Internal and External Causes of Working on Self-Organized Criticality of Sand-piles

Internal causes of working on selforganized criticality of sandpiles are the size and structure of sandpiles, and external cause is the outside perturbation. The size and structure of sandpiles determine sandpiles whether or not can appear selforganized criticality. Different ways of perturbation has different critical point at which selforganized criticality appears; Different intensity of perturbation causes branching between selforganized criticality and nonselforganized criticality; The perturbation shows how selforganized criticality appears and the critical point at which it appears; The perturbation works on selforganized criticality only by the size and structure of sandpiles. Selforganized criticality appears when internal and external causes act each other, and maintain macroscopic stabilization of sandpiles in the critical state. 