Alaskan volcano sealed the fate of the Roman Republic, led to the rise of the Empire

A volcanic eruption in Alaska has triggered climate change this may have precipitated the end of the Roman Republic, leading to the rise of the Roman Empire, according to a new study.

During 43 BC. AD and 42 BC. AD, Europe and North Africa were exceptionally cold and rainy; temperatures were cooler than they had been for over 2,500 years. As crops failed and famine and disease set in, social unrest and political upheaval increased. (It didn’t help that Roman dictator Julius Caesar was assassinated in 44BC, the year before the cold snap.)

Scientists have long suspected that a massive volcanic eruption caused the cold snap that lasted for two years. And now the researchers have identified the volcano responsible: Mount Okmok on Umnak Island in Alaska. They used geochemical analysis to confirm that in 43 BC.

Related: The 10 most dangerous countries for volcanoes (photos)

Climate models and climate proxies – imprints of past climatic events preserved in plants, rocks, shells and fossils – revealed that during this period, the Mediterranean experienced a significant two-year cooling, with average temperatures can reach 13 degrees Fahrenheit (7 degrees Celsius), the scientists reported in the study. Arctic ice cores contained evidence of significant volcanic fallout (concentrations of sulfur and sulfuric acid) which accumulated during the first century BC, suggesting that a volcano was responsible for the cooling.

However, it was difficult to locate the specific rash. For volcanic eruptions over a few centuries old, scientists use the amount of radioactivity carbon-14, or a version of the element with eight neutrons, to approach their age. Since carbon-14 decays at a predictable rate, the amount present at a site can reveal how long it has been around. But a downside to this technique is that carbon-14 dating involves “reasonably large uncertainties,” said lead author of the study, Joe McConnell, a research professor of hydrology at the Desert Research Institute in Reno, Nevada.

In fact, prior to this study, the Okmok II eruption was dated 190 BC. and AD 50, “based on herbs or other organic material found just below the volcano eruption footage,” McConnell told Live Science in an email.

Volcanic “fingerprints”

To date the Okmok eruption more precisely, the researchers decided to analyze ice cores. Connecting the volcanic fallout from ice cores to a volcano relies on two things. First, the ice must contain particles of tephra, or volcanic ash. Second, scientists need to match the geochemistry of particles to that of a specific volcano.

McConnell and his colleagues analyzed six ice cores from Greenland; the amount of fallout material in the ice suggested that the first century eruption was significant, “and we knew Okmok was one of three or four major eruptions that had occurred around that time,” McConnell said . Fortunately, there were dozens of tephra shards preserved in the ice cores.

They also discovered unpublished geochemical data from other tephras that had been collected at Okmok, “and we immediately saw that the geochemistry of the tephra that we found in the ice had a similar geochemical footprint,” McConnell said.

Detailed records of past volcanic eruptions are archived in the Greenland ice cap and have been viewed during deep drilling operations.

Detailed records of past volcanic eruptions are archived in the Greenland ice cap and have been viewed during deep drilling operations. (Image credit: Dorthe Dahl-Jensen)

In contrast, the “fingerprints” of the tephras did not match those of the mount Etna in Sicily; Shiveluch in Kamchatka, Russia; or Apoyeque in Nicaragua, according to the study.

“The game against Okmok was basically perfect,” said McConnell.

Powerful volcanic eruptions eject particles of gas and ash into the stratosphere. While the ash usually disappears within a few days or weeks, the gaseous sulfur dioxide can convert to sulfuric acid, which then condenses to form aerosols, according to the US Geological Survey (USGS). The sun’s radiation is reflected off the aerosols, cooling the planet’s lower atmosphere. In this way, the massive Okmok eruption could have cooled southern Europe and North Africa, the study authors reported.

A republic in crisis

Many factors contributed to the fall of the Roman Republic, but the eruption of Okmok and the climate change what followed was perhaps the straw that broke the camel’s back for the Republic, according to the study.

In 44 BC. Two years of the coldest and wettest weather conditions in over 2 millennia – and the widespread hardship they have caused – may have pushed the Republic to a tipping point.

Ancient Greek and Roman historians painted a grim picture of the cold years. Frequent snowstorms, disease and food shortages plagued the country, with the Roman army at one point reduced to searching for bark, wild fruits and animals “never before tasted by humans”, said writes scientists.

Famine and disease would have worsened the already tumultuous political situation, perhaps enough for the Republic to collapse and give way to the authoritarian rule of the Roman Empire.

Given the circumstances, it is likely that the extreme weather conditions caused by the Okmok eruption had an impact on historical events, McConnell said. While it’s hard to say for sure how much the volcano directly affected the downfall of the Republic, “it seems logical it must have,” McConnell added.

The results were published online on June 22 in the journal PNAS.

Originally published on Live Science.

David C. Barham