Nasa believes the Yellowstone super volcano is a greater threat to life on Earth than any asteroid. So it has come up with a plan to defuse its explosive potential.
Yellowstone National Park is the pride of the United States. It’s an untouched wilderness. It’s overflowing with scenic landscapes. And its colourful hot pools and geysers attract tens of thousands of visitors every year.
But underneath this beautiful – but thin – skin is a lurking monster.
An enormous pool of magma sits high in the Earth’s crust. It’s been calculated to contain about 250 billion cubic kilometres of molten rock.
“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,” Brian Wilcox of Nasa’s Jet Propulsion Laboratory (JPL) told the BBC.
“I came to the conclusion during that study that the super volcano threat is substantially greater than the asteroid or comet threat.”
There are about 20 known super volcanoes on Earth, Nasa says. A major eruption occurs about once every 100,000 years. And these odds are much higher than a repeat of an Earth-changing comet impact of the type that wiped out the dinosaurs.
So Nasa tasked a team with figuring out how to prevent an eruption.
A super volcano is very different from the common conception of tall cones of rock and ash that occasionally catastrophically erupt.
Instead, it’s a vast space of collapsed crust that can cover hundreds of square kilometres. And if it were to erupt, it would not be with a bang.
Instead, vast quantities of searing magma and clouds of fumes would slowly crawl across the landscape – burying much of the United States under a thick coat of ash and lava.
In the case of Yellowstone, it’s enough to change the climate of the world for several centuries.
It’s happened before.
Soil samples have uncovered lava flows hundreds of kilometres long – and kilometres thick – from past eruptions. And the ash falls were even more immense.
A much smaller event in Indonesia, about 75,000 years ago, named the Toba catastrophe, pumped some 4000 tons of hydrogen sulphide gas into the atmosphere along with about 2800 cubic kilometres of ejecta. This produced a global volcanic winter that lasted a decade.
Yellowstone isn’t expected to erupt any time soon. It appears to burst roughly once every 700,000 years. The most recent was 640,000 years ago, with other events 1.3 million years ago and 2.1 million years ago.
This is much more regular than cataclysmic comet impacts.
“When people first considered the idea of defending the Earth from an asteroid impact, they reacted in a similar way to the super volcano threat,” Wilcox said.
“People thought, ‘As puny as we are, how can humans possibly prevent an asteroid from hitting the Earth’.”
Nasa, however, has an idea.
Letting off steam
Nasa’s researchers have told the BBC they have explored what it would take to avert a super volcano catastrophe.
The answer: find a way to cool the magma down.
Super volcanos only spill over when the molten rock is hot enough to become highly fluid.
In a slightly cooler state, it gets thicker. Stickier.
It’s not going anywhere fast.
To achieve this, the Jet Propulsion Labs team calculated a super volcano on the brink of eruption would have to be cooled some 35 per cent.
They propose to do this by pricking the supervolcano’s surface, to let off steam.
But this in itself poses risks.
Drill too deep, and the vent could cause an explosive depressurisation that may set off the exact kind of eruption the scientists were trying to avoid.
Instead, the Nasa scientists propose a 10km deep hole into the hydrothermal water below and to the sides of the magma chamber. These fluids, which form Yellowstone’s famous heat pools and geysers, already drain some 60-70 per cent of the heat from the magma chamber below.
Nasa proposes that, in an emergency, this enormous body of heated water can be injected with cooler water, extracting yet more heat.
This could prevent the super volcano’s magma from reaching the temperature at which it would erupt.
Such a project could cost in excess of US$3.5 billion. But it’s nothing like the reconstruction cost of digging two thirds of the continental United States out from under mountains of volcanic ash.
And it could even help pay for itself.
Steam from the superheated water could be used to drive power turbines.
“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,” Nasa’s Brian Wilcox says.