Debunked: 9/11 WTC: AE911's "Pyroclastic Flow" collapse dust clouds

A claim by the promoters of the the 9/11 controlled demolition theory is that the dust clouds that were pushed up and out by the collapse of the building were "pyroclastic-like", specifically:
The reference that AE911Truth uses to back this up is the site 9-11 Research, a web site that was created in 2003 by Jim Hoffman. Hoffman was a seminal figure in the 9/11 Truth movement, and his early writings were highly influential on the shape that the conspiracy theories took over the first decade after the attacks. Some of his early ideas were quite outlandish, such as the suggestion that the Twin Towers were blown up by the carefully timed detonation of 1.8 million individual explosives disguised as ceiling tiles.

The "pyroclastic flow" claim of evidence is another Hoffman invention, but one that the 9/11 Truth community has been unable to let go of. Here's the calculation that Hoffman used to justify the claim:
Metabunk 2018-07-21 07-47-28.jpg

Remember what AE911Truth said, echoing Hoffman, that the expansion of these dust clouds can only be explained "can also be explained only by the expansion of hot gases." Hoffman has a more detailed analysis on his site where he says:
Note this is already based on an unfounded assumption - that mixing with ambient air is "doubtful".

He then proceeds to give a detailed explanation at how he arrives at the very high energy requirements. The base of this calculation is:
The incredible and impossible magnitude of this calculate temperature is perhaps easy to miss at first. A rise from 300 to 1020? But that's in Kelvin. It's actually a rise from 27°C/80°F to 747°C/1,376°F.

This claim can be debunked quite simply by the observation that no such temperatures were observed in the cloud of dust. We've all see videos and photos of the cloud moving down the street, engulfing people and cars, and we've seen the people afterwards covered in dust. 1,300°F is very hot, hot enough to melt aluminum. Any human caught in a cloud of such superheated gas would instantly suffer third degree burns and die. But they didn't.

For example, Dr Mark Heath was filming when the North tower collapsed. On the corner of Murray and West, we was engulfed by the cloud of dust, which was so dense it blacked out all light, and yet he was uninjured.
Metabunk 2018-07-21 09-24-50.jpg

Another example is in this AP Video, shot on the corner of Murray and Church, also during the North tower collapse. Again the dust is so dense it blacks out the sky, but again it's not hot enough to injure anyone despite the dense cloud moving very rapidly along the street
Metabunk 2018-07-21 11-07-55.jpg

Besides this lack of burning heat, there's another problem. Expanding clouds of dust are a common feature in all kinds of building collapses, including those that do no use explosives. Here's a building collapsed in Italy, leaving a cloud to dust several times the size of the building:
Metabunk 2018-07-21 11-26-48.jpg

Here's another earthquake collapse. The roof of a church falls, creating a cloud of dust identical to the WTC cloud with sharp edges, eventually filling the entire church, many times larger than the segment of roof that fell. Yet this is all just from gravity.
Metabunk 2018-07-21 11-33-13.jpg

Rock falls produce similar large clouds from small falls. Here's a rock fall at Yosemite, with identical clouds of dust - much bigger than the falling rocks.
Metabunk 2018-07-21 11-45-58.jpg

Here's a small structure falling over in an Earthquake:
Metabunk 2018-07-21 11-50-28.jpg

And the resultant cloud of dust that raced across the road at high speed, many times larger than the structure that collapsed.

Metabunk 2018-07-21 11-51-07.jpg

And of course building collapses also create these huge clouds without red-hot air expansion. Here's a recent accidental building collapse in Miami, where no explosives were used:

And here's one that used explosives, but the movement of the dust quite clearly comes from the wind created by the falling building.

So what's actually going on with these growing clouds of dust? You have to think of it in terms of fluid mechanics, and you have to think of it in three dimension. The air is a fluid. When the building collapses it pushes down all the air inside the building, and a good amount outside the building. That is not the only air involved though. When that air is pushed down, air above and to the sides of the building rushes in to take its place. This air also gets dragged down. When the air hits the ground it spreads out in all directions.

The first wave of air continues to move under it's momentum, but it's also being pushed by the air that got sucked down, and is also spreading out, kind of like a microburst:
Metabunk 2018-07-21 12-24-04.jpg
So the dust is moving away from the center, because it's being carries by air that is moving away from the center. Does this mean the air is expanding? No, it means the volume of air that contains dust and debris is now larger than it was because the moving air will leave dust and debris behind.

Consider what happens if you throw a cup of flour. Even better than considering it, go and try throwing a cup of flour.

The flour starts out in a very small compact collection of air and flour as it leaves the cup:
Metabunk 2018-07-21 12-58-52.jpg
It very quickly "expands" to ten times it's original size, and yet still has a well defined leading edge
Metabunk 2018-07-21 13-00-33.jpg
It continues:
Metabunk 2018-07-21 13-01-40.jpg
Still has some cauliflower shape to it, and now it's around 50x its original size.

So obviously I'm not heating up the air in the cup. It's just moving.
Last edited:
Expanding a gas that way only requires heating if it's the heat that drives the expansion. The same requirements don't apply to dust driven by kinetic energy.
Any calculations for what energy was required to turn all that concrete into dust?
Compare it again with the rock fall.

Similar cloud, and yet all the rock did not turn to dust. Same thing with the church.

In the WTC not all of the concrete turned to dust either. Lots of dust was generated both during the collapse and when the concrete hit the ground. But the amount seems perfectly consistent with other collapses, so does not indicate anything different.
Last edited:

This video of smoke stacks being toppled is useful context, as when they hit the ground there's no question of any explosives being involved in the dust cloud. The only smoke and force from the explosives is in a small area around the bottom of each chimney.
Metabunk 2018-11-11 09-27-34.jpg

Then it hits the ground:
Metabunk 2018-11-11 09-28-42.jpg

And "pyroclastic-like" dust clouds result, nothing to do with the explosives.
Metabunk 2018-11-11 09-30-30.jpg
Last edited:
There is one reason why I will easily consider the claims of pyroclastic flows as dubious: pyroclastic flows, as far as I know, originate from volcanoes only.
There is one reason why I will easily consider the claims of pyroclastic flows as dubious: pyroclastic flows, as far as I know, originate from volcanoes only.
The claim is that they are "pyroclastic-like", not that they are literally from a volcano. Basically that they can only have been formed by heat.
The claim is that they are "pyroclastic-like", not that they are literally from a volcano. Basically that they can only have been formed by heat.
I see. If that is the case, all that is needed, is to look at the footage taken after these clouds are formed. Since no one is scorched by those clouds....
The claim is that they are "pyroclastic-like", not that they are literally from a volcano. Basically that they can only have been formed by heat.
But pyroclastic flows are mainly powered by gravity, not heat:
A volcynic eruption ejects rock and dust into the atmosphere rather suddenly and at elevation, thus setting the condions for a pyroclastic flow to occur: air mixed with solid material is heavier than surrounding air, thus sinks to the ground, then spreads outwards (is surface is near to flat) or down the slopes. Incidentally, such flows are devilishly hot, but once a dust cloud has formed, it doesn't matter very much whether it's hot or cold.

A tall building collapsing at elevation similarly ejects dust into the surrounding air, this creating a fluid heavier than air - conditions for a gravity current are set, no explosives and no heat needed.

Look for videos of large rock and landslides for references of non-explosive density flows originating from cold geological processes.
Thread starter Related Articles Forum Replies Date
Mick West Debunked: NIST's Lack of Explanation for WTC7 Freefall [They Have One - Column Buckling] 9/11 38
Mick West Debunked: 9/11 Truth New York Times Billboard Quote 9/11 53
Mick West Debunked: Crowder's "Fraud Week" Title Graphic (and Why it Matters) Election 2020 1
JFDee Debunked: Democratic senators complained about 'vote switching' by Dominion voting machines in 2019 Election 2020 2
Mendel Debunked: The Democrats are trying to take away freedom of religion Election 2020 6
H Debunked: Dr. Shiva's Scatterplot Analysis of Michigan Precincts Election 2020 35
Mick West Debunked: Suspicious "Biden Only" Ballots in Georgia Election 2020 3
Mick West Debunked: "Nancy Pelosi's long time Chief of Staff is a key executive at Dominion Voting" Election 2020 0
Mick West Debunked: Wisconsin Turnout 89% Impossible High [Actually 72%] Election 2020 1
Mick West Debunked: Video of Poll Worker "Filling In" Ballots. Election 2020 3
Mick West Debunked: Pentagon has Evidence of "Off-World Vehicles Not Made on this Earth" UFO Videos and Reports from the US Navy 14
derrick06 Debunked: United Nations creates a "NWO" website Conspiracy Theories 2
N Debunked: Google Mail icon shows linkage to Freemasons Conspiracy Theories 4
Mendel Debunked: The WHO did not take the Taiwan CDC seriously Coronavirus COVID-19 0
A Why 9/11 Truthers Are Wrong About The Facts | (Part 1 w/ Mick West) 9/11 1
Mendel Debunked: Radar Waves Affect Clouds General Discussion 0
Pumpernickel Need Debunking: Foucault's Pendulum debunked through Mach's principle (the Earth is a static object in the center of the Universe) Science and Pseudoscience 16
M Ufos arrive to the central zone of Chile. (Debunked). Skydentify - What is that Thing in the Sky? 0
Jesse3959 FE Debunked with water tube level - 187 foot building 21.2 miles away below eye level Flat Earth 0
H Debunked: Cadillac Mountain from 220 miles Flat Earth 7
Jesse3959 FE Claim Debunked: JTolan Epic Gravity Experiment - Flat earther disproves Perspective! (or his instruments.) Flat Earth 0
Mick West Debunked: DoD prepares for martial law in CONUS: Conspiracy Theories 0
Oystein Debunked: AE911T: CNBC Anchor Ron Insana claims Building 7 a Controlled Implosion 9/11 13
A Debunked: NASA tampered with the original television audio of the Apollo 11 moon landing Conspiracy Theories 1
Greylandra Debunked: media headline "Judea declares war on Germany" [boycott] Conspiracy Theories 20
Mick West Discovery Channel's "Contact: Declassified Breakthrough" was debunked 2.5 years ago UFOs, Aliens, Monsters, and the Paranormal 8
Joe Hill Debunked: "The North Face of Building 7 Was Pulled Inward" 9/11 66
A Debunked : Fake Set Moon Landing with TV Camera and Stairs Conspiracy Theories 3
Mick West Debunked: Photo with Sun Rays at Odd Angles Flat Earth 0
Staffan Debunked: Wikileaks releases unused footage of moon landing (Capricorn One movie scenes) Conspiracy Theories 2
Mick West Debunked: Neil deGrasse Tyson : "That Stuff is Flat" Flat Earth 10
Mendel Debunked: Air Map of the World 1945 is a flat Earth map Flat Earth 0
Trailblazer Debunked: Trees being cut down "because they block 5G" (tree replacement in Belgium) 5G and Other EMF Health Concerns 44
deirdre Debunked: Exemption from military service doc proves Jews had foreknowledge of WW2 (fake leaflet) General Discussion 0
Trailblazer Debunked: Obama called Michelle "Michael" in a speech. (Referring to Michael Mullen Jr) Quotes Debunked 0
Rory Debunked: 120-mile shot of San Jacinto proves flat earth Flat Earth 39
Rory Debunked: The Lunar Cycle affects birth rates Health and Quackery 26
Rory Debunked: Study shows link between menstrual cycle and the moon Health and Quackery 30
novatron Debunked: California Wildfires Match the Exactly Path of the Proposed Rail System Wildfires 3
Rory Debunked: "You must love yourself before you love another" - fake Buddha quote Quotes Debunked 7
W Debunked: Qanon claims there have been 51k sealed indictments filed this year. Current Events 11
K Debunked: Audio of David Rockefeller "leaked" speech in 1991 [Audio Simulation] General Discussion 2
tadaaa Debunked: Fake photos-Novichok attack Russian 'agents' (side by side gates) General Discussion 34
Mick West Debunked: XYO Device Replacing GPS, Saving $2 Million a Day General Discussion 23
Mick West Debunked: "Tip Top" as a QAnon Clue from Trump [He's said it before] Conspiracy Theories 5
Whitebeard Debunked: Nibiru FOUND? Mysterious gigantic rogue planet spotted lurking outside our solar system Science and Pseudoscience 1
Mick West Debunked: "There Exists a Shadowy Government" — Daniel Inouye Quotes Debunked 0
Mick West Debunked: Delta Lambda Compression General Discussion 16
MisterB Debunked: Isle of Man from Blackpool at water level proves flat earth [refraction] Flat Earth 19
JFDee Debunked: Wernher von Braun confirmed that rockets can't leave earth Conspiracy Theories 23
Related Articles

Related Articles