The second edition of Principles of Igneous and Metamorphic Petrology follows the same general approach as the first edition. The book is designed to introduce igneous and metamorphic petrology to those who have completed introductory college-level courses in physics, chemistry, and calculus. Its emphasis is on principles and understanding rather than on facts and memorization. With this approach, it is hoped that students will not only gain a sound understanding of petrology but will develop skills that can be applied to the analysis of problems in many other fields of Earth Science. <...>

Igneous petrology was to some extent essentially a descriptive science until about 1960. The results were mainly obtained from field work, major element analyses, and microscopical studies. During the 1960's two simultaneous developments took place, plate tectonics became generally accepted, and the generation of magmas could now be related to the geodynamic features like convection cells and subduction zones. The other new feature was the development of new analytical apparatus which allowed high accuracy analyses of trace elements and isotopes. In addition it became possible to do experimental studies at pressures up to 100 kbar. <...>

Mathematical astrophysics and mathematical geophysics have their own journals and conferences, where practitioners discuss mathematical formulations that come to grips with the physical processes of the cosmos and planet Earth. Mathematical petrophysics is by no means new. It started in 1942 with the publication of an equation: the Archie equation.

Two words are used to describe the result of a stress: ‘deformation’ and ‘strain’. Deformation is a general term describing the change of shape, size and/or position of an object, while strain (or ‘internal’ deformation) is used when associated with some quantification of shape change. (Note that in French, deformation is used for both meanings.)
No stress, no deformation. Let us begin with deformation, which is the consequence of applying some stress. In the following section, however, symbols referring to a stress will naturally appear here and there. They name the principal directions of push (σ1) and pull (σ3). <...>