When our species has become extinct, is there anything that would survive long enough to tell the next intelligent species to arise that we were a technological civilization?
If we are talking millions of years it will become more and more unlikely that there will be anything left to find. In those timespans new geological formations happen.
Look at fossils as example. Yes, we have quite a lot of them but they stretch over a couple hundred million years, so imagen the things we don't know about these periods. Now consider that modern humanity has been around for about 12 k years and the chances of researchers finding remains of our infrastructure in many million years by chance become tiny, just like the layers of sediment containing our remains.
What's imho a lot more plausible is, that future researchers might find traces of our lasting impact on the atmosphere aka climate change in Arctic ice and wonder what caused it, prompting them to dig around in geological formations from our period which then might lead to some discovery.
The crust has a few tectonically stable regions that have never slid into the mantle. This is where we've found rocks that date all the way back to 2-3 billion-ish years. We call them geologic shields.
Our current activities would leave chemical markers in these regions that would be detectable for a very, very long time, and could come from no known natural process.
Otherwise you're right, everything else eventually slides into the mantle and gets turned back into magma over a long enough timeframe.
To be fair, the effect of stuff being cycled back into the mantle doesn't destroy every human artifact regardless, given that some of our constructs aren't even on earth. Though I'm not sure that the odds of anyone actually finding one of our space probes is that high, the solar system is a big place after all.
Look at fossils as example. Yes, we have quite a lot of them but they stretch over a couple hundred million years, so imagen the things we don’t know about these periods
I get your point. But then again look at how many fossiles there still are. And those are all biologically, easily degraded. We've build quite sturdy things and even if only a tiny fraction survives there should be plenty for future archeologist to figure out that there was some civilisation at work.
With the extend that humans have changed the planet, we should leave a very obvious geological marker. Like suddenly there is plastic in the sediment layers ...
Like suddenly there is plastic in the sediment layers …
If we were to go extinct today, these layers would be incredible thin. 12 k years of human history is a blink of an eye in terms of geological timeframes and for most of that we didn't produce long lasting materials.