Talk:Pyroclastic flow

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[edit] When/why are flows unlikely to happen?

From the Hekla article, a volcano in Iceland:

Up until now, it has always been assumed that Hekla was incapable of producing that most dangerous of volcanic phenomena, the pyroclastic flow.

Is there a reason scientists would believe this, is it something about the shape of the mountain, kind of material that the mountain can eject, or simply because there was little evidence of previous pyroclastic flows? In the pyroclastic flow article it says that the phenomena happens in "some" eruptions, but doesn't really expound on how/why they can happen, anyone have some more info? --Fxer 18:03, 30 January 2006 (UTC)

[edit] Re: When/why are flows unlikely to happen?

Flows occur due to a high ratio of solid to gas. They are extremley dense and continuous. Hekla's magma may not have the right composition needed to produce flows, the eruptions may be too fluid and instead produce sheets. By the discription given it looks as though Hekla is a fissure volcano which produces extensive lava sheets, there also was a great ash deposit. Ash deposits indicate a pyroclastic air fall, not a pyroclastic flow.

[edit] Unlikely but true?

Can someone supply a reference for the statement Volumes range from a few hundred cubic metres to more than a thousand cubic kilometres. Do we have a first idea how big a 1000 cubic kilometres is? Interestingly, the Dutch article mentions a range van enkele honderden kubieke meters tot enkele kubieke kilometers (from a few hundred cubic metres to a few cubic kilometres.) Who's wrong? --Radioflux 21:31, 23 September 2006 (UTC)

Well, Britannica talks about eruptions of up to 2500 km3 at Yellowstone, so I guess that's okay. I will update the Dutch article. --Radioflux 10:03, 24 September 2006 (UTC)

[edit] Why Is September 11th constantly deleted?

I understand that there were no sources before, even though nothing else on this page has a source. I have included two sources from scholarly publications stating that there were pyroclastic flows in New York on September 11th. Obviously a straight collapse would not generate the heat necessary for pyroclastic flows and serious explosive power would be needed to turn all the concrete into the dust in the pyroclastic flow. Just because you don't like the implications of this fact does not give you the right to delete it from the page. Stop doing it and start acting like a responsible admin. The information is verifiable and it is not original information, so there is no reason not to include it on the page.

BECAUSE THE TRAGIC EVENTS OF 11th September 2001, ARE NOT and NEVER WILL BE A GEOLOGICAL PHENOMENA. So it is precluded from this page. —Preceding unsigned comment added by The Geologist (talk • contribs) 18:00, 1 May 2008 (UTC)


response: i totally agree, wikipedia rules are used in very one sided and biased ways sometimes. Certain rules will be bent & then enforced when people disagree with the point even if they are outside notable sources. I say we leave it in especially because it shows pyroclastic flows happening in an unusual way not normally seen.

Additions to Wikipedia must follow our policies; in other words, information should be verifiable, cited, and properly sourced to ensure the accuracy of the statements. If the additions are indeed verifiable and not original research, then they should be easily sourced, and any information that may be dubious and doesn't comply to these standards should be removed immediately. That being said, thank you finding some sources to the claims; however, I would still like to revisit this article a bit later (when I'm not as tired) to discuss the overall topic and issue of the addition. Thanks! Flcelloguy (A note?) 03:24, 21 October 2006 (UTC)
WTC was brought down by an incendiary bomb, not high explosives as is implied by the article. raptor 09:38, 21 October 2006 (UTC)
Incendiary bombs do not pulverise concrete nor do they create pyroclastic flows
That's right. You need a good published source. Not to mention it would be an opinion push, not a neutral summary. Wikipedia has to be neutral. If it belongs anywhere on this website it would probably be on 9/11 Conspiracy Theories, not on this page, which is about the volcanic phenomenon, not the building collapse phenomenon. Also, similar "flows" are observed in any total and catastrophic collapse of a sufficiently large building with a lot of concrete, explosive or not. Gravity can provide the energy necessary. In explosive demolitions the energy to pulverize the concrete does not come from the charges, it comes from gravity. The explosives just knock out a few columns to get the ball rolling. 74.38.35.171 00:07, 11 January 2007 (UTC)

The World Trade Center was brought down by neither; anything that states or implies that it was is a conspiracy theory and does not belong to this article. Upon furthur examination, the first reference cited is not a reputable source: it seems to be a website dedicated to providing original research and theories on the disasters. I've reworded the paragraph to improve it, and also removed the image, which did not significantly contribute to the article: because of the brief mention of the events, the image is not necessary and takes away from the value of the article as a whole. Thanks! Flcelloguy (A note?) 02:36, 29 October 2006 (UTC)

Looks like we had an edit conflict there, my reversion must have erased your edit, sorry 'bout that. The second ref seems to be just a side note in a discussion of gravity flows. And yes, the 9-11 collapse was a gravity flow, but it doesn't seem to fit the volcanologic usage of the term pyroclastic flow. Thus it seems to be out of place in the article - maybe it would fit as a see also link to gravity flows due to building demolition. Vsmith 02:56, 29 October 2006 (UTC)

We have non-scientists attempting to explain the science behind this event. Pyroclastic flows are one type of gravity flow (actually called gravity currents.). It is not sufficient to say there were gravity currents on 9/11, you need to describe what kind of gravity current. The important thing to note is that every kind of gravity current requires an enormous heat input to mix with the dust and debris in order to form. The buildings collapsing solely due to gravity could not produce the energy needed to pulverise the concrete or to disburse it across such a vast area. The mathematics needed to compute the amount of energy needed and the amount present in the buildings pre-collapse is high school level. Please stop editing this simply due to political or personal considerations, deleting the facts because it is a "conspiracy theory." The fact remains and will always remain despite your objections, that there were pyroclastic flows in Manhattan on 9/11, those flows were not as hot as those of a volcano's but were still quite hot and lifted people as far as 50 feet through the air, and that the towers collapsing due to gravity could not produce enough energy to cause such flows, an additional heat source is required to explain them. I will now delete these unscientific analyses and link to a separate article to deal with the pyroclastic flows on 9/11. In case anyone is interested there is no documented case where pyroclastic flows were present after the gravity collapse of any building in history. —Preceding unsigned comment added by 66.130.250.190 (talk • contribs) 06:27, 1 November 2006

Reverted the conspiracy theory stuff again. Building collapses cause gravity flows. A pyroclastic flow is a gravity flow of incandescent molton rock fragments along with other detritus carried downslope in a volcanic environment. Building collapse, intentional or not, causes gravity flows of dust and debris. The molton rock material is absent. In the event of the collapse of a burning building, there will be hot and some burning materials within the flow. This article is about the natural volcanic phenomenon. The efforts by one editor to push his conspiracy theory views regarding the 9-11 attack into this aticle is totally out of place. Vsmith 00:15, 2 November 2006 (UTC)

No it is not. Obviously these flows did not have pieces of molten rock and were not as hot as pyroclastic flows coming from volcanoes. But they were pyroclastic flows, the key you are missing is the dust, which would be ash and rock in a volcanic pyroclastic flow, but here was pulverized concrete, gypsum, and office furniture. The dust mixes with the hot air you contend can come solely from the jet fuel and weighs down the hot air current which would otherwise rise, and makes it hug the surface of the ground. The dust from the twin towers spread all the way to New Jersey, it blanketed most of Manhattan. Even if the jet fuel and kinetic energy in the towers could explain the spread of the dust cloud, and it doesn't come close, but even if it could, it could not explain the amount of dust produced during the collapse. It wasn't just dust from the ground, it was the contents of both buildings. They were vaporized. Such enormous energy was required to pulverise the entire building. The tops of the buildings are even pulverised. There should have been at least a 20 storey chunk from each building on top of the rubble if the buildings collapsed due to their weight on top of weakened steel from the jet fuel. Even the tops were vaporised. Ground Zero was steel, red-hot steel in fact, but that's another article, no concrete chunks at all from 220 stories of steel and concrete that collapsed there that day. All of it was dust. The amount of energy required to do that is obviously going to generate alot of heat. I don't care if you don't like the implications of it this is scientific fact that these flows were highly unusual for what allegedly happened, and people who study pyroclastic flows scientifically might be interested to know there were some visible during 9/11, though obviously not volcanic still interesting.

An uncontrolled building collapse of that magnitude has rarely been seen before; (never, as far as I am aware) so I don't see how the shear mass couldn't have done that. I'm not saying any conspiracy theories should be mentioned but the actual event maybe. raptor 12:06, 7 November 2006 (UTC)

[edit] Seminal paper published in 1992

Everyone seems to have missed it: Branney and Kokelaar, Pyroclastic density currents and the sedimentation of ignimbrites. Completely new thinking, pretty much abolishes terms like flow and surge. Widely accepted. Main tennet: Deposits only represent the conditions at the flow boundary layer, deposits formed by proggressive aggradation, so terms like fully dilute and granular fluid only apply to the base of the current. Russjass (talk) 09:37, 13 May 2008 (UTC)

[edit] Gravity current?

Pyroclastic flows are not gravity currents. They are the same as turbidity currents. they are driven by the density contrast, they can move on a slope of less than 1 degree —Preceding unsigned comment added by Russjass (talk • contribs) 09:42, 13 May 2008 (UTC)