What Would Happen If Yellowstone Erupted?

If you've ever wondered why Yellowstone National Park has geysers like Old Faithful, it's because it sits on top of an active supervolcano. It's a ticking geological time bomb which, according to the US Geological Survey, has erupted thrice in the past two million years. Moreover, the thing could possibly blow in the next couple thousand years...but that it's y'know, extremely unlikely that it'll actually happen within that timeframe, with the USGS giving it a 0.00014 percent chance of occurring.

Geologists at USGS classify supervolcanos as volcanic centers that have had eruptions covering more than 240 cubic miles. Yellowstone is one of two supervolcano locations in the US, the other being located in California's Long Valley. 

Though it's estimated we've got at least a millennia before it'll erupt again — if it ever erupts again at all — the USGS says that it would likely affect the global climate for years to decades. Surrounding states would experience pyroclastic flows, also known as molten lava (not to be confused with molten lava cake), along with falling molten rock. But far more deadly would be the molten ash cloud, which could reach up to 500 miles wide, choking everything in its path with a thick blanket of ash. Crops and livestock would suffer, reducing our food supply while our streams and rivers would become temporarily clogged, and sulfur dioxide released into the atmosphere would trigger global cooling, further affecting the worldwide crop supply.

While a Yellowstone eruption would definitely be a cause for concern, it would be unlikely to cause human extinction. If that doesn't put you at ease, rest assured that the USGS has calculated the yearly risk of an eruption and it's pretty low, coming in at 1 in 730,000 — or that aforementioned 0.00014 percent chance.

The USGS explains that we would likely be able to predict an eruption months to possibly years in advance, and that the majority of eruptions at Yellowstone have not been catastrophic. In fact, the last eruption to have occurred was a relatively benign lava flow at Pitchstone Plateau over 70,000 years ago. So you're free to check out the bison without fear of stepping into a real-life Dante's Peak.