Yellowstone does set on a huge caldera that has erupted in the past and is likely to erupt again in the future. Beyond that the story was typical fiction based on simple facts and cheesey characters.
If the caldera erupted tomorrow there wouldn't be anything we could do to stop it and huge numbers of people would die. It's one of those things not worth worrying about.
I watched it last night too, moat of the main characters were from the Star Gate series on SCiFi,was slow, and didn't need to be 2 1/2hrs.