1. Ok first create a new document, i went for 350x150, and make sure it is set to transparent!
2. Filter>render>clouds
3. Filter>render>difference clouds
4. Press Ctrl+F as many times as you like, till you get something you like.
5. Press Ctrl+B
set the shadows to 80, 0, -80
set the midtones to 80, 0, -70
set the highlights to 60, 0, -70
6. We have finished that layer now, so create a new layer and put a linear gradient from one side to the other:
7. Filter>noise> add noise
amount 20
uniform
and check the monochromatic box
8. Filter render>blur>motion blur
angle 90
pixels 50
9. Blending options> Bevel and Emboss
Inner bevel
Chisel hard
depth- 1000%
size 1 or 2
Everything else left as default
Blending options>Drop shadow
(leave as default)
10. Select the Elliptical Marquee tool and a circles (by holding shift down) not too big though
11. press delete and you should be able to see the lava below, repeat stage 10 as many times as you like
Here is what i got....
More Tutorials: 
