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* 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.

> 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.

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.

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".

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."

  > 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.

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.

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/m...>

(Previously mentioned: <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.

>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

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?