The revolution in geological thinking generally referred to as plate tectonics has brought in its wake both a rash of new terminology and a modification of established terms. This new edition of John Challinor's long-established dictionary incorporates the most important of these new terms and meanings, showing derivation and varying uses of the terms and changes in use through time. With copious quotations from the whole of geologic literature, this volume will be both an invaluable reference and a stimulating source of geologic history and theory.