[Taxacom] end-Permian extinction vs. end-Cretaceous extinction

[Kenneth Kinman]

Hi All,
        An article published in Science a few days ago concluded that the end-Cretaceous extinction was caused by the asteroid impact, and that volcanism had very little to do with it.  I would tend to agree.
        However, the cause of the end-Permian extinction is more likely due to volcanism, but the details are more controversial.  In 2018 there was talk of ozone depletion playing a major role.  However, the end-Permian extinction was more extreme in the oceans than it was on land.  I'm not sure how ozone depletion would cause such a major extinction among ocean life (compared to terrestrial life).  Therefore, it makes more sense to me that the major cause was global warming and the oceans becoming very acidic and lowered oxygen levels.
        In any case, the ultimate cause was apparently that massive volcanic activity (not an asteroid impact).  But my question is whether ozone depletion really had much to do with the end-Permian extinctions.  The acidification of the oceans that we are seeing today is less than that at the end of the Permian, and yet it is already causing major problems.  It just seems to me that ocean life in general could adapt more readily to increased ultraviolet radiation than life on land.  Acidification is a whole different story, especially for all those ocean organisms dependent on calcium carbonate for their shells or bones.
                   ------------Ken Kinman