When Life on Earth Was Nearly Extinguished

While cautioning that there may have been other killers involved in these Armageddons, as well, the paleontologist David Bond and the geologist Stephen Grasby write in the journal that most mass extinctions were marked by “global warming, anoxia and ocean acidification, driven by changes in atmospheric CO2.” After synthesizing a vast body of literature and reviewing almost 20 global mass extinctions over the past half billion years — including the most extreme ones, the so-called Big Five — the authors concluded that “large scale volcanism is the main driver of mass extinctions” and that “most extinctions are associated with global warming and proximal killers such as marine anoxia.”

The journal’s special issue reflects a research community that, failing to find asteroid impacts at the crime scenes of many of the planet’s worst prehistoric calamities, has turned its attention away from the sky and toward homegrown killers.

Today, in the lonely reaches of Siberia, piles of ancient basalt stack up, in places, miles thick. During the height of the End-Permian mass extinction 252 million years ago, this lava would have covered millions of square miles of what was then the supercontinent Pangaea. But it wasn’t simply the lava that nearly exterminated life on earth.

As the work of Dr. Burgess documents, when this magma started spreading into the shallow crust of Siberia, it intruded into one of the world’s largest coal basins, cooking huge deposits of carbon-rich rocks. The superheated fossil fuels then ruptured at the earth’s surface in spectacular gas explosions, as documented by a team led by the Norwegian geologist Henrik Svensen.

Though volcanoes in Siberia had already been erupting for around 300,000 years, Dr. Burgess’s work indicates that it wasn’t until the magma started burning through fossil fuels on a colossal scale that the mass extinction began. The carbon dioxide was delivered to the atmosphere just as effectively as by any coal-fired power plant or minivan muffler today.

In the resulting chaos, as temperatures rose and life died in the acidifying, oxygen-starved oceans, the planet nearly lost its pulse. I asked Dr. Burgess what a time traveler visiting the End-Permian earth would have experienced. “It would be hot and it would be terrible,” he said, laughing.

Though the asteroid that would wipe out the dinosaurs 186 million years later might get more attention, the Great Dying dwarfs that catastrophe in…

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