It would be a huge breakthrough. It is an important event, when the time comes, we can say that we are in a new era. It’s an era that we – as a species – have caused,” Associate Professor Henrik Hovland Svensen from the University of Oslo tells Dagbladet.
Leftover plutonium from nuclear tests and fly ash from coal-fired power plants are not something you want in your local lake.
But it’s the results of these things—along with other telltale signs of the effects of industrial pollution, rising temperatures, and loss of species diversity—that have Canada’s Lake Crawford in Milton, Ontario making headlines around the world.
A group of researchers believes the lake proves a 23-year-old hypothesis that has divided experts for several years:
Humanity has left such geological traces on the globe that it can no longer be said that we are in the geological age Holocene – Which according to current geological chronology began 11 70 years ago – but in the “Age of Man”, Anthropocene.
– very promising
Since 2009, researchers in the Anthropocene Working Group (AWG) have been working to verify whether the Anthropocene – which according to them began in 1950 – meets the criteria to be classified as a separate geological epoch.
Now they think the answer is yes — and geologist Svensen is optimistic on their behalf.
– The reason it is so promising is that the Canadian lake is of a special kind – which we also have in Norway, he says – and at the same time reminds us that the work has not yet been reviewed or published.
Lake Crawford is the so-called Merometic LakeSvensen explains.
– There are lakes where there is no circulation in spring and autumn, so the water bed is quite flat. Then minerals and salts accumulate – and the bottom waters are low in oxygen. As silt is deposited at the bottom of the lake, it settles into very elaborate layers called varves.
He explains that the lack of oxygen in bottom waters prevents benthic organisms from “rooting” in the bottom mud.
This combination of properties causes layers upon layers of mud to settle on the sea floor like the annual rings of a tree trunk.
– If you knock on a tube at the bottom, and then it goes up, you can see these layers. Light and dark layer correspond to one year, depending on the lake. Then you can simply count back in time, he says.
That’s what the researchers at AWG did, according to Svensen.
They counted by time, and then measured the plutonium content of the atomic bombs—and many other things—in each layer. Then they can tell exactly what year the plutonium can be traced back to.
The plutonium in these layers is uniquely suited as a property of the Anthropocene because nuclear tests caused the radioactive element to travel across the globe through the atmosphere.
– When it spreads around the world, it is a global transformation. The diffusion of plutonium through the atmosphere occurred simultaneously around the globe.
Concept AnthropoceneIn its modern sense, it was popularized by Dutch chemist Paul Josef Cruetzen in the year 2000.
But what does it really matter if we live in it Anthropocene or Holocene?
What geologists do is compare the Anthropocene to the rapid climate changes and mass extinctions that have occurred on Earth in the past, says Svensen.
The geologist insists that to find geological changes on the same scale as those that occurred during the Anthropocene – that is, since 1950 – we have to go back millions of years.
The most frequently used comparison, according to Svensen, is Permian-Triassic extinction – the largest mass extinction in the history of the planet – 252 million years ago.
In this period, more than 95 percent of species in the sea and 70 percent of species on land died, according to Encyclopedia Britannica.
– The Anthropocene is at this level – approx. Officially, we’re not there yet. But we have to compare the dramatic changes we saw earlier in geological history.
– Nobody knows where it ends
75 years is a short period in a geological context, Svenssen stresses.
But he stresses that the geological changes that occurred in this short time could end up being on the same order of magnitude as those that occurred millions of years ago.
The Anthropocene debate cuts across almost every academic discipline, according to the geologist.
– It’s about nature, people and the human footprint. Above all, it is about politics. It meddles with spatial planning, concerns about climate change — and how we deal with the upcoming “sixth mass extinction.”
The term “sixth mass extinction” is used by some for rapid man-made biodiversity loss today — and by others for a scenario where this gets worse in the future, according to Large Norwegian Encyclopedia.
— and no one knows where the Anthropocene will end up — in terms of potential mass extinctions, says Svensen.
He also believes that knowledge of the Anthropocene will go into the reports that form part of the decision-making basis for major international political decisions – such as the UN’s climate reports.
A lot changed once the word Anthropocene was introduced 23 years ago. It has created long-standing debates and makes us see the Earth in a whole new way. The fact that it can be documented, both geologically and geochemically, is absolutely essential.
But to declare a geological era, experts need a “golden nail”.
Golden nail – or one “Stratification Division of Global Boundaries and Points”as it is called in technical language – is an internationally recognized reference point that marks the starting point of a phase on the geological time scale.
In this case: a physical location indicating the transition from one era to another.
– The golden nail is a reference point – sort of Type the area – to which all other sites can be compared. In a way, it becomes the standard for the respective period.
When such a reference point is approved by the International Commission of Stratigraphy, it is marked by hammering a golden nail (hence the name) into the ground, rock face, or wherever the point may be.
This is what AWG researchers think they have discovered at Lake Crawford.
Svensen thinks they could easily drive the golden nail all the way to Norway – for example at Sagtjernt in Elverum or other Merometic lakes, where Norwegian researchers are studying the lake floor.
– I would like to think that he could have been a good candidate, he says.
However, this may require different methods than those used by the Norwegian researchers doing research at Sagtjernet.
– The bottom of the lake is very smooth, and the upper centimeters contain a lot of water. It is easy to spoil the layers when you receive it. Then we can’t study the last twenty to thirty years, he says.
The AWG researchers used a proprietary method where sediment and water are frozen – so they can be recovered without “spoiling” them.
– There are very few studies of this kind in Norway, and we tend to focus on time periods further back than the Anthropocene. But they probably would have found a golden nail here, because we have quite a few dumping lakes in Norway.
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