Pyroclastic flows: The secret of their deadly speed

When a volcano erupts, pyroclastic flows are often the biggest danger to anyone nearby. These fast-flowing currents of rock, ash and extremely hot gas are extremely difficult to study, so researchers in New Zealand created their own. By closely studying pyroclastic flows in their specially-made lab, they identified a very thin layer of gas that helps explain how this volcanic phenomenon moves so fast and can travel so far.

8th April 2019

[arrowed_sparrow]

That makes so much sense. A man saw a pyroclastic blast barreling towards him when he was in the woods. He very quickly found a shallow area and laid there until it passed, and lived to talk about it. It now makes sense how he wasn't killed by debris.

[ragnapodewski]

Rittmann has 60 years ago a clear description of the mechanism of pyroclastic flows made:In a gas rich and tough magma with falling pressure the gas bubbles grow til they are confluenting, their walls break to glass splinters an a most movable emulsion of hot fragments in hot gas escapes with high speed.

[AnnedakDragon]

Dante's Peak is the most accurate volcano film, change my mind.

[antonrupert]

Would be interesting to see if one could do something to disrupt the boundary layer and slow/stop the flow earlier. Don't know much about fluid dynamics, but I think boundary layer adhesion is pretty well understood?

[sfd]

Great video. Short and to the point. A+

[RobertMorgan]

Also makes sense when you consider all of the gases in a pyroclastic flow were both under pressure and extremely heated when released, and now in atmosphere those gasses are doing what superheated, pressurized gasses do in any EXPLOSION, rapidly expanding in volume as they move. The gasses are not only rolling downhill from gravity due to being denser than air, but they're also rapidly expanding at the same time and accelerating anything along for the ride.

[ratandmonkey]

You'd think that scientist operating his lab pyroclastic flow might want to put on a dust mask ...

[nikluz]

Creates a pyroclastic flow 10 feet away.

👀 Wears a t shirt

[FishOniDeviantArt]

It's so cool how it moves like water.

[glennbengtson]

I have seen this phenomena my self first hand, and i can tell, its all but fun.
With that being said, it was not from a volcano, but rather a at a power plant, dealing with fly ashes.
When disposal of fly ashes, under right circumstances, ash will behave just as described, as a fluid, and its fast, super fast, there is no time to react, if it wasn't because we had the right protecting gear, i wouldn't be writing this-
And that was "cold" fly ash, pyroclastic flows is super hot at the same time as its insanely fast.

[JeffreyBarkdull]

I wonder if this so-called volcano in the lab could be good for those who want to make a disaster film based around a volcanic eruption?

[ppm]

Amazing video. Great research. Letting the flow out the front door was the funniest bit... at least until I saw the research was published by Lube et al.

[muhammadikhwannurrosyidin]

This explanation is very important for Indonesia because many volcanic eruptions here often cause pyroclastic flows

[Minmin]

St Vincent and the Grenadines La Soufriere is still erupting at the moment, my homeland is filled with plume ash.🇻🇨

[barnarus]

The phenomenon happens with very fine, very dry soil on a slope and in a snow avalanche. Moving gases within keep it fluid, like water does in quicksand.

[SteinErikDahle]

That bottom layer might be some kind of Leidenfrost-effect?

[malcovichoverlord]

I deadass finally know how this works yess thank you!😘😘😘♥️♥️♥️ learning a new way volcanoes can kill and be deadley I more exciting than I thought

[Yichard]

Wow, remarkable. Solves a lot of mysteries.
I am still having a question: what about COLD landslides? They can too travel very fast. Perhaps it is friction which creates a layer of hot gasses?

[KasperiVonSchrowe]

I'm sorry but I think you got it wrong. You know, lavine avalanches are also notoriously fast and long carrying and not having hot gases to carry the avalanche. But instead, during avalanche studies they discovered that the material is flowing fast in the middle of the avalache cloud. The outer layers of the cloud suffer from air resistance moving slower. That generates a "rolling motion" of material in which in the center of the cloud there is no air resistance at all. The front tip of the avalanche is moving fast but in the moment it is in open air, the particles move in the outer layer of cloud allowing new fast particles to emerge. Like bicycle racers drafting and changing leader continuously in peloton.

[melodyj]

Anyone here after that Rings of Power episode? A ton of comments were talking about pyroclastic flow and I admit I had no idea what that was until now lol