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Hank Green: Hey, good news! I live right down the road from one of the largest volcanoes in the Earth's history.

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So, here in Montana it's beautiful. We have a ton of breweries and chai shops and lovely parks to take my dog to, which is why I sort of have a hard time imagining it being completely destroyed and covered in six feet burning hot ash and pumice. You know me. I live for danger.

Fact is, just 250 miles from me lies one of the Earth's largest volcanoes, which you probably know as Yellowstone National Park, and it is still active, though it's not one of those cool mountainous oozy volcanoes that Hawaii gets. The Yellowstone volcano is one of a half dozen or so tantrumy mountains that earn the title "supervolcano", because its eruptions can eject nearly 250 cubic miles of ash, dust, and gas. For comparison, that's about a thousand times the volume of Mt. St. Helens' eruption in 1980, which was in itself a pretty big deal, but you shouldn't be surprised; Yellowstone is famous for its hydrothermal features like geysers and hotpots and fumaroles, which are all products of this volcanic hotspot, where half-melted magma swells up close to the Earth's crust.

The problem is when Yellowstone goes all Christian Bale on us.

Parody of Christian Bale: Oh, good for you! Yeah, you know, you see it walking around, dit da dit da da, going through your fumaroles.... Yeah, I'm gonna kick your f****** ass!

Hank Green: Which it has done three times in its history.

Those eruptions were so huge that you can actually still see their effects from space. This ring that surrounds Yellowstone National Park is a crater, or caldera, that was caused by a series of eruptions that happened 2.1 million years ago, and we can still see them. The first of them was the largest, which left a divot in the ground the size of Rhode Island, and deposited ash so far away that the rock formed from that ash, called tuff, can still be found from Los Angeles to Saint Louis.

The second happened 1.3 million years ago, and was the smallest of the three. Still managed to leave a 23 mile wide crater in eastern Idaho. And the most recent, about 640,000 years ago, was less than half as big as the first, but still equaled about 2,500 Mt. St. Helens, covering hundreds of miles of western North America in a foot of ash.

Now, to give you a sense of how mind-blowingly huge these events were, here's how the Yellowstone's greatest hits compare to some other gigantic eruptions. I can't believe I live in the same area code as that thing.

Now, there were no people around when Yellowstone last erupted, but history has shown us what some of its colleagues have done, and it's not pretty. The most recent supervolcano eruption happened around 75,000 years ago when Mt. Toba blew its lid in what is now Indonesia. Toba spewed what is probably around 720 cubic miles of stuff into the atmosphere, sent sulfuric acid rain falling as far as Greenland, and six inches of ash fell in India. And scientists think that all of this debris spewed into the upper atmosphere and actually caused a miniature ice age, which we can see in geological records. Ice core samples show that the Toba eruption was followed by a global decrease in temperature of five to nine degrees that lasted hundreds of years. Maybe that was just a coincidence? We can hope?

So I know you're wondering whether or not you should cancel your plans to come visit Montana. First of all, no -- you could totally crash on my couch. Secondly, the geologists at the Yellowstone volcano observatory (which is a thing that I am glad we have) say that if they could predict the eruption of this massive supervolcano, which they can't, it wouldn't be overdue for another 100,000 years or so.

So there's that, at least, and I hope that you come to visit Yellowstone soon, because it's pretty freakin' cool place, even if it is one day going to kill us all.

Thank you, as always, for watching. If you would like to ask us questions or suggest topics for us here at SciShow, please suggest them on Facebook or Twitter or in the YouTube comments below, and don't forget to subscribe, because we're making you smarter.

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