What will happen when the next supervolcano erupts, according to NASA

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NASA has proposed sci-fi plans to potentially shut down a supervolcano — should one show signs of an imminent eruption.

But such a geologic scheme might not ever be necessary. In new research from NASA’s Goddard Institute for Space Studies and Columbia University, scientists found that the most powerful scale of eruption — which emits a mind-boggling amount of material into the atmosphere — would probably not plunge Earth into a deep, cold volcanic winter.

Indeed, the prodigious gasses and ash blasted into the sky by a "super-eruption," which erupts over 240 cubic miles (1,000 cubic kilometers) of magma, would inevitably block some sunlight and have a cooling impact. It just likely wouldn't be devastating to life globally, according to this latest research.

"The relatively modest temperature changes we found most compatible with the evidence could explain why no single super-eruption has produced firm evidence of global-scale catastrophe for humans or ecosystems," Zachary McGraw, the study's lead author and a researcher at NASA GISS and Columbia University, said in a statement. The research was recently published in the peer-reviewed Journal of Climate.

SEE ALSO: Why so many volcanoes seem to be erupting right now

For reference, the infamous 1980 U.S. eruption of Mount St. Helens — which was so potent that it completely blacked out sunlight in Spokane, Washington, located 250 miles away — released 0.67 cubic miles of volcanic rock. While impressive, that's a pittance compared to a super-eruption.

Of course, it's (thankfully) impossible for earth scientists to analyze a recent super-eruption. They are rare. The last such event happened over 22,000 years ago at Taupo in modern-day New Zealand. Yellowstone, in the U.S., is widely known for its super-eruption abilities, too: Some Yellowstone eruptions over the past few million years created layers of volcanic lava rock over 1,300 feet (400 meters) thick.

How a volcano super-eruption will impact Earth

Lacking direct observation of such a blast, scientists use computers to simulate how the mega-event would impact our planet. The key ingredient in prolonged volcanic cooling isn't ash, which is actually tiny fragments of volcanic rock: It's sulfur dioxide gas from volcanoes that condenses into liquid sulfate particles. Once high in the sky in Earth's stratosphere (some six to 30 miles up), sulfur dioxide reacts with atmospheric molecules to produce droplets that can linger for a year or more. And when sunlight hits these droplets, energy is reflected back into space, depriving our planet of substantial amounts of sunlight.

NASA's research simulated how this gas, ejected into the stratosphere during a super-eruption, would impact temperatures on Earth's surface.

A visualization showing the scale of different eruptions. The orange circles show super-eruptions; the Mount St. Helens eruption is a small green circle on the left. Credit: USGS

The two expansive regions within the dotted lines show where ash beds formed from two super-eruptions from the Yellowstone Plateau region over the past few million years. Credit: USGS

Dramatic cooling could devastate crops, plant life, and many ecosystems. Yet the simulations showed that although some cooling would occur, it wouldn't stoke temperature changes much more than the largest eruptions in modern history.

"Generally, you always think about volcanoes cooling. But this study says there's a limit to that," Valentina Aquila, an atmospheric scientist at American University who researches the impacts of volcanism, told Mashable. Aquila had no role in the new super-eruption research.

There's a limit to the cooling because a super-eruption will blast an enormous volume of particles into the atmosphere. But once there, they amass together. Crucially, the larger particles are less efficient at reflecting sunlight compared to smaller particles — because there's less surface area for sunlight to reflect off of, Aquila explained. What's more, the larger droplets fall more quickly from the sky.

But that's not all. The sulfur particles also trap heat radiating off Earth — similar to the greenhouse gasses currently driving climate change. So while some solar radiation is being blocked, radiation emanating from our planet is also being absorbed, which causes a temporary warming effect.

"You get these two counteracting effects," McGraw told Mashable.

In 1991, the dramatic Mount Pinatubo eruption (not nearly a super-eruption) ejected some 15 million tons of sulfur dioxide into the stratosphere, driving global temperatures down by around half a degree Fahrenheit (some 0.3 degrees Celsius) for two years. This research suggests that an eruption hundreds of times bigger may temporarily cause some 2.7 degrees Fahrenheit (1.5 degrees Celsius) of cooling.

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Of course, the impacts of a super-eruption would still be devastating regionally. "A super-eruption would cause massive problems near the eruption site," McGraw said.

Around Yellowstone, parts of Montana, Wyoming, and Idaho would get pummeled with extremely hot flows of rock, ash, and gas, called pyroclastic flows, the U.S Geologic survey explained. Mass evacuations would be needed to avoid massive casualties. Closer to the eruption, day would turn to night. Ashfall would spread over a huge swathe of the U.S.

"A super-eruption would cause massive problems near the eruption site."

But humanity would not be imperiled.

"We can be confident of this because there have been two massive explosions while humans were present on Earth, and both of these were actually larger than Yellowstone's most recent cataclysmic eruption," the Geologic Survey said. "These eruptions were from Toba, Indonesia, about 74,000 years ago and from Taupo, New Zealand, about 26,500 years ago."

Volcanologists don't see any imminent super-eruptions on the horizon. But, thankfully, the volcanoes will show signs well before the event. We'll have plenty of warning.

This story has been updated with more information about super-eruptions.

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