Tied to the tracks, we see the train coming. Will we escape our bonds in time? In Hollywood, we will. Basically the alternative doesn’t bear thinking about.
Now a new study published in PNAS sheds light on how past supervolcanic eruptions caused mass extinctions, and why one particular one apparently didn’t: Kerguelen. The implications are horrifying, mainly because the team at Curtin University’s School of Earth and Planetary Sciences in Western Australia, with colleagues, also calculates that humanity is emitting carbon 200 times faster than the rate of the prehistoric super-eruptions that caused mass extinctions.
Mass extinctions resulting from supervolcanic activity were found to be due chiefly to enormous, rapid emissions of carbon dioxide, as opposed to the gentle, glacially slow natural carbon cycle; and opposed to other phenomena related with super-eruptions. Sudden, massive release of CO2 and other greenhouse gases seem to have pushed the global environment beyond a tipping point, acidifying the oceans and lifting temperatures to deadly levels.
“Mass extinction” technically means that at least 75 percent of all species die within a short time, geologically speaking: within a couple to a few million years.
During Earth’s history, we know of five catastrophic mass extinctions, some of which wiped out 90 percent of all species. Separate work has determined that a sixth mass extinction is in process, and for the first time in Earth’s history it is being caused by us, not acts of God. Yet the findings reported by lead researcher Dr. Qiang Jiang and colleagues imply that the worst lies ahead.
The benign supervolcano
The tip-off to the paper by Jiang and colleagues is the Kerguelen plateau, one of the structures by a supervolcano that erupted nonstop for about 32 million years, starting about 122 million years ago and producing a plateau about three times the size of California in area. Once it was a proper micro-continent with forests, but today most of it lies beneath the southern Indian Ocean. Little bits of it peep above the water: the Kerguelen, Heard and McDonald islands.
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Kerguelen is the second-largest igneous province in the world, if we look back at the last half-billion years – which is the period of time in which complex life arose from our primordial ancestors. The Kerguelen supervolcano began to erupt as the supercontinent Gondwana was splitting up about 130 million years ago.
But here is the thing. Separate work has tied mass extinctions to supervolcano eruptions that triggered environmental crises – but not all supervolcanoes had the same geologic triggers, or have the same effect. For instance, the creation of the Siberian Traps large igneous province around a quarter-billion years ago has been associated with the terrible Permian-Triassic extinction event, the worst ever as far as we know, when about 96 percent of sea life and 70 percent of terrestrial life died.
Now, each volcano in the world has its own chemical makeup, which we can analyze. Some have more of this or that element; there is even one volcano in Indonesia that erupts bright blue lava because of high sulfur content.
All volcanoes emitting magma release at least some CO2. But although its magmatic emissions were vast, the newly confirmed dating of the Kerguelen plateau to about 122 million years ago has not been found to be associated with a mass extinction. True, it was associated with an oceanic anoxic event – meaning the seas became oxygen-depleted – but the event was comparatively minor, explains co-researcher Prof. Fred Jourdan of the Western Australian Argon Isotope Facility at Curtin University. Marine animals would not have done particularly well, but a mass extinction there was not, he says.
Why might Kerguelen have been less inimical to life than other super-eruptions? Because it did not involve the rapid emission of large amounts of CO2, explains team member Dr. Hugo Olierook.
“Other deadly supervolcanoes wiped out life primarily through rapid release of enormous volumes of carbon dioxide. Perhaps the Kerguelen eruptions emitted much slower or much less carbon dioxide, or both,” Olierook says. All in all, the team estimates that the amount and rate of CO2 Kerguelen released was around a fifth of other supervolcanoes, and it did so 30 times slower than supervolcano blasts that wiped out almost all life.
But the punch line is that according to the researchers’ calculations, human beings are currently emitting carbon dioxide 200 times faster than those supervolcanic eruptions that caused the most severe mass extinctions, the team warns. That is regarding speed; what about quantity?
We are puny animals. One of the five mass extinctions has been tied to the volcanism creating the Central Atlantic Magmatic Province. In 2020, a paper published in Nature estimated that the creation of CAMP released about 100,000 gigatons of carbon dioxide that could have warmed the planet by 10 to 15 degrees Celsius (18 to 27 degrees Fahrenheit).
We puny animals are approaching an average global increase of 2 degrees Celsius since the late 19th century. That is the train we are driving straight at ourselves tied to the tracks. Here, too, the alternative doesn’t bear thinking about, but we have to.