I love the concept, and for the most part, you have executed it quite well.



If you look at it very closely, however, the illusion of the lava in the cracks gets a little shakier.



Next time, you may consider selecting the cracks out by hand (perhaps covering them with a brush on a separate layer and then selecting the contents of that layer), and then applying your lava-ish image to those regions only.



Still, the concept and composition is very impressive.