Mass extinction 450 million years ago 'triggered by volcanic eruptions and global warming'

The Late Ordovician event killed around 85 per cent of all marine species

Peter Stubley
Saturday 20 June 2020 16:52 BST
World facing first mass extinction since the dinosaurs

Earth’s first major mass extinction could have been triggered by climate change caused by volcanic eruptions, according to a new study.

Scientists have previously believed the Late Ordovician event some 450 million years ago was linked to the end of an ice age, resulting in rising sea levels and plummeting oxygen levels in the oceans.

Around 85 per cent of all marine-based species died out – at a time when most of our present day continents formed a single land mass, Pangaea.

However new research suggests volcanic eruptions released enough carbon dioxide to heat up the planet and deoxygenate the oceans, resulting in the asphyxiation of the species that lived there.

Professor David Bond from the University of Hull, one of the lead researchers, compared the process to the fizziness of a bottle of cola.

“If it’s been in the fridge, it stays nice and fizzy because the gas in that carbon dioxide stays in the liquid,” he told the New York Times.

“But if you leave it on a sunny table outside and it gets really warm, then that gas quickly dissociates out of that liquid and you end up with a flat coke.”

Professor Bond and Dr Stephen Grasby from the Geological Survey of Canada found that when Ordovician rocks collected from a small stream in southern Scotland were heated, they released large amounts of mercury – a sign volcanic eruptions took place during that period.

The rocks also emitted molybdenum and uranium, suggesting the oceans were starved of oxygen at the same time.

The new research, published in the journal Geology, does not discount glaciation at the time but suggests the cooler climate was then impacted by global warming events triggered by volcanic eruptions.

It follows a study published earlier this year which found the Late Ordovician mass extinction was linked to a severe lack of oxygen in the oceans lasting more than three million years.

The most famous mass extinction is the Cretaceous-Paleogene event that wiped out all non-avian dinosaurs some 65 million years ago.

Additional reporting by Press Association

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