A point at which a landform switches, as in the change from an incision stage to an accumulation stage on the slopes of semiarid areas (Gutiérrez-Elorza and Peña-Monné (1998) Geomorph. 23, 2–4). An intrinsic threshold indicates possibly independent changes within the system; see Hugenholtz and Wolfe (2005) Geomorph. 70, 1–2 on the activation of a dunefield, while an extrinsic threshold indicates a response to change in an external factor; see Brunsden (2001) Catena 42, 2–4.
Subjects: Earth Sciences and Geography.