Objectives

The purpose of this book is to present the principles of convection, to show how those principles apply in the peculiar conditions of the earth's mantle, and to present the most direct and robust inferences about mantle convection that can be drawn from observations. The main arguments are presented in as simple a form as possible, with a minimum of mathematics (though more mathematical versions are also included). Where there are controversies about mantle convection I give my own assessment, but I have tried to keep these assessments separate from the presentation of principles, main observations and direct inferences. My decision to write this book arose from my judgement that the broad picture of how mantle convection works was becoming reasonably settled. There are many secondary aspects that remain to be clarified.

There are many connections between mantle convection and geology, using the term ‘geology’ in the broadest sense: the study of the earth's crust and interior. The connections arise because mantle convection is the source of all tectonic motions, and because it controls the thermal regime in the mantle and through it the flow of heat into the crust. Some of these connections are noted along the way, but there are three aspects that are discussed more fully. The first is in Part 1, where the historical origins of the ideas that fed into the conception of mantle convection are described. Especially in Chapter 2 those historical connections are with geology. Another major connection is through Chapter 13, in which the relationship between mantle chemistry and mantle convection is considered. The third respect arises in the last chapter, where the broad tectonic implications of hypothetical past mantle regimes are discussed.