Did volcanoes cause Cleopatra's kingdom to fall?

Decreased Nile floods and lack of rain promoted conflicts and war defeats

These catacombs in Alxandria bear witness to the Ptolemaic rule over Egypt. But their empire could have been weakened again and again by the climatic effects of volcanic eruptions. © Asianologist / CC-by-sa 4.0
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Fatal long-distance effect: Frequent volcanic eruptions could have severely weakened the Egyptian empire of the Ptolemies - and perhaps even promoted Cleopatra's final defeat. Because the eruptions weakened the monsoon and thus the rainfall that fed the annual Nile floods in Egypt. The Ptolemaic Egypt experienced revolts and defeats particularly often when the floods of the Nile after such eruptions, as researchers report.

The empire of the Ptolemies is mainly known for Cleopatra - the last queen of Egypt before the Roman conquest in 31 BC. But the reign of the Greek-Macedonian Ptolemies over the empire on the Nile began almost 300 years earlier: after the death of Alexander the Great, they took over the rule and made Alexandria their capital.

Depending on the Nile

"The Ptolemaic Empire had one of the largest Mediterranean cities in Alexandria, famous for its library and lighthouse, " said Joseph Manning of Yale University and his colleagues. "The city was a center of innovation at that time and harbored such great minds as Euclid and Archimedes."

But as advanced as Egyptian civilization was, it had a flaw. Because the entire agriculture and food supply of the country hung on the Nile and its annual floods. Only they brought fertile mud to the fields and provided enough water for plant cultivation. "The ancient Egyptians were dependent on the floods of the Nile driven by the East African summer monsoon, " explains Manning.

Volcanic gases weakened the monsoon and the Nile floods

As it turns out, this dependency could have been fatal to the Egyptians - and especially to the Ptolemaic empire. Because as Manning and his colleagues found out, volcanic eruptions changed the climate several times and weakened the African monsoon. As a result, however, the important floods of the Nile in the two years after such eruptions often stayed out. display

During the years when there was a major volcanic eruption in the tropics or the northern hemisphere, the level of the Nile remained abnormally low during the summer flood. Manning et al. / Nature Communications, CC-by-sa 4.0

The connection between volcanic eruptions and Nile floods was reconstructed by the researchers from several sources. For the chronology of the Nile floods they evaluated historical records, the times of major eruptions of the last 2, 500 years they could reconstruct using ice cores. Finally, climate models showed how the emission of volcanic sulfur gases weakens the African monsoon and thus also the supply of water for the Nile floods.

Revolts in the hunger years

The consequences for Ptolemaic Egypt were palpable, as shown by the comparison of historical events with times of low Nile floods. So the floods after violent eruptions in the years 46 and 44 before Christ remained almost completely. Cleopatra temporarily alleviated the plight of the people by distributing grain from the royal granaries. But that was not enough to compensate for the crop failures. As a result, a revolt broke out a little later.

The 20 years lasting uprising of Thebes from the year 207 BC could at least have been fueled by a series of large volcanic eruptions and the repeated flooding caused by it. "We observed a clear increase in revolts in the eruption years, " the researchers report. In the year 238 BC, a priest's decree mentions a lack of flooding in previous years, while another papyrus reports an "Egyptian revolt".

Conquest campaign aborted

Even the war achievements of the Ptolemans could have had a decisive influence on the volcanic influence of the climate. "The historical data show a significant coincidence in time between the demolition of war and erosion years, " the researchers report. Often, the Egyptian rulers and generals had to break off their war, because in the home had broken out riots.

Even during Cleopatra's reign there were always failures and revolts. Le Louis le Grand / public domain

So Ptolemy III. However, during the third Syrian war in 245 BC, it was as far as Babylon then had to return to Egypt due to internal unrest. "Had he not been called back to Egypt, he would have been the ruler of all the Seleucid territories, " wrote a Roman historian.

Catalyst for social upheaval?

The war of Antony and Cleopatra against Octavian was also hindered by riots in Alexandria. The Egyptian population revolted not only against the "foreign rule" by the Greek-born Ptolemies, but also against the crushing tax burden, which could not be overcome in years with crop failures.

"The failure of the Nile floods promoted by volcanic eruptions could have been a hitherto neglected catalyst for these revolts against the rule of the Ptolemies, " say Manning and his colleagues. But they also emphasize that, of course, the Nile floods were not the only factor that influenced and influenced Egyptian society.

"But our findings provide insight into how the Ptolemaic society and state responded to such hydrological failures, " Manning said. (Nature Communications, 2017; doi: 10.1038 / s41467-017-00957-y)

(Yale University, 10/18/2017 - NPO)