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February 7, 2012 6:38 PM Subscribe
Science fiction filter: if we disappeared tomorrow, what traces of our civilization would likely still be around 65 million years from now? (I've read The World Without Us but it doesn't go to this timescale)
"Ancient spacefaring dinosaurs" is a thing that occasionally crops up in SF, but since bone fossils manage to hang around that long it seems like other things would as well.
"Ancient spacefaring dinosaurs" is a thing that occasionally crops up in SF, but since bone fossils manage to hang around that long it seems like other things would as well.
If we're lucky, some of our trash, structures (think huge, long-lasting ones like the pyramids), and maybe even some corpses and tools will be preserved in the sedimentary record.
Basically, the best we can hope for is that traces of what we have done will stick around as fossil imprints or bizarre sedimentary structures in some rocks.
posted by Strudel at 7:07 PM on February 7, 2012
Basically, the best we can hope for is that traces of what we have done will stick around as fossil imprints or bizarre sedimentary structures in some rocks.
posted by Strudel at 7:07 PM on February 7, 2012
According to the wonderful documentary by National Geographic "Aftermath: Population Zero," the only thing that will be left is stainless steel. (And everything else will recover just fine. "All we need to do is get out of the way.")
posted by Melismata at 7:11 PM on February 7, 2012 [1 favorite]
posted by Melismata at 7:11 PM on February 7, 2012 [1 favorite]
Best answer: The single most important thing left behind will be certain absences. Geologists will be able to determine that a technological civilization once flourished here because ores and other mineral deposits that should be present will be missing.
...and there's also polychlorinated biphenyls, which don't occur naturally and are probably immortal.
Those will be useful for dating our civilization, because they'll show up at a certain point in ocean sedimentary layers.
posted by Chocolate Pickle at 7:27 PM on February 7, 2012 [3 favorites]
...and there's also polychlorinated biphenyls, which don't occur naturally and are probably immortal.
Those will be useful for dating our civilization, because they'll show up at a certain point in ocean sedimentary layers.
posted by Chocolate Pickle at 7:27 PM on February 7, 2012 [3 favorites]
I think any masses of uranium that we have left over will still be around, it has a halflife of millions of years.
posted by empath at 7:30 PM on February 7, 2012
posted by empath at 7:30 PM on February 7, 2012
Best answer: The dead giveaway should be the amount of Pu-244 occurring at a particular, consistent level in ice cores or other samples. Pu-244 has a long half-life (80MY) and is not generally produced by natural terrestrial processes (it doesn't occur very often in nuclear reactors, so unlike some other isotopes, its existence would not be easily explained by a natural nuclear reactor in close proximity to a volcano or something). I believe there are detectable concentrations of it around today as the result of atmospheric nuclear tests, and if you posit a global nuclear war wiping out civilization, then there would definitely be a nice sheen of the stuff on the planet that ought to be detectable later.
Also, based on what's around today from 65M years ago, there would presumably be fossils from deceased humans, provided that some cemeteries are located in areas conducive to fossil formation (or, more grimly, presuming that some people would die in fossil-conducive areas during whatever calamity you're positing to wipe out civilization). Some of those fossils ought to show evidence of civilization to a careful observer: signs of intentional burial, maybe even some evidence of medical technology or weapons (skulls with bullet holes, maybe?). A lot would depend on what skeletons managed to become fossilized, but there are a lot of people covering a lot of the planet, so I don't think that's an unreasonable stretch.
posted by Kadin2048 at 7:36 PM on February 7, 2012 [3 favorites]
Also, based on what's around today from 65M years ago, there would presumably be fossils from deceased humans, provided that some cemeteries are located in areas conducive to fossil formation (or, more grimly, presuming that some people would die in fossil-conducive areas during whatever calamity you're positing to wipe out civilization). Some of those fossils ought to show evidence of civilization to a careful observer: signs of intentional burial, maybe even some evidence of medical technology or weapons (skulls with bullet holes, maybe?). A lot would depend on what skeletons managed to become fossilized, but there are a lot of people covering a lot of the planet, so I don't think that's an unreasonable stretch.
posted by Kadin2048 at 7:36 PM on February 7, 2012 [3 favorites]
Vertebrate teeth fossilize very well, and in fact there are some species in the fossil record which are primarily known from their teeth. Human teeth are likely to survive that long -- and some of those will have metal fillings, which cannot possibly happen without technology.
posted by Chocolate Pickle at 7:44 PM on February 7, 2012 [1 favorite]
posted by Chocolate Pickle at 7:44 PM on February 7, 2012 [1 favorite]
Microchips will probably be a dead giveaway. I understand that most of them will decay but the epoxy package will take a long time to rot. Inside that is the actual chip which is mostly silicon crystal-- essentially quartz. It will shatter but microscopic fragments will show ordered structures. Besides, there are billions of them so the odds of having lucky survivors is pretty good.
I think when people say there will be nothing left they mean no visible surface traces. There will be lots of crap in the fossil record, including our bones.
posted by chairface at 7:44 PM on February 7, 2012
I think when people say there will be nothing left they mean no visible surface traces. There will be lots of crap in the fossil record, including our bones.
posted by chairface at 7:44 PM on February 7, 2012
Best answer: I had asked something similar a while back, and one thing that stuck out for me is the fact that humans have spent a lot of time collecting materials from spread-out locations, and collect it in very tight areas. So, for example, on a multimillenium scale, future archaeologists are likely to find a lot of iron oxide, hydrocarbon residue, heavy metals like lead and mercury, all compressed into a very specific layer covering a few thousand years, and only a few miles across. Without geological reasons for such a thing, like how gold veins or diamonds are created, a logical (not not conclusive) possibility is that society built a city on that spot millions of years ago.
It was also pointed out that, if glaciation occurs on a similar scale to the last few hundred thousand years, cities at high latitudes are likely to be wiped away and smeared over the continents, leaving little proof behind. Add in continental plate movement and the changing oceans, and it's unlikely anything would be left.
posted by AzraelBrown at 8:14 PM on February 7, 2012 [2 favorites]
It was also pointed out that, if glaciation occurs on a similar scale to the last few hundred thousand years, cities at high latitudes are likely to be wiped away and smeared over the continents, leaving little proof behind. Add in continental plate movement and the changing oceans, and it's unlikely anything would be left.
posted by AzraelBrown at 8:14 PM on February 7, 2012 [2 favorites]
Unfortunately, atomic diffusion will eliminate the sub-micron scale features on microchips over hundreds or thousands of years.
posted by monotreme at 9:30 PM on February 7, 2012
posted by monotreme at 9:30 PM on February 7, 2012
Read The Earth After Us by Jan Zalasiewicz. It looks at the rock record 100 million years into the future based on current understanding of geological processes (with a sci-fi perspective!) and covers exactly what you're asking for. It's also a lot more fun than The World Without Us.
posted by freya_lamb at 3:51 AM on February 8, 2012 [3 favorites]
posted by freya_lamb at 3:51 AM on February 8, 2012 [3 favorites]
It's a bit more cut out to be a drinking game than a television show, but Life After People occasionally throws in some science with their psuedoscience. The thing that comes to mind right away are carved granite monuments, like Stone Mountain in Georgia. It will remain in pretty much great condition for millennia, provided it isn't damaged dramatically in a meteor strike or massive seismic change or something of that nature.
posted by juniperesque at 7:18 AM on February 8, 2012
posted by juniperesque at 7:18 AM on February 8, 2012
Fired clay and reinforced concrete are obviously technolgical and protected from weathering (especially water and freeze thaw cycling) will still be around. So underground earth works like mines will still be detectable.
Also the cut part of cut and fill highway building in stable areas should be detectible.
posted by Mitheral at 8:42 AM on February 8, 2012
Also the cut part of cut and fill highway building in stable areas should be detectible.
posted by Mitheral at 8:42 AM on February 8, 2012
Granite quarries I imagine would be pretty durable non-natural remnants.
posted by zippy at 12:07 PM on February 8, 2012
posted by zippy at 12:07 PM on February 8, 2012
underground earth works like mines will still be detectable
cut part of cut and fill highway building
Keep in mind though that the question is about 65M years. Significant geologic changes are extremely likely at that timescale.
65 million years ago, the Appalachian mountains in the U.S. were a flat plain, just starting to be pushed up into their current shape. Here's an approximate map of what the world looked like.
I think it's unlikely that many earthworks would survive in any recognizable form, except perhaps in the most geologically stable areas... and even then only at low enough latitudes so that they wouldn't be scraped away by glaciers.
Maybe someone with a better understanding of geology can suggest what areas and how much of the earth would probably not be affected by plate movement, but it doesn't seem like that much.
posted by Kadin2048 at 2:11 PM on February 8, 2012
cut part of cut and fill highway building
Keep in mind though that the question is about 65M years. Significant geologic changes are extremely likely at that timescale.
65 million years ago, the Appalachian mountains in the U.S. were a flat plain, just starting to be pushed up into their current shape. Here's an approximate map of what the world looked like.
I think it's unlikely that many earthworks would survive in any recognizable form, except perhaps in the most geologically stable areas... and even then only at low enough latitudes so that they wouldn't be scraped away by glaciers.
Maybe someone with a better understanding of geology can suggest what areas and how much of the earth would probably not be affected by plate movement, but it doesn't seem like that much.
posted by Kadin2048 at 2:11 PM on February 8, 2012
Kadin, large areas can be preserved way beyond 65 million years. If worked or inhabited areas are buried, eg in mudslides or sediment-bearing floods they will be preserved, and will continue to be buried under further successive layers. They may be metamorphosed by the heat and pressure of burial at depth, but many fossils can a still be visible as distinct shapes, anomalous to the material around them, if those beds resurface.
Later movement may cause uplift - at which point erosion kicks in, top layers are stripped away and the ancient strata are exhumed. This might happen when plates collide and previously buried strata finds itself hoiked up during a mountain-building episode. Hence the marine limestone sediments (with fossils!) currently perched atop Mount Everest. Those layers will be gone soon soon enough but it could take a lot longer than 65million years for strata bunched up at the base of the mountain to completely erode away.
So, not everything gets destroyed by plate movement. Some of the most ancient still recognisable sedimentary rocks today are ~3.9 billion years old. Granted these are rare and have been heavily deformed but it shows how long this stuff can hang about.
posted by freya_lamb at 5:30 PM on February 8, 2012 [1 favorite]
Later movement may cause uplift - at which point erosion kicks in, top layers are stripped away and the ancient strata are exhumed. This might happen when plates collide and previously buried strata finds itself hoiked up during a mountain-building episode. Hence the marine limestone sediments (with fossils!) currently perched atop Mount Everest. Those layers will be gone soon soon enough but it could take a lot longer than 65million years for strata bunched up at the base of the mountain to completely erode away.
So, not everything gets destroyed by plate movement. Some of the most ancient still recognisable sedimentary rocks today are ~3.9 billion years old. Granted these are rare and have been heavily deformed but it shows how long this stuff can hang about.
posted by freya_lamb at 5:30 PM on February 8, 2012 [1 favorite]
This thread is closed to new comments.
posted by nicolas léonard sadi carnot at 6:46 PM on February 7, 2012 [2 favorites]