answer:It’s more the aftermath of the aerial debris and the resulting earthquake(s). It’d be difficult to breathe, sunlight would be filtered if not outright blocked out, Water supply would be polluted throughout North America, and vegetation would die out leading to a massive food crisis. However, the effects of a super volcanic eruption tend to be overrated. No super volcanic event in history has been identified as an extinction level event and the effects of Yellowstone erupting are further minimized as scientists discovered that the magma laying therein doesn’t contain much in the way of sulfur so we’re probably not looking at a long and drastic climate change in the event Yellowstone erupted. In short, we’re probably not as screwed as people make us out to be. Though those in close proximity would be very much dead. And considering the aftermath being the killer, elevation probably isn’t going to be saving you.