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So basically, there’s this giant floating island with a whole kingdom built on it. When the magic that’s holding it up fails, it hits the ground (middle of the ocean) at a high speed. The actual story is set a few thousand years after this, so I’m not worried about the cataclysmic tidal wave from this. I can’t figure out what the actual buildings would look like after being dropped. Would they be entirely removed from their foundations, or just collapsed?

Edit: more information: The island had a medieval-style kingdom built on it. It was built with lots of stone bricks, as well as wood. The island dropped straight down in free fall when magic stopped working all at once.

MooNieu
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Evil Overlord
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    Depends on the speed. – Alexander Aug 04 '20 at 23:28
  • Does this answer your question? How would falling buildings affect the earth? – The Square-Cube Law Aug 04 '20 at 23:51
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    We need to know if it was free fall or if it was slowed by magic, was it straight down or was there sideways movement, what are the buildings made of, how tall were the buildings, and how far it fell. I would be interested in seeing this question answered but this info will help us. – Leviathann Aug 04 '20 at 23:57
  • The island was barely damaged as the builders were smart enough to store a small reserve of magical power to slow down the fall and insure that the place does not get damaged too much. Like a fail safe device you know. – Seallussus Aug 05 '20 at 00:16
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    So, thousands of years later, is the fallen city underwater? Or is it supposed to be floating on the water after the fall somehow so that passersby can see it? – MooNieu Aug 05 '20 at 00:18
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    I don't think there would be anything standing. Including the island. I think what is left of the island would be under the waves. – NomadMaker Aug 05 '20 at 00:22
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    The floating island, after crashing into the sea, became a regular island. – Evil Overlord Aug 05 '20 at 00:23
  • Straight down from how high? And what are the aerodynamics? At one extreme, you have a parachute. At the other, Chicxulub :-) – jamesqf Aug 05 '20 at 00:28
  • Depends on mgh ;D oops I neglect drag – user6760 Aug 05 '20 at 00:56
  • @Evil Overlord - I don’t know for sure, but I think that whether or not it went underwater during the crash (and I imagine it would have) / how far it sank / whether or not it bobbed may have an effect on the state of the buildings by the time the island has settled. May or may not be useful, just something to consider. – MooNieu Aug 05 '20 at 01:18
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    How high up was this floating before falling? And when you say kingdom, what size island are you imagining? 5 miles in diameter? 50? – IronEagle Aug 05 '20 at 01:52
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    @Evil Overlord - For as many of the questions asked in this comment thread that you have or can guesstimate the answers to, you should add that information to your question. It may help you get more answers. – MooNieu Aug 05 '20 at 03:13
  • are the castle made of stacked brick with or without mortar in it? if without, it probably end up with a pile of brick upon falling unless it design with burdock piling like japanese style for example. if it has, i imagine it either still majorly intact (depend on the fall) or has crack, or lose big chunk of it, but the lower base at least remain, think something like greek or roman ruin. – Li Jun Aug 05 '20 at 03:38
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    "Middle of the ocean" is usually pretty deep, so after everything settles it likely just looks like ocean again. – user535733 Aug 05 '20 at 04:44
  • So basically is this a castle, or a floating island with a whole kingdom built on it or does the difference not matter to you?

    Does it hit the ground or the middle of the ocean? The actual story is set where and when and how and why you specify, so you don't need to figure out anything: you dictate all of it.

    If you want realism, what's left is a pile of bricks.

    How could you ask whether buildings that flew by magic you designed would be removed from their foundations or just collapsed?

     – Robbie Goodwin Aug 05 '20 at 22:07

1 Answers1

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So, there are two main loading conditions you need to consider when it hits the water: horizontal and vertical. Both are common on Earth in earthquakes: the horizontal earthquakes are commonly caused by strike-slip faults (like San Andreas), and the vertical earthquakes are caused by normal/reverse faults (like Chile). 1 A horizontal earthquake can, if conditions are right, just move buildings like that magic trick of pulling out a tablecloth from under a bunch of dishes. They are usually not as damaging, but if your island is just falling straight down, the horizontal shaking is likely to be minimal.

The vertical forces, on the other hand, are likely to be much greater. Extreme earthquakes can result in forces as high as 3-5g.2 If your island is massive enough, it might be able to slow down slowly enough to stay around that force.

However, that tidal wave... after the initial "sploosh" out, there will also be a tidal wave coming back into the city. This tidal wave will likely destroy most of your city. For an example, see this high-speed footage: youtube

IronEagle
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