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I've seen several spy or action movies in which, mostly with some satirical undertone, a megalomaniac supervillain threatened the world by the following:

Send some stolen nuclear weapon into Earth's core by some kind of drill. Detonating it will make volcanoes on the whole planet violently erupt, thereby causing huge destructions all over the world.

Apart from the obvious difficulties of deploying the bomb in Earth's core, my question is:

What impact would a nuclear explosion in Earth's core actually have, especially on volcanoes or seismic activity. Or - to what extend could we expect damages given current atomic bomb yields.

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closed as off topic by Sklivvz Feb 23 '13 at 21:58

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I don't have any data, but atomic weapons have very little effect on the earth when they are exploded at the surface. At the centre of the earth, the extra pressure would completely absorb the impact. And then, of course, there is the minor problem of getting the bomb to the centre. The deepest we've ever drilled is 12km. The centre is a bit over 6000km deep - about 500 times deeper. So the mad scientists have some work to do... –  hdhondt Aug 20 '11 at 11:47
    
@hdhondt - Well, not completely true. The detonation pressure of a nuke, depending on the class, is apparently an order or two of magnitude larger than that at the center of the earth. This still does not mean that one could actually drill that deep without melting the drill (and bomb) before you get that deep. –  user3344 Aug 20 '11 at 12:10
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Give me that drilling tech and keep the nukes. We could solve a lot of the earth problems with hdr powerplants. –  Daniel Iankov Aug 20 '11 at 20:31
    
Austin Powers. Yeaaaah! –  Konrad Rudolph Aug 21 '11 at 19:11
    
I would think you would be better served by detonating right at the edge of the mantle. The explosion could create some wave action there on edge of the mantle that might force some magma up throught the weak points... I would think it would need to be a much bigger nuke than we currently have though. –  Chad Aug 22 '11 at 13:26

1 Answer 1

The biggest nuclear bombs release an energy on the order of 100 megatons: http://en.wikipedia.org/wiki/TNT_equivalent

A big earthquake is several gigatons: http://en.wikipedia.org/wiki/Richter_magnitude_scale

A nuclear bomb exploding at the center of the earth (assuming you could get it there, which you obviously can't) would therefore have less effect on volcanoes, etc., than a big earthquake, for two reasons:

  1. it's much weaker, and
  2. it's much farther from the crust, which is where the volcanoes, etc., are.

Factor 2 is such a huge effect that you wouldn't even be able to feel the explosion at the earth's surface, which is 6000 km away from the center. This is true for exactly the same reason that a person in New York can't feel an earthquake in California, thousands of km away.

This is all assuming a single bomb, which is what the OP's question asked about. I also assume that we're talking about bombs that actually exist, rather than hypothetical, more powerful bombs that might exist in the future, since otherwise the question becomes impossible to answer. (Even if you used the US's entire present nuclear arsenal, which is on the order of 100 gigatons http://en.wikipedia.org/wiki/Nuclear_weapons_and_the_United_States , it would only be the equivalent of about a Richter 10.5 earthquake. This would be stronger than any earthquake ever recorded, but it would still not produce perceptible effects at the surface, due to the second of the two factors listed above.)

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In all honesty, there is no limit to how big we can make a thermonuclear bomb. The limit is actually on deliverability. The Tsar bomba required a special airplane and put the crew at great risk (because they needed to get to safety quick enough!). Since deliverability is already impossible in this case, I thought I'd mention it here. –  Sklivvz Aug 20 '11 at 20:10
    
@Sklivvz: Edited my answer to address your comment. –  Ben Crowell Aug 20 '11 at 20:34
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there may be no scientific upper limit, but there certainly is an engineering upper limit in that once you get past a certain volume the detonation starts blasting the bomb (and especially the fusion reaction mass) apart before the fusion reaction can reach it, thus fizzling the bomb. You can probably get that limit extended by increasing the strength of the casing, pressurising the reaction mass, etc., but no doubt you'd still run into limits pretty quickly. The Czar Bomba was likely around the maximum that can be constructed for that reason. –  jwenting Aug 22 '11 at 6:04
    
@jwe: to avoid that you set up multiple stages, once the reaction has started, the blast from the first stage triggers the second stage, etc. The tzar bomba had 3 stages IIRC, but it's certainly possible to upscale the load without materials issues. en.wikipedia.org/wiki/Nuclear_weapon_yield#Yield_limits "If the full 250 metric ton payload of the Antonov An-225 could be used, a 1.3 gigaton bomb could be delivered." –  Sklivvz Aug 22 '11 at 9:28
    
yes, multistage would work to get higher, but how much higher? You'd get the same effect by the stages blowing too far apart to enhance each other (or even to be triggered at all), probably depending on the exact design how soon it'd happen. Nice to see you linking wikipedia as a source btw :) –  jwenting Aug 22 '11 at 11:47

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