This is the second edition of a treatment of the origin, structure and internal composition of the Earth, synthesizing the geological, chemical and physical knowledge bearing on the Earth's inaccessible interior. It seeks answers to questions about the Earth's origin, evolution and dynamics, producing an integrated account of these subjects suitable for students and teachers in the earth sciences. Why do we think that the centre of the Earth is a nickel-iron alloy; or that the crust evolves by processes at subduction zones and by vertical plumes rising through the mantle; or that the Earth's magnetic field is generated by some form of convection in the molten outer core? The evidence comes from many disciplines ranging from geology to nuclear physics, but the contributions of geophysics and geochemistry are particularly important and have been given equal weight, while mathematics has been kept to a minimum. The text traces the evolution of the earth's layered structure and explains how its density at depth is deduced from seismic and gravitational data. Density is the prime constraint on chemical composition which is deduced also by reference to new theories of stellar evolution and planetary accretion, combined with evidence from the solar system and meteorites. With this information as background, the second half of the text goes on to describe the probable composition and physical state of the present-day core, mantle and crust. In the second edition, more emphasis is placed on the effects of heat and gravity on dynamic processes at all levels in the Earth. Effects such as stresses in tectonic plates, mantle convection and the geomagnetic dynamo are re-examined in the light of improved understanding. Finally, geological evidence is used to construct a model for the evolutionary history of the Earth's continental crust.

Table of Contents:
1 Introduction.- 1.1 Aims and objectives.- 1.2 'The Inaccessible Earth': an outline.- 1.3 History of ideas about the Earth.- Further reading.- 2 The contribution of seismology.- 2.1 Seismic waves.- 2.2 Deduction of P- and S-wave velocities at depth.- 2.3 Seismic velocities and the structure of the Earth.- 2.4 Surface waves.- 2.5 Free oscillations of the Earth.- Summary.- Further reading.- 3 The density within the Earth.- 3.1 Introduction.- 3.2 The mass of the Earth.- 3.3 The moment of inertia of the Earth.- 3.4 The simple self-compression model: the Adams-Williamson equation.- 3.5 Defects of the self-compression model.- 3.6 More sophisticated models and a contemporary result for the Earth's density variation.- Summary.- Further reading.- 4 The formation of the Solar System and the abundances of the elements.- 4.1 Why it is necessary to look outside the Earth.- 4.2 Introducing the Solar System and the Galaxy.- 4.3 Formation of the Solar System.- 4.4 Abundances of the elements.- 4.5 Meteorites and asteroids.- Summary.- Further reading.- 5 The accretion and layering of the terrestrial planets.- 5.1 The first 100 million years.- 5.2 Pre-planetary chemical processes.- 5.3 Post-accretional chemical processes.- 5.4 The Earth-Moon system: a special relationship.- 5.5 Mars, Venus and Mercury: a postscript.- Summary.- Further reading.- 6 The Earth's core.- 6.1 Problems posed by the core.- 6.2 The Earth's magnetic field and the problem of energy.- 6.3 Energy sources for the dynamo: (a) thermal convection.- 6.4 Compositions of the inner and outer cores.- 6.5 Energy sources for the dynamo: (b) compositional convection.- 6.6 Temperature in the core.- Summary.- Further reading.- 7 The mantle and oceanic crust.- 7.1 Introduction.- 7.2 The upper mantle: mineralogical and chemical relationships.- 7.3 Experimental petrology and the upper mantle.- 7.4 Structure and evolution of spreading ridges.- 7.5 The transition zone.- 7.6 The lower mantle.- Summary.- Further reading.- 8 The dynamic mantle.- 8.1 Introduction.- 8.2 Rheology of the mantle.- 8.3 The thermal balance sheet: heat sources and sinks.- 8.4 Convection in the mantle.- 8.5 Temperature within the mantle.- 8.6 The Earth as a heat engine.- Summary.- Further reading.- 9 Evolution of the mantle.- 9.1 Introduction.- 9.2 Does convection cross the 660-km discontinuity?.- 9.3 Geochemical heterogeneity in the mantle.- 9.4 Synthesis.- Summary.- Further reading.- 10 The continental crust.- 10.1 The nature of the Earth's continental crust.- 10.2 Crustal structure, composition and rheology.- 10.3 Processes in zones of lithospheric convergence.- 10.4 Processes in zones of lithospheric extension.- Summary.- Further reading.- 11 Evolution of the Earth's continental crust.- 11.1 The framework of crustal evolution.- 11.2 Archaean and pre-Archaean Earth history.- 11.3 The Proterozoic.- 11.4 The Phanerozoic.- 11.5 Isotopes and crustal evolution.- 11.6 A history of the Earth and a final summary.- Further reading.- Postscript: the new state of ignorance.- Notes.- 1 Moment of inertia, angular momentum, etc..- 3 Electromagnetic stiffening, and heating.- 4 Radiometric dating.- 5 The atom and the nucleus.- 6 Electronegativity and the electronic structure of atoms.- 7 Earthquake fault-plane solutions.- 8 Gravity and the geoid.- References.