Landslides are caused by both human and natural interference, but mostly human. Mining and excavation hollow out the edge, which can cause it to collapse on itself and make a landslide. Earthquakes and erosion also have that same affect. Construction can put weight on the edge and to much weight will cause it to fall.
During landslides, man made and natural objects can be moved by landslides. With enough force, this can create a domino effect with nearby edges, cliffs, and hills. While sweeping up everything in its path, the landslide also leaves parts of it behind which causes blockages. This leaves massive amounts of property damage, that is if you assume that there is any property left. There is a major chance in death or injury for both people and wildlife.