Would it be possible to detect an industrial civilization in geological record?
Every time this pops up on HN, people post insisting that it won&#x27;t all go away, that the skyscrapers will, somehow, still be there.<p>No, they won&#x27;t. Look at any place in the world where there are mesas. <i>All</i> of the land around the mesa used to be level with the top of the mesa. It has all eroded away, and in only a few million years.<p>So, the metals will corrode, collapse, and wash away. The stone will erode away. The concrete will erode away. The radioactives will decay. It will all end up as a millimeter-thick layer on the sea bottom, one of thousands of millimeter-thick layers with nothing to call attention to itself. Microplastics will abound, but somebody needs to be looking for them in exactly that layer, the way we found iridium at the K-T boundary layer, after specifically looking. There is a huge overabundance of platinum (parts-per-billion) in layers only 12900 years old, just discovered in the past decade, and only because we are really interested in that layer. (It was the start of the 1300-year Younger Dryas cold spell whose end is the start of the Holocene Epoch.)<p>Will <i>anything</i> last? Big mining and quarry pits will fill in, but recognizably. Big mine tunnels will fill in or collapse, but recognizably. A rectangular mine shaft dug down through a thousand meters of sedimentary rock will have no other explanation.<p>Some structures will be buried, instead of eroding away. Those will be deep underground, and then <i>might be</i> exposed again through subsequent erosion or uplift. Again, a brick chimney found buried will have no other explanation, though people will try.<p>Strictly speaking, one is all you need, but some people  (&quot;people&quot;?) need more convincing.