Scientists have identified a geological location they say best reflects a proposed new epoch called the Anthropocene, a major step toward changing the official timeline of Earth's history.
The term Anthropocene, which was first proposed in 2000 to reflect how profoundly human activity has changed the world, has become a common academic word that unites different fields of study, reports N1.
"When eight billion people have an impact on the planet, there are bound to be consequences," said Colin Waters, honorary professor at the University of Leicester's School of Geography, Geology and the Environment, who is also chair of the Anthropocene Working Group.
We have moved into this new state of the Earth and it should be defined by a new geological epoch, Waters added, according to CNN.
AVG, a group currently consisting of 35 geologists, has been working since 2009 to make the Anthropocene part of the Earth's official timeline. In 2016, the group determined that the Anthropocene epoch began around 1950 – the beginning of the era of nuclear weapons testing, the geochemical traces of which can be found around the world. Since then, the researchers have considered 12 sites that could provide the key evidence needed to support their proposal, nine of which have been put to a vote.
On Tuesday, scientists announced a geological site - Crawford Lake in Ontario, Canada - that best demonstrates the geological impact of the Anthropocene, according to their research.
However, not everyone agrees that the Anthropocene is a geological reality or that researchers have enough evidence to officially declare it a new epoch.
A division of deep time
The geologic time scale provides the official framework for our understanding of Earth's 4,5 billion-year history. Geologists divide the history of our planet into eons, eras, periods, epochs, and eras—with an eon being the largest portion of time and an era being the shortest.
For example, we are currently living in the Megalayan Age. It is part of the Holocene epoch, which began at the end of the last ice age 11.700 years ago, when the ice caps and glaciers began to retreat. The Holocene is part of the Quaternary Period, the latest division of the Cenozoic Era, which in turn is part of the Phanerozoic Eon – which spans from 539 million years ago to the present.
These geological chapters are often named after the place where they were first studied. The Jurassic period takes its name from the fossil-rich rocks in France's Jura mountains, while the Cambrian period takes its nickname from the Roman name for Wales.
Andrew Knoll, a professor of natural history at Harvard University, said the scale was "hugely helpful" for his work as a paleontologist.
"When I say 'Cambrian,' this conveys not only the time between 539 and 485 million years, but also a wealth of information about the environment, tectonics, paleogeography and more," Noll said.
That, he adds, is a bit like saying the Middle Ages or the Renaissance.
If approved, the Anthropocene would be the third epoch of the Quaternary period. This would also mean that the Holocene epoch was particularly short, as other epochs lasted several million years.
Each division in the official timeline is also represented by a single geologic locality—known as a Global Boundary Stratotype Section and Point (GSSP), which best represents what is new or unique in a particular chapter in Earth's history.
Each point is usually marked with a "golden spike", often driven into a key layer of rock, although the spot could be a stalagmite or an ice core.
Birthplace of the Anthropocene
For the Anthropocene, the proposed location of the golden spike is sediment found in the bed of Crawford Lake, which reveals geochemical traces of nuclear bomb tests, particularly plutonium - a radioactive element widely detected worldwide in coral reefs, ice cores and peat bogs.
Crawford Lake emerged as the winner after AVG voted on nine candidate sites in three rounds. Other potential sites included a peat bog in Poland's Sudeten Mountains, Searsville Lake in California, a section of seabed in the Baltic Sea, a bay in Japan, a water-filled volcanic crater in China, an ice core drilled from the Antarctic Peninsula, and two coral reefs, one in Australia, and the other in the Gulf of Mexico.
Waters said it was very difficult to choose between the different sites and the votes were close, but he believes Lake Crawford won because the proposed geochemical starting point of the Anthropocene associated with the sediment is particularly precise.
The lake is not large, covering 2,4 hectares, but it is extremely deep, almost 24 meters, and the sediment at the bottom can be divided into annual layers to be sampled for geochemical markers of human activity.
This analysis allows scientists to see changes in annual resolution, explained Francine McCarthy, a professor of earth sciences at Brock University in Canada who has studied the lake.
"The shape (of the lake) limits the mixing of the water column so that the bottom waters do not mix with the surface waters. The bottom of the lake is completely isolated from the rest of the planet, except for what slowly sinks to the bottom," she explained.
Andrew Cundy, professor and chair of environmental radiochemistry at the UK's University of Southampton and member of the AVG, said that "the presence of plutonium gives us a clear indication of when humanity became such a dominant force that it could leave a unique global 'fingerprint' on our planets".
However, the choice of Crawford Lake is not the final decision on whether the Anthropocene is recognized as an official geologic time unit.
Later this summer, the AVG will submit a proposal to make the Anthropocene official to the Subcommission on Quaternary Stratigraphy. If the subcommittee members agree with a 60 percent majority, it will then forward the proposal to the International Commission on Stratigraphy, which will also need to vote and agree with a 60 percent majority for the proposal to proceed to ratification. Both bodies are part of the International Union of Geological Sciences, which represents more than a million geoscientists worldwide.
A final decision is expected at the 37th International Geological Congress in Busan, South Korea, in August 2024.
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