Riddles in Stone covers a variety of fascinating controversies and startling differences of opinion that accompanied the evolution of the study of Earth Sciences in southern Africa. This encyclopaedic book is the result of a lifetime's work. Although scrupulously rooted in scientific literature, it maintains an accessible and entertaining tone and shows how consensus amongst a majority may be proof of nothing. Geologists, challenged to interpret events that took place billions of years ago, often beneath the Earth's surface, have drawn up theories and hypotheses which may appear either absurdly dated or, from other perspectives, as cutting edge. The introduction of fresh ideas (as in the Plate Tectonic model) or new techniques (as in the dating of rocks using radioactive decay) can re-align the thrust of science, leading to the abandoning of traditional ideas and the embracing of new ones.