Take a guess: what’s the longest mountain range in the world?

The Rockies? At 3,000 miles, they traverse the U.S., Canada, and Mexico. But they’re not even close.

How about the Andes? Nope. They stretch most of the length of South America, but that’s just 4,000 miles.

The longest range in the world is over 40,000 miles long. Yes, one and a half times the circumference of the globe itself! How could that be?

Well, this range zig-zags across Earth like the stitch lines on a baseball, but there’s only one place you can easily see it: in Iceland. Everywhere else, it’s underwater.

That’s right, this mountain range follows the tectonic plate boundaries between continents, under the ocean. This chain, called the mid-ocean ridge, is created as the plates spread apart, when molten mantle pushes up to fill in the opening space. At these points you can see the ocean floor forming. Provided, that is, you have a deep-sea submersible.

At times the top of the ridge is a mile underwater. But because the ocean around it might be more than 2 miles deep, that means these mountains are still a mile high!

If you didn’t already know about this, don’t feel too bad. It wasn’t until the 1950’s that scientists had the technology to notice the largest continuous geologic feature on Earth.