Your question about a time-portrait of a person's face is reminsicent of "The Picture of Doiran Gray", and it might be the basis of a good dimensional tale, complete, perhaps, with some interactive illustrations. How could you literally "flesh out" this project? Could you relate it to some of the investigations that are carried out in the geological example you mentioned? Instead of keeping track of what happens along a mountain ridge over time, you can concentrate on the eyebrow, or perhaps the receding hairline, arrested by some monoxydin or implant surgery, corresponding to the prairie-forest boundary? It has possibilities.