By Bill Chameides

More than any other species before us, we humans are dominating the planet, but will you be able to see it in the rocks?

That's what geologists are debating as they consider adding a new geologic term to the vaunted Geological Time Scale. Such matters are not taken lightly in the scientific community, and so the proposal has begun wending its way through the various bodies, which will weigh whether or not there are scientific reasons for the addition. And while it might not take as long as say, an actual epoch, it will be a decision many years in the making.

When It All Began -- Anthropocene

In 2000, the Nobel Prize-winning chemist Paul Crutzen coined the term "anthropocene" to describe the current epoch in which humans are the dominant force for change on the planet. From the loss of biodiversity and the degradation of most of the planet's ecosystems sparked by the billions of people now inhabiting them to the bitterly contested warming that the globe is experiencing and the unprecedented number of invasive species we've introduced to ecosystems, we are changing the planet as we know it and in a way that we normally have attributed to geologic processes.

The term anthropocene is informal, but the geological community is now considering formalizing it; the term and its implications are before a working group from the Subcommission on Quaternary Stratigraphy (the Quaternary refers to the current geologic period). It's no sure bet it will make it into the official Geological Time Scale classification, but it's interesting and noteworthy that such an august body traditionally concerned with the over 4.5 billion-year history of the Earth would even consider it.

Are we such a force of nature that our influence on the planet will, millions of years from now, be a geologically useful division of time? And what's the case for and against establishing this as a new classification next to other epochs such as the Lower Jurassic and Pleistocene?

Anthropecene vs. Holocene

Geologically speaking, we are in the Holocene or Recent epoch that began roughly 10,000 years ago when the last of the continental glaciers receded. The argument for announcing the end of the Holocene and the recent birth of a new epoch is that since the Industrial Revolution and the concomitant explosion in human population, our own activities have driven "geologically unique and in many ways novel changes" on the planet, as a recent opinion piece in Environmental Science and Technology argues.

Geologist Jan Zalasiewicz, of the University of Leicester, and colleagues, including Crutzen, write that the climate changes due to a buildup of greenhouse gases and the ongoing acidification of the oceans are just two major developments that shake the current time period away from the Holocene. Another is the presence of "tiny but measurable amounts of artificial radionuclides" in sediments since 1945 from the first human atomic detonations.

The question remains, though, whether these events will hold up in the geologic record. After all, that is the purpose of the geologic time scale -- to break down the Earth's history into chunks of time (as seen in rock formations) that tell us something useful about the planet's history. For example, the Mesozoic era is separated from the Paleozoic and Cenozoic by two large extinction events and so denotes a different time period.

Some argue that recognizing the anthropocene would not provide useful geologic insights into the Earth's history. Others point out that the time scale being discussed is so short that it would be more like an event -- such as the Paleocene-Eocene Thermal Maximum (see related blog entry) -- were it to show up in the geologic record.

While today's landscapes are marked by vibrant megacities and large populations, long-term and large-scale erosion, and sedimentation, even Zalasiewicz et al. note that the way that we inhabit the many places we now call home has a "remarkable, though perhaps short-lived, sedimentary signal."

A Marketing Gimmick or a Scientific Tool?

It's not clear how our dramatic influence on the planet that includes changes to the oceans and biosphere will hold up in the geologic record.

Some have commented that anthropocene seems more of a marketing term than a scientific one. Perhaps others might even think it a strategy by environmentalists to further policy goals.

And it should be pointed out that anthropocene is not the only proposed name for the current epoch. For example there's the weshouldhavecene appellation suggested, tongue-in-cheek, in a 1985 paper by geologists Prosh and McCracken of the University of Western Ontario, along with nothingcene and changeofcene. As long as we're considering new names, with tongue firmly in cheek, here's my suggestion: heyfolksletscleanupouractandstopmakinganewcene.

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