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self-organization


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In geomorphology, the patterns that arise autogenically; independently of any external forcings (Chin and Phillips (2007) Geomorph. 83, 3–4). Examples include the formation of evenly spaced, nearly uniform ripples on sand dunes or stream beds, or of patterned ground in periglacial landscapes. ‘Nonlinear, dissipative interactions among the small- and fast-scale constituents of a system give rise to order at larger spatial and longer temporal scales’ (Phillips (2003) PPG27, 1). ‘Those not convinced by arguments of self-organisation and inherent behaviour as an explanation in itself commonly ask the mechanism of the changes. Even for those who support the theory, questions still arise of how the self-organisation takes place and how the changes are communicated from one part of the system to another such that order emerges’ (Hooke (2007) Geomorph. 91, 3–4).

Self-organized criticality

describes a system in dynamic equilibrium near a threshold condition The concept arises from Bak et al. (1987) Phys. Rev. Letts 59, 4, who develop a simple cellular automaton model in which sand is added, grain by grain, to a surface to form a pile. When local slopes become too steep a collapse occurs, moving sediment to neighbouring cells, which too can collapse if the adjusted slopes are too steep. See Coulthard and Van De Wiel (2007) Geomorph. 91, 3–4.

Subjects: Earth Sciences and Geography.


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