Landslides are one of several natural disasters caused by plate tectonics. They are more common than other natural disasters and are most likely to occur in a relatively wet environment.
Other forms of landslides could be rock falls, mud slides and other sliding incidents. Shallow debris flows and deep failure of slopes also count as landslides. There is no average landslide, they are all different.
There are many different reasons why this disaster occurs. Some causes are: erosion, earth quakes, volcanic action, snow melt and chemical weathering. Chemical weathering is when water dissolves rocks and forms different chemicals that affect the stability of the land. This is my thought on landslides.