system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 where does all the earth come from that covers ancient cities which are found underground? E.g. the Roman forums.

I was watching a programme about Rome and was curious as to how ancient cities are buried underground and where all the earth that covers these cities comes from.
gpt
Dirt gets blown by wind, and washed by rain water to cover things. Stone will also sink when the ground gets wet if it is not sitting on bedrock. These three things will slowly bury things over hundreds and thousands of years.