Late Ordovician period


Mass marine extinction triggered by global warming says University of Hull professor

The mass extinction of around 85 per cent of all marine species on Earth could have been triggered by climate change.

The Late Ordovician extinction, which occurred almost 450 million years ago, has long been a mystery to scientists.

While some have pointed to toxic metals and radiation being released from a distant galaxy, others have previously argued global cooling could be behind the mass extinction.

However, new research led by the University of Hull’s Professor David Bond and Dr Stephen Grasby, from the Geological Survey of Canada, has uncovered a new, more familiar explanation.

The pair have suggested that widespread volcanic eruptions released enough carbon dioxide to heat up the planet, at the same time starving the oceans of oxygen.

If correct, it would bring the event closer in line with many of history’s other mass extinctions, attributed to global warming.

Prof. Bond told the New York Times: “Think 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.

“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.”

Towards the end of the Ordovician period, Earth experienced widespread glaciation.

Experts have preciously said such an event could have caused shallow seas to disappear, impacting on the species which lived there, and subsequently disrupting the food chain.

Some scientists, however, have struggled with this explanation. Glacial events often span millions of years, but evidence showed the mass extinction in the Late Ordovician was an abrupt event.

Dr Grasby, who has been researching the extinction alongside Prof. Bond, said himself: “The Ordovician one has always been a little bit of an oddball.”

The pair’s research has now formed a new publication in leading journal Geology.

Prof. Bond and Dr Grasby reached their volcanic hypothesis after collecting Ordovician rocks from a small stream in southern Scotland.

They then shipped those rocks to Vancouver, British Columbia, where the specimens were heated in a lab until they released large amounts of mercury — a tell-tale sign that volcanoes had rocked the period.

The rocks also emitted molybdenum and uranium, suggesting the oceans were deoxygenated at the time. Prof. Bond and Dr Grasby argued only warming can so easily starve the oceans of oxygen, in turn asphyxiating the species which lived there.

These findings allowed the team to paint a new picture — one that doesn’t discount glaciation at the time, but suggests that the cooler climate was then impacted by global warming events triggered by volcanic eruptions.

If correct, it would bring the Late Ordovician mass extinction closer in line with many of history’s other mass extinctions, which have been linked to climate change global warming.

The findings also bear huge significance today. As scientists around the world continue to warn of the ongoing ‘climate crisis,’ history tells us that global warming can have a devastating impact on species and habitats.

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