Terrain - Slope angle. Most large slab avalanches run on slopes between 25 and 45 degrees. Smooth ground such as rock slab is predisposed to full depth avalanches. Rough ground such as large boulders will tend to anchor base layers in position, making avalanches less likely. Once these boulders are covered, however, surface avalanche activity is unhindered.
Convex slopes are generally more hazardous than uniform or concave slopes.
The point of maximum convexity is a frequent site of tension fractures, with the release of slab avalanches. Although it turned out that such models are not able to describe real sandpiles, this work initiated a lot of interest in granular materials and especially sandpiles. The angle of repose, the angle between the horizontal and the surface of the pile, is an important characteristic. Since Bagnold's fundamental work the angle of repose is normally thought to be connected to an effective dynamic friction coefficient of the granular material. It emphasizes the role of energy restitution and geometry.