English: This diagram illustrates pure shear deformation of a rock body. The undeformed rock (at upper left) is subject to pure shear that deforms it into the configuration at upper right.) The shear can be broken down into a stretching component, at lower left, and a rotation, at lower right. The stretching component compresses the rock in one direction and extends it in the perpendicular direction to produce foliation in the rock, indicated by the deformed grains and associated foliation planes. The foliation planes are oblique to the direction of shear.