Time evolution of the largest avalanche event #1628 in the 2-D cellular automaton simulation with grid size N = 64². The 12 panels show snapshots at particular burst times from t = 26 to t = 690 when the energy dissipation rate peaked. Active nodes where energy dissipation occurs at time t are visualized with black and grey points, depending on the energy dissipation level. The starting point of the avalanche occurred at pixel (x,y) = (41,4), which is marked with a cross. The time-integrated envelop of the avalanche is indicated with a solid contour, and the diffusive avalanche radius r(t) = t^1/2 is indicated with a dashed circle. The temporal evolution is shown in a movie available in the on-line version.