Are you trying to make a slope deform from an original position to the new slide debris field? It may be possible using the Animation version.
You would have to modify the erosion function of a heightfield terrain for each part and time scale of the slide. Objects can then be used on the surface to 'fall' down the slide using key framing. At least I think that would work. I don't know how to limit the area of the slide, unless the images were composited later.
