What would happen if all the world’s volcanoes went off at once? Although this is fairly unlikely to occur, it is a rather glorious thought experiment – and thought experiments are the cornerstone of the scientific process, after all.
Jessica Ball, a geophysicist and volcanologist with the United States Geological Survey (USGS), clearly relished ruminating on a volcanically-induced end-of-the-world scenario. Just recently, she spoke to Flash Forward about how she envisions a supervolcanic oblivion would come to pass, highlighting that some volcanoes would be far more dangerous than others, and in any case, the world’s climate would be changed, perhaps irreparably. It's possible, though, things would be even grimmer than this particular volcanologist is willing to suggest.
Oozes and Ash Clouds
Don't touch that. It's pretty hot. Fotos593/Shutterstock
Initially, there would be mass panic at seeing every single volcano blow its top. Volcanoes known for their slower, calmer eruptions – like Hawaii’s Kilauea or Ethiopia's Erta Ale – would just ooze liquid hot lava all over themselves, which would inconvenience anyone living nearby. However, the lava moves so slowly out of these shield volcanoes that people could run out of the way and hop on a plane.
However, the taller stratovolcanoes like Mount Fuji and fissure eruptions under ice or water, like those seen in Iceland, would cause more of a problem. Both would produce so much ash that it would blanket the sky and darken the world, plunging it initially into a freezing volcanic winter. Without sunlight, crops would fail and agriculture would collapse, along with the higher food chain.
People would starve, and anyone breathing any of that ash in would suffer slow and agonizing respiratory stoppages. Anyone hiding in buildings would be vulnerable to infrastructural collapse: Most ash is five times denser than water, and many structures aren’t designed to hold tonnes of ash falling on top of them.
In terms of the Fujis of the world, the lava and the person-squashing lava bombs would be the least of our worries. Huge, catastrophic pyroclastic flows would barrel down the slopes at supersonic speeds and would almost instantly kill anything and anyone in their path. Anyone trying to escape in a plane would find their engines melting and seizing up, as ash would find its way inside and begin to re-melt into drops of lava.
A Song of Ice and Fire
As Ball rightly points out, the worst part comes from the effect that such huge volcanic eruptions would have on the climate. As aforementioned, the world would be gripped by a volcanic winter, and the concept of “seasons” would disappear, as seen most famously after the 1815 eruption of Tambora. The year after was known in the Northern Hemisphere as the “Year Without Summer.”
Volcanoes have freed the world from the grips of ice ages in the past. In this case, “ice age" refers to one of perhaps five periods in Earth’s history where the world was extremely frigid and where glaciers were extremely widespread. This doesn’t refer to a glacial maximum, where the wobble of the Earth on its rotational axis causes its orbital path to stretch further away from the Sun, enough to encourage glaciers to encroach on lower latitudes.
During periods of continental break-up, where supercontinents like Pangaea or Rodina split apart, volcanism kicks into gear and massive amounts of carbon dioxide are released into the atmosphere. This quickly warms the world, and ice cover dramatically retreats towards the poles.
Although there is some global cooling initially, as huge quantities of sunlight-reflecting sulfur aerosols are released into the sky, the very long-term expulsion of carbon dioxide will overcome this effect – something observed immediately following the end-Permian mass extinction 252 million years ago when over 90 percent of all life on Earth died off. A similar trend was seen at the end-Cretaceous mass extinction 66 million years ago when the non-avian dinosaurs bit the dust.
Volcanic ash would cool the world, but over the long run, the carbon dioxide would warm it. Ammit Jack/Shutterstock
If all the volcanoes in the world were to erupt at once, this is almost certainly what would happen in the long run, but to a far more severe degree than life on Earth had ever previously experienced. Not only that, but huge unstable reservoirs of carbon in the world's oceans and Arctic would thaw out, be turned by microbes into carbon dioxide and methane – a more potent but shorter-lasting greenhouse gas – and would be unleashed into the sky.
This would accelerate planetary warming, ultimately encouraging more trapped icy methane reserves to escape into the atmosphere in a potentially deadly cycle. Warmer oceans also hold less carbon dioxide, so much of this would also effuse skywards.
A Wonky Post-Apocalyptic World
All in all, we might find our planet going through an inexorable, unstoppable global warming cycle. If it warms to the point wherein plants and trees die off, then a huge sink for any carbon dioxide would die off with them. If the warming reached a point wherein all the water on Earth boiled away, then there would also be no oceanic sink for the atmospheric blanket of carbon dioxide.
In the end, we may come to look like Venus, whose atmosphere is suffocatingly rich in carbon dioxide, and whose surface is absent of any liquid water. That, as you can imagine, would not be ideal – but the doom and gloom might not even end there.
About 3.5 billion years ago, Mars experienced such a prolonged volcanic eruption that it gouged out its own mantle, the partly-molten layer beneath the crust, and plonked it on the surface. This major mass imbalance caused the entire Red Planet to tip over by 20°, irrevocably changing its orbital parameters. This would be like Paris suddenly moving to the North Pole.
In this scenario, Earth may become Venus. Ksanawo/Shutterstock
If every single volcano on Earth erupted, but most of the magma erupted out onto the surface at, say, the locations of the hotspot volcanoes, including at Hawaii and Yellowstone, then the Earth may also tip over to some extent.
At the conclusion of this dark and destructive tale of paroxysmal fire, we’d be left with a suffocating, lifeless, scorched, desolate, wonky planet. It won’t happen – don’t start planning to move planets – but it’s almost certain that someday it will form the basis of a plot for a really, really bad film.