Mt. Okmok bites

How an Alaskan eruption rocked Ancient Egypt.

Volcanic eruptions are playing an increasingly conspicuous role in the study of ancient climate change. Think Frankenstein, 1815: ‘the Year without a Summer,’ and Mary Shelley. Shelley wrote her classic novel while living through a miserable summer at the Swiss Lakes caused by the eruption of Mt. Tambora in Indonesia. In recent years, important research has examined the impact of Icelandic eruptions on medieval agriculture and many other volcanic events.


Now a new eruption has entered the climatic equation: Mt. Okmok in the Aleutian Islands of the North Pacific in 43 BC. This was the largest eruption in the Northern Hemisphere in the past 2,500 years. Tree-rings records from California’s White Mountains identify the decade between AD 43 and 33 as exceptionally cold as a result. Italy endured cold summers that disrupted agriculture and military campaigns. And, 6,000 miles from Alexandria, Nile floods failed for several years leaving famine in their wake. The unique geochemical signature of the Okmok eruption appears in six Arctic ice cores that document abrupt cooling and drought in the 30s BC through the Mediterranean world.


The Okmok eruption occurred soon after the assassination of Julius Caesar in Rome in 44 BC. During the resulting chaos, Ptolemaic Queen Cleopatra turned to Marc Antony as a potential ally (see issue 3 of our magazine), but he was defeated at the Battle of Actium in 31 BC, and she committed suicide. Egypt now became a province of the Roman Empire. Recovery from the eruption must have been slow, given the political chaos along the Nile, but the economy recovered and Egypt became one of Rome’s major granaries. Both Rome and Constantinople depended on Egyptian grain, which made millions more people exceptionally vulnerable to low Nile floods in later centuries.


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Image: Aerial view across Okmok Caldera, Alaska.