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Burning coal may have caused Earth’s worst mass extinction

Posted on 12 March 2018 by dana1981

Earth has so far gone through five mass extinction events – scientists are worried we’re on course to trigger a sixth – and the deadliest one happened 252 million years ago at the end of the Permian geologic period. In this event, coined “the Great Dying,” over 90% of marine species and 70% of terrestrial vertebrate species went extinct. It took about 10 million years for life on Earth to recover from this catastrophic event.

Scientists have proposed a number of possible culprits responsible for this mass extinction, including an asteroid impact, mercury poisoning, a collapse of the ozone layer, and acid rain. Heavy volcanic activity in Siberia was suspected to play a key role in the end-Permian event.

Recently, geologist Dr Benjamin Burger identified a rock layer in Utah that he believed might have formed during the Permian and subsequent Triassic period that could shed light on the cause of the Great Dying.


Sheep Creek Valley, Utah. Photograph: Benjamin Burger

During the Permian, Earth’s continents were still combined as one Pangea, and modern day Utah was on the supercontinent’s west coast. Samples from the end-Permian have been collected from rock layers in Asia, near the volcanic eruptions, but Utah was on the other side of Pangaea. Burger’s samples could thus provide a unique perspective of what was happening on the other side of the world from the eruptions. Burger collected and analyzed samples from the rock layer, and documented the whole process in a fascinating video:

Earth turned into a toxic hellscape

Burger’s samples painted a grim picture of Earth’s environment at the end of the Permian period. A sharp drop in calcium carbonate levels indicated that the oceans had become acidic. A similar decline in organic content matched up with the immense loss of life in the oceans during this period. The presence of pyrite pointed to an anoxic ocean (without oxygen), meaning the oceans were effectively one massive dead zone.

Bacteria ate the oversupply of dead bodies, producing hydrogen sulfide gas, creating a toxic atmosphere. The hydrogen sulfide oxidized in the atmosphere to form sulfur dioxide, creating acid rain, which killed much of the plant life on Earth. Elevated barium levels in the samples had likely been carried up from the ocean depths by a massive release of methane.

The culprit: burning coal

Levels of various metals in the rock samples were critical in identifying the culprit of this mass extinction event. As in end-Permian samples collected from other locations around the world, Burger didn’t find the kinds of rare metals that are associated with asteroid impacts. There simply isn’t evidence that an asteroid struck at the right time to cause the Great Dying.

However, Burger did find high levels of mercury and lead in his samples, coinciding with the end of the Permian period. Mercury has also been identified in end-Permian samples from other sites. Lead and mercury aren’t associated with volcanic ash, but they are a byproduct of burning coal. Burger also identified a shift from heavier carbon-13 to lighter carbon-12; the latter results from burning fossil fuels.

The Permian was the end of the Carboniferous period, which means “coal-bearing.” Many large coal deposits were created in the Carboniferous, including in Asia. Previous research has shown that the Permian mass extinction event didn’t coincide with the start of the Siberian volcanic eruptions and lava flows, but rather 300,000 years later. That’s when the lava began to inject as sheets of magma underground, where Burger’s data suggests it ignited coal deposits.

The coal ignition triggered the series of events that led to Earth’s worst mass extinction. Its sulfur emissions created the acid rain that killed forests. Its carbon emissions acidified the oceans and warmed the planet, killing most marine life. The dead bodies fed bacteria that produced toxic hydrogen sulfide gas, which in turn killed off more species. The warming of the oceans produced a large methane release, which accelerated global warming faster yet. As Burger put it,

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Comments 1 to 27:

  1. Fascinating and plausible theory where a lot of information  fits the theory very well. However how do you get combustion of coal seams underground, because where would enough oxygen come from, or was the coal just ejected somehow from the volcanos?

    On a related matter, a theory has been suggested that the ten biblical plagues of ancient Egypt were caused by a combination of a warming, drying climate and a volcanic eruption on the Mediterranean islands of Santorini, just north of Crete described in this fascinating article.

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  2. nigelj @1

    Large Igneous Provinces such as the Siberian Traps are fissure flow volcanism on a vast scale. This produces fractured surface rock over an extensive area. This could expose coal deposits that could then burn in the presence of lava.

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  3. Active link to Large Igneous Provinces page;

    Large Igneous Provinces

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  4. "It took about 10 million years for life on Earth to recover from this catastrophic event."

    Is that on the species level, from what I've read it took up to 100 million years to recover biological diversity at the Family level?

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  5. Another way of looking at it is that the Great Dying gave rise to new forms of life, including hominids and eventually us. The next one will make way for something else. Perhaps this is what Alexa was laughing about. 

    I suggest we preserve kittens and beagles, perhaps in geo-time capsules. Everything else can be left to chance.*

    *No that is not meant seriously, there is no such movie magic technology, etc. 

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  6. It's also possible that the end Cretaceous extinction event that involved the loss of about 70% of species in a small time frame is also in part the result of vastly accelerated volcanism in the Deccan Traps in what is now India.

    Asteroid impact, volcanism one two punch

    The impactor that created the Chicxulub crater would have produced seimic waves of 11 to 12 on the Richter scale at the site of impact, 10 at the location directly opposite on the Earth's surface and between 8 and 9 everywhere else.

    The evidence seems to point to a liquifaction of the surface at the Deccan Traps which caused a massive pulse of volcanism releasing huge amounts of gases that greatly increased the climate change that was already underway globally and seen in the reduction in numbers of major species like the dinosaurs long before the impact.

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  7. Here is a Wikipedia entry on a coal mine fire that  has been smouldering for over 55 years. The second paragraph says "The fire is burning in underground coal mines at depths of up to 300 feet (90 m) over an 8-mile (13 km) stretch of 3,700 acres (15 km2). At its current rate, it could continue to burn for over 250 years.".

    Granted, a coal mine included a way of getting air in, but clearly the burial hasn't snuffed it out. A large number of such fires would produce a large amount of CO2. Even if it's over hundreds of years, that's a blink of an eye in geological terms.

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  8. Burning Mountain in Australia has an underground coal seam  that has been burning for 6000 years, the oldest known coal seam fire, so just enough air must get in to keep it smouldering. It may have started with a lightening strike, or forest fire igniting part of the exposed seam.

    Large volumes of methane are associated with coal seams, that probably adds to the combustion process producing more CO2.

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  9. It's also important to point out that changing the global environment with the continued massive emissions of greenhouse gases as has happened in the past is not the only impact that is reordering and impoverishing the biosphere.

    There is also urbanization, industrial monoculture, industrial fishing, forestry and more.

    The extinction event we are currently forcing is going to happen much faster than in the past because it is multi-tiered and leaves no ecosystem on the Earth intact.

    Ending massive fossil fuel use is just the start of a process that must occur to mitigate the sixth great ectinction.

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  10. “The culprit: burning coal”.
    Can high level of mercury and lead in the rock samples be considered as a proof of coal burning? I don't think so: it could be a result of thermal decomposition of lead and mercury containing minerals during volcanoes eruptions.
    “Its sulfur emissions created acid rain to kill forests”. More exactly, sulfur dioxide, not sulfur. SO2 is a toxic gas that may kill both vegetable and animal life, especially together with acid rains, and also acidify water (much more than CO2).
    The statement about the combustion of large quantities of coal in the Permian period is not confirmed by CO2 concentration data (~210 ppm):

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  11. I don't see a need for coal deposits in contact with magma to burn (oxidize) below the surfsce since the magma itself provides its own source of intense heat. With contact (or even a near miss!) large portion of the coal would be volatilized in a process similar to coal "gasification". The volatiles will work their way up through fractures and pores in overlying strata to enter the atmosphere as "coal gas",  mostly methane in combination with other hydrocarbons, water vapor, CO², H2S and H²SO⁴. The same catastrophic result as burning, but no oxygen required.

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  12. Typing on a cell phone is a dreadful undertaking. Proofreading is even more difficult. Now I'm revisiting my post on a ten inch tablet. I see that subscripting on my phone was a no-go. Can't get them to work on the tablet either. I''m sure readers were able to get past the typos in my first post, but here are few nearly-corrections anyway:

    CO2, H2S, and H2SO4,

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  13. We could give the Permian a good run for it's money in terms of extinctions.  As man arrived in each previoudly man-less territory, the mega fauna and much of the smaller beasties disappeared.  One of the early ones was Australia, some 50,000 years ago and the most recent, New Zealand some 700 years ago, a period which is a blink of the eye in geological terms.  We are now finishing off the job.  We may go along with the mega fauna and the world will evolve a whole new assemblage of animals.  I wonder why we call ourselves intelligent.

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  14. Aleks @10

    "The statement about the combustion of large quantities of coal in the Permian period is not confirmed by CO2 concentration data (~210 ppm):"

    This biocarb study in an "open access" journal  has a graph using old data with quite a lot of uncertainty, and the graph is a snapshot of permian C02 levels over 50 million of years within the space of only about 1 centimetre on the page, so would probably omit any spikes over short periods. It does however still show a gradual increase in CO2 levels towards the end of the permian.

    The new study on the Permian issue is more up to date. It also finds the injection of CO2 was over a period of just 10,000 years so It would also  not necessarily show up in the biocarb study even if they had this data, because the period is so small. The group also analyzed carbon-isotope data from rocks in southern China and found that within the same period, the oceans and atmosphere experienced a large influx of carbon dioxide. So they have specific evidence.

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  15. Aleks @10

    "Can high level of mercury and lead in the rock samples be considered as a proof of coal burning? I don't think so: it could be a result of thermal decomposition of lead and mercury containing minerals during volcanoes eruptions."

    I doubt it.  The concentrations in the actual rock samples they found are apparently higher than expected to naturally occur. The research team almost certainly would have considered the possibility you describe, and looked at concentrations of lead and mercury you would expect from volcanic igneous rocks breaking down, against the samples they actually found. 

    Also the featured article says "Lead and mercury aren't associated with volcanic ash, but they are a byproduct of burning coal."  

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  16. T R Styles @ 12 (Mod - off topic but for info) Your superscripts appear just fine on my PC so obviously went OK from the phone and tablet: Might just be ine "incoming" text interpretation on them.

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  17. Thanks WOL. I really should dust off my laptop for these things, but I've become addicted to portability. Each keyboard app and wallpaper theme in Android seems to project things differently.

    Hey! I'm a little suprised no one had anything to say one way or the other about "gasification" as a source of P-T greenhouse gases.. I may well be off base on that idea, but still can't see that literal burning is necessary, where hot magmas are involved, to put a lot of nasty volatiles into the atmosphere .

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  18. TR Styles @17, I think your gasification theory sounds very convincing. But I'm not a geologist to say much about it.

    It could of course be a combination of burning and gasification.

    Just to be clear the example I quoted in Australia of coal burning underground was not a mine, and  was a natural seam that somehow caught fire possibly from a forest fire, and somehow enough oxygen gets right down there, possibly as the seam gradually burns from the outside down or just through fissures in the rock, Im not sure. I can believe that the very widespread surface volcanic lava flows during the Permian event ignited more than a few coal seams over extended time periods. But gasification could also have happened and may be the dominant factor.

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  19. Nigelj @14,15
    Thanks for links. None of these links contain a numerical value of suggested spike in CO2 level: what change of initial 210 ppm can be considered as essential and how much coal must be burned for this?
    It's known that 5 great extinction events (see Wikipedia) occurred both at high concentrations of CO2 (Ortodovian-Silurian and Late Devonian) and at low levels (three others). The relationship between CO2 concentration and mass extinction was not proven in any case.
    “Lead and mercury are a byproduct of burning coal”. Byproduct is a secondary product derived from a manufactured product or chemical reaction. Lead and mercury are microimpurities in coal. In itself, presence of of Pb and Hg in samples does not indicate the source of these elements.
    Of course, “lead and mercury are not associated with volcanic ash.” The main lead ore galena (PbS) is very easy to smelt and lead is collected below the ash. As for mercury, its minerals are thermally decomposed, and its boiling point is much lower than melting points of basalt and granite, so it simply evaporates from lava. Anyway, it does not allow to determine the origin of these elements in samples.

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  20. aleks @19, I havent read the research article because is paywalled, but they clearly found evidence of a  substantial increase in CO2 levels and evidence of sulphur oxides etc. It certainly suggests coal burning was a factor.

    I dont think anyone has claimed certainty over this, but nobody has a better theory that explains the evidence including yourself. This is  so typical of sceptics, they pick a few holes around the edges of an idea, but never come up with a better hypothesis.

    Thank's for the information on lead and mercury. Somebody gave me a piece of galena once, an amazing looking very crystaline heavy sort of mineral. 

    I gained the impression that they found lead and mercury in the ash, when normally this would not be expected, so it suggested coal as a source.

    I'm not a chemist, however I think the scientists probably looked at the quantities of lead and mercury you usually find in rocks associated with volcanic eruptions and found the quantities in the permian material were unusually high, which suggested coal may have been involved. They would obviously have also considered other potential sources of these compounds to rule those out. There may be other tests they did as well.You seem to think scientists are all stupid and just guess things, but I find whenever I read the research the opposite is the case. 

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  21. Aleks @19

    You claim "None of these links contain a numerical value of suggested spike in CO2 level:"

    The article I linked said "With further calculations, the group found that the average rate at which carbon dioxide entered the atmosphere during the end-Permian extinction was slightly below today’s rate of carbon dioxide release into the atmosphere due to fossil fuel emissions. Over tens of thousands of years, increases in atmospheric carbon dioxide during the Permian period likely triggered severe global warming, accelerating species extinctions."

    The research  would contain the precise values but its paywalled and I haven't read it. "Slightly below" is good enough information for me. You are nit picking as usual.

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  22. Here is a free copy of the preprint of the paper.  Dr. Burger claims that his data shows a large increase in CO2 that would not have been in previous data.  He claims that this is the first high quality section of the boundry found from the western coast of Pangea.

    I typed "Benamin Burger Permian" into GOOGLE scholar and it was the first hit.  GOOGLE scholar often shows the location of free copies.

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  23. MS thank's for that research paper. 

    It's pretty clear to me that there was a large increase of CO2 during the late permian. That is the most important thing, even if we dont know the exact ppm.

    Sources of both volcanoes and coal  make it pretty compelling to me. And it appears considerable methane was also released as well as sulphur oxides and volcanic ash etc. The period seems like a sort of hell on earth, and I dont think thats hyperbole.

    This article is from Peter Ward, a reputable paleontologist, includes a  graph with a huge spike in CO2 levels in the late permian. The graph  also shows a remarkable correlation between multiple extinction events over millions of years and peaks of CO2 levels. I have no idea how correct this information is, but it's interesting, and he is not a crank or arm chair expert.

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  24. Nigel@19,20
    Yes, I was wrong about the burning of coal, as I was guided by “”. The “secret” value of CO2 level in the period under review was found in Wikipedia article “Permian-Triassic extinction event”. This value is of 2000 ppm and rise in temperature is of 8oC (original source is not in open access).
    So, correct statement may be: “Burning coal is a culprit, but not CO2”.
    At first, 2000 ppm is much less than 7000 in Cambrian or 4000 in Devonian period when both terrestrial and marine life was actively developing.
    Secondly, the increase of temperature can be explained by the release of heat into the atmosphere during combustion, without resorting to the theory of greenhouse effect.
    Third, the combustion of coal is accompanied by the release of toxic gases SO2, NOx, and CO that kill living things both directly and through acid rains (SO2 and NOx).
    Finally, the death of marine organisms is due to acidification of seawater by dissolution of SO2 and NOx and it triggered by H2S.

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  25. Aleks @24, thank's for the comments.

    "So, correct statement may be: “Burning coal is a culprit, but not CO2”.

    I doubt that its that simple. It's entirely possible the extinction during the permain was a combination of global warming from CO2 and methane released by a combination of coal burning and very high levels of mass volcanic activity, along with the considerable ash clouds and sulphur oxides and other toxic material released by the coal. We know all the factors are dangerous for life and all could happen simultaneously, so its certainly plausible. The evidence points that way.

    "At first, 2000 ppm is much less than 7000 in Cambrian or 4000 in Devonian period when both terrestrial and marine life was actively developing."

    These high levels of atmospheric CO2 were reasonably constant over very long periods of tens to hundreds of millions of years, so species would adapt easly enough. The problem is a more sudden spike of CO2 that causes global warming over hundreds of years to thousands of years, maybe a few million years, and this is much harder for species to adapt to.

    The Permian event was over a few thousands of years apparently and more important initiated quite suddenly. You can see from the graph in the Peter Ward article, and that other extinctions correlate with spikes in CO2 emissions in his graph.

    "Secondly, the increase of temperature can be explained by the release of heat into the atmosphere during combustion, without resorting to the theory of greenhouse effect."

    I doubt it. Provide a link to an explanation and full calculations.

    "Third, the combustion of coal is accompanied by the release of toxic gases SO2, NOx, and CO that kill living things both directly and through acid rains (SO2 and NOx)."

    Yes but see my comment above. This most probably combined with global warming.

    "Finally, the death of marine organisms is due to acidification of seawater by dissolution of SO2 and NOx and it triggered by H2S."

    CO2 also acidifies oceans. It's perfectly feasible that they all contributed.

    I'm not a chemist, but I wasn't born yesterday.

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  26. Aleks @25

    "Secondly, the increase of temperature can be explained by the release of heat into the atmosphere during combustion, without resorting to the theory of greenhouse effect."

    It seems unlikely to me that slow burning coal though the permian would significantly raise global temperatures through heat of combustion. There just wouldn't be enough heat from convection etc to warm the huge volume of the atmosphere. Prove it otherwise with calculations.

    We have an adequate explanation for the high temperatures during the permian from high CO2 concentrations, which you post noted at 2000 ppm which would acocunt for approximately 8 degrees.

    This study is relevant and interesting and gives some numerical evidence that direct heat from the combustion of coal burning has little effect on global air temperatures as a whole.

    "That’s the conclusion of a Carnegie Institution for Science study published Tuesday that shows two things: Emissions from burning a lump of coal or a gallon of gas has an effect on the climate 100,000 times greater than the heat given off by burning the fossil fuel itself."

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  27. Thing about coal burning underground is something only someone involved in Biochar would immediately notice, the charcaol one makes to turn into Biochar has to be material burnt with minimum oxygen, otherwise you just create C02 and ash, but better results can be achieved if some water is included, as the high temperature carbon strips all the oxygen from any CO2, creating Carbon Monoxide, and also the Oxygen from the H2O, so creating Hydrogen and then by burning, CO, so the water provides the heat, paradoxically, then the hydrogen and CO travel up to the surface and are either combusted, or, in the case of the CO, react with the oxygen in the atmosphere to produce CO2. Not much heat generated anywhere except at the 'coal face' by burning the oxygen from the groundwater, which keeps the whole thing going. - hope to have helped. 

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