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What is a Supervolcano?

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In Yellowstone, the rim of a supervolcano caldera is visible in the distance. Photo courtesy of the National Park Service.

In 2012, director Roland Emmerich’s love letter to the Mayan apocalypse (oh hey, wasn't that supposed to happen today?), our heroes barely manage to escape Yellowstone National Park before it explodes beneath them. This not-so-subtle sci-fi sequence is actually based on something real: Underneath Yellowstone is a supervolcano. What distinguishes this kind of volcano from regular volcanoes, and what will happen if—or when—it erupts?

Regular versus Super Volcano

There are several types of volcanoes: Cinder, composite or stratovolcanoes, shield volcanoes, and lava domes, which all rise above the earth. But supervolcanoes like the one under Yellowstone are calderas, vast sunken areas formed when the volcano expels all of its magma, and the land comes back to rest in the empty chamber. These calderas can be as big as 60 miles across (the current Yellowstone caldera, which sits on several older calderas, measures about 28 miles by 47 miles).


Click to enlarge.

When Mount St. Helens, a stratovolcano located in Washington, erupted in 1980, the event rated a 5 on the Volcanic Explosivity Index (VEI) and expelled one cubic kilometer of ash. But supervolcanoes register 8 on the VEI and typically expel ten thousand times the quantity of magma and ash expelled during the Mount St. Helens eruption. The last Yellowstone eruption, which occurred 640,000 years ago, "spewed out nearly 240 cubic miles of debris," according to the USGS.

The Yellowstone is just one of a few supervolcanoes scattered around the globe. An incomplete list includes Taupo in New Zealand, which was the most recent to erupt, about 26,000 years ago. Before that was a supereruption of Lake Toba on Sumatra, Indonesia, which occurred 69,000 to 77,000 years ago. There's a supervolcano under Pompeii, and one in Chile, too. There may be more we haven't yet discovered.

What Happens If A Supervolcano Erupts?

Below Yellowstone's surface—in some places as little as 5 or 6 miles—is a reservoir of solid rock and magma. Below that is a 45-mile-wide plume of molten rock that comes from at least 410 miles beneath the Earth surface (this is what fuels Yellowstone's incredible geysers and geothermal pools). Bob Smith, who first described Yellowstone as "a living, breathing caldera" in 1979, says in his book, Windows into the Earth, that if the caldera were to erupt, "Devastation would be complete and incomprehensible."

First there would be swarms of earthquakes, then a huge blast that would wipe Yellowstone off the map. Clouds of ash and gas would burn everything in their paths. Ash would cover most of North America, destroying food sources. Some speculate that a supereruption from the Yellowstone caldera would instantly kill 87,000 people. Others speculate that such an eruption would lower the temperature of the Earth by at least 21 degrees, and might even block out the sun.

Recently, a study determined that if or when Yellowstone next erupts, it will probably be centered in one of three parallel fault zones running north-northwest across the park.

Still, there's probably not a reason to worry. Chances are, a supereruption won't occur in our lifetimes. Number crunchers have determined that only 1.4 supereruptions occur every million years, and, according to the USGS, the chances of Yellowstone erupting are slim: just 1 in 730,000, or 0.00014 percent, a year. Sorry, conspiracy theorists. Maybe at the end of the next b'ak'tun.

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science
Why a Howling Wind Sounds So Spooky, According to Science
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Halloween is swiftly approaching, meaning you'll likely soon hear creepy soundtracks—replete with screams, clanking chains, and howling winds—blaring from haunted houses and home displays. While the sound of human suffering is frightful for obvious reasons, what is it, exactly, about a brisk fall gust that sends shivers up our spines? In horror movie scenes and ghost stories, these spooky gales are always presented as blowing through dead trees. Do bare branches actually make the natural wailing noises louder, or is this detail added simply for atmospheric purposes?

As the SciShow's Hank Green explains in the video below, wind howls because it curves around obstacles like trees or buildings. When fast-moving air goes around, say, a tree, it splits up as it whips past, before coming back together on the other side. Due to factors such as natural randomness, air speed, and the tree's surface, one side's wind is going to be slightly stronger when the two currents rejoin, pushing the other side's gust out of the way. The two continue to interact back-and-forth in what could be likened to an invisible wrestling match, as high-pressure airwaves and whirlpools mix together and vibrate the air. If the wind is fast enough, this phenomenon will produce the eerie noise we've all come to recognize in horror films.

Leafy trees "will absorb some of the vibrations in the air and dull the sound, but without leaves—like if it's the middle of the winter or the entire forest is dead—the howling will travel a lot farther," Green explains. That's why a dead forest on a windy night sounds so much like the undead.

Learn more by watching SciShow's video below.

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Space
SpaceX's Landing Blooper Reel Shows That Even Rocket Scientists Make Mistakes
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SpaceX's Falcon 9 rocket launches.
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On March 30, 2017, SpaceX did something no space program had done before: They relaunched an orbital class rocket from Earth that had successfully achieved lift-off just a year earlier. It wasn't the first time Elon Musk's company broke new ground: In December 2015, it nailed the landing on a reusable rocket—the first time that had been done—and five months later landed a rocket on a droneship in the middle of the ocean, which was also unprecedented. These feats marked significant moments in the history of space travel, but they were just a few of the steps in the long, messy journey to achieve them. In SpaceX's new blooper reel, spotted by Ars Technica, you can see just some of the many failures the company has had along the way.

The video demonstrates that failure is an important part of the scientific process. Of course when the science you're working in deals with launching and landing rockets, failure can be a lot more dramatic than it is in a lab. SpaceX has filmed their rockets blowing up in the air, disintegrating in the ocean, and smashing against landing pads, often because of something small like a radar glitch or lack of propellant.

While explosions—or "rapid unscheduled disassemblies," as the video calls them—are never ideal, some are preferable to others. The Falcon 9 explosion that shook buildings for miles last year, for instance, ended up destroying the $200 million Facebook satellite onboard. But even costly hiccups such as that one are important to future successes. As Musk once said, "If things are not failing, you are not innovating enough."

You can watch the fiery compilation below.

[h/t Ars Technica]

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