Traces of humanity--after 10,000 years?

Factual Questions
1

Let’s say every human being on the face of the Earth suddenly drops dead. The human race is utterly extinct.

10,000 years pass.

A space expedition arrives from some relatively nearby planet and begins to survey Earth to determine whether it ever bore intelligent life; and, if so, what level of technology and civilization it had attained.

The aliens have detection instruments not too much more advanced than those we have now–nothing too “magical.”

What signs of prior human habitation and society would be left for them to see? Would any traces of human structures remain visible on the surface? (I presume underground missile silos, etc, would still exist…) Would the girders of our buildings still exist just below surface “dirt,” or would they have long since disintegrated? Are there modifications to the physical landscape that would obviously indicate that intelligent life had been there? Is it likely that the subways of various cities would still exist more or less intact? How about that huge underground shopping mall in Canada?

Would any of our satellites remain in orbit? (I think not.) How about the equipment we left behind on the moon?

2

Open pit mines with the slag heaps would indicate some sort of large scale operation.

Desert airports maybe? Aside from heat and dust not much to wear them down I would think.

3

There would be a thick layer of crushed aluminum beer cans where our lake bottoms once existed.

My guess would be that tectonics and weather would, after building material used, have the biggest effect on the varying degrees of preservation across the landscape.

A large airport runway in Kansas would probably still be usable but the TransAmerica building in San Franciso is going to be a lot shorter.

4

I think the pyramids will still look like something human-made.

Other solid big stuff made of stone will probably look like it too.

And don’t forget the Statue of Liberty sticking partway out of the ground on the beach.

5

Also, Apes with weapons might be a tip-off that sentient beings once roamed the land.

You have no rights under ape law!:smiley:

6

Ceramic toilet seats. Future archaeologists will find a layer of them, even many thousands of years in the future.

Certain parts of the world will have weird isotope ratios - residue of nuclear fuel processing.

The moon will also have various man-made artifacts, although that will take a detailed search to find.

7

I’d think a lot of structures would partially remain, possibly enough to tell what they once were. Many metals would rust away, but maybe not stainless steel - anyone know just how “stainless” it really tends to be? The monument at Mt Rushmore would deteriorate, but might still be obviously artificially created. Any cities in areas that become desert over the intervening time might be well preserved under sand - it’s happened a couple of times in Egypt, it could happen again. Volcanism could preserve some of our cities just like Pompeii and Herculaneum - Seattle seems like a good candidate for this. Hasn’t this happened recently on Monseraat, and somewhere in Italy near Mt Etna?

Unless an asteroid scored a direct hit on the landing sites, everything we left on the moon (even footprints) should remain untouched. Probes on Mars might be buried under dust, but would remain otherwise untouched. The Pioneer and Voyager probes will keep going unless something acts on them to mess up thier inertia. I’m pretty sure most earth-orbiting satellites would fall out of orbit, but maybe not the ones in geosyncronous orbit. Apollo rocket stages that have settled into solar orbit would probably still remain and occasionally come back into the vicinity of the Earth, barring any spectacular collisions with other objects. The NEAR spacecraft will probably remain untouched and unaltered on the surface of the asteroid Eros forever, unless an impact smacks it into a million pieces.

Nuclear waste should still be radioactive and possibly detectable if the aliens are looking hard enough.

The Great Wall of China might still be noticably man-made. Same for Hadrian’s Wall. Junkyards may still exist as vast deposits of iron and other elements - they may be able to tell that the iron had been forged at some point in the past by examining its chemical composition. Deep down in landfills, newspapers from the late 19th century sometimes remain perfectly preserved - who knows, maybe some of our rubbish might achieve immortality in a similar manner.

Millions of uneaten Twinkies might litter the landscape where grocery stores once stood. Twinkies never go bad or spoil.

8

The biggest telling sign would probably be the bajillion square miles of land we moved to build highways, dams, mines, cities, etc. Even if the buildings aren’t standing, under x dozen feet of earth you’d probably be able to find most of the concrete foundations and structures that made up the large cities. Somewhere like Los Angeles (assuming it hasn’t fallen into the ocean by then, but 10,000 years isn’t much in geological terms) would be kinda interesting to see…

Actually, I think the most damaging things could be, say, a new ice age with glaciers covering most of the populated Northern Hemisphere. Glaciers can carve mountains to pieces - they wouldn’t blink at New York, though they would leave an interesting debris trail.

9

G’day

Bear in mind that we have found footprints that dinosaurs left in sand 70 million years ago. And footprints in sand are a byword for impermanence. Incredibly delicate things can survive for incredible lengths of time in favourable conditions.

We have recovered mummies and jewelry from Egyptian graves five thousand years old.

Neolithic earthen ramparts and burial mounds are still recognisable across much of Eurasia after three-to-five thousand years of weathering. Bet that the much larger and more solid earthworks of modern highways will last at least as well.

Megalithic monuments up to seven thousand years old are still recognisably artificial. I bet the Pyramids and the Great Wall, not to mention a lot of modern stone construction, will last in recognisable form at least as long.

The Sphinx’s present surface is what, four thousand years old (and maybe more)? It is carved from sedimentary rocks. Mount Rushmore is carved from granite (which is much harder), and isn’t being sand-blasted by desert winds.

Concrete. Roman concrete construction is still in recognisable form after 1700 years without maintenance. Even concrete piers in sea-water have lasted since Roman times. Large masses of modern concrete, such as dam walls, bridge pylons, and skyscraper foundations seem likely to last at least as well.

Ceramics. We dig up recognisable potsherds, sometimes even whole pots and tiles in pristine condition, at least three thousand years old. Often they are turned up by ploughs. Modern ceramic tableware will last at least as long. And heavy ceramic objects, such as bricks, bathroom tiles, roof tiles, and toilet bowls, not to mention the insulators used on high-voltage transmission lines, will be sticking out of the ground all over the place for hunreds of thousand of years after we have gone.

And then there is technetium. Technetium has such a half-life that it is doubtful that a single atom survives in the Earth from the nucleosynthesis that produced the material of which Earth formed. And the amounts that are produced spontaneously in nuclear reactions in uranium ores are truly miniscule. But nuclear weapons tests (an attacks, ie. Hiroshima and Nagasaki) produced quantities of technetium that will still be apparent to anyone who is looking for them (eg. in ocean sediment) after hundreds of thousands of years.

Even some of our bones may last ten thousand years. Look for cemeteries in alkaline (limy) soil, in areas without geological uplift.

Regards,
Agback

10

I’d guess railway right-of-way where the tracks had once been would be a very interesting clue for our bug-eyed friends.

While roads would probably be long gone, the heavy duty railway embankments, and more likely, cuttings through hilly terrain carved out of solid rock, would likely provide the newcomers with a geographical join-the-dots which they could follow to other, less obvious clues: cities, mines, ports, etc.

11

Fascinating!

I should have realized that ceramic products and stainless steel would survive.

I suppose when my brain protests that lots of ancient stuff has disappeared, it’s thinking about habitations in jungle or forested areas, where the work of vegetation (and associated water) does the job. But of course much of the citified world is in dry climates.

OK, now an ancillary question:

What if God turned on the faucet and, having killed off humanity, decided to inundate all dry land? (This is divine water, appearing out of nowhere.) Everything is under water for thousands of years–then the excess water vanishes–things dry off–and the aliens come. NOW what would remain for them to see/detect?

12

When sculptor Gutzon Borglum found out the granite at Mt. Rushmore erodes at the rate of approximately one inch every 100,000 years, he added an additional 12 inches to George Washington’s nose, saying, “It will give him another million years …”

Quote attributed to a Discovery Channel or History Channel story about Mt. Rushmore.

13

I’m glad you picked 10,000 years. Because that’s how old the oldest know human ruins are.

Jericho is the oldest known city. It has been excavated down to the earliest level, which is believed to be around 10,000 years old. According to this site, an archaeologist named Kathleen Kenyan excavated “a tomb located near the deepest layers of the city. Inside the tomb were a number of skulls covered with clay. The skulls were dated at about the seventh millenium BC and were beautifully decorated with paint.”

http://emuseum.mnsu.edu/archaeology/sites/middle_east/jericho.html

So that gives you some idea of how long signs of humanity can survive. 10,000 years ago is the Neolithic era, by the way. Jericho was inhabited through the Mesolithic, Neolithic, and Bronze-Iron eras. Pretty impressive.

14

The Statue of Liberty is hollow. And made of copper. One good hurricane reduces it to scrap. Or one good lightning bolt.

After 10,000 years, just scrap.

Wooden ships, in very deep, very cold water will not decay at all.

The Cheyanne Mountain Defence Headquarters, the hollow mountain that holds NORADs command center, will probably still exist. There may even be documents there.

15

Twinkies ® would still be as edible as ever, though not proof of intelligent life, for 9.7 Billion years.

16

…we have this fruitcake in the freezer from 4 Christmases back…

17

I once heard someone claim that there is nothing to show signs of habitiation like a hole that shouldn’t be there.

18

I live on a small lake in the city. There are about 200 houses circling the lake, and pretty much every one has a stone firepit facing the water.

10,000 years from now, aliens will discover a small dry circle with small stone fire pits around it, and concoct elaborate theories regarding the strange rituals that must have been carried on. Why make fire in pits when you have mastered nuclear power? And what’s with the depression in the middle? Was it for sacrifices? It must have been a bizarre religion indeed.

In a similar vein, one day we will discover a cache of Egyptian documents, and find out that the pyramids were nothing more than giant slopes used for pyramid-ball. Kings demanded to be buried in them in homage to Anubus, the greatest pyramid-ball player of all time, who could do a double-whack Cheops slide better than <i>anyone</i> in the history of the sport.

19

The 1979 book Motel of the Mysteries has a humorous take on what archaeologists of the year 4022 would make of a motel room, which, due to the “Do Not Disturb” sign is interpreted as a sacred burial chamber, complete with an analysis of the strange artifacts, such as the “ceremonial chest piece” (toilet seat), porcelain sarcophagus, (bathtub) offerings to the gods (dinner tray) and a High Alter (TV set).

20

I live on a small lake in the city. There are about 200 houses circling the lake, and pretty much every one has a stone firepit facing the water.

10,000 years from now, aliens will discover a small dry circle with small stone fire pits around it, and concoct elaborate theories regarding the strange rituals that must have been carried on. Why make fire in pits when you have mastered nuclear power? And what’s with the depression in the middle? Was it for sacrifices? It must have been a bizarre religion indeed.

In a similar vein, one day we will discover a cache of Egyptian documents, and find out that the pyramids were nothing more than giant slopes used for pyramid-ball. Kings demanded to be buried in them in homage to Anubus, the greatest pyramid-ball player of all time, who could do a double-whack Cheops slide better than <i>anyone</i> in the history of the sport.