Triggers of Landslides, The Conditions and Driving Forces Involved


Triggers and driving forces


Case Studies



Landslides are catastrophic mass wasting events that can create devastating consequences for communities. Slope stability is determined by a body of material remaining in equilibrium (stable) as long as the sum of the stress on the slope does not exceed the sum of the shear strength of the slope materials (Ritter et al. 2002). Landslides are slope failures that are initiated by slippage along a well-defined planar surface (Ritter et al. 2002). The bedrock that the landslide slips along or slumps is in a fixed position but will occasionally break apart as the material slides.

Types of landslides include rotational and translational. On the scale of intensity landslides are on the bottom end compared to flows.  Creep, a slower mass movement can play a role in a land- slide but may only occur before or after the landslide. Saturation of the moving material determines weather the movement is a landslide or a flow. With an increase in saturation in the  material, the movement will have an increase in velocity. Landslides contain drier material and only move along a fixed planar surface vs. flows which contain more saturated material and move more rapidly.

The triggers and driving forces of landslides range from earthquakes to anthropogenic. Gravity plays the dominate role in any landslide and is a constant force working 24 hours a day. Locations susceptible to landslides are areas with high relief, land degradation, areas subject to high rain fall and regions subject to seismic activity. A typical landslide is a mass whose center of gravity has moved downward and outward, there is a tear-away zone upslope where material has pulled away, and a pile-up zone where material accumulated (Abbott 2004). 



Landslide over basalt, extending across Washington State Highway 4. Notice the clump of trees in the middle of the slide. This marks the end of the translation and the begining of a flow.
Source: Schuster, R. L.




Triggers and Driving Forces
Rotational and Translational Landslides
Case Studies



Website author: Nathan P. Beaver, University of Wisconsin Eau Claire, Geography 361, Spring 2004