system
Given the following post, respond as if you're commenting on Reddit:
human
What happens to the earth/soil beneath large cities over time?

When I visit NYC I can't help but wonder what the conditions are beneath miles of tar and concrete. What are the long term implications?  Have there been many geological studies on this?
gpt
It really really depends on the type of geologic environment you're building on. In NYC, it's mostly alluvial, so the foundations of the buildings go very very deep, whereas in Finland, you can build a highrise just on almost the open ground because the bedrock is on the surface. 

Buildings are no where near heavy enough to cause any kind of geologic phenomena (earthquakes) if that is what you are concerned about.