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A while back I read a book called Extinction by Douglas H. Erwin. It was a history of the end-Permian event. There were a few interesting takeaways: 1) When p

A while back I read a book called Extinction by Douglas H. Erwin. It was a history of the end-Permian event. There were a few interesting takeaways: 1) When people started realizing that these dieoffs happened there was a belief that there was probably a common cause like impactors, but end-Permian almost certainly wasn't an impactor like K-T was. There are several things that can kick-off an extinction 2) One thing that is true is that the extinctions seem to follow the same script. Lots of things can kick them off, but once they start going it's a rock rolling down a hill very quicky. End-Permian seems tied to the Siberian Traps basaltic eruption, but that eruption had been going for thousands of years before the dieoff started. K-T definitely happened within years following the impact, but end-Permian seemed to be a "first gradually, then suddenly" as pollution from the traps put more and more stress on the biosphere until suddenly... 3) He posed the question: are we currently in an great extinction. He wrote that we are not because they look at the fossil record of really fundamental creatures (stuff like krill in the ocean) upon which the whole biosphere relies, and we're not yet seeing them collapse. But once such a collapse begins, it will be something that is unstoppable. 4) He thought that there is a big gap in our knowledge of survival and recovery. Why have none of these massive events just turned the planet into a dead world? How does life come back? Historically the early-Triassic was seen as a really boring thing to study because there's not much evidence of life in it, but understanding how life soldiers on through these "wasteland Earth" episodes is potentially a fertile ground for research.

ashoeafoot 2y ago
Some total niche bacteria doing millenias of groundwork.
mapt 2y ago
* End-Permian is associated with the Siberian Traps, but those in turn are associated with the Wilkes Land Crater impactor, which is antipodal to that event and may have seen antipodal seismic focusing. * "Going on for thousands of years" - Dating the End-Permian has confidence intervals on the order of 30,000 years. * Small size and diverse ecology almost guarantees survival of life. There is life basically everywhere we look, down to extremophiles living very slow lives in a random cubic meter of "solid rock" two kilometers deep. We have even evolved several chemical alternatives to photosynthesis as a primary energy source. Mammals and small birds deep in a cave somewhere appear to have been some of the only land vertebrates to survive K-T, and radiated out from there. Evolution does the rest.
- jordanb 2y ago
  > associated with the Wilkes Land Crater impactor Erwin discusses that theory but doesn't agree with it. In any case, 1) there are other mass dyings that are definately not impactors like the oxygen crisis. 2) there are other basaltic eruptions on the scale of the siberian traps (like CAMP) where the cause is known and not an impactor.
- blueflow 2y ago
  P-T is likely not due to the Wilkes Land crater, which would be 2.5x the size of the K-Pg impact and would have left an comparable amount (or more) of iridium in the boundary sediments. There are elevated iridium levels in the P-T boundaries, but only sporadically.
  - mapt 2y ago
    The theory being something along the lines of "Large mantle plume under Siberia suddenly freed when surface crust is fractured in numerous places by extensive antopodal convergence of shockwaves from the Wilkes Land impactor".
    - jordanb 2y ago
      If the Wilkes Land formation is an impact crater (not proven) it's 2x the size of Chicxulub. You don't need any vulcanization in Siberia to explain a mass extinction. But it's not proven to be an impact crater, nor is its age determined with any specificity. There's the lack of Iridium, and Erwin also had complaints about the modeling for an "antopodal convergence crack."
jujube3 2y ago
> End-Permian seems tied to the Siberian Traps basaltic eruption, > but that eruption had been going for thousands of years before > the dieoff started. The eruptions probably hadn't been "going for thousands of years." We can't "see" time periods as small as a few thousands years from a vantage point of 250 million years later. Biologists like to proclaim that things are gradual when they're really more likely sudden. This often reflects mathematical ignorance. For example, if the last specimin of a certain rare fossil is found in a stratum slightly older than the K-T stratum, does that mean it went extinct earlier than the K-T event? Probably not; it just means the fossil is rare so your sampling error is larger.
- jordanb 2y ago
  I'm massively summarizing the book but he talks a lot about the history of the timeline for end-Permian. At the time of writing of the book it was "less than 60k years" which seems like a long time, but when the extinction was first discovered it was believed to be a very gradual change taking place over 10 million years, turns out that it was believed that end-Permian and end-Guadalupian were the same event. As isotope dating has gotten more and more accurate, the length of time for end-Permian has gotten shorter and shorter. There's also other evidence that it was a very sudden event, evidence of fungal explosions for instance during the event suggesting massive amounts of decomposition. In any case, as I said the P-T took "no more than 60k years" but the Siberian traps were erupting for at least 120k years before, so there's at least 60k years unaccounted for between the start of the eruptions and the start of the extinction.
js8 2y ago
> He thought that there is a big gap in our knowledge of survival and recovery. Well, you don't want to know how far you can safely bend over the cliff before falling down. I think attempts to gain such knowledge in a practical way should be explicitly banned.
- jordanb 2y ago
  His point was people should be more interested in the early Triassic.
- deleted 2y ago
  [deleted]
Qem 2y ago
>but end-Permian seemed to be a "first gradually, then suddenly" as pollution from the traps put more and more stress on the biosphere until suddenly... AKA the Seneca effect. See https://terebess.hu/keletkultinfo/seneca.pdf https://terebess.hu/keletkultinfo/seneca.pdf
pfdietz 2y ago
I wonder if the P-T extinction was due not just to CO2 release from the volcanism (and the other bad effects from the magma intruding into the largest/oldest sedimentary basin in the world), but also due to authigenic clay formation in the ocean. When clay forms in the ocean, it pulls calcium out of seawater. Calcium is normally balanced by two bicarbonate ions, so its removal causes the bicarbonate to shift back to carbonic acid/CO2. The ocean acidifies and CO2 is released. This has been called "anti-weathering", since it's the opposite of the normal process that draws down CO2 by weathering of silicates. Sufficient injection of silicic acid and aluminum into the ocean could accelerate this process.
- jordanb 2y ago
  Not sure about clay I haven't heard anything about that. If it formed in large quantities at that time it should still be in sediments. The ocean was acidic and anoxic and that was likely a cause of the extinction. There definitely wasn't enough inorganic carbon released to fully account for the amount of warming that occurred (about 12°C). This was a big part of the book and highly technical (just the explanation of organic versus inorganic carbon was a chapter) so I'm afraid to try to summarize I think I'll get it wrong. But the author's theory was that methane was in the mix as well, released by cooking off carboniferous coal deposits.
  - pfdietz 2y ago
    This is the paper I was thinking of: https://pubs.geoscienceworld.org/gsa/geology/article/50/6/650/612995/Five-million-years-of-high-atmospheric-CO2-in-the https://pubs.geoscienceworld.org/gsa/geology/article/50/6/65... The issue is not just the increase in CO2 at the P/T boundary, but the unusual persistence of high CO2 levels for 5 million years. In contrast, the CO2 spike from the CAMP flood basalts lasted only 300 thousand years. The paper proposes that the ocean became enriched in dissolved silica due to the loss of silica-secreting microorganisms (as indicated by lack of chert deposits during this time), and that this caused enhanced "reverse weathering" that kept CO2 levels high.
Litost 2y ago
Thanks for adding to this. Not an expert on this by any means, but I always found this short series [1] quite fascinating on how cyanobacteria over a period of 200-300 million years coverted the planet from being methane based to being oxygen based, created the ozone layer and paved the way for photosynthesis, oxygen and life as we know it. I can't remember if I'm being too optimistic when I'm recalling bacteria doing something similar for the mass extinctions? See also [2] [1] https://www.bbc.co.uk/programmes/p09xj73n https://www.bbc.co.uk/programmes/p09xj73n [2] https://asm.org/Articles/2022/February/The-Great-Oxidation-Event-How-Cyanobacteria-Change https://asm.org/Articles/2022/February/The-Great-Oxidation-E...
gameshot911 2y ago
Thanks for the great summary!
dredmorbius 2y ago
Concerning: "Why have none of these massive events just turned the planet into a dead world?". Among other rationales: survivorship bias / anthropic principle. Of all the worlds in which a mass extinction event has wiped out all life prior to the emergence of a technologically-advanced species, there would be no (indegenous) witnesses to the fact. We are only here to ponder that question because utter annihilation did not occur. You can make a similar argument about any catastrophic risk/event, and I was delighted to discover a few years ago that Richard Posner (former US federal judge) did just that: By definition, all but the last doomsday prediction is false. Yet it does not follow, as many seem to think, that all doomsday predictions must be false; what follow is only that all such predictions but one are false. -Richard A. Posner, Catastrophe: Risk and Response, p. 13. <https://archive.org/details/catastropheriskr00posn/page/13/mode/2up https://archive.org/details/catastropheriskr00posn/page/13/m...> (Previously mentioned: <https://news.ycombinator.com/item?id=34647615 https://news.ycombinator.com/item?id=34647615>). There are of course other points to be argued, including the resilience of life and its (possible) capacity to re-emerge multiple times. I suspect this was the case in the history of the early Earth, though of course there is vanishingly small prospect of finding any evidence of such an event. Once life did become widespread (~3--3.5 bya) it does seem to have had remarkable tenacity.

ashoeafoot 2y ago

Some total niche bacteria doing millenias of groundwork.

mapt 2y ago

* End-Permian is associated with the Siberian Traps, but those in turn are associated with the Wilkes Land Crater impactor, which is antipodal to that event and may have seen antipodal seismic focusing. * "Going on for thousands of years" - Dating the End-Permian has confidence intervals on the order of 30,000 years. * Small size and diverse ecology almost guarantees survival of life. There is life basically everywhere we look, down to extremophiles living very slow lives in a random cubic meter of "solid rock" two kilometers deep. We have even evolved several chemical alternatives to photosynthesis as a primary energy source. Mammals and small birds deep in a cave somewhere appear to have been some of the only land vertebrates to survive K-T, and radiated out from there. Evolution does the rest.

jordanb 2y ago
> associated with the Wilkes Land Crater impactor Erwin discusses that theory but doesn't agree with it. In any case, 1) there are other mass dyings that are definately not impactors like the oxygen crisis. 2) there are other basaltic eruptions on the scale of the siberian traps (like CAMP) where the cause is known and not an impactor.
blueflow 2y ago
P-T is likely not due to the Wilkes Land crater, which would be 2.5x the size of the K-Pg impact and would have left an comparable amount (or more) of iridium in the boundary sediments. There are elevated iridium levels in the P-T boundaries, but only sporadically.
- mapt 2y ago
  The theory being something along the lines of "Large mantle plume under Siberia suddenly freed when surface crust is fractured in numerous places by extensive antopodal convergence of shockwaves from the Wilkes Land impactor".
  - jordanb 2y ago
    If the Wilkes Land formation is an impact crater (not proven) it's 2x the size of Chicxulub. You don't need any vulcanization in Siberia to explain a mass extinction. But it's not proven to be an impact crater, nor is its age determined with any specificity. There's the lack of Iridium, and Erwin also had complaints about the modeling for an "antopodal convergence crack."

jujube3 2y ago

> End-Permian seems tied to the Siberian Traps basaltic eruption, > but that eruption had been going for thousands of years before > the dieoff started. The eruptions probably hadn't been "going for thousands of years." We can't "see" time periods as small as a few thousands years from a vantage point of 250 million years later. Biologists like to proclaim that things are gradual when they're really more likely sudden. This often reflects mathematical ignorance. For example, if the last specimin of a certain rare fossil is found in a stratum slightly older than the K-T stratum, does that mean it went extinct earlier than the K-T event? Probably not; it just means the fossil is rare so your sampling error is larger.

jordanb 2y ago
I'm massively summarizing the book but he talks a lot about the history of the timeline for end-Permian. At the time of writing of the book it was "less than 60k years" which seems like a long time, but when the extinction was first discovered it was believed to be a very gradual change taking place over 10 million years, turns out that it was believed that end-Permian and end-Guadalupian were the same event. As isotope dating has gotten more and more accurate, the length of time for end-Permian has gotten shorter and shorter. There's also other evidence that it was a very sudden event, evidence of fungal explosions for instance during the event suggesting massive amounts of decomposition. In any case, as I said the P-T took "no more than 60k years" but the Siberian traps were erupting for at least 120k years before, so there's at least 60k years unaccounted for between the start of the eruptions and the start of the extinction.

js8 2y ago

> He thought that there is a big gap in our knowledge of survival and recovery. Well, you don't want to know how far you can safely bend over the cliff before falling down. I think attempts to gain such knowledge in a practical way should be explicitly banned.

jordanb 2y ago
His point was people should be more interested in the early Triassic.
deleted 2y ago
[deleted]

Qem 2y ago

>but end-Permian seemed to be a "first gradually, then suddenly" as pollution from the traps put more and more stress on the biosphere until suddenly... AKA the Seneca effect. See https://terebess.hu/keletkultinfo/seneca.pdf https://terebess.hu/keletkultinfo/seneca.pdf

pfdietz 2y ago

I wonder if the P-T extinction was due not just to CO2 release from the volcanism (and the other bad effects from the magma intruding into the largest/oldest sedimentary basin in the world), but also due to authigenic clay formation in the ocean. When clay forms in the ocean, it pulls calcium out of seawater. Calcium is normally balanced by two bicarbonate ions, so its removal causes the bicarbonate to shift back to carbonic acid/CO2. The ocean acidifies and CO2 is released. This has been called "anti-weathering", since it's the opposite of the normal process that draws down CO2 by weathering of silicates. Sufficient injection of silicic acid and aluminum into the ocean could accelerate this process.

jordanb 2y ago
Not sure about clay I haven't heard anything about that. If it formed in large quantities at that time it should still be in sediments. The ocean was acidic and anoxic and that was likely a cause of the extinction. There definitely wasn't enough inorganic carbon released to fully account for the amount of warming that occurred (about 12°C). This was a big part of the book and highly technical (just the explanation of organic versus inorganic carbon was a chapter) so I'm afraid to try to summarize I think I'll get it wrong. But the author's theory was that methane was in the mix as well, released by cooking off carboniferous coal deposits.
- pfdietz 2y ago
  This is the paper I was thinking of: https://pubs.geoscienceworld.org/gsa/geology/article/50/6/650/612995/Five-million-years-of-high-atmospheric-CO2-in-the https://pubs.geoscienceworld.org/gsa/geology/article/50/6/65... The issue is not just the increase in CO2 at the P/T boundary, but the unusual persistence of high CO2 levels for 5 million years. In contrast, the CO2 spike from the CAMP flood basalts lasted only 300 thousand years. The paper proposes that the ocean became enriched in dissolved silica due to the loss of silica-secreting microorganisms (as indicated by lack of chert deposits during this time), and that this caused enhanced "reverse weathering" that kept CO2 levels high.

Litost 2y ago

Thanks for adding to this. Not an expert on this by any means, but I always found this short series [1] quite fascinating on how cyanobacteria over a period of 200-300 million years coverted the planet from being methane based to being oxygen based, created the ozone layer and paved the way for photosynthesis, oxygen and life as we know it. I can't remember if I'm being too optimistic when I'm recalling bacteria doing something similar for the mass extinctions? See also [2] [1] https://www.bbc.co.uk/programmes/p09xj73n https://www.bbc.co.uk/programmes/p09xj73n [2] https://asm.org/Articles/2022/February/The-Great-Oxidation-Event-How-Cyanobacteria-Change https://asm.org/Articles/2022/February/The-Great-Oxidation-E...

gameshot911 2y ago

Thanks for the great summary!

dredmorbius 2y ago

Concerning: "Why have none of these massive events just turned the planet into a dead world?". Among other rationales: survivorship bias / anthropic principle. Of all the worlds in which a mass extinction event has wiped out all life prior to the emergence of a technologically-advanced species, there would be no (indegenous) witnesses to the fact. We are only here to ponder that question because utter annihilation did not occur. You can make a similar argument about any catastrophic risk/event, and I was delighted to discover a few years ago that Richard Posner (former US federal judge) did just that: By definition, all but the last doomsday prediction is false. Yet it does not follow, as many seem to think, that all doomsday predictions must be false; what follow is only that all such predictions but one are false. -Richard A. Posner, Catastrophe: Risk and Response, p. 13. <https://archive.org/details/catastropheriskr00posn/page/13/mode/2up https://archive.org/details/catastropheriskr00posn/page/13/m...> (Previously mentioned: <https://news.ycombinator.com/item?id=34647615 https://news.ycombinator.com/item?id=34647615>). There are of course other points to be argued, including the resilience of life and its (possible) capacity to re-emerge multiple times. I suspect this was the case in the history of the early Earth, though of course there is vanishingly small prospect of finding any evidence of such an event. Once life did become widespread (~3--3.5 bya) it does seem to have had remarkable tenacity.