Time flies. We’ve barely had a few thousand years to get settled into one epoch, when suddenly it’s time to start a new one. Better reset your watch.
Just to bring you up to speed, the Earth is currently in the Holocene epoch, which began 11,500 years ago with the dawn of human civilisation. But some scientists now believe we are moving into a new epoch, called the Anthropocene, and are pushing to have it officially recognised as a formal unit of geological time. As far as they're concerned, the Holocene is so last week and the Anthropocene is where it's at. When did that happen?
The age of the Earth is estimated to be about 4.7 billion years, so you need a big calendar to track its changes. Geologists use stratigraphy to determine the different stages in the life of Earth, studying the evidence in the layers of rock, ocean sediment and ice cores to build up a chronology of Earth. The table of geological periods puts a bit of structure on the Earth’s history, slicing it up into manageable chunks of several million years. For geologists, this table is set in stone, and not to be changed on a whim.
But advocates of the Anthropocene, who include a UCC professor, say humans have wrought such seismic changes on the planet that a new timescale is called for. Agriculture, mining, damming and construction – not to mention fracking – have changed the face of the Earth, chlorofluorocarbon gases (CFCs) have eroded the ozone layer, carbon dioxide levels and sea levels have risen, and plastics, particulates and nuclear waste have left an indelible mark on the Earth’s atmosphere and surface. Geologists thousands of years in the future should be able to look at the layers of rock and sediment and see our big, stomping boot prints all over the place.
The Kardashian epoch?
You could legitimately claim we’re living in the Kardashian epoch – every time Kim breaks a nail or gets a bikini wax, the entire planet shifts on its axis – but before an epoch can be codified as a formal unit of geological time, the evidence for it has to be seen in the geological record, and not just on Twitter. An Anthropocene Working Group has been set up to look at the data and see if it stacks up.
Some say the proposed epoch is just pop-culture nonsense, or that the pro- Anthropocene lobby is politically motivated, trying to tamper with the geological table to get across an environmental message. Others feel we need more perspective, and should wait at least another thousand years or so to see just how much humans have affected the Earth before we barge into a new epoch with our size 12s.
Even among those who are convinced we are in the Anthropocene era, there is disagreement as to when exactly it began. Did it begin with the great migrations from Europe to the Americas in the 1500s? Did it start with the industrial age? Or did it begin on July 16th, 1945, when the first nuclear device was detonated?
"I think there's very little doubt that we as humans have affected the air and climate of our planet," says John Sodeau, professor of physical chemistry at University College Cork. "The main marker for me would be the increase of carbon dioxide from the time of the industrial revolution, in about 1850, to now."
Prof Sodeau is director of the centre for research into atmospheric chemistry at UCC, which studies the climate-change effects of particulate matter emitted by the burning of fossil fuels and the use of bioaerosols.
“I think, unofficially, most scientists who work in air monitoring will say we’re already in the Anthropocene.”
Plutonium in the environment
Prof Stephen Daly of the UCD school of geological sciences has a more recent start date for the Anthropocene: "Some time in the middle of the 20th century, around 1945. Before 1945 there was no plutonium in the environment, and now there is."
Plastics, lead, mercury and other toxins have also permeated the environment over the past century, but Prof Daly doubts if much of man’s detritus will still be there for scientists to find in future millennia.
“Humans are profoundly affecting their own habitat, but whether that will be expressed geologically is difficult to predict. People get concerned about saving the planet; well, the planet will look after itself. In the longer-term evolution of Earth, we’re almost irrelevant. If you want to be pessimistic, the Anthropocene will arrive abruptly and disappear just as quickly.”
Much of the Earth’s crust reprocesses itself every 200 million years, says Prof Daly, so any trace of the Anthropocene era is likely to be wiped clean along with any evidence we were ever here at all.
“Two hundred million years is an inconceivable amount of time for our minds. But for the Earth it’s a tiny fraction. And humans profoundly affecting their own environment, probably leading to the extinction of our species, is going to have no influence on how the planet operates. It has its own internal engine; it’ll just keep on going whether we’re here or not.”
FROM JURASSIC TO JESUS: EARTH TIME VS HUMAN TIME
The table of geological periods chronicles the 4.7 billion-year history of Earth. Precambrian Time is a bit murky, encompassing the first four billion or so years, when the atmosphere, oceans and micro-organisms were forming. The Paleozoic Era began 542 million years ago. The Mesozoic or Age of Reptiles began 251 million years ago. The most recent era, the Cenozoic or Age of Mammals, began 66 million years ago with the extinction of dinosaurs. Each of these eras is divided into periods such as the Jurassic or Cretaceous, which are in turn divided into epochs, each one lasting several million years. The current epoch, the Holocene, began only about 11,500 years ago, so you can see why some scientists suggest we’re jumping the gun a bit with the proposed Anthropocene. When you look at the timescales involved, you might wonder if humans are somewhat overstating their impact on the planet as a whole.
“On a human timescale, you can see these environmental effects a few years, a few decades, or 100 years later, but over a timescale of hundreds of years, thousands of years and still longer, the preservation of that archive is itself unstable,” says Prof Stephen Daly of UCD. “When you look at things from a geological perspective, you have to think on a different scale, and that’s very hard to get your head around. We spend a lot of time wondering about Jesus 2,000 years ago. These are trivially short intervals compared with geological time. One of the great insights geology gives you is to appreciate how small we are.”
