[philipkglass]

Plastic gets consumed by oceanic microorganisms, though slowly. Take a look at the fascinating microscopic images of plastic partially eaten by microorganisms in this 2013 research article, "Life in the Plastisphere: Microbial Communities on Plastic Marine Debris":

http://onemoregeneration.org/wp-content/uploads/2012/07/Life...

Plastics also break down to simpler hydrocarbons and carbon dioxide with prolonged exposure to sunlight. Unfortunately, these gaseous small molecules are greenhouse gases, but they don't persist for as long.

"Production of methane and ethylene from plastic in the environment"

https://journals.plos.org/plosone/article?id=10.1371/journal...

[tatjam]

It's absolutely insane how, if humanity disappeared today, we would become really hard to detect in pretty short time scales.

[tsol]

I imagine the enormous metal structures we put up are the longest standing evidence, simply because metal is normally found unrefined in earth's crust

[haltist]

Metal corrodes. Ever seen an old car sitting in the sun and rain for a long time? It turns to rust and then disappears.