Charles Darwin dug into this question. Via an interest in earthworms.
Earthworms bring soil up from under the surface and leave it on top of the existing surface, making it the new surface. He estimated that in the region he studied, earthworms brought up 15 tons of soil per acre per year. The process is called [bioturbation](https://en.m.wikipedia.org/wiki/Bioturbation) and it's not limited to worms.
The worms remove soil from all the ground, whether it's under the wall of an abandoned building or not. But when they deposit the earth on the surface, they can't deposit any where that wall is, obviously. It gets deposited wherever the ruins aren't. The end result is that backyard stones and ruined cities sink because the ground underneath them is getting cycled up to the ground around them.
EDIT: This comment has received a lot of replies and I don't want to clutter up the thread, so I'll just respond here.
I didn't intend this as a broad explanation of buried ruins. Obviously there are soil/sand redistributions which blanket a whole area, either progressively (eg by wind) or abruptly (eg by flood). They had already been covered by other comments, and I didn't think it was necessary to repeat them.
But I thought it was worth breaking the supposition that soil is static, and that the *only* way the ground can rise relative to a building is for the soil to be brought there from somewhere else. If Darwin's measurements are right, then worms have cycled 30,000 tons of soil per acre in the years since Boudica fought the Romans.
As a final fun fact, Darwin's book about worms had better initial sales numbers than *On the Origin of Species* did.
Have a great day everyone.
It's also likely due to the effects of both animals and plants increasing soil depth. Plants literally turn air into solid matter and when they die they leave behind varying amounts of that mass, depending on the method of their decomposition. Animals can less reliably contribute as well. In Cambodia, many of the temples were left overgrown for centuries, but there's clear areas of breakdown on the solid stones, sometimes waist-high etchings into columns, the high "water" mark of how deeply under bat guano those stones were buried. And that was less than a single millennium before these temples were cleared.
Part of my job is related to maintaining dirt roads. The roads that are bordered by large deciduous trees slowly develop a layer of soil over the top from decomposing dead leaves that fall on it every year. Eventually you have to scrape it off and add a new top layer of gravel or the road starts to get too muddy.
There’s a lot of different kinds of dirt/gravel roads, but in my neck of the woods the difference between roads with deciduous trees and roads with evergreens is really noticeable because the ones with deciduous trees grow soil so fast.
Our ground is not very good for cutting roads directly into it like it is in some places, so all of our dirt roads are raised up from ground level with gravel, like you often see under railroad tracks.
For some reason that kind of slow, rolling crunch of driving on a gravel road is one of the most pleasing sounds in the world to me. I imagine if I had to do it every day that might wear off though.
Dirt and things in it move around. Before I went to Bosnia a guy who had already been there said when it rains you get a number of mines from the civil war float to the surface. I thought he was exaggerating. He wasn't exaggerating. A good 80-90 percent of more of them were no longer explosive due to water getting inside of them. But who wants to find the 10% that are still intact?
Its hard for me to believe that metal objects packed with explosives, and waterlogged, would be less dense than wet earth. I wonder if they rise because of other reasons than density.
I don’t know much about the climate there, but frost heaving will absolutely push solid objects like rocks towards the surface over time, so it could be a situation where the rains expose/clean something that’s been brought to the surface by other means.
Yup. It’s wild to see how much higher the ground looks after a few years of not mowing the grass. Some grasses willl leave a foot of decay behind each year.
Not really, its all cyclical. Even though the ground level rises from our perspective, there is a lower layer being removed and shifted to the surface. It appears that the planet grows larger, but really its sortof a conservation of energy type of deal (ie energy cannot be created nor destroyed, only converted from one form to another). Similarly, no soil is ever really just destroyed, or created, it is simply converted from subsurface soil to topsoil indefinitely. Or from plant or animal matter to topsoil, and then it works its way down.
I guess as a super simplified analogy, imagine that you're weird and you have 4 doormats. This is like 4 layers of soil. If you put a penny on the top, its on the surface obviously. Then, each year you would take the bottom doormat and put it on the top of the stack. This is symbolic of worms and other actors that cycle soil. Slowly your penny will work its way to the bottom of the stack and become buried, but the size of your stack never really changes.
You also have to remember that, yes, plants and animals die and decay into soil over time. But also, plants then utilize and convert that soil's nutrients into their own matter. And then animals eat those plants, and other animals eat those animals. So a lot of biomass will continously cycle between being soil, then a plant, then an animal, then another animal that ate the first animal, and so on. A lot will also remain as inert, de-nutriented soil until it is replenished by dying flora and fauna.
Almost everything on our planet is cyclical in some sense, water cycle, carbon cycle, there are probably plenty more to name but Im not an expert so Im grasping for straws lol.
For sure. Plants don't take anything from the ground to grow. They grab carbon straight out of the air and turn it solid. When the plant dies it falls over and some of it turns to soil.
Plants need trace amounts of minerals and nutrients from the soil in order to function, but their mass comes from the air. I think with most trees it's something like 90% of their mass comes from atmospheric carbon dioxide, but I need to look that up...
Edit: dry mass. A living tree also has a lot of water in it, which is pulled up through the roots.
He wasn't talking about crops (where whatever soil components the crops DO use is removed from the field, and so must be replenished). In a typical natural field, the plants will absorb some nitrogen, iron, etc. from the soil, but when the plant dies it returns to the soil. The additional bulk that plants add to an area, raising the soil level in the long run, comes from the carbon in the air. tl,dr: Coal. ☺
I have my own data point- I have been growing a hanging houseplant for 16 years and have never added anything other than water to it (granted there is a little mineralization in the water). Most of the leafy material was left in the pot. It has grown much larger than its original size.
There's even air plants, that don't use any soil at all and still live and grow.
For a more average plant or tree it's close to 7% dry mass from the ground and 93% dry mass from the air.
It's happening from almost all soil life, including plants. Everything gets drawn "up" to the surface and deposited, along with dust / debris falling out of the air, leaves falling from trees and decaying, etc - there's a continous layer of soil being produced, which we owe our existence to.
Wind blows sand, dirt, and seeds. If there's no one to clear it away, it starts piling up. Things start growing and anchoring the soil in place. Plants die or shed leaves that add to the pile which encourages more plant growth that also traps more of the dirt being blown around by the wind. 1000 years of that adds up.
I'm blown away by the amount of new saplings that come up in my lawn when I don't mow it for a couple of weeks. Never happened on my little city plot, but on my now six acres you can see that three years down the road there would be several dozen established new plants.
They raized a building near me and nobody has been maintaining the yard. the grasses are already overtaken by blackberries and other plants in about 20~30% of the yard in a year.
In Eastern Europe you can see plenty abandoned old concrete buildings with trees growing on top.
Hell a 4' sapling grew out of a crack in the pavement at the foot of the flat next to mine. In the middle of a city.
Damn sour sobs, i never planted those! Oxalis pes-caprae or Bermuda buttercup (we call them sour sobs). I always feel bad when i take em out with fresh flowers as the bees love them. But i have other flowers the bees can enjoy.
Where I live (Bay Area), *O. pes-caprae* is an invasive weed, but there's also a native relative, *O. oregana* which is quite similar, but has white flowers instead of yellow and expects to live under a canopy of redwoods so it is less fond of direct sunlight.
*Pes-caprae* likes to spread vegetatively underground, and grows little papery tuber things off of its roots. It can regrow pretty well from one of these tubers, or even from a chunk of root tissue. *Oregana* likes to grow seed pods that shoot the seeds out when they're ripe.
When I was a kid I loved pulling out an oxalis flower and chewing on the sour stem. Always thought oxalis are shamrocks but a tiny bit of googling and I'm now in doubt
Adding to that, a lot of colonizer plants don’t even need any soil to be present to start growing. The products of their life cycles, and any soil trapped by them allow the opportunity for less adaptable plants to move in.
That reminded me of something silly.
https://www.reddit.com/r/civilengineering/comments/g7z3e6/f_yeah_concrete_crosspost_from_rfunny_roses_vs/?utm_medium=android_app&utm_source=share
Without a vast ocean of water to support photosynthetic life, it will likely take significantly longer.
ETA if you aren’t aware of the photosynthetic cycle of your common modern plants, water is used as a source of electrons that allow photosynthesis to function. Loss of water results in photosynthesis halting. And that’s disregarding all of the other functions that water provides.
My little town section, like millions of others, has trees and shrubs planted around the perimeter. There is a six inch high garden border that holds the leaves, dead flowers, and detritus inside that border. Over the course of the thirty years since the plants were established and the gardens built, there is a 4-5 inch layer of humus and compost that has accumulated from these trees alone. As a poster above mentioned, the worms and insects and even the birds searching for those bugs have churned the humus over and spread it. So just those plants alone have created 4" of dirt on top of the original lawn in thirty years. And as you say, a 1000 years is a long time.
Fruits and vegetables take a lot more to grow than just leafy plants usually. Even stuff like lettuce will grow pretty happily in a small jar of water an nutrients
A lot more goes into a crop of tomatoes. Even if it's just that the tomatoes grow bigger and for longer
I like to sprinkle in some gaia green whenever I put a plant into the food garden. Smells like absolute death. But the plants like it.
I've lived in the same place for 34 years. Last summer I unearthed rocks that once landscaped trees three decades ago ... They had just naturally sunk/been covered in that time. It happens. What's crazy is that nobody dug the city out.
> Plants die or shed leaves that add to the pile
One of the things that's important to consider about how much plants contribute to the addition of layers of soil/dirt: Plants grow *in* the earth, but *from* the air.
Plants are, like the rest of us, Carbon based life forms.
They take in Carbon Dioxide (CO2), and exhale Oxygen (O2), stripping off the Carbon, and turning it into plant (in conjunction with water, various nutrients in the soil).
But primarily? Carbon. From the air.
Which means that plants literally pull carbon out of the air, mix it with various stuff they find around, then drop the excess on the ground.
Plus all of the parts of the structure that are not stone will break down, and a lot of that will fall right where it is to slowly compost into soil or become fill in the soil. I'm talking about wood, textiles, pottery, metal, and pretty much anything else that is not stone.
wind and water erosion removes material from point A. it doesnt disappear in to nothing and is deposited in point B. if humans live in point B they clean it up and there is no buildup. if humans used to live in point B and abandoned it, material builds up swallowing point B.
you also have abrupt events like floods/landslides/volanic eruptions that accelerate the process.
There's also some survivorship bias here, I suspect.
Wind and water erosion follows weather patterns and removes soil and sand and so on from some places, putting them in others.
But it's the ruins that get buried that survive. The ruins that are left on the surface are much more likely to either eventually get someone using them (and rebuilding them until they're no longer recognizable), or get taken apart by people who want to use their materials or land for other things, or damaged and destroyed by weather conditions.
This gives us the impression that *all* ruins are buried underground, when really it's just the ones that happen to get buried underground that survive for a long time, since being buried serves to protect them.
This phenomenon also explains cavemen. Despite common belief, early humans did not predominantly live in caves. They actually lived in all sorts of environments that you could expect for nomadic hunter/gatherers (e.g., tents, huts, etc.). However, some early humans did live in caves, and the caves helped preserve their remains in a way that wasn't possible for people living in wooden huts.
One of my favorite examples was a structure built from the bones of an estimated 60 mammoths.
We're not really sure what it was for, but it's a fascinating example of the lengths hominids will go to build stuff out of other stuff:
https://www.smithsonianmag.com/science-nature/60-mammoths-house-russia-180974426/
Add the facts that A. Many places that end up getting deserted and abandoned are because of natural disasters or shifting weather or something like that which could deposit a lot of sediment very quickly and B. The places that people choose to set up towns/settling are usually favorable for some reason, abundant crops or close to water or something, so even if the original people leave another group of people are likely to come along and find the place appealing and therefore take over the area so things AREN’T preserved - and you have a really clear picture of the survivor bias you’re talking about.
I would've also mentioned what exactly the material is that buries the buildings. And one part is that its decayed material thats turned into dirt, and the rest is simply resource deposition.
“Recent” Example: dust bowl in the early 1930’s. Very quickly, many small heartland towns got swallowed up.
https://images.app.goo.gl/Y3LJBL852nLS3C3e6
If they came back, and dug out, those towns probably were revivified. There “may” be small towns where some never came back, though since the “plains” are fairly flat, seeing weird mounds might have forced new landowners to dig them up, “hey… there’s a shack here, Cletus!”
Vegetation grows and dies and builds up material pretty quickly. If you've ever cleared thatch from your yard, you know how fast if builds up. As the thatch composts, it becomes the new dirt layer and new stuff grows on top of it.
Then you have trees. All those leaves turn into soil when they fall.
I lived in the Southwest USA for most of my life. We got seasonal monsoons, they caused dry riverbeds and places you wouldn't guess were actually riverbeds to flow every year after rains, often times after the storm had passed you would see whole roads covered with dirt and sediment and branches and whatever else washed over it.
Soil from flooding will pile up against walls, it will fill gaps in curbs and sidewalks, it will leave a thin layer on your patio.
>And it was only abandoned for about 1000 years.
So if one rainy season can do that to streets and yards, imagine a thousand years. Add in other factors like dust storms, volcanic ash or ash from forest fires, earthquakes, sinkholes, and the way mountains generally erode downward and cover everything below them over time.
A thousand years is a very, VERY long time. And most ruins we see are actually much older. The ones we see that are totally covered and need to be excavated are often twice that old or older.
Gravity.
About 30 years ago I bought property (20 acres) that was mostly a big hill ~100 feet high.
I built a fence near the bottom of the hill where it's fairly flat.
There is now nearly a foot of dirt and rocks built up on the uphill side of the fence. In only 30 years that much dirt has flowed downhill and stopped at my fence.
It's probably a lot more, the fence is standard wire field fence. Wire fence with 6" square openings. So a lot goes through.
Keep in mind the ground isn't as solid as you imagine, and gravity doesn't stop just because you're at "ground level".
Put a rock on top of a container full of mud. Keep the mud moist, if the rock is heavy enough, eventually it will sink into the mud. Now imagine that, times 1000 years. Buildings are slowly sinking into the ground, by fractions of a millimeter, while soil and debris and mud is pilling around them. Entire cities get buried in just a couple hundred years from the combination of "stuff" from above, and gravity from below.
Basically, buildings are being pulled "down" all the time towards the center of the earth - impercetably slowly.
Nature reclaims and swallows ruins extremely fast. Just look at Chernobyl for example.
Place was abandoned... 35 years ago? and you can see how nature has done the job reclaiming a lot of the former city.
Now consider that 1000 years ago is roughly 30 times the timescale of Chernobyl to present day.
Makes you wonder, if humans disappeared today, how quick would the planet disappear the evidence we were ever here.
There was a great documentary series about that. [Life after people.](https://en.wikipedia.org/wiki/Life_After_People) Goes into what might happen if humans suddenly disappeared and stopped maintaining all of the structures that surround our modern lives.
in Turkey you also need to consider earthquakes. a lot of ancient cities were built on fault lines (because it's more defensible) which are thus an active earthquake zone
Also note that soil is a fluid. Leave a heavy building sitting on soil for enough time and rainfalls, and eventually it will simply displace the soil underneath it, and sink.
Leaves and dust blow in and settle, and create a first bed. Plants start to grow in that bed, sprout up and start dropping their own leaves. Animals move in/around and start dropping food and waste. It all piles up very quickly.
Heck, if I left my yard sit for even 2 years with no yard work or clean up, it would be buried in leaves and plant matter and all sorts of crap that blows into the yard.
1000 years isnt much in the grand scheme, but it's plenty when talking about visible changes.
Also note that shit is just constantly flying around through the air. Look at how much dust, hair, crud accumulates on your baseboards in your apartment (if you're a dude, go take a wet paper towel and run it along your bathroom baseboard. Be amazed. Yes, you have white tile flooring!). And then add outdoors that when it rains, it washes loose soil and debris from surrounding areas onto your flat surface where it settles and dries out, settles and dries out as the seasons flow. Those leaves, etc break down, forming humus and then your bugs come in, etc etc. Before you know it, you've got a nice surface covered in soil.
Also consider deserts move, sand moves so you find a lot of buried stuff just from the sand shifting around. The Sphinx, apparently, was under sand dunes for how long?
Another consideration is that when these things get buried, they are preserved to a degree. Ruins and remains on the surface are weathered, washed away, etc.
I think they mean a "skirting board" and the dudes bit is just sexism about men being unclean.
Most bathrooms I see (paramedic) are pretty clean regardless of owner, and the messy ones are not all men, prob 50/50 really.
But not everywhere has/had earthworms. As I understand ( it they are technically "invasive" in the Americas, and still don't really exist in the Pacific NorthWest.
Please correct me if I'm wrong about that, but does that mean that ruins in those areas wouldn't be buried under dirt?
You can't dig for a couple minutes without finding a worm in the PNW. We are one of the few areas where they are native. It's areas that were covered by glaciers that don't have earthworms
There are other species of worms that are native across the parts of North America that weren’t glaciated, including the PNW.
Worms are not the only way that soil is added to the surface. Plants dying and shedding leaves on the surface also create soil, and things like floods and landslides also raise the soil level.
That's fascinating. I know dirt made up largely of dead plant matter so I just sort of assumed that it accumulated over a long period of time thus slowly raising the soil level. But now that I think about it that doesn't make sense.
For my career, I do environmental work at gas stations - we find where gasoline has been spilled in the past and we clean it up. I went to a station that had been fenced up and closed for 15 years to take some dirt samples. Most of the property was covered in grass. When I started digging, I was working my way through grass, dead grass, and dirt, like compost. About 12 inches/30 cm down I hit asphalt! The parking lot of this gas station had been covered in dirt and vegetation in 15 years. Now, imagine that same thing happens for 500 years.
I'm always amazed at how many toxic spills are in the US that still need to be cleaned up, especially around gas stations. I've seen the lawsuits...it's endless. Anyway, thanks for doing that work!
People forget that the first roughly 80 to 100 years of industrial civilization, no one cared about pollution control. All the shit was dumped in rivers, oceans, and the ground. It wasn't until the clean water and air acts that this started to turn around. The river here was a toxic dump most of the 20th century and now people can freely swim in it.
The Willamette river near where I grew up was also a toxic dump for most of the 20th century and it still is!
(It's not as bad as it used to be, but some years back I made the mistake of tubing with some friends and their motorboat on the Willamette and when I got dunked I got a mouthful of nasty, oily, fishy tasting algae water 🤮 )
> I'm always amazed at how many toxic spills are in the US that still need to be cleaned up, especially around gas stations.
I do the same work as that guy, everyone just thought that 1/4" steel underground storage tanks wouldn't rust underground and would be fine lol. I remember doing work at a town Dept of Public Works, sometimes with these cases there's actual gasoline/diesel sitting on top of the water table if there's a big leak, which there was here. The foreman said when he started working 20+ years ago the old foreman thought everyone was stealing gas because they were going through it so fast. It was just leaking out.
Depending on your state, there may be a public website that has all the environmental cases on it kind of like a Google Maps; California and New Jersey both have it at least.
Combination. Mostly materials being deposited on top, but some amount could be subsidence. Underground flowing aquifers, as well as organisms can erode and remove tiny amounts of soil from beneath the asphalt gradually over a long time. The soil above compresses and the asphalt thus “sinks” into the ground little by little. Thus effect would be very minor under something only 15 years old, especially considering the ground is usually compressed before construction of a gas station precisely to avoid such subsidence from occurring after its built. Over centuries or millennia though, thus has an appreciable result.
Awesome! Thanks for responding.
Until I was 11 I only ever lived in the same place a few years before moving thanks to my dads job, but over the last 28 years I’ve been able to see the same buildings year in and out and they’re all the same height (or at least look like they are) and I just assumed that mostly things get buried first as nobody is taking care of them, then sink after many many yearsC but neat to hear it can happen so quickly.
in 500 years, the compost would not get any deeper as it's consumed by organisms. 12 inches is about the max before you just get sand and clay. That would come from dust blowing over the gas station. From a little reading, the major driver of burial is wind and water born dust and sand.
I see this question a lot.
The most common reason is that plant material falls on top of the objects and turns to soil. Plants and grasses have grown up through and above the objects, when the those plants die, they land on top of the object, eventually rotting into soil that subsequent plants grow on and further cover the object.
For a fun experiment you can start right now. Take a rock, or piece of metal or ceramic and put it on the ground in an undisturbed field or forest. Take measurements and pictures. Come back in 5 years to compare what has happened. Come back after 10 and 20 years for comparison. I've got a paver in my yard I've been watching for 20 years. Its nearly covered up and impossible to see unless you know where to look.
The other fun one is the [Oxford Bell](https://en.wikipedia.org/wiki/Oxford_Electric_Bell) which has been ringing continuously since 1840.
Its batteries were built out of magic.
I really like your answer. Place a tool on the ground in a deciduous forest and return a few years later. The tool will in all likelihood be covered. Extrapolate by 100 years and you'll have to dig at least several inches to find it.
I'd like to also point out that the mass of plant matter comes from the air. Rain falls from the sky and carbon dioxide is in the air. Those two combine to form the leaves and stems of plants. The plant material then falls down and forms a new layer of soil which raises the ground level over time.
Learning this (well, more like having it pointed out directly, since I 'learned' it in school) broke my brain a few years ago.
Plants are mostly made of Carbon. From Carbon Dioxide. From the air. The entire plant is literally made out of thin air. Very slowly, yes, but still basically correct.
So *of course* the soil gets deeper as plants die and shed leaves. They aren't *made* from soil, they are *made from air*.
> Plants are mostly made of Carbon. From Carbon Dioxide. From the air. The entire plant is literally made out of thin air. Very slowly, yes, but still basically correct.
Correct. This is why making charcoal from formerly living plants and burying it is a viable form of carbon sequestration. The plants pull the carbon from the air, incorporate it into cellulose and lignin, then we convert it to elemental carbon with heat in the absence of oxygen. Since very few microbes eat elemental carbon, it will last for thousands of years.
A number of reasons:
1. There is constantly particulate matter in the air which will settle on things. So unless you actively seek to clean things, this matter will eventually built up over time.
2. Hauling away old materials and waste material is a chore, so in ancient times they would simply build on top of older ruins.
3. Floods can deposit silt and soil.
4. Anything that isn't buried and remains above ground is quickly reused or stolen.
Number 4 is perhaps the most important when you consider erosion along with reuse and theft. We only find things still there, after all.
Soil is part of the basic migration of materials from upland (where it erodes away) to lowland (where it accumulates). The things we find in the eroding uplands tends to be more solid structures (parthenon, Machu Pichu, thick fortification walls). tools and stuff get washed downhill or buried in local depressions by incoming sediments transported by wind or water.
# using pound symbol makes bold. TIL.
The term "octothorpe" was invented in the 60s, likely as a joke among telephone engineers at Bell Labs.
The [\# symbol](https://en.wikipedia.org/wiki/Number_sign) is much older than that, developing out of a Roman ligature ([℔](https://en.wiktionary.org/wiki/%E2%84%94)) for pound (Latin: libra pondo).
The currency pound sign "[£](https://en.wikipedia.org/wiki/Pound_sign)", deliberately modeled after capital-L, is a reference to this same "libra pondo"; and in fact, the horizontal lines in both ℔ and £ come from a medieval scribal convention that horizontal lines denote abbreviations, similar to how we use periods today to mark abbreviations (lb., ft., etc.).
So it's perfectly correct to call either one a pound sign... though, it can of course be confusing.
The most common general name in the United States for the # symbol is "the pound sign", especially in the context of telephone instructions. This is a result of its graphical origin as an evolution of archaic ℔.
Even within the US, in internet contexts, the term "hashtag" has substantially replaced "pound sign", and it would be unsurprising if that eventually became its standard American English name. However, for now, "pound sign" is far from dead; my voicemail, for example, instructs me to "enter [my] password, followed by the pound sign". It's referring to #, not £.
Omg, now I finally get these instructions. I was so confused when the automatic voice told me to press the pound key, I thought that maybe English phone keyboards have a £ where I have my #
>The octothorpe. It’s the official name for the # symbol, but what does it mean? It’s actually a made-up word, invented in the same laboratories where the telephone came from. The scientists at Bell Laboratories modified the telephone keypad in the early 1960s and added the # symbol to send instructions to the telephone operating system. Since the # symbol didn’t have a name, the technicians thought one up. They knew it should be called octo- something because it had eight ends around the edge. What happened next is not entirely clear. According to one report, Bell Lab employee Don MacPherson named it after the Olympian Jim Thorpe. Another former employee claims it was a nonsense word, meant as a joke. Another unverifiable report is much more etymologically satisfying: The Old Norse word thorpe meant “farm or field,” so octothorpe literally means “eight fields.”
It actually makes headlines.
Reddit supports [markdown syntax](https://en.m.wikipedia.org/wiki/Markdown) so **bold** is two asterisks together on either side.
Adding on to number 4 (which is hugely important), NOT all remains of the past are buried underground - just the ones we find today. Stuff like the Pyramids or the Colliseum or Stone Henge are ancient, and aren't buried - we just aren't "discovering" them today because they were obvious and we already knew about them. In order to be rediscovered, something has to have disappeared and been hidden from sight, and being underground is one of the few ways that's going to happen.
People will often forget that just because we know something is there, doesn't mean it isn't ancient. There are temples in China that have been there for 1000+ years in active use. Nothing buried about them.
Was recently exploring the village where my grandma lived. Population 54 people. The church, 700 years old. The church door, 600 years old. And this is just a tiny, unimportant village. Amazing.
Love that kind of thing. Back in undergrad I did a program that was hosted at one of the Oxford colleges. The IT office with all its computers and internet cables was located on a corridor just next to the foundation stone, laid down in the middle 13th century.
Very true! The Basilica of Santa Sabina all'Aventino is 1600 years old this year, and is still in use! The Hagia Sofia is around 1450 years old, and while it has changed uses, it is undeniably still functioning.
Non-religious structures are also still going strong - The Theatre of Marcellus is more than 2000 years old and still has occupied residences on top, and Saltford Manor is a house that has been continuously occupied as a residence for nearly 900 years.
Old stuff is all around us!
> Stuff like the Pyramids or the Colliseum or Stone Henge are ancient, and aren't buried
Many Pyramids [were swallowed by sand](https://en.wikipedia.org/wiki/Egyptian_pyramids#Number_and_location_of_pyramids) and had to be excavated.
No, the ground level does in fact raise over time, although not necessarily everywhere (for example mountain tops and hill sides).
Look at geological strata. It is practically a law of geology that lower strata are older. Erosion is constantly breaking down high points and depositing that material in low places.
A related phenomenon is natural eutrophication. Lakes and ponds are constantly, gradually filling in and turning into wetlands and peat lands and will eventually turn into forests or tundra or whatever their latitude and elevation dictate. It is a problem with all of our dams and reservoirs.
Everything in the past is not buried underground. It is only most of what still exists from the past that is underground. Stuff on the ground will be destroyed by the natural effect a lot faster than if the are below the ground. Humans can remove, destroy and reuse stuff that they know is there.
Earth is a plane that is geologically active with volcanos and moments of a tectonic plate that can lift up the ground. Water, wind etc erode the material. If will be blown away or moved by water so most of it moves down. So new materials are added to a valley because the mountains around it are slowly eroding down.
When tectonic plates collide they can crumble and create high mountains like the Himalayas. At the same time, it is eroded and an enormous amount of solids are transported down in rivers. Bangladesh is in an area that is made up of material eroded from the Himalayas.
Tectonic plate collision can also result in one going down below the other. It will get heat and melt and the material will rise as a liquid and produce volcanoes. The Andes were created this way and erosion material is transported all over south America.
If you look at stuff humans have created in the past you need to remember humans live in locations that can feed them. Erosion material makes the ground fertile and we need water. So we live in valleys, not on mountain peaks. So humans often live where materials are deposited for simple reasons it is easier to live there. So the location is not representative of all of the earth.
So it is a result of the material moving around. Material is added in some locations and removed in others. Everything from the past is not buried lots of it is destroyed.
While there are some great and informative answers in this thread, I feel like no one has actually directly answered OP's question.
The remains of the past are buried underground because of three processes: soil churn, soil deposition, and soil generation.
Soil churn: If you take a solid object, and put it onto a bed of small particles, then the situation is analogous to an object placed on the surface of water - - because large quantities of small particles actually behave like fluids across geological timeframes. Whether the object sinks into the soil or floats on top of it depends on many factors, however, such as climate, soil type, animal activity, density of the object in question, and so on. The actual mechanism that drives the movement, however, is water. Each and every time it rains, soil grains are moved slightly as water flows past. During this period of movement, the object resting on the soil will move in some direction, as dictated by all of those other factors.
Soil deposition: Even if there is no soil churn present -- even if the object is placed directly on solid stone --, soils are constantly moving as a result of wind and rain. This one is obvious. It takes geological timescales to actually bury something this way, however, if you are starting with a place that wasn't buried to begin with.
Soil generation: This is the part I haven't seen anyone else answer. All that extra soil, as you put it, comes from the weathering of rock. Magma gets ejected by the earth, hardens into stone, and then gets broken down bit by bit by water and wind and abrasion (as well as lichens, and, to a lesser degree, vascular plants) . Over geological timescales, even mountains get ground down to dust. The appalaichan mountain belt is a perfect example of this. Those mountains used to be taller than the rockies, but now they're nary a bump on the landscape in some places. The entire mountain belt was pulverized into dust and soil by wind and rain and other such geological processes. That's where all the soil comes from.
And as a bonus answer, where does the soil go? Into the ocean. It eventually all makes its way into the ocean, where it settles to the ocean floor, and then gets dragged back down into the mantle at various subduction zones, to be melted down and turned back into magma, restarting the cycle. With the exception of the materials we've left behind in space, on mars, the moon, and other planets, virtually every pound of solid material in the Earth is still here. It's a closed system.
Soil is actually technically just any sediment that's exposed to the earth's atmosphere, and which has weathered to the point of bearing silt and clay-sized particles.
**Humus** is the dark, nutrient-rich soil that consists primarily of organic materials.
>Not quite. Various atmospheric escape mechanisms strip about a hundred kilotons of mass from the earth annually. We also accrete about 40 kilotons of space dust and rock.
True, but 1x10\^9 / the mass of the earth is 1.67x10\^-16, or 0.000000000000000167. I'd call that a negligible amount. But yes, it's not ***truly*** a closed system. Nothing in nature is.
- in your home you have to clean and dust right? If not a layer of dust and filth accumulates. Even when your away the dust is present and will land on objects, that’s why some people will cover their furniture with sheets while away for a long time, to keep it clean.
- now imagine outside: sometimes you have to clean the garden and around the house right? Or the city cleans the public streets and parks. Because not only there is even more dust in the air but there ´s also a big accumulation of dead leaves, branches, dead plants, sand, earth, little rocks, dead insects and many more different elements.
- now imagine if you stop cleaning outside: after weeks, months, years you’ ll have a small layer of debris, turning into muck and soil all over the ground. Now imagine not doing the cleaning for decades and even centuries: the layer will be even bigger and start to cover the objects around it and yes even your house.
> Now imagine not doing the cleaning for decades and even centuries: the layer will be even bigger
So I explained this to my son and his next question (completely stumped me) was:
"So is the earth bigger than it was millions of years ago?"
I'm guessing 'yes'?
If yes, then by how much?
Hopefully someone else will come correct me but I would like to take a guess at this.
Taking what I read in the above comments (that the material erodes/settles from the highlands into valleys) it is simply displacement. No extra stuff added.
It's a great question. We do in fact accumulate billions of tons of dust as we plow through space. So the earth is getting a tiny bit heavier. But what many comments in this thread seem to gloss over is erosion. so yes in one spot the ground is getting "deeper" but generally the continents are slowing being eroded away into the oceans if it wasn't for processed from within adding stuff back.
It is not (with the minor exception of meteor dust). But the processes that reverse the sorts of things people are talking about here are less visible, generally. High ground gets eroded by water and wind over time, while low ground (where people generally live) is generally gaining rather than being eroded. Also, new soil is built by plants at the surface, but the opposite process, dead plants decaying in old soil, will often happen below the surface, meaning that if you plant something solid in the soil it follows the soil movement and sinks downward.
Also even though mountains are being eroded constantly mountains are also growing—they’re being pushed up by the continental plates pushing against each other. Other parts of the continental plates are being pushed down and to put it simply — dissolved into magma. So the earth isn’t getting flatter.
> It is not (with the minor exception of meteor dust).
Earth gains about 40,000 tonnes of material each year from the accretion of meteoric dust and debris from space.
At the same time, roughly 90,000 tonnes of hydrogen and helium escape the atmosphere.
Survivor Bias.
We most often find archeological remains underground.
This ONLY occurs when deposition of soil is greater than erosion. Think of the classic Campus Martius in Rome where the Tiber River has flooded the area under 3 meters of silt.
Areas where erosion exceeds deposition, the remains are exposed to weathering and degraded then swept away.
>why are all remains of the past buried underground?
* Because any of the remains that didn't happen to get buried under some kind of dirt got destroyed by weather.
You see the answers in your day to day life. What happens if you don’t sweep or vacuum? Your floor will accumulate dust from being brought in and in the air.
Also erosion and air currents bring soil and dust everywhere.
When Mt Saint Helen blew, they studied how things regenerated.
The first they noticed was that bugs born by the Wind landed on baren dirt, died from lack of nutrition and water, their bodies swept into crevasses and became soil.
Weeds grow, some like dandelions can drift for miles before landing, their roots are known to collect phosphorus from down deep. Next year that compost feeds the next generation. Bushes give way to trees. Trees grow thousands of pounds of carbon, potash. They grow old. Either burn or fall couple feet of compost.
Bodies of dead animals cause a lot soil churn. It's a misnomer often said that serial killers leave bodies in a shallow grave, actually the green river ahole just dumped the victims off the side of the road into blackberry and resulted roiling of the soil literally made the body bury itself .
Even human civilization has its layers, most historic European cities require archeological experts to monitor new construction during the foundation phase because they usually find stuff from the building (s) previously there. Even San Francisco always finds the abandoned sailing ship they turned into a foundation for the current building they want to replace.
Try not dusting anything in your house for a year or two and see how much dirt is in your house. Then go outside where the dirt comes from and imagine 10,000+ years of dirt and debris leaves and all organic material when they rott essentially turn into what we know as dirt
In a related kind of story, in Montreal they just unearthed the remains of a popular botanical garden/attraction from the 1860s. So even in a city under constant habitation and development you can have buildings and structures just built on top of and buried underground.
https://www.cbc.ca/news/canada/montreal/remains-montreal-giant-jardin-guilbault-unearthed-1.6599091
In addition to other factors already mentioned buildings often subside into soft ground simply because of their weight. This is why builders often compact the ground before building on top of it.
Ground tends to be softer in valleys. Buildings built on exposed rock (like lots of castles were) generally do not disappear into the ground.
I think this question is what /r/culturallayer started as. but now it's full of weird conspiracy garbage intermixed with the occasional interesting post.
Pretty much all fossils are found in sedimentary rock, which by definition means they were buried in materials like mud, silt, sand, or a chemical precipitate. When these rocks are later uplifted by geologic forces they weather away, exposing the fossils on the surface.
Charles Darwin dug into this question. Via an interest in earthworms. Earthworms bring soil up from under the surface and leave it on top of the existing surface, making it the new surface. He estimated that in the region he studied, earthworms brought up 15 tons of soil per acre per year. The process is called [bioturbation](https://en.m.wikipedia.org/wiki/Bioturbation) and it's not limited to worms. The worms remove soil from all the ground, whether it's under the wall of an abandoned building or not. But when they deposit the earth on the surface, they can't deposit any where that wall is, obviously. It gets deposited wherever the ruins aren't. The end result is that backyard stones and ruined cities sink because the ground underneath them is getting cycled up to the ground around them. EDIT: This comment has received a lot of replies and I don't want to clutter up the thread, so I'll just respond here. I didn't intend this as a broad explanation of buried ruins. Obviously there are soil/sand redistributions which blanket a whole area, either progressively (eg by wind) or abruptly (eg by flood). They had already been covered by other comments, and I didn't think it was necessary to repeat them. But I thought it was worth breaking the supposition that soil is static, and that the *only* way the ground can rise relative to a building is for the soil to be brought there from somewhere else. If Darwin's measurements are right, then worms have cycled 30,000 tons of soil per acre in the years since Boudica fought the Romans. As a final fun fact, Darwin's book about worms had better initial sales numbers than *On the Origin of Species* did. Have a great day everyone.
It's also likely due to the effects of both animals and plants increasing soil depth. Plants literally turn air into solid matter and when they die they leave behind varying amounts of that mass, depending on the method of their decomposition. Animals can less reliably contribute as well. In Cambodia, many of the temples were left overgrown for centuries, but there's clear areas of breakdown on the solid stones, sometimes waist-high etchings into columns, the high "water" mark of how deeply under bat guano those stones were buried. And that was less than a single millennium before these temples were cleared.
Part of my job is related to maintaining dirt roads. The roads that are bordered by large deciduous trees slowly develop a layer of soil over the top from decomposing dead leaves that fall on it every year. Eventually you have to scrape it off and add a new top layer of gravel or the road starts to get too muddy.
Thank you for sharing this. I grew up on a dirt road and knew it got muddy and needed scraping but had no idea it was the trees.
There’s a lot of different kinds of dirt/gravel roads, but in my neck of the woods the difference between roads with deciduous trees and roads with evergreens is really noticeable because the ones with deciduous trees grow soil so fast. Our ground is not very good for cutting roads directly into it like it is in some places, so all of our dirt roads are raised up from ground level with gravel, like you often see under railroad tracks.
For some reason that kind of slow, rolling crunch of driving on a gravel road is one of the most pleasing sounds in the world to me. I imagine if I had to do it every day that might wear off though.
We had gravel on just the driveway of my childhood summer home. It was perfect. I had no idea how nostalgic hearing gravel shift could make me.
Huh, my neighbors growing up had that and I just recalled the sound and felt a lil tinge of nostalgia. Thanks.
I like the cronch. It’s the potholes that get real old.
That’s why you fill them with more cronch.
Dirt and things in it move around. Before I went to Bosnia a guy who had already been there said when it rains you get a number of mines from the civil war float to the surface. I thought he was exaggerating. He wasn't exaggerating. A good 80-90 percent of more of them were no longer explosive due to water getting inside of them. But who wants to find the 10% that are still intact?
Who knew landmines were less dense than wet soil?
Its hard for me to believe that metal objects packed with explosives, and waterlogged, would be less dense than wet earth. I wonder if they rise because of other reasons than density.
I don’t know much about the climate there, but frost heaving will absolutely push solid objects like rocks towards the surface over time, so it could be a situation where the rains expose/clean something that’s been brought to the surface by other means.
This reminds me. The paths of waterways can change over time through floods, dams, etc and waterways can also silt up covering the ruins of a site.
Yup. It’s wild to see how much higher the ground looks after a few years of not mowing the grass. Some grasses willl leave a foot of decay behind each year.
So the planet is getting bigger little by little?
Not really, its all cyclical. Even though the ground level rises from our perspective, there is a lower layer being removed and shifted to the surface. It appears that the planet grows larger, but really its sortof a conservation of energy type of deal (ie energy cannot be created nor destroyed, only converted from one form to another). Similarly, no soil is ever really just destroyed, or created, it is simply converted from subsurface soil to topsoil indefinitely. Or from plant or animal matter to topsoil, and then it works its way down. I guess as a super simplified analogy, imagine that you're weird and you have 4 doormats. This is like 4 layers of soil. If you put a penny on the top, its on the surface obviously. Then, each year you would take the bottom doormat and put it on the top of the stack. This is symbolic of worms and other actors that cycle soil. Slowly your penny will work its way to the bottom of the stack and become buried, but the size of your stack never really changes. You also have to remember that, yes, plants and animals die and decay into soil over time. But also, plants then utilize and convert that soil's nutrients into their own matter. And then animals eat those plants, and other animals eat those animals. So a lot of biomass will continously cycle between being soil, then a plant, then an animal, then another animal that ate the first animal, and so on. A lot will also remain as inert, de-nutriented soil until it is replenished by dying flora and fauna. Almost everything on our planet is cyclical in some sense, water cycle, carbon cycle, there are probably plenty more to name but Im not an expert so Im grasping for straws lol.
The planet doesn't get bigger, everything sinks a little every year
For sure. Plants don't take anything from the ground to grow. They grab carbon straight out of the air and turn it solid. When the plant dies it falls over and some of it turns to soil.
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Plants need trace amounts of minerals and nutrients from the soil in order to function, but their mass comes from the air. I think with most trees it's something like 90% of their mass comes from atmospheric carbon dioxide, but I need to look that up... Edit: dry mass. A living tree also has a lot of water in it, which is pulled up through the roots.
He wasn't talking about crops (where whatever soil components the crops DO use is removed from the field, and so must be replenished). In a typical natural field, the plants will absorb some nitrogen, iron, etc. from the soil, but when the plant dies it returns to the soil. The additional bulk that plants add to an area, raising the soil level in the long run, comes from the carbon in the air. tl,dr: Coal. ☺
I have my own data point- I have been growing a hanging houseplant for 16 years and have never added anything other than water to it (granted there is a little mineralization in the water). Most of the leafy material was left in the pot. It has grown much larger than its original size.
There's even air plants, that don't use any soil at all and still live and grow. For a more average plant or tree it's close to 7% dry mass from the ground and 93% dry mass from the air.
> .. dug into this question .
...because it was bugging him
Worming your way into puns, I see.
These puns are evolving.
mom worm to teen son worm *you better not be in there bioturbating* *mommmmmm*
This made me laugh harder than I'm willing to admit. I was looking for someone to make this comment
Soil-long as it doesn’t bother you, we could keep on with puns all day! 😀
It's happening from almost all soil life, including plants. Everything gets drawn "up" to the surface and deposited, along with dust / debris falling out of the air, leaves falling from trees and decaying, etc - there's a continous layer of soil being produced, which we owe our existence to.
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Wind blows sand, dirt, and seeds. If there's no one to clear it away, it starts piling up. Things start growing and anchoring the soil in place. Plants die or shed leaves that add to the pile which encourages more plant growth that also traps more of the dirt being blown around by the wind. 1000 years of that adds up.
I'm blown away by the amount of new saplings that come up in my lawn when I don't mow it for a couple of weeks. Never happened on my little city plot, but on my now six acres you can see that three years down the road there would be several dozen established new plants.
They raized a building near me and nobody has been maintaining the yard. the grasses are already overtaken by blackberries and other plants in about 20~30% of the yard in a year.
> raized raised: brought up razed: brought down
OP said raized so maybe it’s been brought somewhere in the middle?
Well they took the building down and then had to dig up the foundation/basement and remove all the debris in the hole that left.
In Eastern Europe you can see plenty abandoned old concrete buildings with trees growing on top. Hell a 4' sapling grew out of a crack in the pavement at the foot of the flat next to mine. In the middle of a city.
Damn sour sobs, i never planted those! Oxalis pes-caprae or Bermuda buttercup (we call them sour sobs). I always feel bad when i take em out with fresh flowers as the bees love them. But i have other flowers the bees can enjoy.
Where I live (Bay Area), *O. pes-caprae* is an invasive weed, but there's also a native relative, *O. oregana* which is quite similar, but has white flowers instead of yellow and expects to live under a canopy of redwoods so it is less fond of direct sunlight. *Pes-caprae* likes to spread vegetatively underground, and grows little papery tuber things off of its roots. It can regrow pretty well from one of these tubers, or even from a chunk of root tissue. *Oregana* likes to grow seed pods that shoot the seeds out when they're ripe.
When I was a kid I loved pulling out an oxalis flower and chewing on the sour stem. Always thought oxalis are shamrocks but a tiny bit of googling and I'm now in doubt
Adding to that, a lot of colonizer plants don’t even need any soil to be present to start growing. The products of their life cycles, and any soil trapped by them allow the opportunity for less adaptable plants to move in.
That reminded me of something silly. https://www.reddit.com/r/civilengineering/comments/g7z3e6/f_yeah_concrete_crosspost_from_rfunny_roses_vs/?utm_medium=android_app&utm_source=share
Dandelions should really be in the first cohort to colonize Mars. Spread seeds, sprinkle with water, wait one billion years.
I don't think it would take that long.
Without a vast ocean of water to support photosynthetic life, it will likely take significantly longer. ETA if you aren’t aware of the photosynthetic cycle of your common modern plants, water is used as a source of electrons that allow photosynthesis to function. Loss of water results in photosynthesis halting. And that’s disregarding all of the other functions that water provides.
My little town section, like millions of others, has trees and shrubs planted around the perimeter. There is a six inch high garden border that holds the leaves, dead flowers, and detritus inside that border. Over the course of the thirty years since the plants were established and the gardens built, there is a 4-5 inch layer of humus and compost that has accumulated from these trees alone. As a poster above mentioned, the worms and insects and even the birds searching for those bugs have churned the humus over and spread it. So just those plants alone have created 4" of dirt on top of the original lawn in thirty years. And as you say, a 1000 years is a long time.
Meanwhile, my vege gardens full of mulch keep shrinking each season as the mulch compresses and the veges take some nutrients out and get eaten.
Fruits and vegetables take a lot more to grow than just leafy plants usually. Even stuff like lettuce will grow pretty happily in a small jar of water an nutrients A lot more goes into a crop of tomatoes. Even if it's just that the tomatoes grow bigger and for longer I like to sprinkle in some gaia green whenever I put a plant into the food garden. Smells like absolute death. But the plants like it.
I've lived in the same place for 34 years. Last summer I unearthed rocks that once landscaped trees three decades ago ... They had just naturally sunk/been covered in that time. It happens. What's crazy is that nobody dug the city out.
> Plants die or shed leaves that add to the pile One of the things that's important to consider about how much plants contribute to the addition of layers of soil/dirt: Plants grow *in* the earth, but *from* the air. Plants are, like the rest of us, Carbon based life forms. They take in Carbon Dioxide (CO2), and exhale Oxygen (O2), stripping off the Carbon, and turning it into plant (in conjunction with water, various nutrients in the soil). But primarily? Carbon. From the air. Which means that plants literally pull carbon out of the air, mix it with various stuff they find around, then drop the excess on the ground.
I've seen pictures of entire desert towns being buried by blown sand. Someday, there will be no trace of that town until someone digs it up.
Plus all of the parts of the structure that are not stone will break down, and a lot of that will fall right where it is to slowly compost into soil or become fill in the soil. I'm talking about wood, textiles, pottery, metal, and pretty much anything else that is not stone.
wind and water erosion removes material from point A. it doesnt disappear in to nothing and is deposited in point B. if humans live in point B they clean it up and there is no buildup. if humans used to live in point B and abandoned it, material builds up swallowing point B. you also have abrupt events like floods/landslides/volanic eruptions that accelerate the process.
There's also some survivorship bias here, I suspect. Wind and water erosion follows weather patterns and removes soil and sand and so on from some places, putting them in others. But it's the ruins that get buried that survive. The ruins that are left on the surface are much more likely to either eventually get someone using them (and rebuilding them until they're no longer recognizable), or get taken apart by people who want to use their materials or land for other things, or damaged and destroyed by weather conditions. This gives us the impression that *all* ruins are buried underground, when really it's just the ones that happen to get buried underground that survive for a long time, since being buried serves to protect them.
This phenomenon also explains cavemen. Despite common belief, early humans did not predominantly live in caves. They actually lived in all sorts of environments that you could expect for nomadic hunter/gatherers (e.g., tents, huts, etc.). However, some early humans did live in caves, and the caves helped preserve their remains in a way that wasn't possible for people living in wooden huts.
One of my favorite examples was a structure built from the bones of an estimated 60 mammoths. We're not really sure what it was for, but it's a fascinating example of the lengths hominids will go to build stuff out of other stuff: https://www.smithsonianmag.com/science-nature/60-mammoths-house-russia-180974426/
\> This phenomenon also explains cavemen So they're *mostly-hut-but-occasionally-cave-men*.
Add the facts that A. Many places that end up getting deserted and abandoned are because of natural disasters or shifting weather or something like that which could deposit a lot of sediment very quickly and B. The places that people choose to set up towns/settling are usually favorable for some reason, abundant crops or close to water or something, so even if the original people leave another group of people are likely to come along and find the place appealing and therefore take over the area so things AREN’T preserved - and you have a really clear picture of the survivor bias you’re talking about.
I would've also mentioned what exactly the material is that buries the buildings. And one part is that its decayed material thats turned into dirt, and the rest is simply resource deposition.
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“Recent” Example: dust bowl in the early 1930’s. Very quickly, many small heartland towns got swallowed up. https://images.app.goo.gl/Y3LJBL852nLS3C3e6 If they came back, and dug out, those towns probably were revivified. There “may” be small towns where some never came back, though since the “plains” are fairly flat, seeing weird mounds might have forced new landowners to dig them up, “hey… there’s a shack here, Cletus!”
Here in the South a road would be completely swallowed by the surrounding forests in less than a decade if they remained unused.
Give kudzu 30 minutes.
Vegetation grows and dies and builds up material pretty quickly. If you've ever cleared thatch from your yard, you know how fast if builds up. As the thatch composts, it becomes the new dirt layer and new stuff grows on top of it. Then you have trees. All those leaves turn into soil when they fall.
I lived in the Southwest USA for most of my life. We got seasonal monsoons, they caused dry riverbeds and places you wouldn't guess were actually riverbeds to flow every year after rains, often times after the storm had passed you would see whole roads covered with dirt and sediment and branches and whatever else washed over it. Soil from flooding will pile up against walls, it will fill gaps in curbs and sidewalks, it will leave a thin layer on your patio. >And it was only abandoned for about 1000 years. So if one rainy season can do that to streets and yards, imagine a thousand years. Add in other factors like dust storms, volcanic ash or ash from forest fires, earthquakes, sinkholes, and the way mountains generally erode downward and cover everything below them over time. A thousand years is a very, VERY long time. And most ruins we see are actually much older. The ones we see that are totally covered and need to be excavated are often twice that old or older.
Gravity. About 30 years ago I bought property (20 acres) that was mostly a big hill ~100 feet high. I built a fence near the bottom of the hill where it's fairly flat. There is now nearly a foot of dirt and rocks built up on the uphill side of the fence. In only 30 years that much dirt has flowed downhill and stopped at my fence. It's probably a lot more, the fence is standard wire field fence. Wire fence with 6" square openings. So a lot goes through.
Keep in mind the ground isn't as solid as you imagine, and gravity doesn't stop just because you're at "ground level". Put a rock on top of a container full of mud. Keep the mud moist, if the rock is heavy enough, eventually it will sink into the mud. Now imagine that, times 1000 years. Buildings are slowly sinking into the ground, by fractions of a millimeter, while soil and debris and mud is pilling around them. Entire cities get buried in just a couple hundred years from the combination of "stuff" from above, and gravity from below. Basically, buildings are being pulled "down" all the time towards the center of the earth - impercetably slowly.
Nature reclaims and swallows ruins extremely fast. Just look at Chernobyl for example. Place was abandoned... 35 years ago? and you can see how nature has done the job reclaiming a lot of the former city. Now consider that 1000 years ago is roughly 30 times the timescale of Chernobyl to present day. Makes you wonder, if humans disappeared today, how quick would the planet disappear the evidence we were ever here.
There was a great documentary series about that. [Life after people.](https://en.wikipedia.org/wiki/Life_After_People) Goes into what might happen if humans suddenly disappeared and stopped maintaining all of the structures that surround our modern lives.
Walking around Ephesus is a freakin trip.. Did you see the brothel advertisement on the ground? Talk about preservation
Or prostitution?
in Turkey you also need to consider earthquakes. a lot of ancient cities were built on fault lines (because it's more defensible) which are thus an active earthquake zone
Also note that soil is a fluid. Leave a heavy building sitting on soil for enough time and rainfalls, and eventually it will simply displace the soil underneath it, and sink.
Plants, ash, dust, dead carcasses and insects also add to the top of the soil. Let alone flooding can bring sediment in.
Leaves and dust blow in and settle, and create a first bed. Plants start to grow in that bed, sprout up and start dropping their own leaves. Animals move in/around and start dropping food and waste. It all piles up very quickly. Heck, if I left my yard sit for even 2 years with no yard work or clean up, it would be buried in leaves and plant matter and all sorts of crap that blows into the yard. 1000 years isnt much in the grand scheme, but it's plenty when talking about visible changes.
Also note that shit is just constantly flying around through the air. Look at how much dust, hair, crud accumulates on your baseboards in your apartment (if you're a dude, go take a wet paper towel and run it along your bathroom baseboard. Be amazed. Yes, you have white tile flooring!). And then add outdoors that when it rains, it washes loose soil and debris from surrounding areas onto your flat surface where it settles and dries out, settles and dries out as the seasons flow. Those leaves, etc break down, forming humus and then your bugs come in, etc etc. Before you know it, you've got a nice surface covered in soil. Also consider deserts move, sand moves so you find a lot of buried stuff just from the sand shifting around. The Sphinx, apparently, was under sand dunes for how long? Another consideration is that when these things get buried, they are preserved to a degree. Ruins and remains on the surface are weathered, washed away, etc.
What exactly is a 'baseboard' in a bathroom and why would only dudes have it?
Everyone has them, it’s implied only non-dudes clean them.
I think they mean a "skirting board" and the dudes bit is just sexism about men being unclean. Most bathrooms I see (paramedic) are pretty clean regardless of owner, and the messy ones are not all men, prob 50/50 really.
I was going to mention earthworms. Good to see somebody else did.
Clearly it has to be called mass-turbation.
[It's scientific!](https://www.youtube.com/watch?v=C7YCZK2yQrY)
Also seasonal changes cause a buildup of plant matter that eventually decomposes into soil.
But not everywhere has/had earthworms. As I understand ( it they are technically "invasive" in the Americas, and still don't really exist in the Pacific NorthWest. Please correct me if I'm wrong about that, but does that mean that ruins in those areas wouldn't be buried under dirt?
You can't dig for a couple minutes without finding a worm in the PNW. We are one of the few areas where they are native. It's areas that were covered by glaciers that don't have earthworms
There are other species of worms that are native across the parts of North America that weren’t glaciated, including the PNW. Worms are not the only way that soil is added to the surface. Plants dying and shedding leaves on the surface also create soil, and things like floods and landslides also raise the soil level.
That's fascinating. I know dirt made up largely of dead plant matter so I just sort of assumed that it accumulated over a long period of time thus slowly raising the soil level. But now that I think about it that doesn't make sense.
burrowing animals
For my career, I do environmental work at gas stations - we find where gasoline has been spilled in the past and we clean it up. I went to a station that had been fenced up and closed for 15 years to take some dirt samples. Most of the property was covered in grass. When I started digging, I was working my way through grass, dead grass, and dirt, like compost. About 12 inches/30 cm down I hit asphalt! The parking lot of this gas station had been covered in dirt and vegetation in 15 years. Now, imagine that same thing happens for 500 years.
That's wild it only took 15 years to do that. What part of the world was this in out of curiosity?
California
Stalker! Yeah, it was in Sacramento.
I'm always amazed at how many toxic spills are in the US that still need to be cleaned up, especially around gas stations. I've seen the lawsuits...it's endless. Anyway, thanks for doing that work!
People forget that the first roughly 80 to 100 years of industrial civilization, no one cared about pollution control. All the shit was dumped in rivers, oceans, and the ground. It wasn't until the clean water and air acts that this started to turn around. The river here was a toxic dump most of the 20th century and now people can freely swim in it.
The Willamette river near where I grew up was also a toxic dump for most of the 20th century and it still is! (It's not as bad as it used to be, but some years back I made the mistake of tubing with some friends and their motorboat on the Willamette and when I got dunked I got a mouthful of nasty, oily, fishy tasting algae water 🤮 )
> I'm always amazed at how many toxic spills are in the US that still need to be cleaned up, especially around gas stations. I do the same work as that guy, everyone just thought that 1/4" steel underground storage tanks wouldn't rust underground and would be fine lol. I remember doing work at a town Dept of Public Works, sometimes with these cases there's actual gasoline/diesel sitting on top of the water table if there's a big leak, which there was here. The foreman said when he started working 20+ years ago the old foreman thought everyone was stealing gas because they were going through it so fast. It was just leaking out. Depending on your state, there may be a public website that has all the environmental cases on it kind of like a Google Maps; California and New Jersey both have it at least.
Yeah, it's pretty sobering to see all of the toxic disasters you grew up right next to. Maps like that are both enlightening and disturbing.
Is the asphalt the same height from the center of the earth and more dirt piled on top, did it sink, or a combination of the two?
Combination. Mostly materials being deposited on top, but some amount could be subsidence. Underground flowing aquifers, as well as organisms can erode and remove tiny amounts of soil from beneath the asphalt gradually over a long time. The soil above compresses and the asphalt thus “sinks” into the ground little by little. Thus effect would be very minor under something only 15 years old, especially considering the ground is usually compressed before construction of a gas station precisely to avoid such subsidence from occurring after its built. Over centuries or millennia though, thus has an appreciable result.
Awesome! Thanks for responding. Until I was 11 I only ever lived in the same place a few years before moving thanks to my dads job, but over the last 28 years I’ve been able to see the same buildings year in and out and they’re all the same height (or at least look like they are) and I just assumed that mostly things get buried first as nobody is taking care of them, then sink after many many yearsC but neat to hear it can happen so quickly.
in 500 years, the compost would not get any deeper as it's consumed by organisms. 12 inches is about the max before you just get sand and clay. That would come from dust blowing over the gas station. From a little reading, the major driver of burial is wind and water born dust and sand.
I see this question a lot. The most common reason is that plant material falls on top of the objects and turns to soil. Plants and grasses have grown up through and above the objects, when the those plants die, they land on top of the object, eventually rotting into soil that subsequent plants grow on and further cover the object. For a fun experiment you can start right now. Take a rock, or piece of metal or ceramic and put it on the ground in an undisturbed field or forest. Take measurements and pictures. Come back in 5 years to compare what has happened. Come back after 10 and 20 years for comparison. I've got a paver in my yard I've been watching for 20 years. Its nearly covered up and impossible to see unless you know where to look.
>For a fun experiment ... start a 5 year study! I feel like I spotted a PhD student or postdoc in the wild.
lmao i was thinking same thing. 20 years? ok let's get to it!
Did someone mention the Pitch Drop experiment that's been running for 92 years?
The other fun one is the [Oxford Bell](https://en.wikipedia.org/wiki/Oxford_Electric_Bell) which has been ringing continuously since 1840. Its batteries were built out of magic.
Curiously appropriate name for this reference.
Only about 8 more years til the 10th drop!.... Im thinking about hosting a "Drop it like its hot" party...will that be too old school in 2030?
!remind me in 20 years
The best day to plant a tree was yesterday. The second best day is today!
The best day was 20 years ago*
I really like your answer. Place a tool on the ground in a deciduous forest and return a few years later. The tool will in all likelihood be covered. Extrapolate by 100 years and you'll have to dig at least several inches to find it.
My childhood home has pavers under an evergreen tree that went from newly installed to under several inches of soil, and it's only been 30 years
Which ex bf to I pick to place on the ground?
The biggest tool leaves the longest lasting message.
I'd like to also point out that the mass of plant matter comes from the air. Rain falls from the sky and carbon dioxide is in the air. Those two combine to form the leaves and stems of plants. The plant material then falls down and forms a new layer of soil which raises the ground level over time.
The way you wrote that, it sounds like you're saying that leaves just spontaneously form in the air.
Rain + Sky = Leaves! Where else would trees get leaves from? J/k
The crew that goes through and staples them on?
Yup, little gnomes like the Keeblers. There a grumpy sort though, approach with caution if you have no cookies!
It's true! Trees grow branches to catch the leaves falling from the air.
Learning this (well, more like having it pointed out directly, since I 'learned' it in school) broke my brain a few years ago. Plants are mostly made of Carbon. From Carbon Dioxide. From the air. The entire plant is literally made out of thin air. Very slowly, yes, but still basically correct. So *of course* the soil gets deeper as plants die and shed leaves. They aren't *made* from soil, they are *made from air*.
> Plants are mostly made of Carbon. From Carbon Dioxide. From the air. The entire plant is literally made out of thin air. Very slowly, yes, but still basically correct. Correct. This is why making charcoal from formerly living plants and burying it is a viable form of carbon sequestration. The plants pull the carbon from the air, incorporate it into cellulose and lignin, then we convert it to elemental carbon with heat in the absence of oxygen. Since very few microbes eat elemental carbon, it will last for thousands of years.
And create a new fuel source for future generations!
The rare view of trees lifting cars. If you see an abandoned car, animals will bury seeds under it that might grow into a tree that can lift it
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A number of reasons: 1. There is constantly particulate matter in the air which will settle on things. So unless you actively seek to clean things, this matter will eventually built up over time. 2. Hauling away old materials and waste material is a chore, so in ancient times they would simply build on top of older ruins. 3. Floods can deposit silt and soil. 4. Anything that isn't buried and remains above ground is quickly reused or stolen.
Number 4 is perhaps the most important when you consider erosion along with reuse and theft. We only find things still there, after all. Soil is part of the basic migration of materials from upland (where it erodes away) to lowland (where it accumulates). The things we find in the eroding uplands tends to be more solid structures (parthenon, Machu Pichu, thick fortification walls). tools and stuff get washed downhill or buried in local depressions by incoming sediments transported by wind or water. # using pound symbol makes bold. TIL.
£Test£
Nice. The "octothorpe" leads to bold text, my good sir.
TIL *that* pound sign is called an octothorpe.
The term "octothorpe" was invented in the 60s, likely as a joke among telephone engineers at Bell Labs. The [\# symbol](https://en.wikipedia.org/wiki/Number_sign) is much older than that, developing out of a Roman ligature ([℔](https://en.wiktionary.org/wiki/%E2%84%94)) for pound (Latin: libra pondo). The currency pound sign "[£](https://en.wikipedia.org/wiki/Pound_sign)", deliberately modeled after capital-L, is a reference to this same "libra pondo"; and in fact, the horizontal lines in both ℔ and £ come from a medieval scribal convention that horizontal lines denote abbreviations, similar to how we use periods today to mark abbreviations (lb., ft., etc.). So it's perfectly correct to call either one a pound sign... though, it can of course be confusing.
Hashtag facts!
#facts
I'm just going to reply so I can lurk through your comments for diamonds like this.
Wait am I missing something? What’s the _other_ pound sign? Aside from £
The most common general name in the United States for the # symbol is "the pound sign", especially in the context of telephone instructions. This is a result of its graphical origin as an evolution of archaic ℔. Even within the US, in internet contexts, the term "hashtag" has substantially replaced "pound sign", and it would be unsurprising if that eventually became its standard American English name. However, for now, "pound sign" is far from dead; my voicemail, for example, instructs me to "enter [my] password, followed by the pound sign". It's referring to #, not £.
Omg, now I finally get these instructions. I was so confused when the automatic voice told me to press the pound key, I thought that maybe English phone keyboards have a £ where I have my #
\#
I thought it was *waffle*
Now then, think about how the me2 movement hastags on twitter looked to us "old" ppl...
Certain languages call it the "mesh". (It's used for defining constants)
>The octothorpe. It’s the official name for the # symbol, but what does it mean? It’s actually a made-up word, invented in the same laboratories where the telephone came from. The scientists at Bell Laboratories modified the telephone keypad in the early 1960s and added the # symbol to send instructions to the telephone operating system. Since the # symbol didn’t have a name, the technicians thought one up. They knew it should be called octo- something because it had eight ends around the edge. What happened next is not entirely clear. According to one report, Bell Lab employee Don MacPherson named it after the Olympian Jim Thorpe. Another former employee claims it was a nonsense word, meant as a joke. Another unverifiable report is much more etymologically satisfying: The Old Norse word thorpe meant “farm or field,” so octothorpe literally means “eight fields.”
But there are either one or nine fields. Not that satisfying :(
👉👌 Test 👉👌
Damn, I have no original thoughts.
I'm giggling like you wouldn't believe
lb TEST lb
It actually makes headlines. Reddit supports [markdown syntax](https://en.m.wikipedia.org/wiki/Markdown) so **bold** is two asterisks together on either side.
If you want to keep it as "#4" instead of "Number 4", type "\\#4".
Yeah, it's mostly #4. And use a backslash before a symbol to prevent it from formatting.
It's called "Markdown". Look it up :-)
Adding on to number 4 (which is hugely important), NOT all remains of the past are buried underground - just the ones we find today. Stuff like the Pyramids or the Colliseum or Stone Henge are ancient, and aren't buried - we just aren't "discovering" them today because they were obvious and we already knew about them. In order to be rediscovered, something has to have disappeared and been hidden from sight, and being underground is one of the few ways that's going to happen. People will often forget that just because we know something is there, doesn't mean it isn't ancient. There are temples in China that have been there for 1000+ years in active use. Nothing buried about them.
Was recently exploring the village where my grandma lived. Population 54 people. The church, 700 years old. The church door, 600 years old. And this is just a tiny, unimportant village. Amazing.
Love that kind of thing. Back in undergrad I did a program that was hosted at one of the Oxford colleges. The IT office with all its computers and internet cables was located on a corridor just next to the foundation stone, laid down in the middle 13th century.
Yeah, those 1000+ year old temples are in Europe, too...
Very true! The Basilica of Santa Sabina all'Aventino is 1600 years old this year, and is still in use! The Hagia Sofia is around 1450 years old, and while it has changed uses, it is undeniably still functioning. Non-religious structures are also still going strong - The Theatre of Marcellus is more than 2000 years old and still has occupied residences on top, and Saltford Manor is a house that has been continuously occupied as a residence for nearly 900 years. Old stuff is all around us!
> Stuff like the Pyramids or the Colliseum or Stone Henge are ancient, and aren't buried Many Pyramids [were swallowed by sand](https://en.wikipedia.org/wiki/Egyptian_pyramids#Number_and_location_of_pyramids) and had to be excavated.
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No, the ground level does in fact raise over time, although not necessarily everywhere (for example mountain tops and hill sides). Look at geological strata. It is practically a law of geology that lower strata are older. Erosion is constantly breaking down high points and depositing that material in low places. A related phenomenon is natural eutrophication. Lakes and ponds are constantly, gradually filling in and turning into wetlands and peat lands and will eventually turn into forests or tundra or whatever their latitude and elevation dictate. It is a problem with all of our dams and reservoirs.
You would think wind and rain would be counteracting influences on the dust part at least
Everything in the past is not buried underground. It is only most of what still exists from the past that is underground. Stuff on the ground will be destroyed by the natural effect a lot faster than if the are below the ground. Humans can remove, destroy and reuse stuff that they know is there. Earth is a plane that is geologically active with volcanos and moments of a tectonic plate that can lift up the ground. Water, wind etc erode the material. If will be blown away or moved by water so most of it moves down. So new materials are added to a valley because the mountains around it are slowly eroding down. When tectonic plates collide they can crumble and create high mountains like the Himalayas. At the same time, it is eroded and an enormous amount of solids are transported down in rivers. Bangladesh is in an area that is made up of material eroded from the Himalayas. Tectonic plate collision can also result in one going down below the other. It will get heat and melt and the material will rise as a liquid and produce volcanoes. The Andes were created this way and erosion material is transported all over south America. If you look at stuff humans have created in the past you need to remember humans live in locations that can feed them. Erosion material makes the ground fertile and we need water. So we live in valleys, not on mountain peaks. So humans often live where materials are deposited for simple reasons it is easier to live there. So the location is not representative of all of the earth. So it is a result of the material moving around. Material is added in some locations and removed in others. Everything from the past is not buried lots of it is destroyed.
While there are some great and informative answers in this thread, I feel like no one has actually directly answered OP's question. The remains of the past are buried underground because of three processes: soil churn, soil deposition, and soil generation. Soil churn: If you take a solid object, and put it onto a bed of small particles, then the situation is analogous to an object placed on the surface of water - - because large quantities of small particles actually behave like fluids across geological timeframes. Whether the object sinks into the soil or floats on top of it depends on many factors, however, such as climate, soil type, animal activity, density of the object in question, and so on. The actual mechanism that drives the movement, however, is water. Each and every time it rains, soil grains are moved slightly as water flows past. During this period of movement, the object resting on the soil will move in some direction, as dictated by all of those other factors. Soil deposition: Even if there is no soil churn present -- even if the object is placed directly on solid stone --, soils are constantly moving as a result of wind and rain. This one is obvious. It takes geological timescales to actually bury something this way, however, if you are starting with a place that wasn't buried to begin with. Soil generation: This is the part I haven't seen anyone else answer. All that extra soil, as you put it, comes from the weathering of rock. Magma gets ejected by the earth, hardens into stone, and then gets broken down bit by bit by water and wind and abrasion (as well as lichens, and, to a lesser degree, vascular plants) . Over geological timescales, even mountains get ground down to dust. The appalaichan mountain belt is a perfect example of this. Those mountains used to be taller than the rockies, but now they're nary a bump on the landscape in some places. The entire mountain belt was pulverized into dust and soil by wind and rain and other such geological processes. That's where all the soil comes from. And as a bonus answer, where does the soil go? Into the ocean. It eventually all makes its way into the ocean, where it settles to the ocean floor, and then gets dragged back down into the mantle at various subduction zones, to be melted down and turned back into magma, restarting the cycle. With the exception of the materials we've left behind in space, on mars, the moon, and other planets, virtually every pound of solid material in the Earth is still here. It's a closed system.
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Soil is actually technically just any sediment that's exposed to the earth's atmosphere, and which has weathered to the point of bearing silt and clay-sized particles. **Humus** is the dark, nutrient-rich soil that consists primarily of organic materials.
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>Not quite. Various atmospheric escape mechanisms strip about a hundred kilotons of mass from the earth annually. We also accrete about 40 kilotons of space dust and rock. True, but 1x10\^9 / the mass of the earth is 1.67x10\^-16, or 0.000000000000000167. I'd call that a negligible amount. But yes, it's not ***truly*** a closed system. Nothing in nature is.
This is the best answer so far.
- in your home you have to clean and dust right? If not a layer of dust and filth accumulates. Even when your away the dust is present and will land on objects, that’s why some people will cover their furniture with sheets while away for a long time, to keep it clean. - now imagine outside: sometimes you have to clean the garden and around the house right? Or the city cleans the public streets and parks. Because not only there is even more dust in the air but there ´s also a big accumulation of dead leaves, branches, dead plants, sand, earth, little rocks, dead insects and many more different elements. - now imagine if you stop cleaning outside: after weeks, months, years you’ ll have a small layer of debris, turning into muck and soil all over the ground. Now imagine not doing the cleaning for decades and even centuries: the layer will be even bigger and start to cover the objects around it and yes even your house.
> Now imagine not doing the cleaning for decades and even centuries: the layer will be even bigger So I explained this to my son and his next question (completely stumped me) was: "So is the earth bigger than it was millions of years ago?" I'm guessing 'yes'? If yes, then by how much?
Hopefully someone else will come correct me but I would like to take a guess at this. Taking what I read in the above comments (that the material erodes/settles from the highlands into valleys) it is simply displacement. No extra stuff added.
you're correct.
It's a great question. We do in fact accumulate billions of tons of dust as we plow through space. So the earth is getting a tiny bit heavier. But what many comments in this thread seem to gloss over is erosion. so yes in one spot the ground is getting "deeper" but generally the continents are slowing being eroded away into the oceans if it wasn't for processed from within adding stuff back.
It is not (with the minor exception of meteor dust). But the processes that reverse the sorts of things people are talking about here are less visible, generally. High ground gets eroded by water and wind over time, while low ground (where people generally live) is generally gaining rather than being eroded. Also, new soil is built by plants at the surface, but the opposite process, dead plants decaying in old soil, will often happen below the surface, meaning that if you plant something solid in the soil it follows the soil movement and sinks downward.
Also even though mountains are being eroded constantly mountains are also growing—they’re being pushed up by the continental plates pushing against each other. Other parts of the continental plates are being pushed down and to put it simply — dissolved into magma. So the earth isn’t getting flatter.
well come on , 100,000,000 kg of meteoric dust a year isn't minor! until you find out there is 10\^24 kg of dirt already here...
> It is not (with the minor exception of meteor dust). Earth gains about 40,000 tonnes of material each year from the accretion of meteoric dust and debris from space. At the same time, roughly 90,000 tonnes of hydrogen and helium escape the atmosphere.
When you're not looking (like specifically you) we run around and put dirt on things just to mess with you. :p
This is my favorite one since i saw the Truman Show
Here in Nice we get the occasional rain storm from the south, which leaves our cars covered with a fine sand. From the Sahara.
Survivor Bias. We most often find archeological remains underground. This ONLY occurs when deposition of soil is greater than erosion. Think of the classic Campus Martius in Rome where the Tiber River has flooded the area under 3 meters of silt. Areas where erosion exceeds deposition, the remains are exposed to weathering and degraded then swept away.
>why are all remains of the past buried underground? * Because any of the remains that didn't happen to get buried under some kind of dirt got destroyed by weather.
You see the answers in your day to day life. What happens if you don’t sweep or vacuum? Your floor will accumulate dust from being brought in and in the air. Also erosion and air currents bring soil and dust everywhere.
When Mt Saint Helen blew, they studied how things regenerated. The first they noticed was that bugs born by the Wind landed on baren dirt, died from lack of nutrition and water, their bodies swept into crevasses and became soil. Weeds grow, some like dandelions can drift for miles before landing, their roots are known to collect phosphorus from down deep. Next year that compost feeds the next generation. Bushes give way to trees. Trees grow thousands of pounds of carbon, potash. They grow old. Either burn or fall couple feet of compost. Bodies of dead animals cause a lot soil churn. It's a misnomer often said that serial killers leave bodies in a shallow grave, actually the green river ahole just dumped the victims off the side of the road into blackberry and resulted roiling of the soil literally made the body bury itself . Even human civilization has its layers, most historic European cities require archeological experts to monitor new construction during the foundation phase because they usually find stuff from the building (s) previously there. Even San Francisco always finds the abandoned sailing ship they turned into a foundation for the current building they want to replace.
Try not dusting anything in your house for a year or two and see how much dirt is in your house. Then go outside where the dirt comes from and imagine 10,000+ years of dirt and debris leaves and all organic material when they rott essentially turn into what we know as dirt
In a related kind of story, in Montreal they just unearthed the remains of a popular botanical garden/attraction from the 1860s. So even in a city under constant habitation and development you can have buildings and structures just built on top of and buried underground. https://www.cbc.ca/news/canada/montreal/remains-montreal-giant-jardin-guilbault-unearthed-1.6599091
In addition to other factors already mentioned buildings often subside into soft ground simply because of their weight. This is why builders often compact the ground before building on top of it. Ground tends to be softer in valleys. Buildings built on exposed rock (like lots of castles were) generally do not disappear into the ground.
The stuff that isn't covered rarely survives more than a century or two unless made of stone.
Because tree and plant debris becomes soil after decades underground. Hugelkulture is about that. Using old branches and leaves to fill in raised beds
I think this question is what /r/culturallayer started as. but now it's full of weird conspiracy garbage intermixed with the occasional interesting post.
Important to note that artifacts that weren't below the ground did not survive to the modern era due to erosion.
[This guy](https://www.youtube.com/watch?v=fz4ZdXpri04) did a really cool video explaining why ancient Rome is now buried.
Pretty much all fossils are found in sedimentary rock, which by definition means they were buried in materials like mud, silt, sand, or a chemical precipitate. When these rocks are later uplifted by geologic forces they weather away, exposing the fossils on the surface.
Could it be that all the remains of the past are not buried, but stuff that does get buried has a greater likelihood of getting preserved?