Yellowstone National Park boasts dozens of geysers and broiling eruptions. But they're nothing compared to the massive volcano that bubbles beneath the park, and could unleash a world-altering blast. Check out these images of the megablast-in-waiting.
National Geographic explains:
Yellowstone is a volcano, and not just any volcano. The oldest, most famous national park in the United States sits squarely atop one of the biggest volcanoes on Earth . . . The last three super-eruptions have been in Yellowstone itself. The most recent, 640,000 years ago, was a thousand times the size of the Mount St. Helens eruption in 1980, which killed 57 people in Washington. But numbers do not capture the full scope of the mayhem. Scientists calculate that the pillar of ash from the Yellowstone explosion rose some 100,000 feet, leaving a layer of debris across the West all the way to the Gulf of Mexico. Pyroclastic flows-dense, lethal fogs of ash, rocks, and gas, superheated to 1,470 degrees Fahrenheit-rolled across the landscape in towering gray clouds. The clouds filled entire valleys with hundreds of feet of material so hot and heavy that it welded itself like asphalt across the once verdant landscape. And this wasn't even Yellowstone's most violent moment. An eruption 2.1 million years ago was more than twice as strong, leaving a hole in the ground the size of Rhode Island.
It's worth reading the rest of this article - it beautifully captures the pyrotechnic scientific mystery that is Yellowstone Park. Photographer Mark Thiessen captured the blowholes where Yellowstone lets off scalding, mineral-rich water.