Mushroom cloud refers to the powerful explosion cloud generated by explosion. Its shape is similar to mushroom, with large top and small bottom, hence its name. There may be smoke, flames and sundries in the cloud. In modern times, it generally refers to the cloud formed after the explosion of nuclear weapons such as atomic bomb or hydrogen bomb. Volcanic eruptions or celestial impacts may also produce natural mushroom clouds.

A rising cloud of smoke formed when the fireball went out. The reflection and negative suction of the shock wave on the ground near the projection point of the explosion center make the ground lift a huge dust column, and the rising dust column connects with the smoke cloud to form a tall mushroom smoke cloud.

The mushroom cloud suddenly appears a lot of low-pressure hot gas near the ground. The hot air rises rapidly, causing a vortex turning outward and downward, which is called "smoke cloud". At the same time, the vacuum state makes the smoke and sundries turn upward from the center to form a "dust column" (mushroom stem). A large amount of gas finally reaches the height of the same pressure as the surrounding air, and the rolled up sundries disperse and drift down.

Source: @kerr_tattooist