Plate tectonic theory has revolutionized the study of the history of our planet. It is now becoming increasingly apparent that processes deep within the Earth's mantle and core strongly influence plate movements, and it is to these processes that the author addresses himself. Having discussed the origin, composition, structure and physical properties of the Earth, the book turns to discuss the key role that interactions between the mantle and core play in magmatic and tectonic processes. Other important issues discussed are the nature and existence of mantle plumes and convection cells, and the similarities and differences of tectonic processes on other planets in the solar system. These and other questions are discussed in the context of the Earth's origins, its chemistry and its physics. All geophysicists and geologists concerned with earth evolution and plate tectonics should find much of interest in this book.