Here’s Why Volcano & Atomic Explosions Create Mushroom-Shaped Clouds
Photo 193267744 ©️ Ig0rzh | Dreamstime.com
In a nuclear detonation, the bomb’s blast produces x-rays which ionize and heat the surrounding air, David Dearborn, a physicist at the Lawrence Livermore National Laboratory (LLNL), explains. This produces a “bubble” of gas: otherwise known as a fireball.
Since hot air rises, the fireball does so and picks up dust along the way, forming the mushroom cloud’s stem.
At the top, the center of the fireball—the hottest part—creates a “rolling motion” as it interacts with the external sections of the blast. By the time the bubble has risen to the level of tropopause (the boundary between the troposphere and stratosphere), it encounters material that has more energy than itself. This results in a loss of buoyancy, and the fireball can’t expand vertically anymore. So, it expands horizontally instead, forming the mushroom cap.
There’s a “jet of material that’s being sucked into the vacuum that’s pushing up,” Katie Lundquist, a researcher of computational engineering at the LLNL tells Live Science. “That forms the mushroom cloud on the top and the flatter area within the torus on the bottom.”
As seen in Hiroshima in 1945, a mushroom cloud rose to more than 60,000 feet in the first 10 minutes. Putting this into daily-life context, a majority of passenger planes cruise at around 33,000 feet.
There’s more to it when you delve beyond the surface: phenomena like the Rayleigh-Taylor instability, for example, where a heavy fluid is supported by a lighter one. The hot air shoots through the denser cold air surrounding it, and when this takes place at a central point, the mushroom shape forms.
These clouds aren’t just limited to nuclear explosions; any incident that involves a rapid creation of heat will see them form. You might see them in volcano explosions, too. But this wouldn’t happen if some distant day, for some reason, it was decided that we should blow up the Moon. “You need an atmosphere so they can have that fluid material,” Lunquist said. “It’s not going to happen in a vacuum.”
[via LiveScience, photo 193267744 ©️ Ig0rzh | Dreamstime.com]
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