The so-called Permian extinction or Great Dying was the biggest cataclysm to affect life on our 4.5 billion-year-old Earth. In total, there have been five major extinction events in the last 450 to 600 million years, including an asteroid strike 66 million years ago. But the Permian event takes the crown and until recently it was unclear what has caused the mass extinction.
The extinction occurred about 250 million years ago, at the end of the Permian period.
Scientists have proposed multiple scenarios: volcanic eruptions, asteroid strikes or climate change.
One theory, in particular, proposed an eruption of the Siberian Traps – a volcanic region in northern Russia – was responsible for disrupting the planet’s climate.
Researchers from Japan, the US and China now believe the mass extinction was driven by volcanic activity and climate change after all.
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The researchers presented their findings in the peer-reviewed journal Geology.
The study focused on two specific eruption events: one that has so far eluded scientists, and one responsible for killing swathes of marine and land life.
According to lead researcher Kunio Kaiho, professor emeritus at Tohoku University in Japan, the study investigated rock samples from southern China and Italy.
They researchers analysed organic compounds and mercury contained in the samples, and found the rocks were marked by two coronene-mercury enrichments.
These chemical compounds have been linked to an initial ecological disturbance and the following mass extinction.
Professor Kaiho said: “We believe this to be the product of large volcanic eruptions because the coronene anomaly was formed by abnormally high-temperature combustion.
“High-temperature magma or asteroid/comet impacts can make such coronene enrichment.”
Coronene is a condensed polycyclic aromatic hydrocarbon (PAH), which requires higher energy to transform when compared to other PAHs.
This suggests high-temperature volcanism was responsible for the enrichment of hydrocarbons in sedimentary rocks.
The research, led by Dr Hana Jurikova from the GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, found volcanic eruptions filled the skies with large amounts of carbon dioxide, triggering extreme global warming and the acidification of the oceans.
Dr Jurikova said: “We are dealing with a cascading catastrophe in which the rise of carbon dioxide in the atmosphere set off a chain of events that successively extinguished almost all life in the seas.
“Ancient volcanic eruptions of this kind are not directly comparable to anthropogenic carbon emissions, and in fact all modern fossil fuel reserves are far too insufficient to release as much carbon dioxide over hundreds of years, let alone thousands of years as was released 252 million years ago.
“But it is astonishing that humanity’s carbon dioxide emission rate is currently 14 times higher than the annual emission rate at the time that marked the greatest biological catastrophe in Earth’s history.”