We report particle dynamical simulations of a two-dimensional grain pile in a box with the base being slowly tilted from horizontal to [Formula Presented] angle at which the pile undergoes a large layer sliding event. When dissipation between the grains is negligible, the distribution [Formula Presented] of displacements [Formula Presented] of the surface grains shows decays that are consistent with [Formula Presented] with [Formula Presented] for [Formula Presented] At time [Formula Presented] at [Formula Presented] we find a crossover in τ to [Formula Presented] Dissipation appears to play a key role in the system dynamics only when [Formula Presented] We find that the time for the onset of avalanches, [Formula Presented] where [Formula Presented] is the time when the surface roughness of the sliding pile is minimized. © 1997 The American Physical Society.