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Exactly what caused the collapse of the mighty Roman Empire has been hotly debated practically since the fall itself. Was economic stagnation primarily to blame, or was it societal decay? Did political conflicts mortally weaken Rome’s power, or is its decline owed mostly to a series of invasions from abroad? Was it lead?
In reality, the fall of the empire almost certainly occurred through a complex interplay of socio-political factors—but recent research suggests a brief climate crisis may have contributed more than we thought. The new findings were published on April 11 in the journal Geology by a collaborative team from Queen’s University Canada, the University of Southampton in the United Kingdom, and the Chinese Academy of Sciences in Beijing.
Previous analysis indicates that Earth endured a roughly 200–300 year long ice age starting around 540 CE. Scientists believe that powerful volcanic eruptions that hurled massive amounts of ash and debris into the planet’s atmosphere lowered global temperatures and reduced sunlight. While it was not as intense as other major ice ages, some researchers have argued that this geologic era helped usher in the final days of Rome. Others, meanwhile, contend that the Late Antique Little Ice Age simply coincided with imperial decline.
New evidence supporting the former argument comes from oddly out-of-place rocks collected not from modern areas of the ancient Roman empire, but from Iceland. Although the region is known primarily for its basalt, researchers recently determined certain samples contained miniscule crystals of the mineral zircon.
“Zircons are essentially time capsules that preserve vital information including when they crystallised as well as their compositional characteristics,” said Christopher Spencer, an associate professor at Queen’s University and study’s lead author. “The combination of age and chemical composition allows us to fingerprint currently exposed regions of the Earth’s surface, much like is done in forensics.”
After crushing the rocks and separating out the zircon crystals, Spencer and colleagues determined the minerals spanned three billion years of geologic history that trace specifically back to Greenland.
“The fact that the rocks come from nearly all geological regions of Greenland provides evidence of their glacial origins,” said Tom Gernon, a study co-author and a professor of Earth Science at the University of Southampton. “As glaciers move, they erode the landscape, breaking up rocks from different areas and carrying them along, creating a chaotic and diverse mixture—some of which ends up stuck inside the ice.”
The team argues that the zircon-rich ice could only have formed and drifted hundreds of miles away due to the Late Antique Little Ice Age. According to Gernon, this timing also lines up with a known period of ice-rafting, in which large slabs of ice break off glaciers, drift across the ocean, and subsequently melt to scatter its debris on foreign shores.
Although the team obviously can’t tie zircon minerals to the Roman Empire’s collapse, their lengthy migration inside frozen chunks of glacier further underscore the 6th century ice age’s severity. Knowing this, it’s easy to see how the chillier era’s effects on crops, civil unrest, and mass migrations could further weaken an already shaky Rome.
“When it comes to the fall of the Roman Empire, this climate shift may have been the straw that broke the camel’s back,” said Gernon.
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