The eruptions of so-called supervolcanoes – those that, strictly speaking, produce eruptions that eject at least 1,000 cubic kilometers (240 cubic miles) of material – may rattle the bones. However, they’re not as apocalyptic as they look. If Yellowstone’s supervolcano erupted today, for example, it’d be devastating, but humanity would certainly pull through.
A new Nature study doubles down on this perhaps counterintuitive fact. Looking at the Toba supervolcanic eruption around 74,000 years ago, a team led by Arizona State University (ASU) have concluded that one group of humans was barely left with a scratch despite the cataclysm that took place.
This supereruption, coming in as the most explosive in the last 2 million years, certainly had murderous potential. The blast on Sumatra excavated a crater 100 kilometers (62 miles) across, and generated up to 2,800 cubic kilometers (672 cubic miles) of volcanic debris that was scattered across the planet.
The global effects of this supereruption are heavily debated. It wasn’t long ago that it was thought that the masses of sunlight-reflecting sulfuric acid clumps up on high triggered a volcanic winter so potent and prolonged that it killed off a cornucopia of life. Most dramatically, humanity itself was suspected of being pushed to the brink of extinction.
As such climatic effects are always the most dangerous aspects of significant eruptions, teams across the world have been searching for signs of it in locations across the world. Primarily because the volcanic winter effect can’t be found in plenty of geological deposits, such human extinction ideas have largely fallen out of favor.
This new study took a slightly different approach to such precursors.
“The only way to determine if populations survived Toba is to find the shards directly interstratified with evidence of human behavior,” senior author Professor Curtis Marean, associate director of the Institute of Human Origins at ASU, told IFLScience.
“Our study is the only one to have done that anywhere in the world.”
Looking at South Africa, the team sifted through the ancient sediments and found examples of what they term “cryptotephra” – literally, hidden ash. Found at two archaeological sites of evolutionarily modern humans at Vleesbaai and Pinnacle Point, they assessed their geochemistry and confirmed that they were the product of the 74,000-year-old Toba supereruption.
Glassy products of the supereruption drifted 9,000 kilometers (roughly 5,600 miles) to make it to South Africa. So did the eruption's deadly tendrils reach that far as well?
Apparently not: Archaeological evidence points toward a continued and perhaps increased intensity of human settlement activities in the region. As the team put it in their paper, humans there didn’t just survive, but “thrived through the Toba event”, even as a temporary glacial phase kicked into gear. They posit that a wealth of coastal resources, along with humanity's fledgling ability to adapt to environmental changes, explain this, whatever those environmental changes may have been.
An important caveat is that this new study only illuminates humanity’s response in one small part of the world; future research needs to expand the range of sites analyzed to ensure South Africa wasn’t an exceptional safe haven. It is still possible that humans elsewhere suffered, rather than thrived.
Marean also added that not everyone got off scot-free: those that witnessed it up close probably didn’t fare well. “I think it unlikely people in Sumatra survived… there is no study that has shown they did.”
Regardless, it's important to emphasize that, clearly, humanity survived Toba – and we didn’t have advanced technology 74,000 years ago. This suggests that we shouldn’t be too afraid of the big bad (volcanic) wolf today, in the sense that any future supereruption won’t bring our species crashing down.
That’s not to say that volcanic eruptions can’t bring about mass extinction events, by the way, but in this case, slow and steady wins the race.