It's actually the magma which was at least 36 cubic miles (ash ejected was probably by multiples greater than that)
Vesuvius is, of course, part of that same Campanian Volcanic Arc that includes Campi Flegrei. In fact, the whole Bay of Naples is effectively a giant caldera.
Interestingly, and tying in with your first paragraph of that post, Roger, this Wiki article says:
https://en.wikipedia.org/wiki/Campanian_volcanic_arc
Having been to Naples, I can say that if a nearby volcano did majorly erupt, it would cause millions of Euros worth of improvements.
Originally Posted by: Saint Snow