Busting Jeff King's chops on "pyroclastic flow" meme.

[Gazpacho]

What about the opinion of Herbert Huppert, Professor of Theoretical Geophysics at Cambridge University. He wrote this regarding the events on 9/11,

"Aside from natural events, a very tragic example of a pyroclastic flow is what happened on the 11th of September, 2001. Huge amounts of rubble were brought up into the air as the Twin Towers collapsed, the rubble-laden air was heavier than the surrounding air, and it propagated down the streets of New York very rapidly. Some people died as a result of asphyxiation many blocks away, because people's lungs can't cope with very many particles in the air they breathe. From the point of view of fluid mechanics, the questions that were of interest were how quickly the concentration of particulates would decrease, and also how far would the flow travel. It didn't go all the way to Upper Manhattan, but it did go quite a way."

Is this guy way out of his field? Should only morons listen to him?

It's not enough to listen. You have to think about what's said.

Huppert calling something a pyroclastic flow does not make it one. There is a term for the movement of matter from high density to low density. It is diffusion. People here are defining a pyroclastic flow as a volcanic phenomenon because that is the definition.

 

[Mr.D]

"Some people died as a result of asphyxiation many blocks away, because people's lungs can't cope with very many particles in the air they breathe. From the point of view of fluid mechanics, the questions that were of interest were how quickly the concentration of particulates would decrease, and also how far would the flow travel."

Stop phrase hunting and READ FOR COMPREHENSION.

I mean really.

Prof Huppert is clearly using the term "pyroclastic flow" as a form of limited analogy. If he meant it literally, he'd have to point out that people wouldn't have had time to asphyxiate, since they would have been instantly killed by the temperature.

 

[gumboot]

I would argue that those describing the dust cloud from the WTC as like a pyroclastic flow are indeed in the wrong, and indeed should know better.

A pyroclastic flow is defined to two key features - hot gases and very high speeds. Neither of these two features were present at the WTC. Dust or debris is not a defining characteristic of a pyroclastic flow, and those using the pyroclastic flow analogy when talking of dust clouds are, IMHO, using a very poor analogy.

 

[Hokulele]

Regarding Herbert Huppart, his article is discussing fluid mechanics, and the section you quoted specifically was regarding gravity flows. In my opinion, you can read this quote (in context of course) two ways.

1) He meant to use the phrase gravity flow, but as he had just finished defining and describing pyroclastic flows as one example of a particle-driven gravity current, he entered the wrong phrase by accident. As this is not a peer-reviewed journal, but a casual newsletter, and since copy-editors are not necessarily scientists, the error was missed before publication.

2) He really did mean pyroclastic flow, and is an idiot.

Judging by his accurate description of pyroclastic flows just a few paragraphs earlier, I would personally choose option one.

Link to original article.

 

[Hokulele]

I would argue that those describing the dust cloud from the WTC as like a pyroclastic flow are indeed in the wrong, and indeed should know better.

A pyroclastic flow is defined to two key features - hot gases and very high speeds. Neither of these two features were present at the WTC. Dust or debris is not a defining characteristic of a pyroclastic flow, and those using the pyroclastic flow analogy when talking of dust clouds are, IMHO, using a very poor analogy.

I would agree for the most part, however the paper almost cited by tanabear was describing the after-effects of the dust and debris cloud, rather than the cloud itself (i.e., damage to the adjacent buildings). I can see the justification for using the analogy they did, and find it unfortunate that it has been twisted out of recognition and applied to the event rather than the results.

 

[gc051360]

I respond to literal interpretation words like "explosion" and "like a bomb" and claims of pyroclastic flow with this:

If the members of the "Truth Movement" ever learn what is meant by "simile" and metaphor" and how they were used when eyewitnesses to WTC described what they saw, the entire movement would blow away in a pyroclastic cloud with a noise like a freight train.
​

Here's a note I have on Jeff King.

http://home.comcast.net/~jeffrey.king2/wsb/html/view.cgi-about.html-.html

Biographical Note:

PlaguePuppy is the nom-de-net of Jeffrey King, a 50-something former engineer (MIT class of '74, about 10 years in electronics and electro-mechanical engineering), gainfully employed as a family physician for the past 25 years. See here for more details:

http://www.plaguepuppy.net/public_html/Confronting the Evidence/index.htm#Pupp

​

I had kind of a pseudo debate with Plague Puppy on Youtube.

He kept up the guise of being interested in science for a little while, but he started spilling out with all kinds of conspiracy theorist nonsense, and anti-Bush rhetoric. It was a lot like arguing with any truther.

Starts off as pretending to be interested in facts, and debate. And then goes on a hate filled diatribe against the neo-cons, and the bohemian grove, and all this other stuff.

 

[leftysergeant]

Huppert may just lack the language skills or the breadth of vision to pull in a seemingly un-related phenomenon to explain the phenomena observed. The fact that turbidity flows usually occur in water and pyroclastic flows in air may get in the way of even some reasonably intelligent engineers.

The dust clouds were more similar to the matter involved in a turbidity flow than to that involved in a pyroclastic flow. Pyroclastic material is formed in great heat. Turdidity flow material is just what was sitting around until it was set in motion.

King takes theCD. But the dust in CD, for the most part, is not created by the explosives used, but by the collision of concrete with concrete as the building collapses.

Add to this that dry wall is normally removed before CD to reduce the dust, and that the insulating foam probably would be as well, and you can see why there would be far more material available to become dust in the WTC and that this material would requiore far less explosive force than a CD would normallty produce to reduce it to dust.

It is a turbidity flow, regardless what a dilletant like King may call it.

 

[gumboot]

I should point out that while using Pyroclastic Flow is a poor analogy and deserves a rap on the knuckles, actually claiming that there was a Pyroclastic Flow at the WTC on 9/11 is altogether a different magnitude of stupid.

And to claim that the two different remarks cited above are actually the same is yet another example of impressive stupidity.

 

[rwguinn]

I would argue that those describing the dust cloud from the WTC as like a pyroclastic flow are indeed in the wrong, and indeed should know better.

A pyroclastic flow is defined to two key features - hot gases and very high speeds. Neither of these two features were present at the WTC. Dust or debris is not a defining characteristic of a pyroclastic flow, and those using the pyroclastic flow analogy when talking of dust clouds are, IMHO, using a very poor analogy.

Gum:
The high speed comes from (here we go again!) gravity.
The stuff is falling, and the only way it builds up speed is by gravitational acceleration.
So the speeds would be very similar for pyroclastic flow and the clouds of debris , dust and air from the towers, for a similar drop distance.

 

[Hokulele]

I should point out that while using Pyroclastic Flow is a poor analogy and deserves a rap on the knuckles, actually claiming that there was a Pyroclastic Flow at the WTC on 9/11 is altogether a different magnitude of stupid.

To be fair to the authors cited in this thread so far, the first group was making an analogy to the end result, not the process, and in reading the article by the second author, it really looks to me more like a simple error than an analogy.

And to claim that the two different remarks cited above are actually the same is yet another example of impressive stupidity.

Yep.

 

[gumboot]

Gum:
The high speed comes from (here we go again!) gravity.
The stuff is falling, and the only way it builds up speed is by gravitational acceleration.
So the speeds would be very similar for pyroclastic flow and the clouds of debris , dust and air from the towers, for a similar drop distance.

That's not entirely true. Pyroclastic Flows can also gain velocity from energy released in the eruption, and can attain speeds well in excess of what would be provided by acceleration due to gravity - several hundreds of kilometers an hour. Pyroclastic Surges (which are flows with a higher ratio of gas to solid debris) can travel as fast as 500km/h.

(500km/h would only be achieved after a free fall without resistance for 12,700m - far in excess of the world's highest volcano)

 

[rwguinn]

That's not entirely true. Pyroclastic Flows can also gain velocity from energy released in the eruption, and can attain speeds well in excess of what would be provided by acceleration due to gravity - several hundreds of kilometers an hour. Pyroclastic Surges (which are flows with a higher ratio of gas to solid debris) can travel as fast as 500km/h.

(500km/h would only be achieved after a free fall without resistance for 12,700m - far in excess of the world's highest volcano)

Source, please?
Rocket propelled flows are not making sense to me--but I'm not a fluids guy...

 

[gumboot]

Source, please?
Rocket propelled flows are not making sense to me--but I'm not a fluids guy...

The resulting blast laterally directed the pyroclastic flow of very hot volcanic gases, ash and pumice from new lava, and pulverized old rock hugged the ground while initially moving at 220 mph (350 km/h) but quickly accelerating to 670 mph (1080 km/h) (it may have briefly passed the speed of sound).

1980 eruption of Mount St. Helens

That's just one example of a very high speed pyroclastic flow.

 

[leftysergeant]

Thinking of the historical examples of pyroclastic flows that I know of, the high-speed flows are usually from a volcano which blows out through the side of the cone, such as Krakatoa and Mt St Helens. Rarely is it from the caldera of a volcano with a clear path for the lava.

Perhaps the flow from the towers could be better compared to an avalanche. From what I know of them, from the literature and from having watched a controlled avalanche set off by the WDOT, they seem to me to sometimes take on the character of a turbidity flow, in that the snow becomes disasociated and moves almost like water down the side of a hill. It is a fast-moving powder, usually, but that powder had the force to uproot even old-growth trees.

 

[rwguinn]

That's just one example of a very high speed pyroclastic flow.

Thank you.
I was thinking in terms of the Mexican and Phillipine volcanos, as well as others where there was a vertical eruption. Essentially, like the one the japanese (?) filmakers got caught in. I forgot about St. Helens magnitude of destruction--no way that was gravity driven--but it was a sideways blast.
But even the gravity-driven flows are pyroclastic (by definition), no?

Thinking of the historical examples of pyroclastic flows that I know of, the high-speed flows are usually from a volcano which blows out through the side of the cone, such as Krakatoa and Mt St Helens. Rarely is it from the caldera of a volcano with a clear path for the lava.

Perhaps the flow from the towers could be better compared to an avalanche. From what I know of them, from the literature and from having watched a controlled avalanche set off by the WDOT, they seem to me to sometimes take on the character of a turbidity flow, in that the snow becomes disasociated and moves almost like water down the side of a hill. It is a fast-moving powder, usually, but that powder had the force to uproot even old-growth trees.

That's essentially what I was thinking of. Add extremely hot rocks, ash, and dust, melting any sno/ice cap, and it's pyroclastic...

 

[Beerina]

Actually, he was not the first to make the claim. It was made by seismologists from Lamont-Doherty Earth Observatory. It was in the November 20, 2001 issue of Eos, published by the American Geophysical Union. ScienceDaily comments on the paper,

"The authors also noted that, as seen in television images, the fall of the towers was similar to a pyroclastic flow down a volcano, where hot dust and chunks of material descend at high temperatures. The collapse of the WTC generated such a flow, though without the high temperatures."

Did all these seismologists waste their degree? Should their degrees be revoked as well?

So in other words, thousands of tons of dust and small particles in a limited area can accelerate downward much faster than singleton dust motes can?

Golly, imagine that!


I don't know why this is even an issue.

 

[Hokulele]

Thank you.
I was thinking in terms of the Mexican and Phillipine volcanos, as well as others where there was a vertical eruption. Essentially, like the one the japanese (?) filmakers got caught in. I forgot about St. Helens magnitude of destruction--no way that was gravity driven--but it was a sideways blast.
But even the gravity-driven flows are pyroclastic (by definition), no?

Correct, those are pyroclastic by definition.

 

[leftysergeant]

All pyroclasticflows originate from heat-driven energetic events. Turbidity flows are entirely gravity-driven. The breakup on the dry wall and concrete were entirely gravity-driven. The flow from the towers was a turbidity flow.