The rise of the Roman Empire was due in part to a gigantic volcanic eruption 6,000 miles away in Alaska, an international team of scientists claims.
The eruption of the Okmok volcano in the Aleutian islands of Alaska more than 2,000 years ago caused a severe cold spell in Europe that led to crop failures, food shortages and political and social unrest, they argue.
That hastened the demise of the Roman Republic and the emergence of the Roman Empire, according to the team of researchers from the US and Britain.
By analysing traces of volcanic ash in ice core samples from the Arctic, they found that Okmok volcano erupted in 43BC – a year after the assassination of Julius Caesar in 44BC.
The eruption was one of the largest of the last 2,500 years and would have sent colossal quantities of ash into the sky, leading to alterations to the climate worldwide.
Europe suffered unusually wet conditions and an extreme cold spell, with some regions seeing average temperatures drop by as much as 7C (13F) below normal.
Immediately after the eruption there were ancient Roman accounts of “crop failures, famine, disease and unrest in the Mediterranean – suggesting significant vulnerability to hydroclimatic shocks,” the scientists said.
They pointed out that “historians have previously speculated that a large volcanic eruption of unknown origin was the most likely cause.”
Their findings did come with a caveat.
“While it is difficult to establish direct causal linkages to thinly-documented historical events, the wet and very cold conditions from this massive eruption on the opposite side of Earth probably resulted in crop failures, famine and disease,” they wrote in the Proceedings of the National Academy of Sciences.
Those changes would have “exacerbated social unrest and contributed to political realignments throughout the Mediterranean region at this critical juncture of Western civilisation.”
The eruption on Umnak island in the eastern Aleutians coincided not just with the end of the Roman Republic but also the fall of the Ptolemaic Kingdom in Egypt, heralding the end of the pharaohs.
“To find evidence that a volcano on the other side of the Earth erupted and effectively contributed to the demise of the Roman (Republic) and the Egyptians and the rise of the Roman Empire is fascinating,” said lead author Joe McConnell of the Desert Research Institute in Reno, Nevada. “It certainly shows how interconnected the world was even 2,000 years ago.”
By cross-checking with other climate evidence from around the world, including tree-ring records in Scandinavia, Austria and California, as well as caves in China, they found that the two years following the eruption were some of the coldest in the Northern Hemisphere for 2,500 years.
They were also very wet, with autumn rainfall in southern Europe up to four times heavier than normal.
“In the Mediterranean region, these wet and extremely cold conditions during the agriculturally important spring through autumn seasons probably reduced crop yields and compounded supply problems during the ongoing political upheavals of the period,” said Andrew Wilson, a classical archaeologist from Oxford University.
Prof McConnell, an expert in glaciology and ice core chemistry, said while many factors contributed to the fall of the Roman Republic and Ptolemaic Kingdom, the volcanic eruption in Alaska played an important role.
Other academics were not convinced, however. Mary Beard, professor of classics at Newnham College, Cambridge University, said the link between the volcanic eruption and the downfall of the Roman Republic was “very thin.”
“I am not a scientist, but I am always suspicious of theories that use eruptions, plagues or other natural disasters as off-the-peg explanations,” said Prof Beard, the author of “SPQR, a history of ancient Rome, and Pompeii.”
“There is more than enough to account for the end of the Republic – class conflict, spiraling debt, disparities in wealth, political competition gone mad – without needing the volcano,” she told The Telegraph.