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Experts declare Anthropocene has begun

It means Age of Humans. A scientific working group – at an international meeting of geologists – just recommended including it in the Geologic Time Scale.

Operation Crossroads, an early nuclear test at Bikini Atoll, 1946. Image via U.S. Department of Energy.

Nuclear test at Bikini Atoll, 1946. Image via U.S. Dept. of Energy.

Has humanity become so prevalent and powerful on Earth that we’re now globally affecting the geologic record, the actual rock record used by geologists to divide the past into named blocks? If the answer is yes, should scientists declare we’ve entered a new geologic epoch? This week, a group of 35 scientists said, yes, we are globally affecting the rock record and, yes, we should officially consider a new epoch. They would name it the Anthropocene, meaning Age of Humans, a word first introduced by two scientists in the year 2000 that’s now gaining wider scientific acceptance. The Anthropocene Work Group reported this conclusion on Monday (August 29, 2016) to the 35th International Geological Congress going on this week in Cape Town, South Africa.

If scientists decide to accept the Anthropocene into the Geologic Time Scale, they’ll have to decide when it began. Scientists speak of golden spikes in Earth’s sediment layers, events laid down in the rocks that clearly demarcate one geologic epoch from another.

A widely known example of a golden spike occurred with the demise of the dinosaurs, 65 million years ago. Most scientists believe an asteroid strike ended their dominance, due to the discovery in the late 1970s of iridium in the rock record on all parts of Earth. Iridium is rare on Earth (found mostly in Earth’s core), but common in the rest of the solar system. This layer of iridium in the rock record is said to mark the time of the asteroid impact; it’s the golden spike that marks the end of the Cretaceous epoch.

What would be the golden spike separating the Anthropocene – the Age of Humans – from the rest of history? The answer is arbitrary, and members of the Anthropocene Work Group do not entirely agree.

But 28 of the 35 scientists do agree that the golden spike for the Anthropocene comes around the 1950s. That’s when the great acceleration began on Earth, when our human impacts intensified and began to happen globally, not just locally, scientists say.

About 10 members of the Anthropocene Work Group said they felt the start of the Anthropocene would coincide with the beginning of nuclear bomb testing. It started in the late 1940s and caused radioactive elements to be dispersed across Earth and thus laid down in the rock record.

Other group members pointed to other ongoing signs of the Age of Humans, however, which will ultimately find their way into the rock record, including plastic pollution, soot from power stations, aluminium and concrete particles and high levels of nitrogen and phosphate in soils, derived from artificial fertilizers.

And so defining when and how the Anthropocene began – assuming scientists do accept it and include it in the Geologic Time Scale – is a task that lies ahead.

Plastics aren't as permanent as you might think. Plastics will break down into tiny, persistent fragments that will become buried in sediments. Image via Scripps, BBC.

Plastics aren’t permanent. They’ll eventually break down into fragments that’ll become buried in Earth’s sediments. When future geologists uncover these fragments, they might point to the start of the Anthropocene. Image via Plastic Ocean Gyre blog.

Colin Waters from the British Geological Survey is secretary to the Anthropocene Work Group. He told the BBC:

This is an update on where we are in our discussions.

We’ve got to a point where we’ve listed what we think the Anthropocene means to us as a working group.

The majority of us think it is real; that there is clearly something happening; that there are clearly signals in the environment that are recognizable and make the Anthropocene a distinct unit; and the majority of us think it would be justified to formally recognise it.

That doesn’t mean it will be formalized, but we’re going to go through the procedure of putting in a submission.

If the Anthropocene is formally defined as a geological epoch beginning in 1945 (scenario C in Figure 1), then newer structures, such as the Grant Marsh Interstate 94 bridge over the Missouri River in Bismarck, N.D. (foreground), would be classified as “Anthropocene.” Older structures with or without recent updates, such as the Bismarck railroad bridge (center) would be classified as Holocene and Anthropocene. Photo credit: Joel M. Galloway, USGS

If the Anthropocene were formally defined as a geological epoch beginning in 1945, then newer structures – such as the Grant Marsh Interstate 94 bridge over the Missouri River in Bismarck, N.D. (foreground) – would be classified as Anthropocene. Older structures with or without recent updates, such as the Bismarck railroad bridge (center) would be classified as Holocene and Anthropocene. Photo via Joel M. Galloway, USGS.

So the word Anthropocene, though not a part of the official scientific lexicon yet, is gaining acceptance among scientists. You can read more about the history of the word, which was coined in the year 2000 by atmospheric chemist Paul Crutzen and ecologist Eugene Stoermer in this article: What is the Anthropocene?

By the way, scientists now speak of our geologic age – basically everything since the end of the last major Ice Age, corresponding to the rise of complex human civilizations – as the Holocene. Holo is from a Greek root meaning whole or entire. You sometimes hear the Holocene called the Recent age.

Some have argued that the word Holocene is good enough to describe our human impact and that we don’t need the new term Anthropocene. There are arguments for and against including the Anthropocene in the Geologic Time Scale under the subheads multiple meanings and contrasting philosophies – and also hierarchy – in this article.

In the meantime, just remember the word Anthropocene.

You’ll be hearing more about it in the years ahead.

The Geologic Time Spiral from the U.S. Geologic Survey. Read more about this image.

The Geologic Time Spiral from the U.S. Geologic Survey.

Bottom line: The Anthropocene Work Group reported their conclusions on August 29, 2016 to the 35th International Geological Congress in Cape Town, South Africa. The group said that the new epoch Anthropocene should be considered for official inclusion in the Geological Time Scale.

Deborah Byrd

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