Volcanoes triggered the Black Death in medieval Europe: Cambridge researchers

Eruptions wiped out crops in the Mediterranean forcing cities to import grain from the east, bringing with it fleas infected with bubonic plague.

A succession of volcanic eruptions in the 14th century set off a chain of events that would culminate in half of Europe’s population being wiped out by the bubonic plague, Cambridge researchers have found. Picture: AFP PHOTO / INDONESIA'S GEOLOGICAL AGENCY

Since the pandemic, we have often toyed with the question of how it began - and the same riddle over the origins of the Black Death has plagued historians since the Middle Ages. No one, however, thought the answer might lie in volcanoes.

A succession of eruptions in the 14th century set off a chain of events that would culminate in half of Europe’s population being wiped out by the bubonic plague, Cambridge researchers have found.

The surprising theory has come from the study of ancient tree rings and the secrets they have revealed about drastic changes to the climate 680 years ago.

In the middle of the 14th century, when Edward III was on the English throne, there was a marked drop in temperatures that lasted for several years, more than could be explained by natural fluctuations.

An illustration of the bubonic plague breakout in London in 1665.

Analysis of trees from the Spanish Pyrenees show clear patterns of blue-tinged rings, caused by unusually cold and wet summers in 1345, 1346 and 1347 across much of southern and Mediterranean Europe.

Other evidence from the same decade reveals accounts of thick clouds and dark lunar eclipses. The catastrophic conditions caused a devastating crop failure around the Mediterranean.

Threatened with the prospect of famine and riots, the maritime republics of Venice, Genoa and Pisa needed to find food from somewhere, and fast.

“For more than a century, these powerful Italian city states had established long-distance trade routes across the Mediterranean and the Black Sea, allowing them to activate a highly efficient system to prevent starvation,” said Martin Bauch, a historian from the Leibniz Institute for the History and Culture of Eastern Europe, who worked on the research with Professor Ult Buntgen from the University of Cambridge’s department of geography.

The republics began to import large amounts of grain from the Mongols of the Golden Horde, a state ruled by the Khan dynasty around the Sea of Azov, a smaller inland sea that connects with the north of the Black Sea.

The ships that carried grain across the Black Sea brought with them fleas infected with Yersinia pestis, the bacteria that caused the Black Death.

It was previously known that this was their likely route, with the DNA of the disease linked back to wild gerbils in central Asia, but it was not known why the Italians had suddenly needed so much grain.

The study, published in the journal Communications Earth & Environment said research provided evidence of a “sulphur-rich volcanic eruption in around 1345” or a cluster of such eruptions.

The Times