Extensional rheometry is commonly performed on materials that are subjected to a tensile deformation. Elastic deformation refers to a reversible deformation. This is known as elastic deformation or elasticity. Mechanical nociceptors respond to excess pressure or mechanical deformation. Photoelasticity describes changes in the optical properties of a material under mechanical deformation. Tesserae exhibit the effects of eons of compression and tensional deformation. This is distinct from elastic deformation, which is reversible. The cranial vault was subject to minor lateral deformation. The quartz diorite sheets were intruded during this Cadomian deformation and metamorphic event. This phenomenon is called "elastic deformation". The various moduli apply to different kinds of deformation. Used in conjunction with monitoring data on seismicity and deformation, correlative monitoring gains great efficiency. There are two types of primary brittle deformation processes. This is the basis of deformation mechanism maps. This type of deformation is also irreversible.