An ancient underwater event wiped out more than 90% of life – and it wasn’t a tsunami

Around 250 million years ago, a mass extinction event wiped out more than 90% of life – and it all began in the water.

You’re probably thinking it was a tsunami, a devastating natural disaster that can cause huge numbers of people to die.

But this ancient event – known as the Great Dying – was so catastrophic it was more deadly than the asteroid that wiped out the dinosaurs, researchers say.

It’s widely believed the Earth suffered a sudden warning caused by carbon dioxide released by volcanic activity in a region known as the Siberian Traps.

Emissions in the area, which is now Russia and was once the size of Australia, resulted in higher temperatures, acid rain and ocean acidification, causing the ocean to become low in oxygen, killing off marine creatures.

But according to a new research paper, another event could have played a pivotal role.

In their published paper in the journal Science, researchers from the University of Bristol and China University of Geosciences (Wuhan) say that these mega El Niños caused wild swings in the climate, killing off forests and many land animals.

El Niño is widely used to describe the warming of sea surface temperature that occurs every few years, typically concentrated in the central-east equatorial Pacific

Professor Paul Wignall from Leeds’ School of Earth and Environment said: ‘During the Permian-Triassic crisis, El Niño persisted for much longer resulting in a decade of widespread drought, followed by years of flooding. 

‘Basically, the climate was all over the place and that makes it very hard for any species to adapt.’

Co-lead author Dr Alexander Farnsworth, from the University of Bristol, added: ‘Climate warming alone cannot drive such devastating extinctions because, as we are seeing today, when the tropics become too hot, species migrate to the cooler, higher latitudes.

‘Our research has revealed that increased greenhouse gases don’t just make the majority of the planet warmer, they also increase weather and climate variability making it even more “wild” and difficult for life to survive.’

Around 90% of all species alive at the time may have gone extinct during the end-Permian extinction.

Although the volcanic eruptions theory seemed to be a plausible explanation, it did not explain everything.

For example, land species started going extinct tens of thousands of years earlier than those in the sea. 

To explain this, previous researchers have proposed that volcanic winters or the loss of the ozone layer may have caused this event.

Prof Yadong Sun, at the China University of Geosciences, suggested that extreme El Niños may be involved, based on oxygen isotopes in fossils

So, the team ran computer models to explore what might have happened at the end of the Permian era that could explain Dr Sun’s findings.

The researchers found that before the mass extinction began, El Niños were probably of a similar intensity and duration as today. That is, the warm water was about 0.5°C (0.9F) hotter than average and the events lasted for a few months.

But these events in a massive ocean called Panthalassa, which was around 30% wider at the equator.

This means that the area of warm water during El Niños were much larger than today and therefore had a bigger impact. As carbon dioxide (CO2) levels rose at the end of the Permian era, these El Niño events got stronger and lasted longer, the team’s models suggest.

They caused extreme swings in the weather on land that killed off forests, which stopped soaking up CO2 and started releasing it, leading to more warming and even more extreme El Niños.

In the sea, the animals could easily migrate to avoid the warming temperatures, which is why marine extinctions happened later – when global warming became more intense.

Dr Sun said: ‘Most life failed to adapt to these conditions, but thankfully a few things survived, without which we wouldn’t be here today.

‘It was nearly, but not quite, the end of life on Earth.’ 

As El Niños worsened, it took away the carbon sink, meaning anything that absorbs more carbon from the atmosphere than it releases, which led to the death of a lot of marine animals. 

By the peak of the extinction, the temperature during El Niños was up to 4°C (7.2F), with each event lasting more than a decade. 

Dr Farnsworth said: ‘The Permo-Triassic mass extinction, although devastating, would ultimately see the rise of Dinosaurs becoming the dominant species thereafter, as would the Cretaceous mass extinction lead to the rise of mammals, and humans.’