Canadian lake selected as site to mark the start of the Anthropocene

Geologists have selected a lake in Canada as the best site to mark the start of a new epoch dominated by humanity’s influence on Earth, known as the Anthropocene.

The announcement marks a big development in a long-running effort to declare that we have entered a new geological epoch, although there are three more votes before the site can be formally ratified by the International Union of Geological Sciences.

Earth’s current epoch, the Holocene, began when the last glacial period ended around 11,700 years ago. Human civilisation has thrived during this time, but since the middle of the 20^th century, our impact on the planet has grown dramatically – a shift known as the Great Acceleration. Some scientists believe that this event heralds the beginning of a new epoch dominated by humans.

For the past few years, a team of researchers called the Anthropocene Working Group (AWG) has been trying to pinpoint the place on Earth that offers the best geological evidence for the Anthropocene.

“We looked at a very diverse array of natural environmental archives, from a coral reef in Australia to a peat bog in Poland,” says Simon Turner at University College London, secretary of the AWG.

At the International Congress of Stratigraphy in Lille, France, on 11 July, the group announced that Crawford Lake in Ontario, Canada, is their chosen site.

The layers of sediment at the bottom of the lake, which sits in a protected area and remains undisturbed by the outside world, record precise data about the time during which they were deposited.

“Crawford Lake has this annual chronology that has a very nice record of markers that we’ve suggested tie into the Great Acceleration,” says Turner. Sediment cores from the lake show a spike in plutonium-239, the radioactive fallout from nuclear weapons testing, dating back to the early 1950s that coincides with the surge in human activity at the time.

Other sites under consideration included Sihailongwan Lake in China and Beppu Bay in Japan. Ultimately, approval from the Indigenous community in the area and the protected status of the region clinched it for Crawford Lake, says Colin Waters at the University of Leicester, UK, who heads up the AWG.

Not everyone is convinced that the Anthropocene needs to be defined as a geological epoch. “Humans have been impacting natural environments going back about 40,000 years,” says Philip Gibbard at the University of Cambridge. Instead, Gibbard and others propose that we define the Anthropocene as an event. “It’s a broad term that allows us to say in parts of the world human impacts began much earlier than they did elsewhere,” he says.

Crawford Lake will be put forward in a formal proposal later this year as the reference point for the start of the epoch, sometimes called a “golden spike”. Some locations marking boundaries of geological stages are marked with an actual spike driven into a layer of rock.

As part of the proposal, the AWG will need to nail down the exact year the Anthropocene started, which will probably be between 1950 and 1953, says Francine McCarthy at Brock University, Canada, another member of the group.

The proposal must then be accepted in votes by three separate bodies before Crawford Lake can be declared the official location that records the start of the Anthropocene. The AWG hopes that a decision will be made in 2024.

“It is our hope that if the stratigraphic commission draws that line and formalises the time in Earth’s history when the planet has been so impacted by humans, it will hopefully convey a sense of urgency to people to act now to look after our planet,” says McCarthy.