Disasters

Pyroclastic Flow Is the Deadliest Volcanic Hazard You've Never Heard Of

There have been a lot of volcanoes in the news lately, from the sudden eruption in Hawaii to the deadly events in Guatemala that kicked off this June. Plus, there's a pretty big one in that Jurassic World trailer. But one thing all these geological upheavals have in common is that their worst, most dangerous parts came long before the lava flowed down the mountainside.

Check the Pyroclastic Flow

Here's the thing: Magma isn't the only thing waiting to erupt when a mountain blows its top to become a volcano. There's plenty of burning-hot gas down there as well. And in case you didn't notice, mountains are made of solid rock — all that rock doesn't just disappear when the pressure builds up to an explosion. In other words, a volcanic eruption also sends a wall of searing gas and enormous, broken boulders tumbling in all directions. This is the pyroclastic flow, and it's a lot more dangerous than the glowing-red lava.

Although it makes sense to think that the lava is the worst part, the pyroclastic flow has several elements that make it more dangerous than its liquid counterpart. For one thing, it's a lot faster. This giant wall of ash, gas, and boulders as hot as 1,300 degrees Fahrenheit (700 degrees Celsius) usually comes at you faster than 55 miles per hour (89 kilometers per hour). Second of all, that searing-hot gas is generally a combination of stuff like sulfur dioxide, hydrochloric acid, and carbon monoxide, which aren't just deadly to breathe, but corrosive to boot. Finally, in case we need to re-emphasize it, that cloud of super-hot poison gas is also hiding a super-hot landslide. If you've ever seen the desolate waste left over after a major eruption, you can chalk that destruction up to the all-flattening power of a mile-a-minute, poison-gaseous, nearly-hot-enough-to-burn-diamonds landslide.

Guatemala's Deadly Pyroclastic Flow

The Man Who Survived Doomsday

The deadliest eruption of the 20th century happened on May 8, 1902, when Martinique's Mount Pelée destroyed Saint Pierre, known as the "Paris of the Caribbean." The city's 30,000 residents were almost immediately killed as a wave of incandescent gas washed over them at nearly 100 miles per hour (161 kilometers per hour). The pyroclastic flow killed virtually all of the unfortunate citizens all at once — but one man was able to survive thanks to his drunken misconduct the day before.

Actually, there's some disagreement about the crime that Ludger Sylbaris committed, but one thing is for sure: whatever it was that landed him in prison saved his life. It was probably a pretty minor offense, but the police were irritated enough with his antics to toss him into solitary confinement in a tiny cell with thick, impenetrable walls. You probably see where this is going. The eruption took place the day after Sylbaris was tossed in jail, and while he was badly burned, he managed to survive. And after that, his rocky life began looking up.

Billed as "The Man Who Lived Through Doomsday," Sylbaris began touring the United States with Barnum & Bailey's circus. Meanwhile, the town was not so lucky. It never did recover, and today its population is only a few thousand. It's just further proof that lava might be no fun, but a bad pyroclastic flow can forever change a place in a matter of moments.

Of course, you don't need to put your life and livelihood at risk to spot a volcanic eruption. You can just make one in your own house. This classic experiment is a great way to get kids excited about science. If you choose to make a purchase through that link, Curiosity will get a share of the sale.

Written by Reuben Westmaas June 22, 2018

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