What sort of extension are you looking at? Tectonic autogeneration of terrain has been done, but there's definitely room for improvement. Carl Davidson has a nice web app in javascript to simulate tectonic motion on a sphere,
here. It takes a pretty high-end browser, because it takes advantage of WebGL for client-side processing. Not perfect, but the best of the lot. I know of a couple of similar python apps.
One, by the same author as the previous app, is understandably very similar in approach, but it uses python, which you might find instructive.
Another, also in python, uses a somewhat different approach, which might be similarly instructive. It also looks like, in some ways, a more interesting approach.