First Atom Bomb - Little Boy

1. The Huge Atomic Cloud / The Mushroom Cloud Blowing Up

The atomic cloud (mushroom cloud) produced just after the burst is one of the most intensive characteristics of the A-bomb explosion.

The Hiroshima Meteorological Observatory reported that just after the flash, black smoke rose from the ground up to the sky reaching an altitude of several thousand meters, and covered the whole city. When the fireball disappeared, the angry clouds, like grey smoke, rose and reached an altitude of 8,000 meters in 5 minutes after the explosion.

One of the EnolaGay crew recorded in his flight diary, "9:00a.m.....Clouds were observed. Altitude of 12,000 meters or more." From a distance the cloud formation looked like a mushroom growing out of the ground, with white cloud at the top and yellowish clouds enveloping reddish-black clouds, creating a color that cannot be described as while, black, red or yellow.

In Nagasaki, from an observation point at the air-raid lookout post on Kouyagi Island located about 8 kilometers south of the city, just after the flash it appeared that a huge fireball covered the city, as if it were suppressing the city from the sky. Around the fireball there was a doughnut-shaped ring from the midst of which black smoke and flames rose up to the sky in an instant. The ring of the flames did not initially reach the ground. When the fireball scattered with a flash, the city was covered with darkness. The smoke rising from the midst of the ring, glittering in colors of red, white and yellow, reached an altitude of 8,000 meters in only 3 or 4 seconds.

After reaching an altitude of 8,000 meters, the smoke ascended more slowly and took about 30 seconds to reach an altitude of 12,000 meters. Then, the mass of smoke gradually discolored and scattered in wads of white clouds.
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