Scientists have unravelled the cause of the largest mass extinction in the history of Earth – wiping out 90 per cent of all life on the planet around 250 million years ago.
Dubbed the Great Dying, the hugely catastrophic event was triggered by a massive volcanic eruption that ran for almost one million years in what is today Siberia.
Until now, scientists were unsure of how the so-called Flood Basalts eruption was responsible for wiping out such a large proportion of life on Earth, since previous volcanic activity of this scale had not killed anywhere near as many species.
Some had suggested the eruption blanketed the Earth in a dense smog that blocked the sun’s rays from reaching the planet’s surface.
However, a new study has revealed how chemicals released by the eruption released a huge reservoir of deadly chemicals into the air that stripped Earth of its ozone layer.
This eradicated the only protection Earth’s inhabitants had against the sun’s deadly UV rays, causing the death toll to skyrocket, compared to other major eruptions.
Scientists analysed the chemical composition of mantle xenoliths (pictured), rock sections of the lithosphere – a section of the planet located between the crust and the mantle – that get captured by passing magma and erupted to the surface during eruptions
Scientists at the Centre for Petrographic and Geochemical Research in Vandœuvre-lès-Nancy, France, studied rock from Earth’s upper mantle to determine the cause.
They analysed the chemical composition of mantle xenoliths, rock sections of the lithosphere – a section of the planet located between the crust and the mantle – that gets captured by passing magma and erupted to the surface during eruptions.
Through analysis of the ancient samples, researchers attempted to determine the composition of the lithosphere.
They found that before the Flood Basalts took place, the Siberian lithosphere was heavily loaded with chlorine, bromine, and iodine.
These chemicals, all elements from the halogen group, seemed to disappear soon after the devastating volcanic eruption.
‘We concluded that the large reservoir of halogens that was stored in the Siberian lithosphere was sent into the earth’s atmosphere during the volcanic explosion,’ said study lead author Michael Broadley.
The Great Dying was a hugely catastrophic event was triggered by a massive volcanic eruption that ran for almost one million years in what is today Siberia (stock image)
‘This effectively destroyed the ozone layer at the time and contributed to the mass extinction.’
Around 95 per cent of marine life and 70 per cent of life on land was wiped out in ‘The Great Dying’ 252 million years ago.
All life on Earth today is descended from the roughly ten per cent of animals, plants and microbes that survived the mass extinction event.
Previously it was thought the eruption was so deadly because it blanketed the Earth in thick smog that blocked the sun’s rays from reaching the planet’s surface.
‘The scale of this extinction was incredible,’ said Mr Broadley.
‘Scientists have often wondered what made the Siberian Flood Basalts so much more deadly than other similar eruptions.’