In it, he responds to criticism and ultimately comes to the conclusion that - even if no trace of humanity is left (no civilization, tools, etc) in "deep time" - the biosphere itself has been changed by humanity, and that gives the concept of the Anthroprocene validity.
https://www.theatlantic.com/science/archive/2019/10/anthropo...
I was going to post a comment in response to some of the points in the article, but upon seeing that the other article existed... what's the point?
The point of the anthropocene, as presented in the second article, is to acknowledge the effect humans have already had on the earth. The point of the first is to acknowledge how little an effect that is, relative to other events in geologic time. The events described in that article still stand - global temperature differences of 8C over a few tens of thousands of years, sea levels 400 feet lower (and that was a blink of an eye ago in geologic time), a 90M year long ice age.
I consider this claim to be complete nonsense. Change my mind. There are 4 billion year old rocks still on the earth to be found. 7,000 years of civilization is not going to be completely erased in a few million.
There may be no structures or artifacts that survived 65 millions years, but there's plenty of holes that would have, in natural structures that to all appearances are older than 65 million years, should have been about as available then as they are now, and are obviously undisturbed.
Despite being the third most common element in the earth's crust, aluminum cost more than gold and was rarely used for industrial purposes before the Hall-Heroult process for smelting it from alumina and the Bayer process for smelting it from Bauxite.
Rare-earths display a similar profile: they are abundant in the earth's crust, but not in any form that we can easily mine and extract. What if a past dinosaur civilization mined out all the easy rare-earth deposits building iPhones and batteries?
When I've gone on Geology 101 field trips, once or twice the instructor was like "And this rock was formed over a billion years ago." It was invariably followed by "Deep within the earth's crust, several miles below the surface." Rocks that are on the surface get weathered and eroded; quartz and feldspar on exposed granite become successive layers of sandstone.
It's different from the case he cites, but tracks the general point that there are limits to what we can learn about prehistory / "deep time"
Wouldn't there at least be some places where ruins or landfills were largely exposed? And aren't there lots of materials that would stand out since they degrade slowly?
For example, what is going to happen to all of the concrete and steel in Manhattan in the course of five million years? Will it really be compressed to a thin layer that is barely noticeable or something?
Yes, there will be a thin but noticeable layer of hydrocarbons and odd pollution signatures in the crust that will act as a permanent geologic record of our existence.
If you were specifically looking for it.
Somebody might notice a lack of elephant teeth above a peculiar boundary, or a reduction in fish bones and corals, and look closer at the boundary. But to notice a lack is much harder than to notice the advent of something new. A layer of paperclips might not attract much attention, once oxidized, or be interpreted with anything like fidelity.
Paleohistory is pretty fascinating, and it's easy to forget just how small we are on this big earth and how much things differ from today. For example:
We're technically in an icehouse age. An icehouse age is defined as "any period of time where glaciers exist anywhere on the planet". For about 80% of geologic time, there is no such thing as a glacier, or of snow and ice for that matter. The entire earth's surface is above freezing, even the North and South poles. What we know of as an "ice age" (a glaciation) is a feature only of icehouse states. We currently happen to be in an interglacial of an icehouse age, which is why we think of this as being a warm period. But geologically, the earth is well below its temperature average.
https://en.wikipedia.org/wiki/Greenhouse_and_icehouse_Earth
It's likely that the earth has completely frozen over on at least two occasions, with the entire planet being encased in a gigantic ice sheet like Europa:
https://en.wikipedia.org/wiki/Snowball_Earth
The larger of these two incidents may have been triggered by the evolution of photosynthesis and the addition of oxygen into the earth's atmosphere, which also likely caused a major mass extinction among the dominant anaerobic bacteria of the time:
https://en.wikipedia.org/wiki/Great_Oxidation_Event
Sea level over time has fluctuated by 300-400 meters. That means that anything at an altitude of less than about 1000 feet (which is the vast majority of human settlements) was once underwater. (Well, technically land level fluctuates more than sea level, so most of these low-lying areas are actually sediment weathered off of nearby mountains.)
https://en.wikipedia.org/wiki/Past_sea_level
There've been some massive outburst floods in the past, like the draining of Glacial Lake Missoula (a pleistocene lake roughly half the volume of Lake Michigan, held in by an ice dam on the Clark River nearly 2000 feet tall) which released an outflow 13 times the size of the Amazon River:
Most likely almost all of human history in the Americas, and maybe too in Africa, is 200 feet under the sea.
https://www.theatlantic.com/science/archive/2017/06/the-ends...
