed that the accessible part of the silicate Earth (e.g., upper mantle and crust) is more radiogenic in Nd/Nd than that of chondritic meteorites. The positive Nd anomaly of the Earth’s mantle implies that the Sm/Nd ratio of the mantle was fractionated early in Earth’s history and that the c...

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 ...

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...

Introduction: Geologically recent volcanism on Mars [1-4] can be well explained with mantle convection and plumes [5-7]. Most of these studies have assumed single layer convection in Martian mantle. However, a layered Martian mantle has been suggested in the model of magma ocean and mantle overturn [8]. The possible effects of such stratification on the early volcanism, magnetic dynamo, and the...

[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...

Long intervals of single geomagnetic polarity (superchrons) reflect geodynamo processes, driven by core-mantle boundary interactions; however, it is not clear what initiates the start and end of superchrons, other than superchrons probably reflect lower heat flow across the core-mantle boundary compared with adjacent intervals. Here geomagnetic polarity timescales, with confidence intervals, ar...