The Anthropocene: Defining a New Geological Epoch

For over a decade, the scientific community has debated a monumental question: Have humans altered the Earth so fundamentally that we have created a new geological epoch? This proposed epoch is known as the Anthropocene. Recently, this debate centered on a small body of water in Ontario, Canada, called Crawford Lake. Geologists examined whether the sediment layers in this lake provide the definitive proof needed to officially close the chapter on the Holocene and declare the start of the “Human Age.”

The Case for Crawford Lake

To define a new geological epoch, scientists look for a “Golden Spike.” This is technically known as a Global Boundary Stratotype Section and Point (GSSP). It serves as a physical reference point in the rock or sediment record that shows a global, synchronous change.

After years of analysis, the Anthropocene Working Group (AWG) selected Crawford Lake as their primary candidate for this Golden Spike. Located near Milton, Ontario, this lake is distinct because it is meromictic. This means the surface and deep waters do not mix. As a result, materials that sink to the bottom are preserved in undisturbed layers, creating a perfect annual record similar to tree rings.

Inside these layers, scientists found clear evidence of human activity starting around 1950. The specific markers include:

• Plutonium-239: Radioactive isotopes resulting from hydrogen bomb testing in the mid-20th century.
• Fly Ash: Residue from burning coal at high temperatures.
• Microplastics: Synthetic particles that do not occur naturally.

The AWG argued that the sharp increase in these materials marks the “Great Acceleration,” a period of rapid industrial growth and population expansion following World War II.

The Voting Process and the SQS Decision

The proposal to ratify the Anthropocene is a rigorous bureaucratic process. It is not enough for the AWG to agree; they must convince the upper echelons of the International Union of Geological Sciences (IUGS). The first major hurdle was a vote by the Subcommission on Quaternary Stratigraphy (SQS).

In March 2024, the results of this critical vote were finalized. The SQS voted to reject the proposal to define the Anthropocene as a formal epoch starting in 1950.

Why Was the Proposal Rejected?

The rejection does not mean geologists deny human impact on the planet. Virtually all scientists involved agree that humanity is a geological force. However, the disagreement lies in how that impact is categorized in the Geologic Time Scale.

Opponents of the formal definition raised several key arguments:

1. Too Recent: Geological epochs typically span millions or thousands of years. Defining a new epoch based on only 74 years (since 1950) seemed premature to many stratigraphers.
2. Too Narrow: Restricting the Anthropocene to the mid-20th century ignores thousands of years of human alteration. Agriculture, deforestation, and early mining began altering the planet long before the atomic bomb.
3. An Ongoing Event: Critics argued that the Anthropocene is better described as an ongoing geological “event” rather than a distinct time unit like the Jurassic or the Pleistocene. An event can be transformative and long-lasting without requiring a single, rigid start date.

Where Does This Leave the Geologic Time Scale?

Because the vote failed, we officially remain in the Holocene Epoch. specifically, we are in the Meghalayan Age, which began 4,200 years ago.

Despite the rejection, the term “Anthropocene” is unlikely to disappear. It has become a standard term in anthropology, history, and environmental science to describe the current era of human dominance. The vote simply means it will not appear on the official International Chronostratigraphic Chart used in textbooks to divide deep time.

The Evidence of a Changed Planet

Whether or not the label is official, the physical evidence found in Crawford Lake and other sites worldwide remains undeniable. The “technofossils” created by modern civilization will survive in the rock record for millions of years.

Technofossils and Geochemical Signals

Future geologists looking back at our current strata will find a distinct layer unlike any before it. This layer is defined by materials that never existed prior to human evolution.

• Concrete: We have produced enough concrete to cover the entire Earth in a layer two millimeters thick. This creates a unique rock formation often referred to as “plastiglomerate” when mixed with plastics.
• Aluminum: Pure aluminum is rare in nature. The massive quantities used in construction and packaging provide a clear signal of technological civilization.
• Carbon Isotope Anomalies: The burning of fossil fuels has altered the ratio of carbon isotopes in the atmosphere and oceans. This chemical signature is etched into limestone, coral, and tree rings globally.
• Biotic Homogenization: Through farming and the transport of invasive species, humans have radically altered the distribution of life. The bones of broiler chickens, now the most common bird on the planet by mass, are a likely future fossil marker of our time.

Conclusion

The vote on Crawford Lake was a pivotal moment in stratigraphy. While the official proposal was turned down, the investigation into the lake provided the world with a high-resolution look at exactly how quickly humans transformed the Earth in the mid-20th century. We may still technically be in the Holocene, but the data from Crawford Lake proves that the Earth system is operating in a way that is profoundly different from the past.

Frequently Asked Questions

What is the Anthropocene? The Anthropocene is a proposed geological epoch dating from the commencement of significant human impact on Earth’s geology and ecosystems.

Why is Crawford Lake important? Crawford Lake in Ontario, Canada, was chosen as the “Golden Spike” candidate because its undisturbed sediment layers provide a perfect record of human impact, specifically showing radioactive plutonium from the 1950s.

Did the geologists vote to make the Anthropocene official? No. In March 2024, the Subcommission on Quaternary Stratigraphy voted against the proposal. Consequently, the Anthropocene is not currently an official unit of the Geologic Time Scale.

What epoch are we currently in? Officially, we are in the Holocene Epoch. This epoch began approximately 11,700 years ago after the last major ice age.

What is the Great Acceleration? The Great Acceleration refers to the period starting around 1950 when human population, economic activity, and resource consumption spiked dramatically. This period is associated with the proposed start date of the Anthropocene.