Climate change from a massive volcanic eruption played a role in the rise of the Roman Empire, researchers report.
The assassination of Julius Caesar on the Ides of March in 44 BCE triggered a 17-year power struggle that ultimately ended the Roman Republic leading to the Roman Empire’s rise.
To the south, Egypt, which Cleopatra was attempting to restore as a major power in the Eastern Mediterranean, was shaken by Nile flood failures, famine, and disease. These events are among the best known and important political transitions in the history of western civilization. The new study reveals the role climate change played in these ancient events.
Researchers used historical accounts and climate proxy records—natural preservers of an environment’s history (such as ice cores)—to uncover evidence that the eruption of Alaska’s Okmok volcano in 43 BCE caused global climatic changes that sparked the period’s political and social unrest and ultimately changed the course of ancient history.
“Neither Roman scientists nor ancient priests had any notion of Okmok Island.”
The research appears in the journal Proceedings of the National Academy of Sciences.
The team analyzed volcanic fallout records in six Arctic ice cores, and found that one of the largest volcanic eruptions of the past 2,500 years occurred in early 43 BCE. The researchers found that the geochemistry of tephra—rock fragments and particles ejected by a volcanic eruption—originated from the Okmok volcano in Alaska. Climate proxy records show that 43 and 42 BCE were among the coldest years of the recent millennia in the Northern Hemisphere at the start of one of the coldest decades. Further research suggested that this high-latitude eruption led to pronounced changes in hydroclimate, including colder seasonal temperatures in specific Mediterranean regions during the two-year period following the eruption.
The team synchronized these scientific findings with written and archaeological sources from the period, which described unusual climate, crop failures, famine, disease, and unrest in the Mediterranean immediately following the eruption—suggesting, says Joe Manning, a professor of classics at Yale University and a scholar of ancient Egyptian history, that the otherwise sophisticated and powerful ancient states were significantly vulnerable to these climatic shocks from a volcanic eruption located on the opposite side of the Earth.
“We know that the Nile River did not flood in 43 BCE and 42 BCE—and now we know why. This volcanic eruption greatly affected the Nile watershed.”
There were two famines in Egypt during the reign of Cleopatra, both of which took place during a time when the Nile River failed to flood. While there is some rain in the region, there is not enough to sustain agriculture, and Egyptians relied heavily on annual Nile River flood to water their crops, says Manning.
“We know that the Nile River did not flood in 43 BCE and 42 BCE—and now we know why. This volcanic eruption greatly affected the Nile watershed,” Manning says.
One of the texts that corroborated these findings is dated about 39 BCE—year 13 of Cleopatra’s reign—but refers to large-scale famine and social distress of the previous decade. The inscription describes a local governor who saves the population from widespread famine by finding food when there hadn’t been a Nile River flood for several years. He is recognized as a savior by priesthoods, says Manning.
“This inscription does not describe collapse or resilience,” he says. “It is a more complicated story of trying to survive and to figure out how to distribute grain during a very chaotic time.”
Today, Umnak Island, located in the mid-Aleutian Islands, has a population of about 40 people and 7,500 head of cattle. Manning finds irony in the fact that one of the most significant places in world history is in an extremely remote part of the world: “This large volcanic eruption that happened in the winter of 43 BCE had cascading impacts on the climate system and on human societies in the Mediterranean during a vulnerable period of time.”
Yet, he adds, “Neither Roman scientists nor ancient priests had any notion of Okmok Island.”
The new research “allows us to rethink ancient history, especially with regard to environment and climate, and to create a vision of a dynamic, three-dimensional society,” Manning says.
Additional researchers from the Desert Research Institute, the University of Cambridge, the University of Bern, Queen’s University Belfast, the University of Oxford, Trinity College-Dublin, the University of Alaska-Fairbanks, the University of Göttingen, and the University of Copenhagen contributed to the work. An NSF grant funded the project.
Source: Yale University