Interesting article.  Ocean acidification due to increased CO2 output from volcanism has been suggested as cause of other mass-extinction events as well.  What the article didn’t say is that all corals believed to have become extinct at end of Permian.  Paleozoic corals all used calcite for skeletons; modern scleractinians all use aragonite (also found in spicules of some sea anemones); also there’s a 15 million year gap before corals reappeared in Triassic.  So effects of ocean acidification on corals especially can be seen in this extinction.
A bit more on mass-extinctions caused by increased volcanic activity (causing global warming, acid rain, ocean acidification, and widespread anoxia):
Permo-Triassic – actually two distinct extinctions, one 9 Ma before end of Permian due to eruptions in China, then the one at end of Permian due to Siberian Traps eruptions through deposits of coal (releasing methane, another greenhouse gas in addition to the usual water vapor and carbon dioxide).
Late Triassic – two events, one 15 million years before end (changes in plant communities eliminated the dominant large land animals at the time, paving the way for the little dinosaurs to  diversify and “take over”), then one at end of Triassic.  Both attributed to eruptions during early rifting of Pangaea (volcanoes in New Jersey and other places)
End Cretaceous – major eruptions in Deccan Traps of India, with same effects (also iridium comes from volcanoes).  Old idea of asteroid impact causing extinction called into question with recent questions about supposed impact crater in Yucatan.
It’s interesting that during Cretaceous Period, subduction-related volcanic activity was so intense that CO2 levels may have been more than 10 times present levels, but no major mass-extinction. Oceans apparently did not acidify as much, possibly related to great bloom of newly-appeared calcareous plankton and continuation of density-driven oceanic circulation (which had shut down in Permian extinctions).  Oceans and shallow seas did become anoxic at times (even from bottom up to within 100 m of sea level), the reason perhaps 70 percent of world’s petroleum is from Cretaceous rocks.
Implications to us today: we’re worried about even doubling the CO2 content of atmosphere.  In Cretaceous the increase in levels was very gradual over millions of years.  If we continue our current trend (we’ve accelerated the natural trend from volcanic eruption contributions), there will not be enough time for life, etc to adjust.  Can we expect increased ocean acidification and another catastrophe of shelled critters?
Volcanoes do impact climate: look at recent eruptions of the Icelandic Eyjafjallajökull and Grimsvötn and think about the interesting winters we’ve had (or haven’t had) – there definitely is a connection…
- Dr. Rick Batt, paleontologist

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