Last Trace of Civilization... Timeframe

Factual Questions
1

So assume that tomorrow for some unknown and unknowable reason that the Earth’s atmosphere is stripped away to a Mars like environment.

Due to this every living organism including us meatbags dies and the Earth is now a cold dead and lifeless planet.

Under this scenario, how long would it take Father Time to render EVERY LAST REMNANT of our existence to unrecognizable dust? And by dust, I mean a state where if an alien species found our planet and deployed tiny roving type robots to cover a few select regions, they would not be able to tell that buildings, bridges, homes, aircraft carriers, cars and human ever existed on this world?

Knowing that something like Gobekli Tepe dates to something around the 10th millenium BCE, could we assume that in a million years or more, all traces of mankind would easily disappear to anything but an archeological dig?

I am of course drawing an anlaogy to Mars as I have been debating my “friend” and Alex Jones type conspiracy nut who reads crap talking about Cydonia and pyramids on Mars. The only question he has ever asked me that gave me pause was the - i guess - plausible idea that a civilization COULD have existed millions of years ago and time has removed all traces of it other than the river beds scientists have confirmed.

Thank you, your feedback is appreciated! :wink:

2

I think the big dams will be around for a very long time.

3

I think mines would outlast everything else.

4

The dams will crumble. Any overspill around the side gives you massive erosion as the entire dammed lake pours out through the channel that gets wider and wider.

But yeah, there will be gigantic piles of concrete in lots of places that will last for tens or hundreds of thousands of years. But most of those concrete piles will get covered by vegetation pretty quickly.

How easy is it going to be to tell a natural hill covered with trees from an artificial concrete hill covered with trees?

If the aliens are allowed to do archaeology then the answer is hundreds of millions of years, since glass and stone objects can last that long. We’re constantly digging up fossils that old. But objects like that in geologically active areas will get reworked and won’t be so easy to find 100 million years from now. And a couple of ice ages will scrape most human artifacts in the continental glacial zone clean. So the Alberta Sulfur Pyramids probably won’t last millions of years.

5

I think there are traces that would last for millions of years. Aluminum is an example. Pure aluminum is hardly never found naturally but it’s a common manufactured product. An alien species coming to Earth in a million years would find unnatural (literally) amounts of pure aluminum and know this was evidence of a past technological civilization. And then they’d start arguing about how to spell it.

6

The Cheyenne Mountain Complexwas built into solid granite and engineered to withstand earthquakes. You’d need a scenario where the natural passage of time erodes through blast doors designed to withstand a 30-megaton nuclear strike, letting the elements take their toll on the man-made structures inside, and THEN eroding the cave so much that no one could detect any signs that it had been constructed, rather than naturally formed.

Yeah, a million years would do it, but 10,000 years? I’m pretty sure there’d still be evidence.

Would our hypothetical alien robots also be on the Moon to detect all the stuff we’ve left there?

7

Note also that Mars is a lot less geologically active than Earth. The reason it has massive geologic structures like Olympus Mons and Valles Marineris is that those features don’t get moved around by plate tectonics, or filled in or rounded down by wind and water, or covered over by plants, or oxidized by the chemically reactive atmosphere.

So features on Mars are going to last a lot longer than on Earth.

8

Not to be pedantic, but not everything would die if the atmosphere stripped away…at least not for a very, very long time.

On the Earth or just in the solar system? I believe that some of the satellites and certainly stuff on the Moon and probably Mars would be around for millions of years, at least potentially. As for on Earth, no atmosphere and no bacteria would mean less decay (though the action of removing all the atmosphere would certainly be violent) probably means a lot would be around longer than it would have been. The Earth being geologically active still, regardless of the atmosphere would probably mean some things would be covered over in volcanic eruptions and the like, some destroyed by continental drift, but I’d guess that without wind and weather something like Mt Rushmore or other large stone monuments would last a lot longer than they would otherwise. How long? I’d guess a million or so years is possible, potentially, instead of the several hundred thousand I recall predicted on Life with Humans.

I don’t know, off the top of my head, how often land recycles through plate tectonics, but that would be the longest anything actually on the Earth COULD make it…but I’d guess 100 million years would probably be the maximum for 99% of all human remnants to continue, with a maximum being 5 billion or so when the Sun goes red giant I suppose.

9

Something that’s been mentioned in previous threads such is this is that rock quarries would be identifiable as such millions of years from now–perfect right-angle cuts through granite will be found in those archaeological digs.

That, and some Nokia phones.

10

There was another thread like this. The Great Pyramids will be around a long, long time. Maybe buried in dust and sand, but they’re not going away quickly. Other pyramids around the world will last also. With a Mars like atmosphere erosion is very slow and the largest objects get buried in dust. On the surface without digging everything may be buried before too long though. Assuming massive skyscrapers fall from tremors then dust and sand might cover it all in a thousand years. But I think more likely whatever wind is left keeps uncovering traces of massive structures for a very long time. Of course if they picked the wrong select regions without a visual scan of the entire planet then tiny roving robots wouldn’t find any signs of civilization now.

11

Any millions of styrofoam cups and packing peanuts :stuck_out_tongue:

12

there was a tv series called Life After People
and one from canada called Aftermath: Population Zero

they both say that by 25,000 years almost all traces will be gone. . .except

mc

13

It’s OK to Be Smart is a pretty good YouTube channel from PBS. One episode contemplates an Earth 100 million years in the future. In their hypothetical, the Earth still has an atmosphere and life. But, they predict that even in 100,000,000 years, traces of human life will remain buried in the rock. The episode points to a couple of things mentioned in this thread, like aluminum. It also points to the residue left behind by atomic weapons. It says that the alien explorers in 100M years will be able to see the clear appearance of elements created in nuclear explosions.

That's a cool YouTube channel, by the way. Veritasium is another good one.
14

Note that I missed the part where the atmosphere got sucked away by Alien Space Bats.

That changes things. Of course what happens after that is the oceans start to boil in the vacuum left behind to create a new atmosphere of water vapor. Are the ASB’s sucking up the water vapor too until the oceans are gone and the ice caps sublimate?

If we’re just killing the plants and animals by removing the atmosphere once and then allowing everything to reach equilibrium you’ll still have a water cycle where for a long time most of the atmosphere is water vapor, but with unpredictable rains. Small changes in temperature could cause massive rains and snows orders of magnitude greater than anything we’ve ever seen on Earth before. And with the plants dead, that leads to massive erosion.

On the other hand, water vapor is a greenhouse gas, and so the new all-water-vapor atmosphere will lead to a runaway effect that could lead to Venus-like conditions, and no rains, and the oceans boiling to bedrock in an uncontrollable positive feedback loop when temperatures all over the world are over 100C.

15

Interesting OP

Not all the atmosphere would leave, ok on retrospect it could, but i am not sure what calamity the OP has envisioned?

I am assuming collapse of magnetosphere allowing the sun to strip off the easy parts of the atmosphere?

heavier components (that we cant breath) would stay, because gravity would hang on to them.

Hydrogen would get stripped, Oxygen would get stripped etc.

And i think liquid water would begin to vanish over time because of the loss of hydrogen.
I may or may not be incorrect about that.
The oceans will die though, no free oxygen.
Maybe anaerobic stuff can live, maybe not. I am not sure what happens to temperature.

I am pretty sure atmospheric pressure tanks and that would seem to increase evaporation, but with out the rest of the atmosphere working together, im not sure what happens from there, and any h2o that separates will be lost ad the oxygen and hydrogen fluff off into space.

Mind you i am assuming that something has killed the magnetosphere in this catastrophe and it did not come back to life.

Planetary temp would change, though i am not exactly sure if it would swing hot or cold?
Drop in pressure could let green house stuff float high and hold heat?
Would it create a runaway effect?

More UV will come through if the atmosphere is destroyed, i’m assuming Ozone went byebye, but i dont know if the “new” atmosphere will hold more heat, or lose more heat.

In any case i am thinking the changes will be very detrimental to plant life, which would be the big terrain changers otherwise.

Also with no free oxygen, i assume iron can not even rust?
So all the things that plants would dislodge or tear down, and things rust and oxidation would normally tear down would stand for a lot longer.
Be kind of like a desert planet i guess?

I am guessing you would see a lot of steel and concrete man made things sticking up out of the planetary desert for a long long time?

Perhaps the OP has envisioned something more calamitous?
Something that sucks the planet bare of all free gases from the atmosphere, making a vacuum?

I would guess then ET gets a lovely museum in pristine condition as well as a walking tour of the pacific trench?

16

Wont the water, being blasted by all the stuff from the sun now blasting through unopposed cause it to separate into oxygen and hydrogen which in turn are lost to space?

mind you i am assuming the magnetosphere has ceased and allowed said space bats in?

17

NM…on reflection I’m guessing they wouldn’t freeze but would mainly boil, as Lemur said…and that would create yet another atmosphere.

18

The hydrogen will be lost but it will take millions of years and by that time we will have a new equilibrium atmosphere. The all water vapor atmosphere will be temporary, but the new equilibrium state after a million years will be drastically different.

19

Göbekli Tepe is not a useful comparison for the OP. When its people decided to shut down operations there, circa 8000 BC, they covered it up with earth and went away and forgot about it. That had a lot to do with it remaining secret and hidden for millennia.

The local farmers and anybody trained in archaeology who stopped by would observe the mound, which is a tell that gives away the location of ancient settlements in the Middle East, where layers are built up over time, plus the fact that pieces of ancient stone carvings would be turned up in the soil at times, and putting 2 and 2 together would know there was an ancient archaeological site in there. What wasn’t known until it was excavated was how ancient it was and how significant the discovery would turn out to be, completely rewriting the history of late Paleolithic and Mesolithic culture. The ancient people there deliberately hid the site from view.

20

Without an atmosphere and water, our major structures, even those made of metal, will probably last forever, unless they get gobbled up by earthquakes or volcanic eruptions. There will hardly be any erosion or weathering.