What is strain in geology?

Strain in geology refers specifically to the change in shape, size, or volume that occurs in response to an applied stress. When rocks are subjected to external forces, they undergo deformation, resulting in a change in their structure. This deformation can manifest in various forms, such as elongation, compression, or shear. Strain effectively quantifies how much a material has been altered from its original configuration due to these applied stresses.

While other concepts such as force and pressure relate to the causes of deformation in rocks, they do not encapsulate the effect that results from those forces. Strain focuses on the resultant changes within the material itself, which is a critical aspect of understanding geological processes such as folding, faulting, and the overall structural behavior of the Earth's crust.