Why do large explosions cause mushroom clouds?
Mushroom clouds form as a result of the sudden formation of a large mass of hot low-density gasses near the ground. When the gas rises rapidly it creates vortices curling downward around its edges and drawing up a column of additional smoke and debris in the center to form its “stem”. The gas will eventually reach an altitude where it is no longer less dense than the surrounding air and it will disperse. The debris will be drawn upward from the ground scattering and drifting back down which is the fallout.
