Scientists Crushed Rocks in Iceland—and May Have Solved the Fall of the Roman Empire

• A research team studied unusual rocks in Iceland to better understand the Late Antique Little Ice Age.

• The team believes that rapid climate cooling contributed to a mass migration of people within Europe.

• The information comes from tiny zircon crystals found inside the rocks.

Unusual small stones on a beach in Iceland may help tell the story of the Roman Empire’s demise.

A team of researchers from three different continents studied local cobbles—round stones about the size of a human fist—and the mineral clues embedded within them to better understand a dramatic climate event from the sixth century A.D. that coincided with the undoing of one of the world’s greatest dynasties.

“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, professor of Earth science at the University of Southampton, said in a statement.

Historians have long debated the role of rapid cooling as part of the fall of the Roman Empire, but the new rock-based research strengthens the case that a brief (but intense) period of cooling may have hampered an already declining empire and incited a mass population migration that reshaped Europe. The team behind this research published a study describing their findings in the journal Geology.

The timing of what is known as the Late Antique Little Ice Age has always intrigued historians studying the ties between the climate and European history. Three massive volcanic eruptions around 540 A.D. likely triggered the brief but impactful climate shift, as volcanic ash blocked sunlight and lowered global temperature for around 200 to 300 years.

So, where do these rocks come in? Well, the scientists believe the rocks were carried to Iceland via icebergs formed during the glaciation event, and can now help show the chaotic nature of the climate during that period of history.

“We knew these rocks seemed somewhat out of place because the rock types are unlike anything found in Iceland today,” Christopher Spencer, lead author of the research, said in a statement.

The team crushed the rocks in question to analyze the age and composition of zircon crystals locked inside, which helped pinpoint their source.

“Zircons are essentially time capsules that preserve vital information including when they crystalized as well as their compositional characteristics,” Spencer said. “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 team linked the debris to specific regions in Greenland. “This is the first direct evidence of icebergs carrying large Greenlandic cobbles to Iceland,” Spencer said.

“On one hand, you’re surprised to see anything but basalt in Iceland, but having seem them for the first time, you instantly suspect they arrived by iceberg from Greenland,” Ross Mitchell, a co-author of the study, said in a statement.

“The fact that the rocks come from nearly all geological regions of Greenland provides evidence of their glacial origins,” Gernon said. “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 determined the ice-rafted rocks were likely dropped in Iceland in the seventh century, coinciding with a major climate shift known as the Bond 1 event. “This timing coincides with 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 shore,” Gernon said.

The “climate-driven iceberg activity may have been one of the many cascading effects of rapid cooling,” Spencer said, alongside the mass human migrations that spread the population of Europe across the continent, helping to weaken—and eventually extinguish—the Roman Empire.

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