The family of rocks that have been transformed from their original condition, by being subjected to a change in the physico‐chemical conditions of their environment. All transformations short of melting are included in metamorphism (for example, dehydration, decarbonation, new mineral formation, and recrystallization). Ultrametamorphism (also called anatexis) marks the beginning of melting, and the transition into the igneous realm.Metamorphosed soils are not unknown, a typical occurrence being beneath lava flows where temperatures in excess of 300 °C may persist long enough to dehydrate hydroxide and clay minerals at least partially (see Figure T7, and Chesworth et al., 1985).