This image started it's life as a simple(?) canyon scene with more or less completely procedural materials (it uses two bitmap masks). I then created a tutorial of how I created that material and while doing that I started playing with the idea of adding lava to the scene, which I eventually did. The render was then processed in Photoshop to give it a bit of extra oomph.
The tutorial is avaliabe at my site www.urgaffel.com and at www.3dtotal.com. Thanks go to Allan McKay (www.allanmckay.com) for his procedural lava tutorial that I looked at to figure out what a nice procedural lava looks like