Pompeii’s 2,000-year-old eruption just gave scientists a better clock for Earth’s past

Nearly 2,000 years ago, Pliny the Younger documented what he witnessed when Mt. Vesuvius erupted, burying Pompeii and killing his uncle, Pliny the Elder. His account did more than preserve the story of one of history's most famous volcanic disasters. It also recorded enough information about when the eruption occurred to give modern scientists an unusually precise historical reference point for testing volcanic dating techniques.

Researchers from the Berkeley Geochronology Center, UC Berkeley and the University of Padua in Italy now report in Science Advances that this historical benchmark has helped them significantly improve the precision of argon-argon dating. By calibrating the method against the inferred eruption date of Aug. 24, 79 CE, they have strengthened what is already one of the most widely useful tools for determining the ages of rocks and volcanic events.