Topic summary
Pyrocumulus cloud
Extracted from the Wikipedia article Flammagenitus cloud.
Hiroshima cloud
The attack also initiated numerous primary and secondary fires which, over time, engulfed much of the city. Over time they merged into a firestorm, and generated a much more massive pyrocumulus cloud. Photographs taken by later US reconnaissance planes captured the massive cloud several hours after the initial attack. This later pyrocumulus cloud, caused by the secondary fires, is often mis-identified as the nuclear mushroom cloud, caused by the initial detonation.