My first words when meeting a new class at the beginning of every semester, whether an introductory physical geology course or a graduate seminar, are always more or less the same: “Geology does not exist!”. Some students start frantically going over their schedules, wondering whether they are in the right room, but most of them just stare at me, wondering whether I am a lunatic. While they do this I explain that what I meant was that the Earth and other planets are complex systems in which every process can, and must, be dismantled until we can understand it in terms of the simplest possible physics and chemistry. This does little to put them at ease, but over the course of the first few weeks of class many of them come to understand what I mean, and even to agree with it.

This brings me to the several reasons why I decided to write this book. First, although a few good textbooks on thermodynamics applied to Earth systems are available, I find that none of them goes into the fundamentals of thermodynamics with the depth that I am convinced is necessary. Rather, they tend to discuss the foundational principles of thermodynamics on a “need to know” basis. My approach is exactly the opposite: build a solid understanding of the foundations of thermodynamics first, and explain everything else in terms of this understanding.