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Were Magma pulses responsible for Earth's most devastating extinction event?

Were Magma pulses responsible ...
Geologists at MIT have found evidence that magma pulses may have been responsible for the worst extinction event in Earth's history
Geologists at MIT have found evidence that magma pulses may have been responsible for the worst extinction event in Earth's history
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Geologists at MIT have found evidence that magma pulses may have been responsible for the worst extinction event in Earth's history
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Geologists at MIT have found evidence that magma pulses may have been responsible for the worst extinction event in Earth's history

A time period doesn't earn the nickname "The Great Dying" for nothing. The mass extinction event that occurred at the end of the Permian period is the worst in Earth's history, wiping out some 70 percent of land animals and a staggering 95 percent of sea life. The exact cause of the event is up for debate, but a huge volcanic region known as the Siberian Traps is a leading candidate. New research out of MIT and the US Geological Survey points the finger squarely at that region – but not in the way previously expected.

Today, the Siberian Traps is made up of about 2 million sq km (770,000 sq mi) of igneous rock, but back in the Permian period the region was an ocean of lava belching up from the depths of the Earth and flowing across the land. These extreme eruptions have long been thought to be a top contender for triggering the end-Permian extinction event, but the pieces don't quite add up.

"One thing really stuck out as a sore thumb to me," says Seth Burgess, first author of the study. "The total duration of magmatism in most cases is about 1 million years, but extinctions happen really quickly, in about 10,000 years. That told me that it's not the entire large igneous province driving extinction."

Burgess believed that there was a more immediate trigger for the extinctions contained inside the larger period of flowing lava. To investigate, the team analyzed samples of ancient rock collected from the Siberian Traps and found that the magmatic period started about 300,000 years before the extinction event, and continued for 500,000 years afterwards.

That seems like a pretty clear smoking gun, but it was still too wide a window to account for the fairly sudden decline in species, and there was no evidence of climate change until the extinctions began, some 252 million years ago. But under the surface are layers called sills, which are narrow channels of rock that form when lava squeezes between existing layers. And coincidentally, these sills started to appear 251.9 million years ago.

"I realized the oldest sills out there correspond, bang-on, with the start of the mass extinction," says Burgess. "You don't have any negative effects occurring in the biosphere when you've got all this lava erupting, but the second you start intruding sills, the mass extinction starts."

Armed with those new observations, the team outlined a new timeline that might have led to the biggest extinction event on Earth. First, 252.2 million years ago, lava erupts and flows across the land for some 300,000 years or so, eventually cooling and forming a solid layer of rock at the surface.

Then, 251.9 million years ago, that solid layer began preventing any more magma from erupting onto the surface. Instead, it was forced out sideways, spreading underneath the rocky cap and forming the sills we see today. In doing so, the researchers say it likely heated up sedimentary layers full of carbon, which in turn belched their greenhouse gases into the atmosphere.

This excess of CO2 in the atmosphere is consistent with other hypotheses about the extinction event. Previous studies have attributed the mass dying to ocean acidification and even microbes that released methane, and while these may have been factors, it's likely that they were themselves symptoms of this magma pulse scenario.

"Large igneous provinces have always been blamed for mass extinctions, but no one has really figured out if they're really guilty, and if so, how it was done," says Burgess. "Our new work takes that next step and identifies which part of the large igneous province is guilty, and how it committed the crime."

The research was published in the journal Nature Communications.

Source: MIT

4 comments
Bob
The earth is pretty darn insulating and magma is underneath it everywhere. So how does this igneous rock emit carbon in the sedimentary layers above it? We have magma under flowing all kinds of land around volcanoes. What about Yellowstone? Are there there massive releases of carbon from overlying sediment there? Wouldn't a much smaller amount of SO2 acidify the oceans and create acid rain over land. Could SO2 be the real culprit or is this another attempt to prop up the CO2 global warming theory?
F. Tuijn
Let's look again at the Deccan traps. Did that too cooked the Carbon out of overlaying sediments? What was the exact time of the dying of most dinosaurs, the hit of that comet or whatever and how fit those in the history of those traps.
Nik
The Earth orbits the sun, and the sun orbits the centre of the galaxy, every 600 million years. Every 150 million years the solar system passes through one of the arms of the galaxy. During that passage, solar radiation reaching Earth is significantly reduced, due to interstellar dust, and the Earth will experience a major ice age. This has Malenkovitch ice age cycles superimposed upon it, approximately every 100,000 years. It will also experience increased meteor strikes, together with increased volcanic and earthquake activity, due to gravitational effects. The Permian extinction was one of these events, which can last for several million years. The 'snowball earth' event was another, and the present period, which is some 600 million years since then, is a repeat of that event. Looking inward for causes of major events on Earth is rather like inspecting the engine of a crashed car, to determine the reasons for the crash. It has been determined by others, that the volcanic eruptions during the Permian, which lasted for tens of thousands of years, pumped vast quantities of hydrogen sulphide into the atmosphere, which in turn caused sulphuric acid rain, for similar periods. This destroyed plant life, and animal life dependent upon it then died, almost totally. CO2 during the extinction period was minimal, compared to periods before and after this event, and the lowest recorded until the present. So while it may be politically popular to blame CO2 for just about everything, in this case the blame is probably misplaced.
Douglas Bennett Rogers
The cellular requirement of 4% CO2 probably developed in this period or an earlier one.