Isostasy is a simple concept, yet it has long perplexed students of geology and geophysics. This fully updated edition provides the tools to better understand this concept using a simplified mathematical treatment, numerous geological examples, and an extensive bibliography. It starts by tracing the ideas behind local and regional models of isostasy before describing the theoretical background, the observational evidence. It now also includes an exploration of the role of flexure in landscape evolution and dynamic topography and discussions of lithosphere memory, inheritance, and new NASA mission topography and gravity data. The book concludes with a discussion of flexure's role in understanding the evolution of the surface features of the Earth and its neighboring planets. Intended for advanced undergraduate and graduate students of geology and geophysics, it will also be of interest to researchers in gravity, geodesy, sedimentary basin formation, mountain building and planetary geology.