If the dreamer is witnessing the landslide as it happens, then sudden and unexpected events, which he really should be prepared for, will take him totally by surprise.
The dream is warning him to be prepared. Other symbols in the dream may reveal exactly what the events will entail, and what he should do about it. If the landslide has already taken place and the rocks are lying in the middle of the road, then the dreamer faces obstacles ahead that will need to be removed before he or she can move on and accomplish whatever it is that needs to be done.
