The ancient catastrophe that destroyed Pompeii unexpectedly became a reference point for measuring time in the planet's deep geological record. Scientists used the precisely known date of the eruption of Vesuvius in 79 AD to significantly improve the accuracy of the argon-argon dating method.
The method is based on the decay of potassium-40 into argon-40 within volcanic minerals such as sanidine. Samples from the pumice ejected by the volcano were irradiated with neutrons, and then the ratio of argon isotopes was compared. The historical records of Pliny the Younger made it possible to independently establish the age of the rocks to within a few months, which turned them into a natural standard for calibration.
In a new study published in Science Advances, a group from the Berkeley Geochronology Center and the University of Padua analyzed eight sanidine samples. The result showed an age of 1938 ± 13 years at the time of measurement in 2025, with a real age of about 1946 years. This corresponds to a precision of 0,7 percent and an accuracy of 0,4 percent — a level previously unattainable for such young rocks.
The calibration made it possible to refine the value of the potassium-40 decay constant by a factor of two. Now the method works more reliably not only for recent events, but also for determining the age of ancient eruptions, meteorite craters, and the boundaries of mass extinctions. The improvement helps to establish more precisely the cause-and-effect relationships between geological phenomena separated by millions of years.
As in the old saying, a precise instrument turns scattered facts into a coherent picture. Here a historical tragedy serves as a kind of ruler against which the clocks of the entire planet are checked, making visible processes hidden in the strata of rock.
Thus, a single eruption described nearly two thousand years ago continues to influence our understanding of Earth's history, opening new possibilities for precise chronologies in the Earth sciences.
