Volcanic eruptions around 1345 directly caused the Black Death pandemic by triggering climate changes that forced Italian merchants to import plague-infected grain from the Black Sea. The eruption created a domino effect: sulfate aerosols blocked sunlight, crops failed across the Mediterranean and desperate grain imports carried Yersinia pestis-infected fleas that jumped to humans within weeks of arrival. This rare confluence of environmental and social factors demonstrates how climate disasters can inadvertently introduce devastating pandemics.