As we prepared our revisions for this second edition of Geodynamics we were struck by the relatively few changes and additions that were required. The reason is clear: this textbook deals with fundamental physical processes that do not change. However, a number of new ideas and concepts have evolved and have been included where appropriate.

In revising the first chapter on plate tectonics we placed added emphasis on the concept of mantle plumes. In particular we discussed the association of plume heads with continental flood basalts. We extensively revised the sections on comparative planetology. We have learned new things about the Moon, and the giant impact hypothesis for its origin has won wide acceptance. For Venus, the Magellan mission has revolutionized our information about the planet. The high-resolution radar images, topography, and gravity data have provided new insights that emphasize the tremendous differences in structure and evolution between Venus and the Earth. Similarly, the Galileo mission has greatly enhanced our understanding of the Galilean satellites of Jupiter.

In Chapter 2 we introduce the crustal stretching model for the isostatic subsidence of sedimentary basins. This model provides a simple explanation for the formation of sedimentary basins. Space-based geodetic observations have revolutionized our understanding of surface strain fields associated with tectonics. We introduce the reader to satellite data obtained from the global positioning system (GPS) and synthetic aperture radar interferometry (INSAR).