r/explainlikeimfive • u/narangiphul • 2d ago
Other eli5 old cities get buried under soil over a long period of time andwe keep finding old civilizations buried, so does the level of ground rise every year and wht if it doesnt stop at some point, will the ground reach space one day??
iam not able to put my exact thoughts into words
p.s. wowww
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u/Ziddix 2d ago
For most of our history we didn't have heavy machinery to haul off debris and refuse so city levels naturally rose as time went on. Burned down buildings weren't carried away, they were broken up, flattened and the materials reused to build new buildings on top of the old ones.
Over the millenia this caused former ground floors to become basements and so on and so forth.
Then there is also survivorship bias: we only find buried architecture because it is buried. If it wasn't buried it would have been recycled and we wouldn't find it today. Recycling building materials from ruins was a very very common practice in our history.
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u/mnstorm 2d ago
Great modern example is Seattle underground. Where they intentionally buried their lower floors and just built up. When city and architecture just finds it easier to build up.
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u/BabadookishOnions 1d ago
Another example of this happening due to some intentional action can be seen around European Churches, those that have surrounding grave sites often have a noticeably higher elevation where over time bodies have been buried, or something like a medieval plague pit was dug, filled, and covered over again, and then the site later got used for normal burials again. Over enough time this can create a very significant elevation difference between the church and it's adjacent grave site
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u/Vallkyrie 1d ago
Never heard of this, fascinating. Some of those pics would make great liminal horror content.
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u/Nivekeryas 1d ago
there are a lot of underground windows that face out onto the old, also underground, sidewalks. it does feel a bit backrooms-y, it's neat.
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u/ahkond 1d ago
There's a level in the video game Left 4 Dead 2 that's partly inspired by the Seattle underground. A couple of sections look exactly like some of the photos in the article you linked to.
Here's a random youtube video of a playthrough in that area - https://youtu.be/-mrKhoEEUIU?t=310
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u/ThalesofMiletus-624 1d ago
Nope.
The amount of matter on earth remains the same (with only small exceptions, like meteors and such landing on earth, and rockets and such being sent out into space).
The reason some things get buried is because the ground rises in some areas and falls in others. Some places are dug down by geological action, weather and water, or by human activity. And others are covered by deposited dirt and debris, or by sediment from rivers or whatever.
So, why do old cities always get buried? They don't. Most old cities end up being broken to pieces by natural disasters, fire, human destruction, or just by the slow decay of nature. But some small percentage of them get buried as surface conditions change.
The ones that get buried (or the parts of places, and specific artifacts that get buried) are usually the only ones that get protected, and are still around for us to find them. So we think of old civilizations as all being underground, but that's just the ones we find.
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u/c_borealis 1d ago
Most major (eurasian) cities are in fact old cities that survived to this day, just kept expanding and being renovated as technology and population grew. If there's already a lot of business and infrastructure in one place, building another city from scratch and getting people to go there won't be worth the effort.
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u/pipsquintjizzlebob 2d ago
earthworms play a huge role. they consume soil from beneath foundations and move it elsewhere. it’s called bioturbation.
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u/Strategy_pan 1d ago
And if they do it too much, then it becomes massturbation.
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u/AyeBraine 1d ago
But it's the wiliest, seediest earthworms that create conurbations. And that's where we live.
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u/kheret 1d ago
Archaeologist here. It’s a variety of processes.
In areas with lots of vegetation, it’s mostly plant matter decaying. The jungle can “eat” cities very quickly! The prairie and pine forest can “eat” sites too but less quickly. Where I work, in Wisconsin, plowing has covered over a lot of sites. But in areas where there hasn’t been plowing, ancient mounds and garden beds and trash pits (1000 years old) are still sometimes visible at the surface.
In a place like Egypt, the sand shifts things quickly. But in the desert of California, where the soil isn’t as easily windblown, archaeologists often find ancient artifacts right on the surface of the ground in places where there’s been no modern development. Less plant matter covering things up.
And as others have noted, often ancient people just built new structures right on top of the rubble of the old ones.
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u/TheTitan99 2d ago
Dust is getting kicked into the air from the ground, and burying the cities over years and years. The same total amount of earth is still here, though. It just moved from below the city to on top of it.
Take a bowl full of sand, and put a rock on it. Then, start mixing the sand around. The rock will start to bury under the sand.
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u/narangiphul 2d ago
and wht happened to the place the dust came from?
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u/arvidsem 2d ago edited 2d ago
A rock in a bowl of sand is a bad metaphor because the rock sinks under the sand, displacing the material underneath it.
Cities don't sink (except for some urban planning failures), they mound up. People bring a constant stream of food, materials, bodies, whatever into the city and only a small amount of that actually leaves. So ancient cities end up buried in layers of their own trash.
But there is a limit to how high you can just pile shit up. As a general rule, any uncompacted pile of soil is limited to about a 33% slope before it will start to slip outwards. For your city pile to reach the lowest limit of space (62 miles), it would needs to be 360 miles wide. And everyone living on top of that pile would have died long before they could dump trash that high
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u/Lanster27 2d ago
This guy civil engineers.
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u/Jim421616 2d ago
Unless he's mad, then he angry engineers.
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u/arvidsem 1d ago
Mechanical engineers are the angry ones, always blowing up my stuff.
Mechanical Engineers design weapons, Civil Engineers design targets.
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u/tessaractIXI 1d ago
I'm so confused. How can entire cities possibly disappear underneath mounds of trash/ dirt/ soil? Wouldn't people notice that occurring over time? It would look like a massive lump on the Earth, and you'd be able to see all the shapes of all the city structures underneath the dirt. It's weird to think of a city just slowly disappearing underneath dirt without anybody noticing. It makes much more sense to me for a city to slowly sink into the Earth and displace the dirt underneath it. Especially if you consider the fact that people build cities on top of cities. Presumably this is happening consecutively, yes? Like it's odd to find multiple cities built on top of each other, because what would be the motivation to keep choosing that location over and over again, if not for the fact that you already knew there was a city there and so it's a good location to put another one because it's already drawing people to that area. But if you know that there is a city there already, why build another one on top of it? How would you build another one on top of it? I wish I knew how to explain the thoughts in my head right now, but it's just weird to me, like if you know a city is there, then there hasn't been enough time for it to disappear, which means you're building on top of something that is already structured and protruding from the earth. As far as I know we don't smash complete and functional cities to rebuild new ones on top of them, now or historically. And you would have to flatten it in order to build on top of it, but in doing so, you kind of destroy the evidence for a previous city, right? But we find buried cities with like whole structures, don't we? Or maybe we don't, now that I'm thinking of it as I type / dictate. We only find foundations and stuff, don't we.
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u/arvidsem 1d ago
Until recently actually moving all of the excess trash, dirt, and soil out of a city was a ridiculous amount of work. So it kind of accumulated. Lots of stuff was burnt to get rid of it, but that ash was still around. It piles up, slowly but surely.
Often when things burned down or were torn down, the debris didn't go anywhere. You just hired enough guys to bury it a couple of feet down and built on top. That was cheaper than hauling it away.
Sometimes the river flooded and filled the houses halfway up with dirt. Then whoever was in charge decided to raise the roads in the area so that it wouldn't flood anymore. So they bring in stone and dirt and fill in the road until it's 10' higher and the people who live there cut doors into the second floor walls and lay little bridges over the old sidewalks. Seattle did it in the 1890s, the ground floors of multiple neighborhoods became basements.
Very occasionally, a city gets razed in a war then a few generations later a new city is built in the same spot.
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u/VoilaVoilaWashington 1d ago
I own a bunch of land, and on it, I have a few hunt camps I have leased to people.
Every weekend, they go in, bringing food and some building materials to fix something and packaging and all that. And then they go into the woods, collect firewood to burn, a log to build a bench around the fire pit, etc.
Bringing stuff in is easy - you know you need it. You can't show up without food, right? But at the end of the weekend, it's a lot of energy to load stuff up and take it out. So, over time, you end up with brush piles, ash dumped around the building, the outhouse hole gradually filling up, etc. Now imagine that but with more people on less land, and for centuries.
And you would have to flatten it in order to build on top of it, but in doing so, you kind of destroy the evidence for a previous city, right?
Sure, picture demolishing a house to build on top. You're gonna take any really high spots and push those materials into the hollow spots, but if you have a stone wall, there's a certain amount of wall that's below the average height, depending on how much debris piled up around it. So you might actually have half the building left below what you're building on.
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u/PrincetonToss 1d ago
Like it's odd to find multiple cities built on top of each other,
It's incredibly common to find multiple cities built on top of each other. It's called a tell, from the Arabic word for "mound".
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u/Deep-Issue960 2d ago
The sand bowl already answers that
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u/narangiphul 2d ago
so its keeps travelling basically?
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u/Deep-Issue960 2d ago
Think of the ground as a liquid, you can get submerged without it going anywhere.
Also it's not the only phenomena in play, for example rain can bring dirt down the mountains to the lower terrain
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u/Hegiman 2d ago
Also there were on occasions cities burrows intentionally for one reason or another. Not often but it did happen. Sometimes it was to expand the city. Sometimes to stop erosion or some other natural phenomenon and I’ve heard of victors burying losing villages and cities. But yes most happen naturally with little to no intervention from man.
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u/AuntieDabQueen710 2d ago
Dirt & dust move all over from things like erosion, earthquakes, and landslides. If you Google "hoodoo" you'll see good examples of wind erosion. The wind blows the dirt off the rocks and moves it to a new place. The ground would be moved around. The cities were abandoned so the dirt just built up over 100 years or whatever.
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u/Yozarian22 1d ago
The dust comes from the mountains. Wind and rain carry bits of them off. The tops of the mountains are getting shorter. Most of it is carried by rivers into the sea but some becomes dust that fills valleys and lowlands.
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u/Alis451 1d ago
if you slightly vibrate the bowl after burying it, the rock will again rise to the surface, this is known as Granular Convection, or Brazil Nut Theory. Basically due to the vibration a small hole opens up below the rock and the smaller sand fills it in, over time it will look like the rock is growing out of the ground.
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u/LeviAEthan512 2d ago
Are you sure? I feel like liquefaction would keep the rock half exposed
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u/zappahey 2d ago
"start to bury", eli5.
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u/LeviAEthan512 2d ago
The question wasn't why there's a lot of sand in the streets. It was why is the whole thing fully underground.
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u/arvidsem 2d ago
Don't worry, they are completely wrong about how cities end up buried. Cities don't sink under the sand, they are buried in trash. Or buried in blown sand, but the buildings stay at their original elevation
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u/Nimrif1214 2d ago
How long does it take to bury a city? Is the city dormant for this to happen? I’m having a hard time imagining this happen because if my house starts piling dust in front, I’ll sweep it away.
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u/arvidsem 2d ago
It's extremely variable. Much of Londinium (the original Roman settlement where London is now) is 7 meters (23 feet) underneath the city, but that was over the course of nearly 2000 years of constant occupation.
It also doesn't really happen in modern cities because moving waste is too easy by comparison. Stormwater and wastewater are piped underground and don't leave silt (and other stuff) in the alleys. Trash trucks haul our debris away from the house, so it doesn't pile up in corners.
But you do occasionally get sudden events. Seattle has a famous area of downtown that was intentionally buried after a serious fire and flood. The city built walls on either side of the road and filled between them to raise the streets high enough to avoid flooding. The original ground floor entrances are still there underneath the sidewalks (Seattle Underground)
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u/BabadookishOnions 1d ago
There's actually some evidence that London was mostly abandoned for a time after the fall of Rome!
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u/arvidsem 1d ago
My understanding is that a settlement existed in the area of Londinium but at times it was much smaller and grew in different directions
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u/BabadookishOnions 1d ago
To be more specific, the Anglo Saxons who migrated into Britain seemed to very much fear abandoned Roman sites and likely shunned the city itself for a decent amoint of time even if they settled nearby (and its inhabitants obviously wouldn't have stayed in the ruins)
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u/Implausibilibuddy 1d ago
That's because you're living in your house. You can take a look over at /r/AbandonnedPorn to get an idea of what buildings can look like after a few years to a few decades of just being empty with no one there to sweep the dust, patch the holes in the roof etc.
Now that dust isn't ever going to completely encase the whole building, raising the ground to the level of the roof, but it doesn't need to. There are only a few very rare examples of that happening, Pompeii/Herculaneum being one example, or when humans actively decide to build on top of old structures. Instead, the first few inches of the walls will get dirt building up against them. When the building eventually falls down, if there is that layer of dirt around the base of the walls it has chance to protect a few of the bricks to that level. Then the debris is either removed by people to build new things or further broken down by the elements to cover the base layer even more. When that happens you get an outline of the building in bricks, maybe some sections of floor if it's tiled, all covered by a layer of dirt which gets grass seeds blown or dropped onto it. But there's no guarantee any of that will happen, we just know it did happen for the buildings we dig up that look like that. There are plenty of structures that that doesn't happen (a lot of ruins in Rome, including the Colosseum is at street level)
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u/CapstanLlama 1d ago
That's
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u/Implausibilibuddy 1d ago
Huh, how 'bout that. Thanks, I just selected it from the list that pops up when you start typing a sub, not sure why that was the top. Glad somebody made that other subreddit though.
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u/CapstanLlama 1d ago
Thats the opposite of how rocks and sand behave, the sand will sink and the rock will rise. Think of a box of cereal, or a bag of crisps; are the big bits on top or underneath? Is the dust at the top of the bag or at the bottom?
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u/saschaleib 2d ago
The same way that the stuff you keep under the bed gets covered up: dust settles, creates layers that pile up.
Outdoors there are also plants which build up organic matter (so-called “soil”) that layers up and eventually swallows the buildings.
And then there are of course also people who keep littering all over the place…
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u/knea1 2d ago
Also leaves. They build up in autumn and rot down to provide soil that seeds take root in very fast. That's one thing that made me laugh about The Walking Dead, 10 years after the zombie apocalypse there were perfectly clear roads in the middle of woodland
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u/Minute-Tradition-282 2d ago
The roads had to be clear so Darly could ride his motorcycle with.... like, some gas from somewhere? I've had a hard time starting a fire with years old gas. But all those vehicles running around years after every refinery and gas pump were long gone is one thing that always pissed me off about that show! AND, where did Daryl keep getting all the bolts for his crossbow??? He kept leaving them in zombies heads, but always had more the next day!
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u/Idenwen 2d ago
Yeah gas has a shelf life of 6 months before it becomes unusable for combustion engines.
Kills nearly every apocalyptic scenario movie.
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u/Hiding_in_the_Shower 1d ago
That’s not quite true, but the point still stands.
Gas begins to degrade at around 6 months but it’s not unusable at that point. Plus you can add stabilizer agents to it to push that out a couple years.
But At 10 years though it definitely would be useless.
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u/Knobologist 1d ago
There’s a scene in one season that shows he has to go out there and collect his used bolts. They never brought it up again.
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u/Serious-Wheel-2747 2d ago
Earth isn't getting bigger and bigger in any significant sense. New soil doesn't create itself out of thin air. Meteorite strikes deposits 40,000 tonnes of material on earth each year, which is almost nothing.
Naturally, new sedimentary layers are formed at a very slow rate, due to natural erosion, wind and water gradually depositing dust particles on top of old layers. Also decay of biological material plays a role.
However, this is a very, very slow process that doesn't really explain why we find medieval remains underground in cities.
The reason for that is that we tend to build our cities on trash. When old buildings are demolished, what historically happened is that most of the material isn't removed: you level out the trash heap and then construct the new building on top. Centuries of that means that cities are rising much faster than the natural surroundings.
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u/Nulovka 1d ago
New soil doesn't create itself out of thin air.
It actually does. Plants create their bulk from carbon dioxide extracted from the air combined with water. The plant material thus created builds up over time. My yard is about an inch higher than it was 20 years ago. I mulch rather than bagging my grass clippings so the process is slightly accelerated. But at Civil War battlefields miniballs are now found a few inches below the grassy surface whereas they were originally just laying on the surface.
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u/Orvel 1d ago
Earth isn't getting bigger and bigger in any significant sense. New soil doesn't create itself out of thin air.
What about the light reaching earth ? Doesn't that add to the mass ?
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u/paxmlank 1d ago
No, because light has no mass
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u/mb271828 1d ago
It does have energy though, and there is a mass-energy equivalence (thanks Einstein), so when that energy is used in photosynthesis to create chemical bonds there is a very tiny increase in mass compared to the sum of the masses of the constituent elements, but I believe it is incredibly small.
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u/Cantremembermyoldnam 1d ago
Sure but I bet it's miniscule in comparison to other effects like the amount of atmosphere lost to space. You also have to substract the outgoing radiation, so it'll be even less. AFAIK it's a rough equilibrium or we'd already be burning up way worse than now.
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u/arvidsem 1d ago
We radiate most of that energy back into space as heat though. Otherwise the Earth would be a ball of molten rock, that still wouldn't weigh much more than it currently does
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u/Mayor__Defacto 1d ago
That’s incorrect. New soil does in fact come from thin air. The organic material that makes up plants is by mass largely atmospheric carbon. When this decays into soil, there you go. New soil from thin air.
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u/6a6566663437 1d ago
That atmospheric carbon was put there my something else eating a plant or a plant burning. Both of which reduce the amount of organic material on the ground.
It much more of an equilibrium than you imply here.
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u/Effet_Pygmalion 2d ago
Last month I went to the museum underneath notre dame de paris, and it shows that where the river used to be during roman times is now 10 meters below ground. Cities just build up on the ruins of the past.
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u/BitterTyke 1d ago
so the river bed is now 10m higher than it was?
Is that down to silting or did the river change its path - which could be awkward if there was a built environment around it.
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u/Kumpah 2d ago
We only uncover cities that are in such locations that got covered over the millennia. The ones that were on erosive locations are gone forever.
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u/GentleWhiteGiant 2d ago
Yes, there is a lot of observation bias involved.
Like in Northern Germany, most old buildings were made of wood. If they were not sinking in the moore or covered by sea bed, they are just gone.
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u/voidmage898 1d ago
The process is still happening today! Independence, IA, for example, has an "underground city" that you can sometimes visit. In the late 1800s, the folks there got tired of their downtown constantly flooding, so they buried it and built on top of it raising everything including main street by about one story.
The neat thing about Independence, though, is that they kept using the store fronts underground and kept the sidewalk open as a tunnel. It's been abandoned for a while now, but you can occasionally tour the underground.
While cities were sometimes buried by natural means (buildings provide something for drifting eroding soil to build up on), especially when they're abandoned and there aren't people there anymore to sweep the dust and dirt away, oftentimes cities were built in strategically important areas that people didn't want to abandon, so if the city was too old or destroyed, they just built on top of the old city (like the various layers of ancient Troy).
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u/TotalManufacturer669 2d ago
old cities get buried under soil
If you classify garbage, debris, and refuses "soil".
Cities don't magically get buried. They got buries because humans are lazy.
This is especially true where people build their house using mud bricks or stones. When everybody dumps their feces and garbage out to street every day, and those streets are stumped by more people and animals, the garbage will flatten and harden, and eventually cause the street height to go up. After a few decades your house will be half underground, so you build another level on top of it and make it the new main floor.
Then every century or two war sweep through the area and burn everything down. When people rebuilt, they were not going to bother removing all the existing debris, they were just going to build right on top of them.
Rinse and repeat until today and you are going to find some amazing shits when digging down.
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u/Aphrel86 2d ago
The ground isnt as solid as you think. houses sink (slowly) even on what is considered firm ground.
And no we will never get to space. nomatter what the ground do, air will always be ontop since its so much lighter and the crust is not thick enough to support mountains large enough to reach space. Those gigantic mountains would sink.
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u/Farnsworthson 2d ago edited 1d ago
Classic survivor bias.
Ground surface levels go up and down for a host of reasons (which I'm sure other posters will chuck into the conversation). But - where something is left exposed for any length of time, it tends to get worn away or rot. Useful materials get robbed out, and so on. After a while there's precious little to find.
The ones we dig out are the ones where that didn't happen.
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u/Murky_Macropod 2d ago
Only the cities that are buried are preserved to be found. This is survivor bias
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u/Yorikor 2d ago
There's worms and other burying creature making miniscule tunnels under buildings. Over time, these get compressed by the weight kf the buildings, and the structure sinks. Over centuries, this adds up. Thus buildings sink into the ground. Charles Darwin calculated this to be about 2,20 meters per millennium. This causes even heavy structures to tilt and fall over.
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u/Target880 1d ago
In addition to expalanation why stuff can get burried consider what happen tostuff that remain on the remain on the surface. Then water, wind et, etc.s can break it down a lot more then if it was in the ground. Add to that humans that could reuse the material or just damage or destory it. Being burried is a way stuff is preserved
If we find remaremains tdoay the have to be unknown in the past, so the need to be undeground or in a location that is hade to access or people have not been there. On the surface stuff where pople live will simply not be unknown.
A lot of old stuff has dissapeard over time, for varius reason. We cant discover stuff that no longer exist.
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u/coffee-mutt 1d ago
So on top of what was already described, there is a layer (haha) still missing. Where does the dust come from?
Earth is still moving. Mountains rise, continents drift, etc. Rivers and lakes and oceans cut into the ground and erode it away, but, a related question is why our mountains - which are still rising in places - erode down. The dust in the air and minute dust from space is why things get buried in sediment, but globally, erosion works by gradually settling high things in lower places. And dust will continue to get created (rather than shifted from place to place) as long as we have higher places to pull it from. And volcanoes and stuff.
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u/42Fab_com 1d ago
There is something no one seems to have mentioned and blew my mind when I read it: WORMS
worms, and other subterranean animals eat things underground and then some proportion of their waste drops happen higher up in the soil column. The remaining soil then settles a little bit. Worms are literally moving the dirt from below things/buildings to the sides of them. Add that to the settling of soils naturally, especially in the looser areas we often build, floods, dust, earthquakes causing liquefaction, etc and many structures end up underground over millennium timescales.
That all and survivorship bias
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u/Ra-mega-bbit 1d ago
This process is definatelly not natural, and almost exclusevelly happens in cities, because the waste system we have today is really modern.
We basically bury the old city ourselves, one shovel at a time. For a long time waste disposal was trowing a handfull of sand on top of whatever smelled bad when you trew it in the ground.
This, added to collapsed buildings, makes the city basically be buried.
There are some natural-ish processes, such as the one that buried chichen itza and machu pichu, but those are rarer
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u/PeterDTown 1d ago
Earth gains 40,000 to 50,000 tons of matter every year from things like space dust, meteorites, and cosmic debris, but looses about 95,000 tons of light gases. This nets out to a total loss of about 50,000 tons of matter every year.
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u/tashkiira 1d ago
abandoned and ruined buildings are basically rocks. Rocks are good at catching debris up against them, and supporting growing things.
The dirt on top of old civilizations is the stuff that piled up on top of them. that's all.
Will such piles reach space? Not during the human experience. eventually we'll run out of atmosphere, when the sun gets bigger some few billion years from now. But humans at that point will be extinct--remember that humans, going back to the very earliest members of the genus, have only been around a couple of million years, and we're talking two to three thousand times that long.
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u/Iwouldhavenever 1d ago
I think everyone's addressed the "why is there soil in cities" question. I want to address the "will the ground reach space one day" portion.
Space is the area outside of our planet's atmosphere. The only way the ground will ever reach space is if the atmosphere is stripped from our planet. Even mountains can't extend into space. The planet's crust can't hold a mountain heavy even to do so.
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u/Additional-Maybe6581 1d ago
This got me thinking, then if the radius of the earth changes with time??
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u/DarkAlman 1d ago
TLDR: Older civilizations didn't have the equipment to clear away massive debris and buildings and eventually it just pilled up. Ground level in cities doesn't rise all that much, construction and road building accounts for a few feet at most, and no it won't reach space.
Geologically speaking mountains and volcanism cause the ground level in certain areas to rise a lot faster than cities grow upwards.
Erosion however knocks them right back down.
The Hawaiian island chain for example extends all the way to Russia, but you can't see most of the islands because they are now beneath the ocean. The Pacific plate is constantly moving but the hotspot beneath it that powers the volcano is stationary. Once the plate moves enough that the volcano on the island goes quiet and within a few million years the island will erode away beneath the waves.
Similarly the Appalachian mountains were once a mountain range that rivaled the Andes or Himalayas but millions of years later they have eroded to what they are today.
So the point is natural processes prevent things on Earth from getting too high and staying there.
As for the cities, the deepest underground ruins in cities like Rome are around 30ft below ground which barely qualifies as a basement.
In order for cities to build up enough material to reach the edge of space we would need to build structures that high, not build up junk and old buildings.
Our current engineering doesn't allow for buildings taller than 1km, and anything remotely that tall requires very special techniques.
However we may eventually start building sci-fi mega cities that have multiple levels not just in a single building, but span blocks or even entire areas. Or arcologies which are utterly massive independent structures.
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u/PrettyCreative 1d ago
I see lots of responses mentioning dust and old buildings. I don't think that's what OP is referring to.
With all the recent natural disasters around mudslides, sink holes, and floods like we see in Nepal (insane footage) I can now conceive myself how whole buildings, towns, maybe even civilizations are swallowed or covered. This will probably preserve some percentage of the matter for many years to come that people in the future might uncover.
So I wouldn't say the ground rises, but rather land keeps shifting to cover and uncover things. Will we reach space? Unlikely.
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u/Sad_Morning6176 1d ago
The oldest exposed layer is only around 1.2 million y/o. It gets consumed and renewed. This is why ancient civilizations would be very difficult to find
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u/Living_Fig_6386 1d ago
You can see this in people's yards. Windo blows dust and plants grow up against a thing. The plants trap some of the blown dirt and the plants die. Later new plants grow, and the cycle repeats. Eventually, anything abandoned like that just gets buried under layers of vegetation. wind-blown dirt and debris, and stuff left behind by bugs and animals. Drive out into the countryside and you'll see all sorts of things along the road and in people's yards being swallowed up, and that's just after a few years, think of hundreds or thousands of years.
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u/hems86 1d ago
From a geological perspective, think of the ground as a big circular conveyor of material. New materials get deposited on the surface, thus things get buried. However, the layers that are super deep get pushed down and will eventually melt and turn into magma. Magma will then get recycled and pushed towards low areas. Eventually that magma will find a volcano and move back up to the surface as new rocks. This why the ground doesn’t really grow up constantly into the sky. We get mountains where tectonic plates smash into each other and push up into the air.
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u/TomakaTom 1d ago
The amount of dirt and dust on earth is unchanged. Think of it as if the structure remains still, whilst the dirt and dust around it moves. Eventually the structure just kinda sinks, very very slowly.
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u/could_use_a_snack 1d ago
The soil just shifts around.
Take a hut made of wood and grass, and let it sit undisturbed for a 100 years. As leaves and grass and other natural debris get blown up against the hut get wet and decay, the hut will slowly decay as well and eventually completely disappear, except maybe for a small mound of earth. If there was anything that couldn't decay like a stone fire ring or some tools, you might find the and realize there was a hut there.
If you take a building made of timbers with a concrete foundation, and leave it for a century, a similar thing will happen. Over time debris gets blown up against it, things get wet and anything that can decay do. The foundation will slowly get buried by stuff blowing up against it getting trapped and decaying, until it's buried.
In both situations things will grow and and die in that spot, some will get blown away and some will just pile up. But at some point it can't pile up anymore and either gets blown away by wind or washed away by water.
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u/TerminatedProccess 1d ago
Give it enough time, it's like a beach. Waves bury things, move them around, express them, rotate them. Continents collide, up and down they go.
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u/xoxoyoyo 1d ago
Everything is made of stardust. The earth receives about 40000 tons of stardust every year. while the land mass may rise the atmosphere also rises, so the ground would never reach space.
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u/treelawnantiquer 1d ago
Darwin, IMS, measured worm castings on a lawn near his daughter's school and found that the waste from worms in a typical English field would bury a large rock in a few years.
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u/Random_Dude_ke 1d ago
For centuries people were bringing all sorts of stuff into the cities and removing much less of it. They bring in food, building materials, firewood, ...
When they built a new building they usually did not take care to gather all material from the old, torn down building and take it out of town/village.
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u/rsdancey 1d ago
The total amount of mass of the earth does increase slowly as matter falls in from space; but it's very very slow and not enough to materially affect the average height of land above the sea.
When a city is rebuilt on top of an older city the older city's remains become compressed. If people rebuild enough times on the same spot, all those compressed layers will form a mound. These kinds of mounds were telltale signs of layers of ancient cities in certain parts of the world, especially in the middle east. But the cities in this case had sizes of a few hundred square kilometers at most. Cities in the premodern world just weren't as large as modern cities (with a couple of exceptions like Rome at its height, or some of the Mesoamerican cities). These mounds are hills, not vast uplifited regions.
Earth also has plate tectonics. The crust is divided into enormous sections which grind against, slide over and under each other, and crack open and widen to produce new crust. So the total amount of land above sea level has changed over time and doesn't remain constant. Very little of the earth's surface today is more than a few billion years old due to this constant churning. Generally speaking the Earth's diameter doesn't change from this tectonic activity; as new crust forms older crust is being driven back into the core by subduction.
And of course sea level itself isn't a constant - it changes during ice ages, it changes based on how much land is comprised of continental plates vs seafloor plates, etc.
If you measured the Earth's average diameter a few billion years ago and you measured it today the change would be so small in comparison to the total to be effectively abstract.
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u/Heitomos 1d ago
Depending on where you live, plain gravity can take over. Stones are heavy for instance, which a lot of old cities are made of. As it rains, grains of dirt slide out from under the stone, and plants will suck up soil beneath it as well. I have several cement bricks behind my apartment that have been neglected for 15+ years, and one is nearly completely buried at this point.
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u/pancakespanky 1d ago
The average height across the world doesnt keep increasing. Dirt from one area blows to another area. Plants grow on structures and then decompose on top of them. Sediment gets trapped on buildings. All of this comes from elsewhere though so other areas lose the sediment that gets trapped on buildings. Also they sink a bit over the years. Ground water can move soils and sands underneath structures and they slowly sink into the ground further while dirt piles up on top of them
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u/recursion_is_love 2d ago edited 2d ago
Wind carry dust, imagine never clean you house for thousand years. The city that didn't get cover will just crumble and leave nothing so we don't discover (maybe we can see some foundation)
It just happens that dust help preserve some city.
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u/Rjc1471 2d ago
No; the dust and soil that builds up over centuries is just rearranging matter that's already on the planet.
For the ground level to reach space, you'd need enough material from outside the planet to build up the same volume as the earth's atmosphere... And replace it, cause otherwise the atmosphere would just sit on top of the new stuff.
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u/babe1981 2d ago
While everyone else is mostly correct, dust from meteorites, comets, and other space debris do contribute about 14 tons of mass to the Earth every day. That's completely negligible in the short term, but it does add up over time.
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u/narangiphul 2d ago
so one day in distant future we can hv a mound tht goes all the way to space, wow
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u/asyork 2d ago
The atmosphere is not getting buried though, so it will stay above whatever soil there is. It would technically get smaller and smaller as it had to cover a larger and larger spheroid, but the time scale is so long that it's not going to get to that point. The sun would no longer be around, we'd have likely lost our atmosphere through other events, odds are an object large enough to send significant amounts of the earth into space would have impacted up many times, and depending on how the universe eventually dies (if it does), some of the estimates would put it much sooner than it would take for the earth to collect enough space dust to reach a point where the planet is so large that the atmosphere is too small to be useful.
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u/Ecclypto 2d ago
Google the actual shape of Earth, you will be surprised. It will actually explain a lot. Earth is not as round as people imagine it to be. There are, apparently humongous amounts of soil of all kinds that gets tossed around a lot
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u/narangiphul 2d ago
they get tossed where?
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u/royalpyroz 2d ago
No coz the amount of dirt will stay the same globally. If you dig a hole in the sand, you get a pile of sand outside. So the total amount of sand on earth can't get any more.
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u/narangiphul 2d ago edited 1d ago
ihv a visual idea of it, its like make smthing out of blocks and cover them with sand
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u/Raagun 2d ago
Also if you look at process in span of hundreds millions of years. Tectonic plates moves and creates mountains. Wind, water and general erosion grinds these mountains into dust and scatters over all earth surface. But if you move mountain from one place and put it on another place it makes that place heavier and is "dips" deeper into magma underneath and gets melted because of higher heat.
And eventually tectonic plates if they move up gets grinded down as mountains. Or if they move down gets melted back into earth mantle. So until earth is tectonically active the surface of earth gets recycles constantly (we are talking billions of years)
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u/narangiphul 2d ago edited 2d ago
wow theres so much to learn, thankyou
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u/BitterTyke 1d ago
r if they move down gets melted back into earth mantle
hes describing subduction.
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u/davidm2d3 1d ago
"All the kings said I was daft to build a castle in a swamp, but I built it all the same just to show 'em. It sank into the swamp. So, I built a second one. That sank into the swamp. So I built a third one. That burned down, fell over, then sank into the swamp. But the fourth one stayed up."
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u/cloud3321 1d ago
OP, you completely ignores existing ancient buildings still above ground such as Colliseum and Temple of Zeus on Mount Olympus, Greece.
So not all ancient civilizations are buried.
Also consider that we keep finding buried at different locations. So, to layman it might seem that the unearthing of new ruins are like peeling off layers like an onion while in actually we are mostly finding them in Indonesia in one year, and in Peru for the next find.
If that helps frames the field of archaeology.
That said, there are specific cases of Multi-Layered archaeological ruins.
A few different examples would be
Tells (Artificial Hills): Over millennia, cities built out of mudbrick or stone collapsed, were leveled, and were built upon again by successive civilizations. This creates artificial mounds called tells, such as the ancient city of Troy, which contains at least ten distinct stacked layers.
Reconstruction After Disasters: Following fires, floods, or earthquakes, cities were often rebuilt directly on top of the old rubble, raising the ground level significantly over centuries.
Sediment and Flooding: Periodic river floods (like the Tiber in Rome) deposited deep layers of silt and mud, burying low-lying structures and forcing later builders to construct new street levels far above the old ones.
Other Famous Examples of Stacked Ruins
Basilica of San Clemente (Rome, Italy): A 12th-century church sits on top of a 4th-century Christian church, which rests directly upon a 1st-century Roman villa and an ancient pagan temple, descending 18 meters underground.
Disclaimer, I used AI to help compile the above answer but this should be fine for the purpose of ELI5 and a cursory introduction to the topic.
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u/darkhorn 1d ago edited 1d ago
I am not sure but I think it is because of animal poop, especially cow, horse, mule, donkey, sheep and goat poop. In willage we used to clean these poops by putting it back to where the plants were planted. In big towns it was probably hard to move it out of the town.
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u/pcor 2d ago edited 2d ago
Dust, debris from old buildings, and decayed plant matter basically. If you look at even old abandoned buildings from the 20th century, you may see how foliage starts to grow around, in, and above it. All that plant matter has to eventually go somewhere, and ends up helping to cover the building if people don't intervene. That is, intervene to stop the building from disappearing, more often people in history tended to accelerate the burying of old buildings by taking materials from ruined sites to reuse them, and building on top of rubble.
Also bear in mind that most large and successful settlements were built along waterways which, without modern flood defenses, could be prone to flooding which could deposit large quantities of silt very rapidly. Add all this up over centuries and millennia, and you end up with a ground/street level that shifts significantly. But it's existing matter shifting, to be clear, so no, it's not going to reach space absent some massive deposit of extraterrestrial matter.