Earth has entered a new geological epoch in which human activity has become the dominant geological influence, a group of 35 scientists representing the Anthropocene Working Group argued recently at the 35th International Geological Congress. As the group's name suggests, the new epoch would be called the Anthropocene: “Anthropo” means “man,” and “cene” means “new.”
Geology is the study of solid earth. What makes up the rocks on Earth? How do those rocks change? What can the layers of rock tell us about what Earth was like thousands or millions of years ago? To a geologist, major changes in rocks denote shifts in time. This means geologists look at time differently than the rest of us do — if a geologist tells you she's running a little late, you might need to keep dinner warm in the oven for a while.
We divide the geological time scale into chunks: eons, eras, periods, epochs and ages. An eon is the biggest chunk of time, and an age is the smallest. But it's not like there are exactly 10,000 years to an age and 1 million years to a period. The chunks depend not upon a number of years but upon what layers of rock tell us. Transitions between periods may be marked by new types of rock or indications of global events, such as mass extinctions.
Officially, we are in the Phanerozoic eon, Cenozoic era, Quatenary period and Holocene epoch. The Working Group must determine when the Anthropocene began — it suggests the mid-20th century, when chemical and climate change intensified. If an international committee of scientists agrees with the Working Group's recommendations, we will switch from the Holocene, the epoch following the Paleolithic Ice Age, to the Anthropocene. Following this decision, geology textbook authors will get busy making some serious revisions.
So what prompted the Working Group to recommend this change? It's all about how human activity has progressively shaped our planet since 1950. We've tested nuclear weapons, relied on nitrogen and phosphorous-heavy fertilizers, burned countless tons of fossil fuels, disrupted the carbon cycle and generated millions of tons of plastic.
These activities leave their mark. They are significant enough to indicate a detectable time shift to geologists. Someone in the year 3016 could look back on the geological record and recognize differences in the rocks from the Holocene to the Anthropocene.
It's important to point out that there's no inherent judgment in the Working Group's recommendation. The scientists aren't trying to make a political point or argue for global changes. They are just making the observation that the changes are great enough to justify a new epoch on the geological time scale.
It can be both awe-inspiring and a little frightening to consider that humans are now one of the most powerful influences shaping the earth. What we do today is recorded in the rocks. And while these geologists aren't necessarily calling for a change in our behaviors, their recommendation suggests our actions could have a significant impact on our legacy.