How Volcanoes Caused The Black Death

TL;DR

A 2025 study links a massive 1345 volcanic eruption to crop failures and grain trade that accidentally shipped plague-carrying fleas into Europe.

Key Points

• 1.Ice cores reveal a massive 1345 eruption twice the size of Mount Pinatubo. Greenland and Antarctica ice cores show sulfur spikes in 1329, 1336, 1341, and a giant spike in 1345 representing 14 million tons of sulfur — more than double Pinatubo's 6 million tons — likely from an equatorial volcano near Indonesia.
• 2.The eruption triggered a volcanic winter across Europe from 1345–1347. Tree ring analysis (dendrochronology) across Europe shows abnormally low-density summer growth rings and rare 'blue rings' in northern Spain, indicating multiple consecutive cold summers consistent with volcanic cooling.
• 3.Cold summers caused crop failures and famine in densely urbanized Italian city-states. Venice, Genoa, and Pisa were too densely populated to be agriculturally self-sufficient, relying on grain imports from Sicily, Sardinia, and North Africa — all of which also failed.
• 4.Famine forced Italian cities to reopen trade routes with Mongol-controlled Asia, unknowingly importing plague. Grain ships from the Black Sea carried fleas infected with Yersinia pestis — the bacterium confirmed by 2011 DNA analysis of plague pit skeletons — which had already spread from a strain traced to Kyrgyzstan.
• 5.Cities that didn't import Asian grain were spared the first plague wave. Venice saw plague within 2 months of grain shipments arriving; self-sufficient cities like Milan, Rome, Verona, and Ravenna avoided the first outbreak, directly linking the trade-driven famine response to the Black Death's spread.