If Ilopango came for you, there was no escape.
In A.D. 539 or 540, the largest volcanic eruption witnessed by humans in Central America immediately killed between 40,000 and 80,000 people and soon led to the death or displacement of hundreds of thousands more, according to estimates by Robert Dull, an incoming faculty member and the lead author on a study published this August in Quaternary Science Reviews.
“It’s a flame thrower, and you cannot run,” said Dull, indicating on his team’s map where superheated gas and pulverized rock flowed. “This shows you the area where everybody died.”
Although the shocks to Maya civilization were significant, they represented only the regional effects of the eruption.
As it happened, just three or four years earlier, in 536, a separate volcanic eruption at a northern latitude had been large enough to darken skies and cause crop failures. When Ilopango blew up into the stratosphere, its load of sulphur dioxide spread around much of the globe to reflect solar rays away from Earth.
The combined effect of these eruptions produced a 14-year cooling event across the Northern Hemisphere. Average temperatures dropped by as much as 3.6 degrees Celsius, causing famine and societal disruptions. The cooling is even tied to the first outbreak of bubonic plague in Europe in 541.
Generations of geologists and other scientists have disputed both the dating of the Ilopango eruption and the source of the sixth century’s big chill. Some theorized that an asteroid or comet did the dirty work.
Dull’s longstanding interest in the case was renewed in 2018 with two discoveries. Volcanic ash from 536 was found in a Greenland ice core, suggesting that volcanic activity was a more likely explanation for the cooling episode than space rocks. Also that year, German researchers pulled up marine sediments showing that Ilopango was far larger in magnitude than anyone had thought.
In 2012, Dull and colleagues visited a site known as El Mico on the outside edge of Ilopango’s old kill zone. Detailed here are a few results from that journey. —Kevin Matthews