by The link between ancient volcanic eruptions and the most severe extinction event the world has ever seen has grown even stronger. A new analysis of Mercury isotopes provided evidence that a quarter of a billion years ago, remote places in the Earth’s southern hemisphere were covered with debris from volcanic eruptions in Siberia.
The so-called Great Dying, also known as the Permian-Triassic mass extinction event, followed, where most life was wiped out under an ash-filled sky.
While it’s clear how things ended – with the loss of over 90% of marine species and over 70% of terrestrial vertebrates – our understanding of how the greatest mortality event on Earth unfolded unfolded remains somewhat cloudy, despite the best efforts of geologists.
By piecing together chemical traces trapped in rocks and ocean sediments, geoscientists are pretty confident that a series of volcanic eruptions set off a cascade of dramatic changes in Earth’s atmosphere and oceans that eventually suffocated the animals. .
But an extinction event as large as the Great Dying also needs a pretty solid case before geoscientists can say definitively what caused it and when it happened. They’re squinting back in time, some 252 million years, after all.
In previous research, zinc and nickel have been used to link changes in ocean chemistry to massive volcanism and loss of marine life. But these elements are recycled on the surface of the Earth, unlike the isotopes of Mercury which provide a much more stable signal of volcanic activity.
Additionally, many studies of this mass extinction event have focused on sites in the northern hemisphere, making it difficult to understand the impact of volcanism on the Earth’s underside. This is important because growing evidence suggests that the Great Death was not a single fatal event, but multiple extinction episodes that occurred in waves over a hundred thousand years.
Thus, the paleoclimatologist Jun Shen of the University of Geosciences of China and his colleagues set out to detect Mercury isotopes in rock deposits at two sites in the southern hemisphere: the Karoo Basin in south-central Africa and the Sydney Basin on the east coast of Australia.
At the time of the Great Death, the basins were united into a supercontinent called Pangea, but are now separated by approximately 10,000 kilometers (6,200 miles) and the Indian Ocean. In them, the researchers found almost identical patterns: Mercury isotopes peaked near the end of the Permian.
This evidence – from what are the furthest land sites of the Siberian Traps to date, the gigantic lava flows formed by the late-epoch volcanoes in question – suggests Mercury was expelled from volcanoes in the northern hemisphere and swept across the globe, researchers say.
“It turns out that volcanic emissions from Mercury have a very specific isotopic composition of the Mercury that has accumulated on the horizon of extinction,” says Tracy Frank, study author and University of Connecticut geologist.
“Knowing the age of these deposits, we can more definitively link the timing of the extinction to this massive eruption in Siberia.”
Their work aligns with sulfur isotope signals coinciding with the Great Death, and also builds on previous research that suggests mass extinctions began occurring on earth up to 600,000 years before life. marine takes its last breaths.
“This suggests that the event itself was not just a blow that happened instantly,” said Christopher Fielding, another geologist from the University of Connecticut.
“It wasn’t just a really bad day on Earth, so to speak, it took a while to build up and that does feed into the new findings nicely because it suggests volcanism was the root cause.”
Researchers acknowledge that it is not easy to determine the direct cause of the great death. Ash plumes from volcanic eruptions in southern China were also implicated in the carnage, in addition to Siberian booby traps.
So try as we might reconstruct the sequence of events that led to Earth’s greatest extinction event, perhaps a more salient message to absorb is the fragility of life on a violent planet that is today today under the pressure of many of the same climate changes: rising temperatures and greenhouse gases.
The research has been published in Communication Nature.
