Scientists Link Mysterious Icelandic Rocks to ‘Little’ Ice Age—and Rome’s Downfall

Many historians agree that the fall of the Western Roman Empire, usually dated to the fall of ancient Rome in 476 CE, marked the end of classical antiquity. What they don’t always agree on, however, is what caused the Empire’s infamous decline. Theories include poor management, pressure from Germanic people, the rise of Christianity, overpopulation, worsening defenses—and even the unfortunate timing of a brief ice age.

A multidisciplinary team has revealed new insight into what’s known as the Late Antique Little Ice Age (LALIA), which is exactly what it sounds like: an ice age that lasted “only” for two to three centuries starting around 540 CE. As detailed in a study published April 8 in the journal Geology, the team discovered rocks in Iceland that had likely traveled to the island from Greenland via icebergs during the LALIA. This period of intense cooling—as represented by the rocks’ ancient journey across the Denmark Strait—may have played a role in the fall of one of the world’s greatest empires.

“When it comes to the fall of the Roman Empire, this climate shift may have been the straw that broke the camel’s back,” Tom Gernon, a study co-author and professor of Earth science at the University of Southampton, said in a university statement. Climate scientists theorize that the LALIA followed volcanic eruptions whose ash blocked the Sun and caused temperatures to plummet. According to the statement, the cooling may have triggered some of the mass migrations that took place in Europe at this time.

Just like Germanic warriors may have stood out among Roman legionaries, the rocks Gernon and his colleagues investigated in the study “seemed somewhat out of place because the rock types are unlike anything found in Iceland today, but we didn’t know where they came from,” said Christopher Spencer, lead author of the study and a tectonochemist at Queen’s University in Kingston, Ontario.

Gernon, Spencer, and their co-author, Ross Mitchell from the Chinese Academy of Sciences’ Institute of Geology and Geophysics, crushed the rocks in question to analyze the age and composition of tiny crystals, called zircon.

“Zircons are essentially time capsules that preserve vital information including when they crystallised as well as their compositional characteristics,” Spencer explained. “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.”

The zircon crystals’ “fingerprints” pointed to different regions of Greenland 0.5, 1 to 1.5, and 2.5 to 3 billion years ago—the first direct evidence of Greenlandic cobbles (fist-sized rocks) hitching a ride to Iceland on icebergs. The researchers suggest that the Greenlandic rocks made landfall during the seventh century, aligning neatly with what’s known as the Bond 1 event, a “known major episode of ice-rafting, where vast chunks of ice break away from glaciers, drift across the ocean, and eventually melt, scattering debris along distant shores,” Gernon said.

“The fact that the rocks come from nearly all geological regions of Greenland provides evidence of their glacial origins,” he explained. “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.”

While, as far as we know, the ancient Romans never reached Iceland or Greenland, the ice-rafting event symbolizes broader LAILA cooling patterns that may have kicked the Western Roman Empire when it was already down. While the Roman Empire experienced a warm and stable climate at the beginning of the Common Era, the third through the seventh centuries were marked by unstable weather patterns that fostered the spread of disease and agricultural issues, which exacerbated political and societal tensions.

I know what you’re thinking—the LALIA started over six decades after the fall of Rome, so how could the former have impacted the latter?

To be clear, 476 CE is a symbolic date for the fall of the Western Roman Empire rather than a historically accurate one. In 476, the German chieftain Odoacer overthrew Romulus Augustulus, the last western Roman emperor, but that doesn’t mean that Roman culture or influence disappeared overnight. The Late Antique Little Ice Age likely wreaked havoc on a society already weakened by the fall of its capital.

Beyond reconstructing the iceberg activity that brought foreign rocks to Iceland, the recent study provides an excellent opportunity to reflect on how sudden, dramatic climate change disrupted one of the world’s most powerful civilizations.