Hey! A subject I know nothing about, but am gonna talk about anyways like I am an authority.
So you see, volcanic activity releases dust and sulfur dioxide, both act as "reverse" green house gasses. That's why we don't have to worry about global warming if the Yellowstone Caldera pops off, it'll give us a nice chilly winter.
Anyways, the colder temps in Europe from volcanic emissions gave them a shit harvest that year so they stole, borrowed, and bought grain from other places and accidentally imported the dreaded Mounted Flea (they rode rats). And they carried the bubonic plague with them to Europe.
ANYWAYS, that's why we have last names and get paid. Silver linings yeah?