The assassination of Julius Caesar, in 44 BCE, triggered a power struggle of almost two decades marking the beginning of the transition between the Roman Republic and the Roman Empire. According to historians, this period was marked by strange observations in the sky, a particularly cold climate and great famines. According to a new study published on June 22, 2020 in the journal PNAS, an eruption in Alaska could be the cause of these disturbances.
An international team of researchers was able to link two historical events which had no a priori connection between them: a period of intense cold in Rome in 44 BC and a volcanic eruption in Alaska. Written sources dating from this period depict a difficult time in the Mediterranean basin: the population suffered from abnormally low temperatures, poor harvests, disease and famine. Troubles that were to culminate with the fall of the Roman Republic. Scientists have long wondered: could a volcano, even located on the other side of the Earth, have sealed the fate of this republic?
The analysis of volcanic ash (tephra) trapped in ice cores collected in the Arctic made it possible to answer this question. Swiss scientist Michael Sigl and American Joe McConnell of the Desert Research Institute (DRI) in Reno, Nevada, began their research after the discovery in 2019 of a particularly well-preserved layer of ash in an ice core. New analyzes of other samples taken in Greenland and Russia, some of which were taken in the 1990s and preserved in archives until today, were also carried out. All these data made it possible to find the traces of two distinct volcanic eruptions: a powerful but brief occurred in 45 before our era and a more important in 43 before J. – C. and whose fallout lasted two years.
A geochemical analysis was then carried out on ice samples dating from the second eruption, and proved to correspond perfectly with that of the Okmok volcano, one of the most important of the last 2,500 years. „The correspondence between the samples couldn’t be better,“ volcanologist Gill Plunkett of Queen’s University Belfast said in a statement.
The team also gathered other evidence from around the world, ranging from weather records based on the analysis of tree circles in Scandinavia, to the formation of caves in northern China. These data were used to fuel a climatic model, according to which the two years following the eruption have been among the coldest in the northern hemisphere in the last 2,500 years. According to this model, average temperatures were about 7 degrees below normal during the summer and fall following the eruption, and precipitation almost 400% higher than normal in southern Europe during the fall.
„In the Mediterranean region, these humid and extremely cold conditions during spring and autumn, very important seasons for agriculture, probably reduced the yield of the crops and created supply problems, at the time of the political upheavals of this period, „detailed archaeologist Andrew Wilson of the University of Oxford. These events also coincided with the Nile’s inability to cover the plains this year, which has resulted in illnesses and famines, added Yale University historian Joe Manning.
The eruption could also explain the strange atmospheric phenomena observed then, such as solar halos, a darkened Sun, or an optical phenomenon showing the image of three suns in the sky. But the authors point out that many of these observations were made before the eruption in Alaska, and could be linked to a smaller eruption of Etna in 44 BC.
According to Joe McConnell, if many factors contributed to the fall of the Roman Republic, as well as the Ptolemaic kingdom in Egypt – also precipitated by the advent of the Roman Empire -, the eruption in question played a big role , and contributes to filling a lack of knowledge which has hitherto left historians perplexed. „Finding evidence that a volcano on the other side of the world erupted and actually contributed to (…) the rise of the Roman Empire is fascinating,“ said the researcher. „It shows how interconnected the world was, even 2,000 years ago,“ he added.