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!

  • 3
    $\begingroup$ This seems plenty on topic to me. I would suggest that you add a bit more information. Are we talking industrial waste or your standard landfill for residential garbage? $\endgroup$
    – James
    Commented May 17, 2017 at 20:59
  • 2
    $\begingroup$ If it is about landfills on Earth, it's hardly world building. If it is about all kinds of sci-fi planets that could have sci-fi landfills, then it is way too broad. $\endgroup$
    – Mołot
    Commented May 17, 2017 at 21:42
  • $\begingroup$ It's in no way natural to assume civilizations would abandone their planet, ever. Bar obviously things like supernovas but even then. At best you get failed colonies. It's still far cheaper to 'fix' Earth then terraform Mars. It's never cheaper to go elsewhere then the environment you evolved in. $\endgroup$
    – Mormacil
    Commented May 17, 2017 at 21:49
  • 1
    $\begingroup$ While an interesting question I feel that this may be a little too open ended. if you could elaborate on the specific needs of your story that lead to this question it would be easier to answer. Are you thinking of a specific civilization, specific technology level, specific cause of abandoning their planet? As it is this is just a bit too wide open. $\endgroup$
    – dsollen
    Commented May 17, 2017 at 22:20
  • $\begingroup$ A modern, Western dump that's been created with a liner and methane vents, then sealed when full, or... one that's not so modern? $\endgroup$
    – RonJohn
    Commented May 18, 2017 at 1:26

1 Answer 1

  • One thousand years:

    Paper will be mostly gone, converted to hydrocarbons and reused by the micro-organisms. Most plastic too, but some pieces of plastic may be still recognizable. Metals, ceramics and glass will still be recognizable. Even some food will be still recognizable.

  • Ten thousand years:

    Plastic and paper will be gone, converted to hydrocarbons and escaping. Metals will most likely be converted to oxides mixed with the surrounding dirt, but some metal pieces will still be recognizable. Ceramics will most likely still be recognizable, as will be some rare pieces of glass. Rare pieces of food may have been mineralized and become subfossils.

  • One million years:

    Just about nothing man-made will be detectable. Maybe some pieces of glass will still be recognizable, maybe some radioactive materials will stand out a little over the background, maybe some gold pieces. Everything else will be rock or dirt. Ceramics will be just ordinary dirt. Metals, plastic and paper will have reverted to their natural state -- oxides (that is, ore) and hydrocarbons (mainly methane and butane gas). Some exceedingly rare pieces of food and plastics may have become fossils.

For practical examples, see midden (old dumps for domestic waste much loved by archaeologists) and tell (low rounded hills which form when a city is abandoned to the elements for a few thousand years).

  • $\begingroup$ Since modern landfills are sealed, I wonder if the decay will not progress much at all. $\endgroup$
    – JDługosz
    Commented May 17, 2017 at 22:58
  • 1
    $\begingroup$ @JDługosz: They are not sealed in such a way as to insulate them over millenia, much less over geological timespans. Basically, they are insulated with ephemeral stuff such as concrete, asphalt or vinyl, or are covered by an even more ephemeral impermeable surface layer. Those are not expected to last more than a few centuries at best. $\endgroup$
    – AlexP
    Commented May 17, 2017 at 23:16
  • $\begingroup$ So it might affect the 1000 year mark: it may be found to be only recently breached, showing the beginnings of decay on one side. But can still read the phone books on the opposite end. $\endgroup$
    – JDługosz
    Commented May 17, 2017 at 23:22
  • $\begingroup$ thanks for the thorough answer, this was great! those wiki links are perfect. $\endgroup$ Commented May 18, 2017 at 2:22

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