Radioactive debris from first hydrogen bomb tests mark start of Anthropocene epoch: report
On January 6th, 2023, The Guardian's Environment Editor Damian Carrington reported that researchers around the world were tasked with determining when Earth's current epoch, the Anthropocene, officially began, writing that "an international team of almost 40 scientists, who have been commissioned by the official guardians of the geological timescale, must select a place where layered deposits show the clear transition from the previous age to the new one."
The dividing line between the Anthropocene and its predecessor, the Holocene, in which modern civilization has developed, has never been formally established. This was due to disagreement over what factors matter most and which specific events in human history were significant enough to warrant marking a new phase of terrestrial evolution.
On Tuesday, Carrington revealed that the debate has been resolved, based on debris found in Canada's Crawford Lake.
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"The site is a sinkhole lake in Canada. It hosts annual sediments showing clear spikes due to the colossal impact of humanity on the planet from 1950 onwards, from plutonium from hydrogen bomb tests to the particles from fossil fuel burning that have showered the globe," Carrington wrote. "If the site is approved by the scientists who oversee the geological timescale, the official declaration of the Anthropocene as a new geological epoch will come in August 2024."
The sinkhole — which was selected by the Anthropocene Working Group out of a dozen candidates that were investigated from 2009 to 2016 — sufficiently conveys the "scale and severity of the planetary transformation processes unleashed by industrialized humanity."
The AWB, Carrington noted, "was set up in 2009 and in 2016 concluded that the human-caused changes to Earth were so great that a new geological time unit was justified. The AWG then assessed in detail a dozen sites across the world as candidates for what geologists call a 'golden spike,' ie the place where the abrupt and global changes marking the start of the new age are best recorded in geological strata."
Carrington pointed out that the "climate crisis is the most prominent impact of the Anthropocene, but huge losses of wildlife, the spread of invasive species, and the widespread pollution of the planet with plastics and nitrates are also key features."
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Brock University geology professor and AWG member Francine McCarthy explained that "there is compelling evidence globally of a massive shift, a tipping point, in the Earth's system" and that "Crawford Lake is so special because it allows us to see at annual resolution the changes in Earth history." McCarthy added that "the bottom of the lake is completely isolated from the rest of the planet, except for what gently sinks to the bottom and accumulates in sediment."
Meanwhile, to draw its conclusion, the AWB used "plutonium isotopes from H-bomb tests as the key marker for the Anthropocene, as they were spread globally from 1952 but declined rapidly after the Nuclear Test Ban Treaty in the mid-1960s, creating a spike in sediments," Carrington said.
AWB member and University of Southampton environmental radiochemist professor Andrew Cundy told Carrington that "the presence of plutonium gives us a stark indicator of when humanity became such a dominant force that it could leave a unique global 'fingerprint' on our planet."
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Carrington's full columns continue at this link and here.
