Got a Real World Weapons or Armour Question? Mk XIII

[AgentPaper]

Well a normal wood fire is still not going to melt rock though, and lava can.

Depends on the type of rock. Some will melt as low as 600-800 C, while others take temperatures of 1000-1200 C. An acetylene torch is definitely hot enough to melt rock, though, and it also won't deal significant damage to wood in half a second.


In any case there are certainly visual evidences of pyrcoclastic flows destroying trees and wooden structures.

Destroying, yes, destroying in seconds, no.

You can keep saying that it will, and I'm going to keep saying that it doesn't, because that goes against every bit of evidence I've seen to date. I've helped my parents burn enough branches, logs, and entire trees over the years to know that wood doesn't burn quickly, no matter what you do. Unless you can provide direct evidence to the contrary, there's really not much to discuss beyond that.

Edit: Also, looks like we need to bring this to a new thread.

[AMFV]

Bringing this back to the original question - even if the hypothetic breath hit temperatures of pyroclastic flows, it wouldn't have a similar effect. We're comparing the rate of heat exchange to wood from an extremely viscous liquid and a hot gas - probably a low density hot gas at that. The gas is thus going to need to be far hotter to burn wood anywhere near as quickly.

Pyroclastic flows are a large part gas actually. The most destructive volcanic forces are extremely high viscosity.


Depends on the type of rock. Some will melt as low as 600-800 C, while others take temperatures of 1000-1200 C. An acetylene torch is definitely hot enough to melt rock, though, and it also won't deal significant damage to wood in half a second.



Destroying, yes, destroying in seconds, no.

You can keep saying that it will, and I'm going to keep saying that it doesn't, because that goes against every bit of evidence I've seen to date. I've helped my parents burn enough branches, logs, and entire trees over the years to know that wood doesn't burn quickly, no matter what you do. Unless you can provide direct evidence to the contrary, there's really not much to discuss beyond that.

Edit: Also, looks like we need to bring this to a new thread.


Most of the destruction of pyroclastic flows happens in seconds.

[Thiel]

50 pages, so it's time for a new thread.
LINK (http://www.giantitp.com/forums/showthread.php?p=16880577)

[Stephen_E]

Pyroclastic flows are a large part gas actually. The most destructive volcanic forces are extremely high viscosity.




Most of the destruction of pyroclastic flows happens in seconds.

Yes, but it's knockdown damage.
The blast wave does the damage followed by the heat. The heat takes time.
Keep in mind that you can walk on the thicker lava if you have the right boots and move reasonably quickly.

[AMFV]

Yes, but it's knockdown damage.
The blast wave does the damage followed by the heat. The heat takes time.
Keep in mind that you can walk on the thicker lava if you have the right boots and move reasonably quickly.

You're not walking on the lava, you're walking on the crust it forms, that's just rock. It'll still melt your shoes, and you certainly can't walk on liquid lava. I've kicked lava before, and actually caught my shoe on fire, it wasn't terrible, but that was after it had been cooling and cut off from the source for about an hour.

And it's the heat that welds rocks, that's pretty intense. Pyroclastic flows are mostly damaging because of the combination of volatiles and heat.

[SowZ]

You're not walking on the lava, you're walking on the crust it forms, that's just rock. It'll still melt your shoes, and you certainly can't walk on liquid lava. I've kicked lava before, and actually caught my shoe on fire, it wasn't terrible, but that was after it had been cooling and cut off from the source for about an hour.

And it's the heat that welds rocks, that's pretty intense. Pyroclastic flows are mostly damaging because of the combination of volatiles and heat.
It bears restating that people have fallen into lava and even been sunk to their knees in it and got out with no life lasting injuries other than scars. If lava doesn't disintegrate human legs in seconds, I'd have trouble believing it could do it to any reasonably thick, living tree.

[No brains]

It bears restating that people have fallen into lava and even been sunk to their knees in it and got out with no life lasting injuries other than scars. If lava doesn't disintegrate human legs in seconds, I'd have trouble believing it could do it to any reasonably thick, living tree.

Do you have a source for this? I don't really doubt what you say, but it sounds metal enough for me to see myself!

[SowZ]

Do you have a source for this? I don't really doubt what you say, but it sounds metal enough for me to see myself!

Yeah. I had to source it in one of the previous iterations of this thread where it came up. I'll find it when I get home.

[Mr. Mask]

It depends on how fresh the lava is. Cooled down lava is nothing like fresh lava.

[AMFV]

It bears restating that people have fallen into lava and even been sunk to their knees in it and got out with no life lasting injuries other than scars. If lava doesn't disintegrate human legs in seconds, I'd have trouble believing it could do it to any reasonably thick, living tree.

We were talking about pyroclastic flows, and there's no case where a human has survived that that I'm aware of. Pyroclastic flows are a much closer analog to dragon breath being gaseous and ashy over liquid. Also again it really depends on the freshness of the lava as was pointed out. I've kicked lava and have physically been around it, and I could not have kicked fresh lava.

I've never claimed that lava could flash burn a tree, but a pyroclastic flow sure as hell can.

[Raum]

It's worth noting you won't sink in lava. It's more than three times as dense as water and far more viscous. Since the human body is barely more dense than water, you're not going to sink. You'll just burn on top.

[AMFV]

It's worth noting you won't sink in lava. It's more than three times as dense as water and far more viscous. Since the human body is barely more dense than water, you're not going to sink. You'll just burn on top.

That also really depends on your variety of lava, some of it is about as dense as molasses, others are much less dense. What you're talking about as far as I can tell is a more Rhyolotic lava, which is incredibly dense, but basaltic lavas are less so and you could probably sink somewhat into them, although it's unlikely.

[Stephen_E]

Yes, lava varies a considerable amount and the less dense onse you can ideed sink into. Remember that a standing person is putting a considerable amount of weight on a small surface area. Of course if they were lying down they wouldn't, but that would be a fairly unpleasant way to commit suicide. Lava is a viscous material. Think wet peat/mud rather than water.

Re: Pyroclastic flows. With all respect TTBOMK we don't have data on how long it takes to actually kill a person because been a blast/flow everything in the area is knocked down/buried or outrunning it. There's no in-between. If you get caught any observers are looking at the remains after everything has cooled. Whether you cooked/suffercated/Heart Attack/Stroke/blast truama 1st is basically unknowable because you will carbonize after you die even if the burning didn't kill you 1st.

I'm reminded of an interview of a family that survived St Helen's. They were on the road when the eruption occurred and the driver hit the accelerator and drove for everything he was worth. He passed another car doing 106 mph. He made it out of the blast zone where all the tree's were knocked down before the wave caught them, the other car didn't.

[SowZ]

We were talking about pyroclastic flows, and there's no case where a human has survived that that I'm aware of. Pyroclastic flows are a much closer analog to dragon breath being gaseous and ashy over liquid. Also again it really depends on the freshness of the lava as was pointed out. I've kicked lava and have physically been around it, and I could not have kicked fresh lava.

I've never claimed that lava could flash burn a tree, but a pyroclastic flow sure as hell can.

Hmm, yeah, I wouldn't know about that.

As for the man who went over his knees, he went into a hole not realizing it was adjacent to underground laval flow. The wall caved in and filled the hole.

[AMFV]

Yes, lava varies a considerable amount and the less dense onse you can ideed sink into. Remember that a standing person is putting a considerable amount of weight on a small surface area. Of course if they were lying down they wouldn't, but that would be a fairly unpleasant way to commit suicide. Lava is a viscous material. Think wet peat/mud rather than water.

Re: Pyroclastic flows. With all respect TTBOMK we don't have data on how long it takes to actually kill a person because been a blast/flow everything in the area is knocked down/buried or outrunning it. There's no in-between. If you get caught any observers are looking at the remains after everything has cooled. Whether you cooked/suffercated/Heart Attack/Stroke/blast truama 1st is basically unknowable because you will carbonize after you die even if the burning didn't kill you 1st.

I'm reminded of an interview of a family that survived St Helen's. They were on the road when the eruption occurred and the driver hit the accelerator and drove for everything he was worth. He passed another car doing 106 mph. He made it out of the blast zone where all the tree's were knocked down before the wave caught them, the other car didn't.

There is no outrunning a pryroclastic flow. Period. 106 is not enough to escape a pyroclastic flow, it's possible that he outran something else. But what he outran was not the pyroclastic flow. PDCs are hot enough to weld rock, and they're only around for a short while before they start to cool. Now he may have outrun the shockwave from the eruption (certainly possible), but it is extremely unlikely that he outran the PDCs which are a completely different thing.


Hmm, yeah, I wouldn't know about that.

As for the man who went over his knees, he went into a hole not realizing it was adjacent to underground laval flow. The wall caved in and filled the hole.


I'm sorry, I'm calling shenanigans on this story. I've studied Volcanology, there is no way that he would have been inside lava without receiving severe burns. Now I've heard a story of somebody that had their boots inside lava when they were walking and collapsed into a lava tube, and they lost their boots and had severe injures, but were certainly not "buried up to the knees" and they did have severe injuries.

[AgentPaper]

There is no outrunning a pryroclastic flow. Period. 106 is not enough to escape a pyroclastic flow, it's possible that he outran something else. But what he outran was not the pyroclastic flow. PDCs are hot enough to weld rock, and they're only around for a short while before they start to cool. Now he may have outrun the shockwave from the eruption (certainly possible), but it is extremely unlikely that he outran the PDCs which are a completely different thing.

You can certainly outrun it if you have a 100+ mile head start.

[AMFV]

You can certainly outrun it if you have a 100+ mile head start.

That's not really outrunning it... That's more being in the same place and getting away. The problem is that people are confusing different parts of the volcanic eruption, which even I was guilty of at the first (serves me right for posting pre-caffeine), the thing that they outran is probably a blast wave, which you could maybe outrun, I'm not actually sure how fast those move. PDCs are pyroclastic density currents, those can move at speeds of up to 600 MPH, and generally move around 200-300 MPH even in rough terrain. That's certainly beyond any capacity for outrunning if you don't have a tremendous headstart. If you are close to it, then there is no outrunning it. And if he was close enough to see the trees get knocked down (by the PDC) then he was too close to outrun it. I suspect that it was the blast wave he 'outran' not a PDC.

[Stephen_E]

There is no outrunning a pryroclastic flow. Period. 106 is not enough to escape a pyroclastic flow, it's possible that he outran something else. But what he outran was not the pyroclastic flow. PDCs are hot enough to weld rock, and they're only around for a short while before they start to cool. Now he may have outrun the shockwave from the eruption (certainly possible), but it is extremely unlikely that he outran the PDCs which are a completely different thing.


PDC otherwise known as Pyroclastic Density Current otherwise know as a Pyroclastic Flow?

Pyroclastic Flows slow down. Quite simply if you are have enough headstart you can outrun a pyroclastic flow as it slows down and runs out of omph before it overuns you. Which does pretty much cover the definition of "outrun". Sure they may start at speeds of 700 kmph, but they don't continue at that speed. Admittedly I haven't studied vocalonolgy as such. Spent over 20 years working in seismology sharing general office space with vocanologists and assisting them sometimes (I was a Technician). Helped Proofread a book on Earthquakes and vocanology co-written by Volcanologist Dr John H. Latter, but I only picked up bits and pieces that interested me at the time.

According to Wiki the Gas in Pyroclastic flow's reach 1000 celsius. It does make water boil as it passes over it but the example of St Helens can be taken as an excellent case that it doesn't spontaenopusly burn significant quantities of wood to ash. The Pyroclastic flow knocked vast quantities of trees over but the trees and many of the branches still existed after the PDC had passed. Throughly charred but not ash. And that was after lying in the hot ash and rock until it cooled.

http://en.wikipedia.org/wiki/Pyroclastic_flow

[AMFV]

PDC otherwise known as Pyroclastic Density Current otherwise know as a Pyroclastic Flow?

Pyroclastic Flows slow down. Quite simply if you are have enough headstart you can outrun a pyroclastic flow as it slows down and runs out of omph before it overuns you. Which does pretty much cover the definition of "outrun". Sure they may start at speeds of 700 kmph, but they don't continue at that speed. Admittedly I haven't studied vocalonolgy as such. Spent over 20 years working in seismology sharing general office space with vocanologists and assisting them sometimes (I was a Technician). Helped Proofread a book on Earthquakes and vocanology co-written by Volcanologist Dr John H. Latter, but I only picked up bits and pieces that interested me at the time.

According to Wiki the Gas in Pyroclastic flow's reach 1000 celsius. It does make water boil as it passes over it but the example of St Helens can be taken as an excellent case that it doesn't spontaenopusly burn significant quantities of wood to ash. The Pyroclastic flow knocked vast quantities of trees over but the trees and many of the branches still existed after the PDC had passed. Throughly charred but not ash. And that was after lying in the hot ash and rock until it cooled.

http://en.wikipedia.org/wiki/Pyroclastic_flow

There certainly are pyroclastic flows that have turned trees to ash though, at least as far as I've been able to tell. There is some variety in the flows. Generally you're not going to outrun them, even when they slow down, the best course of action is to get to higher ground if you can, and usually if you can see it's already too late.

I wouldn't call outrunning something with several miles of headstart, outrunning really. Which is what you'd need, even when they slow down to their average speed of around 2-300 MPH you're still not outrunning them, not by a long shot.

[Stephen_E]

There certainly are pyroclastic flows that have turned trees to ash though, at least as far as I've been able to tell. There is some variety in the flows. Generally you're not going to outrun them, even when they slow down, the best course of action is to get to higher ground if you can, and usually if you can see it's already too late.

I wouldn't call outrunning something with several miles of headstart, outrunning really. Which is what you'd need, even when they slow down to their average speed of around 2-300 MPH you're still not outrunning them, not by a long shot.

Hmm, this may be in part different definitions of "out run".
That said Pyroclastic flows start of with "x" velocity (speed and direction) and then flow in a mathmatical path as determined by gravity and the terrain. With their velocity eventually dropping to zero. So basically the Pyroclastic flow is going to cover "Area A", where "Area A" is all the terrain that the Pyroclasitic flow will transverse before it's velocity decreases to 0.
If at the time of the Pyroclastic eruption occurs and the flow starts (St Helens started as a Pyroclastic Jet which then rapidly chaged into a Flow) you are at point "y" and point "y" is within "Area A" then I would consider you to be in a race to reach a point outside "Area A" before the flow reaches you (well technically close to the edge would probably do). I woulod describe that as a "race" but nonetheless if you don't at least you understand what I mean. And respectively if you are on the road driving when the blast occurs and you have a 10-20 miles edge on the blast then provided the road direction favoured you it's quite reasonable that if you are traveling at 170km/h you could get outside "Area A" before the PDC caught you. At an average velocity you might be doing 1 mile to every 2 it does, and the PDC is constantly slowing, so every miles it's rate of catching you is slower.

In general though Volcanoes do rack up the weirdest survival stories. They are very random in their killings. If you read the St Helen's survival stories that brings it home. And the Dr Latter was on the edge of the crater lake of one of our central volcanoes (New Zealand) as part of two observation teams when it erupted. Two were on either side. With boulders landing all around they wrote of the other team and moved from their location to a more sheltered place about 10 metres away. When the eruption finished there was a boulder the size of a small car where they had been initially camped. As it turned out the other team had also been lucky enough to survive unscathed (note: Volcanologists have the highest casualty rate of any group of scientists and are generally consider by other scientists to be at least moderately insane. And this is from people who consider it sane to pull large explosives out of the sea that failed to detonate when triggered and fix them before lowering it back down, rather than abandon that part of the experiment!!!

[AMFV]

Hmm, this may be in part different definitions of "out run".
That said Pyroclastic flows start of with "x" velocity (speed and direction) and then flow in a mathmatical path as determined by gravity and the terrain. With their velocity eventually dropping to zero. So basically the Pyroclastic flow is going to cover "Area A", where "Area A" is all the terrain that the Pyroclasitic flow will transverse before it's velocity decreases to 0.
If at the time of the Pyroclastic eruption occurs and the flow starts (St Helens started as a Pyroclastic Jet which then rapidly chaged into a Flow) you are at point "y" and point "y" is within "Area A" then I would consider you to be in a race to reach a point outside "Area A" before the flow reaches you (well technically close to the edge would probably do). I woulod describe that as a "race" but nonetheless if you don't at least you understand what I mean. And respectively if you are on the road driving when the blast occurs and you have a 10-20 miles edge on the blast then provided the road direction favoured you it's quite reasonable that if you are traveling at 170km/h you could get outside "Area A" before the PDC caught you. At an average velocity you might be doing 1 mile to every 2 it does, and the PDC is constantly slowing, so every miles it's rate of catching you is slower.


Well if you consider that outrunning then we are in agreement. I wouldn't consider it, outrunning.

[SowZ]

There is no outrunning a pryroclastic flow. Period. 106 is not enough to escape a pyroclastic flow, it's possible that he outran something else. But what he outran was not the pyroclastic flow. PDCs are hot enough to weld rock, and they're only around for a short while before they start to cool. Now he may have outrun the shockwave from the eruption (certainly possible), but it is extremely unlikely that he outran the PDCs which are a completely different thing.




I'm sorry, I'm calling shenanigans on this story. I've studied Volcanology, there is no way that he would have been inside lava without receiving severe burns. Now I've heard a story of somebody that had their boots inside lava when they were walking and collapsed into a lava tube, and they lost their boots and had severe injures, but were certainly not "buried up to the knees" and they did have severe injuries.

I didn't say no severe injuries. He certainly didn't walk away from it and if I remember right he was hospitalized for quite a while. I believe I said no life lasting injuries.