Earth as a whole is essentiallly a closed system right? Nothing leaves except what we send into space and (presumably) no material enters earth except the some space debris.
Where does all the earth/dirt come from to consistently bury historical structure under ground across the world?
In: Planetary Science
There’s three parts to this.
The first is while earth is a closed system, its a system in motion. Erosion and deposition move sand and dirt and even rock around the earth and reshape the land. You might not notice it on a human timescale, but over thousands of years you can see much more notable changes.
The other is survivor bias. Most ancient structures and artifacts are destroyed by nature or by humans who move in over them. The ones that are abandoned and buried are better preserved to be found later, so thats why the bulk of our ancient artifacts and buildings are buried, though not all are. Just to take an example, New York City is around 400 years old, yet you are unlikely to find many buildings that are even 100 years old because humans continually demolish old buildings in favor of new and better ones, or fires happen.
And finally, some of the most important archaeological sites for learning about ancient people and cultures are from places of burial or tombs, which of course, tend to be underground.