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Atomic bombs make mushroom. It's well-known and we've seen many images of atomic experiments around the world. My question is, why mushroom? Does TNT and Grenade also make mini-mushrooms? Is it a physical attribute of explosion, or something specific to atomic energy?

Thanks

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It's a consequence of the dynamics of large explosions, see this video for a non-nuclear example. There is more information about fireball dynamics in this Wikipedia article. –  mmc Jul 17 '11 at 18:20
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More precisely its a attibute of sudden heat evolved. An explosion with a bang is not necessary. A small pile of gun powder will burn quickly, but not "explode". Nevertheless a mushroom is formed. –  Georg Jul 17 '11 at 18:26
    
@Georg Yes, the heat release only needs to be fast enough to form a fireball. –  mmc Jul 17 '11 at 18:31
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@mmc, why didn't you answer this question instead of commenting? Your comment was exactly what I wanted. Thanks :) –  Saeed Neamati Jul 17 '11 at 18:45
    
exact mmc, you should have answered. I found now that my answer did not add much on your own. But there is no need for a blast as you see in my answer. –  Helder Velez Jul 17 '11 at 21:56

1 Answer 1

Its due to the WP-Rayleigh–Taylor instability: it is an instability of an interface between two fluids of different densities, which occurs when the lighter fluid is pushing the heavier fluid.
Hot hair raises and colder goes down.
A Mushroom cloud formed by hot wet air :
enter image description here
google for images or videos of 'Rayleigh–Taylor'

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Indeed the garden variety "anvil" cloud that forms over thundershower cells on the plains in another relatively low energy example. –  dmckee Jul 17 '11 at 23:38
    
In the recent great explosion of dynamite in Cyprus a mushroom cloud appeared, the hole was 20 meters with a 50 meter diameter as reported in the news, also that it was about 1/10 of the hiroshima bomb strength . –  anna v Jul 18 '11 at 14:43
    
Interestingly I just saw one of these tonight... –  David Z Jul 19 '11 at 3:50

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