Little lake in Canada is the key marker of a proposed geological epoch: Anthropocene, named for human beings

UPDATE, July 12: The Anthropocene Working Group says it chose Crawford Lake as its representational site because it has "the clearest and most pronounced evidence of humankind’s influence on the global geologic record," The New York Times reports. "Three more committees of geologists will vote on it, a process that could start this fall; 60% of each committee will need to approve the proposal for it to advance to the next one. Ratification by any is far from guaranteed."

An aerial view of Crawford Lake, where sediments hold over
a thousand years of geologic history. (Washington Post photo)

Once considered "bottomless" by locals, a small lake near Milton, Ontario, has a floor of finely detailed sediment layers that show the dramatic change humans have wrought on Earth, so much that it may mark the beginning of a new geological epoch, the Anthropocene, report Sarah Kaplan, Simon Ducroquet, Bonnie Jo Mount, Frank Hulley-Jones and Emily Wright of The Washington Post: in a richly illustrated presentation: "Researchers will determine whether Crawford Lake should be named the official starting point for this geologic chapter, [breaking] from the dependable environment of the past to the uncertain new reality humans have created. . . . In just seven decades, the scientists say, humans have brought about greater changes than they did in more than seven millennia. Never in Earth's history has the world changed this much, this fast. Never has a single species had the capacity to wreak so much damage — or the chance to prevent so much harm."

Scientists begin each epoch, a segment of  geologic time, "with a 'golden spike' — a spot in the geologic record where proof of a global transformation is perfectly preserved," the Post reports. "These spikes are like exclamation points in the story of the planet, punctuating a tale of shifting continents, evolving species and temperatures that rose and fell as carbon levels fluctuated in the atmosphere." Scientists think the golden spike for the Anthropocene Epoch may be Crawford Lake, because of its rare substrate: "No other water body is known to possess this particular combination of attributes, making Crawford Lake a unique bellwether of global change." Two keys: The water at the bottom of the lake doesn't mix with the water above, and the local environment produces a thin layer of calcite that marks every year, going back a millennium.

Radioactive plutonium began to spike in the 1940s with testing
of nuclear explosives. (Research photo, Washington Post graph)

Francine McCarthy, a professor of Earth sciences at Brock University in Ontario, has led the study of sediment layers that show how life has changed on Earth. "Fly ash, a byproduct of burning coal and oil, drifted into the lake from rapidly industrializing cities. Heavy metals like copper and lead increased in the mud," the Post reports. "And then, around 1950, the world reached a tipping point," Head told the Post: "This is when humans essentially overwhelmed the Earth as a functioning system."

From pollution to radioactive remains of nuclear-bomb tests, "The same evidence appears all over the planet, in every potential golden spike site the Anthropocene Working Group has examined," the Post reports. "Peat bogs, ocean basins, the skeletons of coral reefs — even the ice of Antarctica has been permanently tainted by human pollution."

Washington Post map from OpenStreetMap base

"What we have measured, in a very objective and quantitative way, is we are living in a world with conditions that are no longer within the last 11,000 years of natural variability," McCarthy told the Post. "The Earth is, in fact, fundamentally different." The Post reports, "As much as the Anthropocene is a recognition of humanity's culpability, it is also a declaration of human agency, McCarthy believes. Alongside geologic evidence of environmental destruction, Crawford Lake holds proof of people's capacity for repair. She told the Post: "It's not just a doomsday story. It is a 'wake up and smell the coffee' story. It shows we can make meaningful change."