Eruption of Alaska's Okmok volcano linked to period of extreme cold in
ancient Rome
Ice core samples provide new evidence of a massive volcanic eruption in
43 BCE

Date:
June 22, 2020
Source:
Desert Research Institute
Summary:
Scientists and historians have found evidence connecting
an unexplained period of extreme cold in ancient Rome with an
unlikely source: a massive eruption of Alaska's Okmok volcano,
located on the opposite side of the Earth. A new study uses an
analysis of tephra (volcanic ash) found in Arctic ice cores to
link this period of extreme climate in the Mediterranean with the
caldera-forming eruption of Alaska's Okmok volcano in 43 BCE.



FULL STORY ==========================================================================
An international team of scientists and historians has found evidence connecting an unexplained period of extreme cold in ancient Rome with an unlikely source: a massive eruption of Alaska's Okmok volcano, located
on the opposite side of the Earth.


========================================================================== Around the time of Julius Caesar's death in 44 BCE, written sources
describe a period of unusually cold climate, crop failures, famine,
disease, and unrest in the Mediterranean Region -impacts that ultimately contributed to the downfall of the Roman Republic and Ptolemaic Kingdom
of Egypt. Historians have long suspected a volcano to be the cause, but
have been unable to pinpoint where or when such an eruption had occurred,
or how severe it was.

In a new study published this week in Proceedings of the National
Academy of Sciences (PNAS), a research team led by Joe McConnell,
Ph.D. of the Desert Research Institute in Reno, Nev. uses an analysis
of tephra (volcanic ash) found in Arctic ice cores to link the period of unexplained extreme climate in the Mediterranean with the caldera-forming eruption of Alaska's Okmok volcano in 43 BCE.

"To find evidence that a volcano on other side of the earth erupted and effectively contributed to the demise of the Romans and the Egyptians
and the rise of the Roman Empire is fascinating," McConnell said. "It
certainly shows how interconnected the world was even 2,000 years ago."
The discovery was initially made last year in DRI's Ice Core Laboratory,
when McConnell and Swiss researcher Michael Sigl, Ph.D. from the Oeschger Centre for Climate Change Research at the University of Bern happened
upon an unusually well preserved layer of tephra in an ice core sample
and decided to investigate.

New measurements were made on ice cores from Greenland and Russia, some
of which were drilled in the 1990s and archived in the U.S., Denmark,
and Germany.

Using these and earlier measurements, they were able to clearly delineate
two distinct eruptions -- a powerful but short-lived, relatively localized event in early 45 BCE, and a much larger and more widespread event in
early 43 BCE with volcanic fallout that lasted more than two years in
all the ice core records.



==========================================================================
The researchers then conducted a geochemical analysis of the tephra
samples from the second eruption found in the ice, matching the tiny
shards with those of the Okmok II eruption in Alaska -- one of the
largest eruptions of the past 2,500 years.

"The tephra match doesn't get any better," said tephra specialist
Gill Plunkett, Ph.D. from Queen's University Belfast. "We compared
the chemical fingerprint of the tephra found in the ice with tephra
from volcanoes thought to have erupted about that time and it was very
clear that the source of the 43 BCE fallout in the ice was the Okmok II eruption." Working with colleagues from the U.K., Switzerland, Ireland, Germany, Denmark, Alaska, and Yale University in Connecticut, the team
of historians and scientists gathered supporting evidence from around
the globe, including tree- ring-based climate records from Scandinavia,
Austria and California's White Mountains, and climate records from a
speleothem (cave formations) from Shihua Cave in northeast China. They
then used Earth system modeling to develop a more complete understanding
of the timing and magnitude of volcanism during this period and its
effects on climate and history.

According to their findings, the two years following the Okmok II eruption
were some of the coldest in the Northern Hemisphere in the past 2,500
years, and the decade that followed was the fourth coldest. Climate models suggest that seasonally averaged temperatures may have been as much as 7oC (13oF) below normal during the summer and autumn that followed the 43 BCE eruption of Okmok, with summer precipitation of 50 to 120 percent above
normal throughout Southern Europe, and autumn precipitation reaching as
high as 400 percent of normal.

"In the Mediterranean region, these wet and extremely cold conditions
during the agriculturally important spring through autumn seasons probably reduced crop yields and compounded supply problems during the ongoing
political upheavals of the period," said classical archaeologist Andrew
Wilson, D.Phil.

of the University of Oxford. "These findings lend credibility to reports
of cold, famine, food shortage and disease described by ancient sources." "Particularly striking was the severity of the Nile flood failure at
the time of the Okmok eruption, and the famine and disease that was
reported in Egyptian sources," added Yale University historian Joe
Manning, Ph.D. "The climate effects were a severe shock to an already
stressed society at a pivotal moment in history." Volcanic activity
also helps to explain certain unusual atmospheric phenomena that were
described by ancient Mediterranean sources around the time of Caesar's assassination and interpreted as signs or omens -- things like solar
halos, the sun darkening in the sky, or three suns appearing in the sky
(a phenomenon now known as a parahelia, or 'sun dog'). However, many of
these observations took place prior to the eruption of Okmok II in 43 BCE,
and are likely related to a smaller eruption of Mt. Etna in 44 BCE.

Although the study authors acknowledge that many different factors
contributed to the fall of the Roman Republic and Ptolemaic Kingdom,
they believe that the climate effects of the Okmok II eruption played
an undeniably large role -- and that their discovery helps to fill
a knowledge gap about this period of history that has long puzzled archaeologists and ancient historians.

"People have been speculating about this for many years, so it's exciting
to be able to provide some answers," McConnell said.


========================================================================== Story Source: Materials provided by Desert_Research_Institute. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. Joseph R. McConnell et al. Extreme climate after massive eruption of
Alaska's Okmok volcano in 43 BCE and effects on the late
Roman Republic and Ptolemaic Kingdom. PNAS, 2020 DOI:
10.1073/pnas.2002722117 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200622152525.htm

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