What If the Yellowstone Supervolcano Erupts? | Unveiled

VOICE OVER: Noah Baum WRITTEN BY: Caitlin Johnson
According to some, the super-volcano at Yellowstone National Park in USA is long overdue an eruption... and when it does blow, it could trigger a global disaster on an apocalyptic scale! But how much of the legend surrounding Yellowstone is true? Should we really be worried about it erupting sometime soon? And will it really threaten mass extinctions when it does? In this video, Unveiled explores this iconic volcano to ask; What if Yellowstone erupts?

What if the Yellowstone Supervolcano Erupts?

Of all the threats facing humanity, natural disasters are some of the greatest and the most unpredictable. Even with the early warning systems we have in place now, it’s possible for major cities to be destroyed by hurricanes, tornadoes, earthquakes and volcanoes. But one disaster has loomed particularly largely in the media for decades, with repeated claims that we’re overdue for an event.

This is Unveiled, and today we’re answering the extraordinary question; what if the Yellowstone Supervolcano erupts?

In recent years it’s been a go-to topic when thinking about the apocalypse, but the supervolcano in Yellowstone National Park is actually much less active than some corners of the media make it seem… with regular, sensationalist articles claiming that we’re due an eruption in Wyoming “any day now”. The idea that an event is looming generally comes from our knowledge of past supervolcanic eruptions in the region, of which there have been three: one 2.1 million years ago, another 1.3 million years ago, and the most recent 640,000 years ago. Judging by the gaps between those three dates, some say we’re fast approaching (or perhaps are well inside) prime time for another eruption. Nevertheless, basing all our fears on an average gap between three numbers perhaps isn’t all that reliable. The chances are that if Yellowstone does erupt again, nobody on Earth today would be alive to see it. And even if it did blow tomorrow, it’s also possible that a volcanic eruption that isn’t a super-eruption could occur. Volcanoes don’t care all that much about how humans classify them, so say Yellowstone erupted but not to its full potential… the event would still be destructive, but not any more apocalyptic than others like it.

But there is no avoiding the full, heightened and devastating potential that Yellowstone does have. Supervolcanoes are classified by the power of their past eruptions. So, for any volcano to count as “super”, it has to have had a “super-eruption” in its past, which is an eruption at “8 or higher” on the scale we use to measure these disasters; the Volcanic Explosivity Index. More specifically, though, a verified supervolcano has to have an eruption deposit larger than 240 cubic miles. And, because there’s no category higher than “super”, this means that the deposit is effectively limitless - ranging from 240 up to 1,000 cubic miles or more.

The reason these eruptions are so large is that they occur when vast, underground chambers fill with so much magma they burst. In super-eruptions, the volume of magma is so great that an enormous depression forms in the ground when the chamber collapses; called a caldera. Yellowstone National Park is situated inside of three volcanic calderas - from its three previous eruptions - so it really is a hot spot for this type of thing! Interestingly, though, Yellowstone’s previous explosions aren’t thought to be the largest the world has ever seen, and any of our planet’s other supervolcanoes have the potential for huge destruction, too. Yellowstone is simply the most notorious. So, since we can’t stop it from one day erupting, what exactly will happen if – or when – it does?

For starters, the activity we most associate with volcanoes – deadly, flowing lava – wouldn’t be the most pressing problem, unless you were right at the centre. Lava flows would be relatively small, slow and easily contained within the park, so you wouldn’t have to worry about getting covered in molten rock. In fact, if you were that close, you may have already been killed by the initial blast of the eruption itself, which some speculate would be as powerful as an 875,000 megaton explosion going off in the heart of the Midwest.

Ash, on the other hand, is a totally different story. The biggest danger Yellowstone poses is an enormous pyroclastic flow, which is a giant and fast-moving cloud of toxic gas and volcanic matter. It’s this that will start to spread ash across the US, with the effects potentially worsened and quickened depending on wind speed at the time. It’s commonly said that a supervolcanic eruption could produce enough ash to block out the sun, plunging us into a volcanic winter and another ice age. And there is some evidence to this effect… It’s theorised that the eruption of Lake Toba 74,000 years ago, for example, may have itself triggered a millennia of global cooling; so something similar definitely isn’t out of the question for Yellowstone.

If the initially-less-concerning lava causes forest fires in the park, this would further increase the output of ash, so much so that it’s thought that 500 square miles around the volcano itself would be quickly destroyed - choked and smothered by the cloud. On a wider scale, it’s predicted that every single mainland US state as well as parts of southern Canada and northern Mexico would experience at least some of the debris. And even thousands of miles out, this ash is so much more than just an eyesore! It could render huge regions of North America unsuitable for farming and agriculture, sparking famines and polluting much of an entire continent’s worth of water supply. And, since the United States is the world’s largest economy, it’s a disaster which would have ramifications for the entire world, even places that wouldn’t see any of the volcanic ash and gas.

In terms of loss of life, a Yellowstone eruption would inevitably cause some extinctions; with endemic species in the surrounding area wiped out. And, depending on exactly how far and how quickly the ash cloud travels, toxic debris could even reach the Earth’s oceans. The human race as a whole would survive, but North America would suffer an untold list of casualties, as well as massive upheaval and displacement. To a certain extent, though, there might be opportunity to plan for the disaster. One positive note is that volcanoes don’t usually just erupt out of nowhere, especially not the most destructive ones. There are plenty of signs that geologists look for when they’re trying to predict whether one’s liable to blow; including seismic disturbances, an increase in sulphur dioxide released from the ground, and even a change in the behaviour of nearby animals. Molten rock flows below the surface are difficult to measure, but they’re also the best indicator of a magma chamber slowly filling up. The problem here, though, is that notable change can happen weeks or months before an eruption, but sometimes it’s years or even decades. Where volcanos are concerned there is always a degree of uncertainty, but there is usually at least a little time to prepare.

As such, when the Yellowstone question truly becomes a matter of “when?” and not “if?”, we should see widespread countermeasures put in place - to try to at least limit the damage. Evacuation plans and drills within 500 miles of the park; huge stockpiles of food and water across the continent; emergency housing built along the coasts, as far away from the imminent eruption and ash cloud as possible - they’d all need to be considered. Yellowstone would likely become a complex diplomatic issue, too, as refugees from the worst-affected countries look to the international community for help. Meanwhile, some living further afield might rely on underground bunkers to keep them safe… in which case the authorities would need to register (and probably approve) all of them, so that they’d be able to relocate everyone once the worst of the disaster had passed. Given enough time, we could even try to save the endemic and local plants and wildlife at risk, putting animals in conservation-oriented zoos, and plants in structures like the Svalbard Global Seed Vault.

Quite what the world would look like once the dust had settled, though, is difficult to imagine. Underground bunkers, temporary housing and evacuation drills could save us from the immediate effects, but the recovery period would be long and gruelling - with whole regions covered in layers of ash potentially meters thick (depending upon how close to the volcano you get). The prospects of growing anything in the near-future would be low, but even in the far-future a super-eruption could change and disrupt soil types and farming practices for generations. Volcanoes are a natural feature of the environment, however, and are actually integral to many ecosystems… so, should Yellowstone erupt, it really wouldn’t trigger total Armageddon. The planet itself would definitely recover from such an event – like it has recovered from all the super-eruptions of the past.

There’s no denying that a worst-case-scenario, full potential Yellowstone eruption would have a massive effect on life on Earth. But it wouldn’t be the first time that humanity had faced a disaster on this scale. The Toba catastrophe 74,000 years ago may have even been bigger than Yellowstone, and the human race survived that even without a lot of the prior knowledge that we now have.

It would be devastating and dangerous; it’d create all new landscapes across an entire continent; it could trigger wide-reaching problems with the global economy; and Yellowstone National Park itself would never look the same again… but humanity has survived super-eruptions in its past, and more than likely would do once more. And that’s what would happen if the Yellowstone supervolcano erupts.