Gabon
Sand Origin
Libreville
Random Sand Fact
Almost two billion years ago, a nuclear reactor started by itself inside sandstone in Gabon.
At Oklo, uranium had accumulated and become concentrated within porous sandstone. When groundwater entered the spaces between the grains, the water slowed the neutrons enough for a self-sustaining nuclear chain reaction to begin.
The reactor probably switched on and off as the water boiled away and later seeped back in. This continued for hundreds of thousands of years.
By the time scientists discovered it in the 1970s, nature had already built and run its own nuclear reactor long before humans did.
