Stuff in salt mines will last until the mines get compromised.
The only things that are going to get rid of all macroscopic evidence of human activity on/near Earth are probably:
A) The point at which the entirety of the Earth’s crust has been recycled by tectonic activity (is this even likely to happen?)
Or
B) The expansion of the sun, engulfing the Earth and the moon
For scenario A, there might still be some sort of chemical trace, such as unnatural distributions of radioactive isotopes.
Not on Earth, but the two golden records on the Voyager probes have lifespans in excess of 1 billion years.
Wikipedia has a timeline of the far future.
This takes deep time to a whole new level.
The push to have the recent period recognised as the Anthropocene includes recognition that this will be a distinct and definable stage in future geological times, not just now, so that when the Venusian Geobots do their core samples in 2.5 million years time they will see a distinct geological phenomenon in the sandwich of layers.
Concrete in geologically stable settings, like the centres of tectonic plates should do pretty well.
I don’t know whether to be inspired or despaired by some of those events…
I’m thinking large concrete structures away from continental margins … the structure may collapse but how long until every last trace of evidence disappears? … it’s not uncommon to mine Mesozoic limestone to make cement, and cement is a hell of a lot tougher than limestone … so that starts the bidding at sixty-five million years …
Wind and water erosion would at first work to cover and destroy this concrete evidence, however after so much time this erosion work both ways, uncovering what was previously covered … consider the greenstone belts in Eastern Canada, these are dated in billions of years and there they are right on the surface for anybody to see …
All the Cesium-135 that was included in the original solar system had all but completely decayed around a billion years ago … it was unknown on the Earth’s surface until July 16th, 1945 … so presumably this man-made Cesium will be detectable until 5,000,001,945 AD …
This is the argument against any previous Great Civilizations on Earth before humans evolved … we would find traces of such a species’ activity … and we don’t … so no Great Civilizations before humans … ||
I was going to post links to earlier discussions of this theme, but there are too many. Here are the ones with the closest titles.
What will be the largest post-industrial man-made structure to remain standing the longest?
How long would it take for all traces of our current civilization to disappear?
How long would it take for a modern city to disintegrate…
Would any structure last longer than the Hoover Dam?
There’s probably half a dozen more on the Life After People show.
The oldest fossil I found in brief internet search is 4.2b years old.
To show civilization, all we need is for one person with some body modification that exhibits civilization-requiring tech (braces, pacemaker, artificial…something) to be fossilized somewhere, right?
How about a fossilized iPhone? Is there any reason that bits and pieces of man-made items wouldn’t survive as part of the fossil record, even if macro-level structures eventually fall away?
As we have fossilized dinosaur footprints in mud that are still around it’s not implausible that you could and probably would get some artifacts preserved in this way. Even if all of the plastic and other degradable parts rotted away, the metals would still be there, and perhaps the outline of the device would be preserved in a similar way to the footprints in mud.
Curious
Has anyone kind of decided what calamity befalls earth and to what extent the atmosphere is eaten by the space bats?
If it is a magnetosphere loss type thing, we would have some heavier gasses left i am thinking like argon, co2 etc?
We of course couldnt live in that but other things could
If it’s the galactic shop vac space bat, i assume we are talking 100% loss of all free gasses, heavy or not?
Outside the temporary water vapor phase, what do you suppose might be the new equilibrium?
When i try to think of the things the earth it self might put back into the atmosphere (or the void that was the atmosphere) everything i think of is toxic, some is caustic which might help erase signs of man being here i guess if it builds up enough.
But if the magnetosphere is intact after galactic shop vac bat leaves, i supposed the water vapor separating could slowly replace the oxygen?
No idea at when density, though it could be bad with too much oxygen and no fire inhibiting gasses? or would the earth itself give off enough of those?
Still be a desert wasteland wouldn’t it?
I would think, that with the current martian atmosphere, something like the Eiffel tower, or the Empire State building, or the great wall of China etc would sit indefinitely unless they became buried in dust, or perhaps sand blasted away?
I don’t think there is anything there to rust corrode or dissolve them?
Hehe which is kind of ironic because the surface is basically covered in rust.
Rust in a place that cant’t rust 
Mars bears a lot of visible LHB impact craters, if like Earth, if there was a lot of burying activity going on, wouldn’t these craters be mostly filled in and gone?
Though i suppose you could argue that it got buried before the water was gone or something? On earth we have water and weather with water to help dissolve and bury or remove evidence of things. as well as the help of living things like plants etc.
As cool as the idea is, and it makes for great books, i’m afraid that given what we currently know, Mars has just been dead too long to have much change of having ever
evolved any complex life forms, at least in any form we would be familiar with.
At least it appears that way to me.
That said, i still like reading Burroughs
The Yucca Mountain nuclear waste repository is supposed to last at least one million years: Yucca Mountain nuclear waste repository - Wikipedia
The earth is surrounded by satellites in geostationary orbit. At 22,500 mi high these will not experience orbital decay for millions of years. Likewise the LAGEOS satellites are in stable orbits 7,624 mi high and expected to endure for millions of years: LAGEOS - Wikipedia
This tool lets you graphically view satellite orbits. You can see there are so many in geostationary orbit they form an obvious ring. After these fulfill their functional life they are moved to a “graveyard” orbit about 300 miles higher:
Exactly. The Canadian Shield is your best bet. At 4 billion years old, it’s probably the most stable craton in the world and certainly the largest mass of land with that kind of track record. The Canadian Shield was the first part of North America to exist above sea level and for all this time has not been encroached on by the sea (or by other tectonic plates playing bumper cars / demolition derbies). On the minus side, it did get its entire surface shaved off by the glaciers.
I just had a though
With no atmosphere as a mediating buffer, wont the surface temps on earth start swinging from extremely hot where the sun is shining directly, to extremely freezing?
Even with water boiled off from lack of pressure, concrete wont take an intensive and rapid freeze thaw cycle, it breaks down, crumbles.
Mightn’t that speed up the loss of evidence of us?
How about jewellery? A cut diamond in a gold setting is going to last a very long time.
No atmosphere means no greenhouse effect. It would be pretty cold here. I think that some of the Earths oceans would freeze over after a lot of the water was lost when the atmosphere goes, though not sure about that part.
With no atmosphere you don’t have a freeze/thaw cycle, because no atmosphere means no water, and hence going above and below 0C doesn’t matter.
The reason freeze/thaw cycles destroy things is that water gets into everything, and when the water freezes it expands, making a crack. And then more water gets into the crack, which then freezes and the crack gets bigger.
But if there’s no water to get into the cracks it doesn’t matter anymore.
As was mentioned earlier, a heavily cratered surface means that the surface hasn’t been reworked for billiions of years, aside from new craters. But even the moon has the seas which have been reworked much more recently. And Mars has a lot of craters, but not as many as the Moon.
Earth itself wouldn’t be that way even if the Earth lost all it’s volatiles, because Earth is extremely geologically active compared to the Moon and Mars. Only a small portion of the crust–the aforementioned Canadian Shield for instance–is billions of years old, almost all of it is much younger. And note Venus is the same, its whole surface was reworked and all its craters destroyed.
This sounds wildly wrong.
Here’s a BBC article about stone tools made by pre-humans 3.3 million years ago. They were not especially difficult to discover: