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Climate sciences: Volcanic eruptions and the fall of ancient Egypt

Nature Communications

October 18, 2017

Societal revolt in ancient Egypt may have been triggered by volcanic eruptions, climate change, and the suppression of Nile summer flooding according to an article published in Nature Communications this week. The findings provide a demonstration of the interplay between volcanism, climate and society.

The prosperity of Ptolemaic Egypt (305-30 BCE), home to the great city of Alexandria, was directly tied to the river Nile. Driven primarily by monsoon rainfall in the Ethiopian highlands, the Nile’s annual summer flooding was essential to support the region’s agriculture. Detailed writings from the time indicate a correlation between the absence of Nile flooding and societal unrest. However, the primary cause of flood failure remains unclear.

Francis Ludlow and colleagues investigate the possible impact of volcanic eruptions on the Nile’s ability to flood by combining volcano-climate numerical modelling, ice-core catalogued eruption timings, ancient Egyptian documentation of socio-economic behaviour, and recordings from the Islamic Nilometer - an ancient history of Nile water levels. The authors show that weakening of the region’s rain belt and systematic suppression of the Nile flood are consistent with volcanic eruptions and that previously unexplained episodes of societal revolt are statistically linked to these eruptive events. Through further comparisons of the ice-core record with ancient texts documenting key historical events, the authors show that volcanic eruptions may have had a central role in the eventual collapse of the Ptolemaic dynasty and emergence of Ptolemaic Egypt as a Roman Provence.

The vulnerability of Ptolemaic Egypt to volcanic eruptions revealed in this study offers a caution for all monsoon-dependent agricultural regions, presently including 70% of world population.

doi: 10.1038/s41467-017-00957-y

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