Above ground sites are looted, plowed under repurposed or preserved. The only salvation for artifacts is to be either overgrown with jungle or buried beneath the earth, water or dunes.

Windswept soil doesn’t cover everything, but it accumulates in places.

Things like garbage dumps and tells just have more stuff thrown over them.

My dogs dig up things in my parents’ backyard that I haven’t seen since I was seven or eight years old.

Because things are built on top of other things.

Dirt and debris accumulate over the years until things get covered up.
On a similar note, all of the fine fertile soil that grows wheat in Eastern Washington state, got blown in over the eons from places like China.

In ‘cities’ where people have lived for millenia it is common in human history to put a new building on top of whatever is there, like an old fallen-over building.
That’s why some of these discoveries happen on construction digs where there are layers of civilization in the place.

Space dust
Volcanic ash
Erosion
Comic answer, when ancient people were done with a place, they did nice like a cat, and kicked sand over it.

The specific cause of each place’s burial depends on the place. Air and wind move dirt, ash, plant matter that becomes dirt, etc., around, which can accumulate over thousands of years in abandoned places.

But consider that of all the ancient places, the ones which happen to get buried, get hidden from view and disturbance by that dirt. It’s not that every ancient place got buried. It’s that the buried ones are the ones that have been preserved and kept from earlier discovery by that dirt.

So it’s not that “everything that once existed” was buried. It’s that the buried places got protected from other types of destruction and from discovery. Most places weren’t buried – but those places are already known and/or were more taken apart by people.

@flutherother Why are ancient ruins always found buried…?

If it wasn’t buried then it wouldn’t be lost.

@flutherother Don’t mean to derail your question in the GENERAL category. But is it acceptable to use “feet” underground where you are, or is that designation made for us in the U.S.? Would you normally use the metric system in discussing archaeological digs?

I am actually interested in how such finds in ruins and digs would be discussed in Europe and the Middle East.

@Yellowdog We use both systems over here.

Some sites such as Skara Brae were covered by blown sand others like Herculaneum were submerged in volcanic ash but that doesn’t explain why so many other sites end up being buried in the earth. The deeper you dig the older the things you find. Could plants be responsible? They grow by taking carbon from the air and water from the rain – raw materials that are virtually inexhaustible. When they die they rot into mould or dust that builds up over time.