What Causes Landslides?
You can think of the different types of landslide material as a little like the different types of ice cream. Some is smooth and soft, some is smooth but thicker and doesn't flow as well, and some has chunks like nutty boulders and fruity vegetation. As you might imagine, all these consistencies would move differently.
The type of landslide that has to do with the structural combination of rock (the nuts), soil (the ice cream) and vegetation (the fruit) is the morphology. If a hillside has lost vegetation because of a fire for instance, then the addition of water can cause erosion, upping the chances for a landslide. It's not only rain that can cause erosion but flowing rivers, moving glaciers and crashing ocean waves. The geology, or strength of the earth material itself, can also be a factor in landslides. Stronger material is less likely to break apart and slide down the slope. And finally, there are human activities that can expose slopes to erosion and lead to landslides. Clearing land for agriculture or construction are some of the human causes of landslides.