At first glance, it looks like one of Canada’s many lakes. However, researchers have now chosen Crawford Lake as the landmark site where the dawn of a new, human-influenced geological era, the so-called Anthropocene, can best be documented.
The international Anthropocene research group and the Max Planck Society announced their decision on Tuesday in Berlin. This was another step towards official scientific recognition of the Anthropocene.
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Researchers date the start of this new geological era to the mid-20th century. Officially, humans are still living in the Holocene geological era, which began about 11,700 years ago. However, humanity has changed the Earth system so much that, according to the Anthropocene research group, a new geological era has begun.
However, for official recognition, which is by no means considered justified by all scientists, clear scientific evidence is needed and, above all, a concrete point of reference for the new era. This has already been found in Crawford Lake in the Canadian province of Ontario.
The lake’s sediments bear witness to human influence. © AFP/PETER POWER
“The lake is very deep for its size of 24 meters,” said geoscientist Francine McCarthy of Brock University in Ontario. Its correspondingly calm deep waters allow undisturbed sediment deposition. The annual sediment layers are particularly easy to distinguish and thus form a stable geological archive. For example, ash from burning oil and coal, as well as heavy metals and microplastics in the layers are evidence of human influence.
In 2002, the theory of an Anthropocene was presented
Dutch Nobel laureate in chemistry, Paul Crutzen, who put forward the theory of an Anthropocene in 2002, suggested that the new geological age should be linked to humanity’s greenhouse gas emissions since the invention of the steam engine. However, the Anthropocene research group decided on a different marker.
Indeed, traces of the burning of fossil fuels can be found in the soil, said working group chairman Colin Waters of the British University of Leicester. However, this is only the case locally, especially in Europe. “You wouldn’t find anything in Australia,” Waters said. This would lose the criterion of a new age global verifiability.
The researchers therefore decided on plutonium isotopes from above-ground nuclear weapons tests, which took place from 1945 onwards, as the most reliable marker. Plutonium has been found in Crawford Lake since the late 1940s, with a rapid increase starting in the 1950s.
This sediment section shows the different years of sediment deposition. © AFP/PETER POWER
Since the US first tested a giant hydrogen bomb on an atoll in the Marshall Islands in 1952, this year can be defined as the beginning of the Anthropocene, Andy Cundy, a member of the study group at the University of Southampton, told AFP. Previous nuclear tests would have left their mark only regionally.
According to the Max Planck Society, the decision in favor of Crawford Lake must now go through greater coordination between experts. With due approval, the specialized society International Union of Geological Sciences (IUGS) could therefore ratify Crawford Lake in August 2024 for the Anthropocene as a geological reference point, in technical jargon Global Stratotype Section and Point (GSSP).
For the general secretary of the IUGS, Stanley Finney, this is far from being resolved. “The working group vote is a routine step at the lowest level,” he told AFP. The working group must present its choice to the International Stratigraphic Commission, and it will then be verified by independent scientists in the so-called peer review process.
The researchers are carving out frozen layers of lake sediment on the outside of the probe, which was retrieved from the depths of the lake. © AFP/PETER POWER
If Crawford Lake is confirmed, the lake in Canada would be marked with a golden plaque, known as the Golden Spike, as the landmarks of previous geological eras.
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The decision for Crawford Lake to be created by the Anthropocene Research Group in 2009 was made after years of consideration. A total of twelve locations on Earth were selected, including coral reefs and ice cores.
Cundy, a member of the working group, is in no doubt that a new geological era began decades ago. “The data show a clear shift since the mid-20th century that is pushing the Earth system beyond Holocene boundaries,” he told AFP. (AFP)