Hey Artice-3D. That's one of my discarded tests for the Iceland contest from a couple of years back. I was definitely surprised to see it pop up again. The short answer: World Machine+TG. I've attached an image of the WM setup; it's pretty limited in structure, relying on the SuperErosion plugin (the precursor to Geoglyph) and with another simple .ter file as the input. The TG setup is equally simple. I'm curious as to what aspect of the terrain you found interesting?
I've followed your earlier postings with great interest, and with anticipation of some possible sharing of insights into your process.