Forget the mass extinction event that wiped out the landlocked dinosaurs and 75 percent of all life – that was peanuts compared to the apocalypse that visited the world 252 million years ago. Colloquially known as the Great Dying, this wiped out as many as 96 percent of all species.
A little more serious, and the planet would have been sterilized. Everything alive on Earth today descended from that small band of survivors. If there was one event that defined our world more than any other, this was it.
A new study, published in Nature Communications, places the blame squarely on a near-continental-sized volcanic eruption that took place in Siberia all those millions of years ago. Led by the United States Geological Survey (USGS), this new study confirms what scientists have known for some time, but nails down the timing and the specifics a little more.
There's no doubt that the effusive eruption of the Siberian Traps – which created step-like lava flows all across northern Pangaea, the supercontinent that existed at the time – kicked-started the Great Dying. Although it produced a lava flow that lasted for around 1 million years, one which turned that part of the planet into a no-go hellzone, it wasn’t the lava that caused the mass extinction event.
This eruption happened to release a lot of volatile gases too, including 4.4 trillion tonnes of carbon monoxide, 75 trillion tonnes of sulphur dioxide, and 85 trillion tonnes of carbon dioxide.
The first two are great reflectors and deflectors of incoming solar radiation, and as such, they triggered a period of sudden global cooling and dark skies. This caused photosynthesis all over the planet to shut down, which triggered a collapse in food chains – particularly in the oceans.
Then, the carbon dioxide took hold and the planet warmed dramatically, by around 8°C (14.4°F) in a few thousand years – devastating global warming by any measure.
This new research looked at the volcanological deposits left behind by this ocean of fire. It found that the worst part of the mass extinction event, when most species began to die off, coincided with a change in how the lava was being erupted.
Instead of just emerging out of a colossal fissure and pouring over the landscape throughout its million-year-long conquest, the team found that this lava intruded into an area of carbon-rich sediments for 50,000 years. This was likely the reason so much carbon dioxide was produced during the event, which ultimately ended up setting off the worst mass extinction event in the planet’s history.
When this step-change occurred and vast carbon dioxide reserves began to be unleashed, life on land struggled, and the oceans began warming and becoming more acidic.
This ultimately ended up destabilizing stores of frozen methane – a shorter lived, but far more potent greenhouse gas – beneath the sea floor. These effused into the Panthalassic and Tethys oceans, and climate change was exacerbated further.
On Earth, everything that is an equation needs to be balanced. If you heat the oceans, they will try to cool down. Similarly, if you add in all this methane and carbon dioxide, another gas needs to be removed to make room, so to speak. In this case, that gas was oxygen, and chemistry conspired to remove it from all of life’s environments.
From the initial volcanic trigger, life was frozen, burned, overheated, corroded, and suffocated in a climate change nightmare.
People talk about the end of the world like it’s a potential future scenario, but as the geological record shows, it’s not science fiction – it already happened, 252 million years ago.