Several aspects of the physics of the crust may be distinguished for convenience, though they are necessarily interrelated: (1) the physical methods employed in the field to discover structure (i.e., gravitational, seismic); (2) the physical measurements of properties of geological materials required for the interpretation of field observations in terms of composition; (3) the physical conditions, such as pressure and temperature, which influence these properties; (4) the physical processes, particularly the transformations of energy, which give rise to geological dynamics. A brief review is given of subdivisions (2) and (3).