The originator certainly is not from a scientific background.
40 Million years?
Blimey.
Good question tho'.
Lots I would think.
Also sulphur, CO and other nasties.
I've wondered about this too.
The eruption of the Tibetan plateau DID pump more CO2 into the atmosphere than humans have or will.
(Seems we made out just fine).
But the Tibetan Plateau is massive (easily the size of Tibet) and you'd need a good many volcanoes to equal it.