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In 2068, a nuclear war is fought between the USSR and the USA. 42,000 best bombs are used, and 2,000 megatons are used during the war.

My story takes place mostly in 4 regions of the United States, the southeast, Midwest, southwest, and northwest. It’s been 20 generations since the war, and most people live in small, farming communities, or United city states. There are three powerful nations in the post apocalyptic United States called the Midwestern empire, the Western Federation, and the Florida Republic.

My main character is searching for a large city out in California, that used to be known as Los Angeles. My question is, would this city still be recognizable after 500 years?

By recognizable, I mean: Could you be able to tell a city was once there just by looking forward at it? BTW, just assume that the cities weren’t hit directly by bombs.

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    $\begingroup$ Welcome to WorldBuilding! How do you define "recognizable"? Should there be certain landmarks still visible or just enough to tell "Yepp, here was a city. Once upon a time. Probably..."? If you have a moment please take the tour and visit the help center to learn more about the site. Have fun! $\endgroup$ – Secespitus Mar 14 '18 at 20:46
  • $\begingroup$ You may get some inspiration by playing Fallout, specially from Fallout 3 onwards. Different timeframe, different conditions, but still all about a post-nuclear war United States. Fallout 3 focuses on the Washington Area, while Fallout New Vegas (and Fallout 1 and 2, if I remember well) focus on the areas around California and Nevada. $\endgroup$ – Renan Mar 14 '18 at 20:49
  • $\begingroup$ we are assuming none of these cities were ground 0? $\endgroup$ – Andrey Mar 14 '18 at 21:11
  • $\begingroup$ Yes assume that all theses critics were not hit $\endgroup$ – user48611 Mar 14 '18 at 21:13
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    $\begingroup$ @user48611 What is your concern that you think you need two accounts? Feel free to join chat so we can discuss. chat.stackexchange.com/rooms/17213/the-factory-floor $\endgroup$ – James Mar 15 '18 at 17:48
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Well, I'd have to imagine that in any major nuclear exchange between Russia and the U.S., high-profile targets like Los Angeles would be hit directly several times over. It's the ejection of debris from cities into the stratosphere which would cause the nuclear winter that is feared by scientists.

If, however, we say that Los Angeles were not hit and other major cities were -- thus triggering the nuclear winter scenario -- Los Angeles would likely be recognizable for millennia. The buildings, even left unmaintained, would stand for centuries and their foundations, the streets, the sewage systems, the LA River, etc. would endure for much longer than I would expect the human race to survive at that point. Archaeologists have found human settlements as old as 13 millennia made with vastly inferior technology.

If L.A. were to take several direct hits, however, we might expect that all or almost all of the buildings would be gone, though their debris, the roads, and sewer systems would still leave traces. Over time, especially with the deposition of all of the ash that we might expect in the wake of a nuclear holocaust, it may all be buried. But traces would live on for the foreseeable lifetime of the planet.

As an aside, I'd imagine that farming would be nearly impossible and the prevalence of radiation, both at the surface and in the atmosphere would make human life untenable.

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  • $\begingroup$ LA is really pretty big. Even large 20 MT weapons would only destroy buildings in a small part of it. Completely leveling radius for a 20 MT is about 6.5 km. The LA metro area is about 12,000 square km. You'd need a whole heap of bombs to level the thing $\endgroup$ – zeta-band Mar 14 '18 at 23:51
  • $\begingroup$ @zeta-band, The Tsar Bomba, the largest tested nuke in history, had an estimated 100% destruction radius of 35Km (21.7 miles or 1,479 sqmi). That's 3X the area of L.A. (469 sqmi). $\endgroup$ – JBH Mar 15 '18 at 0:29
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    $\begingroup$ @zeta-band We don't use 20MT bombs anymore. Instead, you launch a missile with 15 300kT warheads and they spread covering the whole area much more effectively. The total amount of power is just 4.5MT, but it completely covers the city. $\endgroup$ – Rekesoft Mar 15 '18 at 12:50
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There is a movie "Life after people" that elaborated into the topic with great detail, math and science. Big buildings will all topple in a century, smaller ones may stand for a few thousand years, if made from stone. Some landmarks, however, may safely wait for a new civilisation. Those are pyramids, Rushmore mountain, some cliffside monasteries. But they would be hardly recognisable at the point. Just some traces of artificiality.

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  • $\begingroup$ This is a good explanation. No one would probably recognize the city if people would not live inside it for that much time and would not care for it. Nature would take over in so many years, animals would live and die there, plants will grow in all the small cracks of all the buildings. Modern build materials like steel and glass are far less resistant to corrosion then classical stone building. $\endgroup$ – Andrei Ioan Danaila Mar 15 '18 at 14:08
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No.

Why not? Because by whom and by what they would need to recognize LA?

For me the only distinctive landmark of LA is Griffith Observatory ( I omit Hollywood sign as this is something that can be overrun by vines in 2 seasons).

20 generations is 400 years (using old method, new one would give you between 500 and 600).

So you need to go back to XVII century and look for building that were abandon around that time and not tended to in 400 years. Usually the castles build in manner similar to observatory are in very bad shape (if noticeable at all). La is famous for it's wild fires. Just imagine that after the war there is one like last year and no firefighters to deal with it. How much is left of LA? And after 100 years? What about 400 years and a fire each 100 years?

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    $\begingroup$ There are roman ruins not tended for 2 millenniums, and still easily recognizable. $\endgroup$ – Bora Mar 15 '18 at 11:49
  • $\begingroup$ @Bora Where? not tended means not grass cutting, no structural reinforcement, salvaging. Have you seen a house with "do not enter, danger of falling apart"? And Griffith Observatory is not build like Pyramids. $\endgroup$ – SZCZERZO KŁY Mar 15 '18 at 12:02
  • $\begingroup$ It doesn't have to be built like pyramids. I, myself, have excavated Byzantine town from Justinian period (6th century AD), which was destroyed and left in that period. You could still easily see the houses preserved up to 2m tall walls, form town quarters, churches, even after the villagers from the surrounding area took lots of the stones for re-use. And the town was in a middle of the forest on a hill. $\endgroup$ – Bora Mar 15 '18 at 12:40

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