The term for the measure of deformation of a material, either a volume change or a shape change, is call strain . Elastic Moduli Different elastic materials respond to stresses with a different degree of strain. For example, if I pull on a sponge it deforms much more easily than a rock. The elastic modulus is the measure of a material's resistance to strain. Just like density, the elastic moduli change with pressure and temperature.
Pressure tends to increase the modulus, temperature tends to decrease the modulus.
A rock's elastic moduli are characteristic of that rock type and are controlled by the rock's mineral content. We can measure a rock's elastic moduli in a laboratory. In elastic material, disturbances that transmit energy called elastic waves . Seismic waves are elastic waves that travel through Earth. Surface Waves P waves travel fastest and thus are the first waves to arrive.