The capitvating and deadly pyroclastic flow

February 18, 2009 11:53 AM

An erupting stratovolcano poses numerous hazards for nearby habitation, but none nearly so terrifying and deadly as the pyroclastic flow. Pyroclastic flows, comprised of tons of superheated sulfuric gases, particulate rock materials and ash, can reach temperatures of 1,830 °F and travel at alarming speeds up to 450mph. Convection of materials within the clouds causes them to become a suspension, fluidizing and thundering noxiously across the surrounding landscape for miles, in some cases even uphill or across open water. Wherever these clouds come in contact with humans the result is catastrophe, as the residents of Herculaneum and St. Pierre, Martinique learned within minutes of the eruptions of Vesuvius in 79AD and Pelee in 1902-- both towns were overwhelmed by pyroclastic clouds, igniting all flammable materials and incinerating and suffocating the inhabitants. None survived Herculaneum, while just two of St. Pierre's 26,000 survived, one of whom was a prisoner condemned to death and awaiting his execution in a dungeon cell. Despite their incredible capacity for violence, pyroclastic flows are also capable of producing mesmerizing, awe-inspiring beauty.
posted by baphomet (18 comments total)

I was confused that the geology site doesn't mention Krakatoa, but I guess without pictures it didn't happen. (They do mention it elsewhere.)

How did the tourist in that Japan video not run like mad? Or did Discover (or whoever) stitch more than one video together?

Oh nice, the related videos have 911 conspiracists claiming that "only volcanoes and controlled demolition" exhibit pyroclastic flow.
posted by DU at 12:08 PM on February 18, 2009

Pictures of St Pierre after the eruption of 1902. Extract from "The Last Days of St Pierre".
posted by adamvasco at 12:27 PM on February 18, 2009

just two of St. Pierre's 26,000 survived, one of whom was a prisoner condemned to death and awaiting his execution in a dungeon cell.

Let me guess, his defense attorney asserted that society was to blame, and God agreed.
posted by George_Spiggott at 12:30 PM on February 18, 2009 [1 favorite]

Pyroclastic flows - never want to be near one, but boy are they cool.
posted by Artw at 12:35 PM on February 18, 2009

The GZA was unavailable for comment.
posted by Inspector.Gadget at 12:41 PM on February 18, 2009 [2 favorites]

In January of 1981, National Geographic published a series of photographs taken by Robert Landsburg depicting the first lateral blast of the Mount St. Helens eruption. The photos distinctly showed the asymmetrical bulge immediately preceding the explosion, followed by the explosion itself, and the subsequent pyroclastic flow coming closer, closer, ever closer. Landsburg was killed, suffocated by the toxic cases emitted with the explosion, but not before he secreted his camera in his jacket in an effort to protect the film.

A favorite professor of mine showed an introductory geology class that series of pictures, blown up on a screen 20 feet tall, without letting on about Landsburg's fate. The class began with the oohs and ahs typical of many students who see the dramatic pictures for the first time, but gradually fell silent towards the end of the series as they realized what must have happened.

I wish I could find those photographs online.
posted by monju_bosatsu at 12:47 PM on February 18, 2009 [5 favorites]

Cooool! Pyroclastic flows also create ignimbrite, a nifty type of rock that has been used for millennia by prehistoric folks as toolstone.
posted by elendil71 at 12:54 PM on February 18, 2009

The lava dome at St. Pierre looks like a massive dick. Cool.


(yes, I am twelve.)
posted by notsnot at 1:20 PM on February 18, 2009

Volcanoes, man...they send lava, earthquakes, tephra, mudslides, lightning storms, ash, and smothering blankets of gas to kill you, and if somehow you escape them, they just go ahead and chase you down. They're responsible for mass extinctions!

I am eternally terrified of these things, which means I will probably die in one.
posted by greenland at 1:40 PM on February 18, 2009

I live with a volcanologist who studies pyroclastic flows (among other volcanic processes). He always wins the "so what do you do" contest when we meet new people.
posted by collocation at 1:48 PM on February 18, 2009

Didn't some guy in a titanium canoe once try to ride one? Or did I dream that?
posted by StickyCarpet at 2:52 PM on February 18, 2009 [1 favorite]

Do titanium canoes come with a sidecar for a lion?
posted by Artw at 3:02 PM on February 18, 2009 [3 favorites]

He always wins the "so what do you do" contest when we meet new people.
You think that's bad?
I have a friend who's an astronomer researching rocketry!
=:o
posted by ceedee at 3:06 PM on February 18, 2009

Oh, yeah? I'm Mr. Active Volcano Explorer, himself.
posted by MrMoonPie at 4:02 PM on February 18, 2009

Pyroclastic flows - never want to be near one, but boy are they cool the hot damn!

FTFY.
posted by five fresh fish at 6:09 PM on February 18, 2009

Hot IS cool, man, y'dig?
posted by Artw at 7:16 PM on February 18, 2009

Google books has decided to make all pages of "The Last Days of St. Pierre" unavailable. Here (pdf) is a report in the NYT including eyewitness report from Capt. of the Roddam.
posted by adamvasco at 5:01 AM on February 19, 2009

Also Pliny (78/9 AD) describing eruption of Vesuvius in letters to Tacitus.
posted by adamvasco at 5:06 AM on February 19, 2009