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 6

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.