Le Boom

A truck carrying 35,000 lbs of explosives detonated in Utah, blowing an 80-foot crater in U.S. Highway 6. Pics and vid at the link.

For reference, 35,000 lbs is exactly one half the max bombload of a B-52. But this was all explosives, not explosives inside a bomb casing. Being anywhere near it was likely very similar to being near a B-52 strike. I've been three kilometers away from one in 29 Palms, and even at that range you could feel the pressure wave hitting you in the chest. I can't imagine standing a few hundred feet from it.