The Earth's mantle

  title={The Earth's mantle},
  author={George Helffrich and Bernard John Wood},
Seismological images of the Earth's mantle reveal three distinct changes in velocity structure, at depths of 410, 660 and 2,700 km. The first two are best explained by mineral phase transformations, whereas the third—the D″ layer—probably reflects a change in chemical composition and thermal structure. Tomographic images of cold slabs in the lower mantle, the displacements of the 410-km and 660-km discontinuities around subduction zones, and the occurrence of small-scale heterogeneities in the… 
4 – The Mantle
Publisher Summary The Earth's mantle plays an important role in the evolution of the crust and provides the thermal and mechanical driving forces for plate tectonics. The mantle is also the
Numerical Study of the Origin and Stability of Chemically Distinct Reservoirs Deep in Earth's Mantle
Seismic tomography is providing mounting evidence for large scale compositional heterogeneity deep in Earth's mantle; also, the diverse geochemical and isotopic signatures observed in oceanic basalts
The Upper Mantle and Transition Zone
The upper mantle is the source of almost all magmas. It contains major transitions in rheological and thermal behaviour that control the character of plate tectonics and the style of mantle dynamics.
Reconciling dynamic and seismic models of Earth's lower mantle: The dominant role of thermal heterogeneity
Two large regions of low shear wave velocity in the deep mantle beneath Africa and the Pacific are generally interpreted as hot but chemically dense `piles'. These `piles' are thought to have
Stirring in 3-d spherical models of convection in the Earth's mantle
On a global scale basalts from mid-ocean ridges are strikingly more homogeneous than basalts from intraplate volcanism. The observed geochemical heterogeneity argues strongly for the existence of
Chapter 4 – The Mantle
This chapter summarizes new and exciting information on the mantle and how it operates. It includes a summary of the seismic structure of the mantle and a discussion of large low S-wave velocity
Seismic Heterogeneities and Their Nature in the Lower Mantle
Over the last 20 years, global seismology has made significant progress in mapping the deep interior of the Earth. Tomographic studies identified variations in lower-mantle chemistry and phase
Chemical and seismological constraints on mantle heterogeneity
  • G. Helffrich
  • Geology, Medicine
    Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences
  • 2002
Old ideas that the mantle is heterogeneous in structure, rather than stratified, are reinterpreted and a simple, end–member model for the heterogeneity structure is proposed.


Constraints from seismic anisotropy on the nature of the lowermost mantle
THE D″ layer lies at the bottom of the Earth's rocky mantle, and separates it from the liquid metal-alloy core. This region, extending from the core–mantle boundary to a few hundred kilometres above
Evidence for partial melt at the core–mantle boundary north of Tonga from the strong scattering of seismic waves
Scattered waves that precede the seismic phase PKP (which traverses the Earth's core) have been used to identify and locate small-scale heterogeneity in the Earth's mantle. A recent study has
Segregation of subducted oceanic crust in the convecting mantle
Subducted oceanic crust, transformed into dense mineral assemblages at high pressure, may gravitationally segregate at the bottom of the convecting mantle, for example, the D″ layer. Here it could be
Mantle shear structure beneath the Americas and surrounding oceans
Maps of lateral variation in shear velocity within the mantle beneath North and South America, their surrounding oceans, and parts of Africa and Eurasia are produced from inversion of travel times of
Compositional stratification in the deep mantle
A boundary between compositionally distinct regions at a depth of about 1600 kilometers may explain the seismological observations pertaining to Earth's lower mantle, produce the isotopic signatures
Global seismic tomography: A snapshot of convection in the Earth: GSA Today
Two new global high-resolution models of the P-wave and S-wave seismic structure of the mantle were derived independently using different inversion techniques and different data sets, but they show
Upper-mantle seismic discontinuities and the thermal structure of subduction zones
The precise depths at which seismic velocities change abruptly in the upper mantle are revealed by the analysis of data from hundreds of seismometers across the western United States. The boundary
Chemical differentiation of the Earth: the relationship between mantle, continental crust, and oceanic crust
The average chemical compositions of the continental crust and the oceanic crust (represented by MORB), normalized to primitive mantle values and plotted as functions of the apparent bulk partition
Mixing in numerical models of mantle convection incorporating plate kinematics
The process by which subducted lithosphere is mixed by mantle convection is investigated in numerical calculations. The results show that the observed isotopic heterogeneity of mantle sources and