Avalanche Dynamics in Piles of Two Types of Sand

Some real systems usually drive themselves into a critical state. These systems are said to be in a state of selforganized criticality [1]. The theory of self-organized criticality aims to describe interactive, dissipative and self sustaining systems with many degrees of freedom. Hence it complements the chaos concept. These systems are characterized by power law statistics. Self-organized criticality has applications in many fields, e.g., sand piles [2, 3], earthquake dynamics [4, 5], dynamics of biological populations [6], interacting economic systems [7], etc. The statistics of the systems which display self-organized criticality are characterized by power law distributions [1] of the form