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The Core-Mantle Boundary Region

The Core-Mantle Boundary Region

Michael Gurnis (Editor), Michael E. Wysession (Editor), Elise Knittle (Editor), Bruce A. Buffett (Editor)

ISBN: 978-1-118-66974-7

Mar 2013, American Geophysical Union

334 pages

Select type: O-Book

Description

Published by the American Geophysical Union as part of the Geodynamics Series, Volume 28.

The core-mantle boundary (CMB) is the largest density interface within the Earth's interior, and the change in material properties is as significant as that between the solid Earth and the hydrosphere. The two giant heat engines responsible for plate tectonics and the geodynamo dynamically interact at this boundary. The CMB is as dynamic as the Earth's outer skin, and seismological observations show that dense mantle dregs, anti-continents, raft around the mantle's base and are underlain by giant molten oceans. The mantle dregs are sheared and have developed strong seismic anisotropy. The CMB dynamically interacts with the planet's surface; old oceanic lithosphere has been imaged down to the mantle's base where it accumulates. Reversal pathways of the geomagnetic field may be controlled by molten oceans at the CMB. The molten oceans the seismological ultra low velocity zone—may be the source of hot-spot volcanism at the Earth's surface. The complex magnetohydrodynamics of the geodynamo within the fluid outer core of the Earth has been simulated on a computer, and the models show a surprising similarity to the observed geomagnetic field, including the observed westward drift and episodes of flux expulsion.

Preface
Michael Gurnis, Michael E. Wysession, Elise Knittle, and Bruce A. Buffett vii

Introduction
Michael Gurnis, Michael E. Wysession, Elise Knittle, and Bruce A. Buffett   1

STRUCTURE OF THE LOWERMOST MANTLE AND D"

Deep subduction and aspherical variations in P-wavespeed at the base of Earth's mantle
Rob D. van der Hilst, Sri Widiyantoro, Kenneth C . Creager, and Thomas J . McSweeney   5

Global analysis of shear w ave velocity anomalies in the lower-most m \antle
Xian-Feng Liu and Adam M. Dziewonski 21

PKP and PKKP precursor observations: Implications for the small-scale structure
of the deep mantle and core
Peter M. Shearer, Michael A. H. Hedlin, and Paul S. Earle 37

Illuminating the base of the mantle w ith diffracted waves
Raul W. Valenzueia and Michael E. Wysession 57

PHYSICAL AND CHEMICAL PROPERTIES OF THE CORE MANTLE REGION

The temperature contrast across D "
Quentin Williams 73

Elastic constants an danisotropy of MgSiO3 perovskite, periclase, and SiO2 at high pressure
Lars Stixrude 83

Investigating causes of D" anisotropy
J.-M. Kendall and P. G. Silver 97

The solid/liquid partitioning of major and radiogenic elements at lower mantle pressures:
Implications for the core-mantle boundary region
Elise Knittle 119

Is there a thin electrically conducting layer at the base of the mantle?
J. P. Poirier, V. Malavergne, and J. L. Le Mouel 131

CORE MANTLE COUPLING AND THE GEOMAGNETIC FIELD

Electromagnetic core-mantle coupling: II Probing deep mantle conductance
Richard Holme   139

Free oscillations in the length of day: Inferences on physical properties near the core-mantle
boundary
Bruce A. Buffett 153

Interpreting the paleomagnetic field
David Gubbins 167

A one-dimensional map of Bs from torsional oscillations of the Earth's core
Stephen Zatman and Jeremy Bloxham 183

DYNAMICS OF THE CORE AND LOWER MANTLE

Numerical dynamo modeling: Comparison with the Earth's magnetic field
Weijia Kuang and Jeremy Bloxham 197

Geodynamically consistent seismic velocity predictions at the base of the mantle
I. Sidorin and Michael Gurnis 209

Three-dimensional simulations of mantle convection w ith a thermo-chemical basal boundary
layer:D "?
Paul D. Tackley 231

INTERPRETATIONS OF LOWER MANTLE STRUCTURE, CHEMISTRY, AND DYNAMICS

The EDGES of the mantle
Don L. Anderson 255

The D" discontinuity and its implications
Michael E. Wysession, Thorne Lay, Justin Revenaugh, Quentin Williams, Edward D. Garnero,
Raymond deanloz, and Louise H. Kellogg 273

Seismic w ave anisotropy in the D" region and its implications
Thorne Lay, Quentin Williams, Edward D. Garnero, Louise Kellogg, andM ichael E. Wysession 299

Ultralow velocity zone at the core-mantle boundary
Edward J. Garnero, Justin Revenaugh, Quentin Williams, Thorne Lay, and Louise H. Kellogg   319