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The largest volcanic eruption in Earth's history
55 million
Warm Artic ocean
constantly on the move and most geologists think the continents repeatedly coalesce and split apart in a 500-million-year cycle, so there may have been many more before Rodinia. And the cycle continues: in about 250 million years the world’s land masses will come together again in a future supercontinent called Pangaea Ultima. If only our time machine went forward… Joshua Howgego
The largest volcanic eruption in Earth’s history Gondwana, 135 million years ago Welcome to hell on Earth, aka the ParanáEtendeka province, circa 135 million years ago. The time-travel tourist slogan? “If the dinosaurs don’t get you, the volcanism will!” By the time you arrive, the southern remnant of Pangaea, Gondwana, has already spent millions of years pulling itself apart, separating what we now know as South America from Africa. This rifting was one of the factors that created the red-hot cataclysm you’ve come to see. As the rift worked its way north, Earth’s crust became thinner. Meanwhile, a superheated portion of the mantle was welling up, heating the crust from below. Eventually, magma broke through and flooded across the landscape. The modern-day remnant of this is called the Paraná-Etendeka traps, expanses of basalt covering more than 1.3 million square kilometres of Brazil, Uruguay, Paraguay, Argentina, Namibia and Angola. For the most part, this would be like the volcanism that gave us Iceland – passive,
EPOCH
gentle and only rarely explosive. You didn’t come here for gentle, though. Happily for thrill seekers, a lot of the magma is rich in silica. “That’s the key to explosive eruptions,” says Sarah Dodd of Imperial College London. “Silicic magma is highly viscous and so it traps volcanic gases. These build up, and ultimately propel magma explosively towards the surface.” The Volcanic Explosivity Index gives you an idea of what’s in store: the eruption you’re here to see has the maximum ranking of 8, which is described as “apocalyptic” (one ranking above “mega-colossal”). This score is given to any event that ejects more than 1000 cubic kilometres of rock, as the supervolcano Toba did in Indonesia 74,000 years ago, much to fledgling humanity’s inconvenience. The PE traps produced at least nine apocalyptic eruptions, probably over several million years. They are the most violent eruptions in Earth’s history, as far as we know. But we’re gonna need a bigger scale, because the largest of them spewed at least 8600 cubic kilometres of rock – based on what we can see in South America and Africa today – and perhaps as much as 26,000 cubic kilometres if you factor in far-flung ash and gases (EarthScience Reviews, vol 102, p 207). That’s enough material to cover the entire UK to a depth of 100 metres. And hopefully you brought provisions, because this eruption will take several months. An event on this scale will incinerate, smother or choke everything for hundreds of kilometres in every direction. Lava from one eruption travelled 650 kilometres. So in modern terms, if it happened in the Highlands of Scotland you would want to park your time machine no closer than London. From that distance you would see the black clouds mushrooming, as an almost inconceivable volume of ash is lofted by explosive force and heat into the upper atmosphere, darkening Gondwana’s skies for years to come. “This ash, combined with
sulphate aerosols also produced by the eruption, will reflect solar radiation, quickly plunging the world into a volcanic winter for years after,” says Dodd. For comparison, the much smaller Toba eruption was estimated to cause about 10 degrees of global cooling in the year immediately following, with temperatures not recovering for over a decade. If you stay to watch the immediate aftermath, you will see the local vegetation coated in ash and ravaged by acid rain. This large-scale destruction of plant life will take with it the entire regional food chain, wiping out numerous dinosaurs. The sulphate aerosols are relatively short-lived though, and the ash would eventually settle. So after a few years of cooling, the colossal amount of carbon dioxide also pumped out by the eruption will bring a much longer period of global warming. That aspect, at least, is one you don’t need a time machine to experience. Sean O’Neill
Super-greenhouse The Arctic, 55 million years ago Pack your cozzie, we’re going to the Arctic. It’s going to be hot and steamy. There will be palm trees and crocodiles. This is the Paleocene-Eocene thermal maximum, or PETM, of 55 million years ago. For the past few million years, Earth has gradually been getting hotter and hotter and is now on the verge of a planetary heatwave the likes of which have rarely been seen. Even before the mercury peaks, it’s pretty toasty. The poles are essentially ice-free, the deepest reaches of the oceans are 8 ˚C warmer than today, sea levels are roughly 70 metres higher and there are crocodile-like >
66 million
55 million Paleocene
Warm Arctic ocean
Eocene
Paleogene
Cenozoic
18 July 2015 | NewScientist | 33
Warm Artic ocean
constantly on the move and most geologists think the continents repeatedly coalesce and split apart in a 500-million-year cycle, so there may have been many more before Rodinia. And the cycle continues: in about 250 million years the world’s land masses will come together again in a future supercontinent called Pangaea Ultima. If only our time machine went forward… Joshua Howgego
The largest volcanic eruption in Earth’s history Gondwana, 135 million years ago Welcome to hell on Earth, aka the ParanáEtendeka province, circa 135 million years ago. The time-travel tourist slogan? “If the dinosaurs don’t get you, the volcanism will!” By the time you arrive, the southern remnant of Pangaea, Gondwana, has already spent millions of years pulling itself apart, separating what we now know as South America from Africa. This rifting was one of the factors that created the red-hot cataclysm you’ve come to see. As the rift worked its way north, Earth’s crust became thinner. Meanwhile, a superheated portion of the mantle was welling up, heating the crust from below. Eventually, magma broke through and flooded across the landscape. The modern-day remnant of this is called the Paraná-Etendeka traps, expanses of basalt covering more than 1.3 million square kilometres of Brazil, Uruguay, Paraguay, Argentina, Namibia and Angola. For the most part, this would be like the volcanism that gave us Iceland – passive,
EPOCH
gentle and only rarely explosive. You didn’t come here for gentle, though. Happily for thrill seekers, a lot of the magma is rich in silica. “That’s the key to explosive eruptions,” says Sarah Dodd of Imperial College London. “Silicic magma is highly viscous and so it traps volcanic gases. These build up, and ultimately propel magma explosively towards the surface.” The Volcanic Explosivity Index gives you an idea of what’s in store: the eruption you’re here to see has the maximum ranking of 8, which is described as “apocalyptic” (one ranking above “mega-colossal”). This score is given to any event that ejects more than 1000 cubic kilometres of rock, as the supervolcano Toba did in Indonesia 74,000 years ago, much to fledgling humanity’s inconvenience. The PE traps produced at least nine apocalyptic eruptions, probably over several million years. They are the most violent eruptions in Earth’s history, as far as we know. But we’re gonna need a bigger scale, because the largest of them spewed at least 8600 cubic kilometres of rock – based on what we can see in South America and Africa today – and perhaps as much as 26,000 cubic kilometres if you factor in far-flung ash and gases (EarthScience Reviews, vol 102, p 207). That’s enough material to cover the entire UK to a depth of 100 metres. And hopefully you brought provisions, because this eruption will take several months. An event on this scale will incinerate, smother or choke everything for hundreds of kilometres in every direction. Lava from one eruption travelled 650 kilometres. So in modern terms, if it happened in the Highlands of Scotland you would want to park your time machine no closer than London. From that distance you would see the black clouds mushrooming, as an almost inconceivable volume of ash is lofted by explosive force and heat into the upper atmosphere, darkening Gondwana’s skies for years to come. “This ash, combined with
sulphate aerosols also produced by the eruption, will reflect solar radiation, quickly plunging the world into a volcanic winter for years after,” says Dodd. For comparison, the much smaller Toba eruption was estimated to cause about 10 degrees of global cooling in the year immediately following, with temperatures not recovering for over a decade. If you stay to watch the immediate aftermath, you will see the local vegetation coated in ash and ravaged by acid rain. This large-scale destruction of plant life will take with it the entire regional food chain, wiping out numerous dinosaurs. The sulphate aerosols are relatively short-lived though, and the ash would eventually settle. So after a few years of cooling, the colossal amount of carbon dioxide also pumped out by the eruption will bring a much longer period of global warming. That aspect, at least, is one you don’t need a time machine to experience. Sean O’Neill
Super-greenhouse The Arctic, 55 million years ago Pack your cozzie, we’re going to the Arctic. It’s going to be hot and steamy. There will be palm trees and crocodiles. This is the Paleocene-Eocene thermal maximum, or PETM, of 55 million years ago. For the past few million years, Earth has gradually been getting hotter and hotter and is now on the verge of a planetary heatwave the likes of which have rarely been seen. Even before the mercury peaks, it’s pretty toasty. The poles are essentially ice-free, the deepest reaches of the oceans are 8 ˚C warmer than today, sea levels are roughly 70 metres higher and there are crocodile-like >
66 million
55 million Paleocene
Warm Arctic ocean
Eocene
Paleogene
Cenozoic
18 July 2015 | NewScientist | 33