I hope that I have time to do this one, I will give it my best!
My idea is to have the base flame behave similar to a super high pressure water beam that just blasts and melts through the environment. Something similar to these videos:
and then add impact effects that are sped up versions of the molten debris created by volcano eruptions:
I hope that this is enough to get me going, I was thinking of joining the last event but I just didn't have the time, will be looking forward to what everyone makes!