The Sediment of Crawford Lake is Perfect Record of Human's Impact on the Environment for the Last Millenium
The lakebed confirms the existence of a new epoch in geologic time called Anthropocene, or the age of Humans.
Hiya!
You can thank fellow Curious Adventure reader Natalie for today’s topic! I read about it before, but when Natalie brought it back to my attention on Substack’s Notes, it inspired me to write about it. The topic also serendipitously fits into this week’s theme. So, thanks, Natalie!
If you haven’t heard, some scientists were bestowed with incredible luck because they discovered a nondescript Canadian lake that just so happens to hold a perfect record of humanity’s impact on the environment going back at least a thousand years. Wild right? Get ready, because I’m about to tell you all about it.
Anthropocene
First, though, let’s talk a bit about epochs in Earth’s geological history. You know the Age of the Dinosaurs ended when a meteor plummeted into a Tunisian cliff face on Earth. Meanwhile, Holocene is our more recent Age, which encompasses the last 11,700 years and is linked to hydrogen trapped in Greenland’s ancient ice. But, in 2000, atmospheric chemist Paul J. Crutzen and limnologist Eugene F. Stoermer proposed a new epoch beginning in the 1950s called Anthropocene, which comes from the Greek terms for “human and “new.”
Since then, the scientists behind this mission formed a little-known organization named the Anthropocene Working Group (AWG), which has gathered evidence showing that Earth’s climate and chemistry have fundamentally shifted in the last several decades compared to the conditions over the last several thousand years. These shifts, AWG says, are due to human activity and are substantial enough to warrant a new geological epoch.
However, not everyone is convinced.
First, we can’t just decide to mark a new official epoch in Earth’s 4.6 billion-year timeline. There are requirements to meet. The most important of which is known as the “golden spike.” A mark in the geological record that perfectly preserves a specific transformation. In the case of the dinosaurs, we can see the evidence on the cliffsides. For the Holocene era, the golden spike is the hydrogen molecules trapped in Greenland’s ice.
For Anthropocene to become an official epoch, the golden spike must show a record of an incredible human-caused transformation on the planet’s geological record. And considering AWG is suggesting Anthropocene started less than a century ago, some scientists think it’s too soon to declare the new Age officially, especially since the other Ages were named long after they started and with the exception of Holoscene, usually not until after they ended.
Sturt Manning, an archaeologist who directs Cornell University’s tree ring laboratory, said :
“I’m not sure if something that is ephemeral as a couple of decades can count as a new geological age. You can’t really define your own time.”
Another issue comes down to a very particular human conflict we’re struggling with — the struggle to lump us all together. Some argue that the term “Anthropocene” is unfair because it suggests that all humans are to blame for the impacts our species has had on the planet. When the truth — backed by plenty of research — is that the majority of environmental harms are thanks to the planet’s wealthiest countries and individuals.
Technicalities aside, professor at the University of Leicester in Britain, and AWG chair member, Colin Waters argues that even though it’s only been about 70 years since the changes began, the sheer amount of change can’t be ignored. She states:
"Clearly the biology of the planet has changed abruptly. We cannot go back to a Holocene state now."
Now, Waters and other experts believe Crawford Lake in the suburbs of Ontario, Canada, might be the golden spike they’ve needed to officially declare Anthropocene the new epoch.
The Lake
Okay, now for the fun part. I gotta hand it to the Washington Post for this semi-interactive profile about Crawford Lake. In it, they report that locals used to think the lake was bottomless and that anything that fell in “would fall till the end of time.” Yet when scientists finally investigated the lake, it actually measured to be about 79 feet (29 meters) deep and 25,800 square feet (24,000 square meters) wide.
While the lake proved to have a bottom, scientists were astonished by what they discovered there. The lake’s sediment, it turns out, has swallowed and preserved a thousand years’ worth of changes from the planet’s surface. Whatever falls down there doesn’t “fall till the end of time,” but it does remain a marker of its time because debris sinks to the bottom without mixing with the upper layers of water.
As more debris falls to the lake’s floor, they form new layers in the sediment. Analyzing these layers is like reading a record of environmental history — and Crawford Lake contains a thousand years’ worth of history. When scientists evaluated Crawford Lake’s sediment, they discovered it was saturated with the byproducts of human activity — beginning specifically around the mid-20th century, so about the 1950s.
AWG scientists discovered nitrogen from our fertilizers, plutonium isotopes from testing our nuclear bombs, black fly-ash particles from our fossil fuels, and specific patterns in tree pollen that reflect local forests’ responses to rising temperatures, along with more evidence linked to global trade and deforestation.
This level of evidence is an incredible find. An earth scientist at Brock University in Ontario and a member of the AWG, Francine M.G. McCarthy, remarked:
“The record at Crawford Lake is representative of the changes that make the time since the mid-20th century geologically different from before.”
Lake Crawford, then, seems to be an ideal contender as the needed golden spike, but it’s not the only nominee. The lake is actually one of twelve candidates worldwide. The others include ice in Antarctica, a mountaintop peat bog, two remote coral reefs, and a polluted bay in California. All show a surge in human-related pollution activity beginning in the 1950s. The radioactive plutonium from nuclear testing marks a literal line in the sand and the start of a new age.
After months of consideration, the 22 Anthropocene Working Group voting members — including Waters and McCarthy — decided that Crawford Lake contains the best evidence marking our transition into Anthropocene. But that doesn’t make Anthropocene official quite yet.
What’s Next?
According to the Washington Post, AWG’s proposal will be reviewed over the next few months by the Subcommission on Quaternary Stratigraphy, which is responsible for subdividing the last 2.4 million years of history into official stages/periods.
After that, the International Commission on Stratigraphy, which is “the largest and oldest constituent scientific body in the International Union of Geological Sciences,” will vote on it. If all goes well, the proposal will then be formalized at next year’s International Geological Congress in South Korea. And at that point, Anthropocene becomes a for-real, official period in history.
One we’ve barely begun.
In the mere seven decades since it supposedly started, scientists say we, humans, brought about more substantial changes to the planet than it experienced in over seven millennia. As far as we know, no other species has wrecked so much havoc that they’ve altered the global ecosystem — except for us.
McCarthy warns that Lake Crawford is more than a golden spike, “It’s a line in the sand. The Earth itself is playing by a different rule book. And it’s because of us.”
Perspective Shift
The fact that some people still deny that Human activity could create such a measurable impression on the planet baffles me. Yet, I suppose it’s a very human thing to do. We’re contradictory that way. We think we’re the best, most powerful, intelligent, and indestructible species in the Universe. Yet, also that we are insignificant and incapable of creating such an impact on something so seemingly eternal.
I digress.
Regardless of whether we call the evidence in Crawford Lake the beginning of a new epoch or just another geologic event, at the very least, we should pay attention. The lake, along with the contending sites around the globe, provides proof that our species has disrupted the planet’s one-balanced cycles in less than a century. Granted, there was plenty of ignorance and naivety during that time, and it’s okay to make mistakes. What’s not okay is continuing to make those mistakes even after we know better.
So if Anthropocene is, in fact, a new period, the question is, what sort of era will we make it? One of destruction or of healing?
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This just makes me so sad, in the end.