I rewatched some How The Earth Was Made, and got to the Yellowstone episode. Reminded me that not only are we overdue for another supereruption (600,000 year average between these and we're at something like 630,000), but the land is upswelling and earthquaking more in the last two decades, which are the signs you'd expect to increase in frequency before the next event. Maybe that's a slow build (say, for the next thousand years). I don't know.
