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Thanks to the destruction of Pompeii by the volcanic eruption of Mount Vesuvius almost two millennia ago, archaeologists now have access to the most versatile and precise volcanic eruption dating method ever created.
In a recent paper published in Science Advances, researchers at the Berkeley Geochronology Center, UC Berkeley, and the University of Padua showed how they inferred an exact event date from the writings of Pliny the Younger and then used it to calibrate an argon-argon dating system.
Details from Pliny the Younger’s eyewitness account allowed the team to settle on August 24, 79 CE as the exact date of the event that took the life of the scribe’s uncle, Pliny the Elder. With this new benchmark, scientists can date ancient volcanic eruptions more accurately, providing new insights into the human past and how these deadly events unfold.
The Volcanic Past
Today, locations such as Yogyakarta, Naples, and Mexico City still face lingering threats from past volcanic eruptions. More accurate dating of those past eruptions will help scientists mitigate modern safety threats to these dense urban areas. Additionally, it will improve other common dating methods such as carbon-14 and uranium-lead, providing more accurate dates for Earth’s ancient creatures and earliest rocks.
“If you want to put together the eruptive history of a volcano in relatively recent time, precision and accuracy really count,” said study leader Paul Renne, a Berkeley professor in residence of earth and planetary science and director of the independent Berkeley Geochronology Center. “The study shows that you can achieve that kind of highly useful precision and accuracy in the historical realm.”
The argon-argon method is based on the decay of potassium-40 into argon-40, which typically only happens after a volcanic eruption.
Improving Dating Results
The work builds on Renne’s previous work on meteor impact and volcanic dating, also using argon-argon dating. By increasing the precision of those dates, his work provided new support for the idea that, within brief periods of 10s of thousands of years, roughly 66 million years ago, the Earth was bombarded with a high rate of meteor impacts that increased volcanic activity. This painted a more complex picture of how the dinosaurs went extinct, rather than by a single impact event alone.
Graduate student Caroline Hasler led the historical research portion of the work, which involved narrowing the date by researching a coin found at the site, which some historians had suggested was not minted until September of that year, but Hasler disagreed.
The team’s research benefited from access to better mass spectrometers, new neutron irradiation techniques, and better samples than Renne’s early 1997 work. Because potassium tends to sit at the top of magma chambers while heavier elements like iron and magnesium sink to the bottom, potassium-rich magma spews out first. It ends up at the bottom of volcanic deposits. These new potassium-rich samples have long been shelved, awaiting analysis.
“It was really just a combination of better samples, instrumental advantage, and a more concerted effort. All of those things came together,” Renne added.
Better Volcanic Analysis
To understand the new work, it helps to separate accuracy from precision. Accuracy measures how correct an answer is, while precision measures how reliable and repeatable a process is. When the team tested their recalibrated argon-argon method for dating volcanic eruptions on eight samples and compared the results to the known dates, they found 0.4% accuracy and 0.7% precision.
“This lets us more precisely infer causality between events in the geologic record, for example, a meteor impact structure and a mass extinction,” Renne said.
One major outcome of the research was revising the half-life decay of potassium-40 to argon-40 from the original value calculated with nuclear physics to a new one that is twice as precise.
Renne says that the work will allow comparisons to other forms of dating, which can then be recalibrated based on his team’s advances with argon-argon.
“We’re hoping to really unify as many geologic dating methods as we can by using the same mathematics, the same Bayesian approach, and just bringing more data, more raw observations into that mix,” Renne concluded. “But argon-argon dating is always going to be a standard — it’s going to be an important calibrant in that sense.”
The paper, “Pliny the Younger Advances Geochronology,” appeared in Science Advances on September 25, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.