https://en.m.wikipedia.org/wiki/Anoxic_event https://en.m.wikipedia.org/wiki/Anoxic_event Hydrogen sulfide caused Permian extinction. My favorite theory is th

https://en.m.wikipedia.org/wiki/Anoxic_event https://en.m.wikipedia.org/wiki/Anoxic_event Hydrogen sulfide caused Permian extinction. My favorite theory is that it was caused by massive increase in volcanic activity which was itself caused by a giant meteor hitting earth.