2023-07-12 12:41:47
The official marker of the beginning of a new epoch of the Anthropocene is a small, deep Canadian lake whose sediments have collected rthese chemicals from the radioactive fallout from nuclear bombs and other forms of environmental degradation. This has been proposed by an international team of researchers. who has spent 14 years debating when and how humanity began to alter the planet.
He Working Group on the Anthropocene announced the nomination of Lake Crawford this week at a conference of the International Commission on Stratigraphy (ICS), held in Lille, France. Three geological organizations must approve the election for it to become the official marker.
Some geologists have long argued that we live in the Anthropocene, a new geological epoch in which the human activity it has become the dominant influence on the planet’s climate and environment, especially since the middle of the last century.
The concept has important implications for the way we view our impact on the planet. But there is disagreement in the scientific community about when the Anthropocene began, how it was evidenced, and whether human influence has been substantial enough to constitute a new geological age, which typically spans millions of years. To help answer these questions, ICS created the Anthropocene Working Group.
Year after year, the particles go to the bottom of the lake and form layers of sediment that record environmental conditions in a similar way to tree rings.
The ‘golden nail’ of the beginning of the Anthropocene
If the proposal is approved, a sediment core from Crawford Lake would become the ‘golden spike’, marking the start of the Anthropocene. Year after year, the particles are deposited in the lake and end up at its bottom, forming sediment layers that record environmental conditions in a similar way to tree rings.
Embedded contaminants include specks of fly ash from burning fossil fuels and remnants of radioactive plutonium from nuclear bomb tests.
Among the embedded contaminants are specks of fly ash—remnants of burning fossil fuels—and traces of radioactive plutonium, from atmospheric testing with nuclear bombs.
“We have the key markers for the Anthropocene – in Crawford Lake they line up perfectly,” he says. Francine McCarthya micropaleontologist at Brock University in St Catharines (Canada), who leads the team studying the lake.
The Patterson Lab team collects cores from the deepest part of Crawford Lake. / Brock University
The team has collected samples from various environments around the world, from coral reefs to ice sheets, which have been analyzed at the GAU-Radioanalytical Laboratories at the University of Southampton (UK). There, the researchers processed the samples to detect a key marker of human influence on the environment: presence of plutonio.
The team has collected samples from various environments around the world, from coral reefs to ice sheets.
Andrew CundyProfessor of Environmental Radiochemistry at the University of Southampton and member of the Anthropocene Working Group, explains: “The presence of plutonium offers us a crude indicator of when humanity became such a dominant force that it was able to leave a ‘fingerprint’ ‘ unique global on our planet”.
First tests with hydrogen bombs
“In nature, plutonium is only present in trace amounts. But in the early 1950s, when the first tests with hydrogen bombs were carried out, there was a unprecedented rise in plutonium levels in samples from around the world. Starting in the mid-1960s, when the Nuclear Test Ban Treaty went into effect, there was a decline,” Cundy explains.
The presence of plutonium offers a crude indicator of when humanity became such a dominant force that it was able to leave a unique global ‘fingerprint’ on the planet.
The Great Acceleration
Other geological indicators of human activity are high levels of ash from coal power plantsthe high concentrations of heavy metalssuch as lead, and the presence of plastic fibers and fragments. All this coincides with the big acceleration (or Anthropocene), a dramatic increase in human activities, from transportation to energy use, that began in the mid-20th century and continues today.
Of the hundreds of samples analysed, the Crawford Lake core has been proposed as the one Global Boundary Stratrotype (or ‘golden nail’) point, along with other secondary deposits showing similar high-resolution records of human impact. The evidence of the deposits will now be presented to the ICS, which next year will decide whether to ratify the Anthropocene as a new geological epoch.
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