Each year, millions of people flock to Yellowstone National Park to take in its peaceful natural beauty. But not far underneath the ground lurks a supervolcano which, when it erupts, threatens to wipe humanity off the face of the Earth. And as we reported recently, that could happen a lot sooner than scientists had thought.

While it doesn’t appear likely the volcano will erupt anytime soon, scientists recently discovered that it the conditions for an eruption could evolve over a matter of decades rather than hundreds of thousands of years. And when it does erupt, it will be quite a spectacular event, in a bad way.

The U.S. Geological Survey estimates that there have been three “supereruptions” in the last 2.1 million years, with the most recent being 631,000 years ago. If another one were to happen at Yellowstone, the USGS says, it would result in worldwide effects. Thick ash deposits would cover the United States, and volcanic gases would be injected into the atmosphere that would cause catastrophic effects in the global climate.

In states near the epicenter of the blast, like Wyoming, Idaho, Montana, and Colorado, an astonishing three feet of volcanic ash would cover the ground, killing all plants and animals.

A recent supereruption, the Toba eruption which happened 74,000 years ago in Indonesia, almost wiped out the human race when it happened as it triggered a global winter that may have lasted for a decade.

But ultimately, there’s not really much reason to worry about such an event. For one thing, there’s nothing you can do about it, for another, it likely wouldn’t happen in your lifetime, and for a third reason, which is that it may never erupt again, and even if it does it would most likely be a smaller lava flow.