Mushroom cloud - Kinokogumo

Japanese: きのこ雲 - きのこぐも

...Within 1× ^10-6 seconds after a nuclear explosion, the superheated nuclear weapon remnants release a large amount of energy, mainly in the form of X-rays. In an air explosion, these X-rays are absorbed by the air within 1m of the explosion, and the extremely heated air and vaporized remnants form a glowing, spherical mass called a fireball. The fireball continues to expand rapidly while emitting radiation and heat rays, and gradually cools. As it rises, it is subjected to air resistance and changes from a spherical shape to a doughnut shape, forming a mushroom cloud of radioactive material (Figure 5). Inside the fireball, the gas produced by the high temperature rapidly expands, generating a shock wave that travels outward. ...

From [Clouds]

…Mount Etna in Sicily is covered with a cloud called the “Countess of the Winds.” Mushroom cloud: A huge mushroom-shaped cloud formed by a volcanic eruption or a large explosive explosion (the most powerful being a nuclear explosion). It starts out spherical, but grows into a cumulus cloud, and may be accompanied by a veil cloud or a thundercloud. …

*Some of the terminology that refers to "mushroom cloud" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

Japanese:

…核爆発後1×10^－6秒以内に，超高温となった核兵器残滓は主としてX線の形で大量のエネルギーを放出するが，空中爆発ではこのX線は1m内外の空気に吸収され，極度に高温となった空気と気化した残滓が火の玉もしくは火球fireballと呼ばれる光り輝く球状の塊を形成する。火の玉は放射線と熱線を放出しつつ，急速に膨張を続けるとともに，しだいに冷却され，上昇によって空気の抵抗を受け球形からドーナツ形に変化し，放射能雲のきのこ雲mushroom cloudを形成する(図5)。　火の玉内部で，高温によって生じた気体の急膨張から衝撃波が発生し外方へ進行する。…