No, Hans. "Fizzies" is something different from the pyroclastic flow, which is something different from the mushroom cloud. I began this thread because so many posters were conflating the mushroom cloud with the pyroclastic flows. Now you're conflating the fizzies. I use fizzies to refer to the dustifying pieces of steel.
The current "official" definition of "pyroclastic flow" typically specifies a volcanic origin, so the 9/11 events would be excluded by this definition. However, prior to 9/11, this phenomenon had never been observed, except in volcanoes. 9/11 changed that. The reason that the dust-fluid flow from the twin tower events looked like a pyroclastic flow, is that the same factors were at play: A source of solid material, and a tremendous amount of heat energy to render it into a cloud of fine, dense powder, and expand that cloud into characteristic cauliflower shapes that flow downhill rapidly while continuing to expand.
Another poster suggested the term "density flow". Perhaps.
Mushroom cloud refers to what happens to the smoke. It is above the tower. During the "collapse", it begins expanding and rising.
Fizzies are the steel pieces that trail dust, and appear to be disintegrating into dust,while behaving very energetically. They look like rockets. They are hard to miss. This dust material becomes the pyroclastic flow, but fizzies refers specifically to the dustifying steel.
Hope that clears it up.
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