Chicken Bones, Microplastics, H-Bombs, Soot - Picking A Physical Marker To Define The Anthropocene

[hatrack]

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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 team has come up with a shortlist of 12 sites that have now begun a series of votes – but there can be only one winner. Humanity has unquestionably changed the Earth far beyond the stability of the Holocene, the 11,700-year period during which all civilisation arose, and which will end with the declaration of the Anthropocene. The atmosphere, lakes and oceans, and the living world have all been transformed by greenhouse gas emissions, pollution and the destruction of wildlife and ecosystems. Humans also now have a greater effect on shaping the surface of the Earth than natural processes, shifting about 24 times more material than is moved by rivers.

Defining the Anthropocene is vital, researchers say, because it brings together all the impacts of humans on the world, thereby giving a platform for holistic understanding and, hopefully, action to repair the damage. From a scientific perspective, a precise definition is essential for a clear basis for debate. The first stage of voting is already underway. The site will need to show “specific physical properties in sediment layers, or strata, that capture the effects of recent increases in human population; unprecedented industrialisation and globalisation; and changes imposed on the landscape, climate, and biosphere”, according to a recent paper in the journal Science by Leicester University’s Prof Colin Waters and University College London’s Dr Simon Turner, the chair and secretary respectively of the Anthropocene Working Group (AWG).

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But other markers offer the “golden spike” needed for a precise definition and enabling strata to record a sharp, clear rise. Principal among these is the distinctive fingerprint of radioactive isotopes, particularly plutonium, produced by cold war H-bomb tests, the first of which was carried out by the US on 1 November 1952 on the Eniwetok atoll in the Pacific Marshall Islands. Scores of above-ground tests soon followed, with some even rocketed into the stratosphere. The fallout from the tests was fast and global, circling the planet within about 18 months, until atmospheric testing was banned in 1962. “For a short period of time, they tested their new arsenal a lot,” said Turner. “That’s why you have this very unique, time-specific, global marker which is so useful for our work.”

Another useful marker are tiny spheroidal carbonaceous particles (SCPs), a type of tough fly ash only produced by the high-temperature burning of coal or heavy oil. “They take off with the sudden increase in numbers of thermoelectric plants after WW2,” said Turner. “They’re good at travelling on a continental scale and you find them globally because lots of continents produced them.” Work done for the AWG has revealed SCPs in Antarctic ice cores for the first time.

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https://www.theguardian.com/environment/2023/jan/06/h-bombs-chicken-bones-scientists-race-to-define-start-of-the-anthropocene

[NNadir]

1. The word "thermoelectric" in this text is used incorrectly. It's OK. It's a journalist after all.