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A major city will leave a pretty big mark, geologically. The structures themselves will fall, but the materials have a good chance, especially concentrated as t
by andrewflnr 3y ago
A major city will leave a pretty big mark, geologically. The structures themselves will fall, but the materials have a good chance, especially concentrated as they are..Lots of artificial stone (concrete), asphalt, metal, artificial materials, plus chemical contamination of surrounding soil. These are things we can detect in much smaller amounts in very old rocks. I'd guess it just needs to be lucky enough to be in a depositional rather than erosive environment for a while so the weather doesn't immediately sweep it away.
- mc32 3y agoDefinitely. There is no way a city like Tokyo or NYC leaves absolutely no evidence civilization existed 100 million years into the future if geology continues to change at the rate it has changed.
- andrewflnr 3y agoI feel the same, but I did stop short of directly claiming it. I'm wondering if in 60my, they might only have an infinitesimal trace, or get subducted or something. I still feel like the major cities can't all be in erosive environments or liable to get their crust recycled, or whatever other processes can fully annihilate them, but I don't know quite enough about geology to be confident over tectonic timescales. Scifi side note: imagine a world so thoroughly altered that even the magma from subducted crust shows signs of civilization.
- marcus_holmes 3y agoI always thought the telltale would be a thin layer of mixed metals in the geological record. Assuming the civilisation lasts a few thousand years then that's a very thin layer 60m years later. And it would contain a lot of iron, copper, tin, lead, etc all mixed together in that thin layer. It would look very weird from a geological point of view.