But we're using a lot of the crust. No one will be mining under Atlanta. There are plenty of places we aren't using, but the crust is also thick. A mile down sounds really deep, much less 20 miles.
I mostly agree with you, but it might wind up easier to nab an asteroid than dig a mile under the ocean.
39% of the surface area is used by agriculture, and 3% by urban areas. That excludes oceans & Antartica. Including those, the number drops to less than 10%.
Mining takes up less than 0.05% of the surface area of the earth.
Is Atlanta rich in rare earth minerals or something, or are you just using a random city as an example? I'm aware of various granite mines around the city (such as where they filmed Walking Dead and Stranger Things), but I wouldn't have imagined Georgia to have disproportionately more minerals than other states in the Southeast.
I mostly agree with you, but it might wind up easier to nab an asteroid than dig a mile under the ocean.