This book was finished in June 1993, almost 11 years since the first edition of Reversals of the Earth's Magnetic Field was finished (published by Adam Hilger Ltd 1984). It has often been said that the typical doubling period for the accumulation of scientific knowledge during the last two centuries is about 15 years. This is certainly true for reversals of the Earth's magnetic field if we substitute data and theoretical modelling for scientific knowledge. We have accumulated a vastly increased amount of data, most of it with much greater precision. Our knowledge of the physics of the geodynamo has also been greatly expanded, but we still do not know the detailed mechanism of the generation of the field, and even less about the reversal process.

This book is an attempt to summarize the most important advances that have been made in the last decade. The general layout of the first edition has been preserved. The first chapter is a brief overview of the Earth's magnetic field and the second chapter discusses the magnetization of rocks. This chapter has been expanded and discusses some of the problems that have now been highlighted in the acquisition of natural remanent magnetization. Chapter 3 discusses in general terms the morphology of geomagnetic reversals and gives some of the early development of the subject. These three chapters lay the background for the next three chapters, which form the heart of the book. Chapter 4 deals with excursions of the magnetic field and chapter 5 with models and possible reversal mechanisms. Chapter 6 is a new chapter on transition fields, a topic that has attracted much attention in recent years and is still highly controversial.