An admirer of Nature may be excused becoming enraptured when he takes a view from any of these noble terraces [in County Clare, Ireland]. Looking north, or south, his eyes are riveted on vast surfaces of gray limestone rocks, split up to an extent, and with a regularity of direction, truly wonderful … The observer becomes so absorbed with the scene that he unconsciously begins to feel as if the rocks under and around him were in process of being illimitably cleft from north to south–as if the earth's crust were in course of splitting up from one pole to the other; and he only rids himself of the feeling to become bewildered with the question, as to what mysterious agent produced the singular phenomenon he is contemplating (King, 1875).

In the preceding chapter we learned that the mechanical behavior of rock under certain conditions can be approximated with a linear elastic material, a mathematical construct formulated using Hooke's Law to relate stress and infinitesimal strain. The elastic material is useful for describing both ancient and modern deformation in the Earth at a variety of length and time scales. However, the limestone described by King as “illimitably cleft from north to south” provides an evocative example of fracturing which is inelastic, non-recoverable deformation. Even if the fracture surfaces were pushed back together they would not heal.