But it will be 500,000 years before it erupts so not to worry.
A team from the University of Utah have told the American Geophysical Union Fall Meeting in San Francisco that Yellowstone’s magama chamber is 2.5 times larger than previously thought.
It is an underground cavern measuring some 55 miles by 20 miles and containing between 125 and 185 billion cubic miles of molten rock.
If it blows it will wipe out America – and have enormous impacts on the rest of the world.
The university researchers described their discovery as “astounding.”