Very nice! I tried this as well some time ago, and came up with this. The hard part is to get the lava really glowing (shining light upon its surroundings), so I tried a reflective shader at the edges of the lava stream, but it didn't give the required result.
This is a voronoi rock base displacement on a fractal terrain, and a plane with the same fractal terrain (the lava), but without the voronoi displacement. If I remember right.