A) Gosh, I wonder why so few purchases in Nevada. Can you say "Nevada Test Site" boys and girls?
B) Mushroom clouds for the homeless: it is probably a little known factoid (at least among the general population) that a "mushroom cloud" only occurs when there is a surface-burst or a near-surface-burst. Yes, the cloud is made up of some stuff from the "Gadget" but that could be, sometimes, perhaps only a couple of hundreds of pounds worth of stuff. On the other hand, if you blow up one of these puppies real close to, say, dirt then a HUGE!!!! amount of stuff gets shoved around very hard, dislodged, mucked with, and generally disturbed. It is then sucked up in the rising column of Really Hot Stuff (by that, I mean picante, not caliente, more-or-less - I'll let you figure out what that means.) The word for this process is "invection".
The same thing happens with water, of course (just look at pictures from the Crossroads Baker shot : put the following URL back into shape and see the interesting picture - http://www.atlasmissilesilo.com/Photos/NuclearTesting/OperationCrossroads/ShotBaker/OperationCrossroads_ShotBaker_Photo001.jpg ). That particular "Event" scared the living daylights out of the people who were running the operation not merely because the bomb itself ended up being far more energetic than they expected, but how the environment acted in such a way as to, in effect, amplify the explosion.
Anyhow, after all that blither, any bomb that explodes at a "respectable" distance above the surface generates something that is essentially only a sphere (sometimes a slightly flattened one) and not the overly-well-known 'shroom. Often, other than being extremely bright, they are rather boring images and afterward tend to look like nothing more than a cloud.
Nabbed one anyhow.