Why do some nuclear detonations leave craters, and others don’t?

Question

Hiroshima and Nagasaki didn’t, but other detonations did, like Castle Bravo.

In: Chemistry

Answer 1

It’s a choice of the person detonating the bomb.

In Japan, the US wanted to damage the largest area with “enough” damage to knock down buildings. An air burst provides high pressure over a larger area, and no crater.

In other situations, you can apply the “most damage” to the ground by setting off the nuke right on it. This was done with a relatively short tower in the Trinity blast, leaving a crater of the glass-like mineral trinitite.