Every person who is moderately interested in dinosaurs knows the theory that they were wiped out some 66 million years ago when an asteroid or comet struck Earth, causing the most famous mass extinction event in history. What many people do not realise is that moment was not the most devastating mass extinction event to hit the planet, far from it actually. During the Late Ordivician Period 450 million years ago , volcanic activity drove the second-worst mass extinction event in Earth’s history, killing 50 to 60 per cent of life and, most crucially at that time, 85 per cent of marine life . A massive layer of volcanic ash blanketed the world’s seabeds, dwindling oxygen levels, cooling the global temperatures and, in many places, resulting in the environment icing over. “[The extinction event] affected organisms across the whole range of environments, and so cannot be attached to the wiping out of a specific group of animals, unlike the case of the dinosaurs. It profoundly impacted evolution and development of life on earth,” said Jack Longman, a scientist at Carl von Ossietzky University of Oldenburg in Germany. Longman was a lead author on a new study published on December 2 in Nature Geoscience , which pinpointed two moments of peak volcanic activity that might have contributed to this extinction environment; one in what is now North America and the other in modern southern China. The volcanic activity was unrecognisable to what we experience today and far more devastating than anything in our contemporary imagination. For example, Longman pointed to the Diecke bentonite , an eruption that spewed ash across an area of 600,000 sq km (230,000 square miles), or about the size of Norway and Finland combined. “We think during the Late Ordovician there were hundreds of eruptions on the same scale as the Diecke, so we’re talking about lots of ash and lots of enormous eruptions,” said Longman. The eruption of Toba 70,000 years ago, in modern-day Indonesia, was the last time a volcano erupted at the same scale of Diecke, and there is a theory that suggests it almost wiped out the human population. While the impact of the Late Ordovician volcanic activity is clear, it presented the scientists with a problem: the CO2 emissions from the explosions theoretically should have warmed the planet, not cooled it. To answer the question, the scientists turned to a chemical element that is a backbone for life on Earth: phosphorus. When volcanic ash is deposited into the oceans, it goes through a profound chemical change that releases phosphorus and “fertilises the ocean”. Ancient lovers’ ‘embrace’ found in China excites, but the ring intrigues Increased levels of phosphorus increase the viability of organisms that pull CO2 out of the atmosphere, such as algae, helping to lower the Earth’s temperature. Longman explained that “being photosynthetic” these creatures incorporate CO2 into their bodies and, when they die, fall to the seafloor, where the carbon is stored. “We call this the ‘biological pump’, which acts to remove carbon from the atmosphere and transfer it to the deep oceans and sediments,” he said. The scientists theorised that: “[The extinction] events may have been driven by increased delivery of the nutrient phosphorus to the ocean and associated increases in marine productivity.” Furthermore, when dense algae blooms eventually die, they create a depletion of oxygen, called an “oxygen dead zone”, which was another key characteristic of the extinction event that occurred 450 million years ago. By using more recent oceanic sediments that are millions of years old, gathered by specialised sea drilling ships, the team was able to create a model to show how the phosphorus may have impacted the environment in the past. They discovered that the widespread release of ash into the oceans, driven particularly by the two volcanic surges in North America and southern China, would have deposited a sufficient amount of phosphorus to create a knock-on cooling effect, glaciating the environment and creating huge swathes of oxygen dead zones. It would have been sufficient to counterbalance, and even outmatch, the warming effect created by the CO2 released by the volcano explosions. Armoured dinosaur wielded bladed tail resembling Aztec war club “Our models suggest that the deposition of extensive ash blankets and weathering of lavas emplaced during Late Ordovician volcanism supplied sufficient phosphorus to drive global cooling, glaciation and the Late Ordovician mass extinction,” the team wrote in the study. And while Longman would not say it outright, he hinted that this study might provide insight into other extinction events, including the far more famous case that wiped out the dinosaurs 66 million years ago. “I am not saying a comet did not act as the final kill mechanism, but I think these enormous eruptions before must have had a role to play,” he said.