M. Justin Wilkinson, Texas U., Jacobs contract with NASA-JSC / NASA
Humans have changed the earth so profoundly that scientists say we have entered a new geological period: the Anthropocene.
But when did the new era officially begin? And how exactly should it be defined?
These are the questions that geologists in locations around the world are pursuing with increasing urgency. The teams examine 11 locations on five continents and look for a place where rock, mud or ice perfectly captures the global impact of humans.
As is so often the case in science, teams work together and compete with one another. They share information, but ultimately only one place is crowned the “Golden Spike” location for the Anthropocene: the place on earth where a line in rock, mud, or ice represents the unique markers of the Age of Man.
Each geological period has a golden tip that allows scientists to pinpoint when the period began by identifying a specific layer in rock, mud, or ice and assigning a date to that layer.
For example, in a particular ice core from Antarctica, there is a line of pollen and dust that is the official reference point for the beginning of the Holocene, which began with the end of the last Ice Age about 12,000 years ago. The golden spike location for the end of the age of the dinosaurs about 66 million years ago is a line in a cliff in Tunisia where global debris from a meteorite impact is clearly visible.
However, it was difficult to find a place with golden spikes for the ages of the people. “It has sparked a pretty heated debate about what the Anthropocene is,” says Colin Waters, geologist and chairman of the Anthropocene working groupwho coordinates the Golden Spike research sites.
Anthropologists, sociologists, and historians disagree as to when the age of man began or whether such an epoch even exists.
“There are some people who see an ancient Anthropocene dating back to a hundred thousand years ago when we see people controlling and using fire,” said Nicholas Kawa, an anthropologist at Ohio State University. Others point to the dawn of agriculture as the moment when humans made a major impact on the planet.
Still others, including prominent indigenous scholars, point to colonialism as a turning point.
“By linking the Anthropocene with colonization, attention is drawn to the core of violence and the consideration of indigenous philosophies and processes of indigenous self-government is required as a necessary political corrective measure,” wrote the scientists Zoe Todd and Heather Davis in a 2017 paper titled about the importance of the date or the decolonization of the Anthropocene.
However, the geologists at the Anthropocene Working Group do not believe that the age of humans began hundreds or even thousands of years ago. They argue that industrialization and the atomic age are the best geological markers of the new era. In particular, scientists on the Golden Spike teams focus on a time in the 1940s and 1950s when some people began detonating atomic bombs.
“There are many potential markers, but a favorite would be radionuclides from fallout,” says Waters of the Anthropocene Working Group. The Manhattan Project and the bombs the US dropped on Japan during World War II released plutonium and other radioactive elements into the atmosphere near where the detonations took place.
But fallout didn’t really cover the earth until the US and Soviet Union began testing much larger bombs in the early 1950s. “It’s only when you get to around 1952 – the big thermonuclear detonations – that you see these radionuclides everywhere,” says Waters.
Therefore, 1952 looks like the front runner for the official start of the Anthropocene era.
“I talk to my mom about it because I think it’s really funny,” says Anthropocene Working Group geographer and secretary Simon Turner. “My parents were born in a different geological era.”
In order for 1952 or another year to be officially recognized, the members of the Anthropocene Working Group must vote on a location with gold tips. That vote is slated for 2022, which seems a long way off, but as Turner puts it, “it takes time to do science”. The clock is ticking.
As a result, 2020 was an important year for scientists working in potential Golden Spike locations in Asia, Europe, North America, Australia, and Antarctica. Each location was chosen because it has undisturbed layers of mud, ice, or rock that have accumulated dust, dirt, chemicals, and other evidence of human activity. Some sites have been studied for decades, which means scientists have a whole lot of information about what is beneath the surface.
Over the past year, this research has taken off as scientists work to piece together definitive arguments as to why their website is a perfect example of the Anthropocene. In 2020, Polish researchers analyzed mud from a peat bog on the border between the Czech Republic and Poland. Chinese researchers took a core sample from the bottom of a lake in northeast China and began looking for radioactive cesium as well as soot from fossil fuel burning – a likely secondary marker of the Anthropocene. Australian researchers were looking for radioactive isotopes in corals, and researchers in Germany were looking for microplastics in the mud from the bottom of the Baltic Sea.
The work is arduous and each location presents different challenges. One location in Antarctica is based on a 133-meter-long ice core that was drilled in 2012. Another location in California required scientists to drill three stories into the mud below a reservoir that was built in the late 19th century and quickly filled with sediment.
A Stanford University team took sediment samples from the Searsville Reservoir in California. The site is one of eleven around the world that could officially define the beginning of a new geological period, the Anthropocene Epoch. Anthony Barnosky / Stanford University, Jasper Ridge Biological Preserve hide caption
Anthony Barnosky / Stanford University, Jasper Ridge Biological Preserve
Anthony Barnosky / Stanford University, Jasper Ridge Biological Preserve
“At this point, there has been more than 11 meters of sediment since 1892,” says Alison Stegner, Stanford University geologist and leader of the team investigating the reservoir as a potential location for golden spikes for the Anthropocene.
The sediment is bad news for the people who built the reservoir to hold water, not mud, but it’s a boon to scientists. “If we have a lot of sediment in a place like this, we can examine what happened in the past in really fine detail,” says Stegner. “We can actually look at what has happened seasonally over the past 127 years, which is really, really rare.”
This is because every summer plants grow and die in the reservoir and a layer of organic matter collects on the bottom. A large amount of sandy sediment arrives every winter with the rainy season. Stegner and her team can count these summer-winter couplets to travel back in time and estimate the exact year of each shift in the mud. If they can find a layer of radioactive elements, they may be able to determine not only the year but also the time of year. For example winter 1952.
At this point in time, Stegner had been working on this project for years. The finish line is just around the corner. Your team will come up with their results in the next year or so. Then she will see how the mud from her reservoir holds up against all other anthropocene evidence.
“I mean, I would lie to say that I am not competitive at all,” said Stegner. “But at the same time, everyone else who works in locations around the world are our employees. In many ways, we raise each other.”
She also finds the work sobering in many ways. “It’s really exciting. It’s also a little rattling alternately,” says Stegner. “We think about changes on our planet that are so monumental that we have to name a new era.”
Kawa, the anthropologist, says the official definition of the Anthropocene era raises more questions than answers for people who grapple with the way people live on this planet. For example, what does it mean that the age of man is officially defined by some of the most destructive acts of mankind?
“You think of so many evil facets of human history that we like to sweep under the rug,” says Kawa. “It might actually be helpful to say, ‘We’re using an atomic bomb to define the human era. What does that say about us? And what should future markers look like?’ “”
And he says the Anthropocene epoch is unique because it combines a vast geological history with narrow questions of human responsibility and morality. Geologists studying the ages of the dinosaurs don’t have to think about who was responsible for the meteor that ended it all. “Meteors, we don’t think about them ethically or morally,” says Kawa.
The Anthropocene is the work of man – some more than others. “We have to be careful not to put the responsibility at the feet of everyone,” says Kawa, “because some people and some human groups and some social institutions are more responsible for it.”