I wanted the rim to get a more-weathered look as the millions of years went by.
I just blended two shaders for the rim shader on the crater(shader). then animated a cross fade of sorts to do that. It could use some refinement but I was proud of the fact I could; think of a project, sit down for four hours, and get something close to what I imagined.
Usually, a project goes off in some crazy place because I did not understand concepts. The fog is slowly lifting.
I also used a heightfield operator to blend a masked heightfield for the basaltic plug. That was masked with a painted shader. But that was old hat.
Thanks for the encouragement,
Russ