As Gondwana tore itself apart 165 million years ago,
the rifting unleashed a series of eruptions the likes of which we hope
will never be seen again
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, 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 (Earth-Science 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.
“The ash and aerosols would darken Gondwana’s skies for years to come”
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.
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