What would happen to landfills if abandoned for many years?

So it's plausible that any planetary civilizations (alien or human) may have landfills. It is also natural to think that many planetary civilizations would die out, or migrate away from a planet. So in the event that a planet is abandoned, what would happen to landfills (if left alone) for:

1. 1000 years
2. 10,000 years
3. 1,000,000 years

I'm going on the assumption that these planets are not subject to cataclysmic collisions (although meteor events may occur), and that a "year" equals one earth year.

Thank you landfill experts!

posted over 7 years ago

John Watmuff‭

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