General Question

El_Cadejo's avatar

How do ancient cities get buried?

Asked by El_Cadejo (34382 points ) October 16th, 2008

I mean everyone has read about archaeological digs and how they discover these ancient cities buried by the sands of time.But where does all the dust/sand/dirt come from? Im sure some of this comes from mountains erroding, but it still seems to me like it would take a huge mountain to erode to cover a whole city.

PS im not talking about cities like Pompeii that were located next to a volcano.

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19 Answers

robmandu's avatar

Sometimes, a newer city is simply built on top of the old one.

Magnus's avatar

By bastards with shovels.

Spargett's avatar

Fires tend to be a big culprit of this.

Harp's avatar

There’s a good explanation here.

jvgr's avatar

In adding to robmandu’s note, Jerusalem (inside the walls) was a very hilly city. Every successive conqueror, razed buildings and pushed the rubble into the valleys and started to build their own buildings.

El_Cadejo's avatar

@Harp ahhhh thank you for that link, just what i was looking for.

loser's avatar

I always thought they were just shy.

laureth's avatar

Dirt and dust blow around. There are whole dunes that move around with the wind, slowly but surely. In the 1930s, so much soil blew away from the American heartland that it became known as the “dustbowl.” These are just the big dramatic things we can see, but even over the thousands of years it takes to bury these cities, the little bit of dirt blowing around that we don’t even consciously see can bury it just fine.

A farmer with some marginal land can plant grass, and as his cattle eat the grass, the buildup of humus (good fertile soil) from the dieback of the grass can improve the land enough to make it a good farm in less than a generation. I’m not surprised that some archaeological sites from 30K BCE are found under 9 feet of soil. The steppes are nothing but a dirtbuilding machine!

Next time some fall leaves blow into a corner near your house, check out how they decompose and add just a little to the dirt. If you can imagine a jungle dropping all its leaves every year on a site, you’ll see why they get buried so easily.

AlfredaPrufrock's avatar

This is a really great question! I can see volcanoes erupting, tidal waves, earthquakes, etc. but like why is there a whole city under London, Paris, and New York? I know leaves decompose and create dirt that builds up but you would think that people would notice a foot of dirt outside their door…

That’s a great site, Harp!

El_Cadejo's avatar

@laureth yea i considered the dust and dirt being blown around, but then while some cities were being covered others would have to be uncovered. Another question to consider is if there is decomposing leaves and all building up dirt, is the earth larger than it was before?

harps link pretty much answered this question, just some things i thought about prior to posting the Q

AlfredaPrufrock's avatar

I think it gets redistributed. Matter is neither created nor destroyed.

El_Cadejo's avatar

@alfredaprufrock yes but the earth does accumulate ~10,000 tons of meteor dust a year

elchoopanebre's avatar

Great question, uberbatman. I’ve been wondering this myself.

laureth's avatar

I don’t think people would notice a foot of dirt outside the door when the city has been abandoned for a thousand years.

fireside's avatar

lol, you mean they didn’t leave behind someone to keep the place clean?
not very green of them to just use the land and then take off while there’s space dust accumulating.

El_Cadejo's avatar

Sub question. Why do these cities get abandoned long enough for them to be completely covered in dirt/sand?

obviously this question excludes cities that were built over

laureth's avatar

Very often, back in the day, they’d run out of resources – one of the reasons that one Native American civilization (I can’t remember the name of it, sorry) collapsed and abandoned its city was that they’d used up all the firewood within a few days walk.

Sometimes war can cause a place to be abandoned, because there aren’t any survivors to carry on. This is what’s already happening in places like Darfur, as homes and cities revert back to nature.

Sometimes the environment changes and makes a place inhospitable, like here:

It’s amazing how fast nature can take over a place where people haven’t lived for even a few years. If you’re interested in the subject, I recommend a book: “The Earth Without Us” by Alan Weisman.

El_Cadejo's avatar

awesome answer laureth thanks

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