Brittle deformation = the permanent change that occurs in a solid material due to the growth of fractures and/or sliding on fractures. A fracture is a surface of discontinuity (includes cracks, joints and faults). Faults result from shear stresses, and joints result from tensile stresses:
The change in volume or shape of an object that results from stress is called strain. The response of rocks to stress can be divided into - elastic response: rock returns to original shape - ductile or plastic response: permanent deformation without fracture; occurs above the so-called elastic limit