1 The chronostratigraphic equivalent of the time unit period. Systems are subdivided into series, and together several systems constitute an ‘erathem’. When used formally the initial letter of the term is often capitalized, e.g. the Devonian System.
2 In geomorphology, a natural arrangement of interrelated objects or variables, the whole possessing properties that make it greater than the sum of the individual parts. It normally possesses stability, expressed by a balance between the input and output of energy and matter. This equilibrium may be upset by internal or external change. If the change is modest, the system quickly regains equilibrium; if it is extreme, a new equilibrium is established. A hillslope, for example, receives precipitation and exports water, slope debris, and the products of weathering. The form of the profile represents a balance between input and output. A landslide, perhaps induced by an increase in precipitation, would destroy this equilibrium, and in due course a new balance would be established. Several varieties of system are recognized. See cascading system; control system; morphological system; and process-response system.