At the same time those activists likely don't want oil, gas, or coal either. They probably wouldn't enjoy the countryside being covered with solar panels and wi

At the same time those activists likely don't want oil, gas, or coal either. They probably wouldn't enjoy the countryside being covered with solar panels and wind farms. Not sure how you'd win if it's from an activist perspective with some kind of escatological focus ten-thousand years hence used as a mode of attempting social change today. I don't see what the major issue is with burying radioactive waste inside a mountain and then dynamiting and sealing the entrance so it can't be accessed without serious excavation machinery. (Finland is doing this). Uranium is naturally occurring, we've just condensed it a bit. The civilisation that encounters it would need decent technology to dig it up, and if they've gone backward to the point they don't then not much semiology is going to reach them. We also have a reasonable grasp of some of the meaning and motivations inherent in rock art from Aboriginal cultures and Lascaux. Much of that is 10,20,30 thousand years old. Communicating at that distance isn't some impossible task of semiology, but the more one tries to abstract a message into symbolic meaning, the greater the chance of it being misunderstood which is why I'd stand by my point of writing it in English and other languages to give a key. Could carve it into granite alongside a well-rendered image of humans dying and in pain. Humans are pretty smart particularly when determined to understand something. If they're completely illiterate it might even inspire them to realise that language can be encoded as symbols, but I don't know what would have to come about whereby we'd lose that ability now. And if it's got that bad, then a mountain full of uranium is going to be the least of their problems.