Arguments
Underground magma triggered Earth’s worst mass extinction with greenhouse gases
Posted on 1 August 2017 by howardlee
Coincidence doesn’t prove causality, as they say, but when the same two things happen together over and over again through the vast span of geological time, there must be a causal link. 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. Precise rock dates published in 2014 and 2015 proved that the extinction coincided with the Siberian Traps LIP, an epic outpouring of lava and intrusions of underground magma covering an area of northern Asia the size of Europe.
But those rock dates presented science with a new puzzle: 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?
Now 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. As Burgess told me:
It’s clearly not the entirety of the LIP that’s guilty. There’s a subinterval that’s doing the work, and I set out to figure out which subinterval that was, and what makes it special.
Burgess noticed that the beginning of the mass extinction, as well as a jolt to the carbon cycle and abrupt climate warming, coincided exactly with a switch in the style of volcanic activity in the Siberian Traps. During the initial 300,000 years of the eruptions, basalt lava poured over a vast area of Siberia building to several kilometers thick. In this time there was some stress to life in the Northern Hemisphere, but no mass extinction. Life only began to disappear across the globe at exactly the same time that lava stopped erupting above ground, and instead began to inject as sheets of magma underground.
In Siberia you have got the Tunguska Basin which is a thick package of sediments that contain carbon-bearing rocks like limestone and coal. When you start intruding magma, [it] cooks those sediments and liberates the volatiles. So the deadly interval of magma in the entire Large Igneous Province is the first material to intrude and pond into the shallow crust
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. I asked him to outline the evidence for that.
There are 3 primary lines of evidence that support that link. The first is: right before the onset of the mass extinction we have evidence for a massive input of isotopically light carbon into the marine system.
He went on to explain various lines of evidence that point to the source of that carbon being methane and carbon dioxide resulting from magma intruding and cooking organic-rich sediments. He continued:
Just prior to extinction and persisting after the mass extinction the sea surface temperature is thought to have gone up about 10°C. You get that increase by pumping greenhouse gas into the atmosphere. So that’s the second.
And then the third line of evidence is a physiologic selectivity to the marine mass extinction. Organisms that make their shells out of calcium carbonate suffer much higher mortality than organisms that make their shells out of silica, for example, which suggests that the ocean was acidified, and you get that by pumping gases like CO2 into the atmosphere.
That’s not to say that other factors had no role in ruining the environment:
There is a cacophony of kill mechanisms, and I think that this first pulse of sills is the trigger for quite a few of those, sitting at the top, and beneath it are a cascade of negative effects from ocean acidification to climate warming and on down the line.
A series of associated events
Coincidentally, Joshua Davies of the University of Geneva and colleagues have just narrowed down the trigger for the end-Triassic mass extinction, another of Earth’s biggest mass extinctions, to the underground phase of its associated Large Igneous Province. The Central Atlantic Magmatic Province (CAMP) is another enormous igneous province which stretches from Maine to South America, and includes the Palisade Sill visible from Manhattan.
They too used high precision rock dates on a vast sill that intruded organic rich sediments in the Amazon Basin, and found that this underground magma intrusion also coincided with the extinction. Like Burgess, Davies also argues that greenhouse gas baked from sediments drove climate change, which drove the mass extinction in a smaller repeat of the end-Permian events, this time 201.5 million years ago.
“I think CAMP is very similar to the Siberian Traps and that’s the reason why there’s an extinction at that time. I’m not surprised that they got similar results,” said Burgess.
Diatreme pipes from magma intrusions have also been identified as a likely cause for a more recent global warming and very minor extinction event – the Paleocene–Eocene Thermal Maximum (PETM) 56 million years ago. Again, prodigious quantities of greenhouse gases erupted from oil-rich deposits, although in that case it’s been hard to locate and date the “smoking gun” intrusions due to the fact that they are under the Atlantic Ocean.
A predictive model
Burgess’ insight makes a testable prediction:
Thanks Howard. While rading it a question of PETM was dorming in my head, until it got answered in the last paragraph.
The evidence points that there is a tipping point in a rate of GHG degassing rate triggered by LIP. Life cannot adapt to the changes too fast, past said tipping point. If we can deduce from said evidence that PETM was not fast enough (i.e. did not reach a tipping point to affect most land forms), then the conclusion is: marine lifeforms will be first to go as the result of AGW. We may be mildly confident that AGW rate is at least as fast as PETM, though it may not have reached the scale of PETM which is another important tipping point not discussed here, but in case the required scale is reached lots of marine species may already be doomed. But to determine the vulnerability land species, a comparison it to end-Permian is required but such comparison is difficult I guess.
Changes and problems in global fisheries already happening, due to warming oceans, from research in Nature
science.time.com/2013/05/16/why-warming-oceans-could-mean-dwindling-fish/
Predictions on effects of global warming on fish species, and possible adaptation problems.
www.gbrmpa.gov.au/managing-the-reef/threats-to-the-reef/climate-change/what-does-this-mean-for-species/fish
is there any way to tell when during the increasing temperature rise the extinctions started. I'm concerned deniers will use the fact that the temperature rise was 6 degrees while our business-as-usual estimate is "only" 4.2 degrees means we don't have to worry.
So an increase of 6 or 7 degrees gets us a mass extinction, whereas a decrease of about 5 degrees gets us an Ice Age. Humanity doesn't have much wiggle room!
To put it in context, then, the 2 degrees of Paris is about a third of a mass extinction and the projected 4 degrees by the end of the century is two-thirds of a mass extinction.
Oh, and you have to note, kmoyd, that under business as usual the temperature passes through 4 degrees at the end of the century on its way to 6 degrees, which is a full mass extinction.
To add to my comment above, there is this statement by Dr Kevin Anderson to the effect that "four degrees is inconsistent with an organized global community". The deniers have no reason not to worry.
"Humanity doesn't have much wiggle room!"
I'm not a climatologist, but to my limited understanding glaciers advance rather slowly (thus the phrase 'glacial pace'). Further, as glaciers cover the near-polar latitudes, the sea retreats. The land exposed is sunnier and richer than the land covered, so it's a net gain in liveability, or so I'd guess.
Besides that, I like ice. The skiing, skating and ice-sailing would be awesome!
While obviously temperatures need to be range to support photosynthesis, but the real issue for extinctions etc is rate of change rather than absolute temperatures. Our civilization has an awful lot of assets that cant move quickly. Local disruptions to agriculture cause a lot of problems. Disruption on a global scale is really testing.
Driving by, yes glacial cycles do happen very slowly over several thousands of years, and the next one is predicted somewhere from 15,000 - 50,000 years time, triggered by a known planetary cycle. I confess I like skiing as well.
However ice sheets covered more than just the polar regions, and covered a lot of canada etc. The following includes maps of the last ice age peak around14,000 bc compared to today:
www.dailymail.co.uk/sciencetech/article-2630738/How-world-looked-ice-age-The-incredible-map-reveals-just-planet-changed-14-000-years.html
However as you say it was a slow process, and new coastal land was exposed. Its easier to adapt to that sort of scenario. Also theres a belief that the warming already locked in will reduce the worst aspects of the next ice age.
I think people are missing my point. We routinely deal with quite a wide range of temperatures in our lives — a few tens of degrees. But when it comes to average global temperatures it looks as if plus or minus four degrees (or even less) is about the limit for an "organized global community". That's a remarkably narrow range.
Digbie Scorgie @9, I dont think anyone is fundamentally disagreeing with you or missing the point. Maybe just looking at other aspects of it.
I mean you are definitely right. I would put it this way. Plus or minus 4 degrees both equals very significant global scale problems. Just one example, both scenarios could drive a lot of climate refugees, the difference being that warming could be faster than a cooling period leading to an ice age, so harder for target countries to absorb, so more potential political and practical problems.
But neither scenario is great, and creates a domino effect of practical, political and social problems that will challenge a stable global order.
We have evolved during about 10,000 years of relative climate stability and it enabled development of settled farming. I dont like the way we are altering stability, too many unknowns and it's hard to see many up sides.
I have a book called Adventures in the Anthropocence which deals with some of this, but haven't read much of it yet.
Humans are adaptable creatures, but not infinitely so, and adaptation requires effort that might be better spent elsewhere.
That's my two cents worth anyway. It's an extremely interesting issue.
Digby Scorgie just adding a further comment, yes we do handle large temperature fluctuations day to day, through adaptations, through necessity, but long term changes are different in substance, and its our choice whether we reduce emissions, or chance it and hope things work out. Or so it seems to me.
This would seem to fit with the dinosaur extinction event. Apparently the asteroid crashed through layers of limestone and gypsum which not only released Carbon dioxide but oxides of sulphur which would have shaded the earth for a while adding a double whammy. Once more the effect of a primary cause effecting carbon rich layers.