What is a Mushroom Cloud?

Michael Pollick
Michael Pollick

A mushroom cloud is the ominous formation often seen in the sky following a nuclear explosion or volcanic eruption. This type of cloud derives its name from its resemblance to an actual mushroom, complete with a bulbous top and a centralized stem. Following the dropping of atomic bombs on the Japanese cities of Nagasaki and Hiroshima, the image of a mushroom cloud has become a grim icon for the destructive power of nuclear weapons.

A replica of an atomic bomb.
A replica of an atomic bomb.

When an atomic bomb is dropped over its target, it does not hit the ground and explode. This would force much of the bomb's destructive force into the earth, not through the buildings above it. Instead, an atomic bomb is detonated several thousand feet in the air. The force of this blast instantly pulverizes anything in the blast area into dust and debris. Meanwhile, a ball of super hot gases forms instantly in the sky, which destabilizes the surrounding air and creates powerful currents.

The mushroom cloud produced by a hydrogen bomb detonation can reach high into the atmosphere.
The mushroom cloud produced by a hydrogen bomb detonation can reach high into the atmosphere.

All of this happens within milliseconds of the explosion itself. The superheated ball of gas forms the top of the mushroom cloud as it rises in the atmosphere. Meanwhile, dust and debris are drawn upwards as a column of air rushes in to fill the gap created by the rising fireball. This is essentially the "stalk" of the cloud. There is little to no actual water vapor in the cloud; it is almost entirely composed of dust and debris. Eventually, however, water vapor may combine with the remnants of a mushroom cloud to form a deadly form of radioactive rain called nuclear fallout.

As the head of the mushroom rises in the atmosphere, it eventually reaches a point where the air above is more stable and less penetrable. This causes the fireball to spread out in all directions, forming the very distinctive shape of a mushroom cloud. Convection currents created by the fireball as it rose in the air also force the outer edges of the cloud's cap to curl under and be drawn back into the central stalk.

A mushroom cloud generally forms only when a significant amount of explosive energy and heat are released. A few large conventional bombs can create small mushroom clouds under the right conditions, but generally the only events capable of producing a visible mushroom cloud are above-ground nuclear explosions and major volcanic eruptions. Fortunately, most of us should be able to avoid experiencing either one of those options during our own lifetimes.

A mushroom cloud could be caused by a volcanic eruption.
A mushroom cloud could be caused by a volcanic eruption.
Michael Pollick
Michael Pollick

A regular wiseGEEK contributor, Michael enjoys doing research in order to satisfy his wide-ranging curiosity about a variety of arcane topics. Before becoming a professional writer, Michael worked as an English tutor, poet, voice-over artist, and DJ.

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Discussion Comments


@bythewell - In some ways it is actually a wonder thing that a nuclear bomb has such horrific consequences. That is the only thing that has kept it from being used to kill billions of people, I suspect.

Because when it comes to war, killing lots of the other guy, or even lots of your own guys is not considered such a bad thing.

Potentially killing the entire world is. If there was a weapon that didn't create a nuclear mushroom cloud of radiation, but still killed just as many people, and perhaps destroyed a city or two at the same time, I'm sure they would have used it during the cold war.

Whereas, in the end, they didn't dare to use a nuclear weapon.

And thank God for that.


I hope we are all able to avoid experiencing a real mushroom cloud. They often get depicted in movies as something going on in the background to the real action, but a mushroom cloud within sight of you pretty much means you and everything around you will soon be dead.

If not from the blast itself, then from the radiation and fallout. That cloud is pushing radioactive dust high into the atmosphere where it can get blown for thousands of kilometers. They still don't know all the long term damage that can be done from this, although people in Japan still have increased rates of cancer and other disease.

If a nuclear bomb just killed people that would be bad enough. The fact that it also does such massive long term damage to the environment and everything that lives in it makes it horrific.

I almost wish they would develop some kind of equivalent killer without the radiation fallout so that a nuclear war didn't pretty much mean the end of the future for everyone.

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