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Reading questions of How much TNT needed to blow up Mount Everest and the Moon - and especially the comments below it, I have to ask it:

Can we blow up the sea?

Detonating atomic bomb undersea may look cool but for any sea-level attacks it is not proving anything extra. And It does not "blow up the sea"

So, what is the best way to tactically remove big body of water?

  • It has to happen fast (in matter of hours, one day is maximum)
  • It should be accompanied by some nice effect (boom!)

And, how much would it cost?

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Pavel Janicek
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    you can't really do this without wiping out all life on earth... – James Jan 20 '15 at 14:45
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    Can I ask..defined 'sea'? Is this an ocean reference? Black sea? Any size on this? By blow up...does a hole in the earth that it drains to works? I might have a science fictiony hydrolysis answer that probably sounds good in theory but wouldn't work. – Twelfth Jan 20 '15 at 17:45
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    Lets take the sea definition like this: If it has "sea" in name, then it is sea ;) To be more specific, as European, I would like to get rid of Mediterranean sea – Pavel Janicek Jan 21 '15 at 09:34
  • Remove it? Detonating a bomb on the ground "just" kicks up a lot of dirt... which just falls back to Earth again. Thus, where do you propose removing the water to? – RonJohn Oct 11 '18 at 18:38
  • Obligatory XKCD – Joe Bloggs Oct 11 '18 at 19:01

1 Answers1

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tl;dr: Not without killing everything.

Let's do some maths and actually figure this out.

The specific heat capacity of water is $4.186 \text{ kJkg}^{-1}$. That means it takes 4186 joules of energy to heat 1 kilogram of water up by one degree.

The average temperature of the surface of the sea is 17oC. It gets a lot colder as you go deeper, so the average temperature overall is more like 0.

The seas contain a volume of 1.3 billion cubic kilometres of water. 1 litre of water = 1 kg. 1 litre of water also = 1 dm3, so there are 1000 litres in a cubic metre and thus a cubic metre of water weighs a ton. (This is assuming freshwater to keep the numbers reasonably nice - salt water is heavier.) Then, there are $1000^3 = 1,000,000,000$ cubic metres in one cubic kilometre. That means 1.3 billion billion or 1.3 quadrillion cubic metres of water and the same number of tons, which in turn is $1.3\times 10^{21} \text{ kg}$ or 1.3 quintillion kilograms.

Now let's heat all that up by one degree.

$$ (1.3 \times 10^{21} \text{ kg}) \times 4186 \text{ Jkg}^{-1} = 5.4418 \times 10^{24} \text{ J}$$

Multiply by 100 so we can heat the water to boiling:

$$ = 5.4418 \times 10^{26} \text{ J}$$

Finally, you need around 6x the energy to actually boil it:

$$ = 3.2651 \times 10^{27} \text{ J}$$

Now while that's not quite on the order of blowing up the Earth, that's a hell of a lot of energy. You're in the perfect region for an asteroid impact. We can work out how big and fast it needs to be:

$$ \text{KE} = \frac{1}{2} mv^{2} $$ $$ 2\text{KE} = mv^{2} $$ $$ 6.5301 \times 10^{27} = mv^2 $$

We can play around with mass and velocity. Let's say this asteroid is a perfect 10km cube with 5000kg/m3 density, thus giving it a weight of $5 \times 10^{12} \text{ kg}$. That means its velocity has to be:

$$ v = \sqrt{\frac{6.5301 \times 10^{27}}{5 \times 10^{12}}} $$ $$ v = 36138898.71 \text{ ms}^{-1} $$

or around $0.12c$. That speed isn't insignificant, and while an impact from an asteroid of this size and speed wouldn't destroy Earth, it would most likely make a massive crater, not vaporise the oceans because the energy isn't distributed easily, and kill all life on Earth.

And that's before we start on the water cycle dropping all that steam straight back where it came from.

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ArtOfCode
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    Error: You heated the water to boiling, you didn't boil it. you need roughly 6x the energy you are supplying. Even more overkill. – Loren Pechtel Jan 20 '15 at 19:29
  • @LorenPechtel Ah. Thanks, I'll add that – ArtOfCode Jan 20 '15 at 19:44
  • Yeah, you need energy to do the state transition from liquid->gas as well as energy to actually reach the boiling temperature. – Tim B Jan 20 '15 at 20:44
  • @TimB It's already in there :) Forgot about it – ArtOfCode Jan 20 '15 at 21:44
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    According to this impact simulator, throwing your .12c asteroid at the Earth will completely melt the Earth, making the concept of "crater" a bit meaningless. Note that much of the ocean will be ejected rather than boiled. – Mark Jan 21 '15 at 00:38
  • @Mark It won't melt the earth - see the answer to the question I linked here, that requires a lot more energy. However, you're right that it will eject most of the ocean - that's an effect of the unequal energy distribution I mention. – ArtOfCode Jan 21 '15 at 08:43
  • @Mark The inputs were over slightly. Here's a revised version. – ArtOfCode Jan 21 '15 at 21:21
  • @ArtOfCode, yeah, I messed up on converting a 10km cube into a sphere. – Mark Jan 21 '15 at 22:10
  • How about just lifting the water 20 or 30 meters? – RonJohn Oct 11 '18 at 18:39
  • @RonJohn - Apply some gravity related equations with the mass of all water, and the height to lift, and an energy measurement should come out. – Malady Oct 12 '18 at 02:51
  • @RonJohn Easy one: $E = mgh, m = 1.3 \times 10^{21} \text{kg}$, and Earth's gravity is $9.81 \text{m} \text{s}^{-2}$. To lift the oceans 20 metres: $E = 1.3 \times 10^{21} \times 9.81 \times 20 = 2.55 \times 10^{23} \text{J}$. About 10000x less than you'd need to boil it all - but what would be the point? It'd all just fall right back where it came from. – ArtOfCode Oct 12 '18 at 19:46
  • @ArtOfCode when you blow up a building, pieces fly up in the air and then fall down. What does "blow up the sea" even mean? – RonJohn Oct 12 '18 at 19:52
  • @RonJohn Sure, but the building has been irreversibly deconstructed. Bits of it certainly do fall down, but they won't exactly be in the same place - if you lifted the sea up, it'd all end up back exactly where it came from. – ArtOfCode Oct 13 '18 at 00:48