Book excerpt: This textbook explains how mountains are formed and why there are old and young mountains. It provides a reconstruction of the Earths paleogeography and shows why the shapes of South America and Africa fit so well together. Furthermore, it explains why the Pacific is surrounded by a ring of volcanos and earthquake-prone areas while the edges of the Atlantic are relatively peaceful. This thoroughly revised textbook edition addresses all these questions and more through the presentation and explanation of the geodynamic processes upon which the theory of continental drift is based and which have led to the concept of plate tectonics. It is a source of information for students of geology, geophysics, geography, geosciences in general, general natural sciences, as well as professionals, and interested layman.