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To be clear, I'm talking about apocalyptic events that cause devastating long-term effects, such as:

  • An asteroid impact (lets say about 4.5km wide)
  • A hyper-eruption from a super volcano (lets say it erupts 2,500-3,000 km3 of debris)

Not the typical nuclear war aftermath, not particularly interested in that.

Another thing to consider is that humans would not be capable of repairing, maintaining, or salvaging the buildings/cities (at least, not much) because they'd either be dead or underground.

Cities would just be virtually gone. There's almost nothing visually recognizable about them when you go to — for example — Los Angeles, California.

There may be evidence that the cities were there, of course, but what you see initially is either a flatland, a beach, hilly terrain, forests, etc.

So, my main question is: how many years would it take for this to happen after such events?

Side question(s): would the wrecked buildings still be there after, say, 200 years? Would they be gone? Or simply unrecognizable? How unrecognizable would they be?

Here's some cities I'm curious about, if examples are needed:

  1. Seattle
  2. Los Angeles
  3. New York City
Joachim
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Derek Walker
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    Just one question at a time please as per the [help]. At the moment your questions all have answers, the broadest being here, and here. It's worth using the search at the top of the site before asking. – Escaped dental patient. Feb 24 '22 at 23:14
  • Do you want the apocalyptic event to be directly responsible for buildings' destruction, or they should deteriorate on their own after long exposure to elements? – Alexander Feb 24 '22 at 23:25
  • @Alexander Both. How the apocalyptic event would affect cities and buildings, and how they would deteriorate with exposure to elements, as well as no maintenance being available. – Derek Walker Feb 24 '22 at 23:41
  • @EveninginGethsemane My apologies! :( I was just trying to be as specific to what I was looking for as possible, is all. – Derek Walker Feb 24 '22 at 23:42
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    The TV series Life After People answers all your questions. https://en.wikipedia.org/wiki/Life_After_People – RonJohn Feb 24 '22 at 23:42
  • If you want to consider direct apocalyptic effect, number of scenarios multiply considerably. For example, asteroid impact may hit New York straight on, or at some distance, or cause giant tsunami, or produce only a negligible effect - in those cases the longevity of the city would vary from seconds to thousands of years. – Alexander Feb 25 '22 at 00:07
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    look at the towns around Chernobyl it does not take that long. – John Feb 25 '22 at 00:44
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    Your side question, there are plenty of ruins around Europe that have been ruins for far longer than 200 years are still there and are still clearly recognisable as once having been buildings so the real and very obvious world evidence is a resounding yes, it's almost like you didn't give that bit even the most cursory thought while others can disappear without trace in less than a hundred years, it depends on several factors including the building materials, local environment, fauna, flora and climate. – Pelinore Feb 25 '22 at 01:59
  • This doesn't have to be closed but it should be edited choose one city specifically. As depending on what you choose the answer may be different different cities have different building materials . – Bryan McClure Feb 25 '22 at 03:33
  • Also Check out the television Documentary Earth without people. – Bryan McClure Feb 25 '22 at 03:35
  • It is better to limit this question to one particular city: The speed of the city's disappearance will depend on structures within it and local weather and climate. Side questions are fine with me as they are just elaborations on the main question. – Otkin Feb 25 '22 at 04:37
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    Does this answer your question? How long would it take for a forest ecosystem to overtake New York City? – codeMonkey Feb 25 '22 at 15:28

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Welcome I will try to answer this question as best I can in short not long most modern buildings aren't made to last. Well the exact rate depends on the environment and building material of each certainly in most case most of the city wouldn't last the first few decades without human maintenance. Most of rest would be lucky to last the first hundred years.

However older buildings and monuments would last long (how long would depends on each individual case). The longest I know is the Washington monument which is estimated to last 2 thousand years after human existion.

I strongly recommend the documentary life after people. It can give a much better answer. I'll try and find to post the link later

Bryan McClure
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