Volcanic eruption in Alaska and Roman history | Polarjournal
The caldera of the Okmok Shield Volcano on the island of Umnak extends over 10 kilometers. The caldera formed after the eruption in 43 BC. But the volcano was still active until 2008. Photo: Wikipedia

Much of what is happening in the Arctic is causing major changes in other parts of the world. When conditions change in the Arctic, climate effects are also observed in Europe for example. This can also lead to changes of entire regimes and in politics. An international research team with Swiss involvement has found evidence that a violent volcanic eruption on an island of the Aleutian archipelago was partly responsible for the decline of the Roman Republic and the Egyptian Ptolemaic Empire.

In the study, the two lead authors Michael Sigl of the University of Bern and Joseph McConnell of the Desert Research Institute in Reno, Nevada, found the evidence in ice cores from Greenland and Russia in the shape of ash deposits called tephra. Analysis results found two volcanic activities in the years 45 and 43 BC which had led to the deposits. Geochemical analysis and comparisons with known eruptions at these times led the researchers to the eruption of the volcano Okmok in Alaska. The second eruption, in particular, is one of the strongest volcanic eruptions known in the past 2,500 years. “The tephra match couldn’t fit better,” says specialist Dr Gill Plunkett of Queen’s University in Belfast.

Such ice cores from the Greenland ice sheet are like a window into the past, because deposits from the atmosphere and gas inclusions provide valuable clues to past events, which can then be dated more easily. Photo: Dorthe Dahl-Jensen

The two lead authors found the first evidence of volcanic activity when investigating an ice core. A well-preserved Tephra layer was stored in it. Further investigations on older ice cores, some of which had been drilled in the 1990s, provided further evidence that the “Okmok 2” eruption had been responsible for the deposits. But as the researchers continued to study the effects of the eruption, the true extent of the disaster at the time became apparent. From the analysis of tree rings from Scandinavia, Austria and California, and of cave deposits in northeastern China, the research team found evidence of massive climatic changes after the eruption. Modeling showed that temperatures in the northern hemisphere were up to 7°C lower in summer and autumn, and that summer precipitation was 50-120 percent higher and autumn precipitation up to 400 percent higher in southern Europe.

The timeline shows the amount of sulfur and ash particles in the atmosphere (below), the temperature anomalies in the same period (middle) and historical events of the Roman and Ptolemaic Empire. Photo: Desert Research Institute

Especially in the Mediterranean, where two of the largest empires at this time had been located, these climatic changes had a massive impact. Historians from that time write of crop failures, famines and outbreaks of disease on a massive scale. “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,” says oxford University archaeologist Dr Andrew Wilson. “Particularly striking was the severity of the Nile flood failure at the time of the Okmok eruption,” adds historian Dr. Joe Manning of Yale University. “The climate effects were a severe shock to an already stressed society at a pivotal moment in history.”

The volcanic eruption occurred during a period in which the rule of the Roman empire changed from the people and the Senate to an emperor. Julius Caesar was the first to take sole control. After his death in 44 BC, the change to an empire took place under his stepson Octavian (Emperor Augustus). Photo: Wikipedia

The timing of the two volcanic eruptions coincides with the political upheavals in Rome and Egypt, which are also interrelated. Beginning with Julius Caesar’s seizure of power and his dictatorship and the resulting conflicts and civil wars, the Roman Republic was turned into an empire and the Egyptian Empire became a Roman province. One of the main factors was the supply problems of legionnaires and veterans in the army and of the population. The crop failures and devastated land conditions caused by the climatic changes led to discontent among the population and the army, which encouraged the rise of a leader. Of course, this was not the only factor and the authors of the study are also aware that many different factors had led to the decline of the Roman Republic and Egypt. But the eruption of the Okmok was certainly an important factor. “To find evidence that a volcano on other side of the earth erupted and effectively contributed to the demise of the Romans and the Egyptians and the rise of the Roman Empire is fascinating,” concludes lead author McConnell. “It certainly shows how interconnected the world was even 2,000 years ago.”

The map shows the location of the Okmok volcano on the Aleutian island of Umnak. The island is located more than 9,400 kilometers away from Rome. Nevertheless, the eruption of the volcano has influenced the history of Rome and thus of Europe.

Michael Wenger, PolarJournal

Link to the study: McConnell et al (2020) PNAS, E-Pub: 10.1073/pnas.2002722117

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