When you imagine how ancient Egypt fell, you may envision pharaohs on their knees in stone temples, imploring stone deities to have mercy on a famine-ravaged kingdom infested with disease and political upheaval. The gods may have been rumored to have explosive tempers—but it was something else that erupted and foretold the kingdom’s doom.
Egypt’s Ptolemaic pharaohs ascended to power with the rise of Alexander the Great and crumbled after Cleopatra’s suicide. Their rule was not only influenced by royal viziers and scorching affairs, but also by volcanoes. Records from that era that survived several thousand years speak from beyond the grave about eruptions that suppressed the flooding of the Nile, which in turn devastated crops to the point that Ptolemy III needed to put aside his dreams of military conquest. His gold instead went toward grain for the kingdom, and his energy toward fending off a famine-induced revolt.
Cleopatra fared no better. Besides all the scandalous talk of what really went on behind the curtains of her chamber, including the debate about whether she really succumbed to a snake, her rule was poisoned by "famine, plague, inflation, administrative corruption, rural depopulation, migration, and land abandonment," Yale historian Joseph Manning wrote in a study recently published in Nature Communications.
“Eruptions are associated with revolt onset against elite rule, and the cessation of Ptolemaic state warfare with their great rival, the Seleukid Empire,” Manning explained. “Eruptions are also followed by socioeconomic stress with increased hereditary land sales, and the issuance of priestly decrees to reinforce elite authority.”
Ancient Egypt was so dependent on the Nile that its prosperity depended on the summer flooding of the great river, and when that river ran dry, these hydroclimactic shocks had major human impact. When volcanoes spew smoke and lava, they choke the stratosphere with sulfurous gases that would react and morph into sulfate aerosols that would influence hydroclimate (and the prosperity of the Ptolemaic dynasty) in several ways. Volcanic aerosols scatter solar radiation into space. Temperatures in the troposphere will then decrease, which prevents any change in relative humidity, and rainfall suffers.
Manning’s team used summer flood measurements from the Islamic Nilometer, the annual observations of the Nile’s behavior that were recorded for over a thousand years starting in 622 CE. They compared the flooding of the river during volcanic and non-volcanic years to better understand what climate change could have been like during Ptolemaic rule. Volcanic years showed significantly lower water levels. The team also found that eruptions during the era were frequent, and the revolts and priestly decrees at the time support this evidence.
“Revolts of varying severity and extent are signaled in papyri and inscriptions,” observed Manning, also noting that revolts were sometimes delayed by temporary coping strategies, but nevertheless ended up erupting just like the volcanoes. He is wary that the sleeping behemoths that once started literal and political fires won’t always stay asleep. Scientists should use the chaos of the past as motivation to find a solution before both magma and strife explode again.