How has archeology a thing? Why is so much of our history found under the ground we reside today? Why do we have to dig down to find ancient towns? What happened?
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Manmade feature that aren’t buried tend to erode and degrade and are lost to time unless they are truly enormous and sturdy like the Great Pyramids or Roman architecture. Things that are buried by deposition, avalanche, mud slide or any number of other geological forces tend to be preserved.
Well, it’s not going to be floating in the air, and most of what’s on the surface is paved over or worn away. All that’s left is what’s beneath the ground, even if it’s relatively little.
The stuff that *is* paved over often ends up being what’s under the ground, specifically because we just built over the top of it.
Wind carries sand from the Sahara all the way to Scandinavia. Rivers carry rock all the way from the top of a mountain to the ocean.
The world is constantly changing. If we don’t use/clean our streets, a layer of dust would be clear within weeks. Imagine what years and years and years of those thin layers would accomplish. What two millennia of sediment would do.
That’s the first part of it.
There’s also the fact that a lot of soil, specifically near the ocean, is soggy. There are artefacts from Roman legion buried beneath ground that was a swamp 2000 years ago. It sank back then, and the ground dried up.
Edit; and like others have pointed out, the stuff on the surface erodes leaving only the buried things. It’s the already buried stuff that gets buried deeper.
I always thought it would be all that millenia of seasons changing, fauna decomposing on abandoned sites, wind bringing more natural debris until its all buried. Have you seen how fast nature takes over an abandoned site, imagine years and years worth of that happening
There are generally two options for places:
* Wind and water remove more material than they add, the place gets eroded over time, ancient things are gone. This is a very common for mountains.
* Wind and water add more material than they remove, things tend to get buried over time, you have to dig to reach them. This tends to be more common in places where people live (or used to live), because often the same places are also nice for agriculture.
If humans actively maintain the place then you can stop these processes, that’s how you end up with 2000+ year old ruins on the surface – but that needs continuous interest in the buildings or what’s left of them after centuries.
Only a small part of it is, but all the rest has been destroyed by being in the way of newer stuff, so this small part is the only part that is left.
Also: dust
In green areas new dirt and dust is constantly being created that ends on top of whats there. Unless wind or some other factor clears it.
Think leaves, grass and sticks, dust and sand from the wind, bodies from insects and animals etc.
More old buildings collapse causing the top till in the foundation naturally leading to burying.
A huge amount of civilisation lives near rivers which flood leaving huge deposits of mud and silt burying everything.
Etc etc.
There are places where the opposite happens like mountain tops that get more and more exposed over time.
Ever heard the phrase “When the dust settles”?
That. A lot of that. Centuries of that.
The way erosion and deposition works is that material is taken from one place and dropped in another place. We do not find stuff in the place where it is taken away and moved to somewhere else (it is gone). When material erodes, it is lost.
On the other hand, though, that dirt ends up somewhere, generally in valleys and on the plains (wind and water are dumping dust, silt, sand everywhere, all the time, even if it is fairly slow in our terms). Thus, if there is going to be something left to find, it is because it got buried rather than eroded away. We only find what got buried, and thus protected against erosion. The stuff that wasn’t buried? Can’t find it because it is gone, broken up into tiny bits and scattered across the face of the earth.
Sometimes, structures made by man are exposed to wind and water and ought to be eroded away, but the walls and other features create traps for sediment, and mounds develop where humans once lived, so not everything we find was once in a low area at the start. Sometimes, our constructions are sediment traps and sediment settles down where it normally would not have done if not for the walls or whatever.
Think about how buildings sometimes act to make snowdrifts in winter (can even bury a building), but sometimes the buildings actually make it so the snow is scoured away and the building is surrounded by no snow at all (all the snow got blown away next to the building). Dirt does the same thing but is a lot slower to accumulate or erode.
Aside from the redistribution of dust mentioned by others …
Charles Darwin once spent some time measuring worm casts, and concluded that topsoil gets turned over pretty quickly. (I think he reported this in a standalone paper, not part of one of his books.) As it’s churning, solid stuff on the surface eventually is not on the surface.
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