In its 4.5 billion years of existence, Planet Earth has seen a lot of change. Oceans have formed. Continents have shifted. There’s been ice ages, meteorite strikes and mass extinctions, and life on our little blue planet has evolved enormously.
We know this because Earth’s history has been mapped out on the geological time scale, with each onset of significant planetary changes divided into epochs. We’ve been in the current (official) epoch for over 11,000 years, but experts now believe we’re at the dawn of a new one: The Anthropocene, this time marked by the scale of modern humanity’s impact on the planet.
However, officially declaring the emergence of a new epoch requires substantial geological evidence. That’s why over the past three years, the Anthropocene Working Group (AWG) has been searching across the world for signs that human activity has left a global and long-lasting geological mark on Earth.
Last week they revealed that a lake in Canada could hold the answers. AWG states that:
“The Crawford Lake core tells a story of anthropogenic impacts from Indigenous settlements in the thirteenth to fifteenth centuries, through settler-colonial communities from the mid-nineteenth century, to post-industrial global events beginning in the mid-twentieth century.”
This lake has been proposed by AWG as the candidate site to define the beginning of a new Earth epoch dominated by humans.
Welcome to the Anthropocene, Earth's new chapter.
A million years from now, will Earth's layered rocks and sediment reveal a human signature distinctive enough to mark a clear geological boundary? Yes, say scientists, and the threshold for the "epoch of humans" is likely to be… pic.twitter.com/4kkdJ5B0CP
— AFP News Agency (@AFP) July 10, 2023
What is an epoch?
Britannica defines an epoch as a “unit of geological time during which a rock series is deposited.”
It’s a subdivision of the geological time scale (which is comprised of eons, eras, periods, epochs and ages, in descending order), and its boundaries are generally determined by observing changes in Earth’s rock layers. To constitute a new epoch in the geological record, these changes must be global and long-lasting, indicating planetary-scale changes.
In order to formally define a new Earth epoch, scientists look for geological evidence of global-scale change known as Global Stratotype Section and Points (GSSPs) or “golden spikes” across the planet’s surface. Crawford Lake is the candidate GSSP site AWG has selected to represent the start of the Anthropocene.
What have past epochs looked like?
In the past, the beginnings or endings of epochs are thought to have coincided with the start/end of ice ages; changes in ecosystems and biodiversity; intense global warming events; and even mass extinctions, among many other events.
For example, according to Britannica:
- The beginning of the Eocene epoch (which began 56 million years ago) was marked by the appearance of two new groups of terrestrial animals the perissodactyls (e.g., horses, rhinos and tapirs) and the artiodactyls (e.g., deer, cattle and sheep). Many other modern animals appeared and diversified during this epoch.
- The end of the Pleistocene epoch (which preceded our current official epoch) was marked by the extinction event of many large mammals (e.g., mammoths and ground sloths). This epoch saw many glacial and interglacial climatic cycles, and the extinction event is thought to have been caused by either “abrupt” changes in climate and vegetation as the last ice age ended or overhunting by humans.
- And the Holocene epoch (the most recent official epoch in Earth’s history), which has lasted for about the last 11,700 years, was marked by the onset of a warmer climate where flora and fauna have flourished – including humanity.
However, for a while now experts have proposed the idea that the Holocene may have ended, and we may in fact already be living in a new “human dominated” epoch – the Anthropocene.
What is the Anthropocene?
The “Anthropocene” was first coined by Eugene Stoermer in the late 1980s, and later popularised by Stoermer and Paul J Crutzen in 2000.
There appears to be some debate as to whether the Anthropocene is a geological epoch or in fact a geological event, but AWG proposes the former, and in recent years has been looking for geological evidence to officially declare the beginning of a new epoch in Earth’s history.
“The Anthropocene denotes a proposed geological epoch in which the impact of human activities on the Earth system as a whole has become distinctly visible,” states the Anthropocene Curriculum, the long-term initiative of AWG.
In 2016 AWG voted to decide that the mid-twentieth century marked the start of the Anthropocene; a time known as the “Great Acceleration.”
“The proposed definition of a stratigraphic Anthropocene signifies that human activity has become a global geological force that has altered planetary conditions to such an extent that we no longer live in the Holocene,” wrote Simon Turner, AWG secretary and senior research fellow in geography at University College London, in his contribution: “Defining a New Earth Epoch.”
He went on to explain that AWG proposes that industrialisation, globalisation and technological advancements have caused “unprecedented changes to planetary systems” during the mid-twentieth century.
What’s in Crawford Lake?
Since 2019 AWG has been investigating 12 sites across the world for potential GSSPs or “golden spikes,” looking for traces of humanity’s impact on the planet.
“These sites include a variety of environments with unique geological characteristics and deposition types, but all record high-resolution archives of human impacts over at least the last century,” wrote Turner in “Defining a New Earth Epoch.”
AWG has stated that all candidate GSSP sites should contain radionuclides from atomic weapons tests, as this has been identified as “a primary stratigraphic marker of the mid-twentieth century.”
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Locations included the Antarctic Peninsula, Ernesto Cave in Italy, Flinders Reef in Australia, Karlsplatz square in Austria, and Beppu Bay in Japan (among others); but it was ultimately Crawford Lake in Canada that was selected as the best candidate GSSP or “golden spike” site to indicate the onset of the Anthropocene.
AWG explains that Crawford Lake is a small but deep lake which fills a sinkhole in a protected conservation area in Southern Ontario as part of a UNESCO Biosphere Reserve. They explain that it’s what’s known as a “meromictic” lake due to its unique properties.
“The bottom layer of water does not mix with the upper layers and is therefore isolated from the atmosphere, preventing disturbance of the lakebed,” AWG explains, stating it has been a “site of scientific interest for decades.”
This allows for the undisturbed accumulation of sediments in the bottom layer of the lake. These sediments can provide insight into the time they were deposited as well as the environmental conditions of the past.
What’s more, due to the length of time it will take for the lake to fill in at the current rate of sedimentation (30,000 years), AWG explains that “it has the potential to create an Earth archive that extends into the far future.”
For example, some of the traces revealed in Crawford Lake sediments included:
- Charcoal; indicating agriculture and logging after European colonisation in the 19th century.
- Plutonium and caesium “bomb” radionuclides; indicating fallout from the atomic testing and bombs in 1945.
- Gaseous and particulate emissions; indicating the increased burning of fossil fuels from the 1950s.
There were also many other anthropogenic indicators observed across the 12 different locations.
Other indicators of anthropogenic impacts included: Pesticide derivatives; microplastics; technofossils; sulfur possibly from industrial pollution; barium possibly from oil drilling; as well as evidence that may indicate fertiliser use, deforestation and changes in temperature, ecosystems and the biosphere.
Not all of these indicators were observed at all sites, but there was overlap.
VIDEO: Scientists designated a small body of water near Toronto, Canada as ground-zero for the Anthropocene, the proposed geological epoch defined by humanity's massive and destabilizing impact on the planet. pic.twitter.com/oqVyaql9ep
— AFP News Agency (@AFP) July 13, 2023
Is the Anthropocene already upon us?
Though Crawford Lake has now been selected and proposed as the candidate GSSP or “golden spike” site to define a new epoch, it must first be officially ratified.
Crawford Lake’s GSSP must pass through three further stages of voting, gaining approval from three major geological organisations: The Subcommission on Quaternary Stratigraphy, the International Commission on Stratigraphy, and the International Union of Geological Sciences.
If the GSSP site is approved, the Anthropocene can officially be added to the International Chronostratigraphic Chart, marking the latest milestone in Earth’s geological history.
Have you lost track of time?
Here is the latest chronostratigraphic chart from the International Commission on Stratigraphy, charting 4,600,000,000 years of Earth history – now also available as an #iPhone app and in 23 languages on https://t.co/Ro4x0BT8R3#Earth #time #geology pic.twitter.com/vz1C8KyaCN— IUGS (@theIUGS) February 16, 2022
Editor’s Note: The opinions expressed here by the authors are their own, not those of Impakter.com — In the Featured Photo: Rock layers. Featured Photo Credit: Ramon Perucho.
