Influence of Slope Angle on Mass Movement

An increase in slope angle increases shear stress 

- there is an increase in the forces pulling materials downward so mass movement is more likely to happen

An decrease in slope angle decreases shear stress

- there is a decrease in the forces pulling materials downward so mass movement is less likely to happen

So, steep slopes are more likely to have mass movement on them & shadow slopes are less likely to have mass movement on them

Critical angle of repose = the steepest angle of descent to which a material can be piled without slumping downwards. At this angle the material on the stope face is on the verge of sliding.

The critical angle of repose influences mass movement.

The angle of repose varies from 0 to 90° depending on the rock type.

If angle of slope is greater than the critical angle of repose then mass movement will happen.

Critical angle of repose for:

Chalk is 45°

Snow is 37°

Gravel is 25°