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Conservation Science for a Healthy Planet

Underground magma triggered Earth’s worst mass extinction with greenhouse gases; similar to today’s symptoms

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1 August 2017 by Howard Lee Read full GuardianUK article here

….Of some 18 major and minor mass extinctions since the dawn of complex life, most happened at the same time as a rare, epic volcanic phenomenon called a Large Igneous Province (LIP)Many of those extinctions were also accompanied by abrupt climate warming, expansion of ocean dead zones and acidification, like today.

Earth’s most severe mass extinction, the “Great Dying,” began 251.94 million years ago at the end of the Permian period, with the loss of more than 90% of marine species…. why was the mass extinction event much shorter than the eruptions? And why did the extinction happen some 300,000 years after the lava began to flow?

In a new study published in Nature Communications, Seth Burgess of the US Geological Survey, along with James Muirhead of Syracuse University and Samuel Bowring of MIT, think they have the answer.

….In other words, it wasn’t the lava, it was the underground magma that started the killing, by releasing greenhouse gases.

Norwegian scientist Henrik Svensen had earlier identified hundreds of unusual volcanic vents called “diatreme pipes” all over Siberia that connected underground intrusions of magma (“sills”) to the atmosphere, showing signs of violent gas explosions. This new work emphasizes the importance of Svensen’s 2009 conclusions:

The diatremes that have been mapped are the geologic representation of that gas escape on a catastrophic level. Our hypothesis is that the first sills to be intruded are the ones that really do the killing [by] large scale gas escape likely via these diatremes.

Svensen, who was not involved in Burgess’ study, commented:

The Burgess et al paper is a crucial step towards a new understanding of the role of volcanism in driving extinctions. It’s not the spectacular volcanic eruptions that we should pay attention too – it’s their quiet relative, the sub-volcanic network of intrusions, that did the job. The new study shows convincingly that we are on the right track.

Greenhouse gas as a killer

While other scientists have proposed that an array of killers may have been involved in the end-Permian mass extinction, from mercury poisoning to ultraviolet rays and ozone collapse to acid rain, Burgess argues that it was principally greenhouse gas emissions triggered by magma intrusions that caused the extinction through abrupt global warming and ocean acidification.

Geologically fast build-up of greenhouse gas linked to warming, rising sea-levels, widespread oxygen-starved ocean dead zones and ocean acidification are fairly consistent across the mass extinction events, and those same symptoms are happening today as a result of human-driven climate change. Even though the duration of those past events was longer, and the volume of emissions was larger than we will produce, we are emitting greenhouse gases around 10 times faster than the most recent, mildest example – the PETM. The rapidity of today’s emissions prompted scientists Richard Zeebe and James Zachos to observe in a 2013 paper:

The Anthropocene will more likely resemble the end-Permian and end-Cretaceous disasters, rather than the PETM.

When the promises made for the 2016 Paris Agreement on climate change are added up, they aim to limit peak warming this century to about 3.3ºC compared to about 4.2ºC for the business-as-usual scenario, and the 2ºC limit the world is aiming to stay under. It’s sobering to compare those numbers to the majority of mass extinctions in the geological record which were characterized by abrupt warmings typically around 6-7ºC.

S. D. Burgess, J. D. Muirhead & S. A. Bowring. Initial pulse of Siberian Traps sills as the trigger of the end-Permian mass extinction. Nature Communications 8, Article number: 164 (2017) doi:10.1038/s41467-017-00083-9

 

 

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