Pretty strange, a 500 ton TNT sphere about 10 ft. off the ground near Medicine Hat Alberta. They blew up everything from helicopters to houses, and even brought in a bunch of 50ft spruce trees (blew all the needles off!). It was also used to calibrate seismometers world wide, and was timed to the millisecond. Rained 1mm spheres of fused top soil for some time after. Our experiment was an attempt to see how the rising cloud distorted/compressed the atmospheric potential (normally 100v/meter), which might give some better idea of how the electric field behaved on the approach of a thunder storm. We had to drive 30mi on a winding gravel road to the test site on the Canadian tundra every day. Field mice got into our telemetry receiver and gnawed off some of the teflon insulation… after a mad scramble we got it re-wired and back up. I suppose they liked it for the fluoride for their teeth… LOL.
I took this picture just a second or two after detonation.