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Scientists have identified the geological site they believe best reflects a proposed new epoch called the Anthropocene – a major step in changing the official timeline of Earth’s history.
The term Anthropocene First proposed in 2000 to represent how profoundly human activities have changed the world, it has become a commonly used academic catchphrase, uniting diverse fields of study.
“If 8 billion people all have an impact on the planet, there is bound to be an impact,” said Colin Waters, honorary professor at the University of Leicester’s Geography, Geology and the Environment School and chair of the Anthropocene Working Group.
“We have entered this new Earth state and it should be defined by a new geological epoch,” Waters added.
The AWG, a group currently made up of 35 geologists, has been working since 2009 to include the Anthropocene in Earth’s official timeline. The group noted in 2016 that the Anthropocene epoch began around 1950 – the beginning of the nuclear weapons testing era, geochemical traces of which can be found around the world. Since then, the researchers have considered twelve sites that could provide the crucial evidence to support their proposal, nine of which have been put to the vote.
On Tuesday, the scientists announced that their research found the geological site — Crawford Lake in Ontario, Canada — to best reflect the geological impact of the Anthropocene.
However, not everyone agrees that the Anthropocene is a geological reality — or that researchers have enough evidence to officially declare it a new epoch.
The geologic time scale provides the official framework for our understanding of Earth’s 4.5 billion year history. Geologists divide our planet’s history into eons, ages, periods, epochs, and ages – with an eon being the longest and an age the shortest.
For example, we are currently living in the Meghalaya age. It is part of the Holocene, which began at the end of the last Ice Age 11,700 years ago when ice caps and glaciers began retreating. The Holocene is part of the Quaternary, the youngest division of the Cenozoic, which in turn is part of the Phanerozoic – which stretches from 539 million years ago to the present.
By James St. John/Flickr
This is a global stratotype segment – or golden spike – in the Flinders Ranges of South Australia that marks the beginning of the Ediacaran Period, which began 635 million years ago.
These geological chapters are often named after the place where they were first studied. The Jurassic period is named after fossil-rich rocks in the French Jura Mountains, while the Cambrian period takes its name from the Roman name for Wales.
Andrew Knoll, Fisher professor of natural history at Harvard University, said the scale is “extremely helpful” for his work as a paleontologist.
“When I say ‘Cambrian,’ I mean not only between 539 and 485 million years, but also a wealth of information about the biota, environment, tectonics, paleogeography and more,” Knoll said. “[It’s]a bit like talking about the Middle Ages or the Renaissance.”
If approved, the Anthropocene would be the third epoch of the Quaternary. It would also mean that the Holocene was particularly short – other epochs lasted several million years.
Each section in the official timeline is Also represented by a single geologic site—known as the Global Boundary Stratotype Section and Point (GSSP)—that best captures what is novel or unique about a particular chapter in Earth’s history.
Each point is usually marked with a ‘golden spike’, which is often hammered into the central stratum of rock – although the spot could also be a stalagmite or core of ice.
For the Anthropocene, the proposed Golden Spike location is sediment cores from the bottom of Crawford Lake, revealing the geochemical traces of atomic bomb testing, particularly plutonium – a radioactive element widely distributed in coral reefs, ice cores and peat bogs worldwide.
Courtesy of the University of Southampton
Researchers have confirmed that annual sediment sampling from the Crawford Lake site has uncovered geochemical evidence from atomic bomb testing.
Crawford Lake emerged victorious after AWG voted in three rounds on the nine candidate sites. Other potential sites included a peat bog in Poland’s Sudeten Mountains, Searsville Lake in California, a stretch 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 Crawford Lake won because the proposed Anthropocene geochemical starting point associated with the sediment was particularly precise.
The lake is not large, at 2.4 hectares (5.9 acres), but it is exceptionally deep, nearly 24 meters (78.7 ft), and the sediment found at the bottom can be broken down into annual layers that can be examined for geochemical markers of human origin activity. This analysis allows scientists to see changes with annual resolution, explained Francine McCarthy, a professor of geosciences at Brock University in Canada who has been studying the lake.
“The shape (of the lake) restricts the mixing of the water column so that the groundwater does not mix with the surface water. The bottom of the lake is completely isolated from the rest of the planet except for what gently sinks to the bottom,” she explained.
Andrew Cundy, Professor and Chair of Environmental Radiochemistry at the University of Southampton in the UK and a member of the AWG, said: “The presence of plutonium gives us a clear indication of when humanity became such a dominant force that it created a unique global ‘fingerprint’. could leave behind.’ ‘ on our planet.
However, the selection of Crawford Lake is not the final decision on whether to accept the Anthropocene as an official geological unit of time.
The AWG will present a proposal to the Subcommission on Quaternary Stratigraphy later this summer to make the Anthropocene official. If the members of the sub-commission agree with a 60% majority, the proposal is forwarded to the International Commission on Stratigraphy, which must also vote and approve by a 60% majority in order for the proposal to be forwarded for ratification. Both bodies are part of the International Union of Geological Sciences, which represents more than 1 million geoscientists worldwide.
A final decision is expected at the 37th International Geological Congress in August 2024 in Busan, South Korea.
Some experts do not believe that the Anthropocene will reach the level of epoch determination.
Stan Finney, secretary-general of the International Union of Geological Sciences and a professor in the Department of Geology at California State University Long Beach, said the stratigraphic record of the Anthropocene is relatively slim — barely a human lifespan — given a suggested starting point around 1950.
The beginning of the Anthropocene could be defined in many different ways – including the Industrial Revolution – leading to a much longer timeframe than currently thought, he noted.
Courtesy of the University of Southampton
The alpha spectrometry output displayed on screen indicates the presence of plutonium in a Crawford Lake drill core sample.
“There is no doubt that humans have dramatically impacted the Earth system and we are facing incredible consequences today. But it’s a protracted[phenomenon],” he said.
He also believes that the push to officially recognize the Anthropocene may actually be more political than driven by local geology. The term was coined in 2000 not by a geologist but by the late atmospheric chemist and Nobel laureate Paul Crutzen – apparently in a spontaneous remark at a conference.
Finney said it’s more accurate to describe humanity’s profound impact on Earth as an ongoing geological event, rather than a formal epoch with a precise global start date. It’s also possible, he said, that stratigraphers are concluding that the Anthropocene is not epoch-level, but that it may be the fourth epoch of the Holocene — the much less memorable Crawford epoch.
Others dismiss the term Anthropocene because it involves all of humanity in the activity that has irrevocably changed the planet. Some researcher say that the changes are the work of a powerful and elite minority and that the epoch should better be called the Capitalocene.
Waters believes the AWG has strong arguments for formalizing the Anthropocene, but said naming a new geological epoch is “a very conservative process,” so there’s no guarantee the proposal will succeed.
In addition to Crawford Lake, AWG must also select two secondary sites before submitting a proposal.
“We were very careful in our search for suitable sites, but in the end they could just say, ‘We are not impressed by the evidence you have presented to show that the Anthropocene is legitimately a new epoch.'” “Geological time,” Waters said.
“They may also support the idea that there is a phase here and that the Crawford site represents a new phase of the Holocene, but they are unwilling to accept that the Anthropocene is a significant shift that transcends the boundaries of change that.” we see within the Holocene.” ,” he added.
Andrew Mathews, a professor of anthropology at the University of California, Santa Cruz, said the term “Anthropocene” has already shown its meaning and opened up conversations in the natural sciences, social sciences, and humanities. So, ultimately, the exact geological birthplace of the proposed epoch may not be that important.
“It is firmly established that human societies have a geological impact on the world and Earth systems. And that part is helpful,” he said. “It’s basically, ‘Look, we’re right in the middle. “We changed the world and we have to keep thinking about that,” he said.