By Ian Randall For Mailonline
Published: 14:56 BST, 14 April 2020 | Updated: 14:56 BST, 14 April 2020
More than half of all of Earth's ocean life died off 444 million years ago because of falling oxygen levels, a study has found.
Experts believe that the 'Late Ordovician' mass extinction 450 million years ago was due to widespread 'anoxia', or oxygen depletion, over a three million year period.Insurance Loans Mortgage Attorney Credit Lawyer
The Late Ordovician event was the first of out planet's 'big five' mass extinctions — although some experts believe humanity is presently causing a sixth.
The researchers hope that their findings will help scientists better monitor oxygen in the oceans occurring as a result of modern climate change.
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More than half of all of Earth's ocean life died off 444 million years ago because of falling oxygen levels, a study has found. Pictured, an artist's impression of the cone-like shells of dead Cameroceras shells sticking up out of the muddy foreshore after the extinction event
'Our study has squeezed out a lot of the remaining uncertainty over the extent and intensity of the anoxic conditions during a mass die-off that occurred hundreds of millions of years ago,' said geologist Richard Stockey of Stanford University.
'But the findings are not limited to that one biological cataclysm.'
At the outset of the Late Ordovician event, the world was a very different place than it is today, with the vast majority of life to be found in the oceans, with plants having only just begun to appear on land.
Most of the modern-day continents were jammed together as a single super-continent, which researchers have dubbed Gondwana.
An initial pulse of extinctions began as a result of global cooling, which left Gondwana covered by glaciers around 444 million years ago.Insurance Loans Mortgage Attorney Credit Lawyer
Over the next three million years — a period dubbed the Hirnantian–Rhuddanian boundary — a second pulse of extinction wiped out around 85 per cent of marine species.
Previous studies gleaned valuable information about ancient oxygen levels by looking at changes in radioactive metals caused by different levels of the gas. Using this information and new data from samples of black shale from the Murzuq Basin in Libya, researchers created a new model to map out the oxygen levels in the prehistoric environment.