Death came at a devastating rate

The largest mass extinction of the earth's history took only 60, 000 years to eradicate almost all life

Did that look like the near-end of all life on earth? © José-Luis Olivares / MIT
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The worst mass extinction of the earth's history was deadly fast: within only 60, 000 years, it destroyed 96 percent of all sea creatures and 70 percent of the land creatures. This is now a new date. It reveals that the mass extinction 252 million years ago, at the end of the Perm, was a good ten times faster than previously thought. This also provides important clues to its cause, as researchers report in the journal "Proceedings of the National Academy of Sciences".

It was the largest mass extinction in Earth history - and the first to hit the ocean and land alike. 252 million years ago, it extinguished more than 96 percent of species in the sea and 70 percent of all land-based. Among them were the then common giant insects, almost all coral species, sea slugs and sponges. Even in the prime of their development Therapsiden - mammal-like precursor of the dinosaurs - were almost completely extinguished.

The cause of this prehistoric disaster is still unclear. In question would be a climate change, an asteroid impact or even a long-lasting phase of catastrophic volcanism. But in order to clarify this question, another must first be answered: How long did the mass extinction last? For if it took several million years for the devastating effect to unfold, then it makes climate change or other rather slow environmental changes more likely. But if it went faster, an impact disaster or volcanism would be more likely.

New dating of crucial layers

Researchers led by Seth Burgess of the Massachusetts Institute of Technology (MIT) and colleagues from the Chinese Academy of Sciences have now found this crucial answer. The scientists analyzed rock strata from the Chinese Meishan for their study. In this region, several layers from the period of the transition from the Permian to the Triassic lie close together. Paleontologists interpret this formation as the most important testimony of mass extinction 252 million years ago.

Rock strata of the Permian-Triassic boundary in Meishan. This is where limestone and ash layers alternate. Shuzhong Shen

Researchers collected and analyzed rock samples from these strata and, in addition, found nearby ash and fossil strata from the same ra. Already in 2011, they had published first results, according to which the mass extinction at the end of the Perm could have taken only about 200, 000 years. Now Burgess and his colleagues have refined their dating techniques once again. They isolated zirconium crystals from the rocks and in that measure the ratio of uranium to lead isotopes. display

Too fast for life

The result: The mass extinction was even faster than previously suspected. It only took about 60, 000 years until only a few remnants of the once flourishing animal and plant life of the Permian were left over. According to geological standards, this is only a moment. And one more thing turned up: Immediately before the onset of dying, there was a sudden increase in carbon dioxide in the oceans - they became almost acidic and sea temperatures could have risen ten degrees or more. A large part of the living things in the ocean would already have been doomed to death.

"Obviously, whatever triggered this mass extinction, it quickly became fast enough to destabilize the biosphere before the majority of plants and animals had time to adapt and survive "Burgess explains. But what was it? One candidate who is becoming more and more likely to be affected by the new findings is massive, sustained volcanic eruptions in the so-called Siberian Trapp.

Trapp volcanism is back in the list of suspects

Covering two million square kilometers in northern Siberia, this region of northern Siberia is covered by kilometer-thick basalt strata - prehistoric lava that erupted during major eruptions and buried the entire area until it froze. The most active phase of these eruptions took place almost simultaneously with the mass extinction at the end of the Perm, also 250 million years ago. It used to be thought that the volcanic gases of these huge eruptions changed the atmosphere and climate, triggering a global catastrophe.

According to Burgess and his colleagues, their new dating makes this theory even more likely. A catastrophic eruption could explain where the sudden increase in carbon dioxide in the oceans of that time came from. In 2011, a research group had calculated that the Siberian Trapp could have released more than 170 trillion tonnes of CO2, significantly more than previously thought.

To test whether the Siberian Trapp really was the cause, Burgess and his colleagues now want to date there rock strata in the same way as the deposits of Meishan. In this way, they want to find out whether both events mass extinctions and volcanic eruptions actually fit together in time. "We now have a higher precision than before, one can say that we are gradually moving towards the truth, " says co-author Sam Bowring of MIT. (Proceedings of the National Academy of Sciences, 2014; doi: 10.1073 / pnas.1317692111)

(PNAS / MIT, 11.02.2014 - NPO)