Book excerpt: Water and other fluids play a vital role in the processes that shape the earth's crust, possibly even influencing earthquakes and volcanism. Fluids affect the movement of chemicals and heat in the crust, and they are the major factor in the formation of hydrothermal ore deposits. Yet, fluids have been overlooked in many geologic investigations. The Role of Fluids in Crustal Processes addresses this lack of attention with a survey of what experts know about the role of fluids in the Earth's crustâ€"and what future research can reveal. The overview discusses factors that affect fluid movement and the coupled equations that represent energy and mass transport processes, chemical reactions, and the relation of fluids to stress distribution.