That's typically the type of effect one would use acrylics for
But I guess the same effect can be obtained using the right oil colors too.
I think you'll find Laszlo's
website interesting.
The idea is to have bright yellow deep in the crevices, then orange overall, followed by bright red, to deep red to almost black, where the lava is the coldest.
You can also read Vincent Hudon's Magmatrax tutorial
here It's in french, but the images speak for themselves.
edit: found an
english version