Many of the salt flats in the Western USA used to be great lakes as recently as a few thousand years ago. What is now "a dry salt water lake bed a hundred miles from drinkable water" could very well become abundant land in 10,000 years.
This is a really good point. Going back a mere 20,000 years there was an ice age, glaciers covered much of north america, and you could walk on land from China to Australia. Burying stuff with a half life of 25,000 years means that in 25,000 years there's going to be 1/2 as much, not none. After 150,000 years there will be 1.5% left. For super radioactive stuff that you have piles and piles of that's still a huge threat! It is absolutely impossible to build something that can protect this waste as long as it is dangerous because we are talking about time scales over which a lot of geological change occurs. There might even be comet strikes. The only responsible thing to do is to process it into waste with shorter half lifes, which is something we know how to do. Building a monument and pretending it is safe is just a fantasy we tell ourselves to sleep at night while we are poisoning the future.
