Lying beneath the tranquil settings of Yellowstone National Park in the US lies an enormous magma chamber. It’s responsible for the geysers and hot springs that define the area, but for scientists at Nasa, it’s also one of the greatest natural threats to human civilisation as we know it: a potential supervolcano.

Following an article we published about supervolcanoes last month, a group of Nasa researchers got in touch to share a report previously unseen outside the space agency about the threat – and what could be done about it.

“I was a member of the Nasa Advisory Council on Planetary Defense which studied ways for Nasa to defend the planet from asteroids and comets,” explains Brian Wilcox of Nasa’s Jet Propulsion Laboratory (JPL) at the California Institute of Technology. “I came to the conclusion during that study that the supervolcano threat is substantially greater than the asteroid or comet threat.”

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There are around 20 known supervolcanoes on Earth, with major eruptions occurring on average once every 100,000 years. One of the greatest threats an eruption may pose is thought to be starvation, with a prolonged volcanic winter potentially prohibiting civilisation from having enough food for the current population. In 2012, the United Nations estimated that food reserves worldwide would last 74 days.

When Nasa scientists came to consider the problem, they found that the most logical solution could simply be to cool a supervolcano down. A volcano the size of Yellowstone is essentially a gigantic heat generator, equivalent to six industrial power plants. Yellowstone currently leaks about 60-70% of the heat coming up from below into the atmosphere, via water which seeps into the magma chamber through cracks. The remainder builds up inside the magma, enabling it to dissolve more and more volatile gases and surrounding rocks. Once this heat reaches a certain threshold, then an explosive eruption is inevitable.

I came to the conclusion that the supervolcano threat is substantially greater than the asteroid or comet threat – Brian Wilcox, Nasa

But if more of the heat could be extracted, then the supervolcano would never erupt. Nasa estimates that if a 35% increase in heat transfer could be achieved from its magma chamber, Yellowstone would no longer pose a threat. The only question is how?

One possibility is to simply increase the amount of water in the supervolcano. But from a practical perspective, it would likely be impossible to convince politicians to sanction such an initiative.

“Building a big aqueduct uphill into a mountainous region would be both costly and difficult, and people don’t want their water spent that way,” Wilcox says. “People are desperate for water all over the world and so a major infrastructure project, where the only way the water is used is to cool down a supervolcano, would be very controversial.”

Instead Nasa have conceived a very different plan. They believe the most viable solution could be to drill up to 10km down into the supervolcano, and pump down water at high pressure. The circulating water would return at a temperature of around 350C (662F), thus slowly day by day extracting heat from the volcano. And while such a project would come at an estimated cost of around $3.46bn (£2.69bn), it comes with an enticing catch which could convince politicians to make the investment.

“Yellowstone currently leaks around 6GW in heat,” Wilcox says. “Through drilling in this way, it could be used to create a geothermal plant, which generates electric power at extremely competitive prices of around $0.10/kWh. You would have to give the geothermal companies incentives to drill somewhat deeper and use hotter water than they usually would, but you would pay back your initial investment, and get electricity which can power the surrounding area for a period of potentially tens of thousands of years. And the long-term benefit is that you prevent a future supervolcano eruption which would devastate humanity.”

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But drilling into a supervolcano does not come without certain risks. Namely triggering the eruption you’re intending to prevent.

“The most important thing with this is to do no harm,” Wilcox says. “If you drill into the top of the magma chamber and try and cool it from there, this would be very risky. This could make the cap over the magma chamber more brittle and prone to fracture. And you might trigger the release of harmful volatile gases in the magma at the top of the chamber which would otherwise not be released.”

Instead, the idea is to drill in from the supervolcano from the lower sides, starting outside the boundaries of Yellowstone National Park, and extracting the heat from the underside of the magma chamber. “This way you’re preventing the heat coming up from below from ever reaching the top of the chamber which is where the real threat arises,” Wilcox says.

Those who instigate the project will never see it to completion, or even have an idea whether it might be successful

However those who instigate such a project will never see it to completion, or even have an idea whether it might be successful within their lifetime. Cooling Yellowstone in this manner would happen at a rate of one metre a year, taking of the order of tens of thousands of years until just cold rock was left. Although Yellowstone’s magma chamber would not need to be frozen solid to reach the point where it no longer posed a threat, there would be no guarantee that the endeavour would ultimately be successful for at least hundreds and possibly thousands of years.  

But to prevent a catastrophe, such long-term thinking and planning may be the only choice. “With a project like this, you’d start the process and the main ongoing benefit you’d see in everyday terms is this new supply of electrical power,” Wilcox says.

Such a plan could be potentially applied to every active supervolcano on the planet, and Nasa’s scientists are hoping that their blueprints will encourage more practical scientific discussion and debate for tackling the threat.

“When people first considered the idea of defending the Earth from an asteroid impact, they reacted in a similar way to the supervolcano threat,” Wilcox says. “People thought, ‘As puny as we are, how can humans possibly prevent an asteroid from hitting the Earth.’ Well, it turns out if you engineer something which pushes very slightly for a very long time, you can make the asteroid miss the Earth. So the problem turns out to be easier than people think. In both cases it requires the scientific community to invest brain power and you have to start early. But Yellowstone explodes roughly every 600,000 years, and it is about 600,000 years since it last exploded, which should cause us to sit up and take notice.” 

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