Scientists can trace the reach of aboveground nuclear detonations, the first of which was conducted in 1945, by measuring levels of carbon-14—a radioactive isotope of carbon produced when neutrons from nuclear reactions collide with nitrogen atoms in the atmosphere.
 | "Bomb Carbon" Has Been Found in Deep-Ocean Creatures. The detection of this radioactive relic of nuclear weapons tests in a remote environment shows humanity's far-reaching environmental impact getpocket.com |
It would have taken natural oceanic circulation about 1,000 years to carry it to the depths of the Mariana Trench. And in fact, testing for the new study showed that the waters of the trench did have low levels of carbon-14