In less than two minutes 40 million cubic yards of rock from Turtle Mountain slid along a plane of structural weakness to cover the town of Frank, Alberta, Canada in 1903. The link in the Chapter Heading will take you to the National Landslide Information Center where you can read about this type of Mass Movement. The following factors help to determine the slope stability.
Shear strength is a measure of the ability of an object to withstand a change in shape.
If the component parallel to the slope is the dominant component this helps cause instability. The USGS has several useful links for those wishing to learn more about Landslides . The higher the water content the less stable the slope. Water may percolate into the material and decrease friction between the grains, which lowers the shear strength. Vegetation - vegetation can absorb water which can prevent water from percolating into the unconsolidated material.