Conclusion

Mass extinction theory has come a long way since the initial simplistic impact theories of the 1980s. Today, only the K/T extinction shows evidence of impact, and there is no strong evidence for an impact causing any other mass extinction event. In contrast, the mismatch between major impacts (such as the late Eocene and other Cenozoic impacts, or Manicouagan impact in the late Triassic) and mass extinction shows that only the largest impacts, possibly coupled with flood basalt eruptions, is capable of causing a mass event in the history of life. Massive flood basalt volcanic eruptions occurred in three mass extinctions (K/T, Permian, Triassic), but not in the others, while many other major eruptive events have no correlation with extinctions. The current thinking is that the release of sulfides from the ocean floor, and/or the balance of oxygen and carbon dioxide in the oceans and atmosphere (with our without contribution from major volcanic eruptions) are more critical in the major extinctions that happened at the end of the Devonian, Permian and Triassic.

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