Scientists are currently debating in earnest the question of where we lie in relationship to the geologic boundary of the Holocene, the period of the most recent natural evolutionary development on earth, and the Anthropocene, the epoch characterized by the influences associated with humankind-and which many have decided needs to be recognized as a new epoch .
A big issue has to do with time scale.
Epochs like these are generally millions of years long, so the scale from which we are trying to judge whether the boundary has been crossed is so different from the scale of the transition itself that whether we can even make the judgement is a matter of serious debate. We have only looked at this question for a matter of tens of years.
But, if a geologist, looking at the geologic record some millions of years in the future, were to try to assess where the boundary between Holocene and Anthropocene was, he/she would be looking for a break between two different strata (like looking at the wall of the grand canyon and noticing a layer of red turning into a layer of yellow) in the ground where each inch corresponded to a million years or so.
It’s really kind of mind bending.
One of the things such a geologist would be looking for is something called a trace fossil, and the remnants of cities would certainly be one such. Imagine London being overrun by planet Earth’s erosional process, like, say, Thebes or Machu Pichu. One of the clearest indicators of the difference between the time before, when it became the metropolis we know today (i.e., the Holocene) and this new epoch (the Anthropocene) would be the remains of the Underground rail system, which didn’t exist during the Holocene, but was a prominent feature of major cities worldwide in the Anthropocene. There are today more than 20 cities in China larger than London, so our imaginary geologist would have widely spread data to help him/her mark the boundary.
Of course, if my view of the future turns out rightly, the Anthropocene will wind up being a very small layer marking a distinct strata bounding the Holocene/lifeless boundary and our geologist will have to be an extraterrestrial with a very peculiar speciality.
Hmmmm, sounds like the seed of a science fiction piece. Let’s explore that a bit.
Trace fossils. What would they look like?
Besides massive cities and the underground transportation lines, there are elaborate communications infrastructures crossing all the continents and cables linking many of them laid on the floors of our current seas. There will be the remnants of vast scars from mining resources from the Earth. Ammunition and nuclear materials dumps should be considerably more plentiful than nations.
Maybe the whole of the regions currently marked by aquifers, such as California’s central valley, or the vast Ogallala in America’s midwest, will have collapsed as a result of our removing the groundwater. I’d expect the implosions of Kansas City or Bakersfield, even if they only fell to a depth of twenty feet or so, would leave some sort of definable record for millions of years.
I wonder if our current practice of agriculture will be evident in thousands of years.
What will be the remnants of our wars? Our pandemics? Of our space programs? Will our geologist friend even tell we had such without finding the evidence of a rover, long buried on an otherwise barren planet, Mars? Will they, the scientists of this distant future, look at Earth first?
Perhaps the story would start with an accidental encounter with one of our probes flying through the vastness of space?
Our effect as an extinction force will show up by the sudden absence of non-human species in the fossil record. It may take our researcher a lot of arguing to ascribe the eradication to any of the longer surviving species, but I wonder wether he/she would pin the horror on humanity versus the cow, say? How would you tell from such a vantage point?
Sometimes I wish I had more confidence in writing fiction. I seem better suited to fantasizing plot points than to telling the human stories that make the whole thing interesting enough to read.