23/10/2026
Around 2 billion years ago, uranium deposits at Oklo in Gabon became the site of naturally occurring nuclear fission reactions. Scientists discovered evidence of this extraordinary phenomenon in the 1970s while studying uranium samples.
Groundwater helped slow neutrons, allowing fission to continue under the right geological conditions. The reactions operated in separate zones within the rock and are believed to have occurred intermittently over long periods.
It is one of the rarest discoveries in geology: evidence that nature once created its own nuclear reactors deep underground.