How an Overlooked Eruption May Have Sparked the Black Death

Scientific American ^ | December 4, 2025 | Meghan Bartels edited by Andrea Thompson

[SunkenCiv]

The infamous Black Death -- a pandemic that killed as many as one third to one half of Europeans within just a few years -- may have been aided in its devastation by an unknown volcanic eruption.

That's the hypothesis presented in research published December 4 in Communications Earth & Environment, which argues that the eruption triggered several seasons of climate instability and crop failures. That instability, in turn, forced several Italian states to import grain stores from new sources -- specifically, from regions surrounding the Black Sea. Riding along on those grain stores, the researchers posit, were fleas infected with Yersinia pestis, the bacterium that causes the plague.

Martin Bauch, a medieval and environmental historian... noticed a particularly serious crop failure beginning in northwestern Italy in late 1345 after serious rainstorms. Within just two years, the Black Death had begun, so he was curious whether there might be a connection.

Analyzing records about the grain trade suggested some Italian cities exhausted their typical food supplies, forcing them to import grain from the Black Sea region. Although the measure kept people fed, it may have introduced the Black Death to Europe as a nightmare ride-along, the Bauch and his co-author suggest...

Here a powerful eruption in 1345 stood out.

The eruption itself remains mysterious. The researchers suspect it occurred relatively close to the equator because its debris is visible in ice caps from both poles. But it will take significant additional work to identify the culprit. "Nobody considers this eruption particularly interesting," Bauch says. "We hope that changes."

[fireman15]

I assumed from your post and previous ones that you are very knowledgeable on this subject. I just wanted to clarify with the last chart that for those here who still believe that “climate change” is actually some sort of crisis. In reality the crisis is the rate of spending on inefficient and unreliable sources of energy for electricity and transportation.

[Reverend Wright]

The source of plague in the “Plague Village” of Eyam in Derbyshire is believed to be from imported cloth contaminated with fleas.
https://www.eyamvillage.org.uk

[gleeaikin]

Looking at the chart without explicit date points makes guessing difficult. But, if the last 4 high red lines end in 2024 or 2025, then that could indicate a Tonga eruption effect. This could be dropping based on the last line. More information in a few years.

[fluorescence]

Wow! Looks like climate change makes volcanoes erupt! (/s)

[DoodleBob]

Thank you.

It’s an old trick in plotting to hyperfocus on a narrow segment of the y-axis. When that occurs, there SHOULD be two hash marks on they-axis near the origin.

[John S Mosby]

Appreciate that info. Back then, transport of cloth, anything was not rapid-— took months. So, if it was fleas in the cloth, what were they eating? Fleas obligate blood suckers,maybe even back then they could eat crumbs or plant debris. Fairly sure that all this time, it has been... blood.

So, it was most likely rats feeding their fellow traveling fleas.