Why Geysers Go Boom

Yellowstone National Park has more geysers than anywhere else on Earth. That’s because the park sits on top of a “supervolcano,” where heat from deep inside the planet is especially close to the surface.

That underground heat turns water trapped in rock cracks into steam. When the pressure builds high enough the water blasts out as a geyser.

Yellowstone is home to over 500 active geysers. The most famous of all is Old Faithful, named for its regular eruptions.

Old Faithful shoots boiling water over 100 feet into the air about every 90 minutes. That’s taller than a ten-story building.

Each blast can spray up to 8,400 gallons of water, enough to fill a backyard swimming pool.

And here’s something wild: while many geysers are unpredictable, Old Faithful’s eruptions are so consistent that rangers can forecast them down to the minute.

Why so reliable? Scientists think Old Faithful has a straight, narrow underground path with just the right amount of pressure. It’s basically nature’s perfectly tuned steam engine.

Try this at home: Boil water in a covered pot and listen carefully. Can you hear the hiss and pop of steam escaping? That’s a tiny version of what’s happening under Yellowstone, just without the ten-story splash.