MASS WASTING


The downslope movement of surface 
material under the direct influence of gravity 
is called "Mass Wasting."


Rapid Movements


Slow Movements



Gravity operates vertically but has a 
component acting parallel to the slope - this 
helps cause instability.




Angle of Repose



Rapid Mass Movements


Rockfalls  - Produced by rocks falling from 
near vertical cliffs, the rockfall is the smallest, 
most common, and most rapid from of mass 
wasting.



Rapid transport of mixture of soil, rock, and 
vegetation down a moderate to steep slope 
signifies a debris slide, avalanche, or flow. A 
debris slide is the driest, while a debris flow is 
the wettest.







Mudflows are the most fluid, rapid flow of 
mud, usually mixed with rocks and other 
debris, downhill. They generally occur 
following heavy rainstorms in arid regions, and 
follow preexisting channels, such as streams or 
valleys.




Earthflows are slow flowage of nearly saturated 
soils down moderate to steep slopes. Earth 
flows are more fluid, shallower,and smaller 
than slumps.






SLUMP - The intermittent movement (slip) of 
a mass of earth or rock along a curved plane is 
a slump. A slump is most likely to occur after a 
heavy rain, on a steep slope with deep, clay-
rich soils.


CREEP -  The slowest and least noticeable, but 
most widespread of the slow mass wasting 
categories is creep. Creep involves the entire 
hillside, and is characterized by very slow 
movement of soil or rock material over a 
period of several years.





Solifluction - downslope movement when ice 
melts in the upper portion of the soil


SHEAR STRENGTH is a measure of the 
ability to withstand a change in shape. 




slope material's strength and cohesion 



amount of internal friction between grains  





any external support of the slope