I admit I did not read the entire publication, but, at least at face value, this seems somewhat absurd to me. Within the past couple hundred years humans have built massive structures in cities that should last for many millions (hundreds of millions?) of years.
I mean, Manhattan may be under water in 100 million years (or, much sooner), but all those gigantic steel, concrete, plastic and glass structures aren't just going to dissolve.
It sounds like “gigantic steel, concrete, plastic and glass structures aren’t just going to dissolve” really depends on timescale, and geologic timescales are far beyond our typical experience.
From the Atlantic article by one of the authors: [1] [2]
When it comes to direct evidence of an industrial civilization—things like cities, factories, and roads—the geologic record doesn’t go back past what’s called the Quaternary period 2.6 million years ago. For example, the oldest large-scale stretch of ancient surface lies in the Negev Desert. It’s “just” 1.8 million years old—older surfaces are mostly visible in cross section via something like a cliff face or rock cuts. Go back much further than the Quaternary, and everything has been turned over and crushed to dust.
There is better argument and it is surface natural resources.
We know, that before industry took off we had huge amount of natural resources almost lying on the ground. Now many of crucial resources have to be dug from huge depths or recovered from dilute sources.
I can't imagine a previous industrial civilization leaving huge amount of resources available on the surface. Almost by definition, industry is about scaling and efficiency and it always look to get to the results as quickly as possible.
Depends on time frame. Plate tectonics will reset things quite a bit over truly vast time scales.
Over shorter time scales this argument mostly holds, though one can imagine an intelligence with technology but with less expansionary drive and conspicuous consumption than humans. This intelligence may use resources more slowly.
There are plenty of places within a two hour drive or train ride from NYC where you can see gigantic steel concrete and brick structures that are less than 150 years old well into the process of dissolving. If you live in prosperous cities and don’t have to maintain property, it’s understandable how you can be unfamiliar with the relentless processes of rust, melt-freeze weathering, erosion, storm damage, how quickly vegetation grows, and so on.
In periods of 100s of millions of years whole continents disappear or move around, new layers of rocks are formed and old layers are buried. The Rocky Mountains formed just 55 - 80 million years ago.
Cities disappear completely. Concrete and glass becomes rock (again), steel is oxidized and is just layer of iron ore. Plastics degradate and breaks into nanoparticles.
As the article speculates, most evidence would be likely something like synthetic biomarkers in deep sea sediments. Traces of industrial chemicals not produced naturally. Wrong chirality in some organic chemicals. Transuranic elements.
Some zircons have been dated back to the hadean era, when the earth was forming. Any information for building something that sticks around long term would be contained in them.
To be fair, industrial-level civilization (engines, mass production, etc) doesn't actually require large, reinforced concrete structures[0].
That said, the answer to TFA's question is "almost certainly yes, unless they deliberately tried to conceal geological evidence of their existence, and probably even then".
I would guess that glaciers would encapsulate the skyscrapers and dislodge them from their foundation, and when they receded leaving a huge pile of steel and concrete. Even if that was later encapsulated by magma, future geologists would have to wonder about metal 'veins' that were so structured and why part of the rock was basalt and another part was an exceptionally hard and dense form of limestone.
At this point I've sort of lost track of the argument. I read articles about how glaciers preserved soft tissue from the ice age (> 22 kiloyears ago)[1], I've got a bit of rock with a perfectly preserved trilobyte from Montana that is over 380 million years old, and yet people reading want to argue in this thread that massive amounts of inorganic structures built by humans to last for centuries will somehow be dissolved/eroded beyond detection in some short period of time.
So it seems unequivocal to me that human impact on the planet will be preserved for millions of years via the same mechanisms that have preserved snapshots of what was going on millions of years ago.
I don't think so, meteoric iron (according to the wonderful blog series[1]) is early Egyptian.
Iron (and steel) is stable outside the presence of oxygen and water. It doesn't just dissolve. And certainly if it were part of the steel reinforcement inside concrete in a building where special measures had been taken to insure that neither oxygen nor water would come in contact with it (as modern skyscrapers do) would persist for an exceptionally long time.
If there are two things the glaciers you mentioned a few posts back would accomplish it would be creating cracks that would expose things to water and oxygen, and also expose the resulting heaps to loads and loads of water. This is how stones found in glacial deposits look like: https://sv.wikipedia.org/wiki/Rullstens%C3%A5s#/media/Fil:Ru...
Note how rounded all the stones are. And the stones that are there are generally speaking a LOT more resilient than any variant of limestone will ever be (including concrete).
What about when the skyscraper’s pieces are submerged under saltwater for a million years? Or are covered up by a mile of river sediment and then plunged another 5 miles under the earth for several million years?
Or the concrete develops cracks, allowing water into the steel reinforcement, which expands, further cracking the concrete until it collapses. Like modern bridges.
I mean, Manhattan may be under water in 100 million years (or, much sooner), but all those gigantic steel, concrete, plastic and glass structures aren't just going to dissolve.