Between a rock and a hot place: the core–mantle boundary

Abstract

The boundary between the rocky mantle and iron core, almost 2900 km below the surface, is physically the most significant in the Earth's interior. It may be the terminus for subducted surface material, the source of mantle plumes and a control on the Earth's magnetic field. Its properties also have profound significance for the thermochemical and dynamic evolution of the solid Earth. Evidence from seismology shows that D″ (the lowermost few hundred kilometres of the mantle) has a variety of anomalous features. Understanding the origin of these observations requires an understanding of the elastic and deformation properties of the deep Earth minerals. Core–mantle boundary pressures and temperatures are achievable in the laboratory using diamond anvil cell (DAC) apparatus. Such experiments have led to the recent discovery of a new phase, ‘post-perovskite’, which may explain many hitherto poorly understood properties of D″. Experimental work is also done using analogue minerals at lower pressures and temperatures; these circumvent some of the limits imposed by the small sample size allowed by the DAC. A considerable contribution also comes from theoretical methods that provide a wealth of otherwise unavailable information, as well as verification and refinement of experimental results. The future of the study of the lowermost mantle will involve the linking of the ever-improving seismic observations with predictions of material properties from theoretical and experimental mineral physics in a quantitative fashion, including simulations of the dynamics of the deep Earth. This has the potential to dispel much of the mystery that still surrounds this remote but important region.

Modeling defects and plasticity in MgSiO3 post-perovskite: Part 2—screw and edge [100] dislocations

“…The lowermost 200–300 km of the Earth’s mantle located above the core–mantle boundary (CMB), also known as D″ layer, is a very complex region (Wookey and Dobson 2008 ) characterized by strong lateral heterogeneity, pronounced seismic anisotropy and several regions of much reduced seismic velocities (ultra-low-velocity zones, ULVZs). Being at the interface between the core (made of a liquid iron alloy) and the silicate minerals of the mantle, the CMB represents one of the most important boundary layers of the Earth (with for instance a density contrast which exceeds the one between the crust and the atmosphere).…”

Oscillation tomografy study of Earth’s composition and density with atmospheric neutrinos

“…10c, but including the uncertainties in the outer-core densities Fig. 13 The ratio Z/A as a function of the weight fraction of hydrogen position and/or density of the Earth. This worsens at 2 and 3σ and for the inverted ordering (Fig.…”

“…The various processes that occur in this interface are highly influenced by heterogeneous structures at or near it. The great disparity in density prevents direct convection movement through the CMB, and nearby regions control the transfer of heat and material [13]. These processes strongly affect the convection in the mantle, responsible for the plate motion and continental drift, and the more vigorous convective flow in the outer core that is believed to be at the origin of the Earth's magnetic field (i.e., the functioning of the geodynamo) [14,15].…”

Introduction. Progress in Earth science and climate studies

“…Moreover, the dynamics of energetic eddies and topographically steered jets may both temper and enhance the sensitivity of different aspects of the ACC's circulation to the changes in climate. In the last of the opening papers, Wookey & Dobson (2008) explore the boundary between the Earth's rocky mantle and iron core. Lying almost 2900 km below the surface, this is physically the most significant region in the Earth's interior.…”