10 July 2020

Climate, Roman and Ptolemaic History

Welcome back. A recently published study identified the cause of abrupt climate change that contributed to some of most important political transitions in the history of Western civilization--the fall of the Roman Republic and Ptolemaic Kingdom and the rise of the Roman Empire. 
Map of Roman Republic in 1st century BCE (from Pinterest).
Historians had speculated that a volcanic eruption of unknown origin was the most likely cause. The study pinpointed the volcano and characterized the eruption severity.

If like me, you’re a bit shaky on that era, I’ll begin with a quickie on the affected transitions. Squeezing centuries into a handful of paragraphs and focusing on dates, I’ve omitted a wealth of important background, such as the relationship between Cleopatra and Julius Caesar.

Historic Background

The Late Period of Ancient Egyptian history ended in 332 BCE, when the Greeks conquered Egypt. The Greeks formed the Ptolemaic Kingdom in 305 BCE, and the Ptolemaic dynasty ruled Egypt until the Romans took control in 30 BCE, with the death of Cleopatra, the last Ptolemaic queen. Despite controlling Egypt for nearly three centuries, the Ptolemaic dynasty never became Egyptian, instead, isolating themselves in Alexandria. 

Rome was a small city-state in the 6th century BCE, governed by kings. The Romans managed to overthrow the monarchy and create a republican government in 509 BCE. The Roman Republic lasted five centuries, growing in strength and conquering swathes of the Mediterranean region. 

Bronze statue of Julius Caesar located
at the Roman Forum in Rome
Although the Roman Republic was a democratic society with elected magistrates, Julius Caesar was appointed and reappointed dictator, the last time in 46 BCE, as Cleopatra was attempting to restore Egypt as a major power in the Eastern Mediterranean.

Caesar was assassinated on the Ides of March, 44 BCE. His death triggered a 17-year power struggle that ultimately ended the Roman Republic and led, in 27 BCE, to the Roman Empire. The Empire would be ruled by a series of Emperors and expand its rule in Asia and Africa.

The political transitions in Rome and Egypt in the 40’s BCE were exacerbated by a period of unusually cold climate, crop failures, famine and disease in the Mediterranean region.

Documenting the Volcano
The study was conducted by an international, multidisciplinary team of 20 researchers, led by the Desert Research Institute, Reno, Nev. The team determined that the climate-related impacts were caused by eruptions of the Okmok volcano some 6,000 miles away in Alaska.

World map showing Okmok volcano in the Alaskan Aleutian Islands, Rome and Alexandria.
The researchers analyzed volcanic fallout records in six Arctic ice cores from Greenland and Russia. They were able to delineate two distinct eruptions encompassing Caesar’s death in 44 BCE: a powerful, short-lived, relatively localized event in early 45 BCE, and a much larger, more widespread event in early 43 BCE, the fallout from which continued more than two years. The geochemistry of deposited tephra (ejected rock fragments and particles) identified the Okmok volcano as the source.

Members of the team collected corroborating evidence from around the globe, including tree-ring-based climate records from Scandinavia, Austria and California, and climate records from cave formations in China.

The climate proxy records indicated that 43 and 42 BCE were among the coldest years of the recent millennia in the Northern Hemisphere at the start of one of the coldest decades. Modeling also suggested that the high-latitude eruption led to pronounced changes in hydroclimate, including seasonal temperatures in Mediterranean region as much as 7°C (13°F) below normal during the 2 years following the second eruption.

The team matched the scientific findings with written and archaeological descriptions of the eruption’s impact, including the failure of the Nile River to flood and the unrest in the region.

The Okmok volcano caldera in 2013; the summit of the cone formed during the 2008 eruption is eroding and a lake is filling the crater’s bottom (photo by J.R.G. Schaefer, from Alaska Volcano Observatory, Alaska Division of Geological & Geophysical Surveys, avo.alaska.edu/images/image.php?id=54161).
Wrap Up
Many different factors contributed to the fall of the Roman Republic and Ptolemaic Kingdom; however, the climatic effects of the 43 BCE Okmok eruption played an undeniably large role. Identifying and characterizing the volcanic source and eruption fills a knowledge gap that long puzzled archaeologists and historians.

Thanks for stopping by.

Example sources of Roman and Ptolemaic history:

Study of effects of Okmok volcano eruption in Proc. of National Academy of Sciences of USA: www.pnas.org/content/early/2020/06/25/2002722117
Articles on study on EurekAlert! and Science websites:

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