The funny thing about life is, trouble never comes from where you expect it. You spend two months worried about interviewing for that big job promotion, then on your way there, you get attacked by a pack of wild dogs. That's just the way it goes.
So in terms of worldwide disasters, while Hollywood obsesses over asteroid strikes and earthquakes and whatever the fuck 2012 was about, don't be surprised if disaster comes in the form of one of these lesser-known calamities that you'd never even heard of.
Until today, that is.
Volcanoes are badass, there is no denying that. People worship the things as gods. They can create damned land masses. And sure, Mt. Pinatubo and Krakatoa may have messed some shit up when they went off, but that's really just a problem for the people who made the rather short-sighted decision to live at the base of one.
Whatever, mountain god. We live over here.
But what if you had a really, really big volcano. A super volcano, if you will. One big enough to fuck up the whole planet.
Supervolcanoes exist, and they are to volcanoes what nuclear weapons are to firecrackers. According to Wikipedia, a supervolcano can puke out more than 240-cubic-miles of matter into the sky, which is millions of times larger than a normal eruption.
Imagine tossing all of Connecticut into the atmosphere.
They are caused by massive amounts of magma building up pressure under the crust, and not enough holes (volcanoes, geysers, etc,) to vent it all. Eventually, the pressure builds until a massive section of earth explodes. The human race was possibly shaped by one such explosion--it wreaked such havoc on the ecosystem that when it was done, there were only enough humans left on the planet to fill one high school gymnasium.
So Are We Doomed?
Maybe. There is no evidence that any of these are going to explode in our lifetime- oh wait. Long Valley in California has been showing signs of "waking up" in the past 20 years.
Foul play hasn't been ruled out.
Then there are the Siberian traps in Russia, which are quiet for now. This is very good news because it is estimated that if they blew up, they would likely cause another event like the one back at the Permian Triassic boundary 251-million-years ago... which virtually wiped out all life on Earth.
You know how every once in a while you hear a story about some dumbass who fires his gun into the air like Yosemite Sam, only to have the bullet fall back to Earth and kill some bystander a few seconds later?
Imagine if the Earth did that, only instead of a bullet, it's a hunk of rock big enough to kill millions of us. That's a verneshot.
Also called God's Money Shot.
It all starts the same as your mega-volcano up there, when incredibly hot rock starts welling up under the Earth's crust. Only this time, the heat creates a massive buildup of carbon dioxide gas underground. It builds and builds and builds until it erupts with such incredible force that it launches gigantic rocks into fucking space.
Well, not all the way into space. If that's all it did, it wouldn't be such a problem (and in fact we'd probably just sell tickets to that shit--though you'd have to be far enough away to avoid the shockwave and molten rock spraying everywhere). No, the problem is the rock doesn't quite wind up leaving the atmosphere or settling into orbit. So your real troubles start when it comes back down.
So Are We Doomed?
We don't know for sure that this has ever happened, but if it did, it would basically combine all of the horror of a supervolcano with a massive asteroid strike.
The whole theory came about because when looking back over some extinction-level events of the past, you seem to have both signs of an asteroid strike and a volcanic eruption. And that would be such spectacularly bad luck that it would not only confirm the existence of deity, but of an extremely pissed off deity.
So it seems much more likely to some experts that instead of a rock from outer space, that the call was coming from inside the house, so to speak--a hunk of our own planet came crashing down thousands of miles away. It would seriously be like if you were just minding your own business tomorrow and suddenly Tokyo fell on your head.