An article at Before It's News website on the Yellowstone supervolcano and what would happen if it exploded. It notes:
That volcano has shown all the signs of becoming active: parts of the ground have heated to just under 1,000⁰ F while the earth is bulging from a building lava dome and a lake has completely boiled away.
Just two years ago many geophysicists assured everyone, including the federal government, that there really wasn't anything to worry about. Really.
Now those same scientists have shut up. If they talk at all to curious reporters they respond only in clipped monotones and then hurry away.
What are they worried about? Approaching Doomsday.