Cooling lava

Start with the volcanic rocks.

Heavy drybrush Charred Brown. Slop a bit over the base of the rocks. This gets a subtle glow effect going, and leaves the lava almost cooled out black around the rocks.

Start the gradient with Bloody Red. Blend a bit of Charred Brown at the edges to smooth the transition. Continue with Hot Orange; feather the ends.

Carry on with Orange Fire, then 1:1 Orange Fire and Sun Yellow mix.

Finally, just a bit of pure Sun Yellow at the edges, where the lava would be the hottest.