Physics of the Earth

Cambridge University Press
9780521873628 - Physics of the Earth - by Frank D Stacey and Paul M Davis
Frontmatter/Prelims
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Physics of the Earth

The fourth edition of Physics of the Earth maintains the original philosophy of this classic textbook on fundamental solid Earth geophysics, while being completely revised and up-dated by Frank Stacey and his new co-author Paul Davis. Building on the success of previous editions, which have served generations of graduate students and researchers for nearly forty years, this new edition will be an invaluable resource for graduate students looking for the necessary physical and mathematical foundations to embark on their own research careers in geophysics.

The book presents a detailed, critical analysis of the whole range of global geophysics topics and traces our understanding of the Earth, from its origin and composition to recent ideas about rotation of the inner core. The division of this new edition into an increased number of shorter chapters is designed to make the material more accessible, and allows students to focus on topics of particular interest. New chapters on elastic and inelastic properties, rock mechanics, kinematics of earthquake processes, earthquake dynamics and thermal properties have been added. A brief concluding chapter also reviews contributions from solid Earth studies to our understanding of climate change and the potential for ‘alternative’ energies.

Appendices, presenting fundamental data and advanced mathematical concepts, and an extensive reference list, are provided as tools to aid readers wishing to pursue topics beyond the level of the book. Over 140 student exercises of varying levels of difficulty are also included, and full solutions are available online at www.cambridge.org/9780521873628.

Frank Stacey is a graduate of London University. After appointments in Canada, Australia and UK, he went to the University of Queensland in 1964 and it was there that the first three editions of ‘Physics of the Earth’ were written. After retirement as Professor of Applied Physics, he joined CSIRO Exploration and Mining (in 1997) to continue geophysical research. He has published on a wide range of geophysical topics and has been recognized by his peers by election to fellowship of the Australian Academy of Science and the American Geophysical Union and by the award of the inaugural Neel medal of the European Geophysical Society, as well as numerous visiting lectureships at institutions around the world. Professor Stacey is also the author/editor of three other books.

Paul Davis is a graduate of the University of Queensland. After appointments in Edmonton, Canada, and Cambridge, he joined the University of California at Los Angeles (UCLA), where he is Professor of Geophysics. He has published extensively on geophysical topics, especially seismology. His professional honours include a Guggenheim fellowship, fellowship of the Royal Astronomical Society and the American Geophysical Union and a visiting Leverhulme professorship to the University of Oxford. He has served a term as editor of the Journal of Geophysical Research (Solid Earth). Professor Davis is also the co-author of another undergraduate textbook.

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Gemini XI photograph of the Gulf of Aden and the Red Sea by NASA astronauts Charles Conrad and Richard F. Gordon. This is one of the areas of particular interest in the theory of sea floor spreading. A line of earthquake epicentres extends from the ridge system in the Indian Ocean, up the middle of the Gulf of Aden and into the Red Sea, marking the axis of a new ridge along which mantle material is rising as the Africa and Arabia plates part. Courtesy of the National Aeronautics and Space Administration, Washington.

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Physics of the Earth

Fourth edition

Frank D Stacey
CSIRO Exploration and Mining, Brisbane, Australia

Paul M Davis
Department of Earth and Space Sciences, University of California, Los Angeles, USA

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CAMBRIDGE UNIVERSITY PRESS
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo, Delhi

Cambridge University Press
The Edinburgh Building, Cambridge CB2 8RU, UK

Published in the United States of America by Cambridge University Press, New York

Information on this title www.cambridge.org/9780521873628

© F. D. Stacey and P. M. Davis 2008

This publication is in copyright. Subject to statutory exception
and to the provisions of relevant collective licensing agreements,
no reproduction of any part may take place without
the written permission of Cambridge University Press.

First published 2008

Printed in the United Kingdom at the University Press, Cambridge

A catalogue record for this publication is available from the British Library

Library of Congress Cataloguing in Publication data

ISBN 978-0-521-87362-8 hardback

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the persistence or accuracy of URLs for external or
third-party internet websites referred to in this publication,
and does not guarantee that any content on such
websites is, or will remain, accurate or appropriate.

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Contents

Preface		page xiii
1	Origin and history of the Solar System	1
1.1	Preamble	1
1.2	Planetary orbits: the Titius–Bode law	3
1.3	Axial rotations	4
1.4	Distribution of angular momentum	5
1.5	Satellites	6
1.6	Asteroids	7
1.7	Meteorites: falls, finds and orbits	8
1.8	Cosmic ray exposures of meteorites and the evidence of asteroidal collisions	10
1.9	The Poynting–Robertson and Yarkovsky effects	11
1.10	Parent bodies of meteorites and their cooling rates	15
1.11	Magnetism in meteorites	17
1.12	Tektites	18
1.13	The Kuiper belt, comets, meteors and interplanetary dust	19
1.14	The terrestrial planets: some comparisons	21
1.15	Early history of the Moon	23
2	Composition of the Earth	27
2.1	Preamble	27
2.2	Meteorites as indicators of planetary compositions	30
2.3	Irons and stony-irons	31
2.4	Ordinary and carbonaceous chondrites	31
2.5	Achondrites	34
2.6	The solar atmosphere	34
2.7	The mantle	35
2.8	The core	37
2.9	The crust	40
2.10	The oceans	42
2.11	Water in the Earth	43
2.12	The atmosphere: a comparison with the other terrestrial planets	45
3	Radioactivity, isotopes and dating	48
3.1	Preamble	48
3.2	Radioactive decay	49
3.3	A decay clock: 14C dating	50
3.4	Accumulation clocks: K-Ar and U-He dating	50
3.5	Fission tracks	52
3.6	The use of isochrons: Rb-Sr dating	53
3.7	U-Pb and Pb-Pb methods	55
3.8	147Sm-143Nd and other decays	56
3.9	Isotopic fractionation	57
4	Isotopic clues to the age and origin of the Solar System	61
4.1	Preamble	61
4.2	The pre-nuclear age problem	61
4.3	Meteorite isochrons and the age of the Earth	63
4.4	Dating the heavy elements: orphaned decay products	65
4.5	Isotopic variations of pre-Solar System origin	67
4.6	Sequence of events in Solar System formation	70
5	Evidence of the Earth’s evolutionary history	72
5.1	Preamble	72
5.2	Argon and helium outgassing and the Earth’s potassium content	74
5.3	Evolution of the crust	75
5.4	Separation of the core	78
5.5	The fossil record: crises and extinctions	79
6	Rotation, figure of the Earth and gravity	81
6.1	Preamble	81
6.2	Gravitational potential of a nearly spherical body	82
6.3	Rotation, ellipticity and gravity	84
6.4	The approach to equilibrium ellipticity	87
7	Precession, wobble and rotational irregularities	90
7.1	Preamble	90
7.2	Precession of the equinoxes	91
7.3	The Chandler wobble	94
7.4	Length-of-day (LOD) variations	97
7.5	Coupling of the core to rotational variations	99
8	Tides and the evolution of the lunar orbit	102
8.1	Preamble	102
8.2	Tidal deformation of the Earth	103
8.3	Tidal friction	106
8.4	Evolution of the lunar orbit	108
8.5	The Roche limit for tidal stability of a satellite	111
8.6	The multiple moons hypothesis	114
9	The satellite geoid, isostasy, post-glacial rebound and mantle viscosity	117
9.1	Preamble	117
9.2	The satellite geoid	118
9.3	The principle of isostasy	122
9.4	Gravity anomalies and the inference of internal structure	125
9.5	Post-glacial isostatic adjustment	128
9.6	Rebound and the variation in ellipticity	132
10	Elastic and inelastic properties	135
10.1	Preamble	135
10.2	Elastic moduli of an isotropic solid	136
10.3	Crystals and elastic anisotropy	038
10.4	Relaxed and unrelaxed moduli of a composite material	141
10.5	Anelasticity and the damping of elastic waves	142
10.6	Inelasticity, creep and flow	144
10.7	Frequency dependent elasticity and the dispersion of body waves	147
11	Deformation of the crust: rock mechanics	149
11.1	Preamble	149
11.2	The tensor representation of stress and strain	149
11.3	Hooke’s law in three dimensions	151
11.4	Tractions, principal stresses and rotation of axes	152
11.5	Crustal stress and faulting	156
11.6	Crustal stress: measurement and analysis	159
12	Tectonics	163
12.1	Preamble	163
12.2	Wadati–Benioff zones and subduction	167
12.3	Spreading centres and magnetic lineations	171
12.4	Plate motions and hot spot traces	173
12.5	The pattern of mantle convection	177
12.6	Tectonic history and mantle heterogeneity	179
13	Convective and tectonic stresses	181
13.1	Preamble	181
13.2	Convective energy, stress and mantle viscosity	184
13.3	Buoyancy forces in deep mantle plumes	187
13.4	Topographic stress	188
13.5	Stress regimes of continents and ocean floors	191
13.6	Coulombic thrust wedges	193
14	Kinematics of the earthquake process	197
14.1	Preamble	197
14.2	Earthquakes as dislocations	198
14.3	Generalized seismic moment	203
14.4	First motion studies	206
14.5	Rupture models and the spectra of seismic waves	208
14.6	Earthquake magnitude and energy	212
14.7	The distribution of earthquake sizes	215
14.8	Tsunamis	219
14.9	Microseisms	222
15	Earthquake dynamics	224
15.1	Preamble	224
15.2	Stress fields of earthquakes	225
15.3	Fault friction and earthquake nucleation: the quasi-static regime	227
15.4	The dynamic regime	231
15.5	Omori’s aftershock law	232
15.6	Stress drop and radiated energy	233
15.7	Foreshocks and prediction ideas	237
16	Seismic wave propagation	239
16.1	Preamble	239
16.2	Body waves	240
16.3	Attenuation and scattering	242
16.4	Reflection and transmission coefficients at a plane boundary	247
16.5	Surface waves	251
16.6	Free oscillations	255
16.7	The moment tensor and synthetic seismograms	261
17	Seismological determination of Earth structure	267
17.1	Preamble	267
17.2	Refraction in a plane layered Earth	268
17.3	Refraction in a spherically layered Earth	271
17.4	Travel times and the velocity distribution	274
17.5	Earth models: density variation in a homogeneous layer	277
17.6	Internal structure of the Earth: the broad picture	278
17.7	Boundaries and discontinuities	279
17.8	Lateral heterogeneity: seismic tomography	284
17.9	Seismic anisotropy	289
18	Finite strain and high-pressure equations of state	294
18.1	Preamble	294
18.2	High-pressure experiments and their interpretation	296
18.3	The appeal to atomic potentials	299
18.4	Finite strain approaches	302
18.5	Derivative equations	303
18.6	Thermodynamic constraints	305
18.7	Finite strain of a composite material	307
18.8	Rigidity modulus at high pressure	309
18.9	A comment on application to the Earth’s deep interior	311
19	Thermal properties	314
19.1	Preamble	314
19.2	Specific heat	316
19.3	Thermal expansion and the Grüneisen parameter	319
19.4	Melting	323
19.5	Adiabatic and melting point gradients	326
19.6	Thermal conduction	327
19.7	Temperature dependences of elastic moduli: thermal interpretation of tomography	329
19.8	Anharmonicity	332
20	The surface heat flux	337
20.1	Preamble	332
20.2	The ocean floor heat flux	337
20.3	The continental heat flux	338
20.4	Lithospheric thickness	341
20.5	Climatic effects	346
21	The global energy budget	348
21.1	Preamble	348
21.2	Radiogenic heat	349
21.3	Thermal contraction, gravitational energy and the heat capacity	352
21.4	Energy balance of the core	356
21.5	Minor components of the energy budget	359
22	Thermodynamics of convection	361
22.1	Preamble	361
22.2	Thermodynamic efficiency, buoyancy forces and convective power	362
22.3	Convection through phase transitions	364
22.4	Thermodynamic efficiency of mantle convection and tectonic power	366
22.5	Why are mantle phase boundaries sharp?	368
22.6	Compositional convection in the core	370
22.7	Thermodynamic efficiency of core convection and dynamo power	372
22.8	Refrigerator action in the core	374
23	Thermal history	376
23.1	Preamble	376
23.2	The rate of heat transfer to the oceans	378
23.3	The heat balance equation and mantle rheology	380
23.4	Thermal history of the mantle	382
23.5	Cooling history of the core	385
24	The geomagnetic field	389
24.1	Preamble	389
24.2	The pattern of the field	391
24.3	The secular variation and the electrical conductivity of the mantle	397
24.4	Electrical conductivity of the core	402
24.5	The dynamo mechanism	405
24.6	The westward drift and inner core rotation	410
24.7	Dynamo energy and the toroidal field	411
24.8	Magnetic fields of other planets	414
25	Rock magnetism and paleomagnetism	417
25.1	Preamble	417
25.2	Magnetic properties of minerals and rocks	418
25.3	Secular variation and the axial dipole hypothesis	422
25.4	Geomagnetic reversals	427
25.5	Paleointensity – the strength of the ancient field	432
25.6	Polar wander and continental drift	434
26	‘Alternative’ energy sources and natural climate variations: some geophysical background	438
26.1	Preamble	438
26.2	Natural energy dissipations	440
26.3	‘Alternative’ energy sources: possibilities and consequences	442
26.4	Orbital modulation of insolation and solar variability	445
26.5	A concluding comment regarding ‘alternative’ energies	447
Appendix A General reference data		448
Appendix B Orbital dynamics (Kepler’s laws)		454
Appendix C Spherical harmonic functions		457
Appendix D Relationships between elastic moduli of an isotropic solid		462
Appendix E Thermodynamic parameters and derivative relationships		464
Appendix F An Earth model: mechanical properties		469
Appendix G A thermal model of the Earth		472
Appendix H Radioactive isotopes		474
Appendix I A geologic time scale		476
Appendix J Problems		477
References		496
Name index		514
Subject index		521

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